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Old Mar 07, 2011, 01:02 PM
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Installing an electric motor in place of a gas engine

I have this kit that I'd like to convert to electric. I've noticed that my electric planes that the motors are all angled down and to the right of the thrust line. The kit has the firewall flat making the gas engine thrust straight. Can I mount the motor on the firewall? Should I angle it? How much of a difference will it make?

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Old Mar 07, 2011, 01:33 PM
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What kind of plane?
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Old Mar 07, 2011, 02:16 PM
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I've always mounted my electric motors at the same angle as the glow engines they've replaced. Usually this is a bit of right side and down thrust. So, if your firewall is at right angles to the model's centreline, and the instructions don't tell you to put any shims behind the engine mount, then I would mount the electric motor straight.

The good thing is you're probably going to have to space your motor off the firewall anyway, so it will be quite easy to pack one side out a bit if you find you need some side thrust after you've test-flown the model.
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Old Mar 07, 2011, 02:52 PM
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I would have written exactly what abenn wrote...
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Old Mar 07, 2011, 04:39 PM
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Originally Posted by gewiens View Post
What kind of plane?
Great Planes Trainer 40
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Old Mar 07, 2011, 04:42 PM
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Originally Posted by abenn View Post
I've always mounted my electric motors at the same angle as the glow engines they've replaced. Usually this is a bit of right side and down thrust. So, if your firewall is at right angles to the model's centreline, and the instructions don't tell you to put any shims behind the engine mount, then I would mount the electric motor straight.

The good thing is you're probably going to have to space your motor off the firewall anyway, so it will be quite easy to pack one side out a bit if you find you need some side thrust after you've test-flown the model.
The firewall isn't angled. I'll have to add spacers to get the prop to clear the cowling. So angling it won't be a problem. Just know how much will be the only issue.

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Old Mar 08, 2011, 02:32 AM
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The firewall isn't angled. I'll have to add spacers to get the prop to clear the cowling. So angling it won't be a problem. Just know how much will be the only issue. ...
If there's no data available from the instructions or this forum, then trial-and-error is the only way.

I don't think that wrong angle has ever been the direct cause of a crash -- it just gives the plane some undesirable characteristics: If you're cruising in level flight and you quickly open the throttle and the nose lifts, then you probably need to dial in a bit of downthrust. Alternatively, you back off the throttle and the nose drops before the speed does, also means you could do with a bit of downthrust. Ideally you shouldn't feed the need to adjust the elevator trim every time you change the throttle setting.

I'm not so certain about right thrust, except that first indication that you need it is often when the plane swings left during your takeoff run. After you've checked that nosewheel (if it has one) and rudder are straight, then next port of call is some right thrust.
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Old Mar 08, 2011, 07:32 PM
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Thanks for all the help. Was very informative.
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