Zcars tubular front lovelyness
Turbo Mini Forums

Just found this on the bay.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?Vie...AMEWA%3AIT&rd=1

porno!

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

Nice...... but i'd like to see somewhere to mount the steering rack on the frame.

Why?

Just curious!


I REALLY like that frame...

just so its mounted on something nice and sturdy rather than having a nice frame and a steering rack bolted to pressed tin, to try and stop bumpsteer problems.

Bumpsteer is caused by the positioning of the steering rack, and the arcs in which all the suspension arms work in. It makes no odds as to whether your rack is mounted on tin or a subframe, if it is in the wrong place it will have equally bad bumpsteer.

It is a long time since I mucked about with it, but I seem to remember that Minis do not suffer from bumpsteer especially, this is also helped by the relatively small suspension travel they have.

true but if you've gone to the trouble of making a nice frame you may as well go that extra bit and sort the bump steer,

re the tin there must be some movement there from steering loadings so if your making a frame anyway.....

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

you can help to remove the bump steer on mini which has been lowered you can replace the track rod ends with rose joints. You need to drill out and sleave the steering arms on your uprights, but then you can space out the rose joint to remove some, or all of the bump steer

Team Racing

WWW.FORCE-RACING.CO.UK PLEASE CLICK HERE

From the state of my Dad's autograss car when received newly built from Z-Cars it would appear that they don'tknow the meaning of bumpsteer anyway.......or at least they certainly didn't check it......

My view is with the standard subframe and steering rack position that the rack moves around in relation to the subframe (and the suspension mounting points) as the body flexes during cornering, how much I don't know but I assume it will happen, fitting a cage will get rid of some of this, and bolting the back of the subframe to the bulkhead will get rid of it further.

As I see it fixing the rack to the subframe will prety much stop the rack moving and causing bumpsteer, then when the bump steer is dialed out (either by shimming the rack, or the trackrod ends) it will stay dialed out when the body flexes in the corners.

I follow your logic - kinda.
There is just one small detail; Our cars were not made in a Jelly mould.

I think you'll find the flex that you're suggesting is a huge problem will be measurable in thou's - not inches. I'm much happier with the steering column mounted to the floor. In the standard place. With the standard mounts. With the standard rack.

Jelly mould! LOL

Although i hav'nt dabbled in this i was under the impression that the amount of shimming needed to get rid of the bump steer was in the order of 1-2 16ths of an inch, I wouldn't be suprised if there was this much movment.

agreed it is overkill going to this extent to get rid of a little bit of bump steer but personsally if i was going to the extent of putting a fabricated subframe in I would go that extra bit and mount the rack on it

I was under the impression that Bump-steer is a good thing to totally eliminate, but if you're looking at the position of rack in "thous" then you're making WAAAAY too much work for yourself. I think it's more in the region of if you've got it to within 1/4, or even better 1/8", then that's plenty good enough...

Edited by TurboDave16V on 22nd Feb, 2006.

I think people are also discussing two different issues here.

1. Bump steer due to differing ascs of suspension arms and steering arms.

2. Relative motion between subframe and body (which can result in some unwanted steering inputs depending on subframe mounting type).

Just my £0.02 worth...

we're discussing,

WWW.FORCE-RACING.CO.UK PLEASE CLICK HERE

Robert Tarzwell has done just what Mini13 wants several times on his race minis. He explains in his new book that it really does matter in a fast racecar.

Mini 13,
1) Bump steer is not in the least affected by the rack being mounted on the subframe or the shell. It's the relative position of the rack ball joint to the suspension pivot points.
2)Mounting the rack on the shell and the sub frame on soggy rubber will cause vague steering as the sub frame and attached suspension will move relative to the rack.
3)Mounting the sub frame rigidly to the shell and the rack to the shell is ideal.(the easy way)
4)Mounting the rack to the subframe with rubber mounts subframe to shell will to an extent fix the problem but subframe movement will be a problem with cornering forces and subsequent sub frame movement plus bending of the column mounts.
5) mounting the suframe rigidly and the rack to the subframe would be fine but is very Complicated. So Back to 3 above and you have what most if not all competition Minis use
Regards
Dave

Spot on.

The Mini isn't actually that bad for bump steer, have a look at Mk1 / MK2 Escort, Capri or many other similar cars if you want to see bump steer! I have only ever come across one 'normal' road car that was perfect for bump steer and that was the E30 shape BMW 3 series.

A lot of people would argue that the applications most affected by bump steer are rally cars (lots of movement), road cars (rubbish surfaces giving plenty of movement) with cars that live on smooth race tracks least effected.

I have been involved in tghe design of a couple of radio control cars (1/10th off road) and in that application I acctually try and get a little bump steer such that an extremely unloaded inner front wheel will actually toe in slightly so that when it regains traction it doesn't throw the car across the track (very high grip surfaces). Trick is to do that only at the extremes of travel and not throughout the normal range.

Anyway, this is all slightly off topic ..... has anybody got any pictures of the Z-cars frame from other angles??????

Every day is a school day ...........

How fast and how expensive ...... the same question...

tar dahhhhh

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

Good man ... thank you ..... Out with the measuring stick!!!

Every day is a school day ...........

How fast and how expensive ...... the same question...

Also answers the question about engine mounts, they aren't solid. If you look closely you can see the tubular metalastic bushes mounted nice and low.

It pains me to say this but my first response is that actually looks quite nicely engineered. Not as well triangulated as fastcarls offering though but then again it looks like it was never intended to deal with the same loads. The engine mounts do look a little like an after thought.

I could be tempted to do something similar myself, just need to look a little more at the loading paths.

Every day is a school day ...........

How fast and how expensive ...... the same question...