Results 1 to 8 of 8

Thread: A Newbie Track Question on D2

  1. #1
    Join Date
    Sep 2007
    Location
    NW Ohio
    Posts
    49

    Default A Newbie Track Question on D2

    Recently Garlic Pete explained to me the differences in the large vs small idlers and the long and short track frames. My question is whether the small idler always came with the short frame, or could the small idler be ordered with the long track frames? Pete explained that the longer five roller setups resulted in harder turns, more track wear and so on but delivered a more stable work platform. I imagine ag crawlers, which is the focus of my upcoming story for the April 2018 issue of Diesel World (out in February) most often came with smaller idler and short track frames... but you guys can tell me.

    That leads me to another question: Obviously on level ground, the large idler tractor is going to put more track on the ground and I wonder how much this might have added to drawbar power? Would have reduced ground pressure a little as well.

    All the pics I have seen so far of D2s in ag use are all small idler, 4-roller crawlers. In fact, while I have seen pics of larger roller D2 with dozer blade, I haven't yet see a five roller D2 image. No that I have seen all that may D2 pics so far.

    Anyway, I appreciate you guys getting me up to speed on Caterpillar stuff with, now and in the past.

    PS- Just now saw a five roller D2... it was a Traxcavator. Otherwise the only five rollers smallish Cats I see are D4s.
    Last edited by Jim Allen; 11-10-2017 at 04:12 PM.
    Jim Allen
    Keeping the Good 'Ol Days of Four Wheeling Alive

  2. #2
    Join Date
    Nov 2006
    Location
    Faunsdale, AL USA
    Posts
    3,213

    Default

    More track on the ground would have little to do with increasing drawbar Hp in most ag applications since there is plenty of traction if the conditions are fit for most operations. The old CATs were more of a pull hard and slow machine with limited horsepower vs later ag tractors including the CAT special application AG machines that were higher HP but really were designed to use that to pull implements faster.

    The special AG tractors on belts had a variable horsepower setup that limited fuel delivery in the low gears to protect the drivetrain. Another example is some of the hotrod steel track tractors where a D69U with a 75-ish Hp D318 turning 1400 rpm would get a 6V71 DETROIT diesel of about 210 Hp turning 2100 rpm. The safest solution was to block out the two lowest gears!
    D2-5J's, D6-9U's, D318 and D333 power units, 12E-99E grader, 922B & 944A wheel loaders, D330C generator set, DW20 water tanker and a bunch of Jersey cows to take care of in my spare time

  3. #3
    Join Date
    Sep 2007
    Location
    NW Ohio
    Posts
    49

    Default

    So... was my question too dumb?

    I look in the material I had available show five roller setups only on the Traxcavator and combined only with a large idler. There were some D2 dozers that might have had five but the wheels were obscured by the blade arms and/or the angle of the shot. So, unless someone presents evidence to the contrary, I will refer to the five roller setups as "rare" and not mention whether they came only with one type of idler or the other. I am using the story to inject some very basic crawler track "anatomy" material, since most reader probably don't know much (and I am only a step or two ahead of them ( : < ).
    Jim Allen
    Keeping the Good 'Ol Days of Four Wheeling Alive

  4. #4
    Join Date
    Jan 2007
    Location
    long island NY, Hancock Ma
    Posts
    1,793

    Default

    also keep in mind that sometime in 1953 cat lengthened the track frame of the D2 to allow the lengthening of the clutch compartment to accommodate the removal of the main clutch without pulling the engine
    Cat 941B, Cat D2 4U, Cat D3B, Cat D4 7U, Cat D6 9U

  5. #5
    Join Date
    Sep 2009
    Location
    Asotin, Wa
    Posts
    1,206

    Default 4 vs 5 roller.

    I can only speak for D4 tractors because thatís all we had to farm with back in the day. We had a 4G and a 7U both 5 roller. 7U had a large front idler, 4G was small. Here, traction was never the reason for going to 5 rollers. It was the ride, operator comfort if you will. Spend 10 hours a day riding a bucking teetering 4 roller tractor and youíre in heaven with a 5. Yes it makes that much difference.


    As far as harder turning and increased track wear, I donít know. Our big idler 7U was one of the nicest driving farm Cats Iíve driven. Brake effort for turning on the headrows was very minimal. Like you only used your big toe to push the brake. Our 7U had 14,000 hrs on it when it left here, Dad put rails on it in Ď78 because he needed to spend some money. Iíve got the old rails up on the hill and theyíre in good shape. Good enough Iíd run them in a heartbeat if I needed to.

    My .02 and itís worth what you paid for it.

    Good luck with your project

    Bruce P.
    Two Ton, Diesel 40, No.11 AutoPatrol , 4G D4, 9U D6, 44A D6B, 17R D6C, 9G D7, 7M D7

  6. #6
    Join Date
    Sep 2007
    Location
    NW Ohio
    Posts
    49

    Default

    Thanks for that "aha!" moment!

    I had noted some disparity in track lengths from the J-Series and early U-Series and '53 and later U-Series and had been researching the reason why. I only had one booklet for early U-Series (1951) and it showed 30 shoes and the same ground contact area as the J-Series. The 1953 materials talk about the "New" D2 and highlight the increase in length, clutch serviceability, increased standard fuel capacity, slight power increase etc. and the tracks have two more shoes and have a fair bit more ground contract.
    Jim Allen
    Keeping the Good 'Ol Days of Four Wheeling Alive

  7. #7
    Join Date
    Jan 2007
    Location
    Kerrick, Minnesota
    Posts
    1,017

    Default

    Yes when they made the design upgrade to the D2's in '53 they lengthened the chassis the same amount as the track link pitch (6-1/8" if I remember correctly) so as to only have to add 2 extra links to the tracks to accommodate the change, basically envision it like they split the tracks on the top and bottom in the middle of the machine and inserted an extra link in each spot, then reconnected them. Although that also meant the track frames were a bit longer as well, these machines still came standard with only 4 lower rollers, just spaced further apart.

    On the topic of whether they only used the larger diameter front idlers on the special 5 roller track frames, both my 5J and 5U parts books indicate that the 5 roller units only came with the larger idlers. In fact, the idlers pictured in both books appear to have heavier-duty bearing blocks on either side of the idler where they attach to the track frames on the 5 roller setups, much more stout than the 4 roller units regardless of idler diameter on those. Also pictured for the 5 roller units are non-oscillating hard bars to extend between the track frames to support the chassis instead of the standard main spring arrangement. Long story short, the 5 roller setups were purpose built to stand up to heavier work loads.
    D2 5J2115SP
    D2 5U7066
    RD6 2H1768
    RD6 2H3072
    No.9 Auto Patrol 8A331
    No.9 Auto Patrol 8A539
    Ten PT3037
    Twenty PL134 (Yard-Art)
    Minneapolis-Moline prototype crawler X253
    1945 Farmall H

  8. #8
    Join Date
    Sep 2007
    Location
    NW Ohio
    Posts
    49

    Default

    Quote Originally Posted by Sasquatch View Post
    Yes when they made the design upgrade to the D2's in '53 they lengthened the chassis the same amount as the track link pitch (6-1/8" if I remember correctly) so as to only have to add 2 extra links to the tracks to accommodate the change, basically envision it like they split the tracks on the top and bottom in the middle of the machine and inserted an extra link in each spot, then reconnected them. Although that also meant the track frames were a bit longer as well, these machines still came standard with only 4 lower rollers, just spaced further apart.

    On the topic of whether they only used the larger diameter front idlers on the special 5 roller track frames, both my 5J and 5U parts books indicate that the 5 roller units only came with the larger idlers. In fact, the idlers pictured in both books appear to have heavier-duty bearing blocks on either side of the idler where they attach to the track frames on the 5 roller setups, much more stout than the 4 roller units regardless of idler diameter on those. Also pictured for the 5 roller units are non-oscillating hard bars to extend between the track frames to support the chassis instead of the standard main spring arrangement. Long story short, the 5 roller setups were purpose built to stand up to heavier work loads.
    Thanks for that and it makes perfect sense.
    Jim Allen
    Keeping the Good 'Ol Days of Four Wheeling Alive

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •