Lotus Elan

+2 Loose wheels

PostPost by: mac5777 » Mon Aug 24, 2015 6:08 pm

Mike, a few of the Cobra hubs are longer than a normal hub's length and protrude out past a fully tighten spinner. It pushes my tool off of its power portion and does not work. The Halibrand spinners have a hollow center, much like the early 26R spinners. As a solution, the Cobra guys have ground off the excess so the knockoff tool works.
That could be a solution if a spinner is bottoming out before the proper torque is achieved. That could correct the wheel's center portion being bent in, out of shape, from over tightening or whatever. Just an idea.
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PostPost by: snowyelan » Mon Aug 24, 2015 7:52 pm

Bit of plasticine in the bottom of the spinners, torque, undo and measure plasticine thickness?
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PostPost by: Washer » Mon Aug 24, 2015 9:55 pm

Hi,

Just spent some time measuring the dimensions of my hubs and spinners.

Interestingly, the distance from the hub flange, where the wheels locate, to the end of the hub threads was 46mm at the rear compared to 49mm at the front. This difference would possibly account for a wheel loose at the front being rigid at the rear.

But of more interest is that although the internal depth of all my spinners are the same (~32mm) there are two different types of spinner fitted to each side. On one type(A) of spinner the ends of the threads are undercut for a distance of ~4mm before the end of the spinner bore. On the other type (B) of spinner the threads extend into the bore the same distance but are not undercut at the end. The practical result of this difference is that the Type A spinner can screw a further 4mm onto the hub than a type B spinner without bottoming.
An extra 4mm could make quite a difference to the wheel clamping pressure achieved, if my sums are correct (unlikely :? ) this is over a ? turn of the spinner.

I cannot find any mention of 2 types of 3 eared spinners from the factory in the archives, does that mean that one of the type of spinners is likely to be from an after-market source? Do any forum members know which spinner type is the standard?
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PostPost by: rgh0 » Tue Aug 25, 2015 1:14 pm

I guess you really need to determine how much deformation has occurred in the wheel centre that is allowing the spinner to bottom out on the thread before the wheel is clamped securely to the hub.

Once you know that it should be possible to get your wheels pressed back into the correct shape.

The starting point would be to compare the dimensions of all your wheels including the spare as to which has been distorted the least and is furthest away from bottoming the spinner as this one should be close to original dimension.

I would also be checking the wheels carefully for cracks as the bending you are seeing that is probably due to over tightening and correcting work required may have induced some cracks.

cheers
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PostPost by: wotsisname » Tue Aug 25, 2015 1:22 pm

snowyelan wrote:Bit of plasticine in the bottom of the spinners, torque, undo and measure plasticine thickness?


I also thought this.
I also seemed to remember a stuff called plastiguage (I think this is right) that you can put in the crank bearing to measure tolerance during an engine build, ...
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PostPost by: Quart Meg Miles » Tue Aug 25, 2015 10:33 pm

While not a proper engineering solution you could make a sheet metal shim to space the wheel out 1/16". I recently did that for a bolt-on wheel where the tapers for the nuts were worn deep, allowing the nuts to bottom on the rear hub and leaving the wheel loose. I undercut the nuts a bit but was worried I was losing threads. The hub was a replacement made by St Wilkins and I haven't had the chance to measure its thickness compared to the original on the other side.

Only recently I realised that the correct torque for the original bolt-ons was around 25 ft-lb and I had been using more than 50. No wonder my standard 12-sided socket ruined the nuts by rounding their tips and deepened the tapers in the wheels.
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PostPost by: Washer » Sat Aug 29, 2015 11:32 pm

Hi, many thanks for the replies.

Eventually found time to complete some more measurements of the wheels. From the wheel face which sits on the hub flange to the highest point of the wheel centre there is a range of 1.82mm (29.74mm, 28.84mm, 28.80mm, 27.92mm). Note that this is not measured from where the spinner seats on the wheel as it proved difficult to obtain a consistent measurement. However, it was clear that on the narrowest wheel the witness marks from the spinner were visibly closer to the edge of the centre circle (~3.5mm) than those on the other wheels (~5.5mm).

So to sum up: fitting my narrowest wheel on the longest hub (front) together with the spinner type that does not have undercut threads will not allow adequate wheel clamping pressure to be achieved. Swapping the narrow wheel to the back or swapping the spinner type will allow wheel clamping pressure to be ?apparently tight?.

I have judged the tightness by hammering the spinner through approximately 72 degrees after all wheel play is taken up. This angle is the distance that the drive pegs are apart. To me this feels plenty tight enough but I would be very interested to know what angle that 180-200lbft of torque turns an export nut type spinner through?

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