Lotus Elan

ROTOFLEX QUESTION

PostPost by: gearbox » Mon Oct 22, 2012 5:46 pm

I am trying to determine the age of a set of Rotoflexs I have. They are NOS, never mounted, and look new, but since they have the solid mounting tube instead of the split tube found on all the new Rotoflexes I have seen for the past couple of decades, I have to assume they have to date back to the 80's or earlier. I also notice that they have smooth sides with no ribs between the holes, so maybe 60's? I recall reading a thread saying the ribs were on the Sprints and were the HD Donuts and they started to make all the replacement donuts HD from then on. So any idea how old these donuts are? Thanks Allan


The Rotoflex in question
$T2eC16NHJGoE9nuQeSHwBQfZk2UcS!~~60_57.jpg and



The current ones available today
sZsi9XwLEo6W6WB4AZMmDY6q9X7mSXMnFb71FWdHEaNOHacnEjAz8nvjDnwn9dR4JXtX_.jpg and
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PostPost by: billwill » Mon Oct 22, 2012 6:06 pm

When I first had my Elan back in 1969, it had the doughnuts without the ribs between the holes. I probably changed to the ribbed ones when the first ones wore out.

I do remember that there was noticeably LESS wind-up surge on the ribbed ones, so they must be quite a bit stiffer.

That photo of yours seem to show the metal bits chrome plated?? Surely not.
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PostPost by: oillite » Mon Oct 22, 2012 6:09 pm

Top one is of the type used on early lotus, Hillman Imps and some forklift trucks, very good for taking out the boot floor when they let go. Which happened to me with a brand new set of sprint ones when they first came out it the 70's.
Ditch the rotoflexes and fit c/v's.
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PostPost by: gearbox » Mon Oct 22, 2012 6:51 pm

oillite wrote:Top one is of the type used on early lotus, Hillman Imps and some forklift trucks, very good for taking out the boot floor when they let go. Which happened to me with a brand new set of sprint ones when they first came out it the 70's.
Ditch the rotoflexes and fit c/v's.


I'm leaning torwards the TTR U Joint half shafts as the rumor has it that the new CV axles are failing due to the quality of the new CVs. Seems that the story is the same with the new rotoflexes as the new rubber they are using is failing prematurely as well. I have to assume these Donuts I have are NOS circa 1960's? So the rubber should be the good stuff, albeit 40 years old. They look brand new and the rubber flexes nicely with no signs of cracking. Maybe better suited for someone restoring a S1 or S2 back to 100% OEM for a concor. But just wanted to know if anyone knew when these older versions disappeared from production.

Billwill - LOL, no, not chrome, just very clean.
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PostPost by: Fred Talmadge » Mon Oct 22, 2012 7:34 pm

You are not going to install 40 year old Rotoflex are you?
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PostPost by: gazzamuffin » Mon Oct 22, 2012 8:08 pm

gearbox wrote:
oillite wrote:Top one is of the type used on early lotus, Hillman Imps and some forklift trucks, very good for taking out the boot floor when they let go. Which happened to me with a brand new set of sprint ones when they first came out it the 70's.
Ditch the rotoflexes and fit c/v's.


I'm leaning torwards the TTR U Joint half shafts as the rumor has it that the new CV axles are failing due to the quality of the new CVs. Seems that the story is the same with the new rotoflexes as the new rubber they are using is failing prematurely as well. I have to assume these Donuts I have are NOS circa 1960's? So the rubber should be the good stuff, albeit 40 years old. They look brand new and the rubber flexes nicely with no signs of cracking. Maybe better suited for someone restoring a S1 or S2 back to 100% OEM for a concor. But just wanted to know if anyone knew when these older versions disappeared from production.

Billwill - LOL, no, not chrome, just very clean.





I have the TTR U joint half shafts, they fitted easily and are very good quality, I have never driven an elan with the rotoflex dohnuts so cant comment on the difference in feel, however i really do think the TTR half shafts are a good robust design
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PostPost by: Chancer » Tue Oct 23, 2012 9:47 am

Fred Talmadge wrote:You are not going to install 40 year old Rotoflex are you?


Why not! If you arent then sell them to me please and I will, they will be far better than whats being made these days, my father used to mould them in the 70's and 80's!

That said they are the Hillman Pimp ones and not the re-inforced Elan ones although I would have far more faith in NOS of the weaker type than what is passed off as the re-inforced ones today.
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PostPost by: elancoupe » Tue Oct 23, 2012 9:53 am

gearbox wrote:
I'm leaning torwards the TTR U Joint half shafts as the rumor has it that the new CV axles are failing due to the quality of the new CVs.


This news to me. All of the conversions I have seen here in the US utilize the tried and true Lobro (VW) joints, never heard of a problem.
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PostPost by: rgh0 » Tue Oct 23, 2012 10:33 am

I believe Lotus used the non interleaved rotoflex ( aka Hillman imp ) until 1969/70 for both the Elan and Plus 2. They advertised the intorduction of stiffer coupling with the sprint but I suspect this actually hppened during late S4 production a little earlier.

This is based on what I saw on cars in the early 70's when many late sixties and early seventies cars were still running their orginal donuts.

No reason to not try the NOS donuts if they look OK but I would check closely for cracking after intial installation to see how they stand up to use.

cheers
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PostPost by: Elanintheforest » Tue Oct 23, 2012 11:00 am

Put them in a vice and bend them around to see if there's any visible cracking. If they've been stored out of direct sunlight they should be fine.

I have a couple of sets of the non-leaf couplings that must be 40 years old and they're like new. They came from the same source as a set that I fitted to my S3 in 1979, and they are still OK...I kid you not!

Don't believe that fitting jointed driveshafts will end all woes....there are quite a few topics on this forum where things have siezed up and the halfshaft is US. The covers seem to split easily and let water and dirt in, then they don't last too much longer.
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PostPost by: Fred Talmadge » Tue Oct 23, 2012 1:23 pm

All "rubber" parts have a shelf life, no matter if they aren't exposed to light. You wouldn't put 40 year tires on your car and I wouldn't trust 40 year old Rotoflex either.
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PostPost by: ardee_selby » Tue Oct 23, 2012 2:21 pm

Failure mode....?

I'm sure there are pictures of broken rotoflexes already in here somewhere...but have a look at these links:

http://www.flickr.com/photos/comins/715 ... otostream/

http://www.flickr.com/photos/comins/700 ... otostream/

The rubber doesn't appear too aged and it is the bonding to the metal component that has let go (rather than a crack propogating through the rubber...) and let water in to corrode the steel insert. So I would look closely for signs of separation at that point as much as cracking of the rubber in the NOS couplings.

Maybe the fewer rubber/metal interfaces in a coupling the better ?

Cheers - Richard

FWIW Info: http://www.missionsupplyonline.com/pdf/rotoflex.pdf
Last edited by ardee_selby on Tue Oct 23, 2012 3:47 pm, edited 3 times in total.
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PostPost by: gearbox » Tue Oct 23, 2012 2:25 pm

elancoupe wrote:
gearbox wrote:
I'm leaning torwards the TTR U Joint half shafts as the rumor has it that the new CV axles are failing due to the quality of the new CVs.


This news to me. All of the conversions I have seen here in the US utilize the tried and true Lobro (VW) joints, never heard of a problem.


Hey Mike;

This is what I have been reading about on this forum and others. Sue Miller stopped selling the CV jointed shafts because of the massive failures and TTR says the geometry doesn't work and cannot find a solution. From what I have read, there are two issues, one is the range of motion and the shortness of the shaft on the Elans which over extends the CV joints to failure. Apparently, if you jack the car up and rotate the wheels, the CV's would lock up or clunk badly. Secondly, when these CV shafts first came out, the Lobro CV's were being made better and no failures of note occured. But with the new batch or design, they had been failing left and right. Well, that is what I got from reading numerious posts.

I like the TTR system, 2 U joints on both ends, but you have to upgrade to the steel diff output shafts as the system is so direct, it will undoubtedly twist the cast parts apart. Unfortunately, I keep on looking at the aluminum ears on my diff, very fragile and time has not been kind. So I can see a possible failure using this system. But the idea that when a U joint fails, it's a 20 dollar repair appeals to me. On my other Elan, I have a cross of rubber rotoflexes on the inboard side and U joints on the outboard. At least this system will cushion the torque on the diff and I only have to worry about the two inboard donuts. But I cannot find find who still makes them. It may have been Spyder in the early days, but not sure. BTW what are you using on the 26R conversion? Allan
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PostPost by: RogerFrench » Tue Oct 23, 2012 3:27 pm

The Lobro shafts I've seen here, as marketed by RD Enterprises, for example, are quite a bit different from, and more expensive than, those sold previously by Sue Miller etc.

Look here http://www.rdent.com/ select Elan Parts and scroll down.
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PostPost by: gearbox » Tue Oct 23, 2012 3:40 pm

Fred Talmadge wrote:You are not going to install 40 year old Rotoflex are you?


Are you kidding me? With the esculation of Elan prices and the value of the early versions using these type of rotoflexes all I have to do is to find someone that wants a 100 point Concour car that is 100% original and is willing to trade me a set of TTR half and diff shafts lol. But all kidding aside, they would be better suited for a trailer queen. But with that said, I have to tell you, these things look like they were in a vacuum packed time capsule. I cannot find one single flaw, crack or abrasion, no matter how much you twist them. Plus, from what I understand, this part is much like a water pump or master brake cylinder, it gives you lots of heads up time before it completely fails. So if you ignor the signs, and in this case a visual inspection from time to time, you can avoid the off catostrophic failure. Well at least that is what I am thinking. So will I use these? I have no qualms, so maybe. But I have some time to think about it as my car will not be done until next summer. But if someone really wants these in trade for a TTR system, they are gone lol. Not holding my breath.
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