discussion Fitting small electric motors to a B29

[Guest]

Hi All

Ive got a 1/48 B29 Superfortress & Ive bought 4 Airfix electric motors (£12.00 from Amazon) to turn the propellors. Has anyone done this before, where did you run the wires to keep them concealed but still be accessible, how did you fit the motors?

Thanks

Tess

 

[Guest]

I've used these motors in the Airfix kits but never adapted anything else. You are obviously going to have to make a bulkhead which will fit in the engine nacelle which you can mount the motor to. As the motor is going to be sealed into this for life you may as well glue the motor to the bulkhead, if it fails in the future you will have a dead engine and three still working. You will also have to drill an appropriate sized hole in the back of the propeller boss which you will have to do with great care to ensure that the hole is concentric. If not the propeller will spin off centre and look very unrealistic. The wires can be led back through the aft of the nacelles then along inside the wings and exit the wing roots. You will have to extend the wires so I would go for a soldered connection, which can be sealed with glue or heat shrink. I would use old telephone cable for this as it is nice and thin, pliable but single core so it is easy to bend it to go where you want it.

You then have to make a big decision, do you want to hide the batteries inside the model, in which case you will need to incorporate a removeable panel somewhere, or do you want to put the batteries outside the model, in which case you will need to run the cables outside and somehow hide them. The Airfix kits have the batteries in the stand and the cables run through the stand connection below the fuselage but putting a 1/48th B29 on a stand might be a bit of a challenge!

You will need to wire the motors in parallel, not series, otherwise they will share the voltage and run quite slowly. You don't actually need a switch with these motors as they start when you spin them but that still leaves the batteries in the circuit even when the motors are not turning so I would still recomend that you fit a switch somewhere.

 

[tr1ckey66]

Hi Tess

I've done exactly what you're attempting with the Revell 1/48 Memphis Belle B17. I didn't use airfix motors as they proved a bit too large for the engine nacelles but providing they fit in the B29 it will be fine.

Essentially what you do is wire a series circuit, to do this:

1. Run a twin wire up through the tail wheel opening and along the fuselage to the wings

2. Split the wire here and run one end to the furthest engine on the left and one to the furthest engine on the right. Do this before joining the fuselage halves and the wing halves and after the engines have been securely mounted in the wing bottom halves. Ensure the engines are mounted correctly and are true or the props will fowl against the nacelle sides.

3. Daisy chain the engines on the left and then pass a wire through the fuselage to daisy chain the engines on the right (see diagram)

4. Glue the wing halves together, then glue the fuselage (do this on a wide flat area as the connecting wires will mean plenty of things to support!)

5. Glue the wings to the fuselage feeding in the wire slack into the fuselage as you go (ensure nothing is snagged).

6. Connect the 2 wires at the tail wheel end to a battery and your Super Fortress should spark into life!

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Things to note:

1. Solder all the joints

2. Expose as little bare wire as possible to get the job done - this will cut down the risk of a short circuit

3. ensure the engines are mounted properly centred through the prop shafts

Have fun with the B29 and good luck!

Paul

Ps. Sorry, I forgot to mention I mounted the engines first pressed into putty to get the alignment correct. Once hardened secured the lot with epoxy resin (ensuring non of this goo went into the engines themselves which would obviously prevent them from working).

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