Lotus Elan

Output shafts & rear Wishbones

PostPost by: richard sprint » Wed Jun 10, 2009 8:18 pm

In relation to fitting Tony Thompson drive shafts has anyone had a doubt or reason to change to the diff output and hub drive shafts? i.e. are the originals suspect and be known to shear?

In addition how about the rear wishbones have these ever known to be suspect?

This is a car to be used for friendly use I.e. non track use.

Richard
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PostPost by: rocket » Wed Jun 10, 2009 8:33 pm

I changed from rotoflexes over a year ago ,have had no problems since.

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PostPost by: 512BB » Thu Jun 11, 2009 11:40 am

Good afternoon Richard,

If i remember correctly, yours is a fairly late car and will already have the stronger diff output shafts. Dont waste your money on new TT ones.

Secondly, i seem to remember you telling me that your car was original, and therefore has its original A frames. So long as they havent been tweeked or bent, even slightly, when jacking the car, nothing wrong with them. Stick to original in my opinion.

Regards

Leslie
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PostPost by: batfish » Thu Jun 11, 2009 2:22 pm

Hi Richard

I snapped a diff output shaft quite a few years ago when I floored the accelerator at a crossroads but I have also seen TT's diff output shafts snapped as well.

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Andy
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PostPost by: richard sprint » Thu Jun 11, 2009 9:41 pm

Andy/Leslie

Thanks for your views and will stay with the originals especially as I have already pressed in the hub shafts/new bearings!

Leslie

I contacted the diff people at St Neots and now awaiting a call from the Carb guys at Leighton Buzzard who should have the Dellorto's refurb completed shortly so I can combine the trip.

I'm now starting some minor assembly to the new chassis and have purchased a nice flaring tool to make up the new set of brake lines, so things are moving on...

Richard
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PostPost by: Lincoln62 » Fri Jun 12, 2009 3:16 am

I reckon if your output shafts have lasted this long they would be up to the job (unless you boost power). If your car came with the weaker shafts they would most likely have broken by now and been replaced.

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PostPost by: ill_will » Fri Jun 12, 2009 3:36 pm

Richard-

Do you know what type of diff output shafts you have? It isn't that hard to check if you have (or can rig up) the right adapter for a slide hammer. You should be able to do it in situ. Might be worth replacing the bearings/seals while you're there and have it apart, too, if they're old. The reason I mention it is that I had one of each type (early/late) in the diff I have just rebuilt (which turns out to be a 3.55 motorsport one, so not what it should be at all) - the weaker one had twisted and was showing cracks on the splined bit. I found bits of an old drive shaft in the casing, which had evidently exploded: hence one early one late type. This was backed up by a bill for 176 pounds for a new inner drive shaft in 1996! I have gone down the TTR 4 ear diff, 3 ear outer driveshaft route, retaining original outer drive shafts. This is with a sprint engine. I haven't heard of anyone thats broken an outer shaft during road use. Probably now I've said that someone will tell me they have...

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PostPost by: GrUmPyBoDgEr » Fri Jun 12, 2009 6:33 pm

Fatigue is a factor which should not be overlooked.
By eliminating the "Rotoflexes" you will be taking a lot of the shock supression out of the drive train (which has until now survived).
I wouldn't dare to predict whether the other parts in the drive train should or should not survive.
When I chose TTR driveshafts I went the "Whole Monty" with his input & output shafts.
However I was pumping in a lot of power from a tuned Zetec engine.
Another factor:-A flailing TTR driveshaft will probablyl cost a lot more to replace than a flialing "Rotoflex" driveshaft, they're designed for well maintained competition cars where all parts of the drive train are equally strong & well maintained, also they're not light & could cause a lot of damage if an input or output shaft parts company.
I would say, if you can afford it do it; better safe than sorry.

Cheers & have a good weekend
John
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PostPost by: richard sprint » Fri Jun 12, 2009 8:20 pm

Will

The car is standard and original 1972 sprint so the stronger shafts are installed, no untoward issues found during diassembly and have factored in a complete set of new bearings.

John

Further to my earlier posts I have since been thinking that it would make sense to fit new parts for peace of mind/safety.

Also thinking that new wishbones would make all the rear end new and all fitted to a new chassis...

These matters certainly focus the mind and the wallet...

Richard
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PostPost by: bcmc33 » Fri Jun 12, 2009 10:09 pm

John,

I'm interested in the TTR input and output shafts you mentioned.

When I upgraded my car I added TT's billet diff output shafts and wheel spindles, I never gave the diff input shaft a thought. Was this a mistake?????

I've already spoken to Richard in regard to his existing Lotus upgraded transmission parts, and believe these are more than adequate for his intended use. I stand to be corrected, of course, but the 'weakest link' is the output shaft splines which is the usual failure mode. I would not expect this to result in a flailing driveshaft - and the sort of collateral damage we all fear most.

Richard's car has done so little mileage that use fatigue should not be an issue.

For the record what is the bhp and torque of your Zetac? Knowing you, I guess it would be in the region of 210bhp & 175 lbf ft. This should give Richard a good idea why you needed the billet parts simply for your peace of mind.
Brian Clarke
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PostPost by: paddy » Sat Jun 13, 2009 8:46 am

bcmc33 wrote:I never gave the diff input shaft a thought. Was this a mistake?????


I've never heard of them breaking. The torque experienced by the output shafts is nearly 4x the torque on the input shaft and physically they are similar diameters. Also, if they were even remotely vulnerable, I'm sure Tony T would let us know :)

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PostPost by: GrUmPyBoDgEr » Sat Jun 13, 2009 9:11 am

bcmc33 wrote:John,

I'm interested in the TTR input and output shafts you mentioned.

When I upgraded my car I added TT's billet diff output shafts and wheel spindles, I never gave the diff input shaft a thought. Was this a mistake?????

I've already spoken to Richard in regard to his existing Lotus upgraded transmission parts, and believe these are more than adequate for his intended use. I stand to be corrected, of course, but the 'weakest link' is the output shaft splines which is the usual failure mode. I would not expect this to result in a flailing driveshaft - and the sort of collateral damage we all fear most.

Richard's car has done so little mileage that use fatigue should not be an issue.

For the record what is the bhp and torque of your Zetac? Knowing you, I guess it would be in the region of 210bhp & 175 lbf ft. This should give Richard a good idea why you needed the billet parts simply for your peace of mind.


Hi Brian,

sorry a bit of a mix up in terminology; I meant that my drivetrain consists of TTR Billet Diff' output shafts, TTR UJ Driveshafts & TTR Billet outboard shafts.
My car was in a pretty horrid state (& there was no History with it) before I rebuilt it. I decided I could not put my trust in any single component of the car.
My decision was to do the job right & once only.
That decision was also swayed by the fact that I had to rent sufficient space to do the job & thereafter a single Garage would be my only facility.

You're a little bit off on the gestimation.
My engine develops 185-190 BHP at 6500-7000 RPM & has a fairly flat torque curve 165-170 Lb Ft from 3500 - 6000 RPM
Tweaked Cams, ported Head & stronger Valve Springs being the only changes to the stock engine.
I was told that 195 BHP could be obtained just with larger chokes but it's rare that the engine runs up to those revs & the idle would be terrible.
With the present set up it idles very sweetly at 900 RPM

Cheers
John
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