Lotus Elan

Time to decide between donuts and CV joints

PostPost by: StressCraxx » Tue Sep 03, 2019 3:32 am

RDent, JAE Parts and Dave Bean carry the CV axles.

They are designed to work at full droop on a stock suspension and not bind. They are designed a built by John Kouba (aka Lotus John). He has been building them since the late 80's.

Once you have priced a set of donuts, the required bolts and the diff output shafts (they fail at the spline roots- if they haven't yet, they will) they are a very reasonable price.
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PostPost by: vincereynard » Tue Sep 03, 2019 11:27 am

Reluctant as I am to support anything Spyder their single CV / Donut combination is another option to consider.

I still consider that full on CV shafts are a bit harsh for a mechanism (diff. etc) that is 50 year old and never designed for them. You do need some compliance. So better then than the sliding / Hooke joint things!

Even big, fat moderns RWD often have a form of Donut at the end of the propshaft.

My +2, with its single CV shafts, can be made to surge a little if I'm clumsy. Generally it is not noticeable.

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PostPost by: rgh0 » Tue Sep 03, 2019 11:48 am

Famous Frank wrote:If you drive like my father use to or my friend Greg, Donuts are probably fine. But decades ago, 1972 if I remember correctly, I was at a SOLO II event, (sometimes called a gymkana or an autocrosss). There was a driver there with a gorgeous looking Elan. He was driving it very, very hard. It looked so cool to someone my age to see a car oversteering out of a corner and then accelerating as hard as possible down a short straight. It was wonderful to watch! Then something broke, made some horrible noises, sparks coming out of the bottom of the car under the trunk area, just before he pulled off the course. We all ran up to see if the driver was okay and what went wrong. The driver was fine. There was fuel dripping like crazy from under the car. Amazing it didn't catch fire! I crawled under to see what broke. It was my first glance at a donut as my VW had CV joints. The Donut broke allowing the axle shaft to flail around. It bent the lower A-Arm, dented up the frame, and broke the fiberglass floor and punctured the fuel tank. I said to myself, "Hell! I'm never buying one of these cars!!!" (now I own 7)

When I purchased my first Elan not long after that incident, no one manufactured a CV conversion kit so along with a couple of Lotus friends we made our own from shortened VW axles.

That's how I drive and that's why I'll always have CV joints or sliding splines.

It's up to you! Good luck and stay safe!
Frank


Been there .. done that ... converted to Cv's 35 years ago using modified second hand used VW components from a wrecker, the CVs from the bus worked at a larger angle than the standard bug ones. Still use the same in my Elan today and only replaced one CV joint over all those years. Col Croucher at Elantrikbits helped me with the machining back then as I did the conversion and his Cv kit today is absolutely rock solid and does not need limiters.

cheers
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PostPost by: danielmo » Tue Sep 03, 2019 5:03 pm

Another vote for ElanTrikBits CV conversion.
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PostPost by: Tmac897 » Wed Sep 04, 2019 8:20 pm

Hmmm, I hadn’t really considered CV joints before. I have a “new” (from 1978) pair of couplings, plus two from the original suspension that look to be in pretty good shape. I think I fall into the “spirited driving” camp.

Budget is somewhat of a concern. Hoping my engine block is still good, but I need all the innards. Plus I need a head, cams, valvetrain, etc, although I do have the timing chain :wink:

I guess at this point I’m thinking I’ll put the rear end together with Rflex Couplings. Maybe change to CV joints if all else goes well.
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PostPost by: h20hamelan » Wed Sep 04, 2019 8:58 pm

danielmo wrote:Another vote for ElanTrikBits CV conversion.


This is what I chose, because droop limiting does not allow that wheel full contact with the road when drooped.
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PostPost by: Grizzly » Thu Sep 05, 2019 2:22 pm

I regard ElanTrikBits as the best made kit but you will pay for it, here in the uk it will cost almost twice the amount you would pay for a pair of Kelvedon shafts and Droop limited rear shocks.

The reason i decided to go with the reduced droop kit is because i saw issues with the CV boot popping off or ripping when articulated to the max (hump back bridges or jacking the rear end up off the ground), even the reduced droop Kelvedon kit still stretches the rubber boot to it's limit when the weight is off the rear wheels (they are pulled so tight you only need to nick one and it will rip open when you jack the car up.... as i found out).
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PostPost by: Grizzly » Thu Sep 05, 2019 2:31 pm

billmoore42 wrote:I put UK made donuts from R Dent in my 67 Elan S3 Coupe last year. They are still fine after 1200 miles, and if you read Brian Buckland's book, he thinks the modern donuts might be good for 20,000 -30,000 miles or so.

You might find a warmer climate helps keep the rubber in good order but here in the uk when it's cold the donuts really don't last anywhere near that long. Back in the day late 70's early 80's donuts would get 10-15000 miles on a +2 set before they showed signs of needing replacing (i had a donut let go on me smashing the caliper off the rear hub so whilst the car was in daily use i checked them on a fortnightly basis) but nowadays just leave a car parked in the same position for a few months and you will get separation starting to show (just not made to the same quality, probably due to rules and regulation changes in rubber manufacture in the UK)
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PostPost by: webrest7 » Thu Sep 05, 2019 10:47 pm

Simple answer... . #1
CVDS.
Simple answer... #2
Which type. Elantrikbits
See no dilemma.
:D
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PostPost by: Andy8421 » Fri Sep 06, 2019 10:31 am

Apart from the significant improvement in feel achieved by replacing the donuts (I disliked the rotoflex surge on pull away), donuts are mission critical and don't fail safe.

My post from 2014 on the subject:

"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 touched rotoflex."
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PostPost by: tdskip » Fri Sep 06, 2019 12:03 pm

I personally have no issues making reversible upgrades that make our vintage cars more usable/reliable/safer.

Thanks for the discussion, need to make a decision on sourcing soon.
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PostPost by: Tmac897 » Fri Sep 06, 2019 12:17 pm

tdskip wrote:I personally have no issues making reversible upgrades that make our vintage cars more usable/reliable/safer.

Thanks for the discussion, need to make a decision on sourcing soon.


Yes, this discussion has me rethinking my plan to reinstall my rotoflex couplings, even though I have some older, unused couplings.
Tony
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PostPost by: tdskip » Fri Sep 06, 2019 12:58 pm

To put it mildly, it’s disappointing that the quality of materials available has gotten so marginal. I refuse to put any rubber bushings on the TR4a or MGB for the same reason, at least with those cars the poly suspension bushings are widely available and generally excellent quality.

Do any of the vendors that supply these offer a group by? Wondering if there’s a group of us that can place an order at the same time to help both the vendor and also maybe save some money?
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PostPost by: lotusjohn » Sat Sep 07, 2019 5:31 pm

Decided I would put my 2 cents in here. My name is John Kouba and I am been manufacturing the CV kits that RD, JAE and DBE have been selling since the 1980's.

No limiting straps are needed. The Elan has way more droop than it ever needs. The CV kits do limit the travel but do not bind up like the sliding spline kits.

I am sure the Elan would have had CV's if they were around in 1962. The first production use was 1969 in the VW beetle. Donuts were "state of the art" and used on many formula cars of the era.

Many people find the "donut windup" an unpleasant attribute of the Elan design.

The donut failure issue is something to seriously think about. Many of the cars I have worked on over the years show the damage of donut failure.

With the common low yearly miles on these cars, time will be a bigger factor on replacement intervals. Poor rubber quality and environmental factors will lead early replacement.

I am open to group buys if anyone is interested.

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PostPost by: tdskip » Sun Sep 08, 2019 11:57 am

Hi John! Thank you for jumping in here.

I’m certainly interested in a group by, anyone else here?
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