Inside the Chieftain's Hatch: Skeleton Tank.

The Skeleton Tank, AKA the Spider Tank, was a proof-of-concept from the WW1 era to try to combine the light weight of a smaller tank with the off-road and trench crossing capability of a larger tank.
Video filmed at the Training Support Facility, Ft Lee, VA.

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[aluxtaiwan]

There is almost no "inside" for chieftain to hatch.

[tacticalmanatee]

The idea of an armored core reminds me of warship design, specifically the idea of the all-or-nothing armor scheme and the armored citadel. I wonder if some Navy designers had any input in the initial idea.

[ricklotter]

I always appreciate the Chieftain's forthright approach, willingness to admit to mistakes, and in general total lack of ego. Very refreshing, very commendable. Thanks for the video!

[cirian]

Chieftain channelling his inner OddBall "I'm not a mechanical engineer" Translation "Oh, man. I only ride them, I don't know what makes them work."

[timsmith]

This was parked along the railroad tracks at Ft Lee back in 2010, along with a bunch of other tanks and guns. (Ex-wife wanted to see her old AIT barracks and I hijacked this leg of the trip for about an hour photographing everything that was parked there. She was not happy about that.) It was more of a green shade at the time and I had no idea what it was.

[sampointau]

Reversing gears on the output shafts of each engine to supply forward or reverse and steering was purely done by reving up on one engine and reducing speed on the other with foot throttles. Bevelled gears on the track drive shaft to mesh with the prop shafts bevel gear. Simple brake drum on each track drive for parking only.
That all comes from memory of a "Boys Own" book from the 1920-30's that my uncle had. It didn't explain the starting though but once an engine was turned over to compression on number 1 cylinder a simple pull of a meshed lever would work, yes I have started engines dating from pre WW1 to 1940's by crank, even a ford V8 as fitted to the CMP 30cwt "Blitz" truck could be started by a 10 year old that way!

[ditzydoo]

Bravo! I am glad to see this one preserved and under cover. it always made me sad to see it sitting out in the weather hidden just behind the Ordnance Museum building at Aberdeen Maryland during my service station there with the Ordnance School.

[calvingreene]

I have always been impressed with this solution to the low engine power heavy armor problem in tank design. There is a picture and blurb about it in some old World Book encyclopedias that I had access to from as soon as I was allowed to handle books.

[mini_wargamer]

8:20 love how it went from a Skeleton Tank to a "Spider Tank" lol love mistakes that wasn't caught

[battlefieldbartender]

Glad they restored her, She was in bad shape after years outside at APG. Thanks Chieftan!

[randyhavard]

It's great someone decided to save this

[danielverlander]

The three shafts to the box on the back make me think a sort of double differential system where instead of one motor that goes both ways for steering, it has one motor for each direction

[teamidris]

I am an engineer and started as a plant mechanic and it looks like they built it to try out different drive ideas. Like: two shafts with the clutches inside, un-linked engines and clutches at the back with one central shaft. A proper research and development machine :o) . And that’s probably why the big bevel gears are missing? They were away being tinkered with.

[JuxtaposedStars]

I think I can explain the clutching and steering mechanisms but reverse gear selection is harder because some of the parts can't be seen.
@5:00 You can see the the geared shaft in the middle of the clutch/flywheel assembly. This could be called the clutch output shaft or transmission input shaft. This shaft has a "collar"(between the raised bulbous area on the shaft and the gear)to engage one of the steering levers. You can see the "clutch steering selection fork" on the "floor" in the upper right hand side of the video @5:09. Additionally, the actual clutch fork can been seen riding on the same shaft @5:00 (the small arm with the adjusting bolt for tolerance). The clutch fork follower rides onto the bulbous area of the shaft, functioning like a cam, when the Steering selection fork moves the collar forward or backward. The rear gear on the shaft does not move front or back, the area the selection fork engages is probably a hollow tube, sliding axially on the gear shaft.
Depending on whether the clutches are sprung engaged or disengaged, moving each steering lever will independently let the power to each track "slip" anywhere from full engine(both engines)power to 0. I can't be sure but the very large gear in the center, connecting the geared flywheels of each engine, is probably used to transmit power between engine flywheels so all engine power can be sent to either track. It might be used to start one engine off of the other as well.
Forward/Reverse selection probably involves pairs of idler gears either underneath the gears at the back of the fighting compartment or missing components. The forks for the gear selection can be seen to the viewer's immediate left of the "clutch selection fork" @5:09 and are probably controlled by the large locking lever with the two detents in the driver's area(between the driver's legs?) @5:46
The box at the rear, outside of the fighting compartment, is most likely just a ring and pinion final drive(although it's entirely possible brakes were located here as well). I think the only parts definitely missing are just the beveled ring gears to transmit the power 90 degrees and provide any further gear reduction needed. The biggest piece of evidence for this is the fact that both ring gears mesh on the right of their pinion gears. The left side ring gear would be mounted behind its flange, @6:28 you can clearly see the cut outs in the frame for the clearance of the missing beveled ring gear. This is also evidence that both driveshafts and engines are spinning in the same direction(counterclockwise for the driveshafts and clockwise for the engines, all when viewed from the front of the vehicle). There don't appear to be any other mounting surfaces on the axle mounting flanges to locate steering or even brake hardware, but that is limited by what we can see in the video. If the roof clearance is too low in the box, the roof is probably a later addition for cosmetic or conservation purposes.
(edit for spelling & clarity)

[briansmithwins]

Spider tank, spider tank, does whatever it is a spider tank does...

[frankgulla]

Thanks for the quick view of the Spider Tank.

[RSColddawg]

Saw this thing at Aberdeen when I was a kid. Thought it was the weirdest thing I'd ever seen. Hope the M6 that was at Aberdeen back then eventually got some TLC (as it was missing tracks when I last saw it).

[stanislavczebinski]

The Chieftain The clutches are mounted directly to the engine you stood right next to😉 Their bell housings have that big sprocket around it and a small one in the center.

The clutch is actuated, as you suggested by those big levers - if you consider to do so😉

When the clutch is engaged, the propulsion force is transmitted by the small center sprocket to that double sprocket in the back underneath the fuel tank.

I'm still trying to figure out that final drive🤔

Greetings from Germany!!

[z_actual]

It looks like there are flywheel clutches that work opposite to how we use them now, for now we have a pressure plate from driven flywheel to clutch plate to shaft. That is to say on this the outside ring and gear on the back of each engine is the clutched part, and the middle or core is the drive part. So when you clutch the engine, the outside gear which we would relate to a flywheel loses power and stops moving, but the core keeps going. In this way you would control the drive from each side, and be able to turn the vehicle

[WelcomeToDERPLAND]

What a beautiful and unique prototype, very much enjoyed that.