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26R Chassis mods vs rollcage

PostPosted: Sat Dec 08, 2018 7:58 am
by el-saturn
good morning everybody (europe)!! .......................once upon a time i restored the entire car (81-85) and got the frame zinc coated BUT was unaware of the 26R mods, so they haven't been added H O W E V E R and my actual question: doesn't my FIA rollcage (safety devises) compensate or add this additional stiffness or rigidity, so those strips (or triangles) of x-gauge steel are in comparison useless!?!?!? the cage weighs 10fold!! :oops: - my knowledge of finite elements etc.. isn't good enough anymore --- i'm just a reg. engineer and certain stuff is "beyond me" --- there's a bunch of wizards on this sight:............................. cheers sandy, alps

Re: 26R Chassis mods vs rollcage

PostPosted: Sat Dec 08, 2018 8:32 am
by Frogelan
I'm not an engineer...

Here are a few observations on the chassis (based on careful examination of various chassis):

- if you compare a "contemporary" 26R chassis with an original chassis, the gauge of steel is thicker on the former than the latter
- there are many different points of strengthening beyond the triangles on the turrets
- a few aspects are still not fully addressed (strengthening the engine mountings for example)
- many of these subtle changes can be credited to kaizen by TTR and Gartrac.

With respect to "FIA" roll cages, their role is to protect the driver. Their secondary role of strengthening improves the rear 50% of the car...but does very little to the front.

There are also 2 distinct generations of roll cage.

The 90's TTR / Safety Devices cage (only suitable for RHD as the inner triangle would provide limited protection to a LHD driver) now faces a second generation of "stiffer" competition from more complete MSA models (Andy Robinson, Custom Cages, Kelvedon Lotus. A new model from TTR / Safety Devices is indeed rumoured...).

There will be a difference in weight of at least 10-15 kg between the 90's spec and the current spec and not surprisingly the new cages cost at least 3 times more...(more metres of tube...more expensive tube...more labour...but more safety).

I'm looking at all the cages at present and keeping an open mind!

If you are buying a GTS car prepared with a 1990s cage, it is probably wise to factor in an upgrade.

Re: 26R Chassis mods vs rollcage

PostPosted: Sat Dec 08, 2018 2:49 pm
by el-saturn
thanks - these's most probably a small section between both stiff cubes (tetraheders!): the caged passenger section with the rear axle and the motor area (the motorbrackets are a bit "rubbery") and i could add a "stiffener" - sandy

Re: 26R Chassis mods vs rollcage

PostPosted: Sat Dec 08, 2018 11:08 pm
by rgh0
You could always use the Chapman design method of "Drive it until it breaks then make the bit that breaks stronger. Any bits that don't break you make lighter until they do break."


Re: 26R Chassis mods vs rollcage

PostPosted: Fri Dec 14, 2018 11:58 pm
by 661

Re: 26R Chassis mods vs rollcage

PostPosted: Sat Dec 15, 2018 12:29 am
by Davidb
It may be worth re-stating that the so called "26R chassis" mods are a relatively new phenomenomenom... When I bought my two 26Rs in the early eighties-the first with very low miles-neither had any of the gusseting that is currently considered "26R spec" Although I confess that my current Elan has it because I believe it finishes the chassis the way it should have been done in the first place!

That Safety Devices video is fascinating-I wonder what that lot weighs?

Re: 26R Chassis mods vs rollcage

PostPosted: Sat Dec 15, 2018 11:44 am
by Frogelan
It looks very good, especially in terms of protection to the pedal box area. Very clear Safety Devices video / pictures.

I understand it weighs around 38kg (in its lightest mode - but it depends on the steel used).

The questions that I have are:

- is it going to be sold ready made up for the owner to bolt in (the F' book video says it is a "Weld In Cage Install") ?
- is it possible to raise the bar which crosses behind the dash (to keep it out of sight and way from the occupants' knees) ?
- is there enough room for race seats (on the sides)?

Re: 26R Chassis mods vs rollcage

PostPosted: Sat Dec 15, 2018 1:09 pm
by 661
As Tony and Eddie have now met with Safety Devices and have approved the cage, the following can be released.

The cage in the pictures has virtually every tube option and weighs 37.5Kg. I would guess the full monty would be 38Kg, but I doubt any individual would want every option, indeed many may choose to have much less.
thumbnail_img_0833.jpg and

The dash bar is optional. I wanted it to support the steering column. The height was chosen to allow a bracket with spacers to be placed on the dash bar and to support the steering column. I would imagine it would be very easy to request this to be raised should you wish. I'm not sure it would be needed. I'm an odd shape. Short arms. My legs are a bit bent and they still are nowhere near the bar.(5'11" 100Kg)

thumbnail_img_06361.jpg and

The seat in the picture is an XL Tillett and there's plenty room to fit
Safety Devices were keen to try to get seat fixation as close to FIA standard as possible. Absolute compliance with the up to date standards is, for many reasons, impossible in an Elan. What they settled on was a welded in seat bracket
thumbnail_img_0489.jpg and

Re: 26R Chassis mods vs rollcage

PostPosted: Mon Dec 24, 2018 5:24 am
by vstibbard
Looks very nice indeed, though I'd thought the footwell would have been better if triangulated to help stop it lozenging if front qtr hit. I did one like this 15 years ago but the overall weight in CDS as was required was frightening.

I do like it not relying on the sill bar, I've got sill bars in mine which makes for interesting and fiddly fitting. We're working on cross bar to bolt upper column mount to at moment to give more positive support to the column and dash.


Re: 26R Chassis mods vs rollcage

PostPosted: Mon Dec 24, 2018 8:03 am
by Frogelan
I popped up to TTR last friday and was shown the new cages (on a screen, not built up).

As suggested by Vaughan, the front part of the cage is indeed triangulated (along the side) to protect against lateral intrusion (see Graeme's top photo which shows the front of the cage) . but it will be difficult to add much more frame as there is not enough space (unless you get rid of the pedal box!).

Safety Devices / TTR now have 4 cages, the old 1993 version, a clubmans cage (not clear if this will be FIA approved), a "T3" and "T4" (a "T3" with even more tubes). If you have a closer look at the side of the T3 and compare it with a Lotus XI chassis (or the roof of a factory with north lights...) there are similarities!

I was told that the cross bar was optional, but there may be some additional uses for it as described by Graeme (mounting the steering column, larger cup holders and current handbags ?).

The main changes compared to the 1993 cage are the linear metres of tube and the "one piece" construction: it will be sold completely built up and slides into place (assuming that the interior is stripped) and is the bolted through the body/chassis.

Re: 26R Chassis mods vs rollcage

PostPosted: Mon Dec 24, 2018 3:56 pm
by 661
As said, it's tricky to get much more metalwork in around the footwell without turning the car into a hand controlled vehicle!

48180407_2112135308806954_1154120990188371968_o.jpg and