Lotus Elan

Why use a 26R chassis instead of a standard one?

PostPost by: Pastapesto » Sat Oct 12, 2019 11:02 am

Something has been puzzling me for quite some time now & it is this:

If you are restoring/renovating a car back to original spec (sort of as it left the factory) and you go to great lengths to get it to look standard, why do owners then fit a 26R chassis instead of a standard one. Obviously the 26R one is stronger & torsionally stiffer etc but for what other reason would an owner want a 26R one over an original type standard one. Surely for a road car the standard one gives the car it's well know handling & comfort that it has become known for and the 26R type must change that somewhat. Does it add anything to the value of the car as far as originality goes (which is where current thinking seems to be going) or does it detract from value? It goes without saying that if you are building a genuine 26R or GTS or a road going replica (with all of the bodywork changes too) that you would only use the 26R type but if not, why would you fit one on a standard road car that looks pretty original? Is there anything I'm missing here? Does a 26R chassis road car improve the handling greatly? Does it need improving any more? Does it make much difference?...........is the ride noticeably harder?
I am in no way trying to tell anyone not to do it, it's your car and your money etc......I would just like to know what makes anyone chose one over a standard one that pretty much hardly changed in its original design from start to finish of production........please, if you have fitted a 26R chassis, let us know if it was better or worse in any aspects and after you had done it, were you pleased with your choice? I really would appreciate your comments on this.........I really love the 26R look by the way so don't think I don't like them, I just want to get an answer to this puzzle.........

All the best

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PostPost by: Matt Elan » Sat Oct 12, 2019 1:36 pm

As I see it the 26R chassis has strengthening around the front 'Y' section, the front and rear turrets and the steering rack mounts which were to fix issues uncovered when early Elans were raced. So a 26R chassis will last longer than an original, but that's not really a consideration here as the Elan is now a cosseted plaything rather than a daily driver, and may be a little stiffer in places. I suspect that the extra stiffness would be all but undetectable in a road car with road set up suspension. So it probably comes down to bragging rights, availability and cost.
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PostPost by: elancoupe » Sat Oct 12, 2019 1:51 pm

In my case (25 years ago) my preferred vendor was selling the 26r chassis for exactly the same price as the standard unit. It was a no brainer....

I like the idea of having a stronger chassis, but I doubt that it affects the characteristics of a street driven car like mine. Given the upgraded suspension on my car , I think it makes for more of a complete package.
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PostPost by: Fred Talmadge » Sat Oct 12, 2019 5:15 pm

I'd think that after 50 some years our stock chassis have flexed enough, that some stiffening would be prudent to restore it like new and prevent future failure, for little money compared to acquiring a new chassis.
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PostPost by: CBUEB1771 » Sat Oct 12, 2019 10:52 pm

This raises an interesting question, at least to me. Did the original 26Rs use the small diameter rear springs that are imposed by the reinforcements to the rear turrets? If so, what did Lotus use in place of the Aeon rising rate rubber springs on the 26Rs?
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PostPost by: The Veg » Sun Oct 13, 2019 6:18 pm

An old racing mechanic I've met has suggested that even my road-only Plus 2 would benefit from the 26R frame mods. Any opinions on this?
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PostPost by: Pastapesto » Sun Oct 13, 2019 8:23 pm

Thanks for the replies to my original question fellas, what I was trying to get at was whether the original chassis was not up to the job it was designed for and therefore should all chassis have been superseded by the 26R type?
Apart from stuff like the engine mounting brackets cracking etc, the biggest weakness I can see is corrosion or rather lack of rust prevention. The original springs and dampers were designed to work with the torsional rigidity of the chassis & body unit as a whole so if you were to change the springs and dampers, I would imagine that the best way to get the most out of the new setup would be to have a stronger chassis to make it all work properly.
That said though, using a standard setup, would there be a need to choose a 26R chassis over a stock one unless
you were to feel that the original design was "not fit for purpose"? And if so, why is that?

As Fred said, no harm in strengthening an original chassis if you are doing a refurb, in fact I think that's rather a good idea but if you were replacing for a new one would you feel the need to go outside of the original design criteria?.....I would really like to try a standard car against a 26r chassied car with modified springs and dampers to really see the difference, has anyone got one of each and if so, what's the difference like?

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PostPost by: nmauduit » Mon Oct 14, 2019 8:01 am

my opinion is that the original chassis was "fit to purpose", purpose being road use.
A bit of chassis flex on the road may temporarily alter geometry, but that would not be noticeable I would think.

If one is 100% sure he will only use his car on the road, and not willing to use as a sales argument that his car can be upgraded to track use with limited changes, then an original chassis (or if not available an original specs replacement one) would have the additionnal advantage of better originality, which tend to be highly considered by some.

Then a significant number of Elan owners have a hard time resisting the urge of the track now and then... and with high grip modern tires there is additionnal stress that the original design was not intended for, and if probably overkill for the odd mild trock day, for a serious track use a reinforced chassis would be an insurance for improved reliability, and better controlled geometry at the limit for those pushing really hard.

Two separates schools of thought, both entirely legitimate.
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PostPost by: Certified Lotus » Mon Oct 14, 2019 10:11 am

I put a 26R chassis in my S1 rebuild as I was increasing HP and installed headers on the engine. The 26R chassis has a cutout for headers. But the real reason was because the 26R chassis is stiffer and better made with the reinforcements. My decision was based on the fact that a light weight fiberglass car could use all the support it could get. Minimize the flexing. After a couple thousands miles of driving, I never regretted making the decision of a 26R chassis. (Plus you get a built in tow hook and a removable front cross beam to remove the engine easier).
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PostPost by: trw99 » Mon Oct 14, 2019 2:34 pm

Adam, I fear it would be almost impossibly difficult to make a valid comparison between the two types of Elan chassis. The only way would be if one experienced individual was able to do side by side testing of two Elans, set up exactly the same, differing only in the chassis type fitted.

I'd also remind us all that at the time of it's launch, the Elan was praised for the strength of it's backbone chassis, as well as for the ability of its fibreglass body to absorb and dissipate crash impact energy. Bearing in mind this was 1962 and compared to many contemporary cars, the Elan was exceptional in many ways. Of course, things have moved on, as indeed have technologies and drivers expectations.

To my mind the original Elan set up, with its fantastic ride, handling and performance on the road, all very positively remarked upon in the day, is what the car is about and recreating those sensations most closely takes us back to those days. I do of course appreciate that others have different criteria for their Elans and have no issue with that.

To finish, a couple of interesting wee quotes for you:

“I don’t think I want to get involved with engines, I’m not an engine man, really. Mr. Ferrari himself was an engine man; Carlo Chiti is an engine man; Tony Vandervell is an engine man, but I am a chassis man, loosely speaking. And I think good engine men don’t necessarily make good chassis men, and vice versa. Engine men feel that the way to win races is to get more power from the engine. That’s what they understand, what they like doing. I’d rather have a nice, reliable, standard engine just like everybody else and try to build a better chassis.” Colin Chapman

"The Lotus 25’s monocoque “tub” design was revolutionary for automotive racing, and was touted as being three times stiffer but half the weight of a Lotus 21 chassis. The earlier Type 24 space frame only had about 650-700 lb-ft/deg torsional stiffness; the Type 25 monocoque tub gave about 1500 lb-ft/deg, and 2400 lb-ft/deg with the engine in place. However, Chapman would reduce the gauge 25% to save 73 lb (33 kg) which reduced the stiffness accordingly (his target stiffness then was about 1000 lb-ft/deg). The monocoque structures were more costly and time consuming to make, but required less maintenance. The Elan chassis weighed about 75 lb (34 kg) and the curb weight about 1517 lb (688 kg)." Brian Wiegand, Northrop Grumman: ‘Colin Chapman and Automotive Mass Properties’ 74th SAWE International Conference on Mass Properties Engineering

I've been trying to find the torsional stiffness figure for the Elan chassis, but can not currently put my hand to it. Anyone?

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PostPost by: kwhittle » Mon Oct 14, 2019 3:10 pm

Quote from my new book, now printing, and talking of small Elan

"During strip down of Falcon Carribbean 'mule' Hickman and ACBC decided to measure backbone chassis stiffness, which was 6000lb/ft degree"

Production Elan chassis were measured at 4300lb/ft degree
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PostPost by: Certified Lotus » Tue Oct 15, 2019 10:34 am

I have both a 64Elan S1 with a 26R chassis and a 65 Elan S2 with the original chassis. And I have driven them back to back countless times. I can confirm the 26R chassis makes the car much stiffer.

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