Chassis refurbishment and modifications

[SSPPGG]

I may shortly undertake a restoration of a 93 griff, and would welcome some advice from the "knowledgable collective. I posted the same query on the griff forum, but it was suggested that i may receive more comments on this forum.....

I've had a couple of chimaeras before, and used various tuscan chassis and suspension parts in projects, and have also built and rebuilt a few cobras, so am quite comfortable with all of the mechanicals of rebuilding a chassis, and can get chassis repairs etc relatively easily.

I've also read lots of threads where for example cerbera spring mounts are relocated or additional bracing is built in the chassis to improve chassis stiffness, ....but so far, not come across anything that seems to be a "must do". I will be looking at brakes, and need to understand what options are available and the implications of hub conversions, which seem to be popular

I am contemplating a later BTR type diff in preference to the GKN diff, mainly as i have used both types on cobs before, and prefer the BTR LSD....Is that a bolt in job, or are the mounts different? (as you can tell, i've not yet had chance to remove the body).

What i want to know....is their a "list" of upgrades, or modifications that might be undertaken at a chassis build stage that would be beneficial, especially if my plans would be to increase performance (my last cob ran 550ftlb).

Thanks for any help or advice you can give

Edited by SSPPGG on Thursday 7th July 00:16

[ralphy12345]

I've seen the addition of two bracing strips (running from the adjacent chassis tubes) to give extra strength to the seat mounting points and thought that a good idea.

R

[V8NRG]

Depends on what your plans are really.
Engine mounts for different motor ?
Additional cross bracing, for added rigidity ?
Plates to mount seats to chassis and not just body ?
Change suspension mounts to better positions ? (you'll have to talk to someone more knowledgeable than me about this, but from what I’ve read getting the shock nearer to vertical is beneficial).

[Dr Mike Oxgreen]

When I had my chassis returbed, Nick at Willow Sportscars did a mod that created some metalwork for the seats to bolt onto, instead of just bolting onto the fibreglass floor pan:

[SSPPGG]

Thanks for the comments, and pics are most useful

Motor.

I have a plan for an LS motor, having had these engines in my last 2 cobras...(can i ask that the thread doesn't get into a right or wrong engine in a griff discussion)....i've had that debate in my head a hundred times and any more will just make my head hurt.

Engine mounts for different motor

i've seen that it is possible to use the original mounts with some brackets made by a company in Stafford, so plan to keep the mounts as is, unless someone has pics that might assist..i am really looking not to reinvent if possible ?

Additional cross bracing, for added rigidity ?

This is an area i need to understand as I am not an engineer...where might additional bracing be useful in the chassis . Where are the "weak points"


Plates to mount seats to chassis and not just body ?

I had assumed these would be like later tuscan chassis ive had, where the seats bolted through both...looking at the pic, adding a seat mount in metal seems a good idea to stiffen the floor and prevent flex.

Change suspension mounts to better positions ?
This is a mod ive seen on a couple of cerberas....I'd want to know if doing this prevent say the use of larger width rears

Drive shafts, what is the torque limit on current, what are the best upgrade options

again, thanks for the help

[spend]

The GKN & BTR do require different details.

Early chassis ~ like yours probably can have various differences. In very early chassis the side mounts for the diff 'float' (ie they are not retained at the bush face - only the centre, so poly bushes would just run along the chassis tubing..). Some reckon the roll bar pick ups are missing on the early chassis and the Griff may miss the rear ARB mounts (mine had both of them).

There is of course the big difference for the gearbox but if you retain the LT77 no changes would be required.

Various theories abound for stiffening the backbone against torque twist & flex, the main solutions being creating larger volume triangulation (bigger wire boxes for increased leverage - just like the roll bars stiffen the chassis) and addition of thin plates across sections. I've not seen anyone use the equivalent of tension wires diagonally, but neither of those techniques address the backbone twist which is the main problem to address anyway IMHO.

Personally I'd be looking at proper triangulation at each end of the outrigger, it just looks like a hanger at each corner rather than a tetrahedron, yet done & said all the factory rollbar design seems to me to be the best way to address that. There are limited ways you can add members due to external bodywork or internal drivetrain, making a long levered external shape that triangulates back bone & outriggers appears to result in the best way of stiffening up the chassis to me. The rollbar is far more beneficial in integrating the outriggers into a big spaceframe around the backbone, as well as offering some extra side protection, than it's perceived major purpose in the event of a roll?

[haircutmike]

SPG, told you the chim forum would be usefull .

[.Mark]

Dr Mike Oxgreen said:

When I had my chassis returbed, Nick at Willow Sportscars did a mod that created some metalwork for the seats to bolt onto, instead of just bolting onto the fibreglass floor pan:

That has to be one of the most sensible mods I've seen. Makes you wonder why the factory didn't do it.

[haircutmike]

I agree, my local MOTers couldn't believe it was all down to big washers!

[SSPPGG]

haircutmike said:

SPG, told you the chim forum would be usefull .

thanks chap!!

[SSPPGG]

So my list of chassis considerations (apart from any grot and rot) is

GKN to ATB diff mount differences
Seat mounts
checking gearbox mounts can work with the TKO (LS will break an LT77.
ARB mounts
Additional triangulation
shock top mount.

If anyone has any good images tucked away of any of these modifications I would be grateful

[jfjfjf2]

Have a look at www.sportmotive.com They're doing what you are talking about. See Chassis and Evolution chassis. If you speak to them I would be interesting to know how they are getting on with the Evolution chassis.

Julian

Edited by jfjfjf2 on Saturday 9th July 00:05

[DonkeyApple]

I've assumed that the problem is twist along that long and narrow spine. The angles of the out riggers just look too 2D to be of much use which is why I guess the only low cost and simple solution is the rollcage.

However, to date all discussions have been about welding extra metal in to try and stiffen and avoid an unsightly cage.

There is possibly the space to do this and initial cost needs to be ignored but a carbon fibre tunnel insert with flanges extending out the sides and front and rear flanged face plates bonded in would stop all twisting flex dead?

This would do away with the outriggers as they would be replaced by honeycomb board.

[ralphy12345]

ralphy12345 said:

I've seen the addition of two bracing strips (running from the adjacent chassis tubes) to give extra strength to the seat mounting points and thought that a good idea.

R

This is the very thing I was referring to:


I only wish I'd seen this before I did my refurb.

R

[SSPPGG]

jfjfjf2 said:

Have a look at www.sportmotive.com They're doing what you are talking about. See Chassis and Evolution chassis. If you speak to them I would be interesting to know how they are getting on with the Evolution chassis.

Julian

Edited by jfjfjf2 on Saturday 9th July 00:05

had a chat with Ian at sportmotive, , the new chassis is coming along, but in reality is likely to be more costly than i wish to expend on my hobby car. Not to say its OTT, but not for my budget being very much a hands on chap.

I am probably going to ask them to update diff mounts etc, as they have appropriate jigs to do so.

[SSPPGG]

jfjfjf2 said:

Have a look at www.sportmotive.com They're doing what you are talking about. See Chassis and Evolution chassis. If you speak to them I would be interesting to know how they are getting on with the Evolution chassis.

Julian

Edited by jfjfjf2 on Saturday 9th July 00:05

had a chat with Ian at sportmotive, , the new chassis is coming along, but in reality is likely to be more costly than i wish to expend on my hobby car. Not to say its OTT, but not for my budget being very much a hands on chap.

I am probably going to ask them to update diff mounts etc, as they have appropriate jigs to do so.

[dbv8]

That seat bracing looks overcomplicated to me.
And who cares about the passenger!