Does anyone know: specific track material?

[ww2steel]

Does anyone know specifics on what tracks were made from in WW2? I am wondering about hardness, are they poured steel or cast iron? If cast iron: Grey with graphite? I don't know much on the topic but want to learn! Thanks,

Mike

[Guest Guest]

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[costard]

ww2steel

The reference I have is mild steel being used by the Brits in WW1 (MkIV and V), the French AMR-33 (Renault VM) using die-forged steel tracks of the Carden Loyd system.

Mild steel doesn't weld well, much better to rivet it - loking at the plates of the tracks will give you a good idea of which is being used.

Cast iron is unlikely - too brittle. Poured steel suffers from being difficult to control in a mould (cast iron expands slightly as it cools, making the process easier). So perhaps a die-forged alloy steel - what alloy I can't tell you.

Cheers

[ww2steel]

Thanks for the info. If a single cast link can hold up to 21 tons, and the entire replica vehicle only will weigh about 40,000 pounds, I should be safe using inexpensive cast iron alloys... I hope!

Thanks,

Mike

[JasonC]

The tracks were steel, sometimes with solid, hard rubber "pads" or "shoes" extending out of them an inch or so to give them better road performance and reduce wear.

They aren't welded incidentally, the sections are joined by inch thick steel "pins" through jointed ends of two successive track sections.

[costard]

JasonC

The photos I have of the WW1 tanks have what look like rivets attaching plates to the drive chain through a vertical axis - I assumed they were such with the info on mild steel, and assumed (there's that word again) the cost of bolting to be prohibitive (tho' allowing pretty good replacement ability).

Were the pinned track sections made in one piece with the chain element a vertical component of the original casting, or was there another linkage - chain section pinned to plate, chain section to chain section, plate to plate?

There ough to be someone's article on track designs around, with engineering drawings etc. Different designs for sure - Carden-Lloyd, Christie, Porsche, Holt.. probably mixed up some suspension designers in there.

Do you have a link to engineering drawings in your library?

Cheers

[JasonC]

First, my familiarity with them doesn't come from the links below or drawings, but from pulling maintenance (or supervising it) on modern tracked SP howitzers. There are a few variants in older designs, but the basic method of linking successive tracks together by pin "dowels" remains the same.

The howitzers I worked on were the single pin design explained below, which I consider both simpler and less given to failure. The downside is that they can be harder to service if they do bend or jam, because the single pin rods are quite hefty, and if they bend in place, can be a bitch to swap out.

Overall tread picture for a Sherman -

http://en.wikipedia.org/wiki/Image:M32-ARV-batey-haosef-2.jpg

some terms -

The whole rectangular block is called the shell. A rubber insert in the shell to give a softer ride on roads, and sometimes a "cleat" design, is called the pad. Some older designs did not use a rubber pad, and the whole shell-and-pad assembly might be called the pad in that case. The Germans had a rubber shortage and preferred metal "cleats" extending upward from the outer face of the shell. The term track, singular, refers to one such shell-and-pad, on the order of 100 of them are linked to form one tread.

The shells are forged steel. Their long axis is perpendicular to the direction of motion. Successive shells are assembled together into a continuous chain, in one of two main methods - single pin or double pin.

The tracks (plural) when linked up, form the tread. Sometimes tracks with a plural are

used as the term for the whole assembly. Sometimes even more loosely, the right track

means the whole assembly on the right or the right tread, and the left track the other.

the tracks refers to the both together.

The ends of the shells are hollow tubes, extending the entire length of the shell (its long axis) on the front edge.

Single pin illustration (from a modern robot parts shop, but same design)

http://www.orientalcommodities.co.uk/pictures/BRCandice/BR510415Desc.htm

Double pins are more common, and mean that each shell has such a hollow tube on both its leading and its trailing edges. the ends of the pin of leading edge of the trailing shell fit into the back hole of a *track link* (which is a metal piece with two holes and a connecting piece, much like the links used in ammo belts, except the hole parts are full circles without a gap).

The ends of the pin threaded dowel-fashion through the trailing edge of the next shell ahead fits into the front hole of the same track link.

Between the track link and the shell itself is a (often, rubber) washer called a "bushing". It generally fails first and is the leading cause of track breakage in the two pin system. When the bushing wears out, the pin will eventually grind through the link (the pin is a much stronger steel).

Double pin design (modern, using vertical bolts only for links at the ends of the shells)

http://www.army-technology.com/contractors/tracks/blair_catton/blair_catton1.html

http://www.army-technology.com/contractors/tracks/blair_catton/blair_catton4.html

The pins themselves, with the usual end-piece "nuts" to hold the long axis in place, illustrated -

http://www.specialty-bar.com/military/military-track-pins.html

I hope this helps.

[ March 22, 2008, 11:13 AM: Message edited by: JasonC ]

[ww2steel]

Very interesting, any idea if the WW2 equipment used bushings? With the exception of German lubricated tracks I thought they were just pins and links. I am wondering if in a lighter (30-40k pound) vehicle, bushings (like stainless or something) will be required to give adequate track life or if graphite alloyed cast iron will be hard enough over like a 40mm pin.

Out of curiosity what SPG did you work with?

I see looking through my books that many WW2 US tanks did use rubber grouser pads. I thought that was post war mostly. (I study almost exclusively east front and the Germans and Russians had rubber supply problems, as you stated.)

My replicas are planned to be of German and Soviet designs... someday.

Anyway, still working on methods of casting that are adequate to my requirements.

Thanks,

Mike

[costard]

great stuff JasonC - thankyou.

ww2steel - bushings likely made of bronze - easy to machine to tolerance and fairly hard wearing. The advantage with using a cast iron link would be the inbuilt lubrication - due to the graphite. You could just forget about the bush. Cast iron also machines readily, so your bearing surfaces are smoother to start with. In my opinion it would be difficult to get it to look like steel - particularly if exposed to the weather.

I'm going to take a gamble on my ignorance here, and suggest that cast iron would fail under tension more readily than a hard steel, and wasn't used for this reason. Also, being brittle, would more likely shatter upon the impact of (relatively light)solid shot.

What scale do you plan to make the replicas?

[JasonC]

I worked on both M109s (the SP 155mm, standard army howitzer) and in my later unit, M110s (SP 203mm, heavy open topped piece on the same chassis).

[ww2steel]

The vehicles are 1:1 scale made of steel. About 90% of the weight will be tracks, drivetrain, and suspension. Therefore, I am hoping that cast would be strong enough given the nice waffle style structures used. I do not know the tensile strength of cast iron alloys, and don't know if it would be sufficient to hold up to full power application and abuse of driving 30mph over moderate terrain with the replica vehicle weight. Maybe I can find some metals engineer to work this up for me.

I think that cast iron is less brittle than hardened steel but more brittle than mild steel.

I have plenty of experience welding mild steel, but welded tracks would look odd, especially for German stuff. (Though honestly I haven't decided on a vehicle yet though I have several top candidates.) They could be hollow in places though and could cut the weight of the vehicle hugely.

I think the best would be a face hardened steel, but I'm betting that would be very expensive... prohibitively I'd bet.

Mike

[costard]

Cast iron would be less brittle than some hard steels, perhaps tool steel (used for cutting metal on lathes, high chrome percentages I think). Most, though, would be tougher. A molybdenum alloy gives a work-hardening property - provided the piece isn't over stressed while young, it will over time gain toughness, the crystal structure within the metal changing (you're right, a metallurgist would be handy). I think its this alloy that face hardens, too. Titanium has this quality on its own, but it is a total bastard to machine and expensive. There might be an old SR-71 shell lying around somewhere, going cheap.

Looking at JasonC's links, the single pin track looks to be easiest to manufacture. The driving wheel acts on the pin, so the weak point would be where the pin passes through the shell - where you'd bush it - and no chance of saving weight there with waffling.

Building a Tiger from scratch - heh, THAT's a hobby!

[ww2steel]

I finally found out what KVs used at least: manganese-chromium steel. (New Vanguard #17, plate D (right in the middle of the book)).

Naturally, I will use whatever track style was used originally, especially on the German designs like the King Tiger the waffling (though waffle pattern is a description of a Soviet track style) is very much structural.

My chassis up for options right now are KV/SU-152, Panther (for which I already have a repro'd turret for a late A model that was intended for a ground bunker) or JagdTiger (despite my better judgment for attempting to move this beast - it would be unique and there's one at nearby Aberdeen I can measure from, plus - no turret mechanisms!).

Yeah, I'm going to have to go back to the local foundries and get them to figure up strength and wear and see if there's a cheaper alternative to M-C Steel that's at least half as strong (tensile) and wear resistant.

Mike

[John Kettler]

ww2steel,

Manganese steel, at least for the British and the Russians, who copied them. Source: Macksey's TANK VS. TANK, also Wiki here.

http://en.wikipedia.org/wiki/Caterpillar_track

Regards,

John Kettler