Shifting Force Calculations

[Kev2005]

Hello everyone, i'm working on a single-seater project which is very similar to a Formula Student Car.

I'm planning to use a manual sequential gear shifter and having some trouble with the calculations involving moments for the shifting/transfer forces at both the gearbox and the lever. Could anyone help me with that please ?

would also like to have a few suggestions regarding improving the acceleration of the car, for e.g changing gear ratios, getting rid of a few gears or effects of changing the output sprocket shaft. Any suggestions ?

thanks.

regards kev.

[Kev2005]

Hello everyone, i'm working on a single-seater project which is very similar to a Formula Student Car.

I'm planning to use a manual sequential gear shifter and having some trouble with the calculations involving moments for the shifting/transfer forces at both the gearbox and the lever. Could anyone help me with that please ?

would also like to have a few suggestions regarding improving the acceleration of the car, for e.g changing gear ratios, getting rid of a few gears or effects of changing the output sprocket shaft. Any suggestions ?

thanks.

regards kev.

[TorqueWrench]

Best bet to measure your forces is to hook up a force gauge (physics department should have them if you don't) and you can calculate the moments from the lever arm.

As for the rest of it, do some research. You will find a lot of varying opinions on the rest and they have all been discussed in depth already.

[Drew Price]

Depends on your transmission, on how well you rev-match, on what kind of linkage you use, and what you want to get out of it.

I used a push-pull cable on a drastically cut down foot shifter (maybe 1/3rd it's original length) for our Suzuki ATV trans, and a lever with about a 5:1 ratio, and it yielded shift force at the lever of probably 12-15 lbf when the car was rolling, and shift distance around 1 inch at the end of the lever.

I liked it a lot, and would do it again like that without thinking twice. Other than I would use two bicycle cables to pull the linkage in each direction rather than one push-pull, it would be lighter, cheaper, and easier to route.

We had issues with a 0.25 in. cable buckling at the end initially when we had the ratio too high initially, and had to step up to a 5/16ths cable, which was HEAVY, and could only be bent to about a 5" radius, so unless you have a straight shot to the shift lever that might be tricky.

Dual smaller tension cables lend themselves really easily to a steering column mounted mechanical paddle too, makes the cable mounts symmetric and all that. That's actually how I would do it.

Best,
Drew