Woohoo my fist completed car post

Anyway, how do you improve high speed stability on a 7 type car? 130+mph?

I've raised the rear a little(15mm) as it was at the same height as the front(a oversight by me).

Running 6deg caster, 0.25deg toe out, 2 deg rear toe in, front 1.0 deg camber, rear 0.5 deg camber.

The car runs Ginetta G20 geometry but with wider track.

I guess raising the rear should have helped a lot.

I've not covered the whole underside of the car yet, engine bay is open underneath as is the very rear of the car.

I must say it was rock solid upto around that sort of speed, the steering just started to go light.

To be honest i think the aerodynamics of the 7 type car are its worst enemy, and there is a limit to what you will achieve. I would be bloody terrified to be doing 130 in my haynes roadster to be honest.

quote:

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Originally posted by chrisxr2
To be honest i think the aerodynamics of the 7 type car are its worst enemy, and there is a limit to what you will achieve. I would be bloody terrified to be doing 130 in my haynes roadster to be honest.

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i thought 130 was usually about the top speed for 7s?
seems you need a little force on the front, what about those little 'canard' (?) things that go on the nose, just like small wings to push the front down a little?

er...id lose the toe, but thats a personal thing, apart from that venting the front cycle wings, undertray/splitter is the best way to go, just try to minimise lift. a diffuser would also help

quote:

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Originally posted by blakep82
i thought 130 was usually about the top speed for 7s?
seems you need a little force on the front, what about those little 'canard' (?) things that go on the nose, just like small wings to push the front down a little?

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it around the 130-150 speed i think. to do with the aerodynamics, it takes a LOT more power to go much quicker.
but, flattening the bottom of the car, and a diffuser will help too

One of the best things you can do (I have read) is to modify the cycle wings to ensure that the airflow separates on the trailing edge otherwise it develops lift.

Something like this: http://www.fluke-motorsport.co.uk/carbon-fibre-csr-style-cycle-wing-suitable-for-caterhams-westfields-etc-p-1034.html

Hope this helps,
Craig.

I had pretty much the same problem, and got over it this way, (see pic), and it worked a treat. HTH Ray

[img]
Near side view [/img]

I fitted a diffuser to the rear, and it certainly made the back end feel more settled at high speeds.

However, it magnified the steering going light at 120+, so I think you'd have to do something at the front to balance it.

If I had more cash I would have looked at those carbon canards for the front nose cone plus some shaped cycle wings.

If you are putting a removable flat floor beneath the engine bay, you could extend it out at the front to form some sort of splitter / wing? Nothing massive, just a couple of inches out from the bodyline / nose??

Cheers gents for all the suggestions/ideas. I know it'll never be rock solid at silly speeds. I just want it to feel good till the acceleration dies off a little.

So far, Diffuser/undertray/vented wings all seem like bits that I can have a go at making myself.

With the stick on bits for the nose cone how much downforce can they give on a GRP nosecone that isn't rigid, I thought it might just flex?

I would also get rid of the toe-out on the front.

i have got 0.5 deg toe in on the roadster. it massively improved the high speed stability at the sacrifice of a little bit of turn in feel. mine will do 150 in 5th at which point it hits the redline. im planning to fit different diff which should give me another 10mph then i can wang the boost right up to give more torque to overcome the heavier gearing.

I had some details of those 'csr' type front wings like the ones craig1140 links to. If I remember correctly caterham claim the lift from the front wings was reduced by something like 40% at the top speed of the csr.

Regards
Hugh

My stability has improved 99% by having zero toe in,

But the thought of doing 130 mph in my 7 is horrific,

100 is well fast enough with sitting 4" off the road

I bet good money your lady hasn't seen this thread.

quote:

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Originally posted by Irony
I bet good money your lady hasn't seen this thread.

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When I'm running on track, after fitting the rear tray I moved from small from number plate to standard size. It's mounted at an angle under the nose, the change in size is noticeable above 100.

ATB Dan

Front numberplate angled back? I've not put a numberplate on the front yet as I've not decided where I want to place it, I guess this may help.

scoop

This is the small plate, it has a substantial mounting system.

Dan.

[Edited on 6/7/11 by scutter]

Surely a high top speed and a 7 are a bit incompatible. If you want that you'd be better off with a cheap 944 or 200SX.

Thing is who wants to go fast in a straight line anyway, that's easy, what you want sir is to go round corners very, very quickly, that's where the fun is and at that a 7 is awesome.

quote:

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Originally posted by norfolkluego
Thing is who wants to go fast in a straight line anyway, that's easy, what you want sir is to go round corners very, very quickly, that's where the fun is and at that a 7 is awesome.

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If you have toe out on the front, youll get better turn in, but the downside is you lose straight line stability, Dont think i read the post properly last night, but thatd make a big difference in itself.

quote:

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Originally posted by norfolkluego
Surely a high top speed and a 7 are a bit incompatible. If you want that you'd be better off with a cheap 944 or 200SX.

Thing is who wants to go fast in a straight line anyway, that's easy, what you want sir is to go round corners very, very quickly, that's where the fun is and at that a 7 is awesome.

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Front toe should be set just on the toe-in side of parallel.

The other thing nobody has mention is bump steer ... but try toe-in first.

My no plate is on the nose, and my MOT guy assures me it is perfectly legal
as no were in the MOT bible does it say the plate has to be vertical, all it does say is that it has to be readable while standing in front at about 20 metres

Steve

Sorry to disagree Steve, but my Fav local copper used to love pointing this out to me.
From the 2001 No. 561
ROAD TRAFFIC
The Road Vehicles (Display of Registration Marks)
Regulations 2001

This paragraph requires the plate to be fixed—
(a) vertically or, where that is not reasonably practicable, in a position as close to the
vertical as is reasonably practicable.

I wasn't prepared to argue the T**s about having to make up a front mount. They also have to have a reflective background to the plate, which counts out stick on plates.

Back to the question in hand, An undertray need not be visable.




Put 8-10 mph onto the top speed by fitting that simple piece of ali. and you can't see if from the rear.

ATB Dan.

Awesome, might have to make my own version of that.

I've not got any bump steer issues.

I'm going to fit my plate on the front of the chassis right under the back of the nosecone.

[Edited on 6/7/11 by franky]