What is Horsepower?

[SawTroll]

Brake horsepower was NOT intended to be used on saws It is an automobile term as far as i know.. and dynos on cars do measure hp. Or at least that is what they are calibrated to measure / display. It is also used on locomotives I think. Although ships use shaft horsepower.

If you look up horsepower there are about 2 dozen meanings or ways to measure it. Some, although technically valid terms, are not used any longer.

Yes, but what the dynos actually measure is kW and torque. I agree with the rest of your post.

 

[drkptt]

Yes, but what the dynos actually measure is kW and torque. I agree with the rest of your post.

Dynos measure speed and torque. Is your insistence that they measure watts just based on the fact that modern measurement standards trace back to SI base units (m, kg, s in this case)? If not, please explain.

 

[SawTroll]

Dynos measure speed and torque. Is your insistence that they measure watts just based on the fact that modern measurement standards trace back to SI base units (m, kg, s in this case)? If not, please explain.

Sorry if I was unclear, but that is just another way to say it, kW is the result of torque and speed (rpm).

My original point was that it doesn't actually measure any kind of hp, that is just maths. What the display shows depends on how it is coded......

 

[056kid]

I do think that some of Brad's vids where he sinks those saws into hardwoods are rather impressive. Sure some were more than others, but it is always nice to see a saw with a decent bar buried to the dawgs.



Mr. HE

Not all his big wood is the same, some of it has lost density making saws look faster. IMO!!

 

[TreeClimber57]

Sorry if I was unclear, but that is just another way to say it, kW is the result of torque and speed (rpm).

My original point was that it doesn't actually measure any kind of hp, that is just maths. What the display shows on how it is coded......

Well.. as a kW is a measure of energy or power.. and is directly able to be converted into other measurements of power.. why would we suggest it is kW and not some other measurement?

1 HP = 33,000 ft·lbf/min (see below on this

or

1 HP = 0.74570 kW = 76.04 kpm/s = 641.2 kcal/h = 2,545 Btu/h = 1.014 hk = 550.3 ft lb/s

So.. why would we not be able to say that the measurement is in Btu/h, ft lb/s, kW or even HP? Just wondering..

The only way one might be able to make an argument for kW is if the dyno was using an electric motor/generator as the source of the engine load. Which many do.. (as the measurement of the generator would be electrical - hence kW) but there are also dyno's that use air, hydraulics or water as an example of load sources.

But.. is 1 HP really a horsepower.. likely a question that has been asked over the years a million times.

Apparently the unit of measurement, coined by James Watt as a way to allow people to understand the power of the steam engines. James was using his engines in mining industry, which used ponies for work. James measured the ponies work ability at 22,000 ft·lbf/min. He then added an additional 50% bringing it up to 33,000 ft·lbf/min.. and used that as an measurement for his engines. Only an estimate or guess.. based upon how much work he thought a horse might be able to do over a mining pony.

 

[SawTroll]

Not all his big wood is the same, some of it has lost density making saws look faster. IMO!!

He has occationally said that the wood was inconsistant. Add that to the other variables not accounted for.

At least he admits that his tests are not perfect, not everyone would do that. :msp_wink:

 

[TreeClimber57]

Several comments have stated that cutting would be better measurement.. well in some ways yes.. as it is more related to what the saw does in real life.

But.. how would anybody ever find a material consistent enough to use as a valid measurement point? It would have to be a synthetic material, designed to simulate wood resistance. Only then could you repeat it hundreds of times, in various locations around the world and have some consistant..

Or would you..

Then others would say the chain, how sharp it was, even the pitch of the chain.. may impact the speed!! So.. you are back to a system where everybody would question if it were a solid reliable, and unbiased approach to measurement. Furthermore, it would be something that we could not relate to other engines.. boat, snowmobile, etc..

So end of day.. we are likely best to stay with what we have

 

[056kid]

He has occationally said that the wood was inconsistant. Add that to the other variables not accounted for.

At least he admits that his tests are not perfect, not everyone would do that. :msp_wink:

indeed

 

[Simonizer]

Well.. as a kW is a measure of energy or power.. and is directly able to be converted into other measurements of power.. why would we suggest it is kW and not some other measurement?

1 HP = 33,000 ft·lbf/min (see below on this

or

1 HP = 0.74570 kW = 76.04 kpm/s = 641.2 kcal/h = 2,545 Btu/h = 1.014 hk = 550.3 ft lb/s

So.. why would we not be able to say that the measurement is in Btu/h, ft lb/s, kW or even HP? Just wondering..

The only way one might be able to make an argument for kW is if the dyno was using an electric motor/generator as the source of the engine load. Which many do.. (as the measurement of the generator would be electrical - hence kW) but there are also dyno's that use air, hydraulics or water as an example of load sources.

But.. is 1 HP really a horsepower.. likely a question that has been asked over the years a million times.

Apparently the unit of measurement, coined by James Watt as a way to allow people to understand the power of the steam engines. James was using his engines in mining industry, which used ponies for work. James measured the ponies work ability at 22,000 ft·lbf/min. He then added an additional 50% bringing it up to 33,000 ft·lbf/min.. and used that as an measurement for his engines. Only an estimate or guess.. based upon how much work he thought a horse might be able to do over a mining pony.

This has been the most accurate post thus far.

 

[drkptt]

This has been the most accurate post thus far.

Except for equating energy with power in the first sentence.

 

[TreeClimber57]

Except for equating energy with power in the first sentence.

Well they are closely related. Going back to my physics.. shoot that was a long time ago..

Power is the rate energy is convered or work is preformed.

In an example of constant power, Energy = Power * Time (if memory is correct)

A unit of energy can be the watt.. which is also equal to one joule per second.

But you can also get into mechanical, electrical or even light formulas for energy and power. Many which I likely never remembered .. or if I did then have forgotten long ago.

 

[drkptt]

A unit of energy can be the watt.. which is also equal to one joule per second.

Watt is a unit of power. Joule is a unit of energy. You are correct that energy = power x time. Apply 1 watt for 1 hour and you get 1 W-hr. Which is 3600 W-s or 3600 J.

 

[Thorcw]

Several comments have stated that cutting would be better measurement.. well in some ways yes.. as it is more related to what the saw does in real life.

But.. how would anybody ever find a material consistent enough to use as a valid measurement point? It would have to be a synthetic material, designed to simulate wood resistance. Only then could you repeat it hundreds of times, in various locations around the world and have some consistant..

Or would you..

Then others would say the chain, how sharp it was, even the pitch of the chain.. may impact the speed!! So.. you are back to a system where everybody would question if it were a solid reliable, and unbiased approach to measurement. Furthermore, it would be something that we could not relate to other engines.. boat, snowmobile, etc..

So end of day.. we are likely best to stay with what we have

I like your thoughts how about delrin wouldnt dull a chain just dont know were to find a big enough block

 

[TreeClimber57]

I like your thoughts how about delrin wouldnt dull a chain just dont know were to find a big enough block

But being devil's advocate.. if it does not dull chain.. would it provide enough resistance to provide adequate test? Or would it be like a warm knife in butter.

 

[Hddnis]

I like saws that cut like a warm knife through butter.:msp_wink:




Mr. HE

 

[RiverRat2]

Well.. as a kW is a measure of energy or power.. and is directly able to be converted into other measurements of power.. why would we suggest it is kW and not some other measurement?

1 HP = 33,000 ft·lbf/min (see below on this

or

1 HP = 0.74570 kW = 76.04 kpm/s = 641.2 kcal/h = 2,545 Btu/h = 1.014 hk = 550.3 ft lb/s

So.. why would we not be able to say that the measurement is in Btu/h, ft lb/s, kW or even HP? Just wondering..

The only way one might be able to make an argument for kW is if the dyno was using an electric motor/generator as the source of the engine load. Which many do.. (as the measurement of the generator would be electrical - hence kW) but there are also dyno's that use air, hydraulics or water as an example of load sources.

But.. is 1 HP really a horsepower.. likely a question that has been asked over the years a million times.

Apparently the unit of measurement, coined by James Watt as a way to allow people to understand the power of the steam engines. James was using his engines in mining industry, which used ponies for work. James measured the ponies work ability at 22,000 ft·lbf/min. He then added an additional 50% bringing it up to 33,000 ft·lbf/min.. and used that as an measurement for his engines. Only an estimate or guess.. based upon how much work he thought a horse might be able to do over a mining pony.

Mr. Watt is Pretty close I'd say,,, on the coining of HP

Mercury has been rating their outboards in HP/Kw for years,,,, @ the Prop 250/189

http://www.mercurymarine.com/engines/outboards/optimax/proxs/?model=7

 

[RiverRat2]

I completely understand wanting true HP numbers, actually it would be awesome. The problem is I've yet to find an affordable and viable option. I know TW has one he made and from what I've read, he's put a lot of money and time into it, and it's still not ready, maybe he'll come along and fill us in. My point, a dyno is out of the financial realm of chainsaws, a builder is working on a $800.00 saw for a few hundred dollars, not expensive cars. The best way to measure gains, like it or not is timed cuts. Timed cuts are far from perfect, but it does gives us something.:msp_smile:

If ya ever make it up to Madsens In Centralia/Chehalis WA there used to be a Saw Dyno setting right inside the door!!!

 

[ckelp]

KW method i think is way better than HP ratings IMHO

 

[TreeClimber57]

Mr. Watt is Pretty close I'd say,,, on the coining of HP

Mercury has been rating their outboards in HP/Kw for years,,,, @ the Prop 250/189

Well, a lot have been using the term.. simply because it was a common and known measurement.. Does not mean it is relative to what a horse can actually do.

Anybody who has ever worked around horses knows a horse can outperform a small gasoline engine.. the question has always been debated on how long they can sustain it.. the other obvious question related to relationship of a horse and say a tractor is related to traction ability, the horse with the same power will almost always win over tires in traction ability. If you have ever seen a team of large draft horses in a pulling contest, they can move impressive loads!

However, looking up the term.. trying to determine if anybody had done any research.. here is what I found.

A horse can apparently produce nearly 15 HP.. on continous basis..!

The horsepower measurement is the amount of work that a horse can produce for a continuous time period at a slow haul.

However in a gallop for short periods the power level for that same horse shoots up dramatically..

A healthy person can peak at about 1 HP . But the continuous power output for a human is about 1/8th HP.

But back to horsepower.. what is the record or aveage?

The unverifiable record is apparently a two horse team of clydsdales, pulling a sled with 52 tons of logs across snow. To me seems a little sketchy ..

But it depends on traction, surface, etc.. as well.. so if the snow was packed .. and the surface smooth enough.. assuming they could get traction you can pull a lot on packed snow once moving.

On other hand a horse can easily pull more than its own weight all day long.. and a draft horse can easily weight over a ton. (that is a long way from 21 tons I will admit .. but this is on any ground, up hill, down hill, etc..)

But.. taking a locomotive.. a friend of mine who is now retired from CN.. says they used to figure around 1HP of locomotove per ton of weight pulled as a minimum. They had charts.. and used to run more than minimum on trains many times apparently - and that went up depending on where in the country you were headed (hills or mountains impact this greatly). (he said the locomotives ran around 4,500HP each)

Given that.. maybe a HP on a train is close to being what a real horse can do (but maybe a little lower than real horse ability) .. my dad, who had a lot more experience around them than I always said a horse could easily do more than a HP of work continously.. it has always interested me to find out.. but can not ever get solid answers..

So.. I give up..

 

[TreeClimber57]

KW method i think is way better than HP ratings IMHO

Why .. just a personal preference

they (kW and HP) are both only established measurement units.. they could be rated in corn kernels for that matter and as long as this was a known, measurable and verifiable unit of measurement.. then it would be as accurate! Point being the unit of measurement is not important.. and is easily converted from one to another..

While you may have a preference for one over the other.. fact remains one is no more accurate than the other.. Now some may debate if a HP is really in any way related to what a horse can actually peform.. regardless as long as we know how much work it is .. can measure it and compare it.. then it is equally as good as any other.

Interestingly enough, as far as I know, most electric motors are measured in HP.. one might think being electric kW would be logical.. they do have watts on the rating as well.. but that is watts consumed not produced. I guess the concern might be the confusion between energy used and produced if both shown in watts.. not sure.

The one item I personally like about HP.. since our electric motors are rated in HP, is it gives a common term in relationship between gasoline engines and electric motors.

All be it the torque and hp curves are very different on the same rated gasoline engine and electric motor