I need a hydraulic wizard

[gtstang462002]

I've got two 8hp Briggs I/C engines on Troybilt rototillers and no way would an 3.5hp Honda put out the same horsepower. It just ain't happening.

Not claiming the same HP

 

[lt1nut]

Horsepower is a measurement based on torque and rpm. From the engineersedge website:

"To determine the rotary horsepower of an object into rotary motion (rpm) use the following equation.

Equation:
P = (T x N) / 5250

Where:

P = Power, hp
N = Rotational shaft speed, rpm
T = Torque, lb-ft"

In other words, multiply torque times rpm, divide that amount by 5250.

Play around with the numbers, increasing rpm while keeping torque the same and you will be surprised. It's the reason why a truck with a big block in it will out pull one with a small block even though they both have the same horsepower rating/amount. Torque is what gets things moving, horsepower keeps it moving. Torque is awesome on the street, horsepower is awesome on the race track. Torque is what spins tires...

Hope this helps.

(spell check innop right now, sorry)

 

[gtstang462002]

Horsepower is a measurement based on torque and rpm. From the engineersedge website:

"To determine the rotary horsepower of an object into rotary motion (rpm) use the following equation.

Equation:
P = (T x N) / 5250

Where:

P = Power, hp
N = Rotational shaft speed, rpm
T = Torque, lb-ft"

In other words, multiply torque times rpm, divide that amount by 5250.

Play around with the numbers, increasing rpm while keeping torque the same and you will be surprised. It's the reason why a truck with a big block in it will out pull one with a small block even though they both have the same horsepower rating/amount. Torque is what gets things moving, horsepower keeps it moving. Torque is awesome on the street, horsepower is awesome on the race track. Torque is what spins tires...

Hope this helps.

(spell check innop right now, sorry)

I dont know how accurate that formula really is. If you take any size engine that is rated for a certain HP and RMP and compare it to another that has the same 2 ratings your numbers will be the same. However if there are internal differances such as a longer stroke you are increasing your torque out of that motor. I feel that all of the small engines are improperly rated. None of them should be rated on HP they should all be rated on their torque output. Since they are all intended for working under a load.

 

[kevin j]

Eric: got a reply from applic engr at Haldex, the adjusting screw can bottom out and defeat the unloading valve if screwed in too far, but won't hurt the pump only stall the engine (up to reasonable maximum pressures).
I am trying to reach him today for more explanation, and what the failure modes would be at what pressures, and about shiming the spring.
Will also try to find the 28 I have and look at cartridge tomorrow.


He also sent a nice one page explanation of how the circuit works, really basics, but its pdf and not sure how to post it here.... workig on that.


Formula for hp is exact, because it is the physical definition of hp. However, mfrs can lie or tweak etc. Mainly in what torque and what rpm to use. There are ratings for prime power (thousands of hours) standby power (maybe 100 hours), peak (flashing the maximum on the dyno even for a few seconds until it heats up or changes). all sorts of games. SAE ratings help standardize that. But notice that small lawnmowers are now not sold as '3.5 hp engine', but '5 reserve hp, or lugging ability' or some other marketing term. That rating may be flat out stall torque used to calculate the hp, or it may be comparing it's torque to some other engine. One engine mfr had a term I can't recall, they used peak torque at say 2500 rpm, multipled by max rpm, say 3800, for a fictitious hp it would have if it did both at the same time. Physically could not, did not, but the salesman invented the idea.....
BTW, that Honda with '5.5' in big letters on the side, most places advertise as '5.5 hp honda engine'- -on the Honda website, the engine is rated at 4.6 hp...... so it's not just the obscure names doing the BS.


Your expereince between gas diesel-the gas engine may have been 'rated' at say 4000 or 5000 rpm. Another with same hp but rated at 2500 rpm would have twice the torque (T x rpm, so if rpm is lower, T must be higher). Then if both are actually running at 2500 rpm, the diesel appears stronger with more torque, and the gas engine is actually only putting out half its rated hp. Mfrs won't usually put on an engine they are not squeezing the most out of, but I am just saying there are issues of gearing, engine rpm, torque rise as it lugs down, lots of seat of the pants sensations. Ultimately that perception is what sells the machine, but there is more to it than advdertised hp. a hp is a hp.

Torque is the measured 'twisting force' of the crankshaft, in ft-lbs. It is a force without regard to any distance or speed.
horsepower is 'rate of doing work'. Taking the same torque of a man pulling on a torque wrench or cranking a winch, an engine at 1000 rpm, or and engine at 5000 rpm. All have the same 'twist or torque', but the higher horsepower does more work in same time.

(Gearing down does not add hp, but multiplies torque, reduces rpm, same hp. Another topic totally.)


Illustration: To pull a gravel truck along a road takes 'force' pulling a rope (or torque on a winch crank, or axle input.)
To move that truck up a hill takes force x distance = work done.
To move it up the hill in a certain time is work/time, which defines power.

A 3.5 Briggs will pull a gravel truck up a hill, geared down to walking speed. A 150 hp engine takes it up the hill in a higher gear in a minute. A 500 hp engine takes it up the hill faster yet in seconds. All need the same force, and do the same work, but as time decreases the 'power' required is greater.

Same as splitters. Pressure x area is force. Force times distance of stroke is work done. Work done per time (how fast does it cycle) defines power required.

No shortcuts around physics. Various things might be the limiting factor, may not get the full hp to the ground, but it will never get MORE than the theoretical to the ground.
A system or a drive can be either torque limited, or hp limited, but that is a whole different discussion.


k

 

[BlueRidgeMark]

He also sent a nice one page explanation of how the circuit works, really basics, but its pdf and not sure how to post it here.... workig on that.

Just make it an attachment. First, make sure you are using Standard Editor mode. Check in your "User CP" for that. (Look at the top right of any page you're looking at. It's in the first green bar below all the advertising.)

Now, look along the top row of buttons & stuff in the gray box. You should see a paperclip icon. Click that, and it will open up a new window (a pop-up) to allow you to create attachments.

Here's what it looks like, with the paperclip circled:

If you don't see a screen like that, you are probably using the Basic Text Box editor, which is a royal pain in the patootey.

To set yourself to use the Standard Editor, go to User CP:

Then choose Edit Options:

The scroll down to Miscellaneous Options, and select Standard Editor:

Life on Arboristsite will now be much mo' bettah.

 

[BlueRidgeMark]

No shortcuts around physics. Various things might be the limiting factor, may not get the full hp to the ground, but it will never get MORE than the theoretical to the ground.

+1

Yep. It's amazing how much time & effort people will spendon things that they would have known weren't worth it, if they had only paid attention to BASIC stuff in grade school & middle school science classes, instead of adopting that STUPID notion that it wasn't important because "I'll never use this stuff!"

 

[George G]

Something to play with

http://www.calculatoredge.com/new/horsepower.htm#hp

 

[user 19670]

+1

Yep. It's amazing how much time & effort people will spendon things that they would have known weren't worth it, if they had only paid attention to BASIC stuff in grade school & middle school science classes, instead of adopting that STUPID notion that it wasn't important because "I'll never use this stuff!"

Truer words have seldom been spoken. I myself have sneered that we will never use this stuff. Life has proved me wrong again and again over the years.

 

[cabinman]

Thanks

Eric: got a reply from applic engr at Haldex, the adjusting screw can bottom out and defeat the unloading valve if screwed in too far, but won't hurt the pump only stall the engine (up to reasonable maximum pressures).
I am trying to reach him today for more explanation, and what the failure modes would be at what pressures, and about shiming the spring.
Will also try to find the 28 I have and look at cartridge tomorrow.


He also sent a nice one page explanation of how the circuit works, really basics, but its pdf and not sure how to post it here.... workig on that.


Formula for hp is exact, because it is the physical definition of hp. However, mfrs can lie or tweak etc. Mainly in what torque and what rpm to use. There are ratings for prime power (thousands of hours) standby power (maybe 100 hours), peak (flashing the maximum on the dyno even for a few seconds until it heats up or changes). all sorts of games. SAE ratings help standardize that. But notice that small lawnmowers are now not sold as '3.5 hp engine', but '5 reserve hp, or lugging ability' or some other marketing term. That rating may be flat out stall torque used to calculate the hp, or it may be comparing it's torque to some other engine. One engine mfr had a term I can't recall, they used peak torque at say 2500 rpm, multipled by max rpm, say 3800, for a fictitious hp it would have if it did both at the same time. Physically could not, did not, but the salesman invented the idea.....
BTW, that Honda with '5.5' in big letters on the side, most places advertise as '5.5 hp honda engine'- -on the Honda website, the engine is rated at 4.6 hp...... so it's not just the obscure names doing the BS.


Your expereince between gas diesel-the gas engine may have been 'rated' at say 4000 or 5000 rpm. Another with same hp but rated at 2500 rpm would have twice the torque (T x rpm, so if rpm is lower, T must be higher). Then if both are actually running at 2500 rpm, the diesel appears stronger with more torque, and the gas engine is actually only putting out half its rated hp. Mfrs won't usually put on an engine they are not squeezing the most out of, but I am just saying there are issues of gearing, engine rpm, torque rise as it lugs down, lots of seat of the pants sensations. Ultimately that perception is what sells the machine, but there is more to it than advdertised hp. a hp is a hp.

Torque is the measured 'twisting force' of the crankshaft, in ft-lbs. It is a force without regard to any distance or speed.
horsepower is 'rate of doing work'. Taking the same torque of a man pulling on a torque wrench or cranking a winch, an engine at 1000 rpm, or and engine at 5000 rpm. All have the same 'twist or torque', but the higher horsepower does more work in same time.

(Gearing down does not add hp, but multiplies torque, reduces rpm, same hp. Another topic totally.)


Illustration: To pull a gravel truck along a road takes 'force' pulling a rope (or torque on a winch crank, or axle input.)
To move that truck up a hill takes force x distance = work done.
To move it up the hill in a certain time is work/time, which defines power.

A 3.5 Briggs will pull a gravel truck up a hill, geared down to walking speed. A 150 hp engine takes it up the hill in a higher gear in a minute. A 500 hp engine takes it up the hill faster yet in seconds. All need the same force, and do the same work, but as time decreases the 'power' required is greater.

Same as splitters. Pressure x area is force. Force times distance of stroke is work done. Work done per time (how fast does it cycle) defines power required.

No shortcuts around physics. Various things might be the limiting factor, may not get the full hp to the ground, but it will never get MORE than the theoretical to the ground.
A system or a drive can be either torque limited, or hp limited, but that is a whole different discussion.


k

THANKS kEVIN,...Iam workin on a sofisticated unit that I want to Strip all the BS from and just make high pressure flow..Ill PM you,..As always, spelling is bad,.. Eric

 

[eric_271]

THANKS kEVIN,...Iam workin on a sofisticated unit that I want to Strip all the BS from and just make high pressure flow..Ill PM you,..As always, spelling is bad,.. Eric

WOW you are a sophisticated man, take a 2 stage pump and make a single stage out of it with hundreds of single stage pumps on the market.:hmm3grin2orange: You do a good job keeping me laughing.

 

[user 19670]

THANKS kEVIN,...Iam workin on a sofisticated unit that I want to Strip all the BS from and just make high pressure flow..Ill PM you,..As always, spelling is bad,.. Eric

"just make high pressure flow" opcorn:
"high pressure flow" opcorn:
"pressure flow" opcorn:
flow?

 

[eric_271]

"just make high pressure flow" opcorn:
"high pressure flow" opcorn:
"pressure flow" opcorn:
flow?

LMAO You have to remember, the law of physics is not in cabinman's spectrum. Not much else either as far as that goes.

 

[cabinman]

You Dont Get It

Iam talkin about a sophisticated $37,000 Machine, that has maybe 300 ft of hyd oil circuts, And two seperate pumps, This preticular one is a 40 hp diesel, The service manual is 3 in thick, More saftey and overide equipment than Ive ever seen, Kinda like opening a can of worms and trying to find the tail to match the head of a preticular worm,..WITHOUT PULLING OUT THE WORM I must have posted sompthing to confuse Yaall, As far as you,.. E271,.. Its (way over) your head, Try posting on sompthing more on your leval,. You might try the sponge bob square pants site,...HEHEHEHE Eric

 

[user 19670]

A little bit of knowledge can be dangerous (AND expensive) opcorn: