Horsepower comparrison

Hi, Gauntjoh.
I am open to correction here but it was my understanding that back in 'pre-history', a rough guide was that drawbar hp would be approximately 75% of the flywheel hp of the engine. The lower figure was due to losses through the transmission, differential, final drives, etc..

If my memory serves me correctly, the formula for working our rated hp was:

bore X stroke X No of cylinders X RPM
33,000

For more info., see Wikipedia: http://en.wikipedia.org/wiki/Horsepower

Make yourself a sandwich before you read the above.

Then along came things like super-chargers and turbo-chargers and aftercoolers, torque converters and power-shift transmissions, electronic injection and variable valve timing, etc., and the rated hp figure became somewhat meaningless.

Hope this helps.

Horsepower is a measured, calculated amount of power, produced within a certain time. To be precise, it's 33,000 ft lbs/minute.

The difference between old tractors and new tractors is torque and reciprocating mass. Newer engines run a lot less mass, and produce power at higher RPM. Thus, maximum torque figures are lower. They can do the same amount of work as older tractors, but at higher engine speeds. They need to keep up RPM to produce the HP.

The heavier reciprocating mass of older engines means they "lug" more strongly than newer engines, and have a higher torque rise.
Thus they "feel" like they have more power.

Older tractors have higher friction losses, compared to newer designs, that have lower-friction components. This assists in getting more power to the ground.

The 7M has a tested Belt HP of 92.84, and a tested DBHP of 80.44. AFAIK, no Flywheel HP rating was ever stated for the 7M tractor.

I have my rack setting book from Cat that I used at the dealer for dyno testing and it says the D7 7M is 98 brake HP and 93 belt HP and is from the Cat form # 30782-1 instruction book.The settings are at 1000 RPMs full load.

If an engine has a higher rpm to generate larger hp, wouldn't that mean that it will wear out faster? Haven't we traded higher hp for greater wear? I know my Best Sixty (and the Cat Sixties) had an rpm tops of around 600 (or was it 850?), but at idle, you can hear each cylinder fire - a wonderful sound!

I enjoy reading the technical things as above, and learn a lot from the folks who post. Thanks a bunch.

GWH

If an engine has a higher rpm to generate larger hp, wouldn't that mean that it will wear out faster? Haven't we traded higher hp for greater wear? I know my Best Sixty (and the Cat Sixties) had an rpm tops of around 600 (or was it 850?), but at idle, you can hear each cylinder fire - a wonderful sound!

I enjoy reading the technical things as above, and learn a lot from the folks who post. Thanks a bunch.

GWH

Horsepower is a measured, calculated amount of power, produced within a certain time. To be precise, it's 33,000 ft lbs/minute.

The difference between old tractors and new tractors is torque and reciprocating mass. Newer engines run a lot less mass, and produce power at higher RPM. Thus, maximum torque figures are lower. They can do the same amount of work as older tractors, but at higher engine speeds. They need to keep up RPM to produce the HP.

The heavier reciprocating mass of older engines means they "lug" more strongly than newer engines, and have a higher torque rise.
Thus they "feel" like they have more power.

Older tractors have higher friction losses, compared to newer designs, that have lower-friction components. This assists in getting more power to the ground.

The 7M has a tested Belt HP of 92.84, and a tested DBHP of 80.44. AFAIK, no Flywheel HP rating was ever stated for the 7M tractor.

[QUOTE=OzDozer;39575]Horsepower is a measured, calculated amount of power, produced within a certain time.

The difference between old tractors and new tractors is torque

Torque vs HP can be very misleading- old racer saying-- HP is for going fast & torque is for pulling stumps--- some drag racers & truck pullers find this out by experience- some salt flat guys find it out the hard way....as one of them told me as we were discussing the subject "dynos don't have wheels"-- also dynos don't have tracks..side note-- had a chart w/ drawbar pull on my 2U-- WHEN THE 1200RPM ENG WAS LUGGED DOWN TO 800 RPM THE DRAWBAR PULL ALMOST DUBLED--[had warning not to operate in this mode for long periods of time]-as near as I could figure it just let the gov open up the pump--so HP ratings probably not reflecting this- don't know if othe cats do this or not??

A dyno doesn't need wheels or tracks. It's to test the performance of an engine that will power something with wheels or tracks. Horsepower is basically the rate of ability to do work or Force times Distance divided by Time. What the old racers were really trying to say was Stump pullers need the Force they want the Distance but it still comes down to Horsepower.
Later Bob