hi all just found this site very interesting.
i have finished my chassis according to rons
book. the only fault i found is the set back
of la &lb should be 4 inches not 3 as per book, 3 inches cancells out the castor angle.

Dave,

I'm going to be putting my (front suspension) brackets on tomorrow.

If you look at fig 7.11 on page 83 you will notice that the top wishbone is assymetrical rather than symetrical.

Hopefully that sould sort out your "lost inch"

Regards

Simon

hi simon please study that drawing with care the off set on the top wishbone is supposed to give the 20mm required. but it dos,nt half of 83/4 is 43/8 which gives you 3/8 offset which is still not enough.

So whats the outcome of this question, (BTW not sure about sizes, I make half of 83/4 as 41 and 5/8 therefor giving 1and 1/2)

hi hornet, i will try and explain in metric it might be less confusing, get a piece of a4 paper and a plastic protractor strike a line from one corner at 5.30 degrees for a length of 225mm which is the distance between the ball joints on a cortina stub axle. then you will see that the offset is 21mm to give you the correct castor angle. thats why i said la and lb should be set back 100mm and not 65mm as the book says. if you leave the set back at 65mm your top front wishbone bracket will be half off the upright of la and lb and will need a supporting gusset.

re previous message, sorry that measurment should read 75mm not 65mm. cheers davef.

Hi Davef...

The idea of the LC/LD offset being an error in the book is something I've not heard or read before... most people simply position the brackets as needed to get the right caster (knowing the top wishbone is assymetrical). Too bad Ron didn't show us exactly where to mount the brackets.

There is a link to a full study of the front layout (side view) around here somewhere... I believe that the conclusion was that the bracket is mounted nearly half on and half off (2" wide bracket, 1" tubing).... and that's perfectly ok as long as it's fully welded. There is also a lot of adjustability in the upper wishbone as the bushings are 1&7/16 wide within a gap that is 1.9" wide... nearly 3/16" clearance on each side for adjustability.

Keep in mind that if you were to set LD back farther than the book, the angle on the inside edge of the standard nosecone would no longer line up... and the length of LA/LB would also be significantly off. This is another reason why I believe it is not an error; it would have effected more than one measure on more than one part (not just a simple typo).


Cheers,
-Jim M.

HI JIM
when i built my chassis i did so to the book
thats when i discovered that the front top bracket was positioned half off la & lb, so i shortened the top rails by one inch & made the off set of la & lb 4inches instead of 3 inches and yes this did entail making la &lb slightly longer, but the finished product looks far better, and the bracket is positioned central on la & lb. bear in mind nothing changes ie spacing between wishbone & spring because the brackets are wher they should be according to the book. also my nose cone butts up to the aluminium sheet not the chassis. granted in the end you dont see anything anyway, but i still think it should be 4 inches not 3 inches. there is a good indication of what i mean on MERLIN,S photo album on this site, check front suspension drawing. cheers davef.

Hi Davef,

It sounds like a nice improvement over the book... thanks for sharing.

Along those lines...In my next build I'm going to straighten out everything on the front end; there will be no compound angles at all... but that's long down the road.

Cheers,
-Jim M.