andrews_45
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| posted on 15/12/06 at 11:52 PM |
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MK chassis design
Right then... I have some minor problems with my car, that could have drastic effects on my handling.
I have took my car to a race car company, to have some base settings done. I got a call from them to say I have zero castor on the front end set up
and my car wouldnt handle on a track as it is.
Ok, I thought... No problems I'll just call MK and explain the mistake, who assured me that no locost race cars have any castor and it is how
they are designed.
NOW!!!! I could be wrong, and left to eat humble pie.!! But it seems to me that my car has a inherent in-built design problem, can anybody pursuade
me different. I did suggest to MK that they could exchange my top wishbones for a set with the correct castor i.e 5 deg positive (or is that
negative, i always get confused), but I was assured that me, and a experienced race set up company are wrong...
Who do I listen to??
Help and advice pls
Pls note: I have zero issues with MK and have found them a very helpful company in past experience, I just do not think they are right in this case
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Andy S
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| posted on 16/12/06 at 12:14 AM |
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I would agree with your race car company that zero would be a particularly bad thing - 5-7 degrees in my book.
We know that the book has an error with the top wishbones but I dont think that even Ron is that far out.
Zero would give some very strange feeling
Perhaps give MK the benefit of the doubt that they got the wrong end of the conversation and ask them again.
Cheers
Andrew
[Edited on 16/12/06 by Andy S]
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pawgrp
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| posted on 16/12/06 at 08:01 AM |
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talk to martin keenan at mk eng, he made the jigs and he will be able to explain. hope this helps.
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oliwb
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| posted on 16/12/06 at 08:24 AM |
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&'s always have problems with castor (I say problems because its only really a problem with self centering and SVA not handling.) I
don't honestly know what my CAT is setup to but it handles like nothing else.....I was thrashing a 911 Carrera in some twisties the other day
with it no sweat (got wasted on the straights - obviously!) I'm not really much of a boffin when it comes to handling geomoetry etc but I
imagine that your MK wont be any different to the others (all made on jigs) so if no one else has a problem with castor and handling it makes sense
that you wont either. Obviously I could be wrong.....don't MK use those mushrooms in the front uprights that can be rotated to induce castor?
Have you set them up right?? Also whats the car ultimately for? If its going to be SVA'd I wouldn't spend too much time setting it up now
as you'll lose all your settings making it self centre properly and various other bits and bobs for SVA. Obviously if its not going to be used
on track after SVA then I would suggest that a race garage are not the best ppl to setup a road car as they don't usually take into
consideration things like bump steer etc....some food for thought....Oli.
If your not living life on the edge you're taking up too much room!
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britishtrident
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| posted on 16/12/06 at 09:30 AM |
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The most important thing about caster is to get both sides exactly equal when the suspension is in its normal static loaded condition otherwise the
steering will pull.
Caster is a complex subject, in the days of high profile cross-ply tyres a lot was needed especially on cars that were light at the front, with modern
tyres much less is needed.
The ammount of caster used is also closely connected to king pin inclination and camber angles. In old cars used a lot of caster linked to a lot of
kpi and a quite a lot of posative camber.
The Cortina upright (and the Sierra based upright) has very little caster designed in. With the Cortina upright use a lot of caster and you will end
up too much negative camber in turns.
MK set thier cars up with a fair bit of negative camber, if you increase the caster angle you may find this has to be reduced and this may have other
effects.
Also remember ride height trim front to rear has a big effect on caster ---- raising the rear ride height car relative to the front decreases
caster.
***** How often do I have to repeat this point ******
***** Rotating the mushroom won't alter the Caster angle *****
However it will alter the king pin inclination if the same camber angle is set.
On the good side caster gives better self-centering and road feel.
On the bad side Caster increases bump & roll steer and also loads up the steering in turns and increases tramlining.
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andrews_45
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| posted on 16/12/06 at 09:51 AM |
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No mushroom on my car, its a locost race car. I told MK what it was for when I ordered it. I have got to use Cortina uprights as per the locost race
regs.
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flange nut
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| posted on 16/12/06 at 10:09 AM |
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This could be a stupid suggestion but could you have the top wishbones on upside down?
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TimC
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| posted on 16/12/06 at 10:25 AM |
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Ring Matt @ Procomp
0121 3503258
He'll put you right.
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Hellfire
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| posted on 16/12/06 at 10:26 AM |
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Is it an Indy you're talking about? Are you sure your wishbones are on the right way? Reason I ask, is because the MK wishbones do have castor.
Phil
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britishtrident
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| posted on 16/12/06 at 10:53 AM |
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quote:
Originally posted by Hellfire
Is it an Indy you're talking about? Are you sure your wishbones are on the right way? Reason I ask, is because the MK wishbones do have castor.
Phil
Good point
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TimC
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| posted on 16/12/06 at 10:57 AM |
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quote:
Originally posted by britishtrident
quote:
Originally posted by Hellfire
Is it an Indy you're talking about? Are you sure your wishbones are on the right way? Reason I ask, is because the MK wishbones do have castor.
Phil
Good point
Except that it's not an Indy - it's a 750MC Locost. 
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andrews_45
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| posted on 16/12/06 at 01:18 PM |
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I can confirm that they are the right way round. MK said that they are jig made and none of the locost race cars have any castor
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D Beddows
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| posted on 16/12/06 at 05:35 PM |
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Vote number 2 for phoning Matt at Procomp
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Andy S
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| posted on 16/12/06 at 06:44 PM |
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quote:
Originally posted by andrews_45
I can confirm that they are the right way round. MK said that they are jig made and none of the locost race cars have any castor
Not great reasoning - are they able to give a better technical explanation as to why they think that the geometry works better that way?
Andrew
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D Beddows
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| posted on 16/12/06 at 07:15 PM |
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Probably for similar technical reasons to not designing them to be strong enough either 
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procomp
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| posted on 16/12/06 at 07:21 PM |
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Hi just about sums up MK's attitude. All the other manufacturers of chassis for the locost championship certinaly DO have castor on them.
cheers matt
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procomp
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| posted on 16/12/06 at 10:07 PM |
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Hi posted reply in the race isues section.
cheers matt
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procomp
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| posted on 16/12/06 at 10:20 PM |
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Hi And you honestly BELIVE every thing you read in the kit magazines.
Maybe all the race driver that have had Mk chassis must be wrong about the handeling problems with thier wishbones and Zero castor then.
I still cant see what you are trying to say as Mk have said that they are jigged for Zero castor and that is what they have got .
cheers matt
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Hellfire
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| posted on 16/12/06 at 10:23 PM |
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Charlie, I don't think anyone's questioning the amount of caster on the Indy wishbones. Don't know if the MK Locost ones are
manufactured to the same dimensions though but from other threads, it would appear not.
Phil
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procomp
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| posted on 16/12/06 at 10:29 PM |
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Hi i dont think that i am degrading them they are the ones that have admitted to running cars with no castor.
They are also the ones that LIED by telling thier customer that all locost race cars have zero castor so accept it .
All of the other manufacturers actually do have castor on them.
cheers mat
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procomp
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| posted on 16/12/06 at 10:41 PM |
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Hi is the Mk sprint allowed in to any of the race championships that we race in.
Is it allowed in to the FIA historics.
Is it allowed in to the barc westfield race serise.
Is it allowed in to any of the 750mc championships .
cheers matt
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procomp
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| posted on 16/12/06 at 10:56 PM |
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Hi i hope they handel better than the one in the 750 kit championship.
Anyhow slightly off the topic off castor.
Off to bed cheers matt
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Hellfire
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| posted on 16/12/06 at 11:19 PM |
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Could these posts possibly explain why the vehicle in question has no castor??
It would appear that the wishbone brackets may have been moved and re-welded??
This post
And the post below would suggest Luego wishbones have been used, or is this not the case??
This post
I'm not trying to stir things up, just trying to figure out why there's no castor but it would appear that MK may not be the ones to
blame...................
Phil
[Edited on 16-12-06 by Hellfire]
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Hellfire
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| posted on 16/12/06 at 11:29 PM |
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Also notice that the lower bracket at the rear has been repositioned and re-welded
Phil
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Hellfire
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| posted on 16/12/06 at 11:34 PM |
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Hang on a minute.......... The race car company that is setting the car up for you is Procomp isn't it??
Like Charlie said earlier, and after looking at some of Matts historic posts, he clearly seems to have issues with MK for whatever reason..........
Phil
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