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Snow Trac replacement BRONZE drive sprockets

300 H and H

Bronze Member
GOLD Site Supporter
Most likely 5-11% this is what some bearing bronze has in it

I kept thinking 1/5 or 20%... But maybe it was that I was remembering the 5 and it was 5%, and that could be...

If I remeber correctly isn't there a hard and soft bronze bearing material? The harder stuff you need to grease it when wearing on a steel shaft. The softer material you don't need to grease to keep it from wearing on the shaft, even without grease. I coud be wrong about that...

These J&K castings are quite yellow more like the color of brass btw. I've had them for several years, and they don't seem to darken with time, in the corner of my shop anyway.

Lets hope the mold is avalilable, and your able to secure it.

Regards, Kirk
 

jask

Member
I need to check through my "book" but I am fairly sure these are silicone bronze- much harder and more durable than bearing or aluminum bronzes.
 

JimVT

Bronze Member
GOLD Site Supporter
when I bout mine I ordered 5 . one just incase something like this happened. he called them silicon bronze and told me to use that wire to weld on them.
 

jask

Member
I was talking to one of my favourite welders here in town about the idea of TIG welding repairs and she told me about another fabricator who has been doing some small scale casting and foundry work. I am meeting with him next week to look at patterning a drive sprocket. He said silicone bronze is a more advanced casting metal and has a narrow temperature window and is prone to casting shrinkage and voids if overheated... and since the pattern I am bringing him shows signs of being hot and has shrink voids, I am looking forward to seeing what he has to suggest :) The new alloys are actually harder than the old silicone bronzes and he did not think this would be an issue with old ( not easily replaced..) grousers.
Will let you know as things develop.
Jim I will PM you about possibly getting some pictures of your "new" sprockets as mine are worn on both sides and it would be good to have some measurements to properly "clock" the drive teeth.
 

300 H and H

Bronze Member
GOLD Site Supporter
when I bout mine I ordered 5 . one just incase something like this happened. he called them silicon bronze and told me to use that wire to weld on them.

And yours are from were? Are they J&K from North Pole AK.?

You bought yous before I bought mine. But I was thinking those you have were from a thicker mold that Lyndon had??

Details please:flowers:

Regards, Kirk
 

billa

New member
Manganese bronze. Cu55%+,Zn 38%+, strong and tough used for landing-gear and tail-skid castings, Tensile strength 65000 psi, shrinkage 1/8 to 11/64 in/ft (range for Al and Mg) Hard Bronze SAE Standard 62, Cu and Tin mostly-Good for severe conditions and heavy pressure, used for gears and bearings. Tensile=30000 psi and then Phosphor Bronze.(Cu, Sn, Pb) Resistant to wear and scuffing. Tensile 30000 psi and then there's Cast Aluminum Bronze SAE Std 68. Used in gears,etc. Tensile as-cast 25-50000 psi (2 grades). All this sounds like a job for an experienced Foundry man. It would be fun to draw it, print it and CNC the pattern on a mill(and make the teeth wider maybe). Damn I can almost see that dream shop from here.
 

JimVT

Bronze Member
GOLD Site Supporter
I bought 5 from north pole and are stock ones . But the mold he had has the centering tabs moved or changed some. He told me this when we talked on the phone.
It had something to do with the fitting when they made the mold. I wished I knew what machine they were working on.
The inside centering tabs were 1/8 inch to small for the rubber covered ice drum.
The drum fits loose over them.
So I welded a bead on top of each tab that holds the drum.
It works ok.
It is a little more work but an easy fix. It was Easier than drilling the holes in them.
I also have a set of the heavy brass and other worn out ones. I collected them from my friends years ago and was going to build something.
jim
 

vintagebike

Well-known member
Does someone have some shots of the various stages of sprocket wear? The good, the bad and the ugly? Just about to start on an EcoTec conversion of our 1959, seeing the success Louis has had.
 

alpinenut

New member
The replacement bronze sprockets by J&T Foundry in North Pole were cast from Silicon Bronze, Alloy CDA 873 Everdur, with composition
Copper 95%
Silicon 4%
Manganese 1%
 

teledawg

Member
I have a set of 4 NOS ST30A drive sprockets for 2 band machines that would be good candidates to use for making a drawing or pattern from. :whistling:
 

JimVT

Bronze Member
GOLD Site Supporter
4 heavy brass and a stock.
DSC00229.jpg

DSC00228.jpg
 

couchloafer

Member
SUPER Site Supporter
I have a set of molds for the 3 or 5 band I got from Bob Canton that can easily be modified for the 2 band. If anyone is interested I can get a price from the local foundry.........
 

redsqwrl

Bronze Member
GOLD Site Supporter
this is good news.

any one have a three band and two band sprocket to compare?
 

Snowtrac Nome

member formerly known as dds
GOLD Site Supporter
what needs to be done to modify the sprockets for 2 band the 3 band sprockets look a lot more robust
 

couchloafer

Member
SUPER Site Supporter
I have both two and three band to compare to. These are the thicker ones.
 

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redsqwrl

Bronze Member
GOLD Site Supporter
Alright my ignorance and inexperience is going to come shining through....

in post 43 Jims sprockets look to be wide or chamfered where they meet the rubber drum.

Kevins CPST52 sprockets look flat as compared to the red one standing there.

I assume the little knobs are for alignment.

the three band sprockets look to be quite flat as well.

Question here:

Does the 3 band sprocket fit on the two band machines?

Does the rubber coated hub meet up with that raised area?

Does it need to.

I assumed the rubber drum with the spiral flute running through it was some sort of an attempt to create an ice breaker.

Basically, are we just confused on a higher level or are we making progress. :confused2:
 

JimVT

Bronze Member
GOLD Site Supporter
on the st4 two band the rubber drum in the center it held by clamping the two sprockets together and centered by the tabs on the sprockets
the center rubber is like an ice breaker but isn't very efficient at times. later a ice scraper was put on to keep it clear.
 

jask

Member
I am adding ice scrapers to my early machine ( ST193 - 1961 ) I have seen a few now where the internal drum section was cracked and repaired - obviously from ice building up..
I would also recommend having some work done on the assembly whenever you rebuild these- I have seen a few ( one that might be a low mile original unit ) that have a spot of brazing added on each of the inside face locating tabs where they touch the drum. This extra stiffening supports and protects that drum. and every one I have seen with cracked and repaired drums did not have this- I am speculating that the unsupported flexing of unwelded units, or uneven loading from ice buildup causes more stress ( and cracking ) than they were originally engineered for.
Considering the intended use and very long service life of most of these machines I am really impressed that there are so many still out there, and in as good of condition as they are.
 

Sno-Surfer

Active member
I am also looking for a set of the bronze gears for the two band track. Lyndon pointed out that mine are hard steel and they will eat up my grousers.

If anyone has a set or a lead, let me know. Thank you.
 

redsqwrl

Bronze Member
GOLD Site Supporter
OK, today was the day I went on a goose chase to follow some leads on patterns and casting the sprockets.

What I know patterns:
I can have a pattern on Match board, with Shift locks, created from my used ST-30A sprocket and a supplied, dimensioned drawing. If I want it 4 weeks it will be approx. $1600... If it is prepared as fill in work $1000.
He is willing to prepare the molds and sell the sprockets. on his dime.
He is willing to build a plug Mold, corrected for shrinkage. Labor to cast this way is prohibitive.
Casting:
Union Brass and aluminum foundry, will hand cast four sprockets off of my used sprocket corrected for shrinkage and built up to Approximate OEM dimensions.( his Time and material estimate) at least $500 for molding plus $3.00 per pound for material (which he has in stock) I did not weigh my sprockets but the per lb price seems fair. this price is market driven...

cope and Drag Mold Is still time and material, but the hand molding process is non-existant. This is the $1600 mold that would be good for quite a while.

Summary:

I am going to go to another pattern maker tomorrow and price check the pattern maker quoted above.
we have three foundrys that will and can do this work.
we have at least six pattern shops within an hour.

What are your thoughts,...
Who else has an iron in the fire....

I am guessing that 12-16 sprockets would get sold quite fast based on the chatter here.
 

redsqwrl

Bronze Member
GOLD Site Supporter
Went to the second and third pattern maker Friday.. NOt good news.

$2000 for a loose mold. from A.H. patterns.

$3500 for a loose mold. From Prime patterns.

Both cheaper if i Can source a dimensioned drawing. I am going to bump this a few times before I contact the first pattern maker who is willing to do the cope and drag method for $1600

Basically if my math is correct the cost will be the roughly the same as J&T sprockets plus shipping except the sprockets will be full size not 25% shrunk.

Hopfully I can get some feedback sooner than later. as lead time is key to getting this rolling before any one is in a bind for this coming winter.

mIke
 

MNoutdoors RIP

Gone But Not Forgotten
GOLD Site Supporter
Well I've run into a dead end up at the North Pole AK. But another member here was going to check with another foundry in the Northwest but have not heard anything from him in awhile. We certainly could do the drawing if we had a new one. We also could machine one from a blank of material but do not think it would be cost effective because so much of the blank would turn into chips.
 
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