Horsepower? Gas vs. Electric Motors

[Spencer]

I have a new cement mixer on the way. The unit I bought came in both a gasoline and electric versions (see attachment). I chose the Honda gas engine model for freedom of use. My question is how come the electric motor (110 volt, 6 amp) is rated at 1/2 horsepower and the gas engine is rated at 2.5 horsepower? Both motors will have the same load on them and perform the same task so what gives with these horsepower ratings? Just wondering, and hoping to learn something new.

 

[BB_TX]

I think you would have to look at the torque ratings and/or the gearing of the electric vs the gas engine models. Generally speaking, the electric motor is probably going to run at a much higher rpm than the gas engine and would be geared differently. You know the old saying, you can run a locomotive with a pocket watch if it is geared correctly (albeit not very fast /forums/images/graemlins/smirk.gif).

 

[StanInCalif]

A gasoline engine produces a finite amount of horsepower and is rated at the maximum it will produce under ideal conditions. An electric motor will produce many times its rated horsepower when the load demands, but at the expense of temperature rise. The rating given is usually conservative and is intended for continous duty.
The normal replacement for a 1 HP electric is a 3 HP gas. 1/2 to 2.5 HP seems a bit excessive; maybe 2.5 was the smallest engine they could find.

 

[shado]

Well, one thing that was not pointed out in the ad, is the SAME gearbox being utilized for either the electric version & the gas engine version? There may be two different gearboxes used depending on what's driving it, the gear ratios may be different and allow the smaller horsepower to perform the same job, may not rotate the drum at the same RPM as the gas version does.
J.W.

 

[Egon]

The electric motor will produce maximum torque at zero RPM while the gas engine has it's peak torque at some higher RPM.

Starting the mixer turning will require the most torque.

Egon

 

[JATO_RaT]

Excellent point Egon! An electric motor is also really quiet. I have a 5.5 HP Honda on my mixer, I often wish it was electric whenever I'm near a power source.

 

[hazmat]

Egon hit the nail on the head.

 

[BB_TX]

I have never used a gas engine mixer, but I guess I was assuming it had some kind of clutch mechanism so that the engine was already running at rated rpm when the drum was engaged. /forums/images/graemlins/confused.gif Help educate me here.

 

[JATO_RaT]

Mine uses a gear reduction via a belt drive and then a gear from that. It will easily run the mixer at idle though. When you pull the rope, the drum turns. No clutch is really needed in this case although there are times when turning the rotating drum off without killing the engine would be handy, you know like when you get the shovel stuck in there and the handle is rotating wildly out of control taking out everything in its path. Rat

 

[Dozernut]

RaT
That one made me laugh! /forums/images/graemlins/laugh.gif Been there done that! /forums/images/graemlins/shocked.gif