Irvine Electric Cobalt Motor

[George West]

information required regarding the above motor,  on the motor body is a small yellow label with this info, 05 Cobalt 10 turn, on the main label there are graduations +l 2 1 0 1 2 R-. What i require is the following,

1  Size of motor

 2 working voltage

3  size of model it will fly

4  what are the graduations for

5  or a copy of the information leaflet that would come with the motor 

[Alistair Taylor]

Hi George

The 05 cobalts were pretty generic, being marketed by Ripmax, Promax and others.

 Here's an instruction sheet for the Promax motors with the information on voltage/watts:

http://www.maxxprod.com/pdf/PMXxx.pdf

NB I think the 05 10-turn Promax motors were referred to as "1510" motors.

The info supplied suggests that you use this motor on 12 volts to spin a 7x6 prop at 13,700.

This would be fine for a small, slippery fast model (60" span, speed 500 - 600 model), but given the low Kv of this motor (1284), you might be better off using a bigger prop on fewer cells.

I've been using a 7-turn ripmax 05 cobalt to turn a 9x5 prop on 7 - 8 cells in a 72" (speed 600 type) electric glider and it works well. You might get good results with a 10x6 prop on 7 - 8 cells with the 10-turn motor in a similar model.

The marks and graduations on the case of the motor are timing marks. If you have the time and patience, they are there to help you set the timing of your motor

If you loosen the case screws you can rotate the brushes and vary the timing of the motor, according to your setup (tractor or pusher) and particular preference for duration and efficiency, or speed and power.

The motors come from the factory set to rotate in the "normal" direction (i.e. correct for a tractor installation), and at appraoximately a 50/50 compromise between power and duration.

Rotating the brushes one way (I forget which) will reduce current consumption and rpm, and give you more efficiency. Rotating the brushes the other way will give greater current consumption and more rpm, and less efficiency (I believe that the relationship is non-linear). The "best" position will depend on the prop, the cells, the plane, and your preferences.

Suffice to say I haven't touched the timing on mine. If you do plan to experiment, mark the starting position with care so that you can return to it when you become disillusioned.

Oh - and use an ammeter before committing the motor to flight. Heat kills cobalt magnets.

 AlistairT

[George West]

Hello Alistair, many thanks for your reply, not sure what i am going to use the motor for but i have now got the info i required.

many thanks george

[George West]

something i should have thought of, what kind of aircraft weight will it lift.

George 

[Alistair Taylor]

There's a rule of thumb on "watts per pound" such that with one of these cobalts, pulling 20 - 30 amps on 9.6V, you're probably looking at a model between 1.5 to 5lbs

The 1.5 lb model will be blistering (if you've got the right prop and wing section), the 5lb model will fly... but wont set your pants on fire.

These values are very approx, see;

http://www.csd.net/~cgadd/eflight/calcs_gloconvert.htm

HTH

Alistair

PS - Might be an idea to weigh your battery packs first to give you a baseline, unless you're cabable of building 2oz airframes that can stand 300 watts....