reinforce the motor mount on Firebird/Aerobird


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reinforce the motor mount on Firebird/Aerobird

Postby aeajr » Sun Apr 20, 2003 11:23 pm

I fly an Aerobird, which is the top of the line in the Firebird Series from
HobbyZone. From what I read, all the planes in the series are fun. I have also
had great experience with the HobbyZone support folks. So read this as a happy
flyer who wants to make these fun planes even better.

There is one weakness in the series that is easily fixed. The motor mount is
weak. A hard hit into the ground or a tree can shift the motor, or disloge it
completely, as it did on mine. :( But, with a small modification, this weakenss
can be corrected and you can enjoy lots of fun flights with these "birds" Read
my post and see what you can do to prevent this from happening to your "bird".

There are also other planes that have similar bodies. Planes like the e-gull,
the vector and the t-hawk, just to name a few. They may benefit from this
modification as well.

What Happened?

Last week my Aerobird took a good shot in a nose first, landing causing
the motor to break free of its mounting and shift forward inside the plane. :x I
have since learned that this is not uncommon. Also, while mine was dramatic,
if it is only a small displacement, you might not notice it, but the motor can
get out of the proper thrust line causing the plane to fly to one side or the

After some experimentation and excellent advice from other threads, I have
begun to rebuild the Aerobird and repair the damage done by the forward
shifted motor. There is a link to photos below.

What some other people have done:

Several people created some kind of plate to put behind the motor, inside the
body. This can work, but I think this is difficult to do correctly and may
require you to dismantle the plane. I think it could also reduce cooling air
flow within the plane.

Others replaced the little oval metal piece "washer" that sits below the prop
and holds the motor. They replaced it with a larger plate made of plywood or
metal so that it covered the whole motor mount area. This would prevent a pull
through and reduce the likelihood of the motor shifting left or right. This is
easy and will provide reinforcement, but I don't think it is enough.

Here is what I did.

I drilled two holes on either side of the body, right behind the motor and put
a nylon tie wrap there. This holds the body tight to the motor AND blocks the
motor from shifting backward. I did this as part of my repair, but you can do
it now, before a repair is needed.

The holes are 1/2" apart, centered on the motor. I used an 8" tie wrap, but a
6" wrap would probably be better as they are a little less bulky. You want
the tie wrap to either sit against the motor or sit barely behind it so that,
under stress, the wrap stops the motor from shifting which will either distort
the motor mount area or pull it through all together.

Here are pictures of the damage I incurred and the repair. ... 384c03a4f9

(A tip on viewing the photos. Select view pictures. It takes you to a slide
show. In the upper right is a stop button. The photos will flip on their own
if you don't stop them.)

The photos show a yellow tie wrap, but that was just for pictures. I cut this
out and replaced it with an orange one that looks much better on the plane. I
got the wraps from Home Depot, but Radio Shack has orange tie wraps as well.

After putting this tie wrap in place, there was no longer a need to put any
kind of bracing plate by the prop area. This tie wrap really holds the motor
solidly AND prevents it from moving forward.

Recommendation to all Firebird, Firebird XL, Fighterbird and Aerobird flyers
and those with similar fuselage planes:

I love the Aerobird and think the whole "bird" series is fine. However a weak
motor mount exists in all the planes. I would recommend this modification be
done on ALL new "birds" BEFORE the motor mount is challenged and repairs have
to be done. If the motor shifts far enough, it will hit the control board and
wipe out all of the electronics. If it only shifts a little, the plane flies
badly, commonly to the left or right and can't be trimmed properly.

You can do the drilling and insertion of the tie wrap without having to take
the guts out of the plane. Just be careful to limit how far the drill bit goes
inside the plane. There is enough room to do this, just be careful.

When you put the tie wrap in, make sure it slips UNDER the noise suppression
components that are soldered between the motor terminals. You can see them in
the photo. A 6" tie wrap is not as wide as the 8" wrap I used, so it will fit
more easily with less displacement of the components, however I believe that
it will be strong enough to get the job done.

Don't over tighten the tie wrap. Just make it snug, don't distort the body of
the plane. If you are skilled and have some very long nose pliers, you can
probably hide the square head of the tie wrap inside the plane so it looks

I plan to send a note to the manufacturer and advise that this should be done
at the factory. Don't get me wrong, I like these planes, but they have a weak
motor mount. This will take care of the problem before it becomes a problem.

I hope you find this post and the photos useful. Thanks to everyone for their
advice and tips.

Don't wait, do this mod now on your Firebird, XL, Fighterbird or your
Aerobird. Do it now, before you need it and you will have a much longer,
happier relationship with your "bird". :P
Best regards,
Junior Member
Posts: 17
Joined: Mon Apr 07, 2003 8:05 pm
Location: LI, NY, USA

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