What is Horsepower?
- Thread starter Simonizer
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Lakeside53
Stihl Wrenching
nope... The HP of your truck doesn't change because of the gear in use (assuming no losses in the gear train).
RiverRat2
Serio Tree Freak
OH I see said the Blind Man
I see what you are saying!!!! well think about this then in regard to engines,,
I have found that An engine can have less diplacement and HP than a similar type of engine but develop more ft. lb of torque simply because it internals (Rods} have a longer stroke and a crankshaft with longer throws,,, and the smaller displacement engine will out pull the bigger one seemingly easier!!!!!
Go figure!!!!!
I see what you are saying!!!! well think about this then in regard to engines,,
I have found that An engine can have less diplacement and HP than a similar type of engine but develop more ft. lb of torque simply because it internals (Rods} have a longer stroke and a crankshaft with longer throws,,, and the smaller displacement engine will out pull the bigger one seemingly easier!!!!!
Go figure!!!!!
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Lakeside53
Stihl Wrenching
and.....
chowdozer
Addicted to ArboristSite
Take two identical engines. Put longer rods in one and move the wrist pin height correspondingly and the long rod engine will make more horsepower, more rpm and be more octane tolerant. Why do you think that is?
RiverRat2
Serio Tree Freak
In light of all the great info in this thread about
HP and rotation, time, angular velocity and such :deadhorse: would it be possible that one might
Construe that with a couple of differnt CS That have similar characteristics of displacement but with one clearly having more,,,, err ahhemmm (can I use the T word when talking about saws? I dont want to get Peter fired up again,,,,) TORQUE!!!!!!! than another :hmm3grin2orange: :hmm3grin2orange:
HP and rotation, time, angular velocity and such :deadhorse: would it be possible that one might
Construe that with a couple of differnt CS That have similar characteristics of displacement but with one clearly having more,,,, err ahhemmm (can I use the T word when talking about saws? I dont want to get Peter fired up again,,,,) TORQUE!!!!!!! than another :hmm3grin2orange: :hmm3grin2orange:
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RiverRat2
Serio Tree Freak
cause it has more displacement?????
Sheesh CD,,,, I Dunno :monkey: :monkey: :monkey:
Sheesh CD,,,, I Dunno :monkey: :monkey: :monkey:
chowdozer
Addicted to ArboristSite
A longer connecting rod won't change the displacement. It will decrease the skirt load on the piston and also cause the piston to dwell at TDC and BDC longer due to the decreased rod angle. All this translates into moving the T***** curve up in rpm which increases h****p****.
RiverRat2
Serio Tree Freak
Cool!!!!!!!!!!!!:jawdrop:
Simonizer
Addicted to ArboristSite
Excellent analogy. (I'm almost surprised)
Visualizing that muscle again!
If you look at the question asked, I think Helsel is right. The question was not about hp, but about the force encountered by the dogs against the log at a given speed. And there the chain setup matters very much imo ...
Al Smith
Addicted to ArboristSite
OK.long stroke engines,here's an example of pure torque.I have a 1950 Buick,straight 8,248 cubic inches,125 HP.It will take off from a stop in high gear,at idle and accelerate with no problem other that it's a little slow getting"out of the gate".Try that with your Honda accord.
Crofter
Addicted to ArboristSite
How about the horsepower to weight ratio Al? One problem with getting your horsepower via the high torque route is that a lot of the drive train components must be so much stronger. Transmit the same horsepower at lower torque and you save a lot of material. In either case you have to adjust crank throw to arrive a nearly the same piston speed to match the burning rate of the fuel you are using or your efficiency goes out the window. Drop the piston speed too much (in relation to charge expansion rate) and detonation happens unless you drop compression ratios to 6 to 1 or so. You wont find the efficient high compression ratios on the high torque low rpm engines.
Goat
ArboristSite Operative
Wrw
Those engines have a low static compression ratio because they are configured for forced induction.
There is a big difference between static & dynamic compression ratios. DCR is what your mixture actually sees and is what counts.
Those engines have a low static compression ratio because they are configured for forced induction.
There is a big difference between static & dynamic compression ratios. DCR is what your mixture actually sees and is what counts.
Yes, I just saw the ratio in Crofter's post and threw out something of interest. The supercharger is listed in the specs.
Al Smith
Addicted to ArboristSite
True indeed! High torque lower rpm engines are by design build bull strong with huge bearing surfaces,massive crankshafts etc,they have to be.Even in the world of chainsaw engines.If one could compare a crankshaft from an old Mac or Homelite to that of a modern saw you will see a marked difference.
In dealing with certain high torque engines,one of the worst things you can do is lug them excessively.I can take for instance bog my old D4 Cats to the point of being able to count the rpms but this is very hard on the crankshaft.Even at only 35.68 HP,those old machines have been known to twist a crank in two.They have 3 1/2" mains and 3" throws too.
NovaMan
ArboristSite Operative
I've never heard of matching piston speed to fuel burn rate before; "car guys" like me are mostly concerned with piston speed because it is a decent measure of how much the rod will be stressed. For example, rods usually break before the piston outruns the flame front, at least with modified American V8s.
Just out of curiosity, what do you consider to be a high compression ratio? What about low RPM?
Crofter
Addicted to ArboristSite
Novaman I think you are referring to rod failure from tension at high revs on a forced downshift etc. if you are talking about piston outrunning flame speed. The piston wont outrun the flame very much if the flame is driving it. I was referring more to not having piston speed too low. Piston speed, stroke, rpm and compression ratio are rather tied together in determining where an engine will develop its maximum horsepower. If burning gasoline is the fuel, these things have to be matched to its expansion rate, within reason, to have any kind of efficiency. How you put it together determines the character of the engine. As was mentioned relative rod length and such things as bore offset can have some interesting effects on changing piston speed and accelleration during different phase of crank rotation. Where weight and space is a concern a given horsepower is easier achieve with less torque and more rpm. It will be interesting to see what comes of auto race engines once solenoid operated valves become the norm in a few years. I wonder if the old camshaft will still be king on race day.
