Lotus Elan

small or large front upright?

PostPost by: billwill » Sat Sep 28, 2019 12:44 pm

vxah wrote:Knock on uses the big stub which needs a bigger hole in the upright.
Bolt on uses a smaller stub so the upright has a smaller hole for it to fit into.


I know that but alas your message above with the measurements is ambiguous unless big upright means the same as big stub and small upright means the same as small stub.

Sorry to be so fussy, but there was talk elsewhere about different sized uprights for higher performance, viz Spitfire versus GT6 which has confused the issue. There seems to be four possible combinations not just two.
Bill Williams

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PostPost by: vxah » Sat Sep 28, 2019 2:26 pm

Yes there are 4 types of uprights that I know of. Later Spitfire and gt6 changed the steering arm design so that the rear mounting bolt was not used and instead the steering arm went under the stub axle fixing nut and I think the front mounting bolt location was changed slightly.
So, there is a late and early stub (longer fixing thread on the late) and a late and early upright to match.. both of these in two sizes but afaik the Elan only uses the early type.
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PostPost by: billwill » Sat Sep 28, 2019 9:43 pm

I measured my two spare uprights. They do have the pointy blip pictured above.
The first has the large size of the sub axle hole as 25.9 mm and the small hole as 19.7 mm and the distance across the upright is 50.9 mm

The second sample has 27.33 mm large hole, 21.14 mm small hole and 50.85 mm across the flats.

Converting to inches I calculate this as a taper of 0.244/2.004 hence 0.127564 inches per inch for the first one and 0.244/2.002 hence 0.121878 for the second one.

That's for both ways from the axis so the taper along the axis is half that 0.0609 so the angle of the taper is arc-tan of that figure which is 3.487 degrees from the axis or 6.974 degrees for the full taper.

Does this sound like the figure for a bolt-on stub axle or for a knock-on stub axle, which?
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PostPost by: vxah » Sat Sep 28, 2019 10:26 pm

Sounds like you have one knock on upright and one bolt on upright in your spares stash?
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