Donate SIGN UP

Hp Calculation Help Needed Please

Avatar Image
bill barlow | 16:07 Sun 08th Sep 2013 | Science
11 Answers
An engine crankshaft has a throw of 17mm.The piston exerts a force of 800kg at 2500rpm.What is the theoretical hp?
Gravatar

Answers

1 to 11 of 11rss feed

Avatar Image
Circumference = 0.107m Force = 8000N Work = Force X Distance = 8000 X 0.107 = 855J Crankshaft frequency = 2500/60 = 41.7 Hz Crankshaft period = 1/41.7 = 0.024 second Power = Work/Time = 855/0.024 = 35625 Watts = approx 48 Horsepower This assumes the piston is exerting a constant force of 8000N for the entire 360 degrees of revolution of the crankshaft which is...
21:14 Sun 08th Sep 2013

By force do you mean the Torque?
HP=(RPM * T) / 5252?
Sorry, I realise you do mean Force not torque
HP = 2(pi)(T)(RPM)/33000

T = torque = force x radius

everything must be in foot-pounds
Question Author
No Mark. Imagine the 800kg as weight.
Torque = force x radius
Then put that into the formula.
I'll leave you to crunch the numbers
Question Author
Sorry my answer to Mark should be to factor-fiction
Circumference = 0.107m
Force = 8000N
Work = Force X Distance = 8000 X 0.107 = 855J

Crankshaft frequency = 2500/60 = 41.7 Hz
Crankshaft period = 1/41.7 = 0.024 second

Power = Work/Time = 855/0.024 = 35625 Watts = approx 48 Horsepower

This assumes the piston is exerting a constant force of 8000N for the entire 360 degrees of revolution of the crankshaft which is unlikely.

An adjustment to teddio's formula is needed to account for the average proportion of a revolution that is a power stroke and sine correction for the conversion of linear motion to rotation. In addition the connecting rod angle changes throughout the power stroke so the 800kg force is only realised at the top and bottom of the stroke when no rotary motion is imparted. The length of the connecting rod has to be known too.
Another adjustment is needed because 17mm =/= 0.107m...
Jim, if the throw or radius is 17mm or 0.017m then the circumference will be 0.107m.

1 to 11 of 11rss feed

Do you know the answer?

Hp Calculation Help Needed Please

Answer Question >>