Laying out A arms

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bgkast
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Re: Laying out A arms

Post by bgkast » 21 Mar 2014, 10:51

That's the primary reason I am drawing it out first.

Langan
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Re: Laying out A arms

Post by Langan » 21 Mar 2014, 14:13

I figured you did was just trying to follow along. Your are doing a great job. Good luck

bgkast
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Re: Laying out A arms

Post by bgkast » 21 Mar 2014, 14:47

I think they will end up looking very similar to yours! Based on your experience should I keep the upper ball joint inline with the A arm (when looking at it from the front) or should it be angled one way or the other to prevent limiting out it's travel?

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Re: Laying out A arms

Post by Midlana1 » 21 Mar 2014, 14:53

I suggest welding the tab on at about a 10 degree angle... helps keep the bearing centered after you dial in ~8-9 degrees castor.

Langan
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Re: Laying out A arms

Post by Langan » 21 Mar 2014, 15:47

I agree with Kurt
My car ended up the way it is because I build mind blind meaning I did not have suspension points before I started. Went against every building traits ever. Followed along with Kurts build to help with book. Turned out fine but I worried all the way.
Not sure if I had known were points would be I would do it same way. I went outboard shocks because Kurt went inboard just to show others. Since its not realy an A arm if viewed from top it lends itself to push rod. An A arm shape by moving front mount forward leaves room for shock but trade off is longer nose.
So I left bottom arm same just moved shock to rear and clearanced top arm. For me best for what was already built. Traveled it through all steps before welding. Each build will learn from the last.
Kurts design has proven itself sound so I think if you keep pickup points were they are you can do anything you want between the points.
You are a good builder and ask the rite questions. Can't wait to see yours done.

bgkast
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Re: Laying out A arms

Post by bgkast » 21 Mar 2014, 16:36

For the upper arms im planning to use an ES2074R ball joint, and a hybrid between Jim and Kurt's a arm design like so:

Image

The front Will be very similar to Jim's arm with the curve to get around the spring), and the back will have a 1/4" thick tab (red) with a clevis and link (green).

So when looking at the side view of the arm along the axle line the tab should be welded about 10 degrees up from the plain of the arm?

Edit: since I am using the ball joint instead of a spherical bearing I can just turn the ball joint as needed, right?

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Re: Laying out A arms

Post by Midlana1 » 21 Mar 2014, 17:46

Yes, in that version you don't have to worry about the misalignment... HOWEVER, you always, always have to confirm that every suspension pivot cannot bind at the limits of travel. Just sayin'

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Re: Laying out A arms

Post by Langan » 21 Mar 2014, 18:07

How about just use a spherical ball with no adjustment and a joint at the red bracket like Kurts. You would need less bend and gain more room to stand shock up rite more, still have plenty of camber adjustment and castor adjustment. Easy roll center adjustment.

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freakynami
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Re: Laying out A arms

Post by freakynami » 21 Mar 2014, 23:25

Midlana1 wrote:...check the physical size of the OEM Miata ball joint housing and confirm whether there's room for it within the outboard box assembly...
Yep, you mentioned that in the book, and I had a very slight interference in the CAD, so for good measure I've extended it all by about 0.100" to it should clear now. There were a few small variations I noticed with the CAD geometry (I downloaded the ball joint as I don't have one to measure) so I fully expect to have to adjust the box a bit when I have the real parts on hand. Nothing that a bit of grinding or percussion adjustment won't be able to fix :)

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Re: Laying out A arms

Post by bgkast » 23 Dec 2014, 13:09

This should come in handy for the lower rear A arms:

Image

http://steinjager.com/shop/index.php?ro ... tierSeven=

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