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Originally Posted by DanO
First off READ THIS http://www.torsen.com/fsae/fsaefaq.htm
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35. Are there other differentials, such as a Type 2 (T-2), available to FSAE teams?
At the present, the Type 1 University Special is the only differential and drawing that we can supply to FSAE teams. While this may change in the future, a team wishing to use a Type 2 must currently go to a junkyard or a car dealer’s parts counter. We cannot supply a drawing for any other differential other than the University Special.
If you choose to use a Type 2 then you will have to do all your own design work. Two good possible choices would be the Mazda Miata (1996 - current), or the Toyota RAV4/Lexus RX300 (rear only). Both of these applications are fairly compact (ring gear pitch diameter is less than 7 inches) and can be made quite light.
Advantages to using a Type 2 are: all machining work for the housing is single axis, simplifying housing construction, the gears require no timing to assemble, the unit can be put together quickly. If you are making your own housing, it can be made with no windows, simplifying sealing the unit from oil leakage. Also, Type 2 differentials can use almost any type of lubricating oil, including ATF. Another advantage of using a type 2 differential is lower cost in volume production. The Type 2 would cost $280 each for a run of 1000 units for either of the two mentioned above. Gear costs are $19 per side gear, and $9 per planet gear.
The drawback to the Type 2 is a lower torque bias ratio than the University Special. Adding clutch plates to the side gears can increase TBR. The TBR would then likely be higher than the University Special.
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Whats the reasoning to go with the T-2? ease of case design? it has a lower bias ratio than the T-1 and you cant get the prints for the T-2 (yet)
(I take it you have the FSAE special torsen unit..?)
For The FSAE cars the t-1 type has an excellent bias ratio in a lightweight package. If you create a custom housing you will have excellent strenght and will allow a reduciton in rotational inertia. If i were you, putting time and effort into redesign of the casing of the T-1 is probably the best idea.
If you are going to tackle "scaling" the T-2 to a fsae car size all i can say is ... good luck. You are taking on a very large project, gear profiles, heat treatments, material specs, etc... And in the end.. still have a lower bias ratio.
T-1
T-2
http://www.torsen.com/products/T-2.htm
T-2R
BTW... torsens site has lots of info. ]. |
I've actually already found every one of those images and the FSAE torsen page. I see your point to go with building a housing for the T-1. However that has already been done and wouldn't get as many design points as the T-2 would. I also don't want to mess with timing and working on multiple axis. Looking at the T-2 design over the year, it just looks so much more simple than the T-1 does. I think the hardest thing would be getting the element and side gears. I might be able to use the side gears from the T-2 university spec that we have. Then I need to somehow achieve the equvex element gears. I wonder if I could buy some helical gears pre-heat treated. Then I could machine the grooves on both ends and heat treat them myself. The housing would just be a whole bunch of tolerancing to match the gears using the CNC. I'm hoping a simple heat treat would work for that. Torsen uses a ferritic nitro carburizing heat treatment. I already have the T-1 good to go with a pretty lightweight housing around the university special (I already even have one of the endplates machined); so if my attept at the T-2 fails, there are no worries.
You say I can't get prints for the T-2 YET? Does that mean that there is a time coming up that we might be able to? I got a print of one of the side gears. That was from a guy that had to machine that groove for the circlip.
If I could just get some good pictures of one,... like if someone was kind hearted enough to take one apart and take pictures of everything essential to the diff's operation,... then I think I'd be much much closer to getting the gear ratios right and getting the counterbores done to spec. I am also trying to buy one if I could get one for less that $100,... but I don't see that happening.
Alright. What are your thoughts? Am I off my rocker?