RS2 - Dimensions incorrect? Help!

[mk1]

Hi,

not posted in a while but mainly because Im on build no2 of my chassis (i wasnt happy with the accuracy of build no1 so got busy with the hammer and started from scratch! - this time I decided to paint it with rustproof as i put it together).

Anyhows - I needs some help from the brains of the Forum. I have searched the forum but cant find anything!

Page 43, Fig 4.15 shows the external length of RS2 protruding from the bottom rail as 406.9mm (with total length of RS2 at longest point at 430mm).

Problem is, to achieve 406.9, RS2 total length needs to be cut down (which is what I did). But...having done this (and this dimension being correct) means that RS10 is not square with RS7a/RS5 (ie RS10 - the vertical is out by 1 degree).

Any ideas guys?

My current thinking is that the book is wrong on the RS2 dimension - theres a few errors in the book, Im hoping this is one of them?

Any help much appreciated,

Thx

Martyn

[deezee]

I think you've got confused. RS2 is absolute correct. The 406.9mm dimension is how much it sticks past the 25mm chassis rail, BR12. So add your 25mm for the rail, then lose 3mm for chassis plate CP1 and your on 428.9mm. So not really a far off the 430mm measurement given.

Bear in mind that its only rails 2,7 and 4 that need to be square for the mounting of the suspension, the RS10 rail could be all kinds of wonky and it wouldn't affect the car in the slightest.

[will_08]

I agree with Deezee, and it sort of shows when you alter one thing you think may be wrong - then that in turn makes somethig else wrong!

I know theres alot of skilled people on here produced very accurate chassis's......but when your making a chassis with no jig as such, is going to be out here and there. IMO

Will

[mk1]

I think you've got confused. RS2 is absolute correct. The 406.9mm dimension is how much it sticks past the 25mm chassis rail, BR12. So add your 25mm for the rail, then lose 3mm for chassis plate CP1 and your on 428.9mm. So not really a far off the 430mm measurement given.

Bear in mind that its only rails 2,7 and 4 that need to be square for the mounting of the suspension, the RS10 rail could be all kinds of wonky and it wouldn't affect the car in the slightest.

Hi Deezee,

Thanks for the reply. Im clear about the RS2 sticking out 406.9 past BR12 and that is correct, I did the sums as you did above (in fact the total length of RS2 is 428.9 and so also correct) It just doesnt show in the book RS10 to be at an angle from square outwards (1 deg), it shows it as square?

Still a bit confused.... has everyone got RS10 at a bit of an angle then?

Thx

Martyn

[will_08]

No they sit at a right angle, then when you add the top frame to it should mate with SB3 perfectly.

Unless the lean back of the whole frame is not quite right, which is what i had.

[mk1]

No they sit at a right angle, then when you add the top frame to it should mate with SB3 perfectly.

Unless the lean back of the whole frame is not quite right, which is what i had.

Thanks for the comments. Strangely the lean back angle was the problem I had the first time round (build #1). On build #2 (Revenge of the chassis) I have measured all angles with an inclinometer so they should be pretty close).

The way I see it, I have two options:

1. Remake RS2 a little longer (about 4mm), so the back is square. (But is this likely to have any knock on effects?)

2. Live with the angle being slightly out (which is bothering me at the moment as it seems excessive).

Thoughts?

Thx

Martyn

[mk1]

No they sit at a right angle, then when you add the top frame to it should mate with SB3 perfectly.

Unless the lean back of the whole frame is not quite right, which is what i had.

PS, what did you make the lean back angle?

[will_08]

If you put a flat edge against SB2 that comes down to the build board and measure it against BR12 and you get 151mm then the angle has to be ok. Thats I look at it anyway!

stands to reason BR12 isnt going anywhere, if the lean back is out, SB3 is trying to push the top suspension frame further away. Hence you want to lean RS10 back/extend RS2! Id recheck the lean back.

Will

[mk1]

If you put a flat edge against SB2 that comes down to the build board and measure it against BR12 and you get 151mm then the angle has to be ok. Thats I look at it anyway!

stands to reason BR12 isnt going anywhere, if the lean back is out, SB3 is trying to push the top suspension frame further away. Hence you want to lean RS10 back/extend RS2! Id recheck the lean back.

Will

Thanks Will,

I will check this tonight.

Rgds

Martyn

[HandyAndy]

Unless I,m missing something, which is highly likely :o

If RS2 is incorrect when positioned into place , then , surely RS1 will be too??

I haven,t got my book at home with me but if you have needed to shorten RS2 then it would appear that BR12 is not "true", if you have only need to shorten RS2 & NOT RS1 then the fault lies in the BR rails.

As others have said , the diff cage is basically a TRUE box welded to the back of the chassis , remembering that you need to leave a 3mm gap for where the small plates are fitted on the cockpit side of the seat back area.

RS10 should be at right angles.

Be careful when presuming all is well by shortening parts here & there to get your measurements correct, ( shouldn,t need to ).
This will cause you problems when you come to fit the wishbone brackets to the diff cage if the diff cage is "wonky" as the placement of the wishbone brackets are measured from various points including the rear face of BR12.

If I had my book I could be more precise :o

cheers
andy

[mk1]

Unless I,m missing something, which is highly likely :o

If RS2 is incorrect when positioned into place , then , surely RS1 will be too??

I haven,t got my book at home with me but if you have needed to shorten RS2 then it would appear that BR12 is not "true", if you have only need to shorten RS2 & NOT RS1 then the fault lies in the BR rails.

As others have said , the diff cage is basically a TRUE box welded to the back of the chassis , remembering that you need to leave a 3mm gap for where the small plates are fitted on the cockpit side of the seat back area.

RS10 should be at right angles.

Be careful when presuming all is well by shortening parts here & there to get your measurements correct, ( shouldn,t need to ).
This will cause you problems when you come to fit the wishbone brackets to the diff cage if the diff cage is "wonky" as the placement of the wishbone brackets are measured from various points including the rear face of BR12.

If I had my book I could be more precise :o

cheers
andy

Hi Andy,
You are correct, RS1 and RS2 are out by exactly the same amount and I am happy that BR12 is square.

I totally agree with what you are saying about modifying parts here and there, that was the big learning curve from my first chassis build and why Im getting a bit frustrated with this one as i have been really careful with the angles (inclinometer) and dimensions.

Im losing hair over this one :o) as all other dimensions seem to be correct (having measured over and over again but i must be missing something. I will recheck the angle of SB1 assembly and report back.

Thanks again with your patience and help guys. Will keep you posted.

Thx

Martyn

[HandyAndy]

I,m slightly confused now ( doesn,t take much I know :D )..

You say you can get the position of RS1 & RS2 correct as per book & as per how Deezee has mentioned....is this correct ?

If so ....

(this is where I,m confused)

Are you saying you can,t get RS4 / 5 / 7 & 7A to meet the seat back rail? & is this what is causing you to have RS10 at an angle instead of a 90 degree right angle ?

Sorry for my questions...just trying to get a clear picture in my head :o

A photo showing the problem would help ;)


My point about the wishbone bracket placements is to highlight that if you position them incorrectly( from measurements taken from the seat back area/BR rails) then your wishbones won,t fall into line with the upper shock bracket in the suspension box Cp3 /4 etc .

Hope I,m making sense ?
cheers
andy