When a fun job goes bad...

[Trevor Jessie]

Arggh. I have rebuilt several spridget front suspensions. When everything goes as it should it is a relaxing and "fun" job. For some reason the latest one is fighting me. I want go into all the problems that I have had to overcome, but I am a little stumped on this last issue (I hope it is the last issue). Here it goes:

The caster angle on the kingpin is placing it too close to the shock such that when the trunnion is installed it flexes the pin and causes binding of the swivel axle.

Here is what I've checked: king pin is correct, all bushings are fully seating, shock arm is not bent, no indication of accident damage, the a-arm seems straight and true.

I moved the other a-arm over, with its kingpin, and it didn't work either. I built up the tab slot for the inner A-arm fulcrum pin the raise the pivot of the front of the A-arm. That helped, but I can't take it any higher. None of the holes look enlongated from wear.

Do I shave the shoulder on the trunnion bushings? Mill the edge of the trunnion and the side of the shock arm?

I've had a few that were snug, but never one like this.

What about lowering half of the spring pan?

If I use a long pry bar and twist the a-arm to correct the caster the swivel axle turns freely... So I do not think it is "off" by much.

Any thoughts?

... I'll edit this and try to clarify things tomorrow after I've had some coffee, but right now there is another beer calling my name.

 

[JPSmit]

can you post a pic? - all I can think is that when I did mine, I had the trunnion (4a) 180 degrees out.

https://mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=29294

 

[Trevor Jessie]

No, my problem is with the front-back angle of the king pin (caster). I'll try to post a picture tomorrow unless I get fed up and fix it with the angle grinder (I've given up on the big hammer).

 

[jlaird]

That was my first thought, did that as well. But then I don't understand the question maybe.

 

[Trevor Jessie]

no, I've made my backwards trunnion mistake many years ago ... I've graduated to more frustrating problems.

 

[Trevor Jessie]

I knew there was a problem when it came time to put the trunnion on. The treaded part of the kingpin was touching the shock arm. There was no room for the trunnion. So... I pried on and it flexed the king pin enough to cause it to bind (the stub axle would no longer swivel). I added extra shims to be sure that the flex was causing the problem. I've improved the alignment somewhat, but I still need more correction to get the stub axle to swivel properly.

 

[JPSmit]

could it be a shock problem?

 

[Trevor Jessie]

I measured the offset of the end of the shock arm compared and compared it to three others. It they were within 1/16 of an inch, and was "off" in the direction needed to lessen the problem.

 

[jlaird]

The trunon should swivel preaty freely on the a arm. If not you have the fulcrum in too far (not centered) and it is binding as it trys to turn on the a arm?

 

[Trevor Jessie]

OK... I'm going to sleep on this. I don't think I'm doing a good job of explaining th problem. Thanks for the help... stay tuned.

 

[spritenut]

Trevor
Slightly bent A arm maybe? I had this same problem once, the A arm was bent but you had to study it real hard to see it.

 

[Biff]

Loosen the shock mounting bolts, offer up the trunion, put the trunion pin in and tighten, then retighten the shock mounting bolts.

 

[Trevor Jessie]

Thanks Frank, I thought that too, but the other A-arm caused the exact same problem.

Thanks Biff, I tried that. However, when I torqued the shock bolts it flexed the kingpin and cause the binding again.

I can get it assembled, but the force required causes binding.

I guess I'll try to find a way make some frame measurements.

I'm sure I can a way to make it work, but I'd rather "find the cause than treat the symptoms"

 

[DrEntropy]

TJ, is the kingpin new? Could it be slightly kinked?

 

[Trevor Jessie]

Kingpin is new and seems properly located on the fulcrum, and the fulcrum seems properly located in the a-arm.

 

[DrEntropy]

woof.

no, I've made my backwards trunnion mistake many years ago ... I've graduated to more frustrating problems.

My first thought on reading the original post.

Could there have been a mislabeling of the A-arms? I can't readily put my hands on a Spridget book ATM, but think p'raps the A-arms are at fault somehow.

 

[DrEntropy]

woof.

no, I've made my backwards trunnion mistake many years ago ... I've graduated to more frustrating problems.

That was my first thought on reading the original post.

Could there have been a mislabeling of the A-arms? I can't readily put my hands on a Spridget book ATM, but think p'raps the A-arms are at fault somehow.

 

[aeronca65t]

I don't have a heck of a lot to offer...it seems like you've looked at all the stuff I thought of.

But I will tell you that one of the "frame tabs" that hold the A-arm to the chassis, was bent on mine from accident damage, and I had to do some cutting and welding to get it right. The tabs are pretty thin and easily damaged.

Also, you have the fulcrum pin *fully* screwed in to the A-arm....right?

Just for kicks, I'll add the Moss catalog shot below in case anyone else has an idea

 

[jlaird]

Just to rule out all else is there another shock available just as a test fit.

 

[Trevor Jessie]

Ya know Jack, I just might have an extra old shock in the basement. I may dig it out.

Nial, the tabbed washers that came with my rebuild kit would not fit (tabs were too wide), but the circle seemed to seat properly in the frame tabs. I did some light work on that front frame tab to make sure it was locating as high as possible. That helped my problem, but did not cure it.

I guess I'll check the fulcrum pin again, but I'm certain it was screwed as far as it could then backed out until it aligned with the king pin. I then checked to make sure it pivoted properly without bottoming out the fulcrum.