Top Speed post - Page 3 - RC-Monster Forums

zeropointbug · 12.05.2006, 01:08 PM

Yah, thats true. But for how long? The efficiency goes down fast as you up the load too you know. If it were 94% effcient even at 6000 watt burst, thats 460 watts of heat from that little thing, thats more than a Pentium Prescott CPU! :026: (120watt) I know that you can get more out of the rating of a brushless motor. The 300 watts output (14.4v) is the absolute PEAK for the 820 motor, I was running 16.5 volts so power would somewhere around 700-775 watts (duals). I guess these motors just handle a higher continuous output than other motors, it wasn't shy of 50mph thats for sure.

Serum · 12.05.2006, 01:16 PM

well, the point was 6400 watts vs the 1800 watt rated. the efficiency might look high, but for the size it's hard to desipate 400+ watts of heat. But it's measured and proven to do so. For a few seconds it's okay, which is okay to set a speed record, agree?

600-700 watts on an mt is not enough to get it to 50 mph. (trust me on this one, i know it's hard for you) so it must have been pushing out more, or the speed must have been lower than 50 mph.

But what about the heat coming from your dewalts? 700 watts output, at 60 percent eff. that's a good 235 watts per motor too.

coolhandcountry · 12.05.2006, 01:19 PM

How can you say that you was pulling that many watts?
Did you have the same load as the motors was tested with?
You say 16.5 volts as well. Is that the battery voltage under load or rated at?
A titan goes way up in watts as well. It is only rated like 175 but can draw much more.

zeropointbug · 12.05.2006, 01:21 PM

6400 watts, ya i would say is good for a speed run, thats hellishly fast what ever you put it in...

The Dewalt's have fans like the titans, only alot bigger and they blow like a MOTHER, you could cool down a family of 5 with the wind coming off it. WEll, if you SAY ~750 watts isnt enough to get to 50mph, then it must have been pushing out a little more. They rate the truck will go 45mph easy with them, thats at 14.4v.

lydiasdad · 03:56 PM

Thought I'd ad my two cents. I used to run one dewalt 820 on 18 cells in my maxx. It was very impressive, mid 40's easy. I now run a 9xl on 18 cells. It wasn't that big a difference in performance but my run time is about 5 minutes longer. People under-estimate the 820's power. The dewalts are about 80% efficient, on 18 cells that's about 1400 watts. Kershaw over-gears his setups also, so don't go by his results. If used correctly the dewalts are great motors. I still run one in my jugg 2 with a super duty and 14 cells. I would put it up against the hv maxx any day.

coolhandcountry · 12.05.2006, 08:02 PM

It is not so much the dewalt motors. It is the amount of watts claimed to
draw verses the amount it is accually drawing. You admit that your system
was in the 1400 watts range. Not 775 or so. You said mid 40s the other says 50.

lydiasdad · 12.05.2006, 08:16 PM

I am not zeropointbug. I can not speak to his claims. I was talking about my experiences.

smhertzog · 12.05.2006, 08:38 PM

With 66 spur and 22 pinion 4s lipos on a 7xl my truck does 40mph
The same setup on 6s did 50mph but it was over the limits of the motor and was only done for a couple runs. Not to mention the fact it was extremely hard to control.
I got my speeds from a bushnell radar gun.
When I checked it out on Brian Gs' speed calculator it was very close. I guess I could have saved $79 and just trusted his calculations but were is the fun in that?

coolhandcountry · 12.05.2006, 08:43 PM

Quote:

Originally Posted by lydiasdad

I am not zeropointbug. I can not speak to his claims. I was talking about my experiences.

Your story adds up. I say yes it is very possible. I just have questions on other. Either it ran 50 on more wattage or less on 775 watts. :002:
Anything is possible though.

zeropointbug · 12.05.2006, 09:23 PM

Coolhandcountry You say the titan is rated for 175 watts? On Kershaw Designs he says the Titan puts out 129 watts on 14.4 volts. That might explain why i am able to get to 50 mph on "750watts", so maybe the dewalt setup is putting out something more like 1100 watts or more? Maybe his testing rig is messed, or he just doesn't know what he is doing...
Also, he says 80% peak efficiency, but i don't know what power output that is at? (seems reasonable)

And ppl DO under estimate the 820 motors, they capable of very high power. Apparently you can run them on 18 cells no problem. "600 watts" from one motor... in his watt ratings.

12.05.2006, 10:53 PM

My TC3 went 58.1 mph on 4s 4000mah lipos and a mamba max 4600 system. This was verified with a gps ziptied to the battery strap. It had a lot more speed left in it, I hadnt even touched full throttle yet when I hit a bump, caught air under the body, and took flight. It was geared 25/69 at the time, next time Im going to try something taller, 30/69 or so. And Im hoping to find a bigger, smoother lot to run on.