Interesting Rear Hub Nuts

[LotusJoe]

I'm curious if anyone has used this type of nut?



I saw this on FaceBook:
"For Sale: New Lotus Europa rear hub nuts (guaranteed not to come loose).

I have produced these hub nuts for the Hillman Imp range of vehicles due to the tendency for the standard rear hub nut / lock washer to work loose. As the Europa used the same outer rear splined stub axle & lock nut arrangement I thought I would offer the same items on here.

The nut comprises of three pieces, each with interlocking cams which are joined together to form one assembly. When subjected to shock and vibration the interlocking cams of the nut rise against each other further locking the assembly, eliminating the possibility of the nut ever coming loose. The nut is installed in the same way as a standard nut, using the recommended torque.

This type of nut eliminates the need for the standard lock washer as the nut assembly incorporates its own captive washer.

The nuts are £42 per pair including UK tracked postage, overseas shipping is welcome please contact me for costs.

Thanks for looking."

[jbcollier]

Interesting.  Eliminating the (often-too-soft) tab washer would be an good idea.

[EuropaTC]

Is the problem that the nut actually unscrews or that the central spacer on the earlier designs doesn't have a large enough support area and thus frets if the tube isn't hard enough ?

I thought the main problem was losing clamping force because the assembly (central spacer, outer spacer and the tab lock washer) has worn and lost overall width, not that the tab washer didn't hold the nut securely.  Personally I've never had a problem with the tab washer allowing the nut to unscrew, but I can see the problem with a soft washer/spacer allowing play to develop.

Having said that. it is an ingenious bit of kit and reasonably priced for a custom, low volume manufacture. I did a quick check at SJS and they sell the hub nut for £6.84 and the washer for £11.80. (unless the latter is a misprint ?)   For a UK buyer, add that lot up, slap on tax/postage and that custom nut is probably cheaper.  And if it's proven reliable in service, it looks a neater option. 

Brian

[Bodzer]

Thanks for sharing that Jeff. Very interesting. Rather like a Nord Lock washer. Same principle of locking cams. I can’t remember the thread size at the moment but this looks like it’ll do the job: https://www.nord-lock.com/shop/washers/stainless-steel254smo/nl3.4spss/

[jbcollier]

All good questions Mr TC.  You’re right, the nut doesn’t actually back off.

The first issue is the plain steel spacers.  They actually could be just exhaust pipe.  Replacing them with hardened spacers is a great idea.  I wish the replacement, hardened spacers available were thicker.  It would be a big help.

The second issue is the folding tab, lock washer.  They are soft and can distort/fret leaving less/no tension on the nut.

The third issue is that the spindle/axle is not made of sufficiently strong material.  They didn’t actually use high-grade butter, though it seems like it at times.  Any looseness and the splines on the axle and hub will both wear away quickly.

The fourth issue is the design of the axle/ spindle itself.  The threaded section ends with no rounded, stress-relieving to the rest of the axle.  This is a natural fracture point.  Any over-tightening or stress from a loose hub and it may fracture.

Finally, the upright itself is soft and very thin.  If you drive out the bearings crooked, commonly done, the bores wear/fret until they no longer hold the bearings properly.  This leads to movement, play, stress and failure.

What to do?

Careful examination and selection of the components is very important.  Use only hardened spacers.  The hub should be “snug” on the splines.  Any play and you need to replace BOTH.  The bearings are a press fit into the hub bores.  That means tight!  If they go in easily, you need to have the uprights repaired with steel sleeves shrunk into place. Finally, if all of the above is good, use loctite designed for splines on the axle and hub.  This is extremely important otherwise you will get movement and wear.

The lock tab washer?  AFAIK, there aren’t any correct ones out there.  It needs to be designed so the nut only bears on hardened material.  Unfortunately even the good ones have the nut working through the soft tab part of the washer.  If everything else is up to snuff, the lock tab washer will be ok.  But, if anything else is marginal, it will fail as well.

It is what it is.  Perfectly fine for a 50 hp Imp.  Quite a bit less so for the more powerful Europa with its reduced spline contact.

[SwiftDB4]

Another beef I have with the stub axle is that the outer bearing rides some on splines, not fully on a journal. This may have been an Imp design, but couldn't Lotus have cut the splines shorter? Some of my stub axles have worn out in just this area of the splines.