# Wiper Motor Arm Thread Issue



## Armor78154 (Aug 19, 2010)

I had an issue with the crank arm I got from Monster Guts. The spline threads seem to be worn on the inside of the mounting hole. So I am going to try and attach the arm directly to the motor using JB Weld. I am being careful to keep the rotating parts free of the JB Weld, but hopefully the material will hold up to the rotation of the arm. I am going to try and minimize the torque on the arm.

Has anyone else had this issue, and if so, how have you fixed the problem...aside from replacing the arm or motor and arm?

Is there any way to mount the armature without using the spline threads on the wiper motor?

I would appreciate any assistance with this problem...especially as my Rocking Granny is almost finished, and now I have had this issue come up.


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## Otaku (Dec 3, 2004)

I never use the original crank arms. I usually need a longer throw for my props, so I make one out of 1/2" X 1/8" aluminum flat bar. Drill a 1/4" hole where you want to connect to the shaft, and put a slight chamfer on the side that will be facing the motor. Works every time.


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## Armor78154 (Aug 19, 2010)

How did you put the chamfer on the side of the hole facing the motor spline? I was considering how I have been drilling out the holes, and I do not have a chamfer bit.


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## Otaku (Dec 3, 2004)

I have an old 1/2" bit that I use for applying the chamfer. You really only need to break the edge so the splines on the shaft can get a bite. A Dremel grinding stone bit will also work.


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## niblique71 (Dec 2, 2009)

We had that problem with one of our MnT motors for our rocking granny project. We just added a washer to the outside and tightened it up good. I'm skeptical that it'll work long term. I'm not sure if it was the motor splines or the Arm splines that failed. I like Otaku's solution.


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## Vlad (Aug 2, 2005)

As I remember the problem from our make and take, and believe me it's hard to remember anything after a NJ make and take, the problem was that the new bar stock arm wasn't as thick as the original wiper motor arm, and that the washer made up the difference allowing the nut to completely tighten down on the bar.


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## Armor78154 (Aug 19, 2010)

What methods did you use to bend the arm into shape? I am doing this without a vise, so bending the arm seems to be a difficult proposal at best. I found out the JB Weld could not survive the starting torque on the wiper motor, so that was a bust. I think I will try to construct my own crank arm, but I am looking for some tools, trips, and tricks for crafting said item.


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## Otaku (Dec 3, 2004)

The 1/8" flat stock is easy to bend. I use two sets of pliers to make the bends, even 90° corners.


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## Vlad (Aug 2, 2005)

Armor, a good investment as far as tools is a good vise. Even if you don't have a workbench to mount it on. I carry a fairly large vise mounted to a board to the make and takes. They're handy, and make so many things easier and safer. Look for one that has rounded jaws under the flat normal gripping jaw to also hold pipe, and one with a flat section on the back to be used as an anvil. They're not all that expensive, and I also often see them at garage sales. You won't find an easier, or more precise way to bend stock than with a vise. Ask anyone on the forum, I know all about vices, lol.


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