Dirty_Vinylpusher

Yep.
Got another 4 ostr... struts today so I have plenty to practise on for making shockies.



Now, with the A-arms, Wishbones or whatever you call them, should they be parallell when you look at them from the front?
I guess this would mean that the wheel's camber doesn't change when the shockie is compressed.

Bear in mind that this is mainly for offroad use.



Any thoughts on this appreciated as always.
Or drawings, CAD or MS Paint or whatever to make it easier to explain.


Thanx

ttr125fan09

My Feedback: (1)

well with how yours and my a-arms are setup, we will get a little bit of change in camber, but nothing to be worried about for offroad use

Frederik_b

Removed for incorrect content

Frederik_b

edited: I juste understood by re-reading your post, you are doing a double A arm setup. Sorry I thought you were planning to do a macpherson strut design lol it must be that "strut" and ostrich thing that is confusing me hahahah

so with double wishbone I'd do it parallel one to the other. That will allow larger travel with no camber change.

Fred

Frederik_b

But while you are at it (suspension geometry!) if you are ever going to play with the angle between the A arms (when looking from the front), it would be to lower the inner side of the top arm. See the paint drawing, the blue hashed line would be a setting that would give camber as the wheel compress when you turn. So maybe planning for an extra set of holes sligtly below would allow for future adjustment.

But for large amount of suspension travel I would keep it at a parallel setting.

More importantly I believe is you couldmake them not aligned vertically when looking from the side. I mean your top A arm would be moretowards the rear of the car compared to the bottom one. Sorry if I am explaining you something you already know!this will have a caster effect, which is good as it will make the tire dig in when you turn. Caster is like camber that appear only when you turn the steering.

I guess it's not really needed, but why not add a color chart for the drawing hahahha
Green : ball joint
Pink: wheel bearing
Blue:A arms
Brown:chassis
White: your shed



You could also add an angle to the whole A arms assembly(front part of the bottom frame tilted upwards) as it would soak up bumps better (the A arms would be "attacking" the bumps at an angle) while at the same time giving caster, but it's kind of complicated with all the angles. I'd like to do it on mine but I dont know how I could put an angle in my thick bottom plate.. might be easier for you with welds.

Fred

Dirty_Vinylpusher

Thanks Fred that makes sense with the caster.
Will look at putting the top arm a bit further back than the lower one.


Have just started to make the first top A-arm and hope to have both of them put together this afternoon for a mock-up photo.



Ok time to go talk to the ostrich.

ttr125fan09

My Feedback: (1)

ask him if i can have some ball links, please....

Dirty_Vinylpusher

Ok another question.
I've made the upper arms, and I left them a bit longer just in case as I didn't know where the shock absorber would end up etc.
It would be really good if I could leave them at that length.
Would this affect anything?

If the upper arms pivoting point is further to the centre of the car than the lower ones, is what I'm trying to say I guess..

I had a quick look earlier but it's a bit hard to tell until they're secured properly, but it seemed like the camber wasn't affected.
Not that it's gonna make huge difference to a car like this but still curious to know.

Dirty_Vinylpusher

Just had to quote myself there again......
..seems I know myself pretty well.

Dirty_Vinylpusher

Here's some pics from today.
I've done more since they were taken and will post more updates tomorrow.

VassilisG

This is the exact arm position ,for an off road car. This position gives a little more (-) Camber and 70% suspension travel to compaction and 30% to lengthening .I think that it is the best you have.

The opposite position is ....the destroy of geometry .

If you use parallel with ground arms you would have 50% - 5o% to suspension travel .

If arms are parallel ( between them) you would keep (about ) the same Camber.


I hope that you could understand my 'english'.

VassilisG

Hi DV,

We are crazy homebuilder ( both ) but we have different way to do that.
I think ,how i can make absorbs and you what can i use like absorbs.

I like to make mine but i like , twice , to observe yours.

Dirty_Vinylpusher

Ah so long arm on the bottom and short on top, you say?
Interesting.

VassilisG

If you have a long suspension travel you can use a little sorter upper arm ,than the other.
Extra small upper + long travel = grate wobble of camber.
Medium small upper + long travel = a little wobble of camber
Extra small upper + sort travel = a little wooble of camber

Frederik_b

Actually if I understand correctly, you are making the upper arm longer, VassilisG if I look at your picture this is the opposite of what DV is attempting isnt it ? I see there is maybe something I never realized about suspension geometry, please let me know if it looks like I dont understand.

To me it looks like if the top arm is longer you will have reverse camber as the suspension compresses (the shorter arm will pull the wheel inwards compared to the longer one). see first drawing

Up to now I always thougth that if one arm would be shorter it would be better if it is the top one, so you gain some camber on suspension compression:



But Ithink it wont be too much of a problem anyway

Frederik

Frederik_b

Ok the posts you guys made while I was writing kind of cleared things up, so basically we are saying the same thing !

Fred

VassilisG

We are saying the same thing.
The upper arm must be shorter, like photo and your second drawing.

... and the angle between two arms adjust ( a little ) the Camber.

ivyspoppy

I guess the truth hurts

Dirty_Vinylpusher

Right....well.....time for some rejigging of this setup then.

Better get to it.

Frederik_b

It's the location of the shock that forces you to make the top arm longer ? Could you shape the upper arm a way that it could avoid the shock ?

The arm couldbe a triangle like

/!

or !\

instead of : /\

Dirty_Vinylpusher

Ah yes and no.
I mean this first setup was just a trial really, nothing too permanent.
I think the lower arm needs to be mounted a bit higher on the chassis anyway.

I'm off to the scrapyard and a couple of steel places now to see what I can find, adn will get stuck in to rebuilding this when I get home.
Might try to make the whole arm setup as a separate piece which I'll then attach to the chassis.


Later.

ttr125fan09

My Feedback: (1)

i got lost at camber, lol
im gunna try to make real a-arm for my build

QSPSB2

You don't necessarily need to have a shorter A-arm on the top to accomplish the same task either.. You can have identical upper/lower A-arms,, All you need to do is weld in an extension onto your lower A-arm.. And weld an extension onto the upper frame rail on your chassis... And attach the shock. In your case... Hmmmmm... Just attach it where it will work for your application..

here are few types you can look over..

da mad maori

good info frederick b....
very informative.. ill use that info on my next build

Dirty_Vinylpusher

Thanks guys..
Good pics.
It's a lot to get your head around for sure.

I got some bits today which will come in handy anyway.
Should see some progress by this afternoon.