Board logo

A arm design
Nourish - 24/9/24 at 08:43 PM

When building your own wishbone/A arms is there a rule of thumb to the spacing of the chassis mounts ? Cheers

JoelP - 24/9/24 at 09:11 PM

It's just down to what works with packaging. Too close puts twists into the chassis. Too far apart limits steering lock. The positions also need to tie in with chassis design, so they're not just in the middle of unbraced tubes. Are you building your own chassis?

Nourish - 25/9/24 at 10:43 AM

I'd have to own up here - this is for a classic car - I thought this forum would be where the people that know could help me

Mr Whippy - 25/9/24 at 11:49 AM

I doubt there is any rule of thumb at all. However obviously the wishbone needs to still fit within the limits of the front wheel travel when on full lock and that is where I personally start. So turn it to full lock and measure the angle the arm could be before hitting the wheel/tyre and there's your wishbone spacing.

If your talking about the vertical distance then it's just what it would be for the wishbone or arms to be level when at a normal loaded position.

With my old Volvo S60 they got this so horrifically wrong they had to add plastic spacers to the wishbones and metal scuff plates to the wheel arch just to get the cars through the MOT. Even then they scraped away on full lock and had the turning circle of a truck.



[Edited on 25/9/24 by Mr Whippy]

loggyboy - 25/9/24 at 11:58 AM

** An arm design :p

gremlin1234 - 25/9/24 at 12:44 PM

quote:
Originally posted by loggyboy
** An arm design :p

'An '"A" arm design'

gremlin1234 - 25/9/24 at 12:46 PM

quote:
Originally posted by Nourish
I'd have to own up here - this is for a classic car - I thought this forum would be where the people that know could help me


tell us more about the classic car please ;-)

nick205 - 25/9/24 at 01:01 PM

Tell us more about the classic car you're working on?

Are you copying and replacing an existing "A" arm?

Are you modifying the chassis and "A" arm pivot points"

Some more info might help people give more guidance.

Nourish - 25/9/24 at 09:44 PM

This is for a Morris Minor with the intension of fitting an ST170 engine, type 9 box and an Escort axle with a 5 bar link set up. For the front I'd be doing away with the torsion bars and using coil overs as with the back end. I've made some A Triumph Herald top wishbones but now wonder if they're too narrow. I'd post a picture but I don't have a host site

nick205 - 26/9/24 at 08:28 AM

You can post photos on this site.

Look top left, below the "LOCOSTBUILDERS" logo for "Photo Archive".
Add your photo to your "Photo Archive" and then add it to your post.

If we can see what you're doing (or attempting) we'll be much better informed.

Nourish - 28/9/24 at 12:17 AM

Thanks Nick but I must be thick! I try to add a picture - select from my pc - add a title and I keep getting the message "Sorry! Filenames must be alpha-numeric (ie letters, numbers '-', '_' and space) [IMG_1206[1].jpg" - I've tried all sorts to no avail!

cliftyhanger - 28/9/24 at 06:14 AM

quote:
Originally posted by Nourish
This is for a Morris Minor with the intension of fitting an ST170 engine, type 9 box and an Escort axle with a 5 bar link set up. For the front I'd be doing away with the torsion bars and using coil overs as with the back end. I've made some A Triumph Herald top wishbones but now wonder if they're too narrow. I'd post a picture but I don't have a host site


Triumph front suspension is very good, it has been used for decades on hotrods, kits and so on. Caterham still use a derivitive of it.
I have a spitfire, ST170 engine, T9 box and scooby diff/rover 100 driveshafts/GT6 uprights. So not that different in many ways.

nick205 - 30/9/24 at 10:20 AM

quote:
Originally posted by Nourish
Thanks Nick but I must be thick! I try to add a picture - select from my pc - add a title and I keep getting the message "Sorry! Filenames must be alpha-numeric (ie letters, numbers '-', '_' and space) [IMG_1206[1].jpg" - I've tried all sorts to no avail!




1. Make sure the .jpg image isn't too large. (800x600 pixels is ideal)
2. The .jpg file name has to be not alreay in use on this site
3. In the .jpg filename avoid spaces (use a - or instead)

gremlin1234 - 30/9/24 at 11:35 AM

quote:
Originally posted by nick205
quote:
Originally posted by Nourish
Thanks Nick but I must be thick! I try to add a picture - select from my pc - add a title and I keep getting the message "Sorry! Filenames must be alpha-numeric (ie letters, numbers '-', '_' and space) [IMG_1206[1].jpg" - I've tried all sorts to no avail!




1. Make sure the .jpg image isn't too large. (800x600 pixels is ideal)
2. The .jpg file name has to be not already in use on this site
3. In the .jpg filename avoid spaces (use a - or instead)


it looks like he had square brackets in the name, as nick says special chars do not work.
also I recommend prefixing your filename with your user name to ensure it is unique

coyoteboy - 1/10/24 at 01:43 PM

They're part of a whole system design. If you just bolt on an existing design, the rest of the system has to compatible. The design loads for a 1970s 600kg trundler will not match those for a 900Kg track machine. The brake and acceleration forces depend on the length, and the bearing loads the inboard ends will depend on the aspect ratio and those forces. It's all linked.