Onan 15JC 3CR /120/240

[Onan Dan]

Question on horse power rating? on the onans where it shows horse power like 31 BHP what does the B stand for i always thought HP stood for horse power? thx

[Ed Sparks]

base HP
Most Onan's were overbuilt for their ratings

[moteurdelco]

bhp;brake horse power.

[Billy J Shafer]

Some called it base HP. Some said Brake HP.

[Isaac-1]

Engine horse power will vary depending on a number of factors including temperature, altitude, relative humidity, and even things like oil temperature, as a result there are various ways to measure it (often ways that seem like cheating to increase the number), like BHP or net HP, adjusted HP, etc. I forget the details of each, but I think BHP includes max HP the engine can produce with front accessories like battery charging alternators, and fans disconnected.

Ike

[GHanners]

I never paid attention to *CLAIMED* HP ratings no machine in the world to measure HP all dyno's measure torque and HP is calculated # and depending on the correction factor you can get any # you want
Also I've seen some dyno rooms with a positive pressure with "cooling fans" as high as 3psi well that just like strapping a blower on top so the motor looks better for the customer
give me the raw uncorrected torque #'s they dont lie

BTW another way to spot a doctored dyno sheet hp & tq dont cross at 5252rpm

[MBB]

Almost all Horsepower ratings these days are inflated. Anyone with a Ridgid or most other shop vacs for instance know that. My shop vac has a horsepower rating of 7HP. Well it doesnt take a genius to figure out that thats not so. A motor that size would weigh a ton, wouldnt run on 120v, Wouldnt have a 13amp rating with a 16 or 14 gauge cord. If all those things were possable the cost of the motor alone would be $1000.00. Im not sure how with all the goverment oversite that these hp claims can be made for any tools. The unsuspecting consumer sees these numbers and figures bigger is better rather then the tools actual performance.

[Kevin K]

Originally Posted by MBB

Im not sure how with all the goverment oversite that these hp claims can be made for any tools. The unsuspecting consumer sees these numbers and figures bigger is better rather then the tools actual performance.

What oversight? That's the problem. Every time a regulation or consumer protection law is proposed, certain of our "representatives" decry it as "interfering in private business" or "overburdening industry with expensive regulations". In Europe, they actually have standards that mean something and must be adhered to before a product can be sold.

[MBB]

The problem is that 80 some percent or more of are legislators are attorneys. They have no practical knowledge for the areas there writing laws or regulations for. It used to be (in the old old days) legislature were made up of diverse people from the community blacksmith, storekeepers, lawyers. etc. They did there job went to congress at the appointed time represented the people and went back to there job. There was a vast amount of knowledge diverse social and economic people and ideas. Today its a buisness. We have alot of laws, regulations in some areas and are lacking in common sense other areas. Take away there health care and pensions and maybe will find people who are in it for the people.

Sorry to get off topic.

[Leon N.]

Good Morning. I would like to address Onan Dan's original question. BHP stands for brake horse power as already mentioned. Why the term "brake"? Back years ago in the lab, we used what is called a prony brake to measure BHP and torque of an engine. By definition, if a engine shaft generates 550 foot pounds per second that is a definition of 1 BHP. We used a scale attached to a fulcrum and a friction clutch, sort of crudely speaking to measure not only the BHP but the "twisting action" or torque of a motor. Torque is measured in ft pounds, period.

That being said, I would like to say something about the early on Onan engines, specifically the J-line designs. I have sent some of you, I know I sent a copy to Billy, that has graphs of the J line engine torque, continuous BHP, max BHP and fuel consumption versus RPM. If you look at these performance curves @ 1800 RPM you will quickly see that for example, the model JB can continuously deliver 12 HP or 12 x 746 = 8952 watts or a maximum of 14 x 746 = 10444 watts to the magneciter (alternator). BTW, 746 watts equates to 1 HP or 550 ft-pounds per second. .

In the early days of the Onan Corp, I would bet there philosophy was to build the best product they could come up with. They probably had little competition and there for they did not go cheap or cheaper until for example, they replaced the magneciter.

I agree, today the HP ratings are probably over inflated, but I can tell you folks, my JB Onan spec is rated 7500 watts continuous and 7500 watts standby. I have honestly pulled 8500 watts and pegged the 50 amp ammeters during motor starting.

So, the Onan engines I believe could easily generate magic smoke if one does not provide adequate electrical protection for the back end.