Saturday, February 23, 2008

Watts on the Motor List

How to rate a motor, or create a class of motors which can compete against each other on an even footing? Do you use RPM, torque, or some kind of combination of the two?

After lengthy pondering, much staring into space, and a mercifully short session of calculations, the Slot Car News Motor List has been upgraded with the power output in Watts, for every motor for which we have both RPM and torque data. Power is the product of RPM and torque. The exact formula for maximum power is given in the Intro to the list. Watts were chosen due to ease of calculation, and because they are universal units of power. All you have to do to convert Watts to Horsepower is divide Watts by 746; the most powerful motor on the List puts out a whopping 35.7 Watts, or .048 HP! That is forty-eight thousandths of a HP, a number with which you can impress your friends. It is also about half of what a normal light bulb produces. So, click on the link at the head of the page ("click here to see updates") and amuse yourself by reading numbers.

In the photo above, motors are (counter-clockwise from upper right) Slot.It Boxer 2 (FK-180), Scalextric Moto Bike (FF-050), Plafit Fox (FK-130), Slot.It V12/3 21.5k (FC-130), Fly standard "black stripe" (FC-130), Cox TTX-250 (FT-36D), and Pittman DC-195A.


Marcus said...

Good job on the Watts, Dave! Any chance of adding current draw in Amps next?

DaveKennedy said...

Hello Marcus, if you notice it's my uncle Rob Livingston that posted this. He's also the "keeper of the motor list", it's a project that he's been working on for a few years now.

thanks for checking in!

Robert Livingston said...

Current draw, hmmm....
I know people have asked for this, and it is important if you have a limited power supply. Trouble is, makers sometimes publish the amp draw at max efficiency, or at stall, or at peak power. Those are three different values. I'll look into this.

Robert Livingston said...

A look through manufacturers' and vendors' websites shows that very little amp draw info is published. An exception is Ninco, Scaleauto and Pro Slot, which label the packages or the motors. Slot.It, Scalextric, Carrera and most others do not. The majority of motors draw less than half of one amp; a few draw more, and even less draw a full amp or more, the latter mostly commercial track types, which are mostly not on the SCN Motor List.