Gas powered engine horsepower equivalent to electrical motor horsepower?

[Elgin Clock]

Quick question for anyone who would like to respond.

Is there a way to equivalent Gas Engine Horsepower to Electrical motor power?
Are Electric motors rated in Horsepower??

Say a person wanted to replace a gas scooter motor (5HP) with an electric motor? Could this be done efficiently? What else do I need to know to accomplish this?


I already have a way to (theoretically) hook the original chain drive to the motor, just need to know what kind of motor I can use to make 5 hp.
(Maybe one of the motors from the kit? ) Are any of those equivalent to running 5 HP under load?

[Andy Baker]

Originally Posted by Elgin Clock

Is there a way to equivalent Gas Engine Horsepower to Electrical motor power?
Are Electric motors rated in Horsepower??

Elgin,

Electric motors are rated in various ways. I've seen them rated in HP, oz-in, Watts and KWatts. Looking at the back cover of my Machinery's Handbook, it says that there are 745.7 Watts for 1 HP, if that helps you.

Andy B.

[greencactus3]

Originally Posted by Elgin Clock

Say a person wanted to replace a gas scooter motor (5HP) with an electric motor? Could this be done efficiently? What else do I need to know to accomplish this?


I already have a way to (theoretically) hook the original chain drive to the motor, just need to know what kind of motor I can use to make 5 hp.
(Maybe one of the motors from the kit? ) Are any of those equivalent to running 5 HP under load?

well, yes you can replace the engine with a motor, but since gas and electric have very different torque curves, they will perform very differently. ex) electric will probably accelerate faster... in battlebots and such they say some of the robots' spinny things spin with one 10 hp or more motors. im sure sumone sells them!

[sanddrag]

Maybe you need one of these or these. However, by the time you get batteries and electronics, I think the greatly increased cost and weight show that the gasoline engine is the better choice.

[greencactus3]

wow...... Stall torque:38500 ozf·in or 34.3hp @72V.... wow...
and stall current at 4 digits??? if only the price were a bit lower....
near the top end of 3 digits is kinda high up...

[EricS-Team180]

If you have a golf cart dealership in your area, you might want to stop by and talk with a mechanic. They may be able to offer some insight on a conversion.

Eric

[MattK]

just figured I would toss this info in-

The segway has two 2 horsepower motors. They are 3 inches in diameter (I think).

The segway also gets the equivalent of 460mpg

[greencactus3]

Originally Posted by MattK

The segway also gets the equivalent of 460mpg

how do you calculate that?

[Elgin Clock]

Originally Posted by sanddrag

Maybe you need one of these or these. However, by the time you get batteries and electronics, I think the greatly increased cost and weight show that the gasoline engine is the better choice.

I was kind of hoping to buy some kit motors from my team cheaply and use those. But.. if this just won't work with the kit motors, then I may just say the heck with it and make it gas powered.
:sigh:

That's what I get for trying something that's never been done before (as far as I have seen).

Maybe there is a reason for that..

[MattK]

Segway did- I would imagine one way would be to take the price you paid to charge your segway and compare it to the price of gas.

I am not sure how they came to that number but I have seen that number and number in the 200's come out of segway.

Originally Posted by greencactus3

how do you calculate that?

[MattK]

We put the big black motors on a scooter and it really didnt go very fast... you also had to push off when you started to go.

Originally Posted by Elgin Clock

I was kind of hoping to buy some kit motors from my team cheaply and use those. But.. if this just won't work with the kit motors, then I may just say the heck with it and make it gas powered.
:sigh:

That's what I get for trying something that's never been done before (as far as I have seen).

Maybe there is a reason for that..

[patrickrd]

Originally Posted by Elgin Clock

Is there a way to equivalent Gas Engine Horsepower to Electrical motor power?

I'm not sure about this, but I imagine gas engine horsepower is the output power of the engine. To compare to an electric motor, you need to look at the output power of the motor. Some motors have power ratings but I always look at the stall torque and free speed. Take half of each, and multiply together to get the power of the motor (N*m x rad/sec = Watts). This is the point where the motor is creating the most mechanical power it can possibly produce at the rated voltage. Then you can convert the watts to horsepower (google search "unit conversion" with "i'm feeling lucky"). This is probably as good of a comparison you will get.

You also need to keep in mind that engines and electric motors work very differently. If you use an electric motor at peak output power, it is not most efficient! In fact you are converting a lot of the power to heat at that point. Depending on the thermal limits of the motor, you may burn out the motor if you run at this point for a given amount of time. I don't know how long you can run an engine at peak horsepower? Maybe someone knows.

[Adam Y.]

You also need to keep in mind that engines and electric motors work very differently. If you use an electric motor at peak output power, it is not most efficient! In fact you are converting a lot of the power to heat at that point. Depending on the thermal limits of the motor, you may burn out the motor if you run at this point for a given amount of time. I don't know how long you can run an engine at peak horsepower? Maybe someone knows.

Actually I would worry more about when the motor is stalled. That's when the motor reaches 0 efficiency.

I already have a way to (theoretically) hook the original chain drive to the motor, just need to know what kind of motor I can use to make 5 hp.

Wowser none of the motors in the FIRST kit come even close to 5hp. Even the EV warrior motor which is designed to move humans is only rated at .5hp.http://www.robotcombat.com/marketplace_ev.html

We put the big black motors on a scooter and it really didnt go very fast... you also had to push off when you started to go.

Those big black motors were designed to move a six year old.

[greencactus3]

Originally Posted by patrickrd

I don't know how long you can run an engine at peak horsepower? Maybe someone knows.

as long as you keep the block from overheating and have decent lubrication( i guess thats part of the overheating prevention) and dont run out of gas, quite a long time.... for example, car engine's peak output rpm is around 4000~6000 rpm. i think... not diesel, gasoline... and not rotary engines either, which tend to have lower rpm peak power. car engine's redlines are a bit higher than the peak, so well,,, im confusing myself again.... help?

[Al Skierkiewicz]

Elgin,
Watts is Watts therefore horsepower is horsepower. All motors have different power/torque/RPM curves as they are all designed for different duty. In the operation you are considering, gas power is easier to implement and that is why most designs use that type of engine. There is no control issues other than throttle and no recharge issues other fill the tank. The need to design for output RPM and torque still exists and that is why the transmission is in place. A five horsepower electric motor is not a little toy and the power source is not a little battery. All things considered, the gas powered approach is still the best over all design.