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.

 

[Charlesaf3]

Of all the things I've wanted for my tractor, more horsepower isn't one of them. Horsepower is oversold as a metric of getting things done. Arguably, my b3030 doesn't even need the HP it has, much less more. And more HP would burn more gas to do the same work...

Don't get me wrong, I want and am getting a bigger tractor. But its for traction, loader lift etc - hp isn't the issue, aside from minor pto considerations.

I know most of the people here know this, but it would have been good for me to read as a newbie so I'll post it.

 

[Wombat125]

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

I'm thinking a cage, a parachute, and in my case, an extra pair of shorts.

mx125 -- We all know you're there thinking, "Hey now, There's something I could work with."

I'm just kidding, of course. This has been a good thread because it made me think through some things too.

 

[RWolf]

You could have all the horsepower and torque in the world but if you can't get it to the ground and do useful work then it's wasted. I've got a SCUT that's 14hp with two 3 speed trannys inline. IF I could keep it from spinning wheels it could pull a house down (just a slight exaggeration) but the premise is it could do a lot more if it was about 500lbs heavier. It also has a FEL but because of it's weight limitation it's only rated at lifting 500lbs. I can do a bit more because I've weighted the tires etc.

 

[N80]

Most car hp ratings are also at RPM's that most cars rarely or never see. You'd be surprised how little you use of a cars marketed HP rating.

 

[mx125]

Thanks again . . That is actually exactly the kind of info I needed. Kind of clears up that particular line of thinking for me and all makes sense. I don't feel short on horsepower with my JD CUT (except in high grass with my rotary cutter or slight incline in high gear). More that the size of tractor reaches it's limits . . as you said. I might need to jump up to 30ish HP to deal with grading and plowing my new road, or maybe I just need to hire someone with a proper grader twice a year . . . . but that's a whole other thread!!

 

[Wombat125]

You'd be surprised how little you use of a cars marketed HP rating.

I drive a 1988.5 Suzuki Samurai. I can fairly assure you that I use all of it.

 

[Charlesaf3]

I drive a 1988.5 Suzuki Samurai. I can fairly assure you that I use all of it.

LOL! Aren't those measured in gerbil power?

 

[greggh]

LOL! Aren't those measured in gerbil power?

But in that case it is the size of the cage...

 

[John_Mc]

I drive a 1988.5 Suzuki Samurai. I can fairly assure you that I use all of it.

Maybe when accelerating, but you'd be surprised how little you are using just cruising at highway speeds.

John Mc

 

[Wombat125]

I'm guessing you haven't driven a Samurai.

From the factory a Samurai weighs 2200 lbs. It comes equiped with a 66 squirrelpower, 76 ft-lb, 1.3L, 8v, carbureted motor. The 1986-87 models couldn't pull 5th gear, so they lowered the ratio in the 88 models.

When you get on the on-ramp, you run her up to about 6000 rpm in each gear except 5th. Once in 5th gear, you simply stand on the throttle. All the time. No matter what. Your forward velocity will be somewhere between 55 and 60 miles per hour. Hit a little hill or a head wind and you're back into 4th. Or 3rd....

Having said that, I have repowered my Sami with a multi-port FI, 16v, 1.6L big-block out of a 1994 Geo Tracker. Now I will never win a drag race, but at least I can go 70 and keep up with traffic. And I don't have the throttle pinned. At least not all the time.

I wouldn't trade her for a brand new Cadillac.