Improving Griffith and chimp chassis

[lancelin]

I came across the video below and was a bit disappointed to hear the comments about the poor Griffith chassis. See 5:02 onwards.

https://m.youtube.com/watch?v=lqTbdmbL7mU

Is this really the case? Is it possible to measure the flex? Perhaps jacking it up at one corner and measuring the twist. I wonder what can be done. I don't want a roll cage but might consider a modified chassis. Why on earth didn't TVR do this in the first place.

Harry talks about the outriggers not working but looking at the configuration it doesn't look like they were intended to help stiffness.

Any thoughts welcome

[andy43]

http://www.sportmotive.com/evochassis.html
Job done!

[The Surveyor]

lancelin said:

......

Any thoughts welcome

Thoughts... the Griffith and Chimaera chassis was perfectly sufficient for the car at the time. It was made to a weight, and to a cost, and is relatively simple in nature. Like most 20 year old designs, there is scope for improvement but any shortcomings with the design are likely to be overshadowed by tired suspension and 'thinned' chassis tubes due to corrosion.

[lancelin]

Yep, you could be right. I wonder how other cars of that era compare in terms of flex.

[Classic Chim]

Overall I think they are quite solid.
Modern tyre's work wonders in smoothing out some of the skittish nature and mask some of the flex/ imperfections you often feel just by offering huge levels of grip as does high class suspension and good bushes.
I've come to feel mines a big old solid thing and probably as strong as any Chassis of equivalent age. I like the meaty chassis Tvr employed.

[TA14]

The Surveyor said:

Thoughts... the Griffith and Chimaera chassis was perfectly sufficient for the car at the time. It was made to a weight, and to a cost, and is relatively simple in nature. Like most 20 year old designs, there is scope for improvement but any shortcomings with the design are likely to be overshadowed by tired suspension and 'thinned' chassis tubes due to corrosion.

A good summary although even at the time they were thought to be a little too flexible. Lotus were thought to have even more flexible chassis. I suppose an alternative would have been to go the Sportmotive way with more tubes, larger dia, thicker tubes, change the geo slightly; whilst this creates a stiffer chassis it adds weight not so good for dynamics. Over the next 15 years TVR improved the chassis by making it even taller (the griff was tall compared to the wedge which was tall compared to the M ... ) and bracing with lightweight panels (carbon fibre and al honeycomb - a development of early Vixen construction although that may have been accidental) which is a theme copied by the new TVR albeit now with cardboard honeycomb If you were doing a restoration a few gusset plates and carbon/glass woven mat (and honeycomb?) wouldn't be too hard to add.

[350Matt]

how much is the sportmotive chassis anyway?

and does anyone on here have one ?

[TA14]

IIRC a standard chassis is about £5K and the Sportmotive one is about £15K; note that because of the suspension and hub changes the latter comes with a lot of shiny bits so it's not a like for like comparison.

[eff eff]

I've got one

[Dominic TVRetto]

I posted this almost identical question less than a week ago with some thoughts here, and got virtually no replies...

Speaking to one of the ex-TVR Le Mans mechanics, his thoughts were that bracing the open underside of the backbone would help - but doing that in a manner which would provide extra structural rigidity whilst maintaining access for the various parts that might need to come out for repairs/servicing etc is a logistical challenge...

Still believe there is more that could be done for that one than simply a beefed-up version of the exhaust plate...

[ecs0set]

"The worst structural rigidity of any car put on the McLaren rig".

How many non-race cars do you think had been put on the McLaren rig at that point?

[TA14]

ecs0set said:

"The worst structural rigidity of any car put on the McLaren rig".

How many non-race cars do you think had been put on the McLaren rig at that point?

IIRC quite a lot. When they designed the F1 they tested just about every sports car available to them.

[350Matt]

eff eff said:

I've got one

and?

hows the handling?

[motul1974]

I'm planning a chassis refurbishment this winter and having spoken to Richard at RT, his view is that the standard chassis is more than capable of a road car, and that upgrades were only relevant on race cars.
I'd like to look into a roll hoop at the same time he's refurbing it,as I think that a hoop has surely got to offer the biggest single effect to the handling without trying to reinvent my own chassis.

[TA14]

motul1974 said:

I'm planning a chassis refurbishment this winter and having spoken to Richard at RT, his view is that the standard chassis is more than capable of a road car, and that upgrades were only relevant on race cars.
I'd like to look into a roll hoop at the same time he's refurbing it,as I think that a hoop has surely got to offer the biggest single effect to the handling without trying to reinvent my own chassis.

I'd say Ohlins would take that accolade.

[MikeE]

motul1974 said:

I'm planning a chassis refurbishment this winter and having spoken to Richard at RT, his view is that the standard chassis is more than capable of a road car, and that upgrades were only relevant on race cars.
I'd like to look into a roll hoop at the same time he's refurbing it,as I think that a hoop has surely got to offer the biggest single effect to the handling without trying to reinvent my own chassis.

I don't think a roll hoop would add anything to the chassis rigidity, you'd need a roll cage to achieve meaningful improvements, which is why TVR starting building their FHC (Cerbera, T350 and Sagaris) models with cages

[motul1974]

...a hoop with chassis pick up points, but not a cage that goes forward to the A post.

[TA14]

motul1974 said:

...a hoop with chassis pick up points, but not a cage that goes forward to the A post.

sounds like more for decoration

[deeen]

TA14 said:

motul1974 said:

...a hoop with chassis pick up points, but not a cage that goes forward to the A post.

sounds like more for decoration

Imagine a square section tube, with open ends. Imagine that if you grasp each end firmly, you can twist the tube. Adding a single hoop perpendicular above it will not stop the twist.

[eff eff]

350Matt said:

and?

hows the handling?

It handles very well, difficult to quantify as I can't do a back to back comparison only having one car. It feels more stable and predictable in fast corners the turn-in is sharp, there is less understeer and it's better behaved on uneven roads.

I'm not an automotive engineer but I think chassis stiffness is only one factor in the ride and handling story. From my understanding the Sportmotive Evolution chassis as well as addressing chassis stiffness also addresses the basic suspension geometry, the anti-roll bars and the springs and damper rates and pick up points.

TVR used off the shelf donor suspension parts for the Griffith and Chimaera, one example is the front uprights from Ford. These have a kingpin axis angle of I think 13 degrees suited to a McPherson strut. The TVR double wishbone set up needs less kingpin angle to optimise performance, the T cars have a single figure kingpin angle and so for the same basic suspension geometry handle better than the earlier cars. The Evolution kingpin angle, given by a bespoke billet upright, is set to work with the revised suspension geometry, but this again is just one part of the design. You also have to factor in increased height damper pick up points, bespoke dampers and springs, revised anti-roll bar pickup points and spring rates, fully adjustable wishbones for camber and caster adjustment.
As I said I'm not an automotive engineer and don't pretend to understand all the factors involved in steering and suspension performance which I found quite complicated, What I can say is that the chassis looks right feels right and so probably is right. Ian at Sportmotive does understand this stuff and explains it way better than I can.