Bob Semple detail question

[tom!]

Hi.




I always wondered how they managed to get 8 men inside this thing. Are there any drawings or pictures regarding the crew positions and the interiour?

Yours

tom!

[phylo_roadking]

Well....first of all - remember the side sponsons over the tracks are empty space



http://www.cracked.com/article_19233_th ... built.html

The tank was made by placing an armored box on top of a tractor -- and by "armored" we mean "made from roofing material." Supposedly, the corrugated surface would deflect bullets by virtue of its curviness. Since they also lacked artillery in any numbers, they outfitted the Bob Semple with as many machine guns as it could hold. Six to be exact.

Unfortunately, that last part meant having to cram at least six people into that piece of junk. One of the machine gunners had to lie on a mattress in the belly of the tank, right on top of the burning hot engine. The other five had to stand on the first one's back, presumably. And then they needed someone else to drive the damn thing. According to Wikipedia, the total crew consisted of eight people.

But then again....look at this pic, not a common one of the Bob Semple - and see how physically big it was compared to a man???



As an idea - was it really THAT bad in extremis??? The Soviets did something similar IIRC...



...and actually used them in combat! And the British used armoured bulldozers...

[phylo_roadking]

Have you seen this?

[phylo_roadking]

Here's the newspaper article that first introduced the NZ population to the Bob Semple....I can't help emphasising some "interesting" features!

MADE IN NEW ZEALAND

CONVERTED TRACTORS

P.W.D. ACHIEVEMENT

(By Telegraph—Press Association.) CHRISTCHURCH, This Day,

When New Zealand's own tanks show their paces before the public for the first time, in a few weeks, there will be presented the fulfilment of a dramatic chapter in the history of the Public Works Department.

The genesis of these 25-ton tanks was a photograph taken in the United States and given to Mr. Semple. That photograph showed a converted caterpillar tractor, and so impressed was Mr. Semple that when Belgium and France fell last year he became convinced something "hot" for any potential invader of New Zealand could be prepared on the lines of that valuable photograph. He showed the photograph to Mr. T. G. Beck, now district Public Works engineer in Christchurch, but at that time engineer in charge of the huge irrigation schemes in South and Mid-Canterbury, with his headquarters at Temuka. Mr. Beck was faced with the tough question of whether he could convert some of the big P.W.D. tractors into tanks without any blueprints, as it would take valuable time to secure prints from America. A prompt "yes" was Mr. Beck's reply, and expert workmen at the Public Works workshops at Temuka were organised by him for the job.

ARMOUR DEVISED

First a "tank" was made of three-ply to get the pattern, and the. next problem was to secure steel that would withstand anti-tank rifle fire. As the result of investigations and experiments Mr. Beck devised armour which passed severe firing tests, and it was then decided to go ahead and build the first tank. The whole of that important task was carried out at Temuka and completed. The tank was tested before Army representatives to their satisfaction. With the decision to construct further tanks, operations were shifted to larger workshops.

In addition, big trailers were made to transport the tanks at high speed to places where they might be needed. These trailers were designed by the Public Works Department in Wellington, and the first was built under Mr. Beck's supervision at Temuka. These New Zealand-made tanks look grimly efficient, and their performances bear out their looks.

POWERFUL MACHINES

The armoured bodies are placed on the big 98 horse-power caterpillar tractors, which were brought into New Zealand by Mr. Semple to do heavy Public Works construction jobs. These tractors are the most powerful in the world, and as tanks they have immense power. Not only can they climb a grade of 1 in. 2, but they will travel through water over four feet deep, traverse an embankment four and a half feet high, smash through gorse hedges, scrub, and saplings up to six inches in diameter, and move across country where roads do not exist. Their armament- consists of a number of quick-firing guns. Each tank has a crew of eight, and normally carries 25,000 rounds of ammunition. In addition there is room for the carriage of troops and ammunition in safety over country that might be under enemy fire. Furthermore, each tank is fitted with a drawbar with which an armoured trailer can be towed.'

These tanks, which, incidentally, are officially known as "mobile pill-boxes," burn crude oil, and accordingly cannot be vulnerable to incendiary bombs. The only thing that could put them out of action would be a big gun. The tanks are not fast, but they can be taken wherever they are wanted on trailers as fast as any tank ever built. Not only can they go virtually anywhere, but they can operate for 60 hours without refuelling.

TRACTORS PROVED A GODSEND,

"If this country is going to be invaded, we need to have equipment as good as that of the other fellow, if not better," said Mr. Semple. "We could not buy tanks from outside, but had to act on our own resources. Luckily we had big tractors here, and they were a godsend. They have proved one of the greatest boons the country has ever known, permitting us to build highways, aerodromes, camps, and fortifications in record time in the Dominion. They have proved invaluable for other urgent purposes outside New Zealand."

Mr. Semple added that it would not be necessary to withdrawn tractors from service to have them converted into tanks. Tlie tank bodies could be mass-produced and bolted on to the tractors when required.

Looks like it could do everything but fly!

There is however a display on the Bob Semple at the museum at Waiouru - do we have any NZ members on the Forum could see if they know more about crew locations???

[phylo_roadking]

There's one very interesting line buried away in that article....

Mr. Beck was faced with the tough question of whether he could convert some of the big P.W.D. tractors into tanks without any blueprints, as it would take valuable time to secure prints from America.

According to David Fletcher, they were referring to....this??? Spot the similarities!



The Disston tank! Designed in 1933 and first shown to the U.S. Army in 1937, the Disston used a standard Caterpillar model 35 chassis with an armored structure attached. Rejected by the Army, the Marine Corps ordered 16 and it was sold commercially as the Disston "Six Ton Tractor Tank" to "nations with greatly reduced appropriations" according to their sales brochures.

And they had customers! The Afghans bought nine, and three spare bodies - with the provision that they had a turret with a 37mm gun added, and they were shipped by train from karachi in India to Kabul. In 1938, the Chinese ordered four, with them being delivered a year later.

Many years later - the Americans came across one in Afghanistan!

[Kingfish]

Have you seen this?

If only the Kiwis had a few on Crete...

[phylo_roadking]

Well, THAT would have meant that the Allies had more Caterpillars there....and thus Maleme wouldn't be as bumpy - and thus fewer Ju52s would crack up on landing! And the flightline cleared faster. Careful what you wish for...

At least it would definitely have been able to fire over Cretan stone walls!

[phylo_roadking]

As it manouvers around the sandpit in that video, I can't help thinking of....






(You know.....the more I watch the video above of the Bob Semple, I can't help noticing that it isn't really THAT slow - it's around the same as a Matilda! - or unmanouverable...given the weight bias in the lower half of the machine due to the positioning of the original tractor! And all those MGs would have made quite a mess of a Japanese infantry company...in an era when the Japanese were notoriously short of infantry A-T weapons, bar maybe satchel charges or bags of grenades...! And I would hestitate to say it - but surely the base Caterpillar tractor would be a hell of a lot more reliable than a Matilda that needed preventative maintenance every ten miles according to its manual???)

[tom!]

Hi.



Yeah, I recognized the size. But the side MGs couldn´t be operated by a standing man. The fighting compartment is still not high enough to allow the man on the rear to stand behind the side MG. That´s why I search for an interiour view.

Yours

tom!

[Kingfish]

Hi.



Yeah, I recognized the size. But the side MGs couldn´t be operated by a standing man. The fighting compartment is still not high enough to allow the man on the rear to stand behind the side MG. That´s why I search for an interiour view.

Yours

tom!

Standing orders were for the Bob Semple to be crewed exclusively by Oompah Loompahs.

[phylo_roadking]

Well...one of the things that IS known is that the guy manning the central MG lay on a mattress on top of the engine cowling!

Interestingly - if you look again at the video, right at the end - that open section over the port-side trackrun seems to contain a driver....or perhaps an observer shouting instructions TO the driver! He doesn't have an MG...

That's two taken care of. Now there are two side MGs, and the turret MG, and one MG on the rear - that's another four gunners to account for. Which makes six...

So where are the other two??? Or rather - what are they supposed to be doing?

I assume at this point one is the driver, buried away in the centre of the vehicle where the controls normally are...

But I can't see the need for an eighth crewman - unless there was one to manually traverse the turret?

EDIT: looking again at the pics....the starboard-side MG facing forward? That gunner seems to have a little cupola - so HE for one may have been able to stand up in the sponson and fire the gun I.E mounted in a ball mount at his waist level, as if firing "from the hip"

[Kingfish]

Well...one of the things that IS known is that the guy manning the central MG lay on a mattress on top of the engine cowling!

Interestingly - if you look again at the video, right at the end - that open section over the port-side trackrun seems to contain a driver....or perhaps an observer shouting instructions TO the driver! He doesn't have an MG...

That's two taken care of. Now there are two side MGs, and the turret MG, and one MG on the rear - that's another four gunners to account for. Which makes six...

So where are the other two??? Or rather - what are they supposed to be doing?

I assume at this point one is the driver, buried away in the centre of the vehicle where the controls normally are...

But I can't see the need for an eighth crewman - unless there was one to manually traverse the turret?

EDIT: looking again at the pics....the starboard-side MG facing forward? That gunner seems to have a little cupola - so HE for one may have been able to stand up in the sponson and fire the gun I.E mounted in a ball mount at his waist level, as if firing "from the hip"

Two forward firing, two side, one turret and one rear, so a total of 6 gunners.

Crewman #7 is the driver, who I believe is the man you see in the open window port side. The position of the main turret, plus rear gunner, would suggest the driver (and controls) has been relocated to make room.

Crewman #8 (commander) occupies the starboard side cupola behind the starboard side front gunner. The cupola is too far back and low to be fired from a man looking out of the cupola.

[phylo_roadking]

Crewman #7 is the driver, who I believe is the man you see in the open window port side. The position of the main turret, plus rear gunner, would suggest the driver (and controls) has been relocated to make room.

Mr. Semple added that it would not be necessary to withdrawn tractors from service to have them converted into tanks. Tlie tank bodies could be mass-produced and bolted on to the tractors when required

That would be logical, that it really was the driver out there on the port sponson....but I'm not sure it's the case....not if prefabricated hulls could be built and stockpiled and tractors converted in extemis. They're hardly going to sit down and do a huge amount of hydraulic plumbing/wiring/fitting of various rose joints and extension bars etc. with the Japanese rowing their boats ashore...

It's also far too elegant a solution for the Bob Semple There's a lot to be relocated - at least six levers and two foot pedal controls! And several of those work direct into the gearbox...

[Kingfish]

You could be right - however...



Notice how the turret is more of less in line with the location of the controls (hint: look at the controls/turret in relation to the rear return wheel). That would place the turret gunner's feet right atop the controls.

[phylo_roadking]

As in....the driver steers the tank but the turret gunner works the clutch???

Anyway - that's not the case; look here -



...the driver sits on the left of the bench seat, like an American car...



...but the turret is mounted on the centreline. So if the gunner is standing anywhere...he's standing on that bare bit of decking between the control cluster and the rear engine bulkhead.

Look again at the four-line drawing above - I also asume the two side gunners are sitting/kneeling/standing/perching on weither side of that open decking too? Or rather - on whatever bit of steel plate is laid across it as part of the "hull"...