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Bulldozers are tracked-type tractors designed to push soil and heavy objects. In a typical specification sheet, the following are listed:

  • Flywheel power (hp or kW)
  • Gross power (hp or kW)
  • Engine displacement (=volume)
  • Torque (I could not find this datum in this specs sheet, if you know the torque of a CAT D9, please write it - N meters)
  • Drawbar pull (how much weight the bulldozer can tow)

For reference, here is a specs sheet of the latest CAT D9 bulldozer: https://www.cat.com/en_ZA/products/new/equipment/dozers/large-dozers/104260.html

And in PDF: https://s7d2.scene7.com/is/content/Caterpillar/CM20200807-cbc8d-74cd9

Drawbar pull specs

What is the most representative of the bulldozer's "strength" and performance? If there isn't a single specs, what is the meaning of these specs (not definition) for practical use?

Putting this in another form: suppose I have a semi-trailer truck with 500-600 hp, can it tow more weight than the CAT D9? If not, what spec determines that (I guess the drawbar pull)?

Or in another form: suppose I have an unbreakable chain, I tie one end to a D9 (405-452 hp) and the other end to a racing car (750 hp), heavy truck (500-600 hp) and a tank (1500 hp), which spec will tell me who would win this "rope pulling" contest (in each case)?

And if I tie the other end to another bulldozer of a different model, and I have its specs too, can I predict who will win the "rope pulling" contest?

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  • $\begingroup$ Does this answer your question? Flywheel power vs. Gross power in bulldozers $\endgroup$
    – Solar Mike
    Commented Nov 3, 2023 at 14:47
  • $\begingroup$ No. The linked question asked for the difference between flywheel and gross power. I ask a more general question. $\endgroup$ Commented Nov 3, 2023 at 16:50
  • $\begingroup$ Perhaps you could accept a relevant answer - the faqs help… $\endgroup$
    – Solar Mike
    Commented Nov 4, 2023 at 7:14
  • $\begingroup$ What are you defining as "strength"? $\endgroup$
    – Fred
    Commented Nov 4, 2023 at 19:40

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D9 datasheet gives single shank penetration force, which is similar to pushing force. 16-17 tons in this case.

General rule how to compare:

  1. how much a tractor can pull or push is proportional to its weight. 1\3 in case of D9. D9 weighs about 50 tons, while sports cars about 1 ton. Sports cars will push or pull about 50 times smaller weight. You can improve this by loading a vehicle, to some extent - if soil is hard enough to avoid sinking, you could load 10 tons on a tractor and expect it to push or pull 3 tons more.

  2. Need to make sure there is a gear setting for low speed. 3.5 km/h for D9. Sports cars lowest setting is probably around 35 km/h - it would perform about 10 times worse than D9 by this metric.

  3. Need engine powerful enough. If some tractor gives the same low speed transmission, but has more engine power - you could load it more to increase its pushing capability.

some simple math: 0.16 * engine power (kw) / speed at the lowest gear (km/h) = how much you can push or pull (tons)

0.16 can be as high as 0.28 in an ideal world

If weight that you try to push is more than 0.33 of your tractor weight, you probably wont be able to push it

It seems D9 is well optimized for this role

Competition: Tank-racing car-truck-bulldozer. Racing car loses because low weight and too high low gear speed.

Tank-truck-bulldozer. Truck loses because its grip with the ground is worse, even if we fill it up and it has a low speed gear. Wheels traction is about half of the tracks, unless wheels are gigantic. Truck can pull maybe 1/6 of its weight, but tracked vehicle about 1/3.

Tank-bulldozer. About equal in grip, weight, low speed gear. But tank has a larger engine and can load itself up and win this way.

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  • $\begingroup$ The relevant test is the "slot dozing test" It is used to compare the performance of competing units, and would be a typical specification when a coal power plant wants a new dozer. It's more relevant to D11s than D3s, though. $\endgroup$
    – Phil Sweet
    Commented Nov 4, 2023 at 11:06
  • $\begingroup$ @PhilSweet Can you elaborate on the "slot dozing test"? $\endgroup$ Commented Nov 4, 2023 at 20:25
  • $\begingroup$ @Surprised Seagull: In the specs sheet Caterpillar lists around 700 kN (~70 tons) of drawbar pull in lowest speed (0.1 km/h) and about 40 tons in 2 km/h. The D9 weighs 50 tons. What am I missing here? $\endgroup$ Commented Nov 4, 2023 at 20:28
  • $\begingroup$ @Triceratops apps.dtic.mil/sti/tr/pdf/AD0746228.pdf $\endgroup$
    – Phil Sweet
    Commented Nov 4, 2023 at 21:48
  • $\begingroup$ @Triceratops it is possible to pull closer to 100% of own weight at low speed if ground allows to grip well. It is unreliable metric - too much depends on how well can the bulldozer grip to the ground. But nothing stops you from assuming this, formula i gave works with this assumption too, no changes needed. At low enough speed and good enough grip you can push anything $\endgroup$ Commented Nov 5, 2023 at 4:27

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