Horsepower - RC-Monster Forums

vette1 · **Horsepower -** 10.17.2006, 11:36 PM

Does anybody know how to calculate horsepower on an electric brushless motor with lipos?

Also, how does it compare to nitro horsepower engines?

mwe-maxxowner · 10.17.2006, 11:53 PM

I think it's like 746 watts equals one hp, but someone clarify, i can't remember exactly, I can find it though. If no one gets it soon.

BP-Revo · 10.18.2006, 12:09 AM

Yea, its about 750w or so to 1 HP.

Well, you have to realize that the HP rating are very different.

A nitro motor gains HP as the RPM's increase, the HP reaches a peak, then drops off as it gets into its overrev.

An electric motor starts at peak HP and Torque, and as the RPM's increase, it loses power, but gains efficiency. Eventually, the efficiency peaks and dorps off as well.

However, in general, the electric motor will have more power than the nitro one. So, for example, an electric and nitro motor and engine, respectively, which both put out 1hp, the electric will be faster.

vette1 · 07:30 AM

If 750 Watts equals 1hp, how do I calculate the watts that the motor, esc and the batts put out? :032:

bk20150
lehner 1950/6 hi amp
2 batts 3s 8000mah max amps 11.1volts each

putting them in series will give me 22.2 volts total.

cart213 · 10.18.2006, 12:36 PM

Quote:

Originally Posted by BP-Revo

An electric motor starts at peak HP and Torque, and as the RPM's increase, it loses power, but gains efficiency. Eventually, the efficiency peaks and dorps off as well.

Actually, an electric motor starts at peak torque and zero HP. HP is a product of torque and rpm, so HP is zero when the rpm is zero. Torque will drop as the rpm rises, but HP will rise until the drop in torque exceeds the rise in rpm. That is where the peak HP will be.

MetalMan · 10.18.2006, 09:05 AM

You can roughly base the power output of the system by what the batteries can do. If you assume 85% efficiency, then multiply the power of the batteries times 0.85 to determine roughly how much power your system can put out.
In your case, the batteries can do ~2200watts (estimate), so the power output is (roughly) 1900watts, about 2.5 HP.

vette1 · 10.18.2006, 01:17 PM

Quote:

Originally Posted by MetalMan

You can roughly base the power output of the system by what the batteries can do. If you assume 85% efficiency, then multiply the power of the batteries times 0.85 to determine roughly how much power your system can put out.
In your case, the batteries can do ~2200watts (estimate), so the power output is (roughly) 1900watts, about 2.5 HP.

How does this 2.5hp compare to the traxxas 3.3 revo?
And how much speed do you think I will achieve?

cart213 · 10.18.2006, 01:46 PM

A Revo with a 1950/6 on 6s lipo will blow the doors off a 3.3 Revo. The nitro can do 45+ mph as claimed by Traxxas, but yours should be capable of 60 mph with quicker acceleration and more torque as well, imo.

vette1 · 10.18.2006, 02:38 PM

Quote:

Originally Posted by cart213

A Revo with a 1950/6 on 6s lipo will blow the doors off a 3.3 Revo. The nitro can do 45+ mph as claimed by Traxxas, but yours should be capable of 60 mph with quicker acceleration and more torque as well, imo.

I'm glad you think so but does anybody have any proof of it.

squeeforever · 10.18.2006, 04:09 PM

I know so...There is NO question. Its almost common sense really...I had a 3.3 and it was somewhat fast, but it took over 100 feet to get to top speed. A BL truck can get there as fast as you want. It's just a matter of keeping the front end down...

MetalMan · 10.18.2006, 04:46 PM

Quote:

Originally Posted by squeeforever

I know so...There is NO question. Its almost common sense really...I had a 3.3 and it was somewhat fast, but it took over 100 feet to get to top speed. A BL truck can get there as fast as you want. It's just a matter of keeping the front end down...

... and getting traction (if you aren't wheelie-ing already).

vette1 · 10.18.2006, 06:00 PM

Quote:

Originally Posted by squeeforever

I know so...There is NO question. Its almost common sense really...I had a 3.3 and it was somewhat fast, but it took over 100 feet to get to top speed. A BL truck can get there as fast as you want. It's just a matter of keeping the front end down...

If you look at the photos you can see that the wheelie bar is set low and I configured the suspension to limit the amount of life from the front. I hit the pedal and the truck pushes back a little and then it squats down on all four wheels and just goes.

But my main question is how fast top speed will be with the setup i have based on the 2.5 hp that everyone configured for me?

cart213 · 10.18.2006, 06:36 PM

With a high-powered setup like yours, speed is mostly a matter of gearing.

Do a search on the forum for BrianG's speed calculator. It is a spreadsheet where you enter stuff like motor type, voltage, gearing, and tire size. It will compute an estimated top speed for you.

BrianG · 10.18.2006, 08:14 PM

I'll make it easy for you. Speed Calculator :)

vette1 · 10.18.2006, 08:35 PM

I just checked it and it came out to me 61 mph.

If I achieve that I will be very happy.

I bought the radar gun so once I get the batts from Mike I'll let you guys know.