Motor Things

[Paul]

A few rookie questions about electric engines and speed controllers. The
truck I'm looking at has a mechanical SC model and an ESC model, a $20
difference. I've read that electronic controllers are better than
mechanical. Why? What does that $20 buy me? What makes one ESC better than
another?

I hear the term 'turns' used to describe engines. What are turns? Are more
or less turns better? Apparently some engines are more efficient than
others. Is there a metric to describe efficiency? I assume some engines are
more powerful than others, and some use more power than others. Are there
metrics for these properties?

Is there any website that has this kind of basic engine info?

Thanks, Paul

[kenji]

In article <vf9g0olio35ue3@corp.supernews.com>,
"Paul" <paulben@concentric.net> wrote:

> A few rookie questions about electric engines and speed controllers. The
> truck I'm looking at has a mechanical SC model and an ESC model, a $20
> difference. I've read that electronic controllers are better than
> mechanical. Why? What does that $20 buy me? What makes one ESC better than
> another?

http://www.gettingstartedinrc.com/cars/page3.asp

about the third or forth paragraph down.
>
> I hear the term 'turns' used to describe engines. What are turns? Are more
> or less turns better? Apparently some engines are more efficient than
> others. Is there a metric to describe efficiency? I assume some engines are
> more powerful than others, and some use more power than others. Are there
> metrics for these properties?
>
> Is there any website that has this kind of basic engine info?

Electric uses motors. Nitro (gas powered) use engines.....check this out:

http://rcvehicles.about.com/library/mph/blmotor.htm

[Rick Russell]

In article <vf9g0olio35ue3@corp.supernews.com>,
Paul <paulben@concentric.net> wrote:
> A few rookie questions about electric engines and speed controllers. The
> truck I'm looking at has a mechanical SC model and an ESC model, a $20
> difference. I've read that electronic controllers are better than
> mechanical. Why? What does that $20 buy me? What makes one ESC better than
> another?

Mechanical speed controllers work by routing the electricity through a
resistor, burning off extra energy as heat and slowing the car
down. For anything less than full throttle, they are not very
efficient. Also, many of them use a three-position rotary switch to
select the amount of resistance, so you only get three forward speeds.

ESCs use electronic switching to shut the power on and off very
rapidly. They generate less heat than MSCs, and are more
efficient. Also, they provide a smooth range of forward speeds --
usually at least 32.

> I hear the term 'turns' used to describe engines. What are turns?
> Are more

The number of turns is the number of times that wire is looped around
the armature stacks. Fewer turns means more top speed and more total
power draw. Typical off-road racing motors have between 10 and 19
turns. Stock motors have 27 turns.

> or less turns better? Apparently some engines are more efficient than
> others. Is there a metric to describe efficiency? I assume some engines are

Yes, it's called "efficiency" :-) It's the ratio of mechanical power
to electrical power. At peak efficiency, most motors fall between 65%
and 80%.

> more powerful than others, and some use more power than others. Are there
> metrics for these properties?

Yes, "power" :-) Power is often expressed in watts, although sometimes
you'll see current draw (in amps) used as an analogue for power. As
long as everybody uses six cells (7.2V), current and power are
proportional.

Rick R.