pneumatic clutching

[Parker]

I was wondering how a solenoid would handle clutching duties with a pneumatic clutching setup? We are looking at using a setup where there is a two position swtich to activate the clutch at a half-depress and then make the downshift at full depress, however there are a couple of teammates who believe that having a clutch pedal or hand clutch would work better.

My argument is that it will make the driver's job easier, since nobody has driven the car before, but hey, you know...

[Parker]

I was wondering how a solenoid would handle clutching duties with a pneumatic clutching setup? We are looking at using a setup where there is a two position swtich to activate the clutch at a half-depress and then make the downshift at full depress, however there are a couple of teammates who believe that having a clutch pedal or hand clutch would work better.

My argument is that it will make the driver's job easier, since nobody has driven the car before, but hey, you know...

[raska]

I like the idea, but it will require considerably more testing and tuning than just a manual clutch and pneumatic shifting setep. You have many scenario to deal with, from gear shifting, to launching, to moving at a crawl, to dropping the clutch and doing burnouts (maybe you can leave this one out). For most teams, I think a clutch handle works best because it leaves the feedback all to the driver, who isn't new at the principles of operation of a clutch.

[Marshall Grice]

covered at length already.

[Erich Ohlde]

Hmm. Pneumatic clutch, sounds interesting. I like it.

[Superfast Matt McCoy]

If you use a pneumatic shifter, you should definitely use a pneumatic clutch on downshifts. We also have a manual clutch. Having designed, redesigned, reredesigned and driven the system for the last three years, I think this setup is clearly the best. It shifts every time, it is very easy to use, and if you are careful, it weighs about as much as a manual shifter. Also, it requires almost no "testing and tuning" since you still retain the manual clutch.

[Parker]

Matt, did you guys end up using a pedal or hand clutch? Im also guessing that your clutch cylinder needed to be smaller than your shifting cylinder as well?

Raska, I see your point. I just assumed that if the car was moving at a crawl, that there would be someone pushing it anyway.

[Superfast Matt McCoy]

Hand clutch. Both the shift and clutch cylinders and 3/4" bimba-type cylinders. Make sure the cylinders bottom themselves out before the shift lever or clutch lever reaches its end point, else you will have broken levers on your car.

[mtg]

That sounds like a good way to be stuck in first gear through half of the endurance when the solenoid gets fried by the overheating coolant line that got moved at 2am the night prior to endurance in a mad rush trying to install last minute pieces to hide the oil that's leaking out of the diff.

Keep It Simple Stupid

[Kyle Walther]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by mtg:
That sounds like a good way to be stuck in first gear through half of the endurance when the solenoid gets fried by the overheating coolant line that got moved at 2am the night prior to endurance in a mad rush trying to install last minute pieces to hide the oil that's leaking out of the diff.

Keep It Simple Stupid </div></BLOCKQUOTE>

sounds like all that could be avoided with a little planning and preparation.

[Sooner_Electrical]

Having driven a car with pneumatic shifting/clutching, Manual Clutching/Pneumatic shifting, and a Manual Shifting and Manual Clutching over the years I am going to have to say if team has the capabilities the Pneumatic Shifting and Clutching is by far the easiest to drive and quickest shifts, and can be made reliable.

[jack]

i looked into it long ago. i think the hardest part is timing, for instace, the clutch needs to be a little bit out of phase with the shifting (the clutch disincages a bit before the shift, and reingages a bit after)how ever this delay is set up (probably electrical) it needs to be adjustable easily, so the system can be fine tuned.

also, down shifts might be really harsh if not rev matched well.

[raska]

Jack that could be worked out with testing. I think most already have adjustable delays implimented between and for the durations of spark cut, and solenoid fire. We use 3 that are timed differently, plus the shift button debounce.

So all you guys that have done it: Are you just talking about running it in parallel with a manual clutch for shifts? Or if it becomes the only actuation method, how are you controlling launches and such? A fixed bleed valve and just sacrificing very low speed feathering along since it's not really used?

[Ashley B.]

In my years of working with pneumatics on D/C sports racers in road racing, and in NHRA class, the peumatic shifter is an easy to use and highly relibale peice of equipment. When we used it in road racing, we simply had a delay timer that would place the cluthcing out of sync with the the shift. We also used a progressive push button that could vari the clutch seat pressure. However as the cluthc pressure could be varied, the shift time would remain constant. This same style setup on our Super mileage car a few years ago. Overall i believe our system cost roughly $225, with the PROPER componet selection this system will NOT burn up.

[Superfast Matt McCoy]

We don't have any timers or out of phase clutch/ignition kill. in fact, the solenoid that opens for a downshift has a T after it so that it actuates the shifter and clutch at the same time. same deal with the ignition kill on upshift; they both activate as soon as you push the button. with this setup, our shift time (measured with peak-to-peak G's) was around 0.2 sec. I see no benefit with timers or multi-stage buttons.

[Ashley B.]

The use of a mutli stage button (or Progressive) alows the driver to slip the clutch in the the case of comping out of a corner and the driver is between gears. Thus you are allowed to keep the engine in its power band. Yes it does eat the cluthc up a little faster but it will still last the race. As far as the time delay between the cluching and the shifting, we use it because it save unnecessary wear and tear on the transmission.

[Parker]

I would think that having the relay for the clutch activate the relay for the downshift would be plenty of delay between clutching and downshift.

now, for the upshift, I'm guessing that most of you use engine management for the ignition cut function. From looking at the wiring diagram for our GSXR's harness, it appears that the sidestand switch actually trips a relay in the relay box to cut ignition power to the coils. I was thinking of using this, but without having the stock ecu on there I'm not sure if it will work. only time will tell...

[Ashley B.]

The only reason we use a timer is to adjust the shift time based on the track. In other words if hte car is climbing a hill the driver can lengthen the shift time which will let the "wind-up" due to the cluth being pushed, this acts in a way similar to droping the clutch at a starting line. It also works the oposite for down hill, the driver can shorten the time becuase the "droping the clutch" method for up hill is not needed.

By the way, we are only talkin 100 to 500 thousandths here.

[raska]

Ashley, on the pneumatic side of things what is changing based on the button position? i.e. What are you using to find an intermediate position of the clutch to slip it, or are you just talking about letting the engine rev higher and then having the pressure plate be released at the same speed all the time?

Parker, you can just make another output from your shifting circuit which toggles power to the coils or an ignition module to cut the spark when shifting.

[Dave Cook]

We used a staged downshift/clutch paddle setup that does this in 2000 at Cal Poly Pomona. I've iterated the paddle setup twice since then and I have some that I am selling. You can see pictures and a description of the assembly at www.paradigmmotorsports.com (http://www.paradigmmotorsports.com) .

We only had a gas and brake pedal, and used a manual hand clutch for launching the car. With the 2 stage paddle lever you can also use the paddle clutch lever for upshifting or just sitting in the pits stationary. This is an on/off clutch requiring the driver to blip the throttle after the last gear is downshifted. This shouldn't be a problem because the driver had his right foot over the gas pedal the whole time. The clutch automaticaly gets pulled before the downshift because it is the first stage of paddle throw.

There is also some good info and data from the engine kill system we used. I will get some models of the paddles and shifter parts posted so people can download them.

Dave

[Ashley B.]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by raska:
Ashley, on the pneumatic side of things what is changing based on the button position? i.e. What are you using to find an intermediate position of the clutch to slip it, or are you just talking about letting the engine rev higher and then having the pressure plate be released at the same speed all the time? </div></BLOCKQUOTE>


The amount of pressure on the clutch pack is changing, basically the clutch is operated via pneumatic ram, the progressive button then adjusts the amount of pressure on the clutch. By the way, the button has about 1" of travel so that it is not hyper sensitive making it easier for the driver to dictate how much clutch to apply. The clutch is applied and released at different speeds all the time.

Hope that helps

[raska]

What type of pneumatic regulator did you use for this? Or did you do it through pulse width modulation of the solenoid to control the CO2 going to the cylinder or something?

I'm just trying to picture the best way to do this with CO2. It would be more intuitive hydraulically.

[Ashley B.]

It was pulse width modulated