Lotus Elan

Sill Members

PostPost by: Midlife » Sun Nov 05, 2006 6:11 pm

If I am having a roll cage tied into the chassis with harness mounts, do I need the metal sill members? The sill members just add weight, or do they form some sort of structure for the shell?

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PostPost by: jkolb » Sun Nov 05, 2006 9:48 pm

They will help keep the front wheels from coming into the footwells if you hit something - very important, especially considering how fragile the front suspension components are.

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PostPost by: Old English White » Mon Nov 06, 2006 8:06 am

... With a picture , it help to understand ...
We can see the front member stop the wheel (black rubber tread) saving co-drivers legs ...

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PostPost by: Midlife » Mon Nov 06, 2006 8:29 pm

I might be missing something here and not wishing to ask the "dick head" question but... the roll cage design is such that it goes round in front of your feet, so if the wheel comes back into the wheel arch you get the protection.

I am asking why do you need the steel box section down the side of the car in the sill, if the roll cage has already got side impact protection?

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PostPost by: jkolb » Tue Nov 07, 2006 2:50 am

The cage ties into the sill bar just below the windshield. The sill bar runs all the way forward to the wheel arch, then is tied into the frame by a cross bar that fits under the pedal box. This way, the foot protection is there even if you do not purchase the cage. Note that if you get the cage you can also get side protection bars that fit between the rollbar and the cage vertical member. Pretty slick, but makes getting into the seat a real Houdini effort!

Jerry
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PostPost by: ppnelan » Tue Nov 07, 2006 4:22 pm

I think Doug is refering to a PLUS 2 - i.e. can you remove the standard Lotus sill members if you have a rollcage with the sill bars ? How important are the Lotus sill members in terms of structural bending stiffness of the bodyshell ?

I'm guessing that you'd have to 'tie in' the rollcage sill bars to the sills in a lot of places to get the same effect as the standard Lotus sill members ?
And I'm guessing that the sill members are very important for bodyshell stiffness on the heavier & longer +2 ? Lotus didn't use anything that wasn't necessary, unless it was free ! :D

To summarise, sorry, I've no idea, but maybe someone else has.... :wink:

:arrow: Matthew
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PostPost by: Midlife » Tue Nov 07, 2006 9:13 pm

Matt your right, your first paragraph describes what I mean. In terms off side impact the cage will protect, so does the sill do something for the bodyshell and is it needed?

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PostPost by: jkolb » Thu Nov 09, 2006 11:50 am

I agree with Matthew. You will probably experience problems with door fit and overall body stiffness if you remove the factory sill structure. It exists for that purpose, as it is far too low to present any side intrusion benefit.

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PostPost by: JJDraper » Sun Nov 12, 2006 9:20 am

Surely side intrusion occurs at the sill level? Most trees and lamposts and other street furniture start at ground level... or do you only intend to hit other cars?! I have read other threads doubting the effectiveness of the side impact bar, but having seen the results of cars hitting trees and lamposts, you realise that the bar is there to slow the car down as it wraps itself (literally) around an immovable object. It is not there to prevent other cars (or motorbikes) coming through the door. Even a tree as little as 7 or 8 inches in diameter will stop a small truck, and it will carry on without anything more than a slight scar which heals in a few years.

I realise this is a racing forum, where you may only hit other cars, but many cars set up for a bit of sprinting or track work will spend time on public roads as well. Perhaps a more sensible approach would be fabricate a lighter, stronger side impact bar - then market it to us all!!

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PostPost by: jkolb » Sun Nov 12, 2006 2:21 pm

Point well taken. In a car the size of an Elan, especially in a world populated by pickup trucks and SUVs (I live in the US) by far the highest risk of side intrusion comes above the 7-8 inch level. Unfortunately, there are many of these vehicles where I live with bumpers that would override the side intrusion bars of my roll cage as well. That is why my Elan will spend most of its time on the track, as there I control more of the variables.

There is nothing scarier than a Lincoln Navigator at 80, with a driver who is totally engaged in a cell phone conversation!

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