[T3] Lead Sled Update....

[Bobsnotch at aol.com]

In a message dated 1/3/2013 12:52:34 A.M. Eastern Standard Time,  
jaransont3 at comcast.net writes:

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.
 
John, are you looking at using a wire EDM to put the hole in the trailing  
arm for the shear pin? I'm only asking, as that part of the trailing arm 
should  be hardened steel. I think it might be better to go out the full 
distance, and  grab the end of the trailing arm like the stock set up, and maybe 
set up a  pillow block next to the end of the air bag arm, so you're not 
twisting the end  of the shaft off. I do like the concept, but setting up the 
trailing arm shaft  assembly is still going to need a little more thought, as 
you only have so much  room to play with, and the trailing arm is splined. 
You might want to see about  doing some 3D animation on it, along with a 
little stress testing. ;-) Nice  concept though, and it might just work. : )

Bob 65 Notch  S w/Sunroof and IRS aka Krusty
64 T-34 Ghia aka Wolfie
71 Square-vert  under construction
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