MARCEE Minnesota Area R/C Electric Flight Enthusiasts


By Don Granlund

The following is a slide in power unit, which I use on my 1/4 Scale EAA Biplane. The advantages to using a slide in unit are.

  1. Lots of room for the batteries. This model carries 24 cells and there is lots of room to slide the batteries back and forth to balance the plane.
  2. Power unit is easy to work on. Very little wire used. Speed control is mounted by motor and is soldered directly to motor. Batteries are charged though a hatch under nose. The arming switch and fuse are tied into a wire connecting two battery packs. The arming switch is assessable though the cockpit.
  3. If you have removable cowls the unit can be moved from one plane to another with the only connection being the lead from the speed control to the receiver.
  4. The firewall and bulkheads have notches in them to accept the slide rails. Four bolts in the firewall hold it in. The mount may look weak but it is plenty strong to hold an electric motor. I made it to break in a mishap.
  5. An 18-inch prop is like a crowbar. I would rather do a little gluing then have a bent shaft.

POWER UNIT16.jpg (25582 bytes)

The pictures below are for my Zap-it

This is another Astro 40 powered plane with a slide in unit running on 20 cells. This plane is on its third year of flying and the slide in unit has held up good. Bolts in the sides of the fuselage hold in this unit. Like the unit above you only have to connect the speed control to the receiver. The rest of the power unit is contained on the slide out tray. The arming switch and charging jack are on a removable plate on the side of the cowl. The speed control is on the bottom of the tray in direct airflow coming in the cowl inlet and out though the cockpit. The motor is mounted in a rolled plywood tube in a solid balsa block. This works out good for this plane but if I wanted to put the unit in another plane I would have to use the same nose shape.

If you have any questions you can contact me at

MARCEE Minnesota Area R/C Electric Flight Enthusiasts