During a casual visit to the forum lotuselan.net, there was a discussion thread re the process of dismantling, re-assembly and re-torquing of the elan rear drive hubs to the stub axles.
The post was intriguing, because of the process, method, and procedure the poster was being advised of how to, lap, fit, assemble, and torque the hub and axle assembly.
The particular lotus guru’s advice to the lotuselan.net poster was to assemble the hub to axle, torque to specs, then drive the car a few miles or KM, then stop and re-torque, this process required at least six repeats, apparently to allow the hub and axle to “settle in”.
A similar process might have been common on veteran/vintage T and A model Fords… But a lotus elan??
The question I am going to ask you here is this – If the tapers of the hub and the axle are a perfect match, and if the time is taken, I mean a lot of time is taken to ensure that the hub and axle have been bedded in (mated) using valve grinding paste to lap and match the final few tenths of a thou to make absolutely sure that the hub flange taper does match the axle taper, and the lapping process is also checked at various intervals by applying a light smear of bearing blue applied in a line along the axle taper length, place the hub on the axle and rotate it 120 deg, then remove and check… the bearing blue will clearly indicate if the two parts match correctly along the length of the taper.
If the match of both tapers is correct, the bearing blue will cover all of the axle and hub taper contact surfaces axially for 120Deg.
Prussian, or bearing blue, is the most accurate indicator of how a bearing or a taper pair match when bedding in, and only a very light smear is all that is required.
Sometimes, when in a hurry to get the job done, there is always the temptation to apply a thick coat of Loktite during assembly in the hope that it will take up the slack in the fit, that may work to a degree, but in the long term, if the tapers do not match, they will eventually work loose, and you are back to square one again.
If the tapers on either hub or axle are badly worn in any way, or they simply don’t match, (Some tapers match at the small end, some at the large end, they must match the entire length) then NO amount of lapping and paste grinding will make them match, badly mismatched hub and shaft tapers may require a regrind or re-machining… but there is a limit to how much correction work can be done….
Might be a better option to replace the badly worn items.
Tapers, when installed correctly have incredibly strong holding power, and will resist turning under pressure, and off course, the elan hub and axle assembly employs a round longitudinal locking key to ensure a positive drive and fit of the parts.
Tapered parts that have an exact fit and match with correct tightening torque applied, will do the majority of the holding power, and to make sure that it is all going to hold together, there should be a light coating of medium strength 609 loctite applied during assembly to be 100% secure.
If high strength loctite 680 is used during assembly, a good amount of heat will need to be applied when the time comes to pull/extract the hub off the axle again in the future.
The power of Loctite:
Cure. Anaerobic. 609 med strength and 680 high strength loctite is designed for the locking and sealing of threaded fasteners which
require normal disassembly with standard hand tools. The product cures when confined in the absence of air between close fitting metal surfaces …
The writer has owned an S2 elan with bolt on wheels for thirty five years, and has never employed the drive and re-torque process explained above in all of that time, despite the fact that the hubs and axles have been dis-assembled and re-assembled several times during that period.
The trick is to have perfectly machined and matched taper with both hub and axle in the first place – the rest as they say, is easy.
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