Lotus Elan

If It ain`t .........TTR Grrrrrrrrrrr

PostPost by: rgh0 » Wed Jan 10, 2018 12:00 pm

Craven wrote:Is it preferable to have the hub slip or the shaft snap under excess design loads, I think the wheel staying with the car a better outcome.


It preferable that you finish the race with the car intact. I have had both things occur. i.e. loose a wheel and alternatively have the shaft spin in the hub as the taper did not stay locked. If the hub and shaft is properly lapped in and locked with the securing nut compression load then it will never move with any conceivable torque loads except maybe Steve Broads drag super Elan he is building. The locating pin helps the hub not spin while tightening the securing nut which may be beneficial to the whole process so i have left it in place. Lotus included the pin originally for a reason which I do not totally understand and I prefer to respect their knowledge as they would not have done it without a reason given its cost and thus I leave their pin in place but ensure it does not induce stress raisers that may lead to a shaft failure.

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PostPost by: Craven » Wed Jan 10, 2018 1:25 pm

When a drive system is regularly and knowingly taken beyond its design capability then failure is guaranteed. Adding a failsafe element to my mind, if possible, is desirable.
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PostPost by: knockoffnut » Wed Jan 10, 2018 1:58 pm

I believe David's question is: "Should David upgrade the spindles from stock spindles?" and I think that the answer is "yes" as the original spindles are a known weak point. My own thinking on the extra groove is this: the shaft is near its limit due to its size, and the groove weakens it, so with modern high HP motors pushing on one end and modern, sticky tires at the other end there is a strong argument for no groove. Slippage is always preferable premature release...
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PostPost by: Chancer » Wed Jan 10, 2018 2:13 pm

When an old topic like this gets "resurrected" it's easy to forget that some contributors no longer use the forums. John was an engineer and a highly respected member of the BMW design team in Dachau before he retired, I tried not to question his technical knowledge in case he made me look sillier than I am :lol:

How embarrassing, was he not the gentleman that sadly passed away and is missed by many?

Its not hard to make me look sillier than i am and I thonk I have managed it all on my own this time :(
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PostPost by: Davidb » Wed Jan 10, 2018 4:40 pm

Chancer: I don't think you should feel embarrassed. Perhaps I should have been more careful.

My question still stands but I opened another thread in the 'Suspension/steering' sub-forum since this one got buried very quickly with other 'stuff'...
Last edited by Davidb on Wed Jan 10, 2018 5:02 pm, edited 1 time in total.
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PostPost by: Spyder fan » Wed Jan 10, 2018 4:54 pm

Chancer wrote:
How embarrassing, was he not the gentleman that sadly passed away and is missed by many?

:(


Yes that's him, the forum members raised £575 as a donation to the hospice that cared for him in his final days.

No need to be embarrassed, it's easily done, I'm often guilty of replying to topics without reading through the whole thread or noting the date of the original posts.

This topic had me looking at the manual to try and understand the subject, "3 wheels on my wagon" maybe okay to roll along, but not on an Elan.
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PostPost by: prezoom » Wed Jan 10, 2018 4:56 pm

I can remember a heated argument back in the 70's, regarding the need of a locating dowel for a cam pulley. One side tried making their point that the dowel kept the pulley from slipping on the cam, while the other side stating that the clamping force of the securing bolt was sufficient to prevent slippage, and the dowel was only there as an aid to provide the correct cam timing. I followed this with great amusement, though at the time, not sure which side was correct.

It is interesting to note that the cam pulleys on my 2L Zetec have no locating dowels, and rely totally on the correct torque of the securing bolt to prevent slippage. Cam timing is taken care of with a piece of flat plate inserted into a slot at the rear of the cam shaft, which is removed after tightening the securing bolt. A hex is provided on the cam for holding with a wrench, as the slot in the cam is not designed to take the stress of torquing the securing bolt. More accurate, or a change in factory timing, can be achieved with adjustable pulleys and a degree wheel. Still without a dowel or a key. Clamping force seems to be winning out these days.
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PostPost by: Chancer » Wed Jan 10, 2018 8:04 pm

Zetec has a belt drive which absorbs the inertial torque reversals, also a far far greater clamping area at a much larger radius, vernier pulleys even more so, once you start adjusting the cam timing you have to slot the retaining bolt holes resulting in a tiny clamping area under each bolt head and washer.

That said when I didnt have the correct offset dowel on a X/flow I would drill an 1/8" hole through the pulley into the cam boss and use a single roll pin which never failed.
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PostPost by: prezoom » Thu Jan 11, 2018 1:48 am

The engine in question was a Datsun L18, which has a chain drive. The proponent of not using a locating dowel was a SCCA multi National Champion, using both L16 and L18 engines. Will have to measure the clamping diameters of both the Datsun cam and the TC cam. RPM limits of both these engines are approximately the same.
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PostPost by: rgh0 » Thu Jan 11, 2018 8:53 am

The Datsun engines are SOHC which makes them easier to drive than DOHC cams as the valve loads on the cam balance more and make them easier to rotate

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PostPost by: Chancer » Thu Jan 11, 2018 10:56 am

The Zetec set up is a very good one, it always amused me that people would pay a lot of money for vernier pulleys (which were not vernier) which brought nothing to the party, had they a proper vernier indexing plate (9 dowel holes in one part 10 in the other) then I could see the attraction but they were just bling.
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PostPost by: pharriso » Thu Jan 11, 2018 11:32 am

Talk about topic drift... :evil:
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PostPost by: jimj » Thu Jan 11, 2018 3:40 pm

Drifting back as I was the OP, since then, with a keyway drilled and pin fitted I`ve had no issue. Don`t forget TT`s advice: you must torque up the hub nut every time you use the car. Hands up all those that do.............yeah! thought so.
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PostPost by: elansprint71 » Fri Jan 19, 2018 8:50 pm

To pin, or not to pin,
that the question...

I still miss the Bodger's words of wit and wisdom.

Aye,there's the rub (or is that hub?)! :twisted:
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PostPost by: patrics » Sat Feb 10, 2018 7:03 pm

In answer to David question:
In my opinion I would replace the rear spindles - the TTR spindles are torqued up to higher value - have larger diameter thread than standard, I also wouldn't bother with the pin if the taper doesn't hold the pin will be sheared in two with ease - it makes a mess, I know from experience.
Initially you must keep torqueing these things up, I got another ¼ of a turn out of mine before it finally settled down.

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Steve
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