magnet question

[Buffalo Kid]

Monty,

In a 16D, or any motor, how does airgap affect torque? Also how does timing affect torque? I can build a decent motor but i want to know how certain components affect torque/ top end. Also how does track power affect torque/rpms? High and low voltage? Do you find there is an ideal range for airgaps on certain track voltage readings (Ex. .565 on 14 volts)? Also, do you find one magnet (PSE or FO) is faster on high/low power tracks?

Axle

[JPKART67]

One factor in tourque are the springs. A spring with more tension will result in more tourque. I put Champion heavy springs on a stock flexi 1 and was spinnin the wheels off the line. Also yes the air gap has been known to give more tourque.

[Dan P]

to JPkart and everybody -

PLEASE let Monty have first crack at the questions!:)

I realize that can be pretty hard when you know the answer and the question has been sitting here for a while but after all, the title of this forum is "Ask Monty Ohren"!!!

[[email protected].]

BK,
Sorry for the delay. I went racin' this weekend. Then I had a login problem and lost my lengthy response somewhere in cyberspace.

I have never liked tight airgaps. While they may allow SLIGHTLY more torque, the cost in RPM and poor cooling makes for a slower all around package. Please note that the USRA minimum magnet gap is .575", so I've never even tried a .565" hole.

Electric power is measured in Watts, the product of current and voltage. Therefore, if you increase EITHER, you can realize increases in power, the product of both torque and RPM. This can require fiddling with gears, however, and a voltage increase is more readily identifiable with an increase in RPM. High RPM motors cool better, and due to better gyroscopic action also lead to improved handeling. This is why I'm not excited about the large dia. RJR/FO arms yet, but I'm willing to change my tune when I see some results.

The FastOnes DM II magnets seem to be identical to the Parma EPX magnets, so no I don't reccommend one over another for specific applications. In general, you want stronger magnets for higher power, and matched magnets for all applications.

[JPKART67]

that's okay, fair and understandable, but then in that case give me my own forum! lol

[Neal Stewart]

also, the amount of amps the track gives out (if you are running on power supplies) and the amount of amps the motor draws.

[Buffalo Kid]

thanks monty

[Dan P]

Monty, doesn't bringing the magnet closer to the arm, in effect, increase the strength of the magnet?
I understand your point about a larger gap running cooler (more air!) but theoretically, isn't a weaker magnet made stronger by decreasing the gap, or are there other factors (such as the shape of the field, or whatever) that come into play?

I hope you understand what I'm asking, I just re-read my question and it sounds a bit confusing!!!:confused:

To put it another way, let's say you could measure the strength of the field right at the surface of the armature.
Motor #1 has super strong magnets very far from the arm, and the gauss reading at the arm surface is x.

Motor #2 has weak magnets very close to the arm, and the gauss at the arm is ALSO x (the same).

Disregarding cooling effects, will these two setups have the same magnetic properties? (WHEW!!!;) )

[Buffalo Kid]

Dan,

bringing the magnet closer to the arm doesnt change the magnets themselves but increases the magnetic field making the motor faster.

[[email protected].]

BK,
You were doing fine there until your last 4 words "making the motor faster". In my experience, the motor is often SLOWER after you increase the field, especially in this way.

Stronger magnets MAY make the motor faster, IF the track power is sufficient. Thats all debateable.

Making a stronger field by running a smaller gap, however, makes the motor work harder by increasing the parisitic drag of air on the armature. This is not an inconsequential effect, as it increases with the square of the armature's rotational speed. This drag is also directly proportional to the airgap - you can move twice the air if you have twice the space - whereas the magnetic field is only increased by a small amount when you cut the airgap from say, .010" (approx. .535" hole) to .005" (.525' hole. Remember that the magnet is .150" thick, so its center of mass is .075" deep inside. Your .005" reduction in gap moves the magnet a whole 7% closer ovedrall, not 50%!

Dan, this won't answer your question altogether, but you can see where I'm going. You might get a hypothetical pair of setups as you describe, with reduced airgap making up for reduced magnet strength, but it still isn't the same thing.

As I see it, in a C can, the inside dia. is at least .835" - unless you never straighten the can - and the total magnet thickness is .300". The gap is going to be around .535" unless you are wasting space between the magnets and the can, where the field strength is also affected by proximity.

[Dan P]

I never even THOUGHT about the parasitic drag effect being increased by a tight air gap! DUH!!!:rolleyes:

One more question, I know more track power allows more magnet, but how about hotter winds vs weak ones?

Can a 12 arm handle more magnet than a challenger?

[[email protected].]

YES. Hotter winds demand more field.