Community Forums

Wobster · 10-11-2015, 03:21 PM

Well, my step motor (Kwikee) sheared all 4 of its mounting bolts a week or so ago while I had just arrived for a rally. We made do with a short ladder and once home I have managed to remove all 4 studs using easy-outs (3 of which actually came out fairly easily, the 4th, well that lived up to the "not so easy" easy out reputation, but I did succeed). I cleaned out the bolt holes with a tap (they are 1/4-20 bolts) and I am now ready to replace them. Any recommendations for Bolt type. I had considered using a grade 8 bolt as they are stronger/hardened, but the thought of those shearing and needing to drill out a hardened bolt is not making me happy...but if it never broke again of course that would be Ok...
Second question. The motor housing is aluminum, and of course the bolts will be steel...any thoughts on something to coat the bolt with to resist the inevitable electrolytic corrosion?
Thanks!

gruelens · 10-11-2015, 04:51 PM

I would install Grade 8 bolts. Greater loading is what they are designed for. Possibly something is amiss, in that four Grade 5 bolts sheered off. Was the rig exposed to salt or marine climate causing bolts to decay?

Grade 5 vs Grade 8 Fasteners - TineLok

mhbell · 10-11-2015, 05:11 PM

I agree with Gruelens. Something had to cause them to shear off. 1/4 by 20 bolts does not seem big enough for the steps. My Kwikee steps on a older motor home had 3/8 bolts and I just repaired the steps on my present motor home because the welds where rusted and the steps were sagging. I drilled 1/2 inch holes and use Grade 5 1/2 inch bolts. They don't sag now. If possible I would drill bigger holes and replace the 1/4 inch bolts with bigger ones and use Grade 5 or 8.
Mel

Wobster · 10-11-2015, 07:13 PM

Thanks guys. The thread/bolt size is determined by the threading in the motor housing so I can't fix that. These are just the bolts that mount the motor, the steps are still in place (zip tied up so they won't drag). I went to hardware store and the only things they had that fit were Grade 8 so that's what I bought. I know they are stronger (hardened) but I also thought they were more brittle to shear stress... I actually think the ones I removed were unmarked heads so possibly not even grade 5 (the previous owner did some work on the steps so maybe replaced with generic bolts). Hoping these last as drilling out Grade 8 bolts seems like it will be near impossible!

speed racer · 10-12-2015, 05:36 AM

Are we talking about the bolts that hold the steps to the MH , the bolts that hold the gear box to the step or the bolts that hold the motor to the gear box?

I only use stainless steal bolts and nuts on the outside of the MH.

TQ60 · 10-12-2015, 07:45 AM

Unmarked are grade 2 or less.

They came loose then movement allowed them to stress and break at a thread as that part is stresses and smaller.

Grade 8 will be fine and use a drop of oil in threads with lock washer.

Better would be lock tight but not sure which color as yiu just want a mild hold and not a welded bond.

Others here can provide that info or the counter person at a good Napa store maybe.