Engine Mounting Nut Vibrating Loose??

[Richard10002]

Moody 44, Volvo MD22L.

The forward starboard side engine mounting nut keeps vibrating loose, no matter how hard i tighten it, (which may not be very tight as it's a bit hard to get at.

Any suggestions as to how tight it needs to be, how to get at it to get some power on it, and how to stop it vibrating loose again.

I have some Wurth sabesto Frenador, (bought in Portugal), which is a medium resistance locking adhesive for bolts or whatever, if that helps.

Cheers

Richard

 

[Poignard]

If you put a lockwasher under it and tighten it properly it should not need any adhesive.

To tighten it in an awkward place there are various socket set accessories that might help, e.g. universal joints, extensions, crow's foot spanners. Or you may have to modify a spanner. Make sure that your spanner or socket is in good condition and fits the nut snugly.

Adhesive locking compounds are intended to prevent fasteners vibrating loose and to seal the threads, they do not compensate for a fastener not being properly tightened in the first place, i.e. they don't increase the tension in a bolt. My engine holding down bolts never come loose and have no locking compound on them. If you want to use one, make sure the threads are clean and degreased with a solvent before applying it.

 

[Talbot]

I have always found that spilling a bit of sikaflex onto a bolt makes the nut impossible to remove! /forums/images/graemlins/blush.gif

 

[elton]

There might be a torque setting specified for it (N/M, Kg/M or ft/lbs. Tightening it to the correct torgue will strech the bolt within the elastic limit so it won't need locking washers or loctite, and it'll never come undone. If you tighten it to much less than the specified torgue it will almost certainly come loose; much more, and it's liable to snap. Otherwise use a locking washer, but don't over tighten it.

 

[Thistle]

Have you thought about using a nyloc (or similar) nut? Remember that, for best effect, these should be replaced each time they are taken off rather than being re-used ... but I guess you are not removing your engine mounting nuts that often!!

 

[alanporter]

Use of a lock washer has been mentioned, don't use one. In fact, never use one for anything of importance. Years ago the SAE (Society of Motor Engineers) did a lot of research on fasteners of all kinds, and their conclusions on lock washers was that they can hide a slightly loose fastener that can result in fatigue failure. Their final advice was to never use them.

 

[Poignard]

Fascinating [and sometimes a bit worrying] what you learn on this forum but, before rushing to discard all the hundreds of lock washers on my yacht engine, cars, machine tools, domestic appliances etc., and without in any way doubting what you say, I'd like to read the report on that research. I would imagine that it quite properly warns against trying to avoid properly tightening a fastening by using a lock washer, but I'd like to be sure.

Do you have a link to it, by any chance? Is that the British SAE you are referring to?

 

[ccscott49]

British SAE, standard american engineers?????

But I agree with a Nyloc nut, or "stiff" nut.
Thread lock would maybe do, but I'd go for the nyloc.

 

[fiveflipflops]

Hi Richard

How long has this nut been vibrating loose? If it has only started since you left Lagos or later why now?

David
Five Flip Flops

 

[Poignard]

[ QUOTE ]
British SAE, standard american engineers?????

[/ QUOTE ]

Society of Automotive Engineers?

Thing is - do we have any British automative engineers any more?

 

[ccscott49]

Different society, obviously, but I thought the institute was motor vehicle engineers. I was an associate member. AMIMVE. Maybe I'm mistaken yet again.

 

[wotayottie]

on my boat Moody used some serated washers - bit difficult to describe but one surface has sharp grooves radiating out from the centre and the other has a sawtooth type surface that mates with the washer below. either way, they are an absolute cow to undo.

failing that, Nyloc doesnt come undone on my Norton Commando and thats a fair test.

 

[Richard10002]

[ QUOTE ]
How long has this nut been vibrating loose? If it has only started since you left Lagos or later why now?

[/ QUOTE ]

Good question.

I dont know how long it's been loose. It could be for a long time, or just recently.

I noticed it when in the loo a couple of days ago, I took off the engine cover for a look, (boring otherwise <g>), and noticed the nut had worked its' way up the thread.

Found a 1in ring spanner today, so was able to give it a real good tighten... which I couldnt with the open ended spanner.

I'll keep an eye on it.

Why now for anything I guess... 13 years of vibration?

 

[Norman_E]

[ QUOTE ]

Thing is - do we have any British automative engineers any more?

[/ QUOTE ]

Yes we do. They build most of the Formula 1 racing cars.

 

[TheBoatman]

Torque settings ~ I've never ever known a boat builder yet to specify torque settings!

As an engineer I've always worked on the premiss that I keep tightening down the engine mounting bolts until the boats headlining starts to deflect ~ then it's tight /forums/images/graemlins/smile.gif

But to answer Richards question ~ put some nut-loc on it.

Peter.

 

[Poignard]

Lots of different opinions, you must now be wondering why you bothered asking!

Why not keep everybody happy. You have four holding down bolts. Fit one with a nylocknut, one with a lock washer, one with Loctite and one with a castellated nut and split pin. /forums/images/graemlins/grin.gif

 

[oldharry]

Anyone who ran (runs) a British made motorbike will be very familiar with this problem: the solution is to replace the bolt. Frequent retightening and overtighteningcauses the threads to wear on both nut and bolt so they no longer grip each other properly. As the thread wears the actual metal to metal contact area reduces, making it easier for the nut to shake loose. You then get a catch 22 situation as it needs to be tightened more and more frequently, compunding the wear problem.

Overtightening the nut in attempt to make it stay put damages the threads even more, stretching them and making things even worse, to the extent that even a new nut does not grip properly.

 

[catseven]

Hi Richard,

Another alternative is to use Nord Lock washers. Before I retired I was problem solving engineering issues for a large UK Agricultural Tractor manufacturer. We used these washers to resolve an ongoing problem with some bolts that sometimes came loose in the field. See their website below.

www.nord-lock.co.uk

The following is an extract from the website but I don't think the illustation has copied.


Products
The NORD-LOCK bolt securing system uses geometry to safely lock bolted joints in the most critical applications.
This unique wedge-locking system offers the following advantages:

Maximum safety
Resists loosening caused by vibration and dynamic loads
Ease of assembly and disassembly
Locking function is not affected by lubrication
Positive locking at low and high preload levels
Controllable preload
Same temperature characteristics as standard bolt/nut
Reusable

Tension makes the bolt self-locking
The key is the difference in angles. Since the cam angle " &#945; " is larger than the thread pitch " &#946; ", the pair of washers expand more than the corresponding pitch of the thread. NORD-LOCK washers positively lock the fastener in a joint which is subjected to extreme vibration or dynamic loads.

Hope this helps.

Catseven