RE: 1 horsepower, really the power of a horse?  
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RE: 1 horsepower, really the power of a horse? - 9/6/2007 3:00:55 AM   
Kweasel


 

Posts: 1087
Joined: 1/7/2004
From: fort worth, TX, USA
Status: offline 		Where did all of the engineers go? This hobby used to be 90% engineers, now it seems to be closer to 10%.

(in reply to Cambo)
       Post #: 51

RE: 1 horsepower, really the power of a horse? - 9/6/2007 4:17:59 AM   
Cambo



Posts: 1516
Joined: 6/20/2005
From: Phoenix, AZ, USA
Status: offline
quote:

ORIGINAL: jaka

Hi!
One horse power is one horse power! Whether is is developed by a horse or a glow engine doesn't matter.
Yes a our modern glow .40 two or four stroke engines are as powerful as a horse...can do the same work in the same amount of time...if geared right!
A .40 engine can lift roots and stumps of trees the same way as horse provided you geared it right.

Last sunday i visited a old museum factory in Eskilstuna here in Sweden where they had old steam engines. One of those huge engines only developed 12 horse power , it was 5m long...but did it at low rews. Lots of torque but not that "powerful".
a modern, 116cc MVVS two stroke engine is a "strong" as this gigant but develops its power at 8000rpm.


You are telling me that my st 40 can pull me at 40 mph if geared correctly. Sorry but i don't think so. Could you imagen if you came up with a some harness for the horse that was attached to a belt (like heli) and when pulled over a certian distance (until rope runs out) spins a 10-6 prop. I bet that thing would be turning 60,000 rpm as you could gear it insanley HIGH, LOL. Powered by a real horse it would be insane. Ofcourse, i don't think a horse would fit to well into my tower trainer 40

(in reply to Kweasel)
       Post #: 52

RE: 1 horsepower, really the power of a horse? - 9/6/2007 8:55:41 AM   
DarZeelon



Posts: 7079
Joined: 4/9/2003
From: Rosh-Ha'Ayin, ISRAEL
Status: offline
quote:

ORIGINAL: Cambo

You are telling me that my ST .40 can pull me at 40 mph if geared correctly. Sorry but I don't think so...



Cameron,


You can believe what you want, so I will not take it personally.

I have shown you calculations, in post #40 and #42 that prove a 1 HP engine CAN do the work a horse does per time unit.


But, even a horse can put out much more than 1 HP, when going 'full bore'... Read this horse web site.

When sprinting, a horse would be giving out much more output than while it is 'cruising' all day around the mine-lift, or mill, which is what the definition of HP is based upon.

_____________________________

Dar Zeelon - ISRAEL - ddzeelon@gmail.com
MVVS - Jett - Nelson - Bolly - Mejzlik

(in reply to DarZeelon)
       Post #: 53

RE: 1 horsepower, really the power of a horse? - 9/6/2007 11:50:38 AM   
speedster 1919



Posts: 1467
Joined: 12/17/2004
From: Martinsville, IN, USA
Status: offline
quote:

For clarification, please answer the following in a concise, factual manner:

1) Did your bike do 135 or did it not?
2) If it accelerated to 135, what gear did it do 135 in? (hint: it won't be first gear)
3) If it was doing 135, what changed to make it slow down from 135 to 88 while still at full throttle?

Ok this is my last post Yamaha made this special 350 from 1973-1976 .RD stands for race derived but more like Road Death. I owned it for 3 yrs and it scared me. Sold it when my best friend got killed on his. HP was about 30-35. It sucked gas-It sucked plugs-It smoked like a freight train with oil injection. I had dealer put a special set of pipes and rejet carb. It would pull a wheelee in first 4 gears. I broke my left foot in 13 places and my passenger dislocated his shoulder when I went to pass a slow truck and dropped down a gear . I cracked the throttle open and we went over backwards in a fraction of a second. This bike was so light-just over 300 lbs range.
(1) 135 for a fraction of a second
(2)6th gear
(3) I keep the RPM's over red line starting with 1st gear and vary little load and speed shifted thru all the gears keeping RPM's way up. Once I hit the artifical high the simple fact that the engine did not have enough HP or lugging torque to keep RPM's up and speed. I only did this a few times because it was so hard on the bike and once a old lady pulled out in front of me as I hit 120 in town four lanes , whitch was a 30 MPH zone and she didn't realize I was going so fast. If you floor an engine in neutral with no load you can get alot more RPM than lugged down in last gear pushing air at 88MPH........

_____________________________

Hey Buddy -That was the most spectacular crash I've ever seen , That rolling cart wheel with parts slinging out was cool...

(in reply to Harry Lagman)
       Post #: 54

RE: 1 horsepower, really the power of a horse? - 9/6/2007 5:13:13 PM   
gkamysz


 

Posts: 1570
Joined: 6/24/2003
From: Crystal Lake, IL, USA
Status: offline 		Wow, this "physics" discussion is impressive. The fact that a "horse power" doesn't represent the work of an actual horse is irrelevant. HP is a simple mathematical equation.

Longevity of an engine is strictly a design issue. Yes, a Nelson .40 really puts out 3HP. Just like some of the .21 size car glow engines do. With appropriate gearing you could replace a 3HP Briggs in your lawn mower. Would it be cost effective or long lasting? No, but you would save a lot of weight, if that was important.

On the motorcycle example. If the engine couldn't keep the bike at top speed in top gear this just means that it was geared incorrectly, or 6th gear was there strictly for economy at cruise than running at top speed. BTW, a little research turned up that the successor RD400 used much closer ratios on 4,5, & 6. Like Dar implies, the bike probably topped out in fifth not sixth. Or, the aftermarket pipe was not tuned correctly. Suzuki produced racing motorcycles with up to 14 gears for use with two stroke racing engines with teeny tiny power bands.

http://www.suzukicycles.org/history/history_04-race-1960-1967.shtml

Scroll down to 1967. Those are some tiny cylinders at ridiculous RPM and HP. Imagine one of the three 16.6cc cylinders in the RP68 turning 20kRPM and making 6.3HP. Wow, that doesn't sound all that far off a 1.05ci ducted fan engine now does it? Except that this was 30 years before hobby engines reached that potential.


Hobby engine ratings aren't ridiculous. In most cases they just aren't practical. The Nelson's rating is practical because that's the only way it's used, 26-28kRPM on whatever prop gets it there. A sport LA .40 with a 1HP rating at 16kRPM is not practical because it's normally loaded well below that. We could say the same thing about a sports cars that never sees full throttle. So what if your Viper has 500 HP, if you never use it?

The hobby of micro tractor pulling is virtually unknown, but these guys pull over 700 pounds on tractor pull sleds with .15 car engines. They do it all with gearing. I don't know what kind of weight the little 1/2A class pulls.

http://prettyboypullingteam.tripod.com/index.html

_____________________________

Greg

(in reply to speedster 1919)
       Post #: 55

RE: 1 horsepower, really the power of a horse? - 9/6/2007 8:24:29 PM   
Flyboy Dave



Posts: 13447
Joined: 3/20/2002
From: San Bernardino County, CA, USA
Status: offline 		....the problem with this picture is....

....the horse is walking, not working hard
....the "pull" is only 180 pounds
....the horse is pulling on a lever

So as you can see (and figure) this "rating of the power of a horse is silly to begin with.
A horse with a 180 pound rider could walk for days without stopping. The horse could pull
probably 20 times the 180 pound weight given in the formula by Mr. Watt.

If you look at the fact that torque is what creates mechanical horsepower you will
discover why one of our tiny glow engines rated at one HP couldn't lift hardly anything....

....they produce hardly any torque. The only reason they get the wild HP rating is because of
the RPM used in the multiplier. That is the reason I can squeeze the prop shaft of a so called
one GP glow engine and stop it with two fingers....

...no torque. The horespower rating of our glow engine is only due to the RPM, not the
actual power (torque).

The aqctual power (torque) of the tiny piston pushing on the crankshaft via the connecting rod
is probably more like 1/1000 of a horsepower.

And BTW....if you geared the tiny engine down to 750/1 ratio, you would probably lose
50% of the power of the engine....yes, you would not gain power....you would lose power due
to the mechanical losses involved in the shafts and gears needed. The actual torque of the engine
at the crankshaft would remain the same....the power at the final output shaft would be much less.

Much the same loss as an automobile engine of 300 HP, only puts about 150 to the rear wheels.

FBD.

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_____________________________

An engineer says.... "That won''t work".
A mechanic says..."Oh yeah, watch this".
"Old Age, and Treachery will overcome youth and skill".
Revver Bro #4.

(in reply to gkamysz)
       Post #: 56

RE: 1 horsepower, really the power of a horse? - 9/6/2007 9:06:38 PM   
Jim Thomerson



Posts: 2822
Joined: 10/9/2002
From: Austin, TX, USA
Status: offline 		No, a horse with a 180 lb rider cannot walk for days without stopping. It was a well known and documented fact that a human can walk down and catch a horse. The horse will give out before the human does. My father told me he had seen this done several times. It was a common practice for guys coming west with little in the way of resources. All you need is a rope, some parched corn and a canteen.

(in reply to Flyboy Dave)
       Post #: 57

RE: 1 horsepower, really the power of a horse? - 9/6/2007 9:12:50 PM   
Red B.


 

Posts: 1022
Joined: 8/29/2002
From: Jonkoping, SWEDEN
Status: offline 		Flyboy Dave,

By writing "power (torque)" you are probably confusing a lot of people.
Power and torque are not equivalent physical quantities!

Power is a measure of how much work is produced per unit time. For rotating mechanical machines

power = torque * rpm * (a constant).

The constant doesn't matter for this discussion so let us simplify the equation to

power = torque * rpm.

Both torque and rpm are needed to produce power.

A simple electrical DC motor illustrates the principle:

When connected to a battery the motor will produce its maximum torque when it is stalled, i.e., at zero rpm.
Irrespectively of how high the torque is, no useful power is produced as long as the shaft is held stationary,

high torque * zero rpm = zero power.

If the motor is allowed to spin freely without any external load such as a propeller, rpm will be high, but again no useful power is produced because the motor is not exerting any torque on any external object,

zero torque * high rpm = zero power.

Only when the motor is rotating and at the same time exerting a torque on some external object is useful power produced.

In between these two extremes, there exists a RPM at which the motor operates at maximum efficiency. If that RPM is not optimal for the intended application a gearbox may be used to shift the RPM downwards and at the same time increase the torque available or vice versa. Unfortunately gear boxes always cause some frictional losses so there is not a 1:1 correspondence between RPM decrease and torque increase.

In both examples above the electrical power provided by the battery is wasted inside the motor. In the first case it is wasted as heat in the windings of the motor (Ohmic heating) and in the second case power is wasted inside the motor through friction in bearings, air resistance of the rotating armature and Ohmic heating.

< Message edited by Red B. -- 9/6/2007 9:17:41 PM >

_____________________________

/Red B.

(in reply to Flyboy Dave)
       Post #: 58

RE: 1 horsepower, really the power of a horse? - 9/6/2007 9:14:22 PM   
Flyboy Dave



Posts: 13447
Joined: 3/20/2002
From: San Bernardino County, CA, USA
Status: offline 		....let's look at another example. Say a man can produce 1/10 of one HP. Just about everyone
knows how the winch on the front of a boat trailer works. The man can pull a several hundred
pound boat with the aid of the gear reduction, yes ?

The man however, is still producing 1/10 HP....he cannot produce more. Same thing with the
tiny engine....you can gear it down, but the power of the engine itself does not increase....

....the mechanical advantage increases. The man with a lever can move a lot of weight, but
his 1/10 HP remains the same, no matter what.

If a 100 pound man with 1/10 HP, and a lever moves a 1,000 rock...then his HP goes up by the
power of 10, to one full horsepower, right ?

Wrong. The tiny engine gets the big rating by spinning a two ounce weight at 20,000 RPM, and
end up with a one HP rating. So the tiny engine is a strong as a horse, right ?

Wrong.

FBD.

_____________________________

An engineer says.... "That won''t work".
A mechanic says..."Oh yeah, watch this".
"Old Age, and Treachery will overcome youth and skill".
Revver Bro #4.

(in reply to Flyboy Dave)
       Post #: 59

RE: 1 horsepower, really the power of a horse? - 9/6/2007 9:19:53 PM   
Flyboy Dave



Posts: 13447
Joined: 3/20/2002
From: San Bernardino County, CA, USA
Status: offline 		Red....true, the word torque throws people off. Electrical motors are a totally other ball game
and I didn't want to get into that. A 1/3 HP electric motor puts maybe the torque of about 20
small glow engines, but loses out in the HP rating because it only turns about 2,000 RPM.

FBD.

_____________________________

An engineer says.... "That won''t work".
A mechanic says..."Oh yeah, watch this".
"Old Age, and Treachery will overcome youth and skill".
Revver Bro #4.

(in reply to Flyboy Dave)
       Post #: 60

RE: 1 horsepower, really the power of a horse? - 9/6/2007 9:25:26 PM   
jaka


 

Posts: 4523
Joined: 12/11/2001
From: Upplands Vasby, SWEDEN
Status: offline 		Hi!
One horse power (hp) is one horse power ! whether it is produced by a horse or a .40 glow engine doesnt matter!
It's all about the leverege /gearing.

If it takes 1 hp to lift 75kg one meter in one second (the definition of 1 horsepower) then this could be done by a horse, cow, dog, mule, man or ...even a .40 engine delivering one horse power....as long as the gearing is right.

< Message edited by jaka -- 9/6/2007 9:31:51 PM >

_____________________________

Jan Karlsson Airracing products
MVVS, Motul "Micro" all synthetic oil

(in reply to Flyboy Dave)
       Post #: 61

RE: 1 horsepower, really the power of a horse? - 9/6/2007 9:45:20 PM   
Red B.


 

Posts: 1022
Joined: 8/29/2002
From: Jonkoping, SWEDEN
Status: offline
quote:

ORIGINAL: Flyboy Dave

Red....true, the word torque throws people off. Electrical motors are a totally other ball game
and I didn't want to get into that. A 1/3 HP electric motor puts maybe the torque of about 20
small glow engines, but loses out in the HP rating because it only turns about 2,000 RPM.

FBD.


I choose an electrical motor for my example to illustrate the fundamental difference between power and torque.
Because of the nature of the combustion process, engines produce their maximum torque at some RPM different from zero. Other than that, the same principles apply as far as rpm, torque and bhp are concerned.

_____________________________

/Red B.

(in reply to Flyboy Dave)
       Post #: 62

RE: 1 horsepower, really the power of a horse? - 9/6/2007 9:59:59 PM   
Bax