Why don't compact tractors make more power??

[mx125]

There is probably an aspect of tractors engine requirements that I don't understand, so thought I'd ask. Why is it that a CUT (like my JD2320) makes 20 ish hp and torque and larger CUTs make 30-37ish . . . yet a simple car or motorcycle engine (which can't cost more that $3-4K) produces approx 100hp. Torque may be between 40-85ft/lb's depending on capacity.

CUT motors are likely more basic but can't cost much less. I know rev'ing to 12-15,000 RPM is not practical, but is there something else I'm not understanding?

 

[Tig]

For tractors it's all about torque, not RPMs and HP.

 

[Wombat125]

A tractor motor is designed to be run at WOT under load all day, every day.

Put a plow on your honda civic and run her up to 8000 rpm where she makes that 100 hp and see how long the motor lasts.

 

[Jimbrown]

My BX makes 23 hp. Thats more than it really needs. If you hook it to an imovable object it will spin all 4 wheels, if you put the loader down and try to push 20 tons of dirt it will spin all 4 wheels. If you lower the loader it will lift the front wheels off the ground, if you aren't carful with the back hoe it will drag the thing all over the place. It could not use more power if it had it.

 

[mx125]

A tractor motor is designed to be run at WOT under load all day, every day.

Put a plow on your honda civic and run her up to 8000 rpm where she makes that 100 hp and see how long the motor lasts.

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I see what you mean there. That does make sense. And the point re: available power matching the weight/capacity of the frame makes sense as well. I do think that within a weight class/size, there should be no reason why a tractor should be straining given the technology per dollar available. Ie. My 2320 is great, but could safely benefit from a 30HP/30ft/lb motor . . and that should be a no brainer at the cost. But a lot of that is marketing and model separation.

Thanks for the points. . .that makes sense.

 

[wkpoor]

As another said, Tractor engines are rated at full continuous power. HP in car engines is no different than HP in tractor engines other than cars make power over a much broader band. Any givin size of tractor has the powerplant necessary to do the job of its intention. By moving slow and using gearing for torque multiplication they or more efficient with less peak power.

 

[Wombat125]

My 2320 is great, but could safely benefit from a 30HP/30ft/lb motor . . and that should be a no brainer at the cost.

Perhaps. With relatively high torque and lots of tractive force, a tractor's gearbox and final drive have to be built with engineering limits proportional to the motor.

So if you bump your 2320 up to 30HP, you'll possibly need a bigger, stronger, heavier tranny and diff. You then probably need bigger tires to put that extra power to the ground. Now you have a 3320.

I suppose they could build a tractor powerplant and driveline out of the latest super strong lightweight alloys, but I don't see much market for a $75000, 200 hp, 1500 lb tractor.

I did hear about one fellow who used his 1000cc boxer motor from his BMW motorcycle to build a snowblower. An 80hp walk-behind snowblower is not a machine to be trifled with.

 

[mx125]

Perhaps. With relatively high torque and lots of tractive force, a tractor's gearbox and final drive have to be built with engineering limits proportional to the motor.

So if you bump your 2320 up to 30HP, you'll possibly need a bigger, stronger, heavier tranny and diff. You then probably need bigger tires to put that extra power to the ground. Now you have a 3320.

I suppose they could build a tractor powerplant and driveline out of the latest super strong lightweight alloys, but I don't see much market for a $75000, 200 hp, 1500 lb tractor.

I did hear about one fellow who used his 1000cc boxer motor from his BMW motorcycle to build a snowblower. An 80hp walk-behind snowblower is not a machine to be trifled with.

That's true! . .I would NOT want to blow snow with that thing.
But an other great point I didn't think of. (The tranny etc. has to be build to match). That also explains a lot. An 80HP tractor would need all the mechanicals to support the uses at that power level . . then you've got the power of a car with a chassis and mech 3 times as tough as a car . .hence a much higher price tag. Thanks guys.

 

[DreaminGreen]

I am not sure but maybe, the tractor in this video would make enough power for mx125. A high hp JD lawn tractor. YouTube - NDSCS V8 John Deere Lawn Tractor

 

[tallyho8]

I am not sure but maybe, the tractor in this video would make enough power for mx125. A high hp JD lawn tractor. YouTube - NDSCS V8 John Deere Lawn Tractor

Now that's one that would really needs a ROPS.