Drivetrain/ Shifter Questions

[drivetrainUW-Platt]

I am on the drivetrain team this year and will be the team leader next year. We will be having a custom 3 piece differential housing machined out of aluminum for our car this year, using the torsen innards. I was just curious what other teams have experimented with and what success they had. Also, as far as shifter systems, what differnt ideas are being used? What we will be running is a manual paddle shift with a cam design clutching device, all mounted behind the steering wheel. we would like to go electronic, but have heard that they are troublesome.

Mike Duwe
UW-Platteville Drivetrain 2004

[Attitude_Mikey]

Mike,

UQ Racing used a custom housing on torsen inards in our first two cars (2001 & 2002). To my knowledge it was used succesfully on the 2001 car, but failed at 2002 comp. In 2003 the team went to a spool. Works great.

The team leader in 2003 did a thesis on an elctromotive shifter, using feedback control. The device did work to his credit, however was swapped for a pnuematic system with button shift and a cable clutch, due to power draw issues -> dead batteries.

[DJHache]

As far as shifter goes, mechanical is by far the most reliable, light, and easy to use. Theyt can be troublesome though if the driver tries to force the engine to shift when it really doesn't want to.
Electric solenoid shifters are large, heavy, and unreliable. I don't think they keep the power on long enough to convince the engine to shift.
Air shifters may be a little bit complicated and you have to use tank (special rules) but they give more reliable shifts, the power stays on long enough to get the engine to shift.

[Lyn Labahn UW-Madison]

We have tried it all at one time another: Pneumatic, Push Pull cable, Mechanical with bellcranks, electronic, hydraulic clutch and cable clutch. Commercially availible shift solenoids do not seem to have enough force to shift the car at High RPM. We also blew up in endurance last year because the solenoid malfunctioned. This year we are running a solid rod linkage with no bell crank and a cable clutch. Clutch and shift feel are awesome, and it is easy to make.

[Charlie]

I don't like to say any ideas are unreliable or troublesome. I'd like to think its a problem with the design or component selection, rather than the idea. Surely its possible to design a reliable electric shifting system, in fact I'd wager that its already been done.

That said I think the main problem with the electric shifter is the charging system. There isn't much available, although perhaps a larger battery would still weigh less than a normal battery + a CO2 bottle. Having a car that slowly drains its battery is not ideal, but neither is one that has to refill its shifter bottle.

We are running a pneumatic shifting system with optional automatic upshift, and a 2nd generation aluminum diff housing with integrated brake hat.

Whatever you do just make sure your new shifting setup provides you with some advantage over a manual setup, otherwise whats the point. Unless you do things for design points only which I hate to see teams do but I know they do it...

[Matthew]

not sure about the diff.

but our shifting was a side mounted push pull cable, and clutch was a third pedal up front. Very intuitive for new drivers, plus plenty of leverage for shifting, IMO the throw for 1st to second was too long and there was a fiar about of slack in the shifter, but the goal was to keep shifting down to a minimum (top speed in 2nd appx 65 mph)

[flybywire]

Queen's U. has used torsen diff inards in custom housing many times. We dropped it last year though for a smaller, lighter diff.

As for clutch/shifting systems we have always used a mechanical system. Cable for clutch and either push-pull cable or solid linkage for the shift. I have been investingating alternatives though and would be interested in any more comments on electric systems.

Has anyone used DC gearmotors to actuate clutch and/or shift? They look heavy at the outset but they could eliminate arms or cams. Also, how do people who run electric, pneumatic, etc. clutch actuators deal with launch? Do you just run an on/off clutch control and dump the clutch at launch and hope for the best? Or do people run more complex systems capable of feathering the clutch?

[jack]

flybywire, what do you use instead of a torsen? how well does it work?

[flybywire]

Hey Jack,

I don't know what the Queen's team is using this year and I don't know the model numbers and details but last year we used a front diff off of a Honda 4WD ATV I believe. I think we purchased the half shafts as well and used the CVs, splines, etc. The diff is a design I am not familiar with which uses a series of floating geometric cogs which press against each other laterally as the wheels speeds mis-match. I presume it works somewhat like a torsen where friction transfers torque between the axles in mis-match. It did have a break-in period where it would bind and skip internally in tight cornering but this may have something to do with it being designed for less mis-match on the skinnier wheel base of an ATV. I didn't do the application engineering so... http://fsae.com/groupee_common/emoticons/icon_biggrin.gif (If someone recognizes this design from my cursory explination I'd like to know what it's called so I can look it up.)

Word of caution though, we were running a 400cc naturally asperated Suzuki single so I'm not sure what the power handling of the particular diff is but by the seat-of-the-pants-visual-structural-analysis method it seemed a better match for a Formula car than the large Uni-Specials. Actually, if it survives the power pulse from a 400cc single it probably will stand up to the power pulse from a 600cc 4 quite nicely.

All in all it seemed to work well; but I wasn't around for the summer race season and the team may have some further comments now that they have had some decent track experience with it. The Queen's U team website is: http://www.engsoc.queensu.ca/formulacar/

[All Wheeler]

Just wondering if anyone has ever bothered determining the inner profile of their trunnion joint.
Doug

[Pico2]

Last year we used a pneumatic system with an on-board air compressor to fill the air tank. This year we are using the same pneumatic components with the exception of using CO2 to replace the compressor. The shifting is performed by paddle shifters. So far, the system is running reliably, but as with any other component in a racecar, needs more testing. The clutch is a hand operated pull cable similar to a motorcycle.

[formula_geek]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by flybywire:
(If someone recognizes this design from my cursory explination I'd like to know what it's called so I can look it up.)
<HR></BLOCKQUOTE>

See this thread for more info:

http://fsae.com/eve/forums?a=tpc&s=763607348&f=125607348&m=4126049904&r=1706017014#1706017014

Travis Slagle
Kettering FSAE Alum

[drivetrainUW-Platt]

hey,
yeah, we found out the hard way that the shifter lever must be within the framerails. we figured we would put it on the outside to save a little room and allow for more driver comfort...tech didnt like it so we added a few bars around it to pass. as far as the diff i designed, still havent run it, didnt pass braking at comp, and have had time to fix our problem yet....arg i guess
Mike Duwe
UW-P Drivetrain Leader 2005

[RagingGrandpa]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by DJHache:
Electric solenoid shifters are large, heavy, and unreliable. <HR></BLOCKQUOTE>
amen to that!

[Chris Boyden]

It sounds like DJ used an off the shelf system...
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR> I don't think they keep the power on long enough to convince the engine to shift.
<HR></BLOCKQUOTE>

A custom system allows you to keep the power on as long as you want....long enough to smoke some coils and electronics! http://fsae.com/groupee_common/emoticons/icon_mad.gif

An ignition kill is a HUGE factor in getting the shift times down.

Look for Uni Western Aus. to come out with a super fast shifter using custom voice-coils for clutching and shifting.

The solenoids are very reliable...the electronics are the toughest part to nail down.
However, the whole system can be fast as hell once it is tuned.

As far as launching goes, clutch on the launch, then the upshifts are powershifts with ignition cut. Some teams use a pneumatic clutch and set the bleeddown to get the desired clutch "dump".
There are several ways to do it.