Lotus Elan

Aeon Rear Suspension Bumper Info, Please

PostPost by: jbeach » Tue Feb 20, 2018 11:58 pm

Dear Rear Suspension Experts,

I've seen Rohan and others recommend installing both the standard Aeon suspension bumpers and the spacer used on the +2 to bring the Aeons into service a little earlier as the rear suspension heads toward full compression.

Can someone attach photos of the +2 spacer? Rdent doesn't stock the spacer, so I'm thinking I'll just fabricate a reasonable facsimile.

Many thanks!

-John
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PostPost by: MarkDa » Wed Feb 21, 2018 1:03 am

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PostPost by: Orsom Weels » Wed Feb 21, 2018 7:45 am

If you need dimensions, outside diameter 2 1/4", centre bore 1", overall depth 1 1/4", recess depth 1/4" (so giving a 1" extension overall), & recess inside diameter 2 1/8" (as best I can measure, they get a bit bashed over the years. As long as they are a snug fit on your damper tubes, it's not critical).
Easiest thing in the world to make with some alloy bar stock & a lathe :D

Regards, Tim
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PostPost by: SENC » Thu Feb 22, 2018 1:46 am

Have you checked Dave Bean? I see it listed on their rear suspension page - part 050D 0154
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PostPost by: jbeach » Thu Feb 22, 2018 3:35 pm

Thanks, everyone. I'll check Dave Bean for availability. If not, I'll fabricate.

It's interesting - when you look at the exploded view of the +2 rear suspension on the Rdent website, it lists this part (050D0154 - same as Bean), but does not show the part on the drawing. I don't want anyone to go to any trouble, but it would be nice to see a photo of the part in situ.

Best,

-John
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PostPost by: Orsom Weels » Mon Feb 26, 2018 4:57 pm

Hi John,

The spacer can't be seen in situ if the dust covers are still in place, as they are on my car, but hopefully this will show where it goes

img_0505.jpg and


Once the damper retaining nut is screwed home & tightened, the spacer then sits over it & is gently peened over in two or three places to hold it in place. This one would need a little more straightening of the old peening to drop over this particular damper nut.
There's a better picture of the spacer & aeon rubber & a bit more detail contained in this thread, lotus-suspension-f42/oversteer-t31635.html

Regards, Tim
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PostPost by: jbeach » Tue Feb 27, 2018 10:07 pm

Thanks for the photo and information, Tim.

So, in addition to the Aeon rubber spring, I need a spacer that's about 1 inch thick. I purchased two dense yellow poly spacers from TTR before I saw the importance of using the original Aeon configuration. So now, as I mentioned, I am using the original Aeons I purchased from Rdent.

I don't see the magic in using a metal/alloy spacer. Couldn't I use pretty much any "spacer" that is an inch thick and has good stiffness? Because, I'm contemplating cutting the yellow TTR spacers down to an inch and just putting one of them onto each damper shaft, on top of the Aeon rubber spring. I don't have a photo of my yellow spacers here at the office, but they're the conical yellow spacers in this photo on TTR's website:

https://www.tonythompsonracing.co.uk/pa ... 2016-pair/

I'd be cutting off the conical part to give my resulting 1-inch spacers the maximum thickness/stiffness. I realize the result will be more "squish" than alloy, but they're much stiffer than the Aeons. Shouldn't I still end up with a stiffer final three-or-so inches of shock compression than I would with the Aeon springs alone?

Did everyone follow that? What do you suspension engineers in the group have to say about this idea?

Best,

-John
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PostPost by: rgh0 » Wed Feb 28, 2018 8:38 am

Yes there is not need to make an alloy copy of the Lotus solution

I use a couple of 1/2 thick poly bushes that were originally for a roll bar that had the right ID and OD on the top and bottom of the standard Aeon rubber spring in my Elan. These are a better solution than than alloy cap as used on the late plus 2 as the OD is a little bigger and they protect the Aeon rubber better from damage against the strut top below or the spring retainer plate above. Being plastic they can float on the shock rod like the rubber spring does without damage

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PostPost by: jbeach » Wed Feb 28, 2018 10:08 pm

Perfect,Rohan. That’s exactly what I was thinking. I’ll keep everyone posted as I finish this up.
-John
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PostPost by: Frogelan » Wed Feb 28, 2018 11:22 pm

Rohan

Thank you for your wisdom on the Aeon rubber springs and additional bushing. I can see the sense of what you have suggested and presume that the Aeon is not cut down at all.

I will be shortly sorting out my S2 "GTS10" chassis and have just about understood most of the suspension posts here, but I am unsure as to (unloaded) spring heights for a (FIA minimum) ride height of say 100mm (4").

I plan a mix of fast road / track use using F & R Koni adjustables...

If I was to use 150 lb/" front and 120 lb/" rear springs which I believe to be "Rohan-specification" ;-) (the original 26R spec was for 128 and 100 lb/" respectively), what would be an appropriate unloaded spring height to order (assuming a car weighing in at say 600 kg) ?

This information would be very valuable as certain retailers are very sniffy about their "race springs" and a French friend of mine now finds himself with brand new race springs that give an impossibly low ride height...
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PostPost by: rgh0 » Thu Mar 01, 2018 10:09 am

Frogelan wrote:Rohan

Thank you for your wisdom on the Aeon rubber springs and additional bushing. I can see the sense of what you have suggested and presume that the Aeon is not cut down at all.

I will be shortly sorting out my S2 "GTS10" chassis and have just about understood most of the suspension posts here, but I am unsure as to (unloaded) spring heights for a (FIA minimum) ride height of say 100mm (4").

I plan a mix of fast road / track use using F & R Koni adjustables...

If I was to use 150 lb/" front and 120 lb/" rear springs which I believe to be "Rohan-specification" ;-) (the original 26R spec was for 128 and 100 lb/" respectively), what would be an appropriate unloaded spring height to order (assuming a car weighing in at say 600 kg) ?

This information would be very valuable as certain retailers are very sniffy about their "race springs" and a French friend of mine now finds himself with brand new race springs that give an impossibly low ride height...


Yes I use the standard Aeon spring, the aim of the spacers is to bring it into play earlier and stop the car squatting down on its outside rear wheel in a hard corner which is the cause of of much of the Elans instability and snap over steer on the limit with modern sticky tyres.

For a road and track day set up 150 front 120 rear and 7/8th inch roll bar works great in my experience. Perhaps a little to hard for the road and a little to soft for full racing but a good compromise if you have rough race tracks and smooth roads :lol:

Determination of the needed free spring length is not difficult if you know your desired ride height and current spring details and current ride height. Consideration must be given to ensuring that the spring does not become free at full droop also so this information on distance from normal ride height to full droop is also required. I can help to show you how to calculate it if you post those details

I buy TTR front springs and shocks as sets ( just have a new set to start fitting tonight !) as the front springs are a very heavily stressed design and I cannot get suitable ones made locally. The TTR ones are properly designed to work in my experience, though they do sag overtime as they are not as good a quality as they really need to be which requires a very high specification spring steel and hot coiling process which most people don't do these days. The rear springs are not so heavily stressed so I design and get my rear springs made locally for what I want.

cheers
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PostPost by: rgh0 » Thu Mar 01, 2018 10:09 am

Frogelan wrote:Rohan

Thank you for your wisdom on the Aeon rubber springs and additional bushing. I can see the sense of what you have suggested and presume that the Aeon is not cut down at all.

I will be shortly sorting out my S2 "GTS10" chassis and have just about understood most of the suspension posts here, but I am unsure as to (unloaded) spring heights for a (FIA minimum) ride height of say 100mm (4").

I plan a mix of fast road / track use using F & R Koni adjustables...

If I was to use 150 lb/" front and 120 lb/" rear springs which I believe to be "Rohan-specification" ;-) (the original 26R spec was for 128 and 100 lb/" respectively), what would be an appropriate unloaded spring height to order (assuming a car weighing in at say 600 kg) ?

This information would be very valuable as certain retailers are very sniffy about their "race springs" and a French friend of mine now finds himself with brand new race springs that give an impossibly low ride height...


Yes I use the standard Aeon spring, the aim of the spacers is to bring it into play earlier and stop the car squatting down on its outside rear wheel in a hard corner which is the cause of of much of the Elans instability and snap over steer on the limit with modern sticky tyres. i did experiment with different Aeon springs at one time as alternative stiffness ones are / were available but I concluded in the end that the standard ones worked best, not to soft and not to hard, just right to paraphrase the three bears

For a road and track day set up 150 front 120 rear and 7/8th inch roll bar works great in my experience. Perhaps a little to hard for the road and a little to soft for full racing but a good compromise if you have rough race tracks and smooth roads :lol:

Determination of the needed free spring length is not difficult if you know your desired ride height and current spring details and current ride height. Consideration must be given to ensuring that the spring does not become free at full droop also so this information on distance from normal ride height to full droop is also required. I can help to show you how to calculate it if you post those details

I buy TTR front springs and shocks as sets ( just have a new set to start fitting tonight !) as the front springs are a very heavily stressed design and I cannot get suitable ones made locally. The TTR ones are properly designed to work in my experience, though they do sag overtime as they are not as good a quality as they really need to be which requires a very high specification spring steel and hot coiling process which most people don't do these days. The rear springs are not so heavily stressed so I design and get my rear springs made locally for what I want.

cheers
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PostPost by: Frogelan » Thu Mar 01, 2018 10:45 am

Thank you Rohan.

I am starting from scratch (I do not even have the old springs!) and will have front and rear S2 26R type suspension. The front suspension arms have been copied from an original S1 26R.

TTR does not give out many details on his suspension and the french friend of mine now finds that the springs from TTR are too short (I have not seen them in situ) and that remedial action is needed (for a S1 26R chassis) in order to meet the ride height rules!

I do not know whether he asked for the wrong thing (which given his limited English is of course possible), but he claims he bought the TTR race springs.

I suspect the best way forward will be to simply buy a set of fast road springs from TTR for a rough initial set up and then proceed by elimination with different sized springs from a supplier such as Faulkner. Fortunately springs are not too expensive (about £30 + VAT each) so this may be the way to go...

I will publish my findings...
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PostPost by: rgh0 » Thu Mar 01, 2018 11:00 am

If you can do a dummy setup of your suspension and determine full bump spring length ( to check for coil bind) and full droop spring length ( to check for spring release) and normal ride height spring length required, with the spring platform in a rough mid range location and the range of spring platform adjustment available around this and you know roughly your corner weights, then the spring can be designed in terms of required free length and coils and wire diameter for your selected 150# front and 120# rear

cheers
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PostPost by: nmauduit » Thu Mar 01, 2018 12:10 pm

Frogelan wrote:TTR does not give out many details on his suspension and the french friend of mine now finds that the springs from TTR are too short (I have not seen them in situ) and that remedial action is needed (for a S1 26R chassis) in order to meet the ride height rules!


Springs typically come in 1" length increments, sometimes 1/2", so if you want to have a better ride height control than that one will need a way of shimming. Also, most if not all new springs sag after some use (I would count on 5% to 10% to be on the safe side), so one would need to take that in account, too... would it be to pass inspection or merely road bumps.

For what it's worth, I've installed 175 pound/inch front springs on my 680kg S4se (+77kg driver...) 120 pound/inch rear, those are 9" springs (I have shimmed the bottom somewhere between 1" and 2" iirc, adjusted when setting the corner weights).
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