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grahamw48

9,918 posts

125 months

[news] 
Monday 8th October 2012 quote quote all
In my simple layman's mind I tend to liken a monocoque to the construction of an egg shell, whereas the backbone chassis is a bunch of drinking straws stuck together (with associated strengths and weaknesses).

Anyway, that keeps me linked in to this most interesting topic. biggrin

Chilliman

Original Poster:

5,449 posts

48 months

[news] 
Monday 8th October 2012 quote quote all
Right, I've now read through all the posts again and reviewed the test info from the Cranfield boys, and have the following question: What will be the best shocks/springs combo and geo setup for the Chim following the mods I'm about to undertake which will increase my cars torsional stiffness by 500%? Also, If I get the right setup will I really be able to corner 5 times faster than I can at the moment? In order to make the most of this highly impressive new (500% more) cornering speed will I need to do neck exercises like the F1 boys do, or is there a commercially available neck brace that I can get at somewhere like, er, say Boots? Also, will I need to get the sump baffled so all the oil doesn't go to one side of the engine when I'm taking the roundabout at the end of my road at, hang on while I work it out, umm, ah yes, 150mph? And lastly, any suggestions what tyre pressures I should be running?

Thanks in advance,

Chilli smile

Quietlybonkers

9,162 posts

31 months

[news] 
Monday 8th October 2012 quote quote all
You forgot to ask what brand of 15 inch wide slicks you should be running.....

RichardD

3,449 posts

132 months

[news] 
Monday 8th October 2012 quote quote all
Chilliman said:
Right, I've now read through all the posts again and reviewed the test info from the Cranfield boys, and have the following question: What will be the best shocks/springs combo and geo setup for the Chim following the mods I'm about to undertake which will increase my cars torsional stiffness by 500%? Also, If I get the right setup will I really be able to corner 5 times faster than I can at the moment? In order to make the most of this highly impressive new (500% more) cornering speed will I need to do neck exercises like the F1 boys do, or is there a commercially available neck brace that I can get at somewhere like, er, say Boots? Also, will I need to get the sump baffled so all the oil doesn't go to one side of the engine when I'm taking the roundabout at the end of my road at, hang on while I work it out, umm, ah yes, 150mph? And lastly, any suggestions what tyre pressures I should be running?

Thanks in advance,

Chilli smile
What would be required are gravity adjustable dampers which can increase the downforce by 500%. This would help with cornering force. However due to limititations such as "living in the real world" these are not available as per currently. Plus if they did, they could be expensive!

How about another one.

Two cars, same engine, same setup, same suspension - both are on a rally stage, a twisty bumpy b-road. Which one would be more stable over bumps? The base chassis or the one with the cage and massive stiffness increase?

I don't particularly see a clear link between stiffness and handling, stiffness allows the suspension to work more purely and so can aid stability in bumpy conditions.

If a backboned chassis TVR had 2000lb/in springs and went over a fairly large bump. How much wheel deflection would be down to suspension movement and how much to chassis twist.



SILICONEKID340HP

12,115 posts

118 months

[news] 
Monday 8th October 2012 quote quote all
jwoffshore said:
Seems to have drifted somewhat off the original topic..... It is intended that the Evo chassis will be torsionally stiffer than the original, but limitations inherent in a tubular backbone with a open top car mean it's never going to be as stiff as a modern GT. Unfortunately the TVR body design does not allow for anything structural in the sills. However, by redesigning the suspension with higher roll centres, (which TVR themselves did incrementally from one model to the next) hopefully we can use softer springs and put less twisting loads through the chassis. That's the idea anyway!!

I'll be seeing some more of my build next week. Maybe see if I can get some better pics....
So what do you think of the Gaz Mono Tube 400/500lb spring setup for road use ?
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Bluebottle

3,141 posts

127 months

[news] 
Tuesday 9th October 2012 quote quote all
lots of intelligent words, and anything with Niel Anderson's name attached is beyond rebuke.
That being said, seat of the pants feel is what you want right? well from my experience, if you have ever driven a tuscan racer at speed you will know that the tuscan chasis is...well, quite frankly Pants!, you take it by the scruff of the neck, and ring it!...it bounces, bobs and generally feels awfull unless you ring it's bloody neck then it come alive!...the Griff/chim on the other hand feels completely deferent even with the factory stated 340 bhp it feels quite stable until you compare it to a tuscan chasis with a rigid sag/hard top shell, now you start to understand how different, different can be...A stock chasis with the aid of a more rigid bodyshell & welded roll cage, means that the suspension has to do more of the work and not just some of it, the typical road car t/d setup (even fast road) has way too hard a spring rate, IF, the chasis was even moderately rigid!, even a good road setup is based on the chasis, as well as the tyre wall providing some/most of the suspension complience and the arb is vitally important in this setup.
All suspension is a compromise, but what you are looking for is a prodictable response at the limit of what the chasis will yeild and the tiv is good at this. The TVR chasis yeilds too easily so, you increase the spring rate and beef up the arb to compensate...so for the average user with the research of all the aftermarket providers, it feels bloody marveluss, until, you try a car that has more chasis rigidity and then, you soon realise that, a rigid chasis makes the suspension do more of the work more predictively giving you more cornering speed, as it spreads the load better between the four wheels forcing more of the load to the inner wheels.
However even a good a suspension setup, when pushed to the limit WILL, eventually cock a wheel and let gow, its at what speed/lateral force that this happpens, and clever suspension setup can mask a lot of the chassis failings, its not until you drive a car with a more rigid chassis that you realise that the limit can be much more than a std setup can deliver. this means significantly higher cornering speeds, and more predictable/complient handling carractoristics.
All chasis will will yeild at some point and its how predictable it does it that makes a fast or dangeruous chasis personally i like a chasis that flexis predictably, it easy to catch and control and you can play with it with confidence..i've driven plenty that are so rigid, that when they let go there is no margin for error.
All this above is complete bks and im pished, but my car will keep a gtr3rs honest on track and made a tuscan racer feel slow at silverstone until, i drove a sagaris racer! then i realised just how much more speed you can carry into a corner with a well setup up "Rigid" chassis!


Edited by Bluebottle on Tuesday 9th October 00:15

slideways

3,244 posts

108 months

[news] 
Tuesday 9th October 2012 quote quote all
Bluebottle said:
All this above is complete bks and im pished
It's ok I had my beer googles on when I read it! It made perfect sense to me.drunk

RichardD

3,449 posts

132 months

[news] 
Tuesday 9th October 2012 quote quote all
Bluebottle said:
Stuff
Lots of great detail on chassis/tracks biggrin.

(Hopefully leaving this topic.... on topic)

Before many started getting worked up about how stiff (or not) their motoring symbols of manliness are - the idea here is for an evolution for a road car (as stated by JW on Sunday). Which isn't all about stiffness and grip, more of refinement, confidence and predictability (a la T-cars)

As a sidenote, perversely, I'd say the Griff suspension is more "race car" like than latter TVRs (ignoring the Sagaris) !

Chilliman

Original Poster:

5,449 posts

48 months

[news] 
Tuesday 9th October 2012 quote quote all
Being serious for a moment (not easy for me), It is, for me, all about how much fun I can have driving my car, in particular on empty B roads where I can drive it through the twistys with some gusto, knowing what its limits are (and mine) and driving within them (or on the edge of them), knowing that it's not going to spit me out if I get it slightly wrong. Under these circumstances the occasional hanging the back out a wee bit, a tad of wheelspin powering out of the corners, and that glorious noise are all I need to keep that stupid grin on my face. It's all about understanding the balance of the car, knowing what its going to do next, and being ready for it that's more important to me than being able to carry more speed through a corner than the bloke behind me in his super stiff GT whatever. They all shrink to a small dot in the rear view mirror when we hit a straight anyway wink

500dread

195 posts

30 months

[news] 
Tuesday 9th October 2012 quote quote all
RichardD said:
the idea here is for an evolution for a road car (as stated by JW on Sunday). Which isn't all about stiffness and grip, more of refinement, confidence and predictability (a la T-cars)
You're spouting to the masses with such a fine statement - and whilst I'm sure your statement may well prove to be pretty much spot on, it is rather an obvious one to make. What it doesn't get across, and pretty much nothing said yet in this topic does, is not so much what is wrong with the Griff chassis but more, why would a Griff owner want to give their car this level of refinement, confidence and predictability you speak of?

To me some of the Griffs appeal is its rawness. If I had a T350 that felt like a Griff I'd think it was a bit of a heap. But I'm not sure I'd want my Griff to, let's say 'feel' (as a broad sweeping sword description) like a T350 as I'd be afraid it would lose much of its raw appeal. If this is what a Sportmotive type chassis running the T-car set up is going to bring, me personally I'd just rather use the cost of a conversion, sell the Griff and buy the T-car.

I don't see the Sportmotive chassis as a viable conversion for Griffs that need a chassis change or serious repair. I do see it as a serious upgrade for handling to match performance of heavily modified Griffs and perhaps my thoughts might help answer the op's first post.

This has nothing to do with how manly my Griff makes me feel. Or at least I don't think it does!





jwoffshore

341 posts

141 months

[news] 
Wednesday 10th October 2012 quote quote all
Well, I had a good visit to Sportmotive this past day to discuss the progress of my car. I could post some pics showing how much better the LS engine fits in the Evo chassis compared to squeezing it into the standard one. However, this topic has now drifted so far into Roger Irrelevant territory that I don't think it's worth the bother! It's still at the engineering rather than finishing stage, so doesn't look very pretty anyway, but if anybody is interested you can pm me.

450Nick

3,671 posts

99 months

[news] 
Wednesday 10th October 2012 quote quote all
Bluebottle said:
lots of intelligent words, and anything with Niel Anderson's name attached is beyond rebuke.
That being said, seat of the pants feel is what you want right? well from my experience, if you have ever driven a tuscan racer at speed you will know that the tuscan chasis is...well, quite frankly Pants!, you take it by the scruff of the neck, and ring it!...it bounces, bobs and generally feels awfull unless you ring it's bloody neck then it come alive!...the Griff/chim on the other hand feels completely deferent even with the factory stated 340 bhp it feels quite stable until you compare it to a tuscan chasis with a rigid sag/hard top shell, now you start to understand how different, different can be...A stock chasis with the aid of a more rigid bodyshell & welded roll cage, means that the suspension has to do more of the work and not just some of it, the typical road car t/d setup (even fast road) has way too hard a spring rate, IF, the chasis was even moderately rigid!, even a good road setup is based on the chasis, as well as the tyre wall providing some/most of the suspension complience and the arb is vitally important in this setup.
All suspension is a compromise, but what you are looking for is a prodictable response at the limit of what the chasis will yeild and the tiv is good at this. The TVR chasis yeilds too easily so, you increase the spring rate and beef up the arb to compensate...so for the average user with the research of all the aftermarket providers, it feels bloody marveluss, until, you try a car that has more chasis rigidity and then, you soon realise that, a rigid chasis makes the suspension do more of the work more predictively giving you more cornering speed, as it spreads the load better between the four wheels forcing more of the load to the inner wheels.
However even a good a suspension setup, when pushed to the limit WILL, eventually cock a wheel and let gow, its at what speed/lateral force that this happpens, and clever suspension setup can mask a lot of the chassis failings, its not until you drive a car with a more rigid chassis that you realise that the limit can be much more than a std setup can deliver. this means significantly higher cornering speeds, and more predictable/complient handling carractoristics.
All chasis will will yeild at some point and its how predictable it does it that makes a fast or dangeruous chasis personally i like a chasis that flexis predictably, it easy to catch and control and you can play with it with confidence..i've driven plenty that are so rigid, that when they let go there is no margin for error.
All this above is complete bks and im pished, but my car will keep a gtr3rs honest on track and made a tuscan racer feel slow at silverstone until, i drove a sagaris racer! then i realised just how much more speed you can carry into a corner with a well setup up "Rigid" chassis!



Edited by Bluebottle on Tuesday 9th October 00:15
Err I thought that most of the Sag racers were just Tuscan Challenge cars with different body shells sat on top? Apart from some minor changes including bracing between the front suspension pickup points there is (as far as I'm aware) very little difference in the chassis. The differential cornering speed is due to the wider rubber adding mechanical grip, then roof and aero generating downforce and giving the car a more planted feel.


Graham

15,380 posts

171 months

[news] 
Wednesday 10th October 2012 quote quote all
450Nick said:
Err I thought that most of the Sag racers were just Tuscan Challenge cars with different body shells sat on top? Apart from some minor changes including bracing between the front suspension pickup points there is (as far as I'm aware) very little difference in the chassis. The differential cornering speed is due to the wider rubber adding mechanical grip, then roof and aero generating downforce and giving the car a more planted feel.
Not quite they run a very different roll cage with much more bracing that adds a lot more stiffness to the chassis, and then most have extra bracing on the main chassi too.

at least 2 of them also have the motor solidly mounted to act as a bit of a stressed member. they do share the same basic chassis but the over all package is much stiffer.

Thats why the sags dont wave a front wheel in the air..

DarkMatter

1,172 posts

118 months

[news] 
Wednesday 10th October 2012 quote quote all
jwoffshore said:
... I could post some pics showing how much better the LS engine fits in the Evo chassis compared to squeezing it into the standard one....
I've enjoyed following this thread with the different opinions expressed but I'd also like to see the pictures you have, perhaps you could post them in a new thread?

RichardD

3,449 posts

132 months

[news] 
Wednesday 10th October 2012 quote quote all
500dread said:
Stuff
For starters I am glad the "s" or "r" words haven't been used, so I'm not going to mention them either biggrin.

You've stated you are happy with your Griff, that's great. I was happy with mine (including 50 instead of 55 profile front tyres (from previous owner) which I'm sure made it better (certainly than a friends pre cat 400)), before it got taken to bits to start rust removal!

The refinement bit is a tad overstated I think, the ability to have a flatter cornering car without having to make the suspension stiffer, can't be a bad thing for safety on a car that sees bumpy b-roads.

The whole project has been done with LS conversions in mind, it would be overkill imho for RV8 cars especially as the majority will value originality. So I guess we agree there!

Other things possibly not mentioned yet - the gearbox as per the chassis pic earlier, the "magnum" box is like a T5 close ratio (2.66 instead of 3.0 first gear ratio), but it also has a 6th gear (being a variant of the T56). So 40+ mpg potential for a efficient LS engine. Again, not relavent for a RV8.

Plus the option of "normal" exhaust routing - ie not going forward and frying the alternator and turning the engine bay into an oven...

Finally, I remember buying the Autocar with the Griff road test. The over-riding memory of it was "so close to greatness it hurts". This has always bugged me.

DonkeyApple

17,436 posts

56 months

[news] 
Wednesday 10th October 2012 quote quote all
RichardD said:
You haven't ruffled feathers, you have flown off on a tangent in a "my car is fine, why change anything" mindset.....

If a chassis is being made to replace an old rusty chassis, and the opportunity exists for minimal effort to add in a few more tubes here and there (to increase rigidity), then why not.
This I also at a time when forced induction and LS conversions are seeing Tivs with much, much more power than originally designed in mind.

If we are reaching the point in time when some chassis are needing replacement then 20 years on it would seem retarded not to look to use 20 years of data, experience and industry advancements to deliver a replacement which is superior to the original.

RichardD

3,449 posts

132 months

[news] 
Wednesday 10th October 2012 quote quote all
DonkeyApple said:
This is also at a time when forced induction and LS conversions are seeing Tivs with much, much more power than originally designed in mind.

If we are reaching the point in time when some chassis are needing replacement then 20 years on it would seem retarded not to look to use 20 years of data, experience and industry advancements to deliver a replacement which is superior to the original.
Indeed. The current graphs of the RV8 turbo look... interesting in the collosal torque increase from low to medium revs !

Talking of "industry advancements", here is a modelling screengrab from early days of the project. Looking at pictures has to be better than words as words go off on tangents smile

Edited to add - of a static standard Griff.



Edited by RichardD on Wednesday 10th October 09:41

DonkeyApple

17,436 posts

56 months

[news] 
Wednesday 10th October 2012 quote quote all
RichardD said:
Indeed. The current graphs of the RV8 turbo look... interesting in the collosal torque increase from low to medium revs !

Talking of "industry advancements", here is a modelling screengrab from early days of the project. Looking at pictures has to be better than words as words go off on tangents smile

I'm still intending to buy another Griff at some point. It would be a high day and holiday car so I would be more than happy to set it how I had my old Griff. A 4.3BV with Ohlins and proper alignment. It did the job for what it was but you were always 100% aware of that nasty little 'shimmy' when trying to push on down a B/C road.

The T350 was noteably more planted and confidence inspiring. Some of this came from the fact that the pedal movement was much longer for the torque delivery but it was clearly far more poised in corners meaning you took less risks to travel at the same speed as the Griff. This never meant it was any less thrilling. It was a logical evolution that allowed you to make more use of the engine's ability in the exact places which delivers thrills, the twisties.

Incidentally, I'm not sure how much the roll cages of the T350 or Sag bought to the party as weren't they basically just cosmetic stick ons more than anything?

In the Typhon, it's a different story again and one which actually brings a different perspective to this; this car has a proper cage, engine bracing and the spine enveloped in CF and honeycombe. It doesn't move. It is long and wider so more progressive and has the wider track taken for the Sag fronts, Ohlins and a good general set up.

But there is a problem. It is far more stable in the twisties meaning to get the thrill of the T350 I need to be travelling at speeds which I frankly don't think are appropriate and I can't get sensible track day insurance and nor am I inclined the risk the car on a track day. So, in a perverse way, there is a school of thought that my T350 was the perfect TIV for me. More thrilling than the Typhon for how I want to drive an use it. And more thrilling than the Griff as it dealt with some significant thrill sapping niggles.

If the chassis were shot on a Griff/Chim or I was going for a big output engine then I would think myself silly not to fit a superior design chassis.

But also, the thought of being able to post a Griff through the twisties at the same ease as a T350 is extremely appealing.

saxon

166 posts

137 months

[news] 
Wednesday 10th October 2012 quote quote all
Can I say that what concerns me when driving my Griff is not the stiffness of the chassis but the complete absence of side intrusion protection sitting that low down behind a flimsy fibreglass door and a bit of carpet and with a backbone girder on the other side.

I applaud any attempts to make the chassis better, but I think my main concern as a keen driver, Dad and husband is safety, not shaving a couple of seconds off a lap at Brands.

The main thing that makes me occasionally look at selling the Griff is the thought of replacing it with something rewarding to drive but safer - Honda S2000? Toyota GT86? heck even an MX5 or a 2.8V6 Saab 9-3 convertible chipped for 300BHP. The other thing that makes me consider selling it is its lack of usability when the weather turns foul - poor demisting, heating, wipers etc.

Saxon

Bluebottle

3,141 posts

127 months

[news] 
Wednesday 10th October 2012 quote quote all
Graham said:
450Nick said:
Err I thought that most of the Sag racers were just Tuscan Challenge cars with different body shells sat on top? Apart from some minor changes including bracing between the front suspension pickup points there is (as far as I'm aware) very little difference in the chassis. The differential cornering speed is due to the wider rubber adding mechanical grip, then roof and aero generating downforce and giving the car a more planted feel.
Not quite they run a very different roll cage with much more bracing that adds a lot more stiffness to the chassis, and then most have extra bracing on the main chassi too.

at least 2 of them also have the motor solidly mounted to act as a bit of a stressed member. they do share the same basic chassis but the over all package is much stiffer.

Thats why the sags dont wave a front wheel in the air..
As Graham says above, plus also a full hard top body shell will be inherently more rigid to.
what i forgot to mention in my ramblings was that with the chassis torsional weakness and tyre wall comlience bieng a larger element of the suspension setup/movement over a more rigid chassis, these movements are not damped which is why many owners do not like the feel of the tiv on bumpy B roads.
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