The Ford Barn

MikeK · 08-18-2016, 12:35 AM

I agree with Floats in post #6. Check the caster.

The question with "death wobble" is do you want to fix the symptom or do you want to fix the root problem? Ever wonder why one Model A with everything worn and loose in the front end does not wobble, yet another A with one little thing slightly loose shimmys like crazy?

To fix the symptom just make sure everything in the front end is a tight as possible. Then keep your fingers crossed. You are only holding tight a wheel that wants to shimmy.

To fix the actual problem so the wheels do not want to shimmy in the first place there is really no mystery. If it shimmys something is usually BENT affecting caster. Tightening everything up to new spec certainly improves steering and tracking but does not address geometry errors that induce resonance like shimmy. If you have a bent axle, bent forgings at either end of the wishbone, engine misalignment (the wishbone bolts to the fly cover casting at the back) or frame twist and bend you do not have the factory spec 2 degrees caster. Simple visual inspection likely will not reveal a bend of only a degree or two. You need to carefully measure.

Think of a shopping cart. When the front wheels get slightly bent back from slamming curbs and parking lot divots, you get a cart with a front wheel that goes into the dreaded "death wobble".

80 years of pounding pot holes and RR tracks bends both the axle, shackles, and wishbone in the negative direction. Reducing caster just one degree from the factory spec'ed 2 degrees will make wheels want to shimmy.

There is a lot of info out there about how to straighten an A axle, but not much about the wishbone. The front forgings that hold the kingpin actually bend rather easily compared to the axle. Perhaps someone has the Ford print for the wishbone and can throw in a few angles and dimensions?

Synchro909 · 08-18-2016, 06:14 PM

Quote:

Originally Posted by Rex_A_Lott

So what was the problem, and how did you fix it?

My biggest problem is I couldn't find anything specific. My cure? A damper on the tie rod.
When these tyres are worn out I intend putting radials on it. (Maybe that should read UNDER it!!

) I will then recheck and reassess everything.

Art Newland · 08-18-2016, 08:10 PM

My coupe has done this a couple times, but at the same two places! What I noticed was it only did it when first driving it. If the tire pressure had gotten a little low, going around a big right hand corner, the flatspots on the tires would end up 180 degrees out of sync. It would start the back and forth rocking that started the wobble. A little more speed and it quit. If there is 35 psi in the tires, it doesn't do it. Now maybe if the front end was in better shape it wouldn't do it at all?

SSsssteamer · 08-18-2016, 08:46 PM

Quote:

Originally Posted by Synchro909

I've looked in catalogues and can't see them listed. Are they still available? What have others done?
PS. I would have no objection to putting a 2 tooth column in if I could get one. They're as scarce as rocking horse $#!T. (RHD)

Steering Dampers are still available. After years of trying to sort out a wobble, I recently put one on our 1911 Stanley. Find a damper at: http://www.macsautoparts.com/ford_mo...tabilizer.html

08-18-2016, 12:35 AM	#21
MikeK Senior Member Join Date: May 2010 Location: Windy City Posts: 2,919	Re: Steering Damper I agree with Floats in post #6. Check the caster. The question with "death wobble" is do you want to fix the symptom or do you want to fix the root problem? Ever wonder why one Model A with everything worn and loose in the front end does not wobble, yet another A with one little thing slightly loose shimmys like crazy? To fix the symptom just make sure everything in the front end is a tight as possible. Then keep your fingers crossed. You are only holding tight a wheel that wants to shimmy. To fix the actual problem so the wheels do not want to shimmy in the first place there is really no mystery. If it shimmys something is usually BENT affecting caster. Tightening everything up to new spec certainly improves steering and tracking but does not address geometry errors that induce resonance like shimmy. If you have a bent axle, bent forgings at either end of the wishbone, engine misalignment (the wishbone bolts to the fly cover casting at the back) or frame twist and bend you do not have the factory spec 2 degrees caster. Simple visual inspection likely will not reveal a bend of only a degree or two. You need to carefully measure. Think of a shopping cart. When the front wheels get slightly bent back from slamming curbs and parking lot divots, you get a cart with a front wheel that goes into the dreaded "death wobble". 80 years of pounding pot holes and RR tracks bends both the axle, shackles, and wishbone in the negative direction. Reducing caster just one degree from the factory spec'ed 2 degrees will make wheels want to shimmy. There is a lot of info out there about how to straighten an A axle, but not much about the wishbone. The front forgings that hold the kingpin actually bend rather easily compared to the axle. Perhaps someone has the Ford print for the wishbone and can throw in a few angles and dimensions?

08-18-2016, 08:10 PM	#23
Art Newland Senior Member Join Date: Mar 2016 Location: Lynden, WA Posts: 1,564	Re: Steering Damper My coupe has done this a couple times, but at the same two places! What I noticed was it only did it when first driving it. If the tire pressure had gotten a little low, going around a big right hand corner, the flatspots on the tires would end up 180 degrees out of sync. It would start the back and forth rocking that started the wobble. A little more speed and it quit. If there is 35 psi in the tires, it doesn't do it. Now maybe if the front end was in better shape it wouldn't do it at all?