RC_Fanatic

My Feedback: (1)

Found an electric motor with a folding prop in my "treasure" box. It is a Graupner "Jumbo 550 F G3" It says "9V" on the label so I assume it is designed for an 8-cell battery. It has a gearbox which appears to be 3:1. Prop is ~14" diameter but I can't see any markings that would indicate the pitch. What size of glider would be appropriate for this motor? Wingspan? Weight? I'm looking for something for thermal flying at our club field (~ sea level). Would it fly a Windrifter or Butterfly (100" span)?

Tall Paul

Those motor/gearbox combinations usually work well with 8-cells and 12 to 13 inch props.
A 100 inch plane would the largest practical size.. a 2M would have more pleasing performance.

RC_Fanatic

My Feedback: (1)

Thanks. Any suggestions for a 2m kit? I'd prefer something with ailerons.

Tall Paul

The GP Spirit Elite comes to mind for a reasonably priced easy to build aileron and flap 2M.
Adding the motor is simple.
I've done that to both the Spirit and Spirit Elite.. The SE I made w/o ailerons and flaps, just rudder-elevator-motor.

RC_Fanatic

My Feedback: (1)

Thanks for the tip, and for the photos, especially the fuselage layout. I have a Spirit Elite ARF (glass fuselage) in the closet. I could use the wing from that and build a balsa fuselage and tail for the electric. What size ESC would I need for this motor? I'd thought of just using a servo-activated switch as I only expect to be full on or full off, but the ESC may have some advantage. Where do you get the spinner that goes over the hub for the folding prop? TIA

Tall Paul

Look for a 30 amp ESC, with BEC.
The spinner is a standard 2" DuBro, hogged out with a router bit in a Dremel.

RC_Fanatic

My Feedback: (1)

How is the spinner fastened to the motor shaft? On my gearbox, the shaft is much smaller than the hole in the spinner backplates that I have. Do I need to machine some kind of adapter?

Tall Paul

There's an infinite number (it seems) of adapters for motor-shaft to prop hole available. The MA gearbox usually takes a 1/8" diameter to 1/4" diameter adapter.
And the spinners come with slide-in bushing to accept 4 different sizes of prop shaft.
When worst comes to worst, I use nesting brass tubing to build up a bushing for the motor-shaft to prop shaft fit.
It seems that no matter how many adapaters I have on hand, the one I need I don't have.

csasopwith

swap the motor for a bungy