Interested in what people make of the new TVR chassis designed by Gordon Murray. I get the concept of i Stream from the point of view of it simplyfying the production process, but am unsure if this will translate into a fabulous handling car.

If one of us had come up with the design on the back of a fag packet, pretty sure it would get slated on here for lack of triangulation etc. I'm particularly drawn to the unusual front suspension pick up point arrangement, it looks crude to my eyes.

Anyhow heres a video of it.........over to you, thoughts please



https://fpdl.vimeocdn.com/vimeo-prod-skyfire-std-us/01/1567/9/232838458/825099183.mp4?token=1505355362-0x5e520b4af9a8c176400b2c249f72036570fdf29c

[Edited on 14/9/17 by Wadders]

I find the short exhaust pipes exiting behind the front wheels interesting, it should keep our feet warm and the side windows de-iced in Scotland.
(i still wonder why Ford felt the need to run the P100 exhaust all the way to the tailgate?)

Looks like the link is to an expired cache. Do you have the original Vimeo link? Cheers.

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Originally posted by Wadders...unsure if this will translate into a fabulous handling car.

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Originally posted by gingerprince
Looks like the link is to an expired cache. Do you have the original Vimeo link? Cheers.

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Originally posted by nick205

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Originally posted by gingerprince
Looks like the link is to an expired cache. Do you have the original Vimeo link? Cheers.

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Likewise the OPs video link doesn't work for me, so can't comment.

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Originally posted by Sam_68

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Originally posted by Wadders...unsure if this will translate into a fabulous handling car.

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All the chassis is, is a bracket. It transmist loads from one point to another, that's all.

So long as it is reasonably stiff, and not excessively heavy, it doesn't have major influence on handling, so there's no way of judging just by looking at the iStream chassis, whether the car will handle or not. That's more about geometry, springs and damping.

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Slight update........Try this

http://istreamtechnology.co.uk/?fref=gc&dti=22...

I'm certain that the chassis will have sufficient stiffness to perform its necessary contribution to handling.

The bigger issue with 'proper' cars (ones with doors, complex interiors etc.) is that lack of stiffness sets up all sorts of shimmies, squeaks and rattles that are unacceptable from an NVH standpoint. If you make the structure stiff enough to obviate these, it will be more than stiff enough to do its job in handling terms.

The irony is that 'our' sort of cars (basic spaceframes) are laughably limp be modern production car standards, yet they still handle acceptably.

There's an interesting parallel between the iStream chassis concept, and the Reynard Inverter, which also used a very basic, untriangulated spaceframe that was then panelised by composite sandwich panels to stiffen it.

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Originally posted by Sam_68
I'm certain that the chassis will have sufficient stiffness to perform its necessary contribution to handling.

The bigger issue with 'proper' cars (ones with doors, complex interiors etc.) is that lack of stiffness sets up all sorts of shimmies, squeaks and rattles that are unacceptable from an NVH standpoint. If you make the structure stiff enough to obviate these, it will be more than stiff enough to do its job in handling terms.

The irony is that 'our' sort of cars (basic spaceframes) are laughably limp be modern production car standards, yet they still handle acceptably.

There's an interesting parallel between the iStream chassis concept, and the Reynard Inverter, which also used a very basic, untriangulated spaceframe that was then panelised by composite sandwich panels to stiffen it.

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Originally posted by redscamp
I find the short exhaust pipes exiting behind the front wheels interesting, it should keep our feet warm and the side windows de-iced in Scotland.
(i still wonder why Ford felt the need to run the P100 exhaust all the way to the tailgate?)

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Originally posted by Wadders
Are you saying the bonded on composite panels add a lot of structural rigidity ?

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Jesus Sam, that's buggered my ipad view up

I can see how the Ginetta approach would be very stiff. It reminds me of the aluminium monocoques with steel subframes either end to hang the suspension and engine off etc. Still not sure about the effectiveness of the panels on the TVR though.

What would be the effect on a locost chassis of replacing the floors, sidepanels, footwell panels etc with say 25mm composite, bonded into the space frame ? Would there be a massive increase in rigidity, and if so would that be a good thing.

[Edited on 14/9/17 by Wadders]

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Originally posted by Wadders
Jesus Sam, that's buggered my ipad view up

What would be the effect on a locost chassis of replacing the floors, sidepanels, footwell panels etc with say 25mm composite, bonded into the space frame ? Would there be a massive increase in rigidity, and if so would that be a good thing.

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Originally posted by WaddersWhat would be the effect on a locost chassis of replacing the floors, sidepanels, footwell panels etc with say 25mm composite, bonded into the space frame ? Would there be a massive increase in rigidity, and if so would that be a good thing.

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Looking at it, then the chassis on it's own won't be all that stiff. Stiffness utterly matters for handling - if there's flex, the suspension can't follow the geometry it's been designed for. However, the hybrid approach he's gone for is intriguing.

If you take a read though "Race Car Chassis Construction" by Aird, there's lots in there. Essentially, the stiffest is the sandwich or stressed skin,. However, they're time taking and expensive to manufacture. So, we look for approximates. What we do with space frames is put in diagonals to approximate the paths of force that are achieved with sandwich panels that give the stressed skin. This is cheaper and more easy to modify that a monocoque or chassis with sandwich panels. After all, for the panel to be effective, it has to be bonded in. Ally rivets add little in this context.

I think Murray has achieved a good compromise of manufacturing ease and torsional rigidity (again, essential for handling).

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Originally posted by Sam_68

Potentially yes, and yes (which is why Gordon Murray is pursuing that strategy with iStream). Caterham already use such an approach, in a very half-hearted manner. The Reynolds Inverter has made a better fist of it, and I'm aware of several others who have successfully used the strategy to make a very stiff, light 'semi monocoque'. It's not as cheap, though (honeycomb sandwich panels are quite pricey)

So it would seem Old Gordon knows what he's doing after all . Crafty too, as it seems the panels he's using are scrap offcuts from some aviation process.....

Guess the proof of the pudding will equate to Top Gear test track or Nurburgring times, that seems to be how these things are quantified nowadays

Good luck to them i say, hope the thing spanks some arse and is a commercial success.

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PAUL FISHER - 14/9/17 at 02:26 PM

I suppose the real test is how well it handles when it's reviewed, my guess it will be superb

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Sam_68 - 14/9/17 at 02:42 PM

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Originally posted by FuryRebuildStiffness utterly matters for handling - if there's flex, the suspension can't follow the geometry it's been designed for.

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It matters, but (these days) only to a limited degree, realistically.

The textbook obsession with chassis rigidity dates to the days of simple ladder chassis and ash body frames. Remember that the likes of the early Lotus spaceframes were considered a monumental leap forward, that pretty much solved the problem... yet even they were only achieving stiffnesses of around 700-900 lb.ft/degree.

Nobody complains about the effects of lack of stiffness on Caterham's handling, yet they're only circa 2,500 lb.ft/degree, after decades of optimising and reinforcement.

You won't find many modern production cars that are less stiff than the Mk.1 MX5 (again, not usually criticised for it poor handling), and even that is about twice as stiff as the typical Locost.

Where the MX5 is criticised is for its refinement: it suffers dreadful scuttle shake, and shudders and squeaks like a shitting spaniel.

And that's the reason that manufacturers are obsessed with bodyshell stiffness - nothing to do with handling. A typical small hatchback like a Ford Focus is around four times as stiff as a Mk. 1 MX5, and about 8 times as stiff as a Locost, but you can bet your ass it's not that way because Ford wanted it to be able to lap the Nurburgring faster than a Caterham. It's because they don't want customer complaints or perceived lack of quality because the glovebox squeaks and you can hear the door seals rubbing in their frames.

If you're not interested in refinement, as most Locosters aren't, and you're not running the massively stiff suspension that's necessary for a wings-and-slicks/ground effect race car, the chassis deflections relative to the suspension deflections (never mind deflections in the tyres and bushes) are fairly trivial, so you just need to have enough stiffness (around 10 times the roll stiffness generated by your springs, is the usual rule of thumb), then concentrate on saving weight.

In short: if the new TVR lacks stiffness to the degree that it noticeably affects the handling, it would already have failed, because nobody would pay £90K for a car with that many squeaks and rattles!

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Camber Dave - 14/9/17 at 05:57 PM

Quote from Sam 68

" You won't find many modern production cars that are less stiff than the Mk.1 MX5 (again, not usually criticised for it poor handling), and even that is about twice as stiff as the typical Locost.
Where the MX5 is criticised is for its refinement: it suffers dreadful scuttle shake, and shudders and squeaks like a shitting spaniel. "


I bought an old MX 5 as a donor. I got it MOT’d for evaluation, added Protech dampers and uprated springs and was frustrated by the scuttle shake. It literally shook like a wet dog – L/H front first and diagonally to the tail.

Over the first winter I made 2mm chassis rail covers and fully welded them in.
I also made a centre cross brace and front and rear crucifixes (both removable obs!).

Car absolutely transformed. No shake and as solid as a saloon. The change in direction is instantaneous and it will even take rumble strips on Track days without shake or deflection.

Now on its 3rd year of total fun driving and the Leader is on hold till the MX 5 succumbs to rust.
There is no substitute for a rigid chassis

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