Clutch Actuation

[Ali]

Hi,

I'm builiding a first year car and want to implement electromechanical shifting. My problem is finding an actuator strong enough to move the clutch rod. We're using a GSXR 600 engine. I'm thinking motors (convert rotary to linear motion?) or linear actuators (pneumatic?).

Anyone done this before? If it's a big secret, a slight nudge in the right direction will be greatly appreciated.


Cheers,
Ali, Nat. Univ. of Singapore

[Ali]

Hi,

I'm builiding a first year car and want to implement electromechanical shifting. My problem is finding an actuator strong enough to move the clutch rod. We're using a GSXR 600 engine. I'm thinking motors (convert rotary to linear motion?) or linear actuators (pneumatic?).

Anyone done this before? If it's a big secret, a slight nudge in the right direction will be greatly appreciated.


Cheers,
Ali, Nat. Univ. of Singapore

[Denny Trimble]

Fact:
I've seen solenoids, electric motors, and pneumatic cylinders used.

Opinion:
As a first-year-team, you should really look at putting semi-auto shifting on the back burner. The reliability issues are huge, you'll notice only 30ish teams out of 140 registered completed endurance. There are just too many other systems on the car that need attention. And, fewer than 30% of the top teams used semi-auto shifting this year, if I recall correctly (which is unlikely).

Also, as a driver, I downshift smoothly into fast corners and abruptly into slow/tight corners, to help yaw the car. How would you integrate this behavior in your semi-auto downshift?

Hope this helps

University of Washington Formula SAE ('98, '99, '03)

[Charlie]

We have used a pnuematic cylinder for years for our shifter. But we've always used a manual clutch.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Denny Trimble:
Also, as a driver, I downshift smoothly into fast corners and abruptly into slow/tight corners, to help yaw the car. How would you integrate this behavior in your semi-auto downshift?
<HR></BLOCKQUOTE>

I use the pedals & steering wheel to drive the car, if I want more yaw then I trail brake. I don't think upsetting the car with a downshift is something you want to design for, though it might work just fine. http://fsae.com/groupee_common/emoticons/icon_smile.gif

-Charlie Ping
Auburn University FSAE 1999-present

[Denny Trimble]

Mostly it's good for very tight courses in the rain, which we have the luxury of practicing on 90% of the time http://fsae.com/groupee_common/emoticons/icon_rolleyes.gif

University of Washington Formula SAE ('98, '99, '03)

[Ben Beacock]

We're using the GSXR and a pneumatic system with compressed air. It was fairly easy to set up and we just ran a manual clutch. I don't have any problem shifting up or down without the clutch, but some of the novice drivers aren't quite used to it. I'm not sure how the internals are after that kind of 'abuse' (if you want to call it that) but it doesn't seem too harsh for me to be worried.

The weight of the composite cylinder, 2x3-way valves, bracket, tank, regulator and compressor (minus a hand shift lever and linkages) is a bit much but its reassuring to not take your hands off the wheel while driving.

Ben Beacock
Chassis Design and Technical Coordinator
Gryphon Racing - University of Guelph

[BStoney]

If you wanna go the electronic shifting mechanism route, think about designing a circuit that cuts fuel and ignition when u shift for a prescribed short period of time based on ur programming so you dont abuse the motor as much, the rotational inertia of the motor will continue during the shift and as soon as the shift is done, the motor will continue to fire again. It's probably the simplist way to do it I think....But it takes some knowledge of programming and some digital inputs on your ECU.

As far as a clutch actuator goes, manual is still gonna be your best bet (easiest to use I think, lightest, and easiest to manufacturer and package).

Just my 0.02

University of Cincinnati
bjstoney13@yahoo.com

[ben]

At Birmingham we've developed a semi-automatic clutch and gearshift system for this year.

It's all pnuematic and I think the cylinders are 25mm diameter for the shift and 20mm for the clutch. Will try and find out the system pressure from the guy who built it (obviously the cylinder bores are useless without that :-) )

Something we are quite proud of is that the clutch cylinder has two selectable discharge rates. A fast one for downshifts on the track and a really slow one to facilitate launch control. I for one was amazed at how good an open loop system could be in this role.

Ben

[A Reinke]

from our experiences the GSXR clutches are not easy to pull. we used a hydraulic clutch this year, which turned out to work really sweet without adding a lot of weight. if you are going with solenoid controled shifting, be sure to have some kind of linkage before the shift arm into the engine. we tried direct driving it last year and if it wasn't perfectly lined up the system would bind. we went back to a mechanical shifter this year, worked great.

[Ali]

Thank you for your replies.

So for you guys using electrical shifting and manual clutching, I assume you have to heel and toe into corners?

I plan to do shifting and clutching using one button motion, eg. Press button - clutch in and shift. Release button - release clutch. You can blip the throttle in between press and release. I've heard of cutting the spark on upshifts ( using a relay?). I'll look into that.

Also, I assume that for initial starting, the clutch has to be released in a relatively slower motion, so I guess that must be designed for.

[woollymoof]

Not sure about other ECU's but Motec has this facility in built.

[gug]

search on the net for spark retardation on proper motorbikes. its done fairly regularly for open throttle upsifting, and is often combined with a servo shift (i think). there is a few kits out there for it.
also, if you want a full pnumatic system, talk with Dave Cook: &lt;davecook@paradigmmotorsports.com&gt;, he designed Cal Poly Pomona's system and now makes a commercial system. he also posts on these forums every once in a while.

"I come from a land down under,
Where beer does flow and men chunder"

[Ali]

Thanks Gug. I've already got a shifting mechanism in mind. I'll check up on the spark retardation. The big problem is finding something to move the clutch.

But we still need to clutch for the initial 1-2 upshift right?

[Charlie]

Ali-

check your private topics.

-Charlie Ping
Auburn University FSAE
5th Overall Detroit 2003

[Garbo]

We have used pneumatic actuation for the last two years with a manual clutch... I think some teams using pneumatic clutches get it to work with a very fine bleed screw on the clutch piston ehaust which then has to be tuned. Most bike clutches are about 70 lbs (I think) so a piston this size is minor.

We have since switched back to manual shifting with a hydraulic clutch (hydraulic is key here as we've had bad experinces with clutch cables, on the line for the '02 auto-x, for example). Hydraulic is so sweet!

Garbo

[karter]

Once the car has left the starting line there is no need for a clutch, you can shift all bike motors by simply hitting the shift then letting off the throttle for an instant (or ignition cut).... actualy any manual trans, with enough pratice can be driven very well without a clutch and some in fact are a lot easier without (try a big truck, Roadranger 10 speed). Down shifts are the same story except blip the throttle when going down. Heal and toe is old technology .......

[Ali]

Thanks for all the replies. Think I'll focus on a mechanical stick shifter

[Mark Anderson]

We are experimenting with Pneumatic Shifting both the gear and clutch. We have a micro-controller that is full programable from a laptop. Our electrical guys determined that a electro-mechanical controller (Soleniod) would draw to much current to move the clutch and therefore a simple pneumatic valve and piston can be used. Have a look at SMC Pneumatic contollers for ideas, these guys have helped us heaps. However as I said we are only experimenting at the moment as reliablity is an issue. We have a simple mechanical shifter already design in case this fails.

UNRacing
Team Director - 2003
University of Newcastle
email: mark.j.anderson@studentmail.newcastle.edu.au

[Engelbert]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by karter:
Once the car has left the starting line there is no need for a clutch, you can shift all bike motors by simply hitting the shift then letting off the throttle for an instant (or ignition cut).... actualy any manual trans, with enough pratice can be driven very well without a clutch and some in fact are a lot easier without (try a big truck, Roadranger 10 speed). Down shifts are the same story except blip the throttle when going down. Heal and toe is old technology .......<HR></BLOCKQUOTE>

Firstly mate:
Heel and toe is old technology ? So is the wheel... I'm pretty sure both are still widely in use.

And no, not any manual trans. can be "driven very well" without the clutch. Have you had experience with every type of gearbox ?

When you consider the length of the shifting linkage (talking about mechanical, not hydraulic or any other 'exotic' system) on an FSAE car compared to the linkage for a motorcycle, there's a lot less stiffness, which means you cant just always 'bang' it into gear. I found using the clutch helps a lot in this situation.

Also, some people may prefer to use the clutch for vehicle balancing/stabilising purposes, esp when downshifting.

Sam.