Page 4 of 4

Re: Laying out A arms

Posted: 24 Dec 2014, 14:19
by steve
Just read right through this thread again.

So, looking at the nice drawings there does the centre of the OEM Mazda bottom joint need to be down the middle of the threaded part pointing up as if its assembled to the upright? What I mean is does this make a projection down to the correct point on a point to point drawing?

What I was wondering was how to get the ball joint in the correct position if I draw it out on a piece of ply, drill the 3 holes, bolt to inner rose joints to the table, build the box for the ball joint then where to place it to correctly centre the peice...

That make any sense?

Merry Christmas,
Steve

Re: Laying out A arms

Posted: 29 Dec 2014, 11:53
by bgkast
The lower ball joint is set at an angle to the lower A arm when looking at it from the front of the car. The angle is towards the center of the car to allow the ball joint to be centered while giving the proper kingpin inclination. This angle is somewhat built into the ball joints. When I was building my arms I made the ball joint box, installed the ball joint and when I placed it on the jig I just projected this angle down to the outer "point" on the jig for the ball joint location. You could also just center the circle of the ball joint over the point, In reality it doesn't matter much, the difference is only around 1/16" or so and you can adjust the inner heim joints to account for it.

Re: Laying out A arms

Posted: 09 Jan 2015, 11:28
by steve
Thanks, building the box was what I'm planning, just wondering where to position the ball joint centre before welding the arms in.

Got it now. Just need an upright to get the threaded bit pointing in the right direction :D

Steve

Re: Laying out A arms

Posted: 09 Jan 2015, 12:56
by bgkast
If you center the ball in it's travel, and place the ball joint in it's box with the inboard edge vertical it should give you a very good idea of the angle without needing the upright on hand.

Re: Laying out A arms

Posted: 19 Mar 2015, 13:22
by bgkast
For the upper rear arms I assume the outer point (labeled as outer balljoint in figure 24.30) is the center of the U shaped bracket detailed in Figure 24.33?

Re: Laying out A arms

Posted: 19 Mar 2015, 19:03
by Midlana1
Correct.

Re: Laying out A arms

Posted: 30 Sep 2018, 00:32
by DavidIt
freakynami wrote:And the result...
AArms04_5.png
hi, i would like to draw my arms too because i have different tube size and plate thickness.
i cannot find the information about where is located the balljoint's centerpoint relatively to the 'box'.
looking at figure 24.16 (2th edition, center-to-center dimensions) can be useful know the distance between the back of the "tab B) (side welded on tubes) and the balljoint centerpoint.

thanks,
David

Re: Laying out A arms

Posted: 24 Oct 2018, 06:05
by DavidIt
thanks to "Camber Dave" from Locostbuilders.co.uk forum, i got this informations:
horizontal bolt to center bolljoint: 28.61mm (1.1/8" )
From the horizontal bolt to the vertical bolt is 47.6mm (1 7/8" )
The included angle between ball stud and base plate is 70 deg.
maybe can be useful to somebody else.
David)