Is 50 HP really 50 HP?

[4570Man]

Who could blame one for believing nothing anymore. I once saw a shop Vac with 5 (or was it 6) HP sticker. It had 110 volt 15 amp plug. You can figure about 737 watts per horsepower. You can get about 1700 watts from a normal outlet so how did they get 5 or 6 hp? Maybe it had a free energy collector.

They meant to say it was 6 hp when lightning struck your electric meter the same time the shop vac was running. Portable air compressors are about as bad.

 

[jenkinsph]

Who could blame one for believing nothing anymore. I once saw a shop Vac with 5 (or was it 6) HP sticker. It had 110 volt 15 amp plug. You can figure about 737 watts per horsepower. You can get about 1700 watts from a normal outlet so how did they get 5 or 6 hp? Maybe it had a free energy collection system.

Anything to fool and fleece the consumer.

I have used the 5-6 hp vacuum example with a 15A plug in the past too and almost word for word.

Another one I used to get a kick out of was speaker ratings. Many years ago Altec Lansing built some efficient 15" speakers that could handle about 40 watts yet deliver a very high sound level. Fast forward to the little speakers today that handle 1000 watts while producing a similar sound level I never understood the people who were concerned about how much power a speaker could handle, I was concerned about how accurate the sound was.

More on track with this forum though is gear box ratings. If you look carefully at a 90 hp rated gear box it is a good idea to check the speed rating for the test. If the gear box is rated for a much higher rpm than what you are using it for the rating would be much lower.

 

[4570Man]

I saw an antique steam engine that was 600 hp. It would destroy a 600 hp gear box since it turned at 80 rpm and produced 38,000 foot pounds of toque.

 

[TomSeller]

I saw an antique steam engine that was 600 hp. It would destroy a 600 hp gear box since it turned at 80 rpm and produced 38,000 foot pounds of toque.

That is a LOT of torque.

 

[Retiredguy2]

Who could blame one for believing nothing anymore. I once saw a shop Vac with 5 (or was it 6) HP sticker. It had 110 volt 15 amp plug. You can figure about 737 watts per horsepower. You can get about 1700 watts from a normal outlet so how did they get 5 or 6 hp? Maybe it had a free energy collection system.

Anything to fool and fleece the consumer.

I have a few big Craftsman shop vacuums that range from 4.25 to 5.5 horsepower, and I have wondered the same thing: How a little electric motor can possibly develop that much horsepower. I have an older Craftman push mower with the 190cc Briggs engine and it was rated about 5.5 or 6 horsepower...might be over rated itself but...which motor do you think has a more honest power output rating?

 

[LD1]

More on track with this forum though is gear box ratings. If you look carefully at a 90 hp rated gear box it is a good idea to check the speed rating for the test. If the gear box is rated for a much higher rpm than what you are using it for the rating would be much lower.

Industrial gearboxes are rated by HP AND RPM.

If a gearbox is rated for 5 HP with a 1750 RPM motor, it will be good for 10 HP if using a 3600 RPM motor.

Cause is all about torque.

5 HP @ 1750 RPM is gonna make 15 ft-lbs
Double the RPM's and you can double the HP and torque remains the same.

A 90HP bushhog gearbox @ 540 RPM has to handle 875 ft lbs input

I have often though AG gearboxes and industrial stuff were rated way different. A idustrial right angle gearbox of similar shaft sizes and ratios would be lucky to carry a 10 HP rating

 

[Turbys_1700]

My dad sold Allis Chalmers back in the day. Those units were rated at the PTO. Our D-17's were considered 50 HP tractors. The Nebraska tests show those units to put out around 53 HP at the PTO so engine HP is around 60. Our 8050 is rated at 150 HP and again the Nebraska tests show 153 at the PTO. Back then most manufacturers calculated them at the PTO. Today most of the manufacturers state them at the engine and PTO.

 

[SPYDERLK]

In taking a quick look at US navy aircraft of WWII and later, comparing the radial piston engined Grumman F8F **** cat with 2250 hp, 7650# empty wt, 455 mph max speed and the later Grumman F9F turbojet with 8500 ft-lbs of thrust, 11,866# empty, and 647 max speed it is interesting that they (the planes) are in about the same sized (L x W) package but you get a lot more performance from the turbine. Course variables exist like shaft losses and blade efficiency and all that but assuming designers gave it their best shot at the time, it's an impressive difference.

Course fuel consumption would be an interesting parameter to look at using 100+ octane AV. gas vs JP-4? (Kerosene) and price per gallon. Guess one could look that up if all that interested.

What is a ft-lb of thrust?

 

[LD1]

If thrust truly was measured in ft-lbs, that would imply there would be a time factor. How fast it can move XXXXX pounds that 1-foot. Thus it would be easy to convert to HP for comparison reasons.

HP and thrust cannot be compared. Its apples to oranges. Thrust is just the max ability to push something. 8500 pounds in the case of the F9F. If that jet weighed less than 8500#, it would have the ability to fly and accelerate vertically.

HP has the TIME element. How fast a force can be applied. Different measurement all together. Like trying to convert inches to gallons or something.

 

[buickanddeere]

Who could blame one for believing nothing anymore. I once saw a shop Vac with 5 (or was it 6) HP sticker. It had 110 volt 15 amp plug. You can figure about 737 watts per horsepower. You can get about 1700 watts from a normal outlet so how did they get 5 or 6 hp? Maybe it had a free energy collection system.

Anything to fool and fleece the consumer.

Peak vs continuous . Same problem with choosing consumer grade generators . There capacity in large print or the capacity in small print .