Just a simple question...

[CaseyD]

It was made clear at steam school that the dual HP ratings for steam traction engines is boilerHP-EngineHP. With that being known, what is the reasoning behind the dual HP ratings for early fuel oil and gasoline tractors?

Thanks, to whomever knows..

[M Kerkvliet]

It was made clear at steam school that the dual HP ratings for steam traction engines is boilerHP-EngineHP. With that being known, what is the reasoning behind the dual HP ratings for early fuel oil and gasoline tractors?

Thanks, to whomever knows..


Drawbar and PTO HP Casey...

[CaseyD]

But I thought that the drawbar HP was irrelevant, and cannot be determined?

[Lee]

Drawbar hp is relevant in that it is the maximum lbs that a tractor will pull in ideal conditions. There is a formula to determine this by using how many lbs were pulled, distance it pulled the load and length of time it took to pull it. The pto (flywheel) hp is measured basically right off the engine. There is no friction to overcome from gearing, bearings, etc., so the rating will be higher.

[CaseyD]

So the drawbar hp is likely determined on a gravel road, or something with not much rolling friction, then? It takes different amounts of power to push the tractor's own wheels, too.

[Lee]

Ideal conditions would be where the tractor would be able to get the most pulling power to the ground. The photo you posted in the steam traction section is a perfect example of ideal conditions.The engine has the weight on the rear wheels and spinning just a little bit. If you could hook a gauge that measured lbs between the drawbar and the hitch of the skid and took a reading right before the engine could not pull anymore, that would be the maximum weight pulled. By knowing how long it took to cover a given distance, drawbar hp can be determined. This was one of the reasons the University of Nebraska started testing tractors. Some companies exagerated their tractors horsepower. The Nebraska tests were a way of giving the farmers an objective opinion on tractor performance. Very interesting reading, highly recommend getting the book.

You are right about the power it takes just to move the tractor. It also affects the drawbar horsepower. It would be interesting to compare the horsepower needed for American steam plowing and British steam cable plowing.

[Ned]

Heres just my two bits. Most british steam engines atleast the earlier ones where rated with nominal horse power which ment a 6 horse engine would require 6 horses to move it around. you can see in photos or videos that the bore and stroke would translate over here (in the U.S) as a much larger engine

just my two bits
Erik the NEd
p.s less than a month until the show :hide: