KaareKanin t1_ja4tb9o wrote
Reply to comment by Dr_Sigmund_Fried in ELI5: Why does farming equipment require such low horsepower compared to your average car? by thetravelingsong
I don't quite agree, and I would say the premise for the question is false. Cars don't require much power, unless you're going very fast or hauling something heavy up a hill (fast). Farming equipment don't need the same kind of speed. A tractor probably actually needs more power than a car to do what it needs to do
platypuswill t1_ja4ydsc wrote
u/Dr_Sigmund_Fried is correct and you sort of are too. Cars don't NEED all the horsepower they have, they do need some to get up ramps (think freeway) and such but they could go with a lot less. As far as the original question Dr.SigmundFried is right about the torque to horsepower ratio in farm equipment. and u/mmmmmmBacon12345 nails it with their response and u/PckMan explains the difference in what those two measurements of force actually are. hope you learned something new today, please check for yourself though it's good practice. Learning something new is always a cool thing to do.
Daelan3 t1_ja5mc9j wrote
The formula hp = torque x rpm applies both at the engine crank and at the wheels. This means the faster the wheels are turning (the faster you're going) the less torque they will have at a given power level.
If the engine is putting 100hp to the wheels, at low speeds that's enough torque to spin them. At highway speeds, the wheel torque is so low that you can barely accelerate. It doesn't matter whether the engine is achieving 100hp with low torque and high rpm or vice versa.
A tractor has a high torque low hp engine because such engines have good fuel economy and reliability, and the large size and heavy weight are not a problem for a tractor. It's not that a tractor needs more torque. A 100hp car engine can get double the torque as a 50hp tractor engine through gearing.
You can put an F1 engine in a fully loaded semi truck, lower the final drive ratio, and it will move it no problem. It just won't good fuel economy or reliability.
KaareKanin t1_ja6v2a5 wrote
The only thing is, I'm fully aware of this. With his answer Fried validated the initial question, and I still maintain that for normal people using cars normally, they don't require much power at all. They may use it in short bursts because it's there, but I've had rentals with only double digit horsepower figures, and I was never a hindrance to normal flow of traffic.
A tractor probably comes close to using what their engines can output frequently, and if they were to do ploughing a lot faster, power requirements would go up. It's almost all about speed.
platypuswill t1_ja6xxfr wrote
Yes and speed translation comes down to the difference between the original answer of what's more important for each piece of equipment,. Horsepower or torque? For farm equipment it's torque, for cars horsepower. If it's heavy and you need torque for moving heavy loads slowly but with power. taking a hatchback up a hill and onto the freeway horsepower, there have been some awesome answers so far in the responses that nailed it. This was a great question to ask and I hope a lot of others got their answers as well!
[deleted] t1_ja5b1yq wrote
[removed]
platypuswill t1_ja5cemq wrote
Thank you I hope you have a great day
IveGotDMunchies t1_ja50pon wrote
Torque vs horsepower is what you need to google
KaareKanin t1_ja6u1a0 wrote
I don't really need to. Horsepower is the measure of work that can be done. An engine with more horsepower will be able to do more work, hence most car engines could easily do the work a tractor does. And with regards to torque, that's just a question of gearing.
Speed up stuff = do more work.
IveGotDMunchies t1_ja6zt9r wrote
Legend has it that every time you reply, an angel loses a brain cell.
quadmasta t1_ja5cww8 wrote
Horsepower is the product of torque and rotational speed divided by 5252. If you're not spinning quickly, and diesels can't, you gotta have way more torque to produce higher horsepower.
Ever see a dyno graph for a combustion engine?
KaareKanin t1_ja6ucmc wrote
But on the flip side, gear down a normal car engine to output the same rpm, and the torque would be higher (with the premise that a car engine has more power).
Cars don't require much power, only the drivers do. Power is king, torque is just a matter of gearing
quadmasta t1_ja7h7mc wrote
No it wouldn't. Gasoline vehicle engines are designed for higher RPMs and don't make peak power until higher up in their operating range. Tractor engines are designed for low RPM operation and have their peak power waaaaay down in the RPM range.
KaareKanin t1_ja7krne wrote
A given power figure on a shaft rotating at given speed will give the same torque. This is how it works. You can't really argue with this. So I say again, gear both drivetrains to the same output speed, and the one with more power has more torque
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