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?
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.
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!
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.
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…
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.
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).
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.
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.
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? :o
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.
If you want to take an approach looking at the overall design, however, there are several other factors you should consider:
If you should ever want to take the machine on an airplane, let’s say to go visit friends or to go to some kind of show or competition or something, no airline will ever let you take a gas-powered device with you. Even if you empty the fuel tank, the residual fuel and fumes represent a hazard that is completely unacceptable to the airlines and federal safety requirements.
On the other hand, if you’re in a place with no electricity, you’d be unable to recharge.
Electric motors are usually much quieter than gas motors–a factor your neighbors will appreciate.
Transporting, storing and using gasoline has certain health and safety risks involving toxicity, flammability, and pollution (though if you already have small gas-powered devices such as a lawnmower, you’ve already taken that step). Of course, batteries have similar problems. Which set of risks would be of greater concern to you?
Gas engines are mechanically more complex than electric, and require more complex maintenance.
You also need to figure out how the control system will work with your setup.
In summary, there are the initial design considerations (What is the most feasible design for your needs?), but there are also the long-term usage considerations (which design will be the easiest to live with over the long haul?).
By the way, I’ve seen a guy zipping along the Strand in Manhattan Beach on a gas-powered SKATEBOARD. He has a hand-held control (probably the throttle) connected to the board by some type of cable. The little fuel tank is located behind the rear truck. I’m not sure such a device is legal on the Strand, though…
Gas powered skateboards go back into the sixties. You see them in several movies of the period. I think I remember one in “On Any Sunday” a doc with Steve McQueen. I have heard that many places outlawed them since they do not have deadman switches or brakes.
Talking about gas powered motors…I guess you will probably use a small Briggs and Stratton Engine. The horsepower ratings that you see are for the engine at 3600 RPM’s. These motors will run, if in good shape with enough oil, at 3600 RPM constantly. By replacing the rod, using a shorter piston, twisting the cam, and using a 3HP flywheel and a few other assorted things you can get a 5HP Briggs motor to turn 9200 RPM running methyl alcohol racing fuel. These motors are what are run on the racing gokarts.
Anyways…thats for 4 cycle motors. You might consider using a 2 cycle weedeater motor. They can turn a lot of RPM’s and I have seen small kids gokarts, minibikes etc powered by them. They are also really hard to blow as long as you keep oil in the gas. The connecting rod rides on the small crankshaft in these motors on bearings.
If you use a gas powered motor you will also need a centrifugal clutch of some type since you cant just turn it on and off like an elecdtrical motor.
-Aaron
A car engine’s peak HP/Torque can happen low or high (depends on the application) For rock crawling and stuff that you need the most of the power lower in the band - you just change the timing/cam. I have seen engines with the most torque at about 2,000 RPMs. Now for horse power - yes you will typically need to go higher. I think that the lowest i have seen HP is at about 3,100 RPM (agian - these are for any decent hp/torque 200+ in each catagory) But for Racing applications - you wish to have a split. Torque in the low end and HP in the higher end.
For this application I’d personally like to see a diesel engine. The RPMs are kept much lower, and the torque is needed here (and lots of it.) Gas is better for speed - but diesel is best for getting off the line/heavy loads.
And for the Peak HP/Torque curve and the redline - rember you have gears in your vehicle. When you shift at your redline - you idealy will be right in the middle of your power band (from the taller gearset) - so you get the most pulling power when you shift.
) Are any of those equivalent to running 5 HP under load?
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.