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mmmmmmBacon12345 t1_ja4ofm9 wrote

They go at pretty slow speeds so the engines are built around high torque and long term reliability

At low speeds, power scales linearly with speed so pulling a plow that takes 1 ton of force at 10 mph requires half as much power as pulling the same plow at 20 mph. If you're only ever going to pull that plow at 10 mph you don't need a huge amount of power, lots of farming equipment doesn't work if you pull it too fast.

Cars and trucks need to get up to highway speeds over a relatively short distance, this is really why we put 100+ horse power in everything these days. You only need about 30 hp to cruise on the highway but doing 30-70 on a short onramp to get up to a safe speed requires quite a lot more power.

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hedoeswhathewants t1_ja577sm wrote

Your last paragraph also explains why cars can go 120+ when speed limits generally max out around 70. They have that power so they can accelerate quickly when they need to. The top speed is just a byproduct.

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KarmaticIrony t1_ja5i1fu wrote

It's also (in fact mostly) because having the engine only use a portion of its maximum potential, so going around sixty when it could do over a hundred, is good for long-term reliability.

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koalasarentferfuckin t1_ja61w95 wrote

I'm just sayin' that it's fuckin' dangerous to have a race car in the fuckin' red. That's all. I could blow.

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akodo1 t1_ja8lfno wrote

Not nearly as dangerous as a farm tractor in the red. If/when it fails, all the chains, cables, equipment it's pulling against is going to go flying

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delebojr t1_ja60tq3 wrote

That and you don't want to be sitting at 8,000 rpm on the highway

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SerenadeNox t1_ja6jjw0 wrote

Wankel enters the chat

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Dysan27 t1_ja6r3y7 wrote

Have you seen the custom 4 rotor Rob Dahm is building? Well built, currently tuning it.

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rtfcandlearntherules t1_ja751db wrote

That's not the whole truth though, a lot of cars also need the speed, e.g. police and emergency vehicles.

The maximum speed limit is also higher than in the US in basically every country.

In Most European countries it's around 80 mph (130 km/h) and then there's Germany of course. For me as a German it is pure hell to go only 130 km/h on a straight road with no obstacles and low traffic. Feels super dangerous because you will get bored and "fall asleep" very fast. I guess that's how Americans manage to produce so many accidents on their highways despite the low speed.

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it_might_be_a_tuba t1_ja79aty wrote

Australia has speed limits of 110km/h on the highways and far fewer deaths per capita than the USA. But we don't drive as many American cars and we're less drunk on the road.

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LeftToaster t1_ja7merq wrote

>and we're less drunk on the road.

You sure about that?

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Osiris_Dervan t1_ja8r30y wrote

They all drive drunk, so while there's more drunks driving the average amount of drunk is less.

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it_might_be_a_tuba t1_ja9bpm5 wrote

Blood alcohol limits are .05 in Aus, .08 in most of the USA.

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rvgoingtohavefun t1_ja9gs2j wrote

You could set it at 0.02 or 0.20 and it's the same don't-give-a-shit group of idiots that are going to drive drunk. Generally you aren't taking a breathalyzer before you get behind the wheel, and 0.05 is still plenty dangerous.

Something like 1/3 are repeat offenders and it's full of motherfuckers driving really fucking drunk, like 0.2 or higher.

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rtfcandlearntherules t1_ja7f9qm wrote

Sleeping in the driver's seat also seems to be spreading around the US lately

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Dont____Panic t1_ja9aso2 wrote

Is that the one video of the Tesla driver? I’m pretty sure that was in Toronto.

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rtfcandlearntherules t1_ja9ply8 wrote

there are like 10 different cases that i can think of out of my head. Most are in the US but not all, i believe one even was in Germany.

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balukabalu t1_ja7wshg wrote

I used to drive at 150 km/h because in my country the tolerance is 23 km/h at 130. But with the increasing fuel prices now I travel at 110 (13L/100km vs 8) and I like it, it has a very chill vibe

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beyondusername t1_ja7gcz1 wrote

Emergency vehicles have the budget to do regular maintenance. Pushing the engines harder is less of an issue when you get regular check ups and maintenance to ensure reliable operation.

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gobblox38 t1_ja8rlup wrote

The requirements for getting a license in the US are a joke. It's much more strict in Germany. One of the reasons why there are so many traffic collisions in the US is because there are so many terrible drivers on the road. Add to this that there isn't an alternative way of getting around in most of the US. This even includes sidewalks in some places. If there were interconnected and well funded mass transit systems in the US and walkable infrastructure, the driving standards could be higher.

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Snoo-76025 t1_ja75k5r wrote

speed limits generally max out around 70 screaming in German

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AliMcGraw t1_ja6f7jd wrote

It is also, incidentally, pretty bad for the soil to drive fast on top of it -- going faster than 5 mph increases "washboarding" (or "corrugation"). Tires (and the weight of the vehicles on top of them) are TERRIBLE for soil, and a huuuuuuuge amount of research is put into ensuring that tractor tires compact the soil as little as possible. And even with those beautiful soil-protecting tires, if you're going faster than 5 mph, you're damaging the soil no matter what. Even if your tractor COULD go fast, you don't WANT it to.

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rtfcandlearntherules t1_ja757v5 wrote

How is washboarding a concern on a field that's being plowed?

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tanandblack t1_ja7l5xa wrote

You drive on it after plowing...

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rtfcandlearntherules t1_ja7nke0 wrote

I mean the plow is behind the tractor ..?

Sure you might drive on it afterwards but from my experience a field is not a dry granular road surface like a gravel road. There's also way less traffic, the fields gets plowed frequently and sees almost no traffic. It also turns wet from rain and water and "moves" naturally.Completly different from a gravel road. On top of that the wiki article even recommends "plowing" the road to remove washboarding.

I am not saying that you are wrong because I am geniuenly interested to learn about this, i never thought about it before. But the arguments presented still have me sceptical. That being said the general idea you presented makes perfect sense, of course you'd want to "squish" the ground as little as possible with the tractor. I can understand that without any science.

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gobblox38 t1_ja8v15o wrote

I've come across quite a few farmers that do no plow.

That's not to say the majority of your post is wrong though, just adding a little bit of extra information.

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Naive_Composer2808 t1_ja98ov9 wrote

It more about soil compaction and disruption beyond what is really necessary to plant fertilize cultivate and harvest, any more than that and you are harming the productivity of the plants and soil.

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freefrogs t1_ja9ib55 wrote

A few things to consider here. One is that not every field is a nice soft soil like you might think of in your garden - there are clays and sands and different compositions, some of which are susceptible and others aren't. Another is that not every farm still does plowing, and especially not deep plowing, and even that won't totally break up compaction especially farms that have to plow when it's still wet.

Also, even on farms that do plow, there are still a lot of operations that happen after plowing. There can still be tillage and fertilizing and top-dressing etc etc etc that happen after initial soil prep.

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jaa101 t1_ja5plcr wrote

If pulling a plow requires 1 ton of force at 10 mph then the same plow in the same ground is going to need around 4 tons of force at 20 mph. This means that doubling the speed requires eight times the power.

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purplepatch t1_ja73mnu wrote

Surely you mean doubling the speed requires four times the power, not eight.

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jaa101 t1_ja7845f wrote

If the speed doubles and the force required quadruples, then the power goes up by a factor of eight. This is because power is proportional to force times speed.

The above is true for air resistance and water resistance, where drag is proportional to speed squared. I found a publication linked in this thread that says the same is true of plowing, but another commenter found a paper with experimental results showing the force required increasing much more slowly with speed. If so, plowing is not like fluid resistance and the power required increases even less than the square of the speed.

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InsidiousTechnique t1_ja66r9u wrote

Can you source this? I doubt it's true

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CollegeAnarchy t1_ja6a1ay wrote

Here is a link to an explanation:

https://www.quora.com/Why-is-air-resistance-roughly-proportional-to-the-cube-of-speed

I understand that link is for air, but the concept Is true for any “fluid”. For all purposes of farm equipment, the soil is a fluid because it flows around the implement.

Actually, a lot of solids can be modeled as fluids when in small pieces. Fluidizing flour, sugar, and sand is how it handled on an industrial scale.

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InsidiousTechnique t1_ja6b1qj wrote

I understand the concept, I doubt it applies to dirt in the same way. There's probably some affect there, but surely not in the same cubic relation.

As an example, you can plow dirt and if you were to go over the same dirt right after and it would take much less force at a constant speed.

It's more about the mechanical bonding and friction than fluid losses in this instance. I'm calling in to question your assertion that dirt acts similarly as a fluid in this specific instance.

How much force does it take to pull a plow through dirt at zero speed? Meaning, if you put a plow in to the dirt, does it take greater than zero force to move it?

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MortalTwit t1_ja6iwq0 wrote

Force = mass times acceleration squared. If you double your speed, you need x4 the force.

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jaa101 t1_ja6fja6 wrote

Note that air resistance is only proportional to the square of the speed, so the heading of the linked article is incorrect. Resistance is a force. It's power that goes with the cube, because it's proportional to force multiplied by speed.

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Travianer t1_ja6pfq0 wrote

The whole truck isn't moving through the medium of dirt though so it's apples to oranges in this case.

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kyrsjo t1_ja6vq2w wrote

That doesn't really matter tough. The force would be the sum of two terms that both goes like v^2, the plow drag and the body air resistance drag. So the total drag force still goes like v^2, and the power (force x velocity) like v^3.

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jaa101 t1_ja6ej8o wrote

As plowing speed increases, draft also goes up, but usually varies as the square of ground speed. In practical terms this means that by doubling the ground speed, say from two to four miles per hour, the draft increases four times.

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InsidiousTechnique t1_ja6gtqn wrote

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.thescipub.com/pdf/ajabssp.2010.247.255.pdf&ved=2ahUKEwjLocOc8rT9AhWXlIkEHfzuBN4QFnoECBUQAQ&usg=AOvVaw3A1t4DfoJgCQDmG8Etdlju

So I read the paper, and saw it did assert that. But here's another paper (that looks more researched) that has draft force compared to speed, and there's definitely not a squared relation there although it does show an increase on draft force compared to speed it appears more linear.

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jaa101 t1_ja6iqeq wrote

Looks like you're right, in fact it shows closer to a power of 0.33 than 1, and far from 2. Neither document goes into the physics involved.

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SpaceAngel2001 t1_ja8o60m wrote

As an illustration of how power and speed relate. My neighbor buried a truck and trailer down to the axles in a mud bog. His truck was 300+ hp. My 70 hp tractor easily pulled them out but at a speed of about 2mph. Another example we've seen lately is Ukrainian 200 - 300 hp tractors towing 800 hp Russian tanks.

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DerCatzefragger t1_ja6re81 wrote

Torque is the difference between 500hp sending a 1.5 ton Mustang from 0-60 in 3 seconds, vs a 40,000 lb Freightliner doing the same in 2 and a half minutes. It's slow. . . but it does move.

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mdchaney t1_ja876q8 wrote

To add to this - the old Volkswagen 4 cylinder engines put out around 55HP. Your normal modern car is 200HP and up. That engine was in the Beetle as well as the microbus. Neither vehicle was a barn burner, but could eventually get up to 60MPH. But after you got to that speed it would be fine. I used to also drive a 1980 Ford Mustang with a 6 cylinder engine that put out around 90HP. The post-muscle-car era had some pretty anemic engines, but we got around.

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Dont____Panic t1_ja9ajwk wrote

Frankly, if people didn’t enjoy driving quick cars, more people would drive cars with 50 hp. That’s all you really need to go on the freeway.

I mean, I can’t talk, my car goes 0 to 60 in under four seconds, but practically, there isn’t a great mood for this.

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