radius rod help

AA Ford Discussion Group relating to the repair and restoration of your AA Ford.
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njcar757
Posts: 67
Joined: March 4th, 2009, 4:00 pm
Body Type: closed cab
Model Year: 1929

radius rod help

Post by njcar757 » June 25th, 2017, 6:42 pm

I'm restoring a 29 AA, last year I removed the front axle, dismantled it completely, sandblasted, primer and paint, reinstalled it, I did not check caster angle. The wishbone is not bent or damaged in anyway. I have read that there is no front or back to the axle. The king pins are new, and the spring perch shaft and the hole in axle are not wore out. I rebuilt the radius ball with all metal parts. Now I have checked the castor angle with an angle degree finder and a carpenters square on the floor and I have zero degree castor. I measured this close to each king pin and in center of axle, all the same.
I really need your help
thanks nick c

Stakebed
Posts: 1082
Joined: June 14th, 2007, 7:29 pm
Body Type: Grainbox
Model Year: 1929
Location: Illinois

Re: radius rod help

Post by Stakebed » June 26th, 2017, 2:02 pm

How's your front spring and shackle? In guessing your front spring has sagged...

njcar757
Posts: 67
Joined: March 4th, 2009, 4:00 pm
Body Type: closed cab
Model Year: 1929

Re: radius rod help

Post by njcar757 » June 26th, 2017, 4:32 pm

The shackles are new, if the spring was sagging I think it would have some positive castor? Is it true that there is no front or back to a model aa axle?
thanks nick c

Stakebed
Posts: 1082
Joined: June 14th, 2007, 7:29 pm
Body Type: Grainbox
Model Year: 1929
Location: Illinois

Re: radius rod help

Post by Stakebed » June 26th, 2017, 8:37 pm

28/29 front axle is same as cars - spindles and spring perches are AA specific tho - spring perches should be cast AA-XXXXX number in them.

think of the front axle as this:
Take a compass (thing that draws perfect circles - pencil in one hand and sharp stationary point in the other), imagine the stationary point is the wishbone ball - it doesn't move only rotates. The front axle is like the pencil and moves in an arc. The wishbone and axle are locked together so as the axle moves down you get negative castor and if its flat against the frame its neutral with a bit of positive castor. AS you can imagine your front spring must keep the axle a set distance away from the frame to maintain that 3* negative castor - if its sagged it becomes more positive

Stakebed
Posts: 1082
Joined: June 14th, 2007, 7:29 pm
Body Type: Grainbox
Model Year: 1929
Location: Illinois

Re: radius rod help

Post by Stakebed » June 26th, 2017, 8:39 pm

FYI most springs especially 28/29 are broken sagged or incorrect replacements - they are 12 leafs just like the standard A's and the standard A's will fit but will be too weak. The AA 12 leaf are thicker leafs thus can handle the loads more (and extra heavy frame etc) but AA's weren't treated nice over the years and many were overloaded and 85+ years has taken thier toll on them.

njcar757
Posts: 67
Joined: March 4th, 2009, 4:00 pm
Body Type: closed cab
Model Year: 1929

Re: radius rod help

Post by njcar757 » June 27th, 2017, 7:28 am

Very interesting, now we're getting somewhere. From what I've read, with a positive castor the top of the king pin leans back, with a negative castor the top of the king pin leans forward, is this correct?
thanks nick c

njcar757
Posts: 67
Joined: March 4th, 2009, 4:00 pm
Body Type: closed cab
Model Year: 1929

Re: radius rod help

Post by njcar757 » June 28th, 2017, 10:45 am

Stakebed, are you sure that its a negative 3* castor that I need, that means the top of king pin would be tilted to the front?
I really need your input, thanks nick c

Bob C
Posts: 1087
Joined: April 24th, 2003, 11:50 am
Body Type: Mail truck, Stake tr
Model Year: 1931
Location: SO CAL

Re: radius rod help

Post by Bob C » June 28th, 2017, 4:19 pm

This you tube video may help get a better reading https://www.youtube.com/watch?v=1NOwQzOWNTU
Is the cab and bed mounted on the chassis and you have the correct size tires on a level floor.

Bob

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