GOT SOME ANSWERS
marti brought up a good topic under her thread "got some questions". this was further amplified over a few beers today at the local sportbiker watering hole and that is the misconceptions of horsepower and torque. yep we've all seen the numbers the manufacturer's post but it is kind of amazing that even around a group of guys that can quote them they use the terms interchangably. now i am sure rbn has heard the old saying "torque starts races and horsepower finihes them". now just so everyone can win a buck or two at the local watering hole here is what torque and horsepower is.
torque-that which produces or tends to produce torsion or rotation;the moment of a system of forces which tends to cause rotation;the pressure,measured infoot-pounds exerted by a rotating shaft.
horsepower-a unit for measuring power or rate of work,as of the engine of a motorcycle;equivelent to 550 foot pounds per second.
ok breaking it down the rotating shaft is nothing more than the motors crankshaft and horsepower is nothing more then a measurement of work. but let's put it in real world perspective.
single cylinder and 2 cylinder motors with all things being equal will be high torque motors but low on horsepower. the reason is simple as these are low rpm motors and since they are low rpm the results of 550 ftlbs/sec are less.
3,4,6 cylinder motors (these are found in production motorcycles past and present) will be lower torque motors but will always be greater in horsepower again due to the 550 ftlbs/sec since they can achieve greater rpm before hitting the maximum piston speed wall of 3000 ft per second which to this day has motor engineers trying to beat with no avail.
undersquare vs. oversquare motors--
undersquare is where the piston diameter is less then the length of the connecting rod stroke where oversquare is a piston of greater diameter then the stroke length. what the heck does that mean??!! ok let's look at motor i love the royal enfield 500cc single,while the bore is small the connecting rods are long and thus the connecting rod gives a greater lever effect or it's gots gobs of torque. now compare that off aginst an old honda 500cc 4 cyclinder motor. the bore is big the stroke is small and thus it achieves much higher rpms (remember the piston speed wall) before it hits maximum piston speed but it has a much lower torque for the same given 500cc motor size.
real world implications----
a single or twin will be great for heavy traffic since they have a greater torque which translates in to less shifting since the motor will simply torque away.
a multicyclinder will run faster but will require more gear changes in slow traffic due to less torque being available.
now from here it can get really esotric but what it boils down to is this the more cylinders the greater the horsepower but the less torque which explains why the FIM banned the 8 cylinder moto-guzzi and why honda made the oval piston v4 or why the KTM twins were so sucessful in the paris dakar rallies or even why the harley xr750 engine dominates flat track mile races.
so torque and horsepower are not interchangeable but with knowledge the two can be used to greater benefit.
jack
ps. a good bar bet that will always win is ask a smuck what horse power is. the answer is always 550 ftlbs/sec. remebr that and you will never have to pay for a beer ever again,.
torque-that which produces or tends to produce torsion or rotation;the moment of a system of forces which tends to cause rotation;the pressure,measured infoot-pounds exerted by a rotating shaft.
horsepower-a unit for measuring power or rate of work,as of the engine of a motorcycle;equivelent to 550 foot pounds per second.
ok breaking it down the rotating shaft is nothing more than the motors crankshaft and horsepower is nothing more then a measurement of work. but let's put it in real world perspective.
single cylinder and 2 cylinder motors with all things being equal will be high torque motors but low on horsepower. the reason is simple as these are low rpm motors and since they are low rpm the results of 550 ftlbs/sec are less.
3,4,6 cylinder motors (these are found in production motorcycles past and present) will be lower torque motors but will always be greater in horsepower again due to the 550 ftlbs/sec since they can achieve greater rpm before hitting the maximum piston speed wall of 3000 ft per second which to this day has motor engineers trying to beat with no avail.
undersquare vs. oversquare motors--
undersquare is where the piston diameter is less then the length of the connecting rod stroke where oversquare is a piston of greater diameter then the stroke length. what the heck does that mean??!! ok let's look at motor i love the royal enfield 500cc single,while the bore is small the connecting rods are long and thus the connecting rod gives a greater lever effect or it's gots gobs of torque. now compare that off aginst an old honda 500cc 4 cyclinder motor. the bore is big the stroke is small and thus it achieves much higher rpms (remember the piston speed wall) before it hits maximum piston speed but it has a much lower torque for the same given 500cc motor size.
real world implications----
a single or twin will be great for heavy traffic since they have a greater torque which translates in to less shifting since the motor will simply torque away.
a multicyclinder will run faster but will require more gear changes in slow traffic due to less torque being available.
now from here it can get really esotric but what it boils down to is this the more cylinders the greater the horsepower but the less torque which explains why the FIM banned the 8 cylinder moto-guzzi and why honda made the oval piston v4 or why the KTM twins were so sucessful in the paris dakar rallies or even why the harley xr750 engine dominates flat track mile races.
so torque and horsepower are not interchangeable but with knowledge the two can be used to greater benefit.
jack
ps. a good bar bet that will always win is ask a smuck what horse power is. the answer is always 550 ftlbs/sec. remebr that and you will never have to pay for a beer ever again,.
