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ST4 Tracks & Sprockets

Puckle

Well-known member
SUPER Site Supporter
Most of the restoration work on my ST4 is now complete, except it really needs new tracks & sprockets. I did make a start on this but got sidetracked buying another ST4 off E-Bay - it was too cheap to ignore at 650 quid so I'm now the proud owner of 1962 ST4 330
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This, as you can see, is in similar condition to the last one, except that the gearbox is ok, and, after a bit of tinkering and fitting a new exhaust valve, the engine is a runner too. The worst bits are the tracks - rubber is rotten, and most of the track guides are as well, so I have made a start on fabricating some new ones.
I have made a few jigs for cutting, drilling, folding and welding 3mm steel strip, but it is a bit of a task - the top of the guide is a complex compound curve and the only way to do this is to fold it over a suitable dolly made from 2 pieces of 20mm steel, clamp in place with a matching clamping piece made from a single piece of 20 mil then cold form the curves with a hammer - each guide needs about 100 blows so to do a full set that's 32,000 hammer blows! - i'll have arms like Popeye.

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The good new is these are only costing about £1.25 in material, and I can get all 320 powder coated for about £100, so much cheaper than trying to buy new even if you can get them.

I've been experimenting with casting the sprockets as well - so far only in aluminium as its easier to work with, but results are promising - I've over estimated the shrinkage factor at 2%, so need to re-work the pattern to approx 1.5% before having a go in bronze
 

redsqwrl

Bronze Member
GOLD Site Supporter
Well, If I can assist. I can get new two band wheel guides from couchloafer (FF member) for $10 plus or minus a couple bucks ( US )

I have bought many and you are right there are many hammer blows necessary to straighten one.....

Kevins wheel guides are perfect, galvanized and generally in stock ready to go out the door quick.

That mold is looking awesome. Keep up the good work. we just did a group buy and many Snow trackers bought in. if you go into production post up, I would be willing to snag another spare pair.
 

3512b

Junior Member
GOLD Site Supporter
I had a st4 with a winch like that.. it’s a sad story On the ST4
Always trust a friend
but get cash up front.........:( plus 10% aggravation fee.


does that have the Bronze St 25 ?
mine did it’s all I have left and some track guides l, grozers and parts of the varator the frame got made into a sled
 

Puckle

Well-known member
SUPER Site Supporter
Well, If I can assist. I can get new two band wheel guides from couchloafer (FF member) for $10 plus or minus a couple bucks ( US )

I have bought many and you are right there are many hammer blows necessary to straighten one.....

Kevins wheel guides are perfect, galvanized and generally in stock ready to go out the door quick.

That mold is looking awesome. Keep up the good work. we just did a group buy and many Snow trackers bought in. if you go into production post up, I would be willing to snag another spare pair.
Hi Redsqwrl, thanks for the offer, but even at that price it would be over £3k for a full set shipped to the UK and I reckon I can do a set for less than £500 including powder coating - now I'm retired I've got the time to make them.
I'll let you know how the sprockets work out - watch this space!
 

Puckle

Well-known member
SUPER Site Supporter
I had a st4 with a winch like that.. it’s a sad story On the ST4
Always trust a friend
but get cash up front.........:( plus 10% aggravation fee.


does that have the Bronze St 25 ?
mine did it’s all I have left and some track guides l, grozers and parts of the varator the frame got made into a sled
Hi 3512b, did your winch have the drive motor? mines missing and I can't see where it should be fitted - do you have any photo's?
 

DAVENET

Bronze Member
GOLD Site Supporter
One kicking wasn't enough? :) Very cool that it has the winch - and I can't believe everyone hasn't lost their minds yet over the HIGHLY coveted Hella beehive directional lights.
 

3512b

Junior Member
GOLD Site Supporter
Hi 3512b, did your winch have the drive motor? mines missing and I can't see where it should be fitted - do you have any photo's?
It had a 6 Vt DC drive motor and I Iwill dig around and see if I have any pic it’s was a pretty Rube Goldberg set up
 

3512b

Junior Member
GOLD Site Supporter
sombody will flip em I hope
dont think the motor was the right one but that what was with it the mounting was pretty cob up
 

redsqwrl

Bronze Member
GOLD Site Supporter
the fluted pulley is a capstan.

Wrap a rope around it a 1/2 dozen times or so and give it a gentle pull, the rope sinches (sp) tight and it will pull onto itself when you let off the tension the rope will just slide around. You have great control wet or dry. the number of wraps are your pull effort. I only saw one actual ST winch in the wild. it was driven off the main motor. I saw it on the dome outside of ninilchek AK.
 

Puckle

Well-known member
SUPER Site Supporter
The winch was a factory fit (Kenth sent me a copy of the sales ledger) but I don't know if it was electric motor powered or driven by the engine somehow. I have modified a car starter motor for now to power it, just need to figure out how to mount it.
Yeah, I noticed those indicator lamps on the E-Bay listing and though someone would bid up just to get them - unfortunately one of the lenses is broken and half is missing but my son reckons he can 3d print one in translucent resin so I'll see how that goes.
 

Puckle

Well-known member
SUPER Site Supporter
Finally got the 350 track guides made and galvanized, a lot of work but not too difficult, and I ended up at a unit cost of £1.10 each.
Making the bands has been much simpler, I made a drilling template out of 10mm plate and used a cutter made from an old VW exhaust valve stem in a battery drill and it flew through the job.
I am now looking at making some grousers, but the cost of EN45 (5160) spring steel is a bit exorbitant - I've been quoted £1,500.00 for enough to make a full set.
My son has come up with a 3d printed split pattern for the drive sprockets but not got round to casting any yet - I think the sand I have got is a bit crap and won't part cleanly - I get some oil bound sand and try again.
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Puckle

Well-known member
SUPER Site Supporter
I have had 200 of these new grousers laser cut and pressed from STRENX700, a structural steel with a yield strength similar to spring steel but easier to work with - I can now weld on the center winglets for the tyres to run on without worrying about stress cracking post weld. I decided against going for a two part grouser with a center strip as per the originals as this creates a major rust trap that is difficult to get paint or galv into - its really the reason the old ones are scrap as they have rusted from the inside out.
Not sure whether to taper the up-turn to either side - Lyndon said this helped a lot with turning in the original grouser design, but I see the people who are making the "new" snow-trac have opted for parallel grousers as do other manufacturers.
These have cost £6.58+vat each so far and I will powder coat them after welding so should cost less than £10 each - just hope they are strong enough as I have read of people spending hours making these only to have all of them fracture in a very short space of time!
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Snowy Rivers

Well-known member
Absolutely great set up.......I like the assembly line approach for drilling the belts.....

Grousers have been manufactured from all sorts of materials over the years, Formed channel, box tubing, steel angle....even wood.

What makes the big difference is the size (Width of the grouser) and the weight of the machine....also how the cat is used too...

Rough running over soft material...Snow, or soft earth is pretty benign.....Rocky terrain is tough on tracks..no matter how good the materials are.

Looking great......
 

mlang2005

Member
There’s a lot of pull on the grousers when they go around the gear and front tension wheel, if they are flexing as they go around they will crack eventually. Seems like most modern grousers are tall and triangle shape to make them stiff. Over tension tracks would exasperate the flexing.
 

Puckle

Well-known member
SUPER Site Supporter
Yeah, there are pictures of one in Germany where that happened - they made a great job of fabricating them but then drilled holes in the centre of the upstand so they could bolt in polyurethane pads (legal requirement for driving on road there I think) and every one snapped across that hole.
 

alryA

Well-known member
If you look at the shape of modern grousers, compared to those of yesteryear's. There is a reason some shapes are no longer used.
 

Snowy Rivers

Well-known member
Yes
The tracks take a beating
The smaller tracks are less prone to the destruction
The big wide tracks found on the 2100 and 3700 Thiokol and LMC cats are tough on tracks
 

Puckle

Well-known member
SUPER Site Supporter
I've got the grousers back from the powder coaters and have finally started assembly of the tracks - looking good so far.
I removed the old tracks so as to remove the old sprockets and these have been cut up to be melted down to make new ones - the new ones are quite a bit thicker than the old so I bought some ingots of silicon bronze and added approx 3kg of additional material to each sprocket. I found a good trick to help with track removal was to put a couple of spare wheels onto the upper shock absorber mounting with some M12 threaded rod - it really helped roll the tracks off and stop them snagging all the time.
I had to upgrade my furnace to burn diesel as it wasn't hot enough on propane only, it then made short work of melting the bronze and was ready to pour in less than 50 mins - bit scary working with 900'c liquid, especially when the first pour blew the mould apart as I hadn't screwed the two halves together but it went well in the end and I now have 4 new bronze sprockets.
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300 H and H

Bronze Member
GOLD Site Supporter
I must have missed something...
There is not a brake drum in the center of the sprocket.
You have brakes I am sure. Just wondering...
 

Puckle

Well-known member
SUPER Site Supporter
Well, turns out not tapering the grousers was a mistake - they make sliding the tracks in a tight turn too heavy going and overloads the variator mechanism - my belt just disintegrated in the end. Probably ok on snow but maybe not on Ice - as I have to use mine mostly on grass I will need to strip down the tracks again and cut back the grousers - bummer

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