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Vplow 
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Joined: 17 Jun 2013
Location: New Jersey
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 Topic: 3 Cyl Detroit= HD7?
Posted: 17 Jun 2013 at 11:35am |
Hi all,
just had a quick question which I see lots of crawler discussion going on here so I was hoping someone might know.
Did AC produce any crawlers in the 1930s-ca. 1950 timeframe with a 3-cylinder Detroit Diesel other than the HD7? That is the only one I have been able to come up with. And did any early HD7s have any difference in radiator/sheet metal from later production, or did they always look basically the same?
Just trying to pin down what an old, long-gone machine actually was. Thanks!
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DiyDave
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Joined: 11 Sep 2009
Location: Gambrills, MD
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Posted: 17 Jun 2013 at 6:24pm |
 Vplow wrote:
Hi all,
just had a quick question which I see lots of crawler discussion going on here so I was hoping someone might know.
Did AC produce any crawlers in the 1930s-ca. 1950 timeframe with a 3-cylinder Detroit Diesel other than the HD7? That is the only one I have been able to come up with. And did any early HD7s have any difference in radiator/sheet metal from later production, or did they always look basically the same?
Just trying to pin down what an old, long-gone machine actually was. Thanks! |
According to Swinford's book, 3-71's were only in HD 7's crawlers AD, AD3, AD30, and BD3 graders.
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SHAMELESS
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Posted: 18 Jun 2013 at 2:01am |
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i had one in my HD5, maybe it was a transplant??
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DiyDave
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Posted: 18 Jun 2013 at 4:59am |
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Should have been a 2-71, in a HD5. That's the thing about 50+year old equipment, someone has been there before!
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Ages Cat
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Joined: 12 Sep 2009
Location: Hutchinson, MN
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Posted: 18 Jun 2013 at 11:51am |
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I have an HD5B that was converted to a 3-71 by Sweeny Brothers Tractor Co , in North Dakota. I understand there were 125 done and I have seen two and two others advertised. The heavy gumbo soil in the Red River Valley demanded a lot of power out of the early tractors. The crawlers, both Caterpillar and AC, were very popular as they did not compact the soil. The HD-7 had a factory installed 3-71.
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Coke-in-MN
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Joined: 12 Sep 2009
Location: Afton MN
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Posted: 18 Jun 2013 at 12:10pm |
Early HD7 with the 3-71 was a completely different machine than later HD7 units . Unlike the HD6 which use much of the same tooling as the HD5 machines . Difference on the 2 or 3 -71 is about 20/25 HP per cylinder. Other crawler tractors made by AC also used the 71 series engine through the lineup , but as GM got into crawler business with Euclid / Terex AC sourced their own engines by buying Buda engines.
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Faith isn't a jump in the dark. It is a walk in the light. Faith is not guessing; it is knowing something.
"Challenges are what make life interesting; overcoming them is what makes life meaningful."
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Vplow
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Location: New Jersey
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Posted: 18 Jun 2013 at 3:54pm |
Thanks to all for your repsonses! Sounds like it was an HD-7, as this was in NY state so I would doubt those conversions were anything but an exceptionally odd rarity out here!
Coke, when you say the early HD7 was a completely different machine, can you elaborate at all? Mechanically, appearance wise, or all of the above? I haven't found reference to anything but the 3-71 DD in the HD7 so was there some other engine used earlier or later, or did the engine stay the same but other things got changed? Other than maybe the radiator grill, all the HD7s I've seen firsthand or in pics all look about the same- there may be mechincial differences but the radiator/sheet metal/etc. are all the same basic design. I never saw the machine I'm asking about, only heard about it so just trying to know what model it was and what it actually would have looked like. It was a town snowplow machine with v plow and double wings, the "oldtimers" said it was about late '30s machine but also specifically said it had the 3 cyl detroit in it so I would say it's probably been pinned as an HD7, and probably just from the early 40s (based on what I've seen soemwhere that the HD7 was introduced in 1940).
But what changed between early and later HD7s?
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Dozer
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Posted: 18 Jun 2013 at 7:08pm |
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The HD7's 1941 - 1950 were dozers. The later HD7G's are track loaders. The HD5G track loader has a detroit 2-71 The HD6G is similar to the HD5G but the motor is an HD344 or a 6000 in the newer machines. The HD7G 1961 - 1969 uses the 7000 turbo motor. The HD7GB 1969 -1974 uses the 516 cubic inch 6 cylinder version of the turbo 344 motors.
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Coke-in-MN
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Posted: 18 Jun 2013 at 7:20pm |
AC seems to have left a hole in production after the HD7 when they came out with the HD5 in 1947-48 so the line was dropped in say the 70 HP machines going to a 4-71 in next size . The next HD7 series had no resemblance to the early machines . Early HD7 had some look of the HD5 with radiator area being wider in front and tapering back to operator station. First video is like most machines i have seen and the same type of dozer blade lift system [TUBE]http://youtu.be/G4M2FNVMKXs[/TUBE]
This is a modified blade system on this HD7 , and a operator who is going to be buying a clutch real soon . Unskilled operator just waiting to self destruct machine around him as he plays.
[TUBE]http://youtu.be/KKYZFpFxcds[/TUBE]
Edited by Coke-in-MN - 18 Jun 2013 at 7:23pm
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Faith isn't a jump in the dark. It is a walk in the light. Faith is not guessing; it is knowing something.
"Challenges are what make life interesting; overcoming them is what makes life meaningful."
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Vplow
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Location: New Jersey
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Posted: 18 Jun 2013 at 8:08pm |
Thanks guys. So for the "orginal" Hd7 tractor/dozer, the machine was pretty much always the same then thoughout production (1940-50 or so) and looked like the ones I'm familiar with (which is also to say, like the ones in the video clips posted by Coke), and the reference to the difference between early and later was only refering to the later ca 1960s-70s HD7G trackloader vs the earlier "orginal" Hd7.... have I got that right?
For sure the machine I'm talking about was the old orginal ca. 1940s HD7 - that machine was probably already out of service by the time the Hd7G trackloader came into existence! Or at most got fired up one or two last times for big blizzards. By the 60s the big 4wd trucks (plus more frequent plowing instead of the old days of waiting for the snow to stop and then going out to break everything open!) had pretty much made the crawler plows obsolete.
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AusHD6
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Posted: 19 Jun 2013 at 3:42am |
Hey Dozer
HD7GB 69 thru 74 ran the 426 ci 6 cyl' 3500 series motor, HD12GB got the 516 ci turbo 11000 series motor. Think the HD7G's also got slightly wider track guage and HD11 track chains.
Cheers
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