M3 Halftrack suspension spring compression tool needed

[maple_leaf_eh]

Folks, who has worked on an M3 halftrack's rear suspension lately?

From Nick at the Cold War Collection:

"Hey gang, to replace the road wheels, I thought I could get away with a work around...no such luck, I need to compress the vertical springs to take the load off the bogie chassis (I don't feel like getting smashed in the face by a bouncing spring.....so)

If you see note AA in the drawing above, there is a female thread inside the base of the spring, and a hole in the top of the cast support arm accessible once the return rollers are removed. Two threaded rods are spun in, and a nut and drive washer combo used to pull up the springs, safely.....taking the pressure off to drop the road wheel bogies out.

All the references I have located have called this threaded rod, a "special tool"...and yes, I'm sure it is , but there is a lack of actual specs ....

I'm asking for help to reach out to folks on your MV contacts list to obtain the thread type so we can source rod locally...or....if we could buy the twin rod tool even. I can't easily tell if its UNF or UNC, but, it looks fine pitched.

This is a track install show stopper for us, so, if you have any time at all to do some research, that would be terrific ! ...."

Can anyone help us, a) locating the tools, or b) selling us a pair? Other conversation has zero'd in on using Grade 8 threaded rod if we are going to make one, and using hand tools not impact wrenches.

[David Herbert]

Please note that the thread will not be either UNF or UNC ! They hadn't been standardized then but were based on AF and AC standards which were the ones in use in WW2 USA. Most threads are effectively the same but not 1" fine which these bolts might be (Sherman ones are 1" AF). 1" AF is 14tpi and UNF is 12 tpi so they will not fit together. There is another smaller size that is different too but I can't remember what it is now - I blame it on dementia !
David

[maple_leaf_eh]

Originally Posted by David Herbert

Please note that the thread will not be either UNF or UNC ! They hadn't been standardized then but were based on AF and AC standards which were the ones in use in WW2 USA. Most threads are effectively the same but not 1" fine which these bolts might be (Sherman ones are 1" AF). 1" AF is 14tpi and UNF is 12 tpi so they will not fit together. There is another smaller size that is different too but I can't remember what it is now - I blame it on dementia !
David

You are a wise man! Worth investigating. I posed the same Q on Facebook and got a flurry of responses from Keyboard Master Mechanics. Most encourage us to 'go to the hardware store and get a piece of threaded rod'. Ummm? No. Too many variables, especially spring force and risk of injury to be imprudent. Use the correct tool correctly.

For something so fundamental, there has to be a straight forward solution. And for your entertainment, our neighbour in the Green Disease hospital ward offered the following.

https://www.youtube.com/watch?v=E4-M...p=desktop#menu

[David Herbert]

Not wise, just done it before !

The funny thing is that the guy building up the Sherman VVSS bogie didn't need the spring compressors. If he had just put the bogie upside down and put the bits in in the right order they sit down well enough under their own weight to start the nuts on the six studs that hold it all together. Then just tighten down the middle ones followed by the four end ones and job done. He was quite correct not to lubricate the bushes and pins because the grease mixes with grit and retains it where as running dry the dirt falls out and there is actually less wear. However I would have greased the studs and nuts as rust build up can make these very hard to dismantle.

Building up a bogie that is bolted to a tank is slightly easier with the compressors but the need to take the skid off the top to get them in is I think more trouble than it is worth so I balance all the suspension arms, equalizers and springs on a trolly jack and use that to lift them into position. It is quite possible to do that by yourself as long as you don't rush at it.

I would expect that half track ones can be done the same way but not with the tracks on and you would need to jack up the vehicle without tipping it sideways. However I have only built up half track suspensions once and that was 40 years ago and I can't remember how I did it ! Getting tracks onto half tracks is fun too but mind your fingers !

David

[maple_leaf_eh]

It seems Gary of Gary's Halftracks has retired, and his daughter has taken over the business. She had the tools we needed, and they are expected to arrive before week's end. Thank you all for your attention and suggestions.

When we get the volutes compressed and the tracks reinstalled, and the tool goes into the vehicle's kit, I will post the answers to my own questions. Dimensions, diameter, coarse or fine, TPI and grade if known.

[maple_leaf_eh]

Friday afternoon Nick circulated pictures of the correct tool being used correctly. A supplier came through with a pair of 1" diameter rods with threads on both ends, and a square end for turning into the blind hole.

Second search item. The M3 is going back together nicely, and it is time for a few road handling improvements. Att is a shot of the cracked plastic steering wheel. Yes, they can be repaired but .... doing this restoration justice means not reinstalling broken or damaged parts. Does anyone have a good US Autocar halftrack steering wheel and horn assembly?

[BCA]

The plastic steering steering wheel as shiwn in your photo is ultra rare but I do have the steel spoke style steering wheel (NOS). PM me for details. The horns were paired: a hi tone and a low tone that made very impressive sound: but they are scarce. I make have a close substitute low tone horn.