Countersunk holes worn out of round.

[twinrider1]

Wallered out, I believe that's the machinist's term.

I gave my no-stamp chassis a good cleaning last night. What I found is the holes where the rear a-arm mounts....mount have worn themselves a bit out of round; maybe 1/32" on the wheels side of the hole.
Is there a standard fix for this sort of thing? Is it even much of a problem in real world use?

[RC10resto]

Where's the pics

[kaiser]

they must have been loose for some time in order for them to wear like that. it's never happend to me.

[twinrider1]

Pic added to original post.

[jwscab]

yeah, it will happen over time when the parts are allowed to rock, and hard landings/shock to the arms will continue to hammer those mounting holes.

I have a couple of graphite chassis that I am going to repair in the following way:

I have .015" sheet stainless steel that I will be cutting to fit on the chassis, sandwiched in between the trans, arm mounts and chassis, basically, make a pattern from the bulkhead to the rear of the arm mounts. Since the material is not very thick, it will not change the chassis geometry very much, if at all. Then I will be epoxying the holes shut, and once hardened, redrill the hols and recountersink to put material back where it's needed. Then be sure to tighten everything securely. This way, the stainless sheet will be what locate and absorb any forces on the chassis. You could attempt to do something similar.

[GoMachV]

^ what he said! That's basically what traxxas did when they broke the plastic chassis, just added a replaceable fiberglass plate sandwiched. Should work great

[slotcarrod]

I have an old runner that is like this, but when you tighten down the counter sunk screws it all lines up perfect back to normal. So just keep your screws tight!

Yes this problem happens when you run for very long times with loose chassis screws.