New Sportmotive chassis

[sportmotive]

Yes you could.......

[DonkeyApple]

sportmotive said:

Yes you could.......

Thanks. I'm assuming that the upside would be to remove an awful lot of heat from the bay. Is this correct, is this a real benefit, are there other benefits?

I am interested in a replacement chassis for an old Griff that will give better driving but I don't have any intention of going for any more power than standard.

Thanks.

Tim.

[GTRene]

it would also save some weight up front I guess when taking the short route of exhaust, not much but looking at is on a positive note

[7 TVR]

Good to see the sportmotive chassis coming along!
My chassis strengthening for the LS has proved more than adequate with the car performing and handling very well over the summer on circuits like Oulton & Donny! I'm still getting a bit of chassis twist on full beans but overall very impressed with how the car is handling 500BHp.
Very interested to see how much the handling can be improved with the revised pick up points etc
One thing that i'm sure of is running the exhausts straight down is a much better option than forward, although its bloody tight on a standard chassis so more room would be great for less restriction on pipe size and bend!
Ian the Griff will be coming apart again over the winter so whens the chassis ready?????????????

[500dread]

7 TVR said:

I'm still getting a bit of chassis twist on full beans

How are you identifying twist? Even "a bit".

I assume when you get to full beans something different happens that you identify as the chassis twisting.

[jwoffshore]

DonkeyApple said:

sportmotive said:

Yes you could.......

Thanks. I'm assuming that the upside would be to remove an awful lot of heat from the bay. Is this correct, is this a real benefit, are there other benefits?

The advantages which presently spring to mind of running the exhaust down the side of the block are:
1. Takes the heat away from under the bonnet. The cats get very hot and are now relocated under the car.
2. Creates space for mounting other ancillary components as desired (e.g. LS air intake system, expansion bottle, accusump, power steering bits etc) without having to slot them in around a hot exhaust.
3. Allows extra chassis bracing tubes since we don't have to thread the exhaust through the top/front of the frame.

[sportmotive]

Tim, the real benefit is the reduction in engine bay temperature and with the LS install it just makes it easier for us to package all the ancillaries on the front of the engine and frees up space for the induction system and coolant pipes, ie. we wont have our air intake pipe running inbetween two large exhaust manifolds. I think its less critical with a Rover install so I suppose it comes down to how much you want to spend on having exhaust manifolds made.

Chris, we have four chassis in fabrication at the moment all of which are very near completion, unfortunately all are sold with deposits taken. We intend to build a car on the first chassis very soon and we will fully road test it and make any changes necessary to dampers/ spring rates and anti roll bar rates before we actually release it for general sale and even then we will probably only do in house supply and build rather than actually sell them as a retail item on their own.

[7 TVR]

500dread said:

How are you identifying twist? Even "a bit".

I assume when you get to full beans something different happens that you identify as the chassis twisting.

Yes & No you can just really feel the way the chassis reacts to a huge dose of Torque in say 2,3
Hard to describe but you just get a feeling of less forward momentum and a cross between tyre slip and the whole bloody thing wanting to eat the road!
The chassis changes from a v.rigid solid feel to something akin to being malleable if that makes any sense! [Feels very alive]
I'm running strong spring rates for the track but have still felt like there is to much body roll!
I've been told i'm on the limit of cracking things if i go too much stronger on spring rates so plan to look at stranger ARB although after owning the Tuscan challenge car i realise the Griff will always be compromised by my want for it to remain a pleasant road drive so plan to concentrate on making the car as user friendly as possible for both track/road!
Would be good to drive all the cars back to back as i'm keen to see how the new sportmotive chassis feels compared to a Griff or T350!

[bsdnazz]

GTRene said:

does a small cage like this ads some chassis stiffness?

I would expect most of the chassis flex to be in the central backbone between the two axle lines. The roll cage picture is not going to help there.

[GTRene]

me thinks so too, that one is not connected well enough to add more rigidity.

hope the new Sportmotive chassis will help a lot in that, it looks a bit "stronger"

would be nice to see some numbers, original tube ala TVR and the one ala Sportmotive when ready.

[500dread]

7 TVR said:

500dread said:

How are you identifying twist? Even "a bit".

I assume when you get to full beans something different happens that you identify as the chassis twisting.

Yes & No you can just really feel the way the chassis reacts to a huge dose of Torque in say 2,3
Hard to describe but you just get a feeling of less forward momentum and a cross between tyre slip and the whole bloody thing wanting to eat the road!
The chassis changes from a v.rigid solid feel to something akin to being malleable if that makes any sense! [Feels very alive]
I'm running strong spring rates for the track but have still felt like there is to much body roll!
I've been told i'm on the limit of cracking things if i go too much stronger on spring rates so plan to look at stranger ARB although after owning the Tuscan challenge car i realise the Griff will always be compromised by my want for it to remain a pleasant road drive so plan to concentrate on making the car as user friendly as possible for both track/road!
Would be good to drive all the cars back to back as i'm keen to see how the new sportmotive chassis feels compared to a Griff or T350!

I enjoyed reading how you describe it in layman terms as I can't say I've ever felt such myself. But then I'm not as fortunate as you are to get out on track in such beasts and get them to their limits.

For the first time in this thread your comments with regard to body roll in particular sound like they make a lot of sense. To me body roll is inherent in all the aspects that make the car do what it does the way it does, but for you to pin point body roll when you're at the limits of spring rate (and set-up no doubt) really starts to make sense as to how you are experiencing chassis limit and twisting. There was another comment earlier that I somewhat overlooked which said something about wheel lift. Combined with your findings I can picture it in my head even if I doubt I'll ever be able to get my Griff to behave in such a way on the road so as I really can feel it!

Perhaps after all the Sportmotive chassis might well bring something to the road that's not so much overkill as I first imagined.


Thank you. Much appreciated.

[GTRene]

I think for most its hard to feel, because they "think" the ride is say excellent or fine/good.

best way to feel the difference of a rigid chassis is to drive 2 cars the same day...
one with a more "twisty" chassis
and the other with a very rigid chassis.

then you feel the difference better, the shocks can do their work better and that way the car stays more planted to the road.
when a chassis gives to much (twist) it acts a bit like a spring with "no damper".

[900T-R]

Now the ultimate would be the Sportmotive geometry and strength mods with Gregor (vaurien)'s stainless steel build (assuming ductility and fatigue resistance as good as or better than the mild steel grade normally used)...

[Basil Brush]

GTRene said:

I think for most its hard to feel, because they "think" the ride is say excellent or fine/good.

best way to feel the difference of a rigid chassis is to drive 2 cars the same day...
one with a more "twisty" chassis
and the other with a very rigid chassis.

then you feel the difference better, the shocks can do their work better and that way the car stays more planted to the road.
when a chassis gives to much (twist) it acts a bit like a spring with "no damper".

Or drive a Tuscan down a very bumpy road a few times and then see how much paint has been rubbed off the door and roof openings.

Interesting about the subaru steering rack. How does the rack width compare to the Griff or later wider T car racks?

[GTRene]

900T-R said:

Now the ultimate would be the Sportmotive geometry and strength mods with Gregor (vaurien)'s stainless steel build (assuming ductility and fatigue resistance as good as or better than the mild steel grade normally used)...

would indeed be interesting and less worries...
a lot TVR owners keep their cars at home when its raining, mostly I guess because afraid of the otherwise bigger chance of rust.

you pay a few thousand more, but your car will also be more worth in the end and give's you more peace of mind

[DonkeyApple]

900T-R said:

Now the ultimate would be the Sportmotive geometry and strength mods with Gregor (vaurien)'s stainless steel build (assuming ductility and fatigue resistance as good as or better than the mild steel grade normally used)...

Hi Eric, Doesn't there come a point when flex in the mild steel actually takes strain off the join points? So, if a stainless build has less flexibility is there a risk of over stressing weld/fixing points?

[900T-R]

DonkeyApple said:

Hi Eric, Doesn't there come a point when flex in the mild steel actually takes strain off the join points? So, if a stainless build has less flexibility is there a risk of over stressing weld/fixing points?

I'd say that is plausible - although with the sort of stainless used for exhausts et al you'd sooner see cracks in the material near the welds...

I'm not a materials specialist but I'd say if you are to replicate a given structure in a different material its ductility properties should be close to the original material's ?

[DonkeyApple]

900T-R said:

DonkeyApple said:

Hi Eric, Doesn't there come a point when flex in the mild steel actually takes strain off the join points? So, if a stainless build has less flexibility is there a risk of over stressing weld/fixing points?

I'd say that is plausible - although with the sort of stainless used for exhausts et al you'd sooner see cracks in the material near the welds...

I'm not a materials specialist but I'd say if you are to replicate a given structure in a different material its ductility properties should be close to the original material's ?

Neither am I, but when you use a change of material properties to fix a problem you usually don't fix the problem just move it along to somewhere else. Hence my thinking if you'd be increasing stresses in the direct area of joins when eliminating 'elasticity'?

I think it is fair to say that at the power outputs some LS engines are capable of it would be valid to argue that you can never 'fix' a backbone chassis design.

[900T-R]

DonkeyApple said:

Neither am I, but when you use a change of material properties to fix a problem you usually don't fix the problem just move it along to somewhere else.

So I would think that if you're going to replicate a given structural design you might want to make sure that the mechanical properties of the materials used are close to the originals' - or modify the design using finite elements analysis (or simply over-engineer joins to the point that they will hold regardless).

Hence my personal conviction that at the level of knowledge and resources that defines most of us, you're probably better off lowering the loads on the structure we're given at a given longitudinal and lateral acceleration level (i.e. make things lighter, especially if unsprung and/or rotating) rather than beef up the structure to cope with higher loads (more engine torque output, higher spring rates, bigger brakes/wheels etc.).

[RichardD]

900T-R said:

...Hence my personal conviction that at the level of knowledge and resources that defines most of us, you're probably better off lowering the loads on the structure we're given at a given longitudinal and lateral acceleration level...

(More on topic and responding to the bit I've highlighted in bold)

Hence slightly higher roll centres here - to reduce the need to fit stiffer springs/dampers.