How to secure a drive shaft nut?

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dovekie

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The output shaft of my gearbox is splined. Onto this slides a drive plate, which is secured by a nut on end of the output shaft. The nut has come off - fortunately with no adverse consequences. I think that the repeated rotational impulse when engaging reverse has caused this. The whole lot (engine, gearbox, flex' coupling, prop shaft and prop are newish - 40 hrs running time). The prop is a self-pitching Autoprop, which does give quite a clunk when gear is engaged.

Nothing is damaged. The splines and thread are unmarked. The drive plate slides smoothly back on and the nut does up easily, and doesn't slip with the torque I can apply using a 36mm socket and a 20inch bar.

I am concerned that it may work loose again. Any suggestions on how to secure it gratefully received.

Hopefully - pictures below. Apologies if I fail at this.
 
OEM specified as Loctite 271

High temperature, high strength for heavy duty applications

Designed for larger fasteners 3/8" to 1" (9.5mm to 25mm)

Locks studs, bushings and large fasteners against vibration loosening

Strengthens slip and light press fits

Removable with heat and hand tools
 
Is the centre of the coupling solid? If it is then you could work out the distance between the end of the output shaft and the coupling. You could then add washer under the nut so that it was pressed against the coupling when it was all done up. The nut could not then work off.

Failing that then good old Locktite.
 
Can you see a small indent or keyway on the threaded shaft?

With Yanmar (Hurth) gearboxes the recommendation is to use a centrepunch or screwdriver and hammer to locally distort the thread of the nut into the indent of the shaft once torqued up tight.

The workshop manual calls it "Calking''and says of course remember it might be lefthand thread!
 
Hi . Your local friendly engineer here.

Nothing personal but DO NOT DO what he says ^^^^ its obvious he's only trying to help so thank him for that etc. but at the end of the day i dont not care what any manual says, probably bodgerneers themselves whomever wrote that tripe.:D ( you should never ever have to damage a thread to do a nut uptight and make it stick, british engineering rocks by the way)

go to your local engineering suppliers and ask for a product called "Loctite ThreadLoc" it comes in a dark red bottle. you get different grades, some are very brittle some are flexible, ask for the middle of the road stuff, that should suit your needs fine, make sure you give both male and female threads a really good scrub with thinners and allow to dry, then apply your threadloc then put your nut into position.
 
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Keyway on a threaded shaft? Errrr, dont think so. The coupling runs on splines. Loctite , as suggested above, and find out what the correct torque should be from the makers. Calking or Staking the nut to shaft would lead to expensive repairs long term.
 
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Re Blueboatman's reply- you are thinking of a Stake Nut (google for one), but thats not what the OP has.

OP- use either loctite, or make a locking tab for the nut, one tang to engage in the spline, and one flat to tun up against the flat of the nut.
Personally, I'd use Locite!
 
oldharry said:
Keyway on a threaded shaft? Errrr, dont think so. .
Click to expand...


It is not so unusual to find a groove machined along a threaded shaft when an internal tab washer is used to lock the nut. The central hole in the washer has a tab which locates in the groove machined in the shaft and the outer edges or tabs of the washer are turned up against the flats of the nut, locking it in place.

http://forums.lr4x4.com/uploads/1155214591/med_gallery_2_148_688605.jpg

http://forums.lr4x4.com/uploads/1155276206/med_gallery_2_148_904564.jpg

http://images.google.co.uk/imgres?i...el=s&rls=org.mozilla:en-GB:official&sa=G&um=1

However that does not apply in Dovekie's case.

I can't see it too clearly in the photos but that special nut looks as if it might be some kind of self-locking type [similar idea to Aerolock nuts].
 
Last edited by a moderator:
parsifal said:
That is not so unusual and is found where an internal tab washer is used to lock the nut. The central hole in the washer has a tab which locates in the groove machined in the shaft and the outer edges or tabs of the washer are turned up against the flats of the nut, locking it in place.

http://forums.lr4x4.com/uploads/1155214591/med_gallery_2_148_688605.jpg

http://forums.lr4x4.com/uploads/1155276206/med_gallery_2_148_904564.jpg

http://images.google.co.uk/imgres?i...el=s&rls=org.mozilla:en-GB:official&sa=G&um=1
Click to expand...

we know that, but its obvious from the OP's predicament he does not have that washer, so he either gets one to fit or uses the easier option of Loctite Threadloc, :cool:
It matters not which he chooses, as both are good and will solve his problem.
 
JasonClark said:
Hi . Your local friendly engineer here...

Nothing personal but DO NOT DO what he says...

... apply your threadloc then put your nut into position.
Click to expand...

-------------------------------------------------
Got to say that I was surprised to read it, seeming a tad crude way to treat a relatively precision made gearbox....

So I am glad to have posted and even more so to be professionally corrected. Good this forum innit !
 
The correct Loctite to use is 243. You should be able to source it at your local engineers suppliers. It comes in diffferent sized bottles ~ you need the one that's the size of your wife's nail varnish bottle (that'll still be £15 squids sir) but you'll have enough to last a lifetime on your type of application. Make sure the thread is clean ~ apply the 243 and torque up to manufacturer's recommendations ~ leave for 4 hours before you use the engine.

243 can be split using minimal heat if required.

As some extra help try your yellow pages under Engineers Supplys or goggle "Cromwell Tools".

Peter
Boatman and engineer.
 
Ignoring all the nasty fighting here.......


It strikes me that since the only thing that was capable of cracking the nut loose in the first place was the spider on the splined shaft. If the splines on the shaft and spider are in good nick there should be as good as bu$$er all backlash between the spider and the shaft. If that was the case then the spider could not shake the nut loose. I'd check the condition of that spider coupling.

Looking at the problem you could get a tab washer made up, shaped like a frying pan. Hole in the centre to fit around the shaft and with a tab that could be folded up onto a flat of the nut. The 'handle' of the washer could then be extended to interfere with one of the legs of the spider or perhaps even have one of the coupling bolts passed through it.

That nut really only keeps the coupling seated. Perhaps the nut just was never tightened when it was assembled. Maybe it just needs a new nut. Maybe a reference in the manual gives a recommended torque loading for tightening up.
 
TheBoatman said:
The correct Loctite to use is 243. You should be able to source it at your local engineers suppliers. It comes in diffferent sized bottles ~ you need the one that's the size of your wife's nail varnish bottle (that'll still be £15 squids sir) but you'll have enough to last a lifetime on your type of application. Make sure the thread is clean ~ apply the 243 and torque up to manufacturer's recommendations ~ leave for 4 hours before you use the engine.

243 can be split using minimal heat if required.

As some extra help try your yellow pages under Engineers Supplys or goggle "Cromwell Tools".

Peter
Boatman and engineer.
Click to expand...

Well thats two engineers that say use Loctite, anymore ? :p
 
parsifal said:
Looks like its a self-locking nut and therefore should not be re-used.

Suggest you buy a new one [and a torque wrench]
Click to expand...

Dovekie, Does your first photo show the nut tightened fully? If so, I'm curious as to why there is a collar on the nut. At first glance, I agree it looks to be some sort of self-locking design, but there's nothing like enough thread protruding for it to be certain to work! Are you certain the hub is fully home?

If so, as has been said, I guess some sort of thread locking compound would seem to be the best solution. As has also been said, it's worth getting a grade that can be undone with mild heating (say just over 100 C). It's highly unlikely ever to get that hot in use but you'll stand half a chance of undoing it without ruining the seals if you ever need to.

I'm slightly concerned that you say the hub slides easily on to the splines. I'd expect to maybe have to tap it home with a hide mallet - especially on two new components. It doesn't take much backlash to get these nuts undone!

I also agree that the suggestion that it wasn't torqued up correctly should not be overlooked - you might be trying to solve a problem that's not there!

Finally, just for the sake of joining the "bun fight", Blueboatamn's suggestion of a small keyway in the end of the shaft and a stake nut:

http://www.philidasfasteners.co.uk/prod_stake.htm

seems perfectly reasonable to me, as long as you can still get full thread engagement in the nut (and there doesn't look to be much "spare" shaft sticking out)! It's a very common solution and there are (literally) millions of front wheel drive cars running round with just such a method of keeping their front hub nuts on the ends of their driveshafts!
 
nimbusgb said:
Ignoring all the nasty fighting here.......


It strikes me that since the only thing that was capable of cracking the nut loose in the first place was the spider on the splined shaft. If the splines on the shaft and spider are in good nick there should be as good as bu$$er all backlash between the spider and the shaft. If that was the case then the spider could not shake the nut loose. I'd check the condition of that spider coupling.

.
Click to expand...

OR CONVERSELY, IT WASNT DONE UP TIGHT IN THE FIRST PLACE. mUCH MORE LIKELY ON A NEW ENGINE.

AM ENVIOUS OF THE CLEAN ENGINE AND SHINY BILGE! :)

SORRY FOR THE CAPS - UNINTENTIONAL.
 
Well aware of the unhappy practice of staking car drive shaft hub nuts - and arent they a pig to do after an overenthusiastic garage hand has done them! My point was simply, unless the maker specifies doing it to lock the nut - dont.

As to the keyway, clearly a threaded shaft will not have a locating key in it as such. The OP's pics show it could never have been fitted with a keyed locking washer. The special nut pretty well fills the recess in the coupling with its load spreading flange, and the nut is deeply recessed in the flange so it would be difficult or impossible to use a keyed staking washer. The nut flange would need a 'flat' in it anyway for a staked washer.

Firstly, we need to know the specified torque for this nut - which I think will be quite high. Almost certainly, given the low engine hours quoted, it had not been properly torqued at assembly. Secondly, another vote for Loctite to ensure it stays put this time.
 
Drive shaft nut

Well first, thank you all - just fantastic to be able to gather so many points of view.

To try and answer the questions:
MoodySabre: Can I fit a washer that holds the nut against the centre of the coupling? I would need to go back to the boat to check but I hesitate to do this. It is a flexible coupling, or at least it has elements that are plastic and give slightly on tightening their bolts, so there may be some movement, and wear. Perhaps more importantly, the nut is only 16mm thick, i.e. 16mm of thread engaged - and (Avocet) the first photo does show the nut fully home. So fitting washers under the nut will start to reduce the proportion of thread engaged.

Loctite sounds like the way to start, and thanks for the info on which sort (TheBoatman/ksutton). I had wondered if the nut could ever be removed once "loctited" but I did not know that heat freed it up.

Blueboatman: there is no keyway or indent on the threaded shaft - looked pretty carefully, being concerned about damage.

NorthUp: I hadn't thought of a locking tab. The nut seats in the hollow of the drive flange with little gap to run a tab through.

parsifal: It certainly isn't just a standard nut, being thinner and only partly hexagonal section (collared?) for starters. I shall post the only (slightly) better picture I took of the nut. But it has no splits, is not "aero", and has no inserts etc.

nimbusgb/Avocet/jason -and the arguenauts : yes, why did it come undone? The drive plate does indeed need a few light taps with a mallet to send it home. I am presuming it is home, as the unpainted bit of the plate disappears. And I too can't see how the drive plate could apply torque to the nut - given that it is so solidly splined to it's shaft. I guess the suggestion that it was never tightened in the first place may be right - presumably a loose nut could work looser with the inertial torque of engaging gear. It hasn't moved since I first fixed it up tight, probably 20 gear changes ago.

BTW the engine is a Beta 38HP, and the gearbox is a "technodrive TMC 60E" which came standard with it. he prop is an autoprop which does give a fair clunk on engaging gear, much more than our previous three blaed fixed prop did.

Many thanks again
 
dovekie said:
the gearbox is a "technodrive TMC 60E"
Click to expand...

Manual (pdf file).

Nothing about staking, loctite or needing a new nut every time (indeed one needs to torque this nut up and remove it again as part of the gearbox set-up).

Torque setting is 16kgf m which I've converted as ~116 ft lbs.

FWIW I would do it up again to that setting.

HTH

Andy
 
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