E type Roll Centre and Handling

[mgcjag]

Dont hold your breath Geoff......i think all we will see is computer modeling......the cars in Australia awaiting major rebuild.....Clive i assume is in Thailand.....a basic starting point would surelly be to fully understand the build of an E type ......for that you really need one in front of you.....Clive has already dismissed the race modifications currently used......Steve

[Gfhug]

Steve, you are very probably correct, you often are. I’m always reminded of when Clarkson et al on Top Gear tried to improve a car’s handling, changing shocks, brakes, tyres etc. and all they did was make it worse. Ok, Clive at least has the correct background to try to better their attempts.
Would Norman be rolling his eyes or smiling in amusement/interest?

Cheers

Geoff

[mgcjag]

I would like to here Clives basic thinking........is he going to remove the IRS and completely redesign the rear drive train and suspension.....or modify an IRS .........for the front is he keeping the frames and torsion bars or a completely new design.....Steve

[Series1 Stu]

None of it really matters!

Whatever Clive does may or may not make a difference, possibly for the better, possibly not. However, it will be different from standard and therefore less desirable for most future custodians.

Professional suspension engineer or not, the car will be viewed as wrong by the industry.

So far, Clive has not said anything that has made me realise that he is full of knowledge and experience. No knockout punch.

Regards

[PeterCrespin]

So far, Clive has not said anything that has made me realise that he is full of knowledge and experience. No knockout punch.

Looking back at who-said-what, I'm slightly surprised to see it was Clive who asked the questions in paras 2&3 of post #25. By the time I pressed 'Submit', a couple of others had responded the same as I did and I was quite surprised to note it was Clive asking what seemed like pretty basic structural questions. As someone pointed out, engineering the bouncy bits should be done in the context of the stiff boxy structures to which they are fastened.

However, I totally understand the appeal of tinkering and changing, as one look at my avatar confirms. It's certainly more interesting than paint and trim discussions, albeit in the end perhaps less objective than we assume.

[CliveR]

So far, Clive has not said anything that has made me realise that he is full of knowledge and experience. No knockout punch.

Looking back at who-said-what, I'm slightly surprised to see it was Clive who asked the questions in paras 2&3 of post #25. By the time I pressed 'Submit', a couple of others had responded the same as I did and I was quite surprised to note it was Clive asking what seemed like pretty basic structural questions. As someone pointed out, engineering the bouncy bits should be done in the context of the stiff boxy structures to which they are fastened.

However, I totally understand the appeal of tinkering and changing, as one look at my avatar confirms. It's certainly more interesting than paint and trim discussions, albeit in the end perhaps less objective than we assume.

Hello Peter, I phrased those questions in a carefully neutral manner to avoid pre-loading the answers. It's unfortunate that gave an impression of ignorance. I'll try to redress that in responses which I owe you and others. My goal is not to deliver any knockout punches of hitherto unseen wisdom, I want to gather experience from people who are familiar with these cars to guide me in my project. I respect the collective knowledge here and understand my views and plans raise eyebrows and hackles. I appreciate the time members have taken to respond, I will pass back my comments as long as that seems to be useful. I hope that explains my direction, in my next post I'll get back to boxy and bouncy bits and will, I hope, be more interesting than this.
Wish you a good day / evening.

[CliveR]

I am far too lacking in knowledge to comment on the efficacy or otherwise of any suggested improvements described above. However, I do come back to a view I've expressed before about what, in my view, is one of the important purposes of buying an E Type. That is, to drive and experience a 50+ year old car.
If I want a car that can handle and go like a modern supercar on a race track, I'd go out (as I do!) on the racetrack in my F Type.
If I want a car with an incredible degree of comfort I'd buy a modern luxury limo, or go out in my XF.
But I drive my E Type warts and all to enjoy it as it was.
It is of course a personal choice if people want to change their car, and I respect that. But to me, buying an E Type and making radical changes such as some of those described above is simply trying to give the driver a modern car and ride in something that looks like an E Type, but isn't really. It might as well be a kit car.
Just my view I know.

Hello Malcolm,
I respect that view while my working background allows me to see a car as a work in progress that can always be improved. I'm doing this to help a friend who recently rebuilt a Roadster to a high level and wants to extend the dynamic performance of his newly-acquired FHC. I agreed to help him because I feel that would be appropriate for such a wonderful car. I would not be doing this if I felt the result would be incongruous. I understand many view this as desecration, to me it's a positive gain to expand the car's capability to a new level. Yes, he could buy an F Type as you have, but he's chosen to go this route. I hope we can respect our differing viewpoints and learn from each other.
Best regards

[CliveR]

I would like to here Clives basic thinking........is he going to remove the IRS and completely redesign the rear drive train and suspension.....or modify an IRS .........for the front is he keeping the frames and torsion bars or a completely new design.....Steve

Basically...yes, yes, yes ....no.....no, no, yes...Clive

[mgcjag]

Thanks for the reply Clive....i was initially interested but if your doing away with the IRS, front frames and torsion bars im not anymore. .....all the best....Steve

[rswaffie]

Bad things can happen if you try and re-design the front and rear suspension.

[Gfhug]

You could also change the engine to a modern V6 diesel, after all you’re creating Frankenstein’s monster why not go the whole hog?

Geoff

[CliveR]

Bad things can happen if you try and re-design the front and rear suspension.

Not like that, I promise!

[CliveR]

Thanks for the reply Clive....i was initially interested but if your doing away with the IRS, front frames and torsion bars im not anymore. .....all the best....Steve

I understand Steve. The original intent was just simple mods and upgrades but we kept seeing new "opportunities", so we are going a lot further. I do think some of the things we've found along the way might have more general interest or application. For example, I'm sure the front frames could be improved in the way they manage load, as bolt-on items they could be installed with no permanent effect on the car. I'll post some detail on that later today. It includes the thorny question of the tube-through-the hole, for which I need to compile some pictures to support my suggestion that there is a better way. The reason I'm labouring this point is that a really good structure opens other doors as it makes the car more responsive to tuning - damper adjustments, for example. Having put the model together I can possibly suggest other simple tuning mods that others may care to try.
Thanks for your candour. I hope we could have a chat with a beer some time.

[christopher storey]

Oh, this is getting ridiculous . We have Clive R, who has a TR5 which it seems he is frightened to drive because he considers its rear suspension deficient, and yet he's done nothing about it in 25 years . Yet suddenly he is going to create something wonderful out of an E . The question which has never been answered by Clive R , although it has been posed more than once, is has he ever driven an E type , and if so which model and in what circumstances ? And what were his conclusions about its capabilities ?

[CliveR]

Surely, the shorter the wishbone, the greater the camber change for a given vertical displacement?

The driveshaft contributes to camber change in concert with the lower wishbone albeit the design doesn't allow for easy variation of geometry.

I think I have understood your post correctly so if I'm wrong I'll retire from engineering.

Regards

Please don't retire, I need my pension funded.

You understood correctly what I didn't express very well. What I should have said is that any wishbone has a limited range of vertical motion over which it will give helpful camber change (pushing the lower end of the upright outward in this case), and that range is shorter for a short link. Outside that range it works against the desired intent. I made the "short" comment with a mental picture of the central tube in the link, forgetting the fork attaching it to the diff casing. Overall it couldn't really be much longer so my comment was very academic and rather pointless. Sorry about that.

Relative to the driveshaft, it can't contribute as much to camber change as a separate top wishbone, which can be positioned at a steeper slope to make its shortness a benefit, giving a more aggressive camber curve. I'll run some curves to illustrate the point.

Cheers

Here's some supporting data to explain my comment about the rear suspension. It's a graph of rear wheel camber as the wheel rises and falls. The black line is the standard rear suspension, you can see the camber goes positive as the wheel rises in a bump motion - that translates to a reduction in cornering power at the outside wheel in a corner. Interesting also to see the curve changes direction as the wheel drops in to rebound -that could show up as a "shuffle" at the rear end over a series of undulations on a typical country road. The dotted blue line shows the effect of fitting the front upper wishbone, if such were possible, with the driveshaft now serving purely to drive the car, not locate the suspension. It improves in both areas but probably not enough to justify the effort. With a bit of juggling with the position of the inner end of the top wishbone, however, the curve changes to where we get negative camber on the outside wheel in a corner (green line). More cornering power and better use of the tyre, I would call that an improvement.

[Gfhug]

Clive, a general forum guidance is not to overly quote, even if you do need to reference someone else’s words you can edit that down to a few words or sentences. It takes up a lot of server space.

Geoff

[mgcjag]

Clive...i dont follow your graph.....on an E type rear end jacked off the ground with wheels hanging fully down the wheels will have positive camber. ........as you raise the wheel it will become more negative. ........Steve

[CliveR]

Oh, this is getting ridiculous . We have Clive R, who has a TR5 which it seems he is frightened to drive because he considers its rear suspension deficient, and yet he's done nothing about it in 25 years . Yet suddenly he is going to create something wonderful out of an E . The question which has never been answered by Clive R , although it has been posed more than once, is has he ever driven an E type , and if so which model and in what circumstances ? And what were his conclusions about its capabilities ?

Chris,
There are rather more fundamental reasons I haven't driven my TR lately. This picture was taken in the Norfolk barn where I left it in 1991 when Lotus sent me to work with GM in Detroit. I haven't lived in UK since, as I moved to work in Shanghai in 1999, then Thailand in 2015. My intent was to return and fix it after I retired but other things got in the way. My wife was diagnosed with Stage 4 cancer in 2019, since when we've been unable to travel due to her treatment. We are currently marooned in "Covid dark red" Bangkok for her chemo session no. 31 while our dream retirement home on an island in the south sits empty. This is why I agreed to help my friend plan his E-type restoration, I thought it would be therapeutic. It's also why I've been unable to drive his car In Brisbane. Meanwhile I'm working from models and charts, as I was trained to do by some of the best people in the business. I'm confident I can do that, I'll be happy to send updates as we progress if there is a positive side to doing so. If it's better I withdraw from this forum I will do so.
To answer your specific question, the last time I drove an E-type was 1972, with a friend who worked at Jaguar. He shared a house with other Jaguar people, one of whom owned a C-type which he parked on the grass verge outside their house at night. They were different times.
regards

[nichmoss]

Hello Clive

Firstly, I'm sorry to hear about your wife's illness and hope the treatment is going well.

There does seem to be something wrong with your kinematic model as that response for the original suspension design doesn't look right at all. A few points:

As noted by Steve, under droop, the rear wheels show positive camber.

It seems inconceivable that Bob Knight made such basic errors in the way the suspension would work, especially as he started with a blank piece of paper.

If anyone has Philip Porter's definitive history book, on page 285 during a review of an early race car, it was proposed that the front suspension be adjusted to provide the same camber change as the rear, namely 1.25 degrees per inch deflection. This sounds about right to me. I know my simple model didn't show that much but it was only ever meant to be indicative.

I know you don't have a rear cage in front of you so, I suspect that you have been given incorrect dimensions. Can you share the kinematic model as this is only 2D geometry with this design?

I still don't believe you have anywhere to attach an upper wishbone anyway, even if you find room. The reinforcing of the shell is only in a few locations where the cage attaches.

Regards, Chris

[nichmoss]

Just to emphasise the issue with your dimensions being incorrect. Unless very small offsets make a huge difference to the response (I can't see that) then the kinematics below are close. I just poked an extendable tape under the rear of the car and I see this - these dimensions are much more accurate and probably within +/- 10 mm.


And here, with a 50 mm down deflection so, the outside wheel on a curve and we'd be hoping for more negative camber, which is what we see.


And a graphical response:


I don't quite get the 1.25 degrees per inch that is mentioned in the PP book but, it is close. You can see that as the load comes off the wheel (so it can't do much for grip) which is the left hand side of the curve, the wheel shows slight positive camber but, for me, this is not important. As the wheel loads up, on the right side of the curve, the camber becomes more negative in a linearly fashion (more or less) and this is what I would expect Bob Knight aimed for in the design.

If you see any errors, let me know and I hope this helps a little.

Cheers, Chris