What shifting system do you use?

[mech5496]

We used to use a ProShift unit on our second car, which was a step forward from the hand lever used in our first one, but we are still not so satisfied with it, and especially with it's reliability. It's main problem is shifting from 1st to 2nd gear. Sometimes it goes to neutral and we need to press the button 2-3 times to upshift to 2nd, which costs several time, especially during 0-75. At first we thought to remove the first gear from our gearbox and calculate the final gear ratio to start on second gear, or changing to an air shifter for our new car. The only thing we doubt(ed) is the weight of such a sustem. And I say we doubted, because in FSG competition I have discussed this issue with lots of teams and their answers confused me a lot. So what do you think we should use, and why, keeping in mind that we want a LIGHTWEIGHT and RELIABLE system?

[Drew Price]

Hey, welcome to the forum!

From the looks of what you said about your own experiences with reliability and concerns about the weight of the gas and pneumatic systems, you have answered your own question.

We use a mechanical system with a pretty moderate throw. After some teething issues and buckling one end of a #10 push pull cable (upgraded to a 1/4" cable) it has been very reliable, requires a very short arm at the shifter drum, and the whole system weighs about 1.5lbs. For a compressed gas system I think it can range anywhere from 3-5 pounds.

There are lots of threads about the reliability of these systems, and various problems people have had.

Best,
Drew

[HenningO]

http://www.paradigmmotorsports.com/html/actuator.html

Works great, no electronics needed (except for shift up/down paddles/buttons.

I'd say if the pneumatic hoses are installed properly, it is as reliable as a mechanical system.

[Brian S]

Two years ago we used the Paradgim system linked above. After some initial tuning of the gas pressure it works fairly well. The only major problem we had was related to the placement of the paddles and our steering. Not sure on the weights.

[Prohet][]

In 07 we used a Kilktronic acuator and we made our own control box so that we could program in safety features.

If I had to do it again I would very much look into using good drill motors. Our actuator on its own weighed like 1.8kg. Our big problem was that our actuator was too powerful to the point it ruined cogs on the gears. I beleive this years team made a much better control unit though which makes the whole system much more controllable.

[AndrewUofL]

We used an pneumatic system on one of our past cars (before I joined)and from what I have heard about it, it was not very good. Our main problem was that we could not get enough shifts out of our tank an had to get it filled quite often. We used a compressed air tank from a paintball gun. As soon as I joined we made a mechanical one. This past year we just used a mechanical pull-pull system using bicycle brake cables as the linkages and it works great. It is also very easy to adapt to paddle shifters if you want.

[Charlie]

My goodness, you are supposed to be engineers designing a car! So make your own system. It's quite simple.

Or, at the least, instead of saying your purchased system doesn't quite work right and what is a better purchased system, figure out why your system is lacking and FIX it!

[Dennis Seichter]

Yes, reliability is an issue with pneumatic systems, since a lot of things can go wrong. However, I think pneumatic (or other electronically controlled actuators) are superior to a simple mechanical link. Just think about ignition/gear cutting, automatic upshifting during acceleration, shift times.. etc.

In our first year car we had some minor problems with our self-developed system (CO2 pressure bottle, Festo cylinders, self-developed controller), so for this year we did some extensive hardware testing - you start with the components you have, build a hardware-in-the-loop testbench (e.g. cylinders and the controller and just play around with different cylinders, tube lengths etc), then after your car is finished, you go on the track and just test different configurations, look at the logged data and choose the best configuration. Actually this led to a lot more issues coming up this year than with last years system (e.g. liquid CO2 entering the system), but in the end it all helped us to understand the system better and make it more reliable.

I think a lot of teams underestimate (as we did in the first year) how bitchy a pneumatic system can be, but that's no reason for just not using it. You just need to do some more engineering work than you might think. Oh, and obviously, if you just by a system, you won't learn anything, and you can't do too much if it doesn't work.

[Sebastiaan]

If you are not sure about the reliability of a certain system, but would like to try it because it has some other features you like, why not have a simple but effective mechanical back-up. A shifting system for that matter is one of the easiest parts on a car with which you can experiment without taking a big risk.

[mech5496]

First of all I would like to thank you all for your answers.
We have considered building our own system, utilizing components such as purchased solenoids and build our controller, but being a small team (7-8 team members) and having only a little experience, means we cannot afford spending manhours on designing such a system. A mechanical system is a big "no no" for us, because of all the things mentioned by Dennis ("think about ignition/gear cutting, automatic upshifting during acceleration, shift times, etc..."). I forgot to mention earlier that we will switch from a Yamaha XT600 to a WR450 powerplant this year. So the first thing we are going to do is test our Pro Shift system on the WR engine. We suspect that the main problem in this year's car was that the solenoid was mounted on one of the chassis' tubes instead of being mounted on the engine. If nothing of the above doesn't work, we were thinking of using either the Kliktronic unit, that seems of better quality than the ProShift one, or this Paradigm actuator.

http://www.pitwheel.com/html/actuator.html

Has anyone tried this particular one before? Any problems/suggestions? Thanks again for your help and time!

[Superfast Matt McCoy]

After designing the pneumatic shifting system on our car and redesigning it for two years after, I'm still not convinced it is the way to go. For the same on-track performance (show me numbers) simpler is almost always better. I'm on board with UTA/Texas A&M with the mechanical clutch w/ downshift butterfly thing they've got with an electric kill switch on up shift. It just works, it's fast, it's easy to get into neutral, and I prefer that positive feedback; the ca-chunk, that says "you, sir, are in second gear now."

Also, I like Paradigm Motorsports stuff but we had one of those solenoids that was leaking and I replaced them with the industrial Ingersoll Rand ones from Grainger. Maybe we just got the one bad one, but the IRs worked so I stuck with them. Also, you can look at Grainger/McMaster and find the exact size pneumatic cylinder you need; one that fits your packaging with length and diameter.

BTW, there's an SAE paper on this worth reading.

[mech5496]

BTW, there's an SAE paper on this worth reading.

Thank you!Any link on this?

[Charlie]

Originally posted by mech5496:
We have considered building our own system, utilizing components such as purchased solenoids and build our controller, but being a small team (7-8 team members) and having only a little experience, means we cannot afford spending manhours on designing such a system.

No offense, but I am very unimpressed by this type of decision-making.

The time to properly decide on a purchased system is the same time, or less, that it takes to design your own. A pneumatic system is a very, very simple design exercise.

It is my opinion that purchasing a system is actually wasteful in terms of resources, and certainly does not promote any learning.

[Wesley]

We have been using the aforementioned Matt-designed CO2 system for 2 years, with varied success, then switched in '08 to a new system.

The previous system was a solenoid actuated pneumatic cylinder with CO2. The calculations said "good for 1000 shifts," but in practice, we'd have dead bottles all over. Either they would leak, they'd freeze up the solenoids (even after installing a large expansion chamber) or the bottle would heat up in the sun and blow the safety valve.

In '08 we switched to a nitrogen (or compressed air) system. It's lighter, theres no phase-change associated pressure spike like with CO2, and better yet, there are fewer connections. We've had the same bottle attached to the car since the California event, and it still shifts the car. Theoretically we have less shifts, but in practice, we actually get to use all of our N2 shifts versus almost none of our CO2 ones.

The system has been bullet-proof thus far, plus it's easier to hit neutral consistently with better pressure control.

[mech5496]

Thanks for the feedback!
So, did you use a brand new system, or did you midified your previous one to work with nitrogen? In case of compressed air, did you have any problems with air humidity?

[Mike Cook]

I think a lot of those pneumatic and electronically controlled systems offer very small gains given the risk they introduce into the system. While a mechanical system isn't exactly easy to design and get right, after they are setup they generally work flawlessly for the life of the car (as long as you avoid lots of misalignment in the joints). It also seems like a big plus to me to not have to worry about refilling tanks and what not.

Given that you are a small team, I would definitely just go with a good hand shifter so you can dedicate your time to more important issues.

We use a hand shifter (butterfly style). If you pull the first lever back it up shifts with out clutch. If you push the first lever forward it clutches and then downshifts. You can also pull both levers together to clutch and/or up shift. I like the system a lot because you automatically clutch on downshift and because of the linkage, they are synchronized.

Up shifting with an ignition cut is a good idea but I don't think it's that simple to implement imo. We have been working on a strain gauged linkage that is used to cut ignition but never really had time to finish it.

We won acceleration at VIR and West with our current system (with less power and a lot more weight than our competitors (494lb/69peakhp). I think there are a ton more things to look at besides a shifter like, track and wheelbase, weight distribution, gearing, average power, tire selection and pressure, and car setup. Of course, if you don't practice you're not going to be very good either.