Bulldozer Question

[Paul Ramsden]

I know its not really a CMP question but you blokes seem pretty knowledgable about these things.
In have been reading accounts of the British using D4 and D7 Bulldozers. What do these designations actually mean? I presume it is weight or something. Picture comparisons or dimensions would be useful.
The reason I ask is I read an account of the British parachuting D4s into the Borneo Jungle and as a model maker thought it might make an interesting diorama. However in 1/35 scale I can only find the resicst D7. Would it be feasable to parachute a D7 or are they way too big?
I also found a Clarke Airborne Bulldozer, how does this relate in terms of D rating?
Thanks
Paul

[gordon]

Well size-wise the Clarks would be about D 0.01 I'd say.

It's just a size theing. The most common was the D2, and as the number got bigger so did the machine. You wouldn't want to pass off a D6 as a D4, no sir.


Gordon

[cletrac (RIP)]

The early Caterpillers were rated by weight like the "2 Ton Cat". The next ones were the 15 Cat, 20 Cat, etc but they were a bit heavier than the numbers might imply. When they came up with the "D" series they were way heavier.
The USAF tried dropping a D7 out of a Hercules in Vancouver in the 1960s and as the chutes opened they ripped off one by one but the Cat did make it to the ground, albiet in not too good of shape. They've perfected the technique since then!

[servicepub (RIP)]

Originally posted by cletrac
...and as the chutes opened they ripped off one by one but the Cat did make it to the ground ...

Was there a concern that the Cat wouldn't make it to the ground?

[gordon]

Of one they 'chute dropped at the south pole and the chutes failed...

It made rather a large, deep hole, and wasn't in too good condition.

[Geoff Winnington-Ball (RIP)]

Originally posted by servicepub
Was there a concern that the Cat wouldn't make it to the ground?

Oh lordy, I think I just pithed m'self...

[cletrac (RIP)]

When I watched it come out the back of the Herc there was no doubt in my mind that the Cat would make it to the ground! It made quite a thump when it hit and there wasn't much left that was any good!

The D number system is used by Caterpillar to denote the different crawler dozers they make. The wartime D4 weighed about 5 tons, the modern D4 tips the scales at about 9 tons. D7 wartime was about 12 tons, modern D7 is more than twice as heavy at 26 tons. I doubt that D7s could be air dropped. D4 was 62 in. wide, 122 in. long. D7, 98 in. wide, 162 in. long. Lengths are to end of drawbar.

Perry

[Rob Beale]

the RNZAF were tasked to drop a dozer (don't remember what size) on to Pitcairn Island. They had a dropzone about the size of rugby field.
Mission was accomplished successfully, but there is a whole lot of empty Pacific Ocean round that wee island.

Rob

[Kym Loechel]

Just as a point of interest the "D" in Caterpillar stands for Diesel or so I'm told.... The 1931 "Diesel 60" motor built by Cat became the staple heavy machine engine used in the USA at least.
The number designated size as already mentioned..
The 1942 RD-1820 radial diesel engine was used to power the M-4 tank with the "RD" prefix standing for Radial Diesel..

[Alex Blair (RIP)]

Originally posted by Kym Loechel
Just as a point of interest the "D" in Caterpillar stands for Diesel or so I'm told.... The 1931 "Diesel 60" motor built by Cat became the staple heavy machine engine used in the USA at least.
The number designated size as already mentioned..
The 1942 RD-1820 radial diesel engine was used to power the M-4 tank with the "RD" prefix standing for Radial Diesel..

Yes The M4A6 was radial diesel powered,but only less than a 100 of them were made late in the war.

[Snowtractor]

The civy Herc we were using had a usable load of 20,000kg well below 26tons for sure. Can the military ones carry more as they may not have the same weight restrictions or was the D7 dropped out of something bigger?
Sean

[Noel Burgess]

Getting back to pauls question about parachuting into Borneo - I would not have thought that was achievable in the 1940s. In 1944 there was only limited success parachuting Jeeps.

As to sizes & weights this from the Trux web site

The following types were the standard types in British service.
Caterpillar D4 35 horse power weight 10,240lb (4.65 metric tons)
Caterpillar D6 55 horse power weight 16,650lb (7.55 metric tons)
Caterpillar D7 80 horse power weight 23,910lb (10.84 metric tons)
Caterpillar D8 120 horse power weight 34,170lb (15.50 metric tons)
All were used by the Royal Engineers with he D7 being the most common. Other types in use were
International TD9; International TD14

Above weights relate to the Tractor only with no allowance for Dozer blade, Winch Etc.

I know that a few Clark Airbourne dozers were used by the british in Europe but were landed by glider Think the same was true in Borneo

Noel

[Grant Bowker]

Looking at the two posts above, it appears that a WW2 vintage D7 (tractor only) could have been transported and possibly dropped from a Hercules. Most construction machinery gets heavier over time for the same model name as part of the competition to say "my toy is better than yours". Current production D7 weighs between 56 and 60 thousand pounds (operating) or 46 to 50 for shipping. Horsepower is now quoted as 240. Quite a change from the earlier versions.

[cletrac (RIP)]

Between the 60 and the D6 there was the RD6 so it could have been around 6 tons. The designation numbers likely originated based on the actual weights but as stated above the weights got heavier over time.
All I know about the Herc's payload is they could lift a D7. The newer versions could likely heft a little more.
Here's a pic of a wartime D7 and a Clark airborne dozer in approximately the same scale. This is a lot like comparing pigs and chickens!

[Paul Ramsden]

Thanks for all the imput.
The picture is from the Royal Engineers Museum in the UK. It shows a static display of a D4 Bulldozer on a medium stressed platform dropped by parachute into Borneo from a Beverley Transporter so it must be 1950s or 60s.
My question was could they deliver a D7 via the same route?

[Snowtractor]

The C119 Boxcar can lift 20,000lbs I believe . So it could have handled the D4 no sweat. Did the Brits use this aircraft also?
Sean

[sapper740]

Originally posted by cletrac

The USAF tried dropping a D7 out of a Hercules in Vancouver in the 1960s and as the chutes opened they ripped off one by one but the Cat did make it to the ground, albiet in not too good of shape. They've perfected the technique since then!

Back in the '70s the CAF used to demonstrate both JATO take-offs and LAPES drops from a C-130 at the Abbotsford International Airshow. The load dropped was a small bulldozer sans blade, but it was always VERY impressive to see. They stopped doing this about the same time as I heard through the grapevine that the JATO bottles were over stressing the airframes and that an aircraft was lost during an operational LAPES somewhere. I've included a pic of a LAPES:

[Wayne McGee]

Indeed there was an aircraft lost with all aboard while conducting LAPES at CFB Namao, late 70's early 80's? due to the load hanging up after the chutes had deployed however, I beleive that the system is still practiced today.
Needless to say, that even from the ground LAPESing is a sphincter tightener.

Cheers

[Mike Timoshyk]

http://ca.youtube.com/watch?v=pRhFRGzh0s0

Hopefully this works....an oldie but a goodie



Mike

[Richard Farrant]

Originally Posted by Mike Timoshyk

http://ca.youtube.com/watch?v=pRhFRGzh0s0

Hopefully this works....an oldie but a goodie

What look like a rough terrain fork lift dropped from the Herc on a low pass, must have broke the land speed record for that type of vehicle.......

[sapper740]

Originally Posted by Paul Ramsden

I know its not really a CMP question but you blokes seem pretty knowledgable about these things.
In have been reading accounts of the British using D4 and D7 Bulldozers. What do these designations actually mean? I presume it is weight or something. Picture comparisons or dimensions would be useful.
The reason I ask is I read an account of the British parachuting D4s into the Borneo Jungle and as a model maker thought it might make an interesting diorama. However in 1/35 scale I can only find the resicst D7. Would it be feasable to parachute a D7 or are they way too big?
I also found a Clarke Airborne Bulldozer, how does this relate in terms of D rating?
Thanks
Paul

It definitely wasn't feasible to para drop a D7 or even a D4 in WWII, at least out of a transport. The reason why? No aircraft existed during that time with a rear ramp that could be opened in flight. The C82 had a rear ramp, but the clamshell fairing couldn't be opened in flight. It would have been suicide to push a D4 out the door of a C46 or C47 in flight as the shift in C. of G. would cause a crash long before the dozer could have been manhandled out. I'll include a pic showing the effort taken to load a D4 into a C47...now try that while the aircraft is flying! I guess a dozer could have been slung beneath the bomb bay of a large bomber...I don't think it would fit inside, at least not completely. It would create terrible drag and probably adversely effect the handling of the bomber. I never heard of such a thing and doubt it ever happened. Derek.


(P.S.) Hmmm, it's not allowing me to upload a picture of several grunts manhandling a D4 into a Skytrain. Oh well, these days I'm happy to simply be able to post a reply!

[Keith Webb]

Originally Posted by sapper740

(P.S.) Hmmm, it's not allowing me to upload a picture of several grunts manhandling a D4 into a Skytrain. Oh well, these days I'm happy to simply be able to post a reply!

Here goes...

[sapper740]

Originally Posted by Keith Webb

Here goes...

Thanks Kieth, much appreciated! Y'know, after taking a good look at the dozer being loaded into the C47 in this pic, it's too small to be a D4, I wonder if it's a CA-1?

[George McKenzie]

Hi First I will say that the older cats pre 1936 numbers stood for horse power .A 30 cat had 30 HP a 60 had 60HP .The 35 was the first deisel .The R series were R being a gas ,RD is a deisel The RD 2,4,6,8 and some U series were the Catipiller modles used in the ww2 .I put a D7 in a Hurculies aircraft in Yellowknife where it was hauled to the artic we had to remove all the dozer parts ,blade and C frame maily because it was too wide ,not too heavy .I might add that these cats did not have canopies on them and when working in the bush kild alot of operaters from the tree tops comming down on them .Some were sheeted in with iron and used in combat They were so reliable that they made a great impact on the out come of the war George

[Lang]

Keith,

I agree with Sapper that it is a little baby Clarke air portable tractor.

[sapper740]

Originally Posted by Paul Ramsden

I know its not really a CMP question but you blokes seem pretty knowledgable about these things.
In have been reading accounts of the British using D4 and D7 Bulldozers. What do these designations actually mean? I presume it is weight or something. Picture comparisons or dimensions would be useful.
The reason I ask is I read an account of the British parachuting D4s into the Borneo Jungle and as a model maker thought it might make an interesting diorama. However in 1/35 scale I can only find the resicst D7. Would it be feasable to parachute a D7 or are they way too big?
I also found a Clarke Airborne Bulldozer, how does this relate in terms of D rating?
Thanks
Paul

Paul, as this thread is about bulldozers, perhaps we should move this thread over to the Engineer Forum? Derek.

[Lang]

Derek,

I will ask Bev about them as she keeps a daily diary of our travels but the chance of getting "Sighted Clarkair bulldozer" in her usual couple of paragraphs over "Sighted two squirrels and beautiful wildflowers" does not make me wildly optimistic about a result.

One, I am pretty sure was on I-90 going west from Minneapolis about mid-morning - it was actually sitting in a little landscaped garden at the entrance to the company yard.

The second one was in the Black Hills area of South Dakota on a pole in a small town, but which one???

Sorry to be so little help but I have to curb my hunting instincts when overseas.

Lang

[sapper740]

Originally Posted by Lang

Derek,

I will ask Bev about them as she keeps a daily diary of our travels but the chance of getting "Sighted Clarkair bulldozer" in her usual couple of paragraphs over "Sighted two squirrels and beautiful wildflowers" does not make me wildly optimistic about a result.

One, I am pretty sure was on I-90 going west from Minneapolis about mid-morning - it was actually sitting in a little landscaped garden at the entrance to the company yard.

The second one was in the Black Hills area of South Dakota on a pole in a small town, but which one???

Sorry to be so little help but I have to curb my hunting instincts when overseas.

Lang

Thanks Lang, I've been mulling over purchasing a CA-1 since I started doing an airborne impression. Along with my R.C.E. impression, an air-transportable dozer kinda fits. Although probably not historically correct, it would look good towed behind my CMP. Derek.

[Noel Burgess]

Identification
I know which were the main types of dozer/tractor used by the British forces in NW Europe - How would I identify the type from a picture? - that is how would I distinguish a Cat D4 from a Cat D7 from an International ?
And what other types were used by other Nations?