Lotus Elan

solid drive shafts vs rotoflex

PostPost by: el-saturn » Fri Apr 18, 2014 9:15 pm

......................ok fellas, i agree: you?re a couple of 10ths quicker aas a racer (at yr local intersection/turnabout AND race) BUT everybody who has raced anything (i only raced my mike wilson/parillas carts and my elan: against crazy race oriented pals) knows: you don?t normally win the race due to yr first lap?s exravagancies SO why (t....) abuse your x,w,z-components if you can outdrive ?em without a racing clutch and solid drive shafts which weigh 5x (you know better than I) - it?s the tyres, yr faith and courage NOT the BETTER (?) 20kg drive shafts - pls correct me, if i?m wrong - s.j. alps
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PostPost by: roblotus79 » Fri Apr 18, 2014 10:20 pm

For me its never having to worry or think about a broken rotoflex again. Also rotoflex are getting so expensive and are poorer quality.
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PostPost by: rgh0 » Sat Apr 19, 2014 12:17 am

CV drive shafts will not make you any quicker I agree. But they do give you more chance of getting to the end of the race or the end of whatever trip your on. "To finish first - first you have to finish"

A set of CV drive shafts is only a few kg more than the rotoflex assembly so the weight penalty for reliability is small. I had two donut failures early on in my Elan, The first was a failed locating bolt and did no damage ,The second failed completely ripping the chassis and coming very close to my rear end :shock: . Also had one in the Plus 2 that fortunately did no chasiss damage despite ripping the centre retaining pin off as it failed. Now I have had CVs on both cars since the mid 80's without any issues.

cheers
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PostPost by: el-saturn » Sat Apr 19, 2014 6:51 am

i do agree BUT I?m constantly looking at my doughnuts and another arguement are the higher
loads going thru diff, gearbox, chassis. i actually DID have a rotoflex incident whereafter only some
minor body-work was to "re-arrange" and having a cage behind my a... it also touched one of the bars!
...................... BUT I have considered THE alternative easter greetings from the fresh snow - sandy
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PostPost by: Hawksfield » Sat Apr 19, 2014 12:55 pm

Hi

Ive had my drive shafts in for around 10 years now (Mick Miller) fit and forget, also any work that required rear suspension removal is much easier to do and quicker.
Would not be without them
Regards

John

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PostPost by: Famous Frank » Sat Apr 19, 2014 3:07 pm

The year was 1970. I was at a local Slalom Race. I was racing 69 VW. Interestingly, VW Beetles in 1969 came from the factory with CV joints even on a 47 horsepower motor. At the event I saw one of my first Elans. This race consisted of only three timed runs of approximately 1 minute each. The Elan was such a cool looking car. This particular one was an unmodified 1968 S4 DHC. On the second run the Elan broke a rotoflex. The rear axle flaying hit and bent the lower control arm, hit and bent the frame, and hit and punctured the fuel tank!!! Leaking fuel was everywhere. What a horrible, dangerous thing to happen. It could have been even more catastrophic!!! I thought to myself, this would never have happened in a German car.

Years later I purchased my first Elan. One of the first mods I made was some friends of mine removed a set of axles from a VW beetle, shortened the axles, and made one of the first sets of CV Axles. If nothing but for the fact that if something broke, the axles staying the same plane and did not tear up the rear end, .......INCLUDING THE FUEL TANK!!!

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PostPost by: patrics » Sun Apr 20, 2014 3:15 pm

Hi

I changed to the TTR solid drive shaft conversion including input and output shafts and was anal enough to weigh everything - the TTR set up it is lighter than the original.

Standard set up Total 11.5kg
TTR Sliding spline Total 10.3kg

Just for info
Regards
Steve
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PostPost by: Andy8421 » Mon Apr 21, 2014 12:57 pm

In the past I have raced an Elan in HSCC events in the UK. While I can't speak for every Elan, all of the Elans that I looked at in detail in the paddock (and mine) used TTR sliding spline driveshafts. This was for reasons of safety, not performance.

Sliding splines lock under load, so they are not ideal. In period, racers used 'ball splines' that didn't suffer the same problem. Given that the suspension on a racing Elan has very limited travel, I guess that the locking issue isn't as important, although I personally would have preferred CVs (unfortunately not permitted by the regs).

I have Sue Miller CVs on my road going Elan.

I am convinced that if plunging CVs were available at reasonable cost when the Elan was in production that Chapman wouldn't have touch rotoflex.
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PostPost by: Geoffers71 » Mon Apr 21, 2014 5:27 pm

I've been following this thread with interest as I have to replace the 4 rotoflex couplings on my S2. In the "store" at the back of my garage I've found these that I've had for years
SNV32325.JPG and


I don't know whose these are and I can't remember where and how I got them, but the obvious thing to notice is that there's no splines . What is the general view about them? Should I use them? Does anyone recogise their format? Who made them? They may be an early experiment by someone to reduce the dependance on donuts, but would the absence of splines put any undue stress on the rest of the drivetrain.
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PostPost by: billwill » Mon Apr 21, 2014 7:08 pm

That looks a bit like the Spyder drive option that has one doughnut at the diff end and a flexible joint ar the wheel end.

I think the modern version uses a CV joint so that might be an earlier type using a U/J instead.
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PostPost by: elanman999 » Mon Apr 21, 2014 7:18 pm

Billwill,
Yes they look a bit like Spyder ones but they are not them.
The Spyder U/J ones have a sliding spline to take up the change in length. I'll try to add a pic later if I can find one.
Cheers
John
Pic added, Spyder +2 shafts.
IMG_0132rs.jpg and
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PostPost by: Geoffers71 » Mon Apr 21, 2014 8:02 pm

So, since mine do NOT have the splines and therefore they will not adjust for change in length, I'd better not use them! Eh :? :?
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PostPost by: Andy8421 » Tue Apr 22, 2014 4:58 am

Rotoflex absorb a certain amount of plunge along with angular displacement, that's how the original system worked. I have not seen a half rotoflex / half hook joint without a spline before. In your case you are relying on one rotoflex to absorb the plunge originally shared by two. I don't know whether that will be sufficient.

To be honest, the half rotoflex / half hook joint / spline solution seemed to my mind to be the worst of all worlds, almost a case study of things not to have in your halfshaft.

If I was going to mess around changing driveshafts, I would install a CV solution and have done with it. Just make sure to limit the suspension travel to avoid CV lockup.
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PostPost by: Geoffers71 » Tue Apr 22, 2014 6:49 am

Andy, Your analysis sounds right to me. So they're for the bin :D
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PostPost by: billwill » Tue Apr 22, 2014 10:15 am

Don't bin the doughnuts they may be fairly new Old Stock.
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