Castor is 5.3 deg enough ?
big_wasa - 9/11/05 at 08:29 PM
Yes shoot me now 
I know the subject has been flogged a million times BUT..
I have chassis ,I have bones , I have brackets and I want to get them all stuck together.I only wish to weld them on once so...
The question is ,Is 5.3 deg castor enough to give the self centering steering required to getting it through the sva ?and if I increase it a touch to
the 7 deg thats been sujested to make sure what would the negative aspects of the handling be.
Any input would be apreciated as I intend to make the jig this weekend....The bones are book and thanks to this site I found they will give bugger all
castor on there own so I will be pulling the top bones back as far as required...
Rorty - 9/11/05 at 08:48 PM
Jerry rig the wishbone brackets to the chassis and have a play with it all.
I'm tipping you'll require somewhere nearer to 6.5-7 degrees neg.
Bob C - 9/11/05 at 09:18 PM
remember the book design is ~2.7 degrees & everyone knows it's not enough. So you need more than book. I've always assumed a genuine
5.5degrees would be about right - do I need to further alter things? I have to remake my top bone's anyway so opportunity knocks!
Bob C
Mark Allanson - 9/11/05 at 09:24 PM
I have 5.5° confirmed with a computerised Hunter system, the self centring passed the SVA, and the car drives better than I could ever have hoped.
More caster would probably be an advantage for catching wet weather oversteer and not over correcting.
jambojeef - 9/11/05 at 10:32 PM
Re: Not knowing what castor angle is best - I was thinking exactly the same thing when I designed my top bones!
I took the easy way out and made them adjustable with rod ends and washers - as I know some other builders do.
Could be an answer?
Geoff
Rorty - 9/11/05 at 10:46 PM
quote:
Originally posted by Bob C
remember the book design is ~2.7 degrees & everyone knows it's not enough. So you need more than book. I've always assumed a genuine
5.5degrees would be about right - do I need to further alter things? I have to remake my top bone's anyway so opportunity knocks!
Bob C
I've built more cars than I can remember, but never a Locost, so I can't be specific. However, I believe from the general size/weight etc.
of the Locost, that 6.5-7 deegrees would be about right. It certainly won't do any harm, you'd need to go way over that amount (possibly
double) before seeing problems like steering being too heavy, so I would give it a go.
Mark Allanson - 9/11/05 at 11:16 PM
Remember this lot?
http://www.locostbuilders.co.uk/viewthread.php?tid=3551
Mark Allanson - 9/11/05 at 11:21 PM
"Ron Champion, what a twat!!"
http://www.locostbuilders.co.uk/viewthread.php?tid=3480
NS Dev - 10/11/05 at 12:09 AM
quote:
Originally posted by Rorty
quote:
Originally posted by Bob C
remember the book design is ~2.7 degrees & everyone knows it's not enough. So you need more than book. I've always assumed a genuine
5.5degrees would be about right - do I need to further alter things? I have to remake my top bone's anyway so opportunity knocks!
Bob C
I've built more cars than I can remember, but never a Locost, so I can't be specific. However, I believe from the general size/weight etc.
of the Locost, that 6.5-7 deegrees would be about right. It certainly won't do any harm, you'd need to go way over that amount (possibly
double) before seeing problems like steering being too heavy, so I would give it a go.
Will concur on that one. My grasser has around 7 degrees and that is a bit lighter on the front than a seven, so 6.5 degrees ish should be about
right. If you make it adjustable by +/- 0.5 degrees or so from there you won't be far wrong.
As Mark Allanson said, nice brisk partial self-correction in the wet will result from this sort of setup, and if you enjoy "spirited"
driving (and who doesn't!) the that will be most welcome!
Bob C - 10/11/05 at 12:22 AM
So I could add a degree or so,- but Mark has a proper 5.5degrees & says it works fine. My setup is different to most (esp the cortina guys) in
that the mx5 front has zero scrub (honest) - I'm thinking that will reduce loading on balljoints & may reduce the need for castor (or will it
make it worse???) the original mx5 had about 5.3 degrees castor.
Bob
Mark Allanson - 10/11/05 at 12:50 AM
I am also running a Pinto and have given no consideration to weight (700kg's at SVA), so the lightweights may need more castor.
The SVA tester was very surprised by the self centring, he really expected it to be the one thing he could pick me up on
Surrey Dave - 10/11/05 at 08:15 AM
I have around the 5 degree mark , have always thought it could do with more, as the car has a bit of a dead spot in the straight ahead position , and
can tend to wander.
Also self centering could be better......
Lozec - 10/11/05 at 08:59 AM
PLEASE, don't increase the caster above 6 deg. I've been down that road. Built my car on ST chassi wth a descent 5 deg caster. Result is
poor or non self centering. My SFRO-inspector (swedish thing) wasn't happy with the sefl centering and i made new upper arms to get 9 deg. The
difference is that it requires more force to turn at higher speeds. Self centering at low speeds still poor. The inspector wasn't happy with it
but let me throuh after I'd ensured him that I will continue to improve it...
Im running Cortina upritghs with 205/50R15 wheels with ET 35mm. 185 wheels would probably made it better.
Mondeo wheels have more offset and will probably result in a better behavior but the front track will decrease as well.
Next thing on my agenda is to make new trailing arms with a new better upright :-)