Air box fixings

[Revvit]

I'm in the process of refurbishing my air boxes, have removed the old back plates in readiness for painting prior to fitting the new carbon fibre ones and have noticed that someone has PU'd nuts inside to take the bolts which hold the box to the bracket.

Can someone please confirm if the original fixing was an aluminium rivnut and what size.

Thanks

Mark

[ukkid35]

Whatever you do, bear in mind that the airbox is only a moment away from destroying your engine. A couple of years ago there was a Cerb that suffered total engine failure when a nut from an airbox ended up in the combustion chamber causing one of the liners to split.

[Revvit]

ukkid35 said:

Whatever you do, bear in mind that the airbox is only a moment away from destroying your engine. A couple of years ago there was a Cerb that suffered total engine failure when a nut from an airbox ended up in the combustion chamber causing one of the liners to split.

Paul, thanks for that, now I'm completely bricking it.

I think possibly the best way of dealing with this is to reverse the fixing detail by tack welding a bolt to a reasonably sized washer, feeding it through from the inside (epoxied in place) prior to fixing the new back plates, then another washer and nut to sandwich the fixing either side of the air box wall. The bolt can then pass through the bracket.

Any thoughts? It's a bit belt and braces, but rather that than a pile of scrap metal.

[tofts]

the way I have done it before, is tack a bolt to a small piece of stainless plate about 1" long or so, then drill a hole the other side of the plate and rivet that to the airbox/item in question. Means that the damn thing can never turn and the rivet is a permanent fixture, if the rivet does work loose, it fall off on the outside of the airbox

J

[Revvit]

But then again, if I were to use a rivnut, if it were to loosen or pull through the air box wall it's still on the end of the bolt which isn't going anywhere?

The only doomsday scenario I can imagine would be if the rivnut pushed through the air box wall and worked its way off the bolt.

I wonder if you can get nylock rivnuts.

I'm beginning to over-think this

[Jabbah]

ukkid35 said:

Whatever you do, bear in mind that the airbox is only a moment away from destroying your engine. A couple of years ago there was a Cerb that suffered total engine failure when a nut from an airbox ended up in the combustion chamber causing one of the liners to split.

Well, it was never confirmed that was the actual cause but definitely a strong possibility of an errant nut. Happy to say that it is still going strong after having a new piston, liner and heads welded and now has another 15k miles on her since then.

Edited by Jabbah on Thursday 5th May 12:54

[tofts]

Never been keen on riv nuts, over time they allways start to turn in the medium you mount them in! You are right, and the chances of it working through the airbox are slim, you just may end up with a fastner that just keeps on turning. If you must use them, buy the stainless ones!

[Revvit]

tofts said:

Never been keen on riv nuts, over time they allways start to turn in the medium you mount them in! You are right, and the chances of it working through the airbox are slim, you just may end up with a fastner that just keeps on turning. If you must use them, buy the stainless ones!

I've just purchased a Memfast rivnut kit,so will give it a go with stainless rivnuts as you suggest. I've also got to bond a pair of M4 composite fasteners to the back of my new carbon dash (to take the PCB board)using vudu methacrylate which is strong enough to bond steel to steel, so I might add a touch of that to the rivnuts at the same time.

And if that doesn't work I don't know what will???

A couple of bungee straps maybe

[viperbluecerb]

Just had to rivnut mine. The way it is mounted it shouldn't find it's way into the airbox and instead would pull though like the last one did. The way it is fastened means that the face of the nut pulls tight against the bracket so even if it pulls through it should remain firmly attached to the bolt.

I also have home made aluminium back plates in which the rivnut at the very back is attached.

[ukkid35]

There are also the crankcase breather fittings that can come loose...

I found a small nut in one of the air tubes once, no idea where it came from, very scary.

[Revvit]

What size are the original rivnuts?

M8?

[Revvit]

Revvit said:

What size are the original rivnuts?

M8?

A previous owner has removed the original fixings.

Judging by the size of the holes the front pair on each air box are approx 11mm dia which equates to an M8 rivnut and the single rear is smaller, maybe an M6?

At the end of the day I can install whatever fits, but my OCD wants it to be as per original

Can anyone confirm M8 front and M6 rear? Or something else.

Thanks

[Revvit]

By accident I've just seen the link posted by Mr Cerbera on the wiper motor thread.

M4 capped bolts it is then!

[pmessling]

I too hate riv nuts.

Unfortunately stainless steel ones are a pig to use with a normal hand tool.

[Revvit]

pmessling said:

I too hate riv nuts.

Unfortunately stainless steel ones are a pig to use with a normal hand tool.

That's why I've bought one of these

http://memfast.co.uk/shop/Vprod1.asp?cat=225800463...