Jam-ehz

iTrader: (6)

You can first sort out the types of silver cans.. ones with 4 small vent holes are generally faster than the newer 2 large vent holes..

Also, ones with a different "endbell" (for a lack of a better word) colour and shape.. the newer johnsons have a dark blue endbell, one older one I have has a silver endbell (probably a mabuchi), and it goes like a demon.. faster than any other silver can I've known, more like a sport-tuned..

PeteB

iTrader: (-1)

A really cheap way of "feeling" the difference is to get a large-ish prop from an RC plane, and attach it to the motor, and apply some power to the motor ** CAREFULLY ** hold the motor the motor out in front of you, so that you wont lose a finger in the prop (seriously- be careful, I had a prop spin backwards (trailing edge is the sharp side) and it vertically split my finger and fingernail half an inch down from the tip of my finger... WEAR PROTECTIVE GOGGLES!

anyway, hold it out in front of you and you should be able to feel how much power the motor has by the amount of wind genereated, very technical I know

Pete

coons88

iTrader: (1)

A cheap way I use is to just run the motors off a charged battery and listen to the pitch of the sound it makes. Whichever one makes the highest pitch sound is generally the quickest. Then to test for torque, just the motor in your hand, but with a very loose grip on it. Then plug it into the battery and see how much the motor spins in your hand. Whichever motor moves the most has the most torque.

shift

i made my own dyno. what i did was make a mount for the motor then ran a belt from that motor to another motor and it spun the other motor which creates voltage and i measure the voltage the other motor makes and and which ever has the highest voltage is the best. also i got a car speedo and hooked it up and i meseared a motor on a proper dyno at certain voltages then i was able to put numbers on and see what the rpm is. ill post a pic when i get my camera back

PeteB

iTrader: (-1)

Thats awesome, I have tried building a slave motor dyno, but couldnt really get any useful info out of it...

maybe I was measuring the out put incorrectly, I thought to measure power, using Ohms law, you multiply volts and amps. If I know the volts going into the test motor and then measure the amps being generated by the slave motor, you get power (less any losses) in the test motor. Is that right?

coons88

iTrader: (1)

Thats an awesome idea.

AUSSIE BOB

iTrader: (6)

Coons88, I did the "listen" thing, I thought my fastest was a motor, i did the "dyno" thing and then the "run in car" thing and it was number three, the motor that sounded the slowest was in fact the fastest in all forms. Just a sideline, the guy that said he had a 30,000 silver can still has not got back to me with a price

PeteB

iTrader: (-1)

Yeah, Im not sure how accurate the free rev sound will be, thats why I like the prop, it is a constant load. if you could measure the rpm of the prop, that would give more accurate results.

DerekEngland

Make a mount and use a bicycle computer.... it will give you some indication.... just not a RPM.

RocketRacer

is 19000rpm on a a 540 motor good? what type of rpm are we aiming for with this motor? what should the amp draw be at 19k rpm???

shift

what voltage are you running at

RocketRacer

7.2volts on a Team Integy Indi Dyno V2

shift

yeah i would say that is good rpm. not to sure on amp draw

RocketRacer

thanks

hav_lova

iTrader: (4)

Try 5 volts and let me know, most of my motors are 13,000+ at 5 volts and i had one that did 13,600-13,800 @5v that was a missile on the straight. Most people say my motors aren't faster then theirs on a straight but i'm usually geared around 3 teeth lower then most.