Terminology -
FD - Final Drive/diff ratio
LSD - Limited Slip Differential
Drop gears - transfer gears (primary, idler, and input gears)
There’s a good selection of straight-cut final FDs available. Examine the FD table, and using information from 'Gearbox - Final dives, standard' and 'Gearbox - Formulae for car speed, etc.' you can assess which would best suit your usage. Bear in mind that they’re noisy, make sure you select one that’ll fit your diff unit, and also consider that using drop gears will allow fine-tuning of the ratio where necessary. See 'Gearbox - Up-rating drop gears' for more info.
STRAIGHT CUT FINAL DRIVE RATIOS AVAILABLE.
FITMENT AVAILABLE
NUMBER OF
TEETH ON GEARS FITMENT AVAILABLECROWN WHEEL PINION RATIO (LSD is specific fitment)52 15 3.44 Std and twin pin, NOT LSD64 17 3.76 Std and twin pin, NOT LSD55 14 3.9 Std and twin pin, NOT LSD53 13 4.08 Std, twin pin, and LSD55 13 4.23 Std, twin pin, and LSD56 13 4.31 Std, twin pin, and LSD64 14 4.57* Std and twin pin, NOT LSD56 12 4.67 Std, twin pin, and LSD
NOTE; All above are actually ‘semi-helical’ with the exception of ‘*’.
The standard diff unit’s componentry falls well short in the performance stakes. As an absolute minimum you should fit an up-rated diff-pin - whether this is because your racing regs don’t allow alternatives, or merely for the road - along with new planet-wheels and thrust washers. If at all possible, use the later diff-cage that has cutouts next to the planet-wheel seats that take the later 'locating tab'-type thrust washers. This massively reduces diff wear of all types by stopping the thrust washers spinning. In the old-style diff these used to wear away very quickly, further exacerbating the planet-wheel/diff-pin wear problems and substantial irrevocable damage to the diff-cage. It is entirely possible to modify an early-type diff-cage to use the later thrust washers, but really only practical if there's a later one to hand to take dimensions from, and the diff-cage isn't already completely goosed. The wear is obvious to the eye - the planet-wheel seat should be smooth and not at all recessed.
Unfortunately this doesn’t guarantee complete reliability - even in a road car. The planet-wheels have a seemingly very broad manufacturing tolerance not really suitable for spirited driving, irrespective of power output. To counter this problem, Mini Spares/Mania also supply a special 'bushed' planet-wheel/diff-pin kit that massively reduces these tolerance/wear problems by the fitment of bronze bushes into modified planet-wheels. The bushes are precision reamed to give a proper fit on the diff-pin, greatly reducing twisting of the planet-wheels in use. The bushes also improve lubricity/reduced friction. The kit includes the competition diff-pin and new thrust washers.
Twin cross-pin diffs are the only real solution to long-term reliability for an 'open' diff. As the title infers, the unit has two diff-pins. Consequently it also has four planet-wheels. These two factors combined with proper, exact machining during manufacture make them practically indestructible - assuming tightly controlled tolerances, material spec, and heat treatments are adhered to as is the case for the superlative 'Trannex' unit. An absolute must for any Mini with anything like a whiff of increased power output, or/and where spirited driving is envisaged. Not particularly cheap, but a sight cheaper than an exploded diff and the consequent damage it’ll inflict!!
The ultimate is an ‘LSD’. Its title says it all. It limits the amount of slip allowed before it engages, providing positive drive to enable progress! They are generally referred to by the mis-informed as ‘Salisbury’ diffs, purely because this was the name of the first and only one available for the Mini for some considerable time. There are others - Trannex, Jack Knight, Quaife, and even AP Racing. For further expansive information on how these work, and who's does what, see articles pre-fixed 'Gearbox - Limited Slip Diffs…'
Ancillary components
It's every-bit as important to up-rate the collection of components that combine with the main gears to make up a whole and reliable gearbox. Mini Spares have poured substantial resources in to researching what needs doing and developing suitable components to make you life easier, and your Mini happier.
Genuine Rover balk rings are quite satisfactory for road use, and limited weekend, short distance racing. Circuit racing soon eats them up. Main problem is the material and manufacturing spec. They’re made by a process called ‘sintering’ that essentially means metal powder is pressed and bonded then baked in extreme temperature. An unfortunate by-product is brittleness. Wear rate is OK, but they break when used in anger by those less-than-sympathetic to the cars mechanicals. When used in sports other than the like of sprints/hill-climbs, it’s necessary to replace these every couple of events - approximately 100 racing miles - dependent on mechanically sympathetic level of user! To wit there are special manganese-bronze replacements. These need replacing at least once a year as they still wear, BUT are far less prone to breakage - thus preserving gears/dog-teeth/selector forks for longer periods.
Standard or cheap replacement layshafts are simply not up to the punishment of protracted high rpm use. The extremely hard chromed finish of the needle roller bearings used soon eats into the cheap/low-spec/heat-treated/poorly surface-ground materials used. Again, good, high quality versions are available from Mini Spares/Mania at sensible prices for all gearbox types. Essentially they are manufactured using higher-grade materials, far closer tolerances, more exacting heat-treatments, and finer ground finish.
For those struggling to fit LSD units or Hardy-Spicer-type couplings to rod-change gearboxes, help is at hand! The problems are two-fold. The diff output shafts are larger in outside diameter than pot-joints, and there’s the selector detent plunger/spring to cater for. Specifically manufactured side plates are available from Mini Spares/Mania to sort both problems in one go. They are basically the original S side plate cast with the necessary detent lug on. Consequently this means the original S side plates are also available.
And last but not least - whatever you use your Mini for, ALWAYS fit a centre-oil pick-up pipe to maintain oil supply when cornering hard!
GEARBOX - Up-rating drop gears
Terminology Drop Gears - Transfer gears (primary, idler and input gears) Large-bore - Refers to anything based on a 1275-type unit Small-bore - Refers to anything based on 850/998/1098 units The standard drop gears are fine for practically all road use - almost irrespective of power output. Despite what many folk believe - they are more than strong enough, and will perform perfectly well if correctly set up. That means getting the idler and primary gear end floats right, and using new bearings for the idler gear at each re-build. Simply following the methods outlined in the relevant workshop manuals will achieve these simple goals. There are two problems with standard drop gears - the main one is the helical cut of the teeth, the other a very limited selection of ratios. The helical-cut teeth are essentially power absorbing - both from increased metal-to-metal contact through having a greater tooth engagement area, and from side loads applied by the helical-cut. The limitation in ratios is mainly a one-to-one ratio. The only exceptions being the later 'economy' primary gear used on a very limited number of A+ 1275 units, and an 'economy input gear' sold by Jack Knight in the eighties. The former had 30 teeth instead of the 'standard' 29, the latter a fudged tooth profile to fit with the idler gear. To solve both problems, straight-cut versions are available. It has to be said here - contrary to popular knowledge, the straight-cut gears are no stronger than the helical standard versions, all things being equal (i.e. correctly fitted). Straight-cut drop gears come in a variety of ratios from a couple of manufacturers/suppliers. As they supply drive from crank to gearbox, they can be used to fine-tune the actual FD. The accompanying table gives the gory details. It's these that are largely responsible for the whining howl emitted by race Minis. Music to some folks ears and desired by many in street used/tuned variants. Obvious from the table is the fact that the 'Trannex' range has a very broad option for ratios as they revolve around a 'common to all' idler gear. Their manufacture is far superior to any other, with proper gear-ground teeth, minimum back-lash and rigorously maintained manufacturing tolerances. No surprise then that this is the type supplied by Mini Spares/Mania. STRAIGHT CUT DROP GEAR RATIO AVAILABILITY CHART. NUMBER OF TEETH ON GEARTYPE PRIMARY IDLER INPUT RATIO COMMENTSTRANNEX - 22 30 25 1.136-1 24 30 24 1.0-1 23 30 23 1.0-1 Extra strong input gear 24 30 25 1.0416-1 23 30 24 1.0434-1 22 30 23 1.045-1 Extra strong input gear 23 30 25 1.0869-1 22 30 24 1.09-1 24 30 23 0.958-1 NOTE; All Trannex ratios use same idler gear, so are totally interchangeable with each other. Not interchangeable with other manufacturers. Superior over-all quality makes these Number One.TYPE PRIMARY IDLER INPUT RATIO COMMENTSST TRANSMISSIONS & JACK KNIGHT - 24 31 24 1.0-1 23 31 24 1.043-1 Same idler/input as above 23 30 25 1.087-1 Seperate set from above 2 NOTE: Realistically not interchangeable between manufacturers due to tooth finish, so not recommended. ST transmission gears are generally a better product than the Jack Knight ones in terms of finish, fit, and longevity. Drop gears can be used to fine tune final drive. To assess actual FD, just multiply FD by the drop gear ratio. So a 3.44FD using a 1.0434 drop gear set would give - 3.44 x 1.0434 = 3.59 FD. A glance at the FD table will show this can be used to achieve ratios not available off the shelf. Primary gear bush failures. Although not of immediate interest to many road-runners, mainly accorded to the racing scene, it seems to be a perplexing problem to a very large number of folk around the world. So I'm having a pop at trying to solve the problem wholesale here. Distilling the myriad of the symptoms go like this descriptions down from the various languages it was put to me in (some were highly entertaining where more than a smattering of "sign language" was incorporated) the end result was always the same. The bushes at one end or other, and sometimes both, had failed in their duties. Incidentally, some of the confusion when trying to sort the problem descriptions was down to miss-understandings about which end of the primary gear is which. To put the record straight, the end nearest the engine is the FRONT end. Consequently the end nearest the flywheel is then the REAR end. The two biggest outstanding symptoms were severe oil leaks onto the flywheel/clutch assembly, and difficulty/impossibility in selecting gears. Strangely, these problems were still suffered immediately after refurbing the offending article, using "modifications" suggested by some of the many Mini "specialists" out there who all but guaranteed it'd cure the problems! Some bought new gears from other "specialists" who make their product "special" by using "specific machining detailing" to "cure the problem". Unsurprisingly these didn't work either. So how's this happening, and what's the solution? Front bush damage is caused by it becoming loose, spinning between the gear and crank, and generating an enormous amount of heat. This ruins the bush, destroying all clearances, and allows excessive amounts of oil to pass, both through the now much larger clearance between crank, bush and gear and past the primary gear seal. The latter happens because the primary gear wobbles about excessively so the sealing lip on the seal can't do its job. Slightly less severely super-heated bushes cause them to move outwards, jamming the primary gear between the retaining clips and the thrust washer and crank shoulder. This is why gear selection becomes difficult/impossible. The primary gear won't disengage drive from the engine, and is the main reason why the rear bush gets it's thrust lip broken off. Even if the loose front bush isn't immediately apparent. This lip does break off on it's own though, but for the same reason all the other problems occur. The "miracle cures" to this have been legion over the years. Despite much nose-tapping and eye-winking, almost all solutions revolve around two themes - running a much bigger front bush to crank clearance and/or welding it to the primary gear. As many can attest to, even this doesn't work. That's because the cause isn't being addressed. And that's EXCESSIVE HEAT. It's generated by the slipping clutch, be that when gear changes are made, getting off the line, or badly set-up clutch. Magnified by the use of cerametalic plates. The slipping causes friction, generating a huge amount of heat. This spreads through the plate and into the primary gear. When the heat level becomes excessive, the bushes pinch on the crank, are grabbed and spun. This is magnified by using desperately-lightened pressure-plates in conjunction with the cerametalic plate where heat generated by the clutch isn't efficiently/effectively dissipated. The heat simply bleeds way into the primary gear. The cure? Initially and mainly - reduce the heat level. Simply achieved by either boring holes in the clutch cover ("wok"), by welding on a suitably sized and positioned duct. (whichever, always cover with meshing to deter foreign objects from joining the fray), and use a sensibly dimensioned pressure-plate. This is something I am currently looking in to, so keep your eyes open for the results!
Bevel Gear Cutting Machine
The Phoenix II 600HC CNC Bevel Gear Cutting Machine features a monolithic column design that optimizes dry machining, significantly reduces floor space requirements and improves cycle times. While the 600HC can accommodate wet cutting processes, it is particularly well-suited for dry machining, with the cutter spindle and work spindle mounted directly to the column, and the cutter spindle pivots to create the root angle. The machine can accommodate all styles and types of Gleason and non-Gleason cutters and cutter systems for face mill and face hob cutting of bevel and hypoid gears.
Find the root cause of gear failure
Successful gear analysis is integral in preventing gear failure. Use the same rigorous process a gear failure analyst does.
PlantServices.com
By Robert Errichello
Successful gear failure analysis requires proper investigation, a strong team leader and a qualified gear failure analyst. These components are what it takes to determine the root cause of gear failure and maximize your chances for preventing failure recurrence.
Failure analysis is important
A properly managed failure investigation can provide valuable feedback about how a component performs. It might uncover shortcomings or weakness in design, manufacture or quality control. It can provide information for improvements that prevent future failure. In some cases, the failure investigation can assess liability and determine whether the failure was a unique event or a symptom of a wider problem. Rigorous root cause determination might lead to machinery improvements that yield:
* Greater safety
* Improved reliability
* Higher performance
* Greater efficiency
* Easier maintenance
* Reduced life-cycle costs
* Reduced impact on environment
The team leader
The most effective and efficient gear failure investigation is headed by a team leader who is high enough in your corporate hierarchy to be able to establish four items at the outset:
* The investigation’s priority
* Available resources
* Constraints imposed
* The investigation’s goal
The leader must be a good communicator with the ability to integrate the team and select the best expert for each role in the investigation. The leader should have a broad background and must be skilled in failure analysis techniques such as fault tree analysis (FTA), failure mode assessment (FMA) and root cause analysis (RCA).
The team leader needs a clear understanding of the investigation’s scope to organize it effectively. Time and money are always constrained. Therefore, the scope of the investigation is controlled by what you want to know and how much you’re willing to spend.
After considering all interests, the team leader should define a clearly stated goal before launching an investigation. This involves a detailed, well-documented investigation plan that makes clear to all involved what information is expected from each step of the investigation. The documentation should address:
* What is to be done
* Why is it to be done
* The findings expected to be determined
The specific investigative plan can vary depending on when and where the investigation is made, the nature of the failure and time constraints. In any case, the team leader needs to ensure that everyone involved understands the priorities, the analyst has the necessary resources, the investigation stays within imposed constraints and that the investigation will achieve its goal. This is a collaborative effort.
Additional team staffing should include a gear failure analyst who answers directly to the team leader, and metallurgists and tribologists who collaborate with the analyst and report to the team leader.
In some cases, a gear failure analyst with the necessary skills can be the team leader. Otherwise, the analyst should be responsible for technical details of the analysis, but work under the team leader’s supervision. This arrangement frees the analyst to concentrate on technical detail and permits the team leader to manage resources and logistics necessary to implement the plan.
The gear failure analyst
Gear failure analysis, a subset of general failure analysis, is conducted by an investigator who specializes in it. The requisite qualifications for the analyst include experience in gear design, stress analysis, gear manufacturing plus an understanding of how gearbox components are supposed to function and how they can malfunction. Furthermore, the analyst should have a thorough knowledge of gear metallurgy and tribology, and understand the capabilities and limitations of the analytical procedures both disciplines use.
There’s no real alternative to including an analyst. If you don’t have a qualified gear failure analyst on your staff, either train someone or hire an outside consultant. A metallurgist is unlikely to be familiar with the gear’s function, modes of operation and service characteristics, and is unlikely to be acquainted with manufacturing procedures, accepted workmanship and appropriate materials for a specific gear application.
Costs depend on gearbox complexity, nature of the failure, available resources for the investigation and risks associated with recurrence. The costs details might not be readily apparent. Therefore, cost estimates might need to be revised as the investigation progresses and the team leader needs to assess whether the budget is adequate to achieve the investigation’s goal.
The usual goal is to discover the root cause of a failure and determine the best corrective actions to prevent recurrence. In some cases, the goal might be to assess gearbox performance to improve the design. In other cases, the goal might be to assign responsibility for a failure.
Often there’s pressure to repair or replace failed components quickly and return the gear system to service. Because gear failures provide valuable data that can help prevent future failures, however, you should follow a systematic inspection procedure before repair or replacement begins. This entails a complete disassembly and thorough inspection of gearbox components.
Getting organized
As the investigation proceeds, it might become apparent that other resources are needed to corroborate evidence, such as metallurgical tests or tribological analyses. It’s often the case that investigation resources and budget must be reviewed and revised continually. Unless time and budget are adequate, it might be best not to investigate at all. The gear failure analyst should have access to:
* Design data
* Technical data
* Analysis reports
* Test reports
* Maintenance records
* Operational logs
The analyst should interview witnesses to the failure, operators, maintenance personnel, system designers and other people involved in gearbox design, operation and maintenance. The team leader should identify those responsible for operating the gearbox to provide information and resources the analyst needs.
Gear failures often attract onlookers or other curious parties. However, it’s imperative to preserve evidence and it’s in the best interest of the investigation to restrict access to the failed gearbox. If possible, the team leader should arrange to quarantine the gearbox and schedule an inspection as soon after the gear failure as possible. Failure conditions can determine when and how to conduct an analysis. It’s best to shutdown a failing gearbox as soon as possible to limit damage. To preserve evidence, carefully plan the failure investigation to include shutdown, in-situ inspections, gearbox removal, transport, storage and disassembly.
Prepare for inspection
Before visiting the failure site, the team should explain to the site contact person what is needed for the gearbox inspection, including personnel, equipment and working conditions. Ideally, the analyst should visit the site as soon as possible after failure. If an early inspection isn’t possible, someone at the site must take measures to preserve the evidence.
The analyst needs as much background information as possible, including manufacturer’s specifications, service history, load data and lubricant analyses. The analyst might send the site’s contact person a questionnaire to help expedite information gathering (Download Figure 1 using the "Download Now" button at the bottom of the page).
Before starting the inspection, the analyst should review background information and gearbox service history before interviewing those involved in the design, installation, startup, operation, maintenance and failure of the gearbox. Plant personnel should reveal all they know about the gearbox, even if some facts seem unimportant.
In some situations, the high cost of shutdown will limit the time available for inspection, in which case careful planning is required. It may require dividing tasks between two or more analysts to reduce downtime.
Keep it running?
If the gears are damaged but still functional, you may decide to continue operation and monitor damage progression. In this case, monitor the gear system under the analyst’s supervision. The analyst should ensure there are no risks to human life. For critical applications, the analyst should examine the gears with magnetic particle inspection to ensure there aren’t any cracks that prevent safe continued operation.
Other routine analysis actions the analyst should perform are a visual inspection and measurement of temperature, sound and vibration. The analyst should collect samples of lubricant for analysis and examine the oil filter for wear debris and contaminants, and inspect magnetic plugs for wear debris.
Then, it’s time to drain, flush and refill the reservoir.
Gear tooth contact patterns
The next steps to follow are important. Clean the inspection port cover and the surrounding area. Remove the cover, being careful not to contaminate the gearbox interior. Observe the condition of gears, shafts and bearings.
If there’s evidence of gear misalignment such as macropitting concentrated at ends of teeth, but no broken teeth or other failures that would prohibit rotating the gears, record the gear tooth contact patterns. The way gear teeth touch indicates how they’re aligned. Tooth contact patterns may be recorded under loaded or unloaded conditions (Figure 2). No-load patterns aren’t as reliable as loaded patterns for detecting misalignment because the marking compound is relatively thick and no-load tests don’t include misalignment caused by load, speed or temperature. Therefore, follow any no-load tests with loaded tests.
For no-load tests, paint the teeth of one gear with a soft marking compound and roll the teeth through the mesh so compound transfers to the unpainted gear. Turn the pinion by hand while applying a light load to the gear shaft by hand or brake. Use clear tape to lift the patterns from the gear and mount the tape on white paper to form a permanent record (Figure 3). The compound PT-650 Tooth Marking Grease available from Products/Techniques, Inc. (909) 877-3951, works best. Scotch No. 845 Book Tape (2-in. width) works well for lifting contact patterns.
For loaded tests, thoroughly clean the teeth with a solvent. Brush paint several teeth on one or both gears with a thin coat of machinist’s layout fluid (Dykem). Run the gears under load for sufficient time to wear off the lacquer and establish the contact pattern. Photograph patterns for a permanent record.
Record loaded contact patterns under several loads, for example, 25%, 50%, 75%, and 100%. Inspect patterns after running about one hour at each load to monitor how patterns change with load. Ideally, the patterns shouldn’t vary with load. Optimum contact patterns cover nearly 100% of the active face of gear teeth under full load, except at extremes along tooth tips, roots and ends, where contact is lighter as evidenced by traces of lacquer.
PlantServices.com
By Robert Errichello
Successful gear failure analysis requires proper investigation, a strong team leader and a qualified gear failure analyst. These components are what it takes to determine the root cause of gear failure and maximize your chances for preventing failure recurrence.
Failure analysis is important
A properly managed failure investigation can provide valuable feedback about how a component performs. It might uncover shortcomings or weakness in design, manufacture or quality control. It can provide information for improvements that prevent future failure. In some cases, the failure investigation can assess liability and determine whether the failure was a unique event or a symptom of a wider problem. Rigorous root cause determination might lead to machinery improvements that yield:
* Greater safety
* Improved reliability
* Higher performance
* Greater efficiency
* Easier maintenance
* Reduced life-cycle costs
* Reduced impact on environment
The team leader
The most effective and efficient gear failure investigation is headed by a team leader who is high enough in your corporate hierarchy to be able to establish four items at the outset:
* The investigation’s priority
* Available resources
* Constraints imposed
* The investigation’s goal
The leader must be a good communicator with the ability to integrate the team and select the best expert for each role in the investigation. The leader should have a broad background and must be skilled in failure analysis techniques such as fault tree analysis (FTA), failure mode assessment (FMA) and root cause analysis (RCA).
The team leader needs a clear understanding of the investigation’s scope to organize it effectively. Time and money are always constrained. Therefore, the scope of the investigation is controlled by what you want to know and how much you’re willing to spend.
After considering all interests, the team leader should define a clearly stated goal before launching an investigation. This involves a detailed, well-documented investigation plan that makes clear to all involved what information is expected from each step of the investigation. The documentation should address:
* What is to be done
* Why is it to be done
* The findings expected to be determined
The specific investigative plan can vary depending on when and where the investigation is made, the nature of the failure and time constraints. In any case, the team leader needs to ensure that everyone involved understands the priorities, the analyst has the necessary resources, the investigation stays within imposed constraints and that the investigation will achieve its goal. This is a collaborative effort.
Additional team staffing should include a gear failure analyst who answers directly to the team leader, and metallurgists and tribologists who collaborate with the analyst and report to the team leader.
In some cases, a gear failure analyst with the necessary skills can be the team leader. Otherwise, the analyst should be responsible for technical details of the analysis, but work under the team leader’s supervision. This arrangement frees the analyst to concentrate on technical detail and permits the team leader to manage resources and logistics necessary to implement the plan.
The gear failure analyst
Gear failure analysis, a subset of general failure analysis, is conducted by an investigator who specializes in it. The requisite qualifications for the analyst include experience in gear design, stress analysis, gear manufacturing plus an understanding of how gearbox components are supposed to function and how they can malfunction. Furthermore, the analyst should have a thorough knowledge of gear metallurgy and tribology, and understand the capabilities and limitations of the analytical procedures both disciplines use.
There’s no real alternative to including an analyst. If you don’t have a qualified gear failure analyst on your staff, either train someone or hire an outside consultant. A metallurgist is unlikely to be familiar with the gear’s function, modes of operation and service characteristics, and is unlikely to be acquainted with manufacturing procedures, accepted workmanship and appropriate materials for a specific gear application.
Costs depend on gearbox complexity, nature of the failure, available resources for the investigation and risks associated with recurrence. The costs details might not be readily apparent. Therefore, cost estimates might need to be revised as the investigation progresses and the team leader needs to assess whether the budget is adequate to achieve the investigation’s goal.
The usual goal is to discover the root cause of a failure and determine the best corrective actions to prevent recurrence. In some cases, the goal might be to assess gearbox performance to improve the design. In other cases, the goal might be to assign responsibility for a failure.
Often there’s pressure to repair or replace failed components quickly and return the gear system to service. Because gear failures provide valuable data that can help prevent future failures, however, you should follow a systematic inspection procedure before repair or replacement begins. This entails a complete disassembly and thorough inspection of gearbox components.
Getting organized
As the investigation proceeds, it might become apparent that other resources are needed to corroborate evidence, such as metallurgical tests or tribological analyses. It’s often the case that investigation resources and budget must be reviewed and revised continually. Unless time and budget are adequate, it might be best not to investigate at all. The gear failure analyst should have access to:
* Design data
* Technical data
* Analysis reports
* Test reports
* Maintenance records
* Operational logs
The analyst should interview witnesses to the failure, operators, maintenance personnel, system designers and other people involved in gearbox design, operation and maintenance. The team leader should identify those responsible for operating the gearbox to provide information and resources the analyst needs.
Gear failures often attract onlookers or other curious parties. However, it’s imperative to preserve evidence and it’s in the best interest of the investigation to restrict access to the failed gearbox. If possible, the team leader should arrange to quarantine the gearbox and schedule an inspection as soon after the gear failure as possible. Failure conditions can determine when and how to conduct an analysis. It’s best to shutdown a failing gearbox as soon as possible to limit damage. To preserve evidence, carefully plan the failure investigation to include shutdown, in-situ inspections, gearbox removal, transport, storage and disassembly.
Prepare for inspection
Before visiting the failure site, the team should explain to the site contact person what is needed for the gearbox inspection, including personnel, equipment and working conditions. Ideally, the analyst should visit the site as soon as possible after failure. If an early inspection isn’t possible, someone at the site must take measures to preserve the evidence.
The analyst needs as much background information as possible, including manufacturer’s specifications, service history, load data and lubricant analyses. The analyst might send the site’s contact person a questionnaire to help expedite information gathering (Download Figure 1 using the "Download Now" button at the bottom of the page).
Before starting the inspection, the analyst should review background information and gearbox service history before interviewing those involved in the design, installation, startup, operation, maintenance and failure of the gearbox. Plant personnel should reveal all they know about the gearbox, even if some facts seem unimportant.
In some situations, the high cost of shutdown will limit the time available for inspection, in which case careful planning is required. It may require dividing tasks between two or more analysts to reduce downtime.
Keep it running?
If the gears are damaged but still functional, you may decide to continue operation and monitor damage progression. In this case, monitor the gear system under the analyst’s supervision. The analyst should ensure there are no risks to human life. For critical applications, the analyst should examine the gears with magnetic particle inspection to ensure there aren’t any cracks that prevent safe continued operation.
Other routine analysis actions the analyst should perform are a visual inspection and measurement of temperature, sound and vibration. The analyst should collect samples of lubricant for analysis and examine the oil filter for wear debris and contaminants, and inspect magnetic plugs for wear debris.
Then, it’s time to drain, flush and refill the reservoir.
Gear tooth contact patterns
The next steps to follow are important. Clean the inspection port cover and the surrounding area. Remove the cover, being careful not to contaminate the gearbox interior. Observe the condition of gears, shafts and bearings.
If there’s evidence of gear misalignment such as macropitting concentrated at ends of teeth, but no broken teeth or other failures that would prohibit rotating the gears, record the gear tooth contact patterns. The way gear teeth touch indicates how they’re aligned. Tooth contact patterns may be recorded under loaded or unloaded conditions (Figure 2). No-load patterns aren’t as reliable as loaded patterns for detecting misalignment because the marking compound is relatively thick and no-load tests don’t include misalignment caused by load, speed or temperature. Therefore, follow any no-load tests with loaded tests.
For no-load tests, paint the teeth of one gear with a soft marking compound and roll the teeth through the mesh so compound transfers to the unpainted gear. Turn the pinion by hand while applying a light load to the gear shaft by hand or brake. Use clear tape to lift the patterns from the gear and mount the tape on white paper to form a permanent record (Figure 3). The compound PT-650 Tooth Marking Grease available from Products/Techniques, Inc. (909) 877-3951, works best. Scotch No. 845 Book Tape (2-in. width) works well for lifting contact patterns.
For loaded tests, thoroughly clean the teeth with a solvent. Brush paint several teeth on one or both gears with a thin coat of machinist’s layout fluid (Dykem). Run the gears under load for sufficient time to wear off the lacquer and establish the contact pattern. Photograph patterns for a permanent record.
Record loaded contact patterns under several loads, for example, 25%, 50%, 75%, and 100%. Inspect patterns after running about one hour at each load to monitor how patterns change with load. Ideally, the patterns shouldn’t vary with load. Optimum contact patterns cover nearly 100% of the active face of gear teeth under full load, except at extremes along tooth tips, roots and ends, where contact is lighter as evidenced by traces of lacquer.
Automatic transmission
An automatic transmission is an automobile gearbox that can change gear ratios automatically as the car or truck moves, thus freeing the driver from having to shift gears manually. (Similar but larger devices are also used for railroad locomotives.)
Most cars sold in the United States since the 1950s have been equipped with an automatic transmission. This has, however, not been the case in Europe and much of the rest of the world. Automatic transmissions, particularly earlier ones, reduce fuel efficiency and power. Where fuel is expensive and, thus, engines generally smaller, these penalties are more burdensome. In recent years, automatic transmissions have significantly improved in their ability to support high fuel efficiency but manual transmissions are still generally more efficient. (This balance may finally shift with the introduction of practical continuously variable transmissions; see below.)
Most automatic transmissions have a set selection of possible gear ranges, often with a parking pawl feature that will lock the output shaft of the transmission.
However, some simple machines with limited speed ranges and/or fixed engine speeds only use a torque converter to provide a variable gearing of the engine to the wheels. Typical examples include forklift trucks and some modern lawn mowers.
Recently manufacturers have begun to make continuously variable transmissions commonly available (earlier models such as the Subaru Justy did not popularize CVT). These designs can change the ratios over a range rather than between set gear ratios. Even though prototypes for CVT have been around for decades, it is just now reaching commercial practicability.
Hydraulic automatic transmissions
The automatic transmission selector lever in a Ford Five Hundred car.
The automatic transmission selector lever in a Ford Five Hundred car.
The predominant form of automatic transmission is hydraulically operated, using a fluid coupling or torque converter and a set of planetary gearsets to provide a range of torque multiplication.
Parts and operation
A hydraulic automatic transmission consists of the following parts:
* Fluid coupling or torque converter: A hydraulic device connecting the engine and the transmission. It takes the place of a mechanical clutch, allowing the engine to remain running at rest without stalling. A torque converter is a fluid coupling that also provides a variable amount of torque multiplication at low engine speeds, increasing "breakaway" acceleration.
* Planetary gearset: A compound planetary set whose bands and clutches are actuated by hydraulic servos controlled by the valve body, providing two or more gear ratios.
* Valve body: hydraulic control center that receives pressurised fluid from a main pump operated by the fluid coupling/torque converter. The pressure coming from this pump is regulated and used to run a network of spring-loaded valves, check balls and servo pistons. The valves use the pump pressure and the pressure from a centrifugal governor on the output side (as well as hydraulic signals from the range selector valves and the throttle valve or modulator) to control which ratio is selected on the gearset; as the car and engine change speed, the difference between the pressures changes, causing different sets of valves to open and close. The hydraulic pressure controlled by these valves drives the various clutch and brake band actuators, thereby controlling the operation of the planetary gearset to select the optimum gear ratio for the current operating conditions. However, in many modern automatic transmissions, the valves are controlled by electro-mechanical servos which are controlled by the Engine Management System or a separate transmission controller. (See History and improvements below.)
The multitude of parts, along with the complex design of the valve body, originally made hydraulic automatic transmissions much more complicated (and expensive) to build and repair than manual transmissions. In most cars (except US family, luxury, sport-utility vehicle, and minivan models) they have usually been extra-cost options for this reason. Mass manufacturing and decades of improvement have reduced this cost gap.
History and improvements
Oldsmobile's 1940 models featured Hydra-Matic drive, the first mass-production fully automatic transmissions. Initially an Olds exclusive, Hydra-Matic had a fluid coupling (not a torque converter) and three planetary gearsets providing four speeds plus reverse. Hydra-Matic was subsequently adopted by Cadillac and Pontiac, and was sold to various other automakers, including Bentley, Hudson, Kaiser, Nash, and Rolls-Royce. From 1950 to 1954 Lincoln cars were also available with GM Hydra-Matic. Mercedes-Benz subsequently devised a four-speed fluid coupling transmission that was similar in principle to Hydra-Matic, but did not share the same design.
The first torque converter automatic, Buick's Dynaflow, was introduced for the 1948 model year. It was followed by Chevrolet's Powerglide and Packard's Ultramatic for the 1950 model year. Each of these transmissions had only two forward speeds, relying on the torque converter for additional gear reduction.
In the early 1950s Borg-Warner developed a series of three-speed torque converter automatics for Ford Motor Company, Studebaker, and several foreign and independent makes.
Chrysler was late in developing its own true automatic, introducing the two-speed torque converter PowerFlite in 1953 and the three-speed TorqueFlite in 1956.
By the late 1960s most of the fluid-coupling four-speeds and two-speed transmissions had disappeared in favor of three-speed units with torque converters. By the early 1980s these were being supplemented and eventually replaced by overdrive-equipped transmissions providing four or more forward speeds. Many transmissions also adopted the lock-up torque converter (a mechanical clutch locking the torque converter impeller and turbine together to eliminate slip at cruising speed) to improve fuel economy.
As the engine computers became more and more capable, even more of the valve body's functionality was offloaded to them. These transmissions, introduced in the late 1980s and early 1990s, remove almost all of the control logic from the valve body, and place it in into the engine computer. (Some manufacturers use a separate computer dedicated to the transmission but sharing information with the engine management computer.) In this case, solenoids turned on and off by the computer control shift patterns and gear ratios, rather than the spring-loaded valves in the valve body. This allows for more precise control of shift points, shift quality, lower shift times and (on some newer cars) semi-automatic control, where the driver tells the computer when to shift. The result is an impressive combination of efficiency and smoothness. Some computers even identify the driver's style and adapt to best suit it.
ZF Friedrichshafen AG and BMW were responsible for introducing the first five-speed automatic (the ZF 5HP18 in the 1992 BMW E34 5-Series) and the first six-speed (the ZF 6HP26 in the 2002 BMW E65 7-Series). Mercedes-Benz's 7G-TRONIC was the first seven-speed in 2003, with Toyota Motor Company introducing an 8-speed in 2007 on the Lexus LS.
Automatic Transmission Models
Some of the best known automatic transmission families include:
* General Motors — Powerglide, Turbo-Hydramatic 350 and 400, 4L60-E, 4L80-E
* Ford: Cruise-O-Matic, C4, C6, AOD/AODE, E4OD, ATX, AXOD/AX4S/AX4N
* Chrysler: TorqueFlite 727 and 904, A500, A518, 45RFE, 545RFE
* BorgWarner (later Aisin AW)
* ZF Friedrichshafen AG
* Allison Transmission
* Voith Turbo
* Aisin AW; Aisin AW is a Japanese automotive parts supplier, known for its automatic transmissions and navigation systems
* Honda
* Nissan/Jatco
Automatic transmission families are usually based on Ravigneaux, Lepelletier, or Simpson planetary gearsets. Each uses some arrangement of one or two central sun gears, and a ring gear, with differing arrangements of planet gears that surround the sun and mesh with the ring. An exception to this is the Hondamatic line from Honda, which uses sliding gears on parallel axes like a manual transmission without any planetary gearsets. Although the Honda is quite different from all other automatics, it is also quite different from an automated manual transmission.
Continuously variable transmissions
Main article: continuously variable transmission
A different type of automatic transmission is the continuously variable transmission or CVT, which can smoothly alter its gear ratio by varying the diameter of a pair of belt or chain-linked pulleys, wheels or cones. Some continuously variable transmissions use a hydrostatic drive consisting of a variable displacement pump and a hydraulic motor to transmit power without gears. CVT designs are usually as fuel efficient as manual transmissions in city driving, but early designs lose efficiency as engine speed increases.
A slightly different approach to CVT is the concept of toroidal CVT or IVT (from infinitely variable transmission). These concepts provide zero and reverse gear ratios.
Some current hybrid vehicles, notably those of Toyota, Lexus and Ford Motor Company, have an "electronically-controlled CVT" (E-CVT). In this system, the transmission has fixed gears, but the ratio of wheel-speed to engine-speed can be continuously varied by controlling the speed of the third input to a differential using an electric motor-generator.
Manually controlled automatic transmissions
Most automatic transmissions offer the driver a certain amount of manual control over the transmission's shifts (beyond the obvious selection of forward, reverse, or neutral). Those controls take several forms:
* Throttle kickdown: Most automatic transmissions include a switch on the throttle linkage that will force the transmission to downshift into the next lower ratio if the throttle is fully engaged. The switch generally only functions up to a certain road speed, so as to prevent a downshift that would overrev the engine. Some transmissions also had a part-throttle kickdown, obviating the need to "floorboard" the throttle to downshift.
* Low gear ranges: Many transmissions have switches or selector positions that allow the driver to limit the maximum ratio that the transmission may engage. On older transmissions, this was accomplished by a mechanical lockout in the transmission valve body preventing an upshift until the lockout was disengaged; on computer- controlled transmissions, the same effect is accomplished electronically. The transmission can still upshift and downshift automatically between the remaining ratios: for example, in the 3 range, a transmission could shift from first to second to third, but not into fourth or higher ratios. Some transmissions will still upshift automatically into the higher ratio if the engine reaches its maximum permissible speed in the selected range.
* Manual controls: Some transmissions have a mode in which the driver has full control of ratio changes (either by moving the selector or through the use of buttons or paddles), completely overriding the hydraulic controller. Such control is particularly useful in cornering, to avoid unwanted upshifts or downshifts that could compromise the vehicle's balance or traction. "Manumatic" shifters, first popularized by Porsche in the 1990s under the trade name Tiptronic, have become a popular option on sports cars and other performance vehicles. With the near-universal prevalence of electronically controlled transmissions, they are comparatively simple and inexpensive, requiring only software changes and the provision of the actual manual controls for the driver. The amount of true manual control provided is highly variable: some systems will override the driver's selections under certain conditions, generally in the interest of preventing engine damage.
Some automatic transmissions modified or designed specifically for drag racing may also incorporate a transmission brake, or "trans-brake," as part of a manual valve body. Activated by electrical solenoid control, a trans-brake simultaneously engages the first and reverse gears, locking the transmission and preventing the input shaft from turning. This allows the driver of the car to raise the engine rpm against the resistance of the torque converter, then launch the car by simply releasing the trans-brake switch.
Most cars sold in the United States since the 1950s have been equipped with an automatic transmission. This has, however, not been the case in Europe and much of the rest of the world. Automatic transmissions, particularly earlier ones, reduce fuel efficiency and power. Where fuel is expensive and, thus, engines generally smaller, these penalties are more burdensome. In recent years, automatic transmissions have significantly improved in their ability to support high fuel efficiency but manual transmissions are still generally more efficient. (This balance may finally shift with the introduction of practical continuously variable transmissions; see below.)
Most automatic transmissions have a set selection of possible gear ranges, often with a parking pawl feature that will lock the output shaft of the transmission.
However, some simple machines with limited speed ranges and/or fixed engine speeds only use a torque converter to provide a variable gearing of the engine to the wheels. Typical examples include forklift trucks and some modern lawn mowers.
Recently manufacturers have begun to make continuously variable transmissions commonly available (earlier models such as the Subaru Justy did not popularize CVT). These designs can change the ratios over a range rather than between set gear ratios. Even though prototypes for CVT have been around for decades, it is just now reaching commercial practicability.
Hydraulic automatic transmissions
The automatic transmission selector lever in a Ford Five Hundred car.
The automatic transmission selector lever in a Ford Five Hundred car.
The predominant form of automatic transmission is hydraulically operated, using a fluid coupling or torque converter and a set of planetary gearsets to provide a range of torque multiplication.
Parts and operation
A hydraulic automatic transmission consists of the following parts:
* Fluid coupling or torque converter: A hydraulic device connecting the engine and the transmission. It takes the place of a mechanical clutch, allowing the engine to remain running at rest without stalling. A torque converter is a fluid coupling that also provides a variable amount of torque multiplication at low engine speeds, increasing "breakaway" acceleration.
* Planetary gearset: A compound planetary set whose bands and clutches are actuated by hydraulic servos controlled by the valve body, providing two or more gear ratios.
* Valve body: hydraulic control center that receives pressurised fluid from a main pump operated by the fluid coupling/torque converter. The pressure coming from this pump is regulated and used to run a network of spring-loaded valves, check balls and servo pistons. The valves use the pump pressure and the pressure from a centrifugal governor on the output side (as well as hydraulic signals from the range selector valves and the throttle valve or modulator) to control which ratio is selected on the gearset; as the car and engine change speed, the difference between the pressures changes, causing different sets of valves to open and close. The hydraulic pressure controlled by these valves drives the various clutch and brake band actuators, thereby controlling the operation of the planetary gearset to select the optimum gear ratio for the current operating conditions. However, in many modern automatic transmissions, the valves are controlled by electro-mechanical servos which are controlled by the Engine Management System or a separate transmission controller. (See History and improvements below.)
The multitude of parts, along with the complex design of the valve body, originally made hydraulic automatic transmissions much more complicated (and expensive) to build and repair than manual transmissions. In most cars (except US family, luxury, sport-utility vehicle, and minivan models) they have usually been extra-cost options for this reason. Mass manufacturing and decades of improvement have reduced this cost gap.
History and improvements
Oldsmobile's 1940 models featured Hydra-Matic drive, the first mass-production fully automatic transmissions. Initially an Olds exclusive, Hydra-Matic had a fluid coupling (not a torque converter) and three planetary gearsets providing four speeds plus reverse. Hydra-Matic was subsequently adopted by Cadillac and Pontiac, and was sold to various other automakers, including Bentley, Hudson, Kaiser, Nash, and Rolls-Royce. From 1950 to 1954 Lincoln cars were also available with GM Hydra-Matic. Mercedes-Benz subsequently devised a four-speed fluid coupling transmission that was similar in principle to Hydra-Matic, but did not share the same design.
The first torque converter automatic, Buick's Dynaflow, was introduced for the 1948 model year. It was followed by Chevrolet's Powerglide and Packard's Ultramatic for the 1950 model year. Each of these transmissions had only two forward speeds, relying on the torque converter for additional gear reduction.
In the early 1950s Borg-Warner developed a series of three-speed torque converter automatics for Ford Motor Company, Studebaker, and several foreign and independent makes.
Chrysler was late in developing its own true automatic, introducing the two-speed torque converter PowerFlite in 1953 and the three-speed TorqueFlite in 1956.
By the late 1960s most of the fluid-coupling four-speeds and two-speed transmissions had disappeared in favor of three-speed units with torque converters. By the early 1980s these were being supplemented and eventually replaced by overdrive-equipped transmissions providing four or more forward speeds. Many transmissions also adopted the lock-up torque converter (a mechanical clutch locking the torque converter impeller and turbine together to eliminate slip at cruising speed) to improve fuel economy.
As the engine computers became more and more capable, even more of the valve body's functionality was offloaded to them. These transmissions, introduced in the late 1980s and early 1990s, remove almost all of the control logic from the valve body, and place it in into the engine computer. (Some manufacturers use a separate computer dedicated to the transmission but sharing information with the engine management computer.) In this case, solenoids turned on and off by the computer control shift patterns and gear ratios, rather than the spring-loaded valves in the valve body. This allows for more precise control of shift points, shift quality, lower shift times and (on some newer cars) semi-automatic control, where the driver tells the computer when to shift. The result is an impressive combination of efficiency and smoothness. Some computers even identify the driver's style and adapt to best suit it.
ZF Friedrichshafen AG and BMW were responsible for introducing the first five-speed automatic (the ZF 5HP18 in the 1992 BMW E34 5-Series) and the first six-speed (the ZF 6HP26 in the 2002 BMW E65 7-Series). Mercedes-Benz's 7G-TRONIC was the first seven-speed in 2003, with Toyota Motor Company introducing an 8-speed in 2007 on the Lexus LS.
Automatic Transmission Models
Some of the best known automatic transmission families include:
* General Motors — Powerglide, Turbo-Hydramatic 350 and 400, 4L60-E, 4L80-E
* Ford: Cruise-O-Matic, C4, C6, AOD/AODE, E4OD, ATX, AXOD/AX4S/AX4N
* Chrysler: TorqueFlite 727 and 904, A500, A518, 45RFE, 545RFE
* BorgWarner (later Aisin AW)
* ZF Friedrichshafen AG
* Allison Transmission
* Voith Turbo
* Aisin AW; Aisin AW is a Japanese automotive parts supplier, known for its automatic transmissions and navigation systems
* Honda
* Nissan/Jatco
Automatic transmission families are usually based on Ravigneaux, Lepelletier, or Simpson planetary gearsets. Each uses some arrangement of one or two central sun gears, and a ring gear, with differing arrangements of planet gears that surround the sun and mesh with the ring. An exception to this is the Hondamatic line from Honda, which uses sliding gears on parallel axes like a manual transmission without any planetary gearsets. Although the Honda is quite different from all other automatics, it is also quite different from an automated manual transmission.
Continuously variable transmissions
Main article: continuously variable transmission
A different type of automatic transmission is the continuously variable transmission or CVT, which can smoothly alter its gear ratio by varying the diameter of a pair of belt or chain-linked pulleys, wheels or cones. Some continuously variable transmissions use a hydrostatic drive consisting of a variable displacement pump and a hydraulic motor to transmit power without gears. CVT designs are usually as fuel efficient as manual transmissions in city driving, but early designs lose efficiency as engine speed increases.
A slightly different approach to CVT is the concept of toroidal CVT or IVT (from infinitely variable transmission). These concepts provide zero and reverse gear ratios.
Some current hybrid vehicles, notably those of Toyota, Lexus and Ford Motor Company, have an "electronically-controlled CVT" (E-CVT). In this system, the transmission has fixed gears, but the ratio of wheel-speed to engine-speed can be continuously varied by controlling the speed of the third input to a differential using an electric motor-generator.
Manually controlled automatic transmissions
Most automatic transmissions offer the driver a certain amount of manual control over the transmission's shifts (beyond the obvious selection of forward, reverse, or neutral). Those controls take several forms:
* Throttle kickdown: Most automatic transmissions include a switch on the throttle linkage that will force the transmission to downshift into the next lower ratio if the throttle is fully engaged. The switch generally only functions up to a certain road speed, so as to prevent a downshift that would overrev the engine. Some transmissions also had a part-throttle kickdown, obviating the need to "floorboard" the throttle to downshift.
* Low gear ranges: Many transmissions have switches or selector positions that allow the driver to limit the maximum ratio that the transmission may engage. On older transmissions, this was accomplished by a mechanical lockout in the transmission valve body preventing an upshift until the lockout was disengaged; on computer- controlled transmissions, the same effect is accomplished electronically. The transmission can still upshift and downshift automatically between the remaining ratios: for example, in the 3 range, a transmission could shift from first to second to third, but not into fourth or higher ratios. Some transmissions will still upshift automatically into the higher ratio if the engine reaches its maximum permissible speed in the selected range.
* Manual controls: Some transmissions have a mode in which the driver has full control of ratio changes (either by moving the selector or through the use of buttons or paddles), completely overriding the hydraulic controller. Such control is particularly useful in cornering, to avoid unwanted upshifts or downshifts that could compromise the vehicle's balance or traction. "Manumatic" shifters, first popularized by Porsche in the 1990s under the trade name Tiptronic, have become a popular option on sports cars and other performance vehicles. With the near-universal prevalence of electronically controlled transmissions, they are comparatively simple and inexpensive, requiring only software changes and the provision of the actual manual controls for the driver. The amount of true manual control provided is highly variable: some systems will override the driver's selections under certain conditions, generally in the interest of preventing engine damage.
Some automatic transmissions modified or designed specifically for drag racing may also incorporate a transmission brake, or "trans-brake," as part of a manual valve body. Activated by electrical solenoid control, a trans-brake simultaneously engages the first and reverse gears, locking the transmission and preventing the input shaft from turning. This allows the driver of the car to raise the engine rpm against the resistance of the torque converter, then launch the car by simply releasing the trans-brake switch.
Twin-clutch Gearbox
A Twin-clutch gearbox is a semi-automatic transmission with separate clutches for odd and even gears. Shifts can be accomplished without interrupting power by transferring torque between these two clutches. A dual clutch gearbox eliminates the torque converter, which is a major source of parasitic loss in a traditional automatic transmission. This type of gearbox was invented by Andolphe Kégresse just before the outbreak of World War II.
Essentially, the engine drives two clutch packs simultaneously. The outer clutch pack drives gears 1, 3, and 5 (and reverse). The inner clutch pack drives gears 2, 4, and 6. The synchronizers that select an odd gear can be moved while driving in an even gear and vice versa. Dual clutch transmissions that are currently on the market use wet multi-plate clutches, similar to the clutches used in traditional automatic transmissions. Versions that use dry clutches, like those usually associated with manual transmissions, are rumored to be in development by several manufacturers.
BorgWarner is currently the leading manufacturer of this type of transmission. They are most commonly sold under the name Direct-Shift Gearbox, as sold by Volkswagen Group. In August 2005 BorgWarner, who call their technology "DualTronic", signed further agreements with two other (unnamed) European automotive manufacturers to incorporate their gearbox.
Essentially, the engine drives two clutch packs simultaneously. The outer clutch pack drives gears 1, 3, and 5 (and reverse). The inner clutch pack drives gears 2, 4, and 6. The synchronizers that select an odd gear can be moved while driving in an even gear and vice versa. Dual clutch transmissions that are currently on the market use wet multi-plate clutches, similar to the clutches used in traditional automatic transmissions. Versions that use dry clutches, like those usually associated with manual transmissions, are rumored to be in development by several manufacturers.
BorgWarner is currently the leading manufacturer of this type of transmission. They are most commonly sold under the name Direct-Shift Gearbox, as sold by Volkswagen Group. In August 2005 BorgWarner, who call their technology "DualTronic", signed further agreements with two other (unnamed) European automotive manufacturers to incorporate their gearbox.
Right Angle Worm Gear Boxes
The AGNEE Worm Gear Boxes have Cast Iron Gear Case of streamlined design completely air tight, dust proof and capable of being installed in open without any cover. The Worm Shaft is made of Alloy Steel, duly hardened and tempered. The Worm Wheel is made of Chill Cast Phosphorous Bronze and teeth accurately Generated on Gear Hobbing Machines. They are supported on Extra Heavy Duty Taper Roller anti friction Bearings of ample margin of safety to allow adequate journals as well as thrust loads. Lubrication is effected by splash of oil from the sump. Thus, no special care is required except for occasional oil topping to the required level. Air cooling is effected by means of standard polypropylene or metal fans. Please read the Selection of Correct Worm gear box for choosing the correct one for your application. They are available in:
*
Vast range of Models suit every individual's requirement *
Some Models like C.D. 50, 60, 75, 85, 100 mm, Ratio 30:1 or 40:1 are usually available Ex-stock or on short notice *
Center Distances from 40 mm to 400 mm *
In Single or Double Stage Reductions *
Ratios from 5:1 to 4900:1 *
Also made as per customer's specifications, Drawing, requirements *
Overhauling of Old Gear Boxes also undertaken, Early delivery schedules *
Adaptable Worm Gear Boxes, range from CD 25mm to 85mm
Right angle gear boxes contain input shafts that are positioned perpendicular to the output shafts. Right angle gearboxes have up to 98% efficiency levels, and are common in printing presses and glass cutting equipment.
*
Vast range of Models suit every individual's requirement *
Some Models like C.D. 50, 60, 75, 85, 100 mm, Ratio 30:1 or 40:1 are usually available Ex-stock or on short notice *
Center Distances from 40 mm to 400 mm *
In Single or Double Stage Reductions *
Ratios from 5:1 to 4900:1 *
Also made as per customer's specifications, Drawing, requirements *
Overhauling of Old Gear Boxes also undertaken, Early delivery schedules *
Adaptable Worm Gear Boxes, range from CD 25mm to 85mm
Right angle gear boxes contain input shafts that are positioned perpendicular to the output shafts. Right angle gearboxes have up to 98% efficiency levels, and are common in printing presses and glass cutting equipment.
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