Any ideas to stop these bolts coming undone?

[Trevorleach]

Scania truck 5 piece cat walk, each piece held on with 6 M10 countersunk allen headed bolts.
Plastic washer under the taper part of the bolt to stop fretting on the alloy catwalk, pretty much daily these are coming loose, obviously due to chassis flex.
All bolts screw into mild steel framework that is bolted to truck chassis, 5mm thick rubber pads with a hole in sit between chequer plate and steel framework.
Noticed today he has tightened them so many times the female thread has worn out on one of the mounts.
Have tried silicone sealant then loctite, both failed to stop the fasteners coming loose.

 

[8ob]

It needs a redesign, the bolts cant be tightened properly because of the rubber sandwich. It could really do with the male/female rubber mounts screwed down to the chassis and them screw down the plate to the mount.

This sort of thing

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[Rannsachair]

worth trying tab washers, like: https://simplybearings.co.uk/shop/p...aeij7_jq0-nt8fKrHjKpDzpyhW_pFEfMaAmF0EALw_wcB

 

[Trevorleach]

It needs a redesign, the bolts cant be tightened properly because of the rubber sandwich. It could really do with the male/female rubber mounts screwed down to the chassis and them screw down the plate to the mount.

This sort of thing

View attachment 510732​

Sadly not possible as the whole thing has just been rebuilt/new paint/exhaust system, the works basically, cab to chequer plate clearance is quite tight so any height increase would cause difficulties, plus driver would bitch if it did not look cool!

 

[Ace Paul]

rivnut, long bolt and nuts on back
Drill hole, in thread stainless wire.

As m10 is small chunk out counter sink and drill self tapper screw option

 

[8ob]

Sadly not possible as the whole thing has just been rebuilt/new paint/exhaust system, the works basically, cab to chequer plate clearance is quite tight so any height increase would cause difficulties, plus driver would bitch if it did not look cool!

The only other thought is to swap out the bolts you have and go with a countersunk shoulder bolt that has just enough shoulder to nip up the rubber and for the shoulder to bottom out on the chassis.

 

[500e]

Dzus fastener

 

[Brad93]

Loctite

 

[Trevorleach]

The only other thought is to swap out the bolts you have and go with a countersunk shoulder bolt that has just enough shoulder to nip up the rubber and for the shoulder to bottom out on the chassis.



View attachment 510733

I like that idea, any idea where to get said bolts from?

 

[Bornfree]

Loctite 638 but you will need a grinder to undo them.

 

[bricol]

I suspect the plastic washers are to keep the stainless steel screw and the aluminium apart in an environment where they will get wet and salty.

I have no idea why you would use silicone as a thread locker - but that is why your loctite failed when used afaterwards. Thoroughly clean the threads out and use one recommended to work with stainless.

Or as has been suggested, a longer screw and simply put a nut on the back to lock it. Nylocs would be even better and probably allow you to simply drill through the worn threads and use them as a clearance hole.

 

[BrokenBiker]

swap the scanny for a volvo and you wont have these issues

had a similar problem on a fleet truck a few years back, that was a scania as well although doubt it made much difference...i ended up wrapping the threads in PTFE tape and never had an issue again, although my bolts werent holding a catwalk on, they were for brackets for various bits of added kit and pipework

 

[Slowcoach]

Is it me or is the hole in the chequer plate not really countersunk, looks like a pretty straight hole to me.

 

[Beanwood]

I like that idea, any idea where to get said bolts from?

You could use cheese or dome head screws and use a sleeve insert cut to the correct length to tighten on to? Or Zoro do shoulder boltsLoads of types.....

 

[Turbo]

Loctite should work, I think the issue is contamination or not giving it time to set.
Thoroughly clean and degrease the holes and the bolts, maybe run a tap through the holes. They have to be very clean plus oil and silicon free. Use blue loctite and let it set overnight.
If that doesn't work try green loctite but be aware that if it sets it requires heat to undo the fastener!

 

[8ob]

Thread lock could cause problems, these walkway plates may need to be removable roadside to get at the components, last thing you need is a dischuffed fitter doing battle with them. @Beanwood' s spacer idea would also work if it was a thickwall spacer or even top hat section spacer, rubber is 5mm so a spacer of a tad under that would do, you could then use the standard c/s crews with those.

Bob

 

[Trevorleach]

Stuck catwalk back on this morning, had to use head torch as it was still dark.
I took a closer look at the tapered holes in the alloy chequer plate, and as mentioned by @Slowcoach above the are quite worn so there is not a lot for the bolt to grip onto, more sort of steer it gently!
I will have to have a think about how to go about this, main thing is it is ready for Monday morning.

 

[Trevorleach]

Thread lock could cause problems, these walkway plates may need to be removable roadside to get at the components, last thing you need is a dischuffed fitter doing battle with them. @Beanwood' s spacer idea would also work if it was a thickwall spacer or even top hat section spacer, rubber is 5mm so a spacer of a tad under that would do, you could then use the standard c/s crews with those.

Bob

Most of our catwalks are sectional, one truck has a huge one piece affair, I know how to get it off with 2/3 other blokes lifting and I still hate it, gawd knows what another fitter would think of it!

 

[awemawson]

Check crankshaft balancer. Something is vibrating far too much.

 

[Bravheart]

If threads a bit worn try new studs.

Or give the threads a bash first