[T3] Lead Sled Update....

John Jaranson jaransont3 at comcast.net
Wed Jan 2 21:52:28 PST 2013


On Jan 2, 2013, at 11:57 PM, Jim Adney wrote:

> On 2 Jan 2013 at 22:13, John Jaranson wrote:
> 
>> With this in mind, here is a drawing of my latest plan....
>> 
>> http://www.carartbyjohn.com/2013JaneBuild/Type3AirRide.jpg
> 
> That puts some additional side force on the inner journals:force that 
> wasn't there before. You may need to beef up that bearing a bit.
> 

Good point.  I will look into making the thrust bearing also a rotational bearing and add a thick doubler to the support bracket.

> I see that you've cut windows in both the front and back of the beam, 
> but you really only need them in front. Welding metal over the rear 
> cutouts would put some strength back in there.

That is just an old rusted out beam that I am using as a mock-up/exploratory surgery victim.  The final beam would only have a cut-out on the front side.  I would also add a doubler plate around the opening to beef it up.  It would also hold a couple of rubber flap seals to keep most of the water out.  I will have to provide a couple of drain holes for the water that will inevitably get in there.

> 
>> Basically this eliminates the lower torsion bars and replaces each with its own airbag.  The airbags would be mounted between a bracket attached to the beam (not shown) and the bag arm shown in yellow.  This arm is attached to the inside end of the trailing arm through a custom adapter insert.  The added thrust bearing acts on the bushing support already in the beam assembly shown in this picture...
>> 
>> http://www.carartbyjohn.com/2013JaneBuild/Type3AirRide2.jpg
> 
>> I will probably weld the adapter insert along with using the shear pin just to make sure it doesn't move.
> 
> Yeah, I wouldn't want to trust that shear pin to hold, but you'll 
> have to be careful with the weld, because I suspect the journal there 
> is hardened. (And if it is hardened, welding could cause problems in 
> the adjacent HAZ.)

Yeah the heat affected zone is a concern.  I have also thought about machining some castellations in the end of the trailing arm and matching ones in the adapter to mechanically transfer the torque.  The shear pins job would then be to counter the much smaller thrust loads.

> 
> You really need something to securely hold your new inner arm from 
> coming loose from the torsion arm. Maybe a big set screw in a dimple 
> will be sufficient, but it needs to be thought out carefully. You'll 
> probably want to put a radius where the adaptor goes from round to 
> square, to try to make sure it doesn't shear off there.  

Have also considered using a hexagonal pin instead of square to reduce the stresses at the transition.  A big radius there will also help with the transition. I have also consider slotting the end of the arm and putting a clamp bolt in there.....not unlike the clamp bolt that holds the ball joints in.

> 
> Interesting concept. Will this stick into the spare tire well, or 
> will it clear to the sides? (Or does that well even exist on the Lead 
> Sled?)
> 

It will certainly stick into the bottom of spare tire wheel.  The top of that well is one of the places I have been considering for the air tank and air compressor.  The spare tire will just sit on top of the fuel tank, probably on a bracket.


Later,
John Jaranson
www.carartbyjohn.com


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