Tank bolts shaking loose

[danno]

Have got the new longer bolts in now. Took a while getting the tank off and even longer putting it back on.
Patience and a lot of rag helps.
Cleaned up the holes with 5/16 BSF tap and now there's plenty of thread for the bolts to grip.
Even using coppaslip I still find there's resistance from the rubber mounts on the bolts when doing them
up.
I'm not sure if they've pulled right up to the bolt shoulder but I don't want to risk over tightening and damaging the thread.
Hope they stay put now!
Thanks for the help.

 

[bmetcalf]

You reminded me that I have used silicone spray lubricant on the bolts to help them slip against the rubber.

 

[chankly bore]

You MUST do them up tight against the thread or they WILL strip out or loosen.Do some careful measurement to ensure this.

 

[danno]

You MUST do them up tight against the thread or they WILL strip out or loosen.Do some careful measurement to ensure this.

Yep will do. The bolt shank length is the same size as the rubber mounts so they shouldn't compress much before the bolt tightens.

 

[1660bob]

Length may be same Danno, but I think from memory the bolt shoulder may enter a small counterbore in the headstock and therefore go in further than you expect-and the thickness of the washer equates to a lot of compression on the rubber also.Take a close look at the bolts,alone in the headstock,are they free to go in right up to the shoulder whereupon they should come to more or less a dead stop when nipped up?-thats the all important bit to stop loosening. If all good then measure the distance between the headstock face and the underside of the washer when the bolts are nipped up. Compare this fitted measurement with a free rubber length to see how much the difference and therefore how much rubber compression there will be - personally, I see no reason to compress the rubber more than half a turn of the bolt at the most-that compresses the rubber just a little-squashing the rubber achieves nothing but stress and distortion.If too much, you could, like me undercut the bolt head on a lathe -effectively lengthening the bolt slightly, or I suppose you could remove a little rubber from the OUTER end somehow to avoid the squash.Bob.

 

[danno]

Thanks.
Yes now I think of it, there is a small counterbore there.
Once I'd cleaned up the holes I was able to screw in the bolts by hand and then use a ratchet spanner for the last bit.
It didn't seem to come to a dead stop, more of a gradual tightening which I thought was ok. I didn't measure the distance as you mention but I could re-check plus I need the practice getting the tank off

The rubbers may be compressing a little too much. It all makes a bit of a racket when turning the bolts through the
rubber mounts as it resonates through the whole tank!
It's all back together now and while tapping the holes was straight forward enough, it wasn't easy getting the tank on
due to the cables near the tank mounts. Should be easier 2nd time.

 

[clevtrev]

Length may be same Danno, but I think from memory the bolt shoulder may enter a small counterbore in the headstock and therefore go in further than you expect-and the thickness of the washer equates to a lot of compression on the rubber also.Take a close look at the bolts,alone in the headstock,are they free to go in right up to the shoulder whereupon they should come to more or less a dead stop when nipped up?-thats the all important bit to stop loosening. If all good then measure the distance between the headstock face and the underside of the washer when the bolts are nipped up. Compare this fitted measurement with a free rubber length to see how much the difference and therefore how much rubber compression there will be - personally, I see no reason to compress the rubber more than half a turn of the bolt at the most-that compresses the rubber just a little-squashing the rubber achieves nothing but stress and distortion.If too much, you could, like me undercut the bolt head on a lathe -effectively lengthening the bolt slightly, or I suppose you could remove a little rubber from the OUTER end somehow to avoid the squash.Bob.

Your memory is up the swannee. The face should be perfectly flat for the shoulder to tighten against. Helicoil repairs are a no/no. The OD of the helicoil is greater than the 3/8" diameter of the shoulder bolt.

 

[1660bob]

Well Trev, I went to check, -nope, memory is good-check out my headstock.Definate countebore, not damage-photo`d both sides for good measure then a piccy of the bolt in with shoulder just about to enter said counterbore and lastly fully home.Counterbores are about 1-1,25mm deep and look "proper"-perhaps my headstock has been "got at" but it all looks kosher, Bob.