Can I use a shaft more than 12 inches long?

VEX does not provide an 18-inch shaft.
It’s very difficult and unstable to connect two axles by myself.
Can I use a shaft of the same thickness but longer than 12 inches?

You can use shaft couplers, which you mention are unstable. However, if you insert a lockbar connection in between the two axles (standoff two metal lockbars off of each other, then insert two axles from each side through a lockbar into a shaft coupler into the middle) we’ve found that the connection is pretty stable.

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Strength is still not enough.And it takes up a lot of space.

How much space do you need? the connection only takes up a tiny bit more than 1 inch of length, and is the same amount in width

You may not use a single drive shaft longer than 12".

<R16> allows you to cut VEX’s drive shafts into smaller pieces, thus allowing any drive shaft shorter than 12", but <R5> prevents you from using any non-VEX drive shaft, eliminating anything longer than 12".

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If you are linking gears or sprockets teams use lock bars screwed on to the gear/sprocket and slipped on the shaft then attach stand offs to give the shaft support. The shaft still needs a coupler but it is not a weak link anymore.

Thank you. I hope the IFI can produce an 18-inch shaft. It will save a lot of trouble.

You could take two of them, cut/file a tongue and groove joint in the ends and secure it with a shaft collar. Some form of spline might work better, now that I think of it… much easier to do on the high strength stuff, of course.

You could also build a custom clamp for the regular axles by drilling and broaching a piece of high strength shaft, then tapping the side for set screws.

I know not every team has access to that kind of technology, but if your school has a metal shop, or you know a machinist and ask nicely (and explain that you can’t weld/braze/glue) then they might be able to help you learn a new skill.

Jason

But I should add that transmitting any significant torque over a long distance will result in significant shaft twisting… and perhaps failure.