Shifter solenoid choice?

[bringo]

A question for the teams that have made their own electric solenoid shifter systems. I'm looking into doing this for next year's car, and I'm having trouble finding a suitable push/pull solenoid. As others have said, the CBR600 gearbox requires about 25 lb of force to get the shifter moving with the stock 1" lever. The one company that had a promising solenoid listed on their website told me that it would burn up if it was cycled more than 5 or 6 times a minute. What solenoids have you had good experience with?

[IsheeM]

I would also like some information on this. I have been searching for quite a while now with no luck.

[Agent4573]

you could always try our route, a bit different but it seems to work for us. take an rc car motor and mount it to a 18 volt cordless drill transmission. Works like a charm, but you have to replace the brushes every year.

[Igor]

Try to stay away from the big coil and armature solenoids, they are ridiculously heavy for the little force they give. If you set it up just right it works most of the time, but not all the time. It usually lacks power to push through when the shift is missed.

After market trunk type solenoids aren't really solenoids, but a small motor with a plastic ball screw. This will get you far more power per weight, but they are designed to operate only occasionally and thus have thermal issues. I have a molten one lying around somewhere, but that one was really tortured. I also think they're not sturdy enough for this application.

I've seen a sweet version made by Lulea, which was an RC motor linked to a metal ballscrew with a pulse encoder for the control electronics. Lighning fast.

I like the cordless drill idea. Will it damage the transmission if it doesn't engage right away or isn't there enough force?

Igor

[Cement Legs]

Bringo, where did you get the 25 lb number? A couple of guys on our team welded a piece of hex-stock onto the splines so they could fit a socket over it. With a torque wrench they measured 45 lbs/in.

[syoung]

We use a unit by Kliktronik (http://www.kliktronic.co.uk). They are a UK company but list US, Aussie and other distributors. It's fairly heavy, and subject to going wrong if you don't install it nice and straight, but it should do the job for us. Long-term (i.e. next year) I'd like to see us move on to looking at electro-pneumatic actuation.

[bringo]

The RC motor and drill transmission sounds like a good idea. I might have to give that a try. Unfortunately premade units like the Kliktronik are too expensive for our team.

Cement Legs - I just used a cheap pull-spring force gauge. 25lb is what it took to get the shifter moving. I didnt complete a shift b/c the gauge wouldnt read any higher, so your measurement is probably much better. Thanks for the info.

[Patrick W. Crane]

We use a solid linkage from the shifter to the engine made of carboin tubing and some bonded aluminum ends. Never misses a shift, nice light action, and weighs around 250grams.

But we have no elec guys on the team trying to convince us to do something silly http://fsae.com/groupee_common/emoticons/icon_wink.gif

[Chris Boyden]

Another thing to look at is high speed linear dc motor drives.

[gug]

Originally posted by Igor:
I like the cordless drill idea. Will it damage the transmission if it doesn't engage right away or isn't there enough force?

Igor

im sure there are others around here that know more about transmissions than me, but AFAIK the only way to damage a motercylcle transmission is by shifting too slow. the dogs grind instead of engaging, and pretty quickly the transmission dies.

of course, thats in a normal application. we would probably stuff some other part of the engine before crappy shifting could destroy a gearbox.

[Agent4573]

We've been running it for two years now with no problems.

Well i shouldn't say no problems, but im not sure if they are related. Instead of losing a dog on second gear I believe we lost an actual tooth out of second gear one time, but thats why the new yamaha engines are coming with more robust second gears now, cuz even bikes tear them up.

[bringo]

another question if you guys dont mind: what is your clutching scheme? Do you do it at all? do you use ignition interrupt (if so, is it a complete ignition cut or a soft rev limiter)?

I'm thinking of using a soft rev limiter with no clutch for up shifts and clutching with a pneumatic cylinder for downshifts... its the downshifts that im worried about.

[syoung]

Yeah it's the downshifts that are the harder bit - especially when auto-blipping of the throttle isn't (as far as I understand) allowed.

[Jeff The Pyro]

It took us forever to track this down, but a company named trombetta makes pull type solenoids that are almost perfect for this application. I dont remember the exact part number, but the ones we use have approximately 25lbs of force and 1" travel. We were searching for quite a while and the problem with pretty much all of them was that they didn't have enough travel.

[Marshall Grice]

We used to do a pnuematic clutch on our older cars that was activated for downshifting. Turns out it's incredibly difficult to get a smooth downshift when your clutch only has two positions(on or off). We've since ditch the pnuematic clutch and our downshifting performance has increased; based on reduced shifting times and smoother transitions, not to mention decreased weight and decreased complexity. Obviously the driver needs to blip the throttle to initiate a downshift but once they figure that out everything is cool.

Personally, i wouldn't waste my time with any sort of pnuematic clutch system unless you were able to implement some sort of continuous control that would allow the use of the clutch for launching, thereby eliminating a clutch handle/pedal.

[Charlie]

I keep seeing this and it boggles my mind http://fsae.com/groupee_common/emoticons/icon_wink.gif. Why do you have to clutch on downshifts at all? We never did. If you can do clutchless upshifts why do you have to clutch on downshifts? And why would you want to make an (IMO) overly complex downshift clutching mechanism (ie, pnematic or electronic clutch control) when you can do totally without it?

[romkasponka]

because engine acts as brakes, and after downshift you will loose traction on rear wheels. You should use throtle for smooth gear change and clutch.

[raska]

Originally posted by bringo:
another question if you guys dont mind: what is your clutching scheme? Do you do it at all? do you use ignition interrupt (if so, is it a complete ignition cut or a soft rev limiter)?

I'm thinking of using a soft rev limiter with no clutch for up shifts and clutching with a pneumatic cylinder for downshifts... its the downshifts that im worried about.

Our drivers typically use clutch for downshifts, but we have full ignition cut.

Pneumatic cylinders for lever actuation works very well. It packs a good punch without all the weight of the solenoids - although of course solenoids are still needed in the system, but little tiny ones that weigh very little.

[Charlie]

Originally posted by romkasponka:
because engine acts as brakes, and after downshift you will loose traction on rear wheels. You should use throtle for smooth gear change and clutch.

I understand that, but in our car and I'd guess most FSAE cars the final drive ratio makes the gears effectively VERY close together. You don't get enough difference in engine braking to upset the car, even on double downshifts.

That's the main theory behind using the clutch for downshifts, however for small drops it doesn't hold water, and if you complete you downshifts in a timely matter and in a straigh line while braking, whats a little engine braking matter? Not much for us the last 5 years.