Lotus Elan

steering column joint

PostPost by: rdssdi » Fri Jul 03, 2015 11:14 am

My TVR has a steering column coupler like my Elan +2. I am having a problem which I have not experienced with my +2 but was wondering if anyone has.

I tightened and safety wired the bolts on the coupling. Within a short period of use the steering wheel would have fore and aft play. Upon examination I found that the coupling where it attaches to the rack pinion was loose and allowed it to move on the pinion splines.

The bolt was the same tension and the safety wire intact. I removed the safety wire and re-torqued the bolt. Again all was fine.

After a drive yesterday I noticed a small amount of play reappearing. Could the coupling be squashing? Slightly smaller pinion spline diameter? I believe the +2 and TVR share a similar rack. I am baffled.

Bob
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PostPost by: rgh0 » Fri Jul 03, 2015 1:09 pm

The bolt should fit though a groove cut in the shafts that stops axial movement - do you have the grooves and the correct size bolt ?

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PostPost by: rdssdi » Fri Jul 03, 2015 1:36 pm

The problem of "fore / aft" or "in and out" movement of the steering wheel / column is not because of the bolt and shaft groove. That groove will stop the coupling from sliding off in the event the bolt loosens.If it loosens and begins sliding off the pinion shaft the bolt grip will contact the portion of the pinion shaft which is the full diameter. The bolt is the correct diameter.

I was wondering if the ground wire I used which was constructed of regular crimp ring terminals is to blame. I theorize that it is possible for the ring portion of the terminal which is under the bolt head or nut compresses and allows the "pinch" bolt to loosen slightly.

I an skeptical because my +2 has a similar arrangement and maintains a tight coupling fit. It may be that the coupling to pinion shaft dimensions are at the maximum and a small change in bolt torque allows the coupling to slide.

In any event I purchased hardened tab washers. I can solder a wire to the tab and the washer which is Rockwell B90 hardness should not allow creep. I will report once I assemble it with the new washers.

Bob
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PostPost by: mbell » Fri Jul 03, 2015 4:26 pm

I think there was a thread on this same issue on here fairly recently. I think the conclusion was the problem went away after a couple of tighten/drive cycles. Not sure the reason why it took a few cycles was figured out thou.
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PostPost by: ensign42 » Fri Jul 03, 2015 6:14 pm

Perhaps the simple solution would actually be a thread lock type glue? I have seen vibration cause lots of similar issues- and I use lock tight type products for almost everything unless it is specifically something contraindicated.

Just a thought

- Will
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PostPost by: Elan45 » Fri Jul 03, 2015 6:25 pm

I have seen these joints with both 1/4" and 5/16" diameter bolts. You said it is the right size but didn't say what size it actually was. If 1/4" , I'd be all for trying to use a 5/16 diam bolt instead.

Roger
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PostPost by: rdssdi » Fri Jul 03, 2015 6:46 pm

I will measure the bolt diameter and post it. I cannot remember.

I will use the new tab washers in lieu of the soft ring terminals. Then tighten and safety wire.

If it loosens I will re-torque and safety wire as required.

Bob
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PostPost by: rdssdi » Tue Jul 07, 2015 4:02 pm

Unfortunately the tab washers I purchased were too large. I have ordered smaller diameter hole size tab washers as well as "high temperature" ring terminals which are made from steel and should be harder than the terminals I used. One of these items will work.

The pinch bolt is 1/4" diameter.

I hope to post some photos once the parts arrive and all is re-assembled. My camera no longer functions . I purchased a new one and am awaiting delivery.

Bob
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PostPost by: Quart Meg Miles » Tue Jul 07, 2015 10:19 pm

rdssdi wrote:The pinch bolt is 1/4" diameter.
Bob

Never mind the bolt size, what is the hole size! On my previous car I had the shaft pull right out, luckily while I was parking, because the bolt was the wrong size.
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PostPost by: rdssdi » Thu Jul 09, 2015 12:59 pm

The bolt and bolt hole are 1/4". A 5/16 is too large and will not fit into the hole.

I shall have the coupling reassembled tomorrow with the new "non compressible" ground lugs. If it loosens again I will retighten as required. There is not much remaining to change. I was wondering if the replacement coupling is manufactured in a "metric" size and is marginally larger than the original "inch pattern" unit. Just a thought.

Bob
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PostPost by: nomad » Tue Jul 21, 2015 11:59 am

Another thing to consider with the pinch bolt is to have a bolt with a shank that is contacting the splined portion of the steering shaft and not one that only contacts on the bolt threads. Much safer.

I also use the easiest to remove 'Loc Tite' on that coupling. Once saw a fellow pull his steering shaft out during an auto cross.....the thought of it at speed!!!

Kurt
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PostPost by: rgh0 » Tue Jul 21, 2015 12:43 pm

The shaft on the rack and the shaft on the steering column should both have a groove in them that the bolts on the coupling go though. It is not possible for the coupling to pull off the connecting shafts with the bolts in place and the grooves on the shaft or even for much axial or radial free play in the connection. if this is the case you have a fundamental problem with the assembly that needs investigating versus the original design.

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PostPost by: nomad » Wed Jul 22, 2015 3:57 am

I don't disagree, Rohan, but feel much safer having a solid bolt shank doing the work rather than the threaded portion. The case I mentioned was a lost bolt that obviously wasn't fitted properly in the first place. As to the loc tite, it will get rid of any tendency for the splines to begin moving if the bolt is a little loose as in this case.

Those things make me feel better anyway! :)

Kurt.
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PostPost by: andyelan » Fri Jul 31, 2015 11:44 am

Hi Everyone

I had a similar problem recently when I fitted a new coupling to my Plus 2. No matter how hard I tightened the pinch bolt it wouldn't stay tight on the steering column and there was always a little bit of play. When I took it off the car and inspected it, I found it was much chunkier than the original and consequently so ridged, no matter how hard I tightened the pinch bolt, it wouldn't pull up enough to grip the shaft. I ended up rebuilding the original coupling and re-fitting that.

Regards
andy
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