I’m having some problems measuring the compound angles of tubes LA and LB. I’ve looked at previous threads, but haven’t yet found an answer. I was
hoping some of you guys could let me know how you did it.
Cheers,
Chris.
Have you tried Mcsorely plans? I did mine before that, it was bloody difficult, but you get there eventually. a bit of trial and error in the abscence
of calcs, ie a piece of scrap worst case!
tim
Mcsorely plans? Please excuse my ignorance.
Using Trig' I just worked out the angle that each cut needed to be along each face of the tube. I then cut each face individually.
Took me three attempts but worked in the end! 
Cheers,
James
EDIT:
You could of course cheat and make the nosecone angled in only one plane- then just lean it back! I think Conrod did that on his first Locost.
Additionally it's worth noting that the top/bottom offset should really be 4" not 3" so you can fit the wishbones on better. Mark
Allanson knows more about that than me though.
[Edited on 19/5/04 by James]
well mine is probably bu**ered because I just cut them by eye and then set them by the location of the suspension brackets using the jig i made.
Ned.
James, could you please expand on your comments re top to bottom offset, or maybe Mark should? Thanks, Steve.
Basically if you want to use book wishbones AND get the correct castor angle (5.3 or 5.5 deg) you need to shift the top wishbone back by about 20mm.
If you do this with the standard front assembly one of your wishbone brackets ends up with nothing to fix to! You can either change the L assembly, or
change the design of the wishbone to overcome this. But you need to change one or the other to get the castor right.
Cheers,
David 
'Nuff said!
James
The one I'm doing now has the front top 25mm further back and the fu's the same to give more castor and still leave something to fasten the bracket to. The chassis is 25mm taller as well
I'd intended to use GTS's wide track wishbones. will that effect the position of the L & F tubes?
In a word....yes...(AFAIK) you still need to lean the L assembly back further and leave the FU tubes out until you have the wishbones....
Anyone else agree with me?
Cheers,
David
I'm using sierra uprights so will have to use mushroom inserts. It's possible to get the inserts with an offset hole, so will this help the
castor without having to move the wishbones?
[Edited on 19/5/04 by Chris_R]
This might help if you are to lazy to use a hacksaw, like I am.
Drawings for more reclined versions in following posts.
Oh! I forgot! Please check the dimension, I don't have The Book around.
Happy building
[Edited on 04-5-19 by leto]
[Edited on 04-5-19 by leto]
Reclined 20mm
[Edited on 04-5-19 by leto]
[Edited on 04-5-19 by leto]
Reclined 40mm
[Edited on 04-5-19 by leto]
quote:
Originally posted by Chris_R
I'm using sierra uprights so will have to use mushroom inserts. It's possible to get the inserts with an offset hole, so will this help the castor without having to move the wishbones?
quote:
I believe Castor is defined by a line through the joints and they will not be moved by a offset mushroom. This have most probably been discussed before. But I can bee wrong in both cases.
(It has been posted before too....)
would turning the offset to the front of the vehicle not angle the upright toward the rear?
I always assumed that too, but i remember reading something to the contrary...if you can find the topic thread you can read all about it...i dont
remember what it was called....all i remember is that the adjustable inserts dont do much for you....
Anyone remember?
And i stand to be corrected as usual.... 
[Edited on 19/5/04 by flak monkey]
so, the basic advice is make the 76mm lean of the L section around 101mm and don't add the F tubes until wishbones arrive? Knowing my luck something will go wrong somewhere along the line.
Yup, sounds about right to me Then your brakets will definately end up with something to fix to...and not be hanging in mid air!
Cheers
David
Reclined 25mm
Hi Chris
this subject is a real old one, go into search, look for castor angle, and check accurate front suspension date 13/2/03,all will be explained in
detail. i discovered the cockup in the book a long time ago, and did my own alterations to the chassis to accomodate the suspension brackets better.
while i am typing just to make clear for people looking at the castor angle for the first time 5.3 degrees means 5 degrees 30 minutes. or 5.5 which
means five and one half degrees, cos theres 60 minutes in a degree. cheers davef.
quote:
Originally posted by Chris_R
so, the basic advice is make the 76mm lean of the L section around 101mm and don't add the F tubes until wishbones arrive? Knowing my luck something will go wrong somewhere along the line.
Castor is the angle which the line that passes between upper and lower swivels makes with a vertical line passing through the center of the hub.
By offsetting the point that the upper swivel attaches to the hub, the castor angle is not being changed at all. However, a line drawn through the
two swivels will intercept the ground at a slightly different point with reference to the tyre/ground contact point, so the castor action will be
changed. However, the amount of change will be miniscule, and probably not even noticeable.
A point to note is that if you tilt LA & LB backwards you reduce the area available to mount / adjust the steering rack. It may be a better option
to retain the book tilt and gusset the area where the top forward brackets mount.
Fully agree with leaving the fitting of the 'FU' tubes until you mount the wishbone brackets.
Mick
I don't think that area is short on room though- the MK2 rack is mounted quite a way back from LA/LB. It's more of an issue with Sierra
racked cars but I'm pretty sure it'd still be ok... mine (with Sierra rack) would certainly have benefitted from this mod.
Atb,
James
Many thanks guys. Finally got it done and fitted last night. I used trig and also increased the lean by 25mm. One thing though. It seems to have highlighted that my chassis is twisted. It's only about 4 - 5mm and it looks as though adding tubes K1, K2, N1 and N2 will pull it back into shape. On a scale of 0 to very bad, how bad is this?
I would say 0
4-5mm is not very much. If you can try to straighten it out go for it. If not, when you put your suspension brackets on make sure you take the twist
into account. I have certainly heard of peoples chassis' being furthur out than that....
Cheers,
David
That’s quite reassuring. Like I said, I think I can pull it back, but as long as there’s a solution if it all goes Pete Tong I’ll not loose sleep over it.