Horsepower
 

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

Also, how does it compare to nitro horsepower engines?

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.

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.

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.

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.

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.

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

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.

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).

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?

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.

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

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.

FYI: At that speed, wind resistance becomes more of a factor. Unfortunately, it is quite difficult to figure that since there are so many variables. So, expect a speed a bit less than that.

Probably if you run the truck indoor with grippy floor you might achieve that speed easily.

What would I enter into that speed calculater for a revo with stock diff.s, an e-maxx tranny with stock two-speed, geared 70/12, and 70/13, and an hv6.5. Also with an hv4.5? I'm mainly concerned what to put for the diff.s and tranny, I don't know stock gear ratios, and am no good at calculating gear ratios.

There are drop-down boxes that let you select some preset values.

For the diff, just use the drop-down box and click on the Revo. It'll fill in the correct value.

Same thing for the tranny. Use the next drop-down and select the emaxx tranny. There are two entries; one for first gear, one for second gear. You probably want to pick 2nd gear. Again, it will fill in the right value.

For the spur/pinion, just enter the tooth counts in the appropriate boxes.

The same goes for the voltage. You can either type in the value, or use the two boxes and pick the values and it will do the work.

The motor drop-down has a bunch of different motors to choose from. When selected, the correct kv rating will automatically be filled in. If you know some of the kv values of the various HV motors, let me know and I'll add them to the listing.

If you make some obvious mistakes, the program will most likely let you know. I've built in error trapping and warnings when possible. BTW: if you have any ideas to make it better or more user-friendly, please let me know!

Wow, that's great. Don't remember the kv ratings right now, but I can find them and get them to you, probably tomorrow. I'm studyin' for a physics exam right now :(

The kv rating on the 6.5 is close to 4400, and is what it used to be rated, but has since been changed a little bit, and the kv rating on the 4.5 I believe is 4800. When I enter these along with 16.8 volts, it tells me that this combination is unsafe, and will result in motor overheating.

lol, tells me I'll get about 47 mph with my 6.5, and just over 50 with the 4.5. These are not accurate results for these motors :(. The 6.5 theoretically should give me just shy of 40 mph, if not dead on it, and the 4.5 in the mid 40's.

I refigured with the kv rating of the 6.5 set at 4000 kv, because I think that is close to the updated rating, and that yielded a more accurate result, about 40 mph. That still puzzles me about the 4.5 though, I saw it listed at 4800kv today.

Good luck on the test!

I told ya 60 mph was possible! :)

I certainly did not spend all the money that I spent to only go 40-45 mph. I it hits 55-60 mph I'll be happy. Over 60 mph is gravy.

With that kind of power your going to have some tire growth. Kind of like a dragster which will add a few mph. Keep us filled in on your top speed tests:018: If you need more speed and your not running hot take the pinion up a tooth or two.