Shafts Bent

Hey guys this is just a heads up. I will be changing accounts, so this will be my last post using this account. My new teams account will be Bluethunderlegacy.

Alright so this question is asking about how do you guys fix your bent shafts, so that there as good as new?
Is there a way that is the best?

I’m asking these questions because my team has bents shafts that we want to recycle them. These shafts are not like twisted, and don’t look like a drill bit.

You are not really ever going to get them back to being as good as new, bending it back will only weaken it and you will likely struggle to get it back to being straight. My advise is to 1. get new shafts and 2. design your robots knowing that the shafts are not always as strong as you would like them to be. We have all bent shafts before, it is what you learn from it that is important.


Tighten down in a vice grip, rotate, tighten again. Hope it works, be willing to accept if it doesn’t.

Agreed - Once you stretch the metal (when you bent it), hand tools will never get it compressed back to its original shape.

Even if there slightly bent.

Slightly bent ones, such as say 10 degrees we usually just bend back, depending on the length (lets say 4" shaft) we just try and bend it back as much as possible using vice grips, pliers, or hands. It’s quick and dirty but like the posts above its never quite the same.

I’m having a difficult time picturing what you’re describing. The shafts aren’t twisted, but they look like drill bits? Doesn’t that mean they’re twisted? Twisted axles are a lot harder to “fix” than bent ones…

In any case, I advise against trying to reuse shafts that have been bent or twisted, because you can’t ever get them back to factory condition and they’ll never be as good as new ones. If you have to, they’d probably be OK for prototypes. Otherwise, hang them from the ceiling as a reminder of what happens when you overstress a shaft.

How do you guys test for bent shafts?
Do you guys have a tool?
Wondering because what if the shafts are slightly bent.

What is the problem with reusing bent shafts on your robot?

It’s crude, and it depends on what your definition of ‘slightly bent’ is; but I just put it on top of a flat metal surface and compare it to that. Something like the top of a solid metal vice/table clamp should work for you.

Easiest way to test is roll it on a table top or flat granite surface if you have one. Look for daylight between the table and the shaft in the middle or ends. Also if you stick the shaft in a drill and spin it you can see how much wobble you’re going to get.

Do you really want to introduce needless variability in your autonomous or dirivng? Keep it straight is the way to go. A wobble or shimmy just leads to unpredictable results. And once deformed, more deformations are all the easier like others have said.

For example. if you have two motors lifting your four bar or six bar linkage, a bent shaft on one side could lead to not very smooth lifting causing the one motor to work harder. If you have a bent shaft on a wheel it could lead to wobble or at worst seizing since the stress is now on the other plane when it should be free wheeling it through the square holes between the motor and the gear/wheel.

Some places it may not matter much so it can be OK, but generally straight shafts are wanted. Some shafts seem to end up in hard to reach areas requiring much disassembly to replace them. Time rebuilding at a competition is to be avoided if possible.

The shafts are generally one of the cheaper parts so keeping a good stock of them on hand is probably a bit cheaper than other parts. Just do this roll test when you receive the parts since we have received some shafts kindly pre-bent for us :slight_smile:

if its a full 12" shaft with a slight bend in the middle
maybe you can cut them up into shorter pieces? (and not use the bent section)
it really depends on the shaft