Help me with the gear shifter mechanism!

[Scrutinizer]

Hi,
I am a member of IUT Formula Student team and am looking for an appropriate mechanism for our gear shifitng. We have a 1>N>2>3>4>5>6 RR 600cc engine. I have thought to use a double wire system. If I want to use a pneumatic system, how can I get along with the 1>N>2 pattern?
Plz help me.
Thanks.
S Mohammad Reza Shahshahani

[Scrutinizer]

Hi,
I am a member of IUT Formula Student team and am looking for an appropriate mechanism for our gear shifitng. We have a 1>N>2>3>4>5>6 RR 600cc engine. I have thought to use a double wire system. If I want to use a pneumatic system, how can I get along with the 1>N>2 pattern?
Plz help me.
Thanks.
S Mohammad Reza Shahshahani

[Chris Allbee]

you could use a very complicated system involving microcontrollers. Have it go through the microcontroller so that during a shift event it monitors the neutral light signal from the motor and if it detects it holds open the solenoid for a slightly longer period of time to guarantee the shift. Or just have it run through a relay with a long enough delay to guaruntee the shift every time. Third option, hard wire the button (paddle, small gnome, etc.) to the solenoid and just have your driver hold it down as long as it takes to shift.

[Rex]

Option 3 gets my vote. That way you don't have to have yet another electrical "solution" (i.e. some kind of alternate button, or switch, or whatever) in the event you actually do want to stop at N.

[formula_wally]

1 - Remove 1st gear, change your final


or


2 - Offset your barrel 30 degrees by milling the paths on the barrel and run N-1-2-3-4-5-6, the spring cam also has to be modified

[drivetrainUW-Platt]

replace your "double wire" with a "push pull" or solid linkage system.....

[gambino]

A push-pull cable is a great idea for a mechanical system. Very reliable too if set-up correctly. If you want to run pneumatic shifting, the 1-2 shift will usually skip over neutral when you push the button. The only way we can get into neutral is by very lightly tapping the upshift button from 1st gear. It's actually pretty tough to miss the 1-2 shift and hit neutral. That's something I was also worried about when installing pneumatics on our car. This is the first year we're running pneumatics.

[Scrutinizer]

Thanks a lot. I should check some of these.
I also should check the solid linkage possibility.

[Mexellent]

I dont know about a push-pull cable. Maybe if the path of the cable is relatively straight and free from getting "squooshed" by the driver. It takes a pretty big amount of force to change gears on the engine. I think it might be (but i could be dead wrong) about 50lbs with a two inch arm at the engine(F4i). I would be hesitant to put that much push on a cable. Just my two cents.

[Nitesh]

we have used push pull cables in the past and are using it again this year. they are good enough to take the load of a shifter. no problem at all.

[KU_Racing]

I would guess that the shift pressure is nowhere near 50 lbs. I can shift our trans with my hand pulling on the lever, and its not that hard. 20 lbs, maybe 30?

[Mexellent]

My bad. I had shifter force mixed up with shifter torque. With a two inch arm, 20lbs sounds about right.

[Wesley]

A dual cable system is very hard to make work. We tried and tried to come up with an idea to have a paddle-operated dual cable design - but (to us at least) it is impossible to have two cables pull in opposite directions because you have to constrain the housing in relation to the point you want to pivot. The two cables end up fighting each other no matter how we put them.

I do recommend a push-pull cable. Summit has some that it sells for automatic transmission shifters that work very well and can transmit a lot of force without distortion.

Also, a solid linkage works very well (thats the route we ended up going) and can be made with almost no slop in it if you use rod ends. You can also include a rocker pivot so you can achieve a comfortable shift effort with mechanical advantage (which is what we did.) It works flawlessly so far, and the feel is excellent. I can snap a few pics even if you would like.

We ran a tie rod from the shifter arm to a pivot arm on the lower frame - from which it was a straight shot to the shifter arm. Shifting effort is maybe 7lbs.

On our f4i, we measured the shift force at 16 lbs with a 2" arm.

As it is, you can shift without a clutch (just like a bike) if you let off the gas, but if you were clever you could mount an actuating button to cut throttle and have a no-lift shift system. It's also super easy to find neutral while all the pneumatic guys (our '06 and '07 cars) try to half-shift with a pushbutton.

[gambino]

I guess some pneumatic teams have problems with half shifts into neutral. I guess I got lucky with our system. It isnt that hard to get into neutral. But I guess that's the sacrifice we pay for getting quicker shifts. Just my two cents. Either way, both pneumatic and mechanical systems have their ups and downs.

[Scrutinizer]

Thanks all you guys.
Wesley, I'm eager to have the pics you said. Can you also tell me more about the push-pull wire system?
Thanks in advance.

[Wesley]

Basically, it's just a cable with a stiff and positively constrained housing. Made for an automatic transmission. You could use a paddle system, or a shifter handle system. Another problem we ran into with a mechanical paddle shifter is having it rotate with the steering column, the cable runs into our front bulkhead. Not necessary, but nice if its a paddle system.

Jeg's Link (http://www.jegs.com/webapp/wcs/stores/servlet/product2_10001_10002_745839_-1)
http://www.jegs.com/images/photos/890840200.jpg

I couldn't get Summit to come up, it's usually got cheaper stuff. They've got quite a few lengths.

Our mechanical shifter system (prototype) wasn't really "engineered" but we ran some quick numbers in our heads for the proper motion ratio. I'll snap some pictures next time I'm up at the shop.

[Superfast Matt McCoy]

Here it is '05 Cornell style:

http://sae.ou.edu/cornellshift.jpg

[Scrutinizer]

Thanks for the pics.

[Biggy72]

We get our push pull cables from mcmaster. They're generally around $45 in most lengths.

[Wesley]

Pics. Ignore the rust, it's the '05 car. Paint will go on after '07 is done. Also ignore the ugliness. A future real version would look much better.

http://photos-891.ak.facebook.com/ip002/v72/181/98/9619773/n9619773_33527891_4057.jpg
http://photos-892.ak.facebook.com/ip002/v72/181/98/9619773/n9619773_33527892_4371.jpg
http://photos-893.ak.facebook.com/ip002/v72/181/98/9619773/n9619773_33527893_4679.jpg
http://photos-894.ak.facebook.com/ip002/v72/181/98/9619773/n9619773_33527894_4982.jpg
http://photos-896.ak.facebook.com/ip002/v72/181/98/9619773/n9619773_33527896_5286.jpg

I did forget to take one of the actual arm linkage - but its just u-channel steel with two holes drilled, one for the shift arm and one for the linkage.

[skillet]

that looks slick. can you give me the dimensions of the arm length used for the shifter at the motor, at the handle and at on the crank?

[Ppada]

http://www.proshift.co.uk/
It might help

[Wesley]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by skillet:
that looks slick. can you give me the dimensions of the arm length used for the shifter at the motor, at the handle and at on the crank? </div></BLOCKQUOTE>

If I gave out all the info, what fun would that be?

Just do a FBD of the system, decide what you want your shift effort and motion ratio to be, and calculate your lengths from there. Then you don't have to find a special shifter arm - you can use whatever you have (which is what we did, can you tell?)

The rod ends are also way oversized in that pic, we just had them lying around, also the shifter pivot is in single shear, and is inelegantly mounted.

But we thought the badass skull made up for that. Plus some. And it works like a dream.

[epitrochoid]

This year we are going to try to use the shifter very similar to the Link above, an electronic actuator by company called Klictronic.

Downsides - Heavy, and 35 amp (yes, 35 amps!) current draw when energising the coil but it has a neat controller package which automates the neutral finding position and has an external output to an interrupt which can be used inconjunction with their own interrupt module or I'm just using it as a trigger to relay my ECU's spark cut pin.

[benjo]

Correct me if I'm wrong but isn't the kliktronic around 900USD? Thats alot of extra money to account for in the cost report.

Edit: Whats the cost for the Pro-Shift?

[ad]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by benjo:
Correct me if I'm wrong but isn't the kliktronic around 900USD? Thats alot of extra money to account for in the cost report.

Edit: Whats the cost for the Pro-Shift? </div></BLOCKQUOTE>

Who said it would go in the cost report?

[Garlic]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by ad:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by benjo:
Correct me if I'm wrong but isn't the kliktronic around 900USD? Thats alot of extra money to account for in the cost report.

Edit: Whats the cost for the Pro-Shift? </div></BLOCKQUOTE>

Who said it would go in the cost report? </div></BLOCKQUOTE>

Oh, I don't know, someone who was honest?

[KU_Racing]

Its only called cheating if they catch you.

We used an electronic system a couple of years ago, but we had trouble making everything work. Id suggest trying to find out how good the customer service is on a commercial unit before you buy one.... motorcycle forums can probabably help with that.

[Ppada]

about 850 euros for the pro-shift
And i agree its heavy.

[Welfares]

We have used a Mechanical linkage in the past, they're good if you can fit them.

At the moment we're using a Teleflex (Who bought out Morse Controls) 43C. It's worked really well so far.

There are different size push pull cables (diameter, not lenght) don't go for one that's to small.

[ad]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Garlic:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by ad:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by benjo:
Correct me if I'm wrong but isn't the kliktronic around 900USD? Thats alot of extra money to account for in the cost report.

Edit: Whats the cost for the Pro-Shift? </div></BLOCKQUOTE>

Who said it would go in the cost report? </div></BLOCKQUOTE>

Oh, I don't know, someone who was honest? </div></BLOCKQUOTE>

Sorry, i wasnt trying to be dishonest. Just not everything has to be put down as the 'bought' price. The manufacturer may even quote it as the manufactured cost which would be much lower than that.