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cham-ed

Horse power

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cham-ed

:whistle: I have another question for the group. The 702 I used to have, had a 7HP Kohler (K161). My current self propelled walk behind has a 6.75 B&S. My Kohler had A LOT my power than the 2006 B&S. Has the concept of rating horsepower changed over the years? Or am I imagining something?

Cham-Ed

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wse100

wiki horsepower This may help a bit :D

They still measure it the same way.

I think i know what you mean. I have two lawn mowers, both 11 horse briggs. my horizontal (wheelhorse)seems to have more power? They are just about the same age. On another thread they were saying that the kohlers had much more power than briggs of the same H/P rating?

I'm still learning :WRS: :whistle:

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dgjks6

I wonder is it has more to do with the transmission and how the power gets to the wheels?

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wse100

I wonder is it has more to do with the transmission and how the power gets to the wheels?

In my case it just has more power, cutting pulling et cetera. my wheelhorse has a 42" deck 11 h/p, my simplicity has a 36" deck 11 hp. my simplicity bogs down, my horse just keeps chewing?

maybe there is a technical reason?

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BairleaFarm

horsepower origniated for along time ago. Each horse power represents the amount of weight that can be towed in a certain amount of time. I think its 30000 ft pounds per minute. Example. My tractor 8 hp. That equals 240000 ftlbs per minute. So my engine shold be able to tow/pull 240 lbs in 1000 feet in 1 minute. Hope thats not confusing. :whistle:

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dgjks6

It may have to do with torque - but I am having a hrad time understanding the difference between hp and torque

Greg

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BairleaFarm

I told you what hp was. Now torque. Torque is how hard you pull the rope :whistle:

Think of it like this. Dragraceing. Hp is how fast you hit the wall and torque is how far you go through the wall. Ever been to a truck pull?

Dragstrip drivers like Horsepower they dont really care how much they got tow to the end as long as they get there quickest.

Pullers like torque. We dont care how long it take us to get to the end we just wanna get the weight there.

Have i made this clear or just confused you more.

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HorseFixer

It may have to do with torque - but I am having a hrad time understanding the difference between hp and torque

Greg

Maybe this will shed light on the subject, this is for automobiles but can be used for our small engines.

Horsepower and Torque

by Dale Wickell

What You Need to Know About Torque and Horsepower

Nearly every truck and car review you read tells you the vehicle's horsepower and torque ratings -- but they don't usually explain what the terms mean or why they're important to you as a driver. And when you do see an explanation, it's often in tech language that still doesn't make sense on a level that most of us understand. So here goes -- a basic explanation of horsepower and torque, in everyday English. No tech experience required.

Horsepower, abbreviated hp, and torque are two separate measurements that help reveal the capabilities of your truck or car's engine. Don't worry too much about how they are measured or exactly what the abbreviations you see with them mean. Just look at the numbers and the revolutions per minute (rpm).

Remember a few things when you're looking at specifications:

Horsepower is responsible for moving the vehicle along and gives it the ability to cruise on the highway and accelerate in normal conditions.

Torque is the force that helps the vehicle start moving from a stop and pulls it up steep hills.

Torque steps in again to provide power when you're hauling items or towing something behind the vehicle.

Automakers state peak hp and peak torque at specific rpm (the numbers you see on a tachometer).

Hp and torque both drop off before and after their peaks.

Comparing Horsepower and Torque

When you look at specs, think about how you drive. If the majority of your driving is in-town and at 60 to 70 mph on the highway, your vehicle's engine is spending most of its time in the 1800-2500 rpm range. So an engine that produces its peak horsepower or torque at 5500-6000 rpm might not be the best choice (unless it's the only choice for the vehicle you're considering) because that's not your usual rpm range.

Horsepower vs. Torque

Higher torque ratings are more important than high hp ratings if you pull a trailer, haul heavy loads or drive on roads with long, steep grades.

If you like to see how fast you can get from stoplight to stoplight -- or if you do a lot of other quick acceleration driving -- hp is more important.

Keep in mind that hp and torque don't necessarily peak at the same rpm. They can differ by a small to wide range. Reviews don't always include the peak rpm for horsepower ratings, but they're available in factory specifications.

Don't assume that you need the truck that's advertised as having the highest horsepower or torque in its class. If it suits you in other ways, sure, go ahead and buy it. But put some thought into how you use the truck before you decide to spend extra money now -- and pay more for gas later -- on a truck with more power than you need.

Hope this helps! :whistle:

Duke

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Curmudgeon

Everyone has a torque wrench, right? Torque is how hard you twist something, be it a bolt, or how hard the crankshaft will turn something.

Horsepower is torque times speed. Same torque, but the crank turning faster, more horsepower. More torque, but the crank turning the same speed, still more horsepower.

Now let's talk powerband. As the speed is dropping, so is the horsepower, but if the torque does too, horsepower will really drop. Some engines have wide powerbands, think diesel trucks. Some very narrow, think chain saw.

When you're mowing, it's torque that keeps the crank turning.

When more power is required, the engine has to slow down to pull the governor open. The governor senses the speed of the engine, and opens the throttle accordingly.

To continue, you're in heavy grass, the engine slows, the governor opens, torque increases, the speed holds at the slower speed.

Comparing engines of the same peak torque or peak horsepower is fine, that's wide open at a specific speed.

In the real world, you're seldom wide open, just reach up and push the governor when in heavy grass if you don't believe me, the engine will speed up unless you're really bogging it down. You're not mowing at peak horsepower.

So now you have a combination of just wide is the powerband, how far off the peak speed are you, and how far did the governor open the throttle to try to compensate for that speed loss?

How was the engine rated? That new engine could very well make 25hp at 4000RPM, but it's governed to 3600, and dropping from that before the governor responds.

Lot of variances, and in a world where horsepower numbers sell, not how well the engine actually performs, well, the new engines numbers just don't measure up to the old.

Figures don't lie, it's 25 peak HP, but liars do figure.

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linen beige

Figures don't lie, it's 25 peak HP, but liars do figure.

I LIKE that! :whistle:

As my uncle used to say, "The older ones had bigger horses." In other words, the new ones may claim to have more horsepower, and they may just have. But although ten little horses may pull x number of pounds x number of feet, they likely can't pull any further than that. The heavier masses found in the older engines provide more inertia that translates into more torque, that translates into pulling further.

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refracman

You guys have splained it perrty good, but i like mine more better

Horsepower = how looud it bees

Torque = how goods it be doin a smokey burn out!

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Curmudgeon

But although ten little horses may pull x number of pounds x number of feet, they likely can't pull any further than that. The heavier masses found in the older engines provide more inertia that translates into more torque, that translates into pulling further.

Inertia doesn't make torque. Rotational mass stores energy, (inertia) but it doesn't keep you going when the going gets tough. If you think it does, try turning the engine off, the rotational mass is still there, but it doesn't long. It is constantly being restored with every firing of the engine.

All the inertia does is keep you going until the engine fires again, and even with a single cylinder engine lugged way down, that's not very long.

With each firing, some energy is stored in the rotational mass, the rest goes into the driveline. Well, except for all that energy wasted out the exhaust pipe and cooling fins that is.

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linen beige

Inertia doesn't make torque. Rotational mass stores energy, (inertia) but it doesn't keep you going when the going gets tough. If you think it does, try turning the engine off, the rotational mass is still there, but it doesn't long. It is constantly being restored with every firing of the engine.

All the inertia does is keep you going until the engine fires again, and even with a single cylinder engine lugged way down, that's not very long.

With each firing, some energy is stored in the rotational mass, the rest goes into the driveline. Well, except for all that energy wasted out the exhaust pipe and cooling fins that is.

I guess I didn't phrase that quiet right. The more mass you have rotating, the more inertia you have. The more inertia you have the more work can be done by it and that translates into more USABLE power. If, for instance, an engine has a given amount of energy available through the inertia of a large rotating flywheel, and another engine rated at the same horsepower has only half that much inertia available to it, then the one with the larger flywheel will be less apt to bog down under a load that would slow or stop the other engine. That translates into more usable power.

Think of it like this. One horse, with a pre-tightened rope from a stand still, can pull so much weight so far before becoming exhausted. That same horse given a "running start" can much more easily move the same load that same distance and still have energy to spare. That is due to the increased inertia of the already moving horse.

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jerrell

:whistle: here is another twist to things, all new engines are being measured in cc's so the B&S's 305cc produces 14.5 ft lbs of gross torque, What happened to hp, we went to the metric system and confused the dickens out of me , i still like the lb, gallon, and sae measurements, why do they have to complicate a good thing, i don't want to look at some converison chart to find a 17 hp engine. what's next,, s

just sonding off, :WRS:

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linen beige

:whistle: here is another twist to things, all new engines are being measured in cc's so the B&S's 305cc produces 14.5 ft lbs of gross torque, What happened to hp, we went to the metric system and confused the dickens out of me , i still like the lb, gallon, and sae measurements, why do they have to complicate a good thing, i don't want to look at some converison chart to find a 17 hp engine. what's next,, s

just sonding off, :WRS:

I think maybe the industry is trying to come up with a standard. There are more ways to measure horsepower than you can stuff into a bushel basket (What's the metric equivalent to bushel?).

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Curmudgeon

Looks like I'm gonna make another enemy here.....

Energy stored in a flywheel is just that, energy stored. You're only going to keep going IF you're making enough power to do so. You can have a one ton flywheel, and if the job performed is taking more energy than you're making, you're gonna just keep slowing down.

Even the heaviest of normal sized flywheels on a garden tractor will only buy a couple seconds at best. At 3000 RPM you've already went through 50 firing cycles (100 if you have a twin) in those two seconds. If you've lost some speed with every one of them because you were using inertia to keep going, you aren't going to keep going for long.

A flash in pants load can be overcome with inertia, but a sustained load, such as keeping the grass or snow flying requires plain horsepower and torque. The only purpose of the flywheel is to store energy to get you back past the compression cycle, and to even out the pulses from when it does fire. That's why generally speaking, singles have the heaviest flywheels, and they get progressively lighter as you add cylinders.

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linen beige

Looks like I'm gonna make another enemy here.....

Another enemy? Nah! We're trying to say the same thing! A larger flywheel will get you past a small, how you say, "Flash in the pants" load without perceptibly adverse effects to the engines forward momentum when that same load may very well stop a smaller flywheel. And that is one reason a lot of folks think that the older engines had more power than the newer ones rated the same.

No enemies here, just another poster that sometimes can't find the right words.

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