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Old Oct 08, 2012, 09:41 PM
Registered User
Joined Jan 2008
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Engine mounting via tape or rubber bands?

Hello,

Iím a novice scratch builder. Iíve built 4 or 5 flyable foamies at this point. My flying skills are novice as well.

Following a bad crash Iíve often noted that the engine/firewall has either torn off or the firewall/fuselage junction has been badly damaged.

Iím currently building a delta wing pusher and while working on the CG had just taped the engine/firewall to the rear fuselage mounting point temporarily .

With not much tape it felt surprisingly secure.

That caused me to wonder if anybody ever used tape as the only attachment method.

Also: What about ďrubber bandingĒ the motor to the fuselage similar to the way a wing might be mounted?

I thought that either technique might provide a bit of give the next time I make more of an impact while landing than I had intended, ha, ha.

Is there any experience using either technique?

Thanks!
Don.
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Old Oct 08, 2012, 09:56 PM
Do a Barrel Roll!
rcbif's Avatar
United States, OH, Medina
Joined Jun 2005
1,021 Posts
It's all about distributing force. The more area the motor mount is distributed over, the less likely it will be to damage the surrounding foam. You can increase your motors surface mount area using thin plywood, or a material stronger than the foam you use.

It's hard to see, but here is my delta. The motor is mounted to the end of a simple stick mount, and that is attached to a 2inx4in 1/8in piece of plywood glued to the main foam airframe. Very unlikely to come off in a crash.

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Old Oct 08, 2012, 10:12 PM
"Fly, yes... Land, No"
OutcastZeroOne's Avatar
United States, CA, Santa Cruz
Joined May 2005
1,328 Posts
properly securing a motor mount can have as much to do with the design of the aircraft as the shape and size of the mount. rcbif shows a good example for a stick mount motor, but for a plate mount here are a couple of examples.

The first picture I show a mount i made for one of my Funbats that was simply glued right to the front of the nose. But I had to make sure that it was fully secured to all edges of the foam behind it. For the flat plates of foam behind it I had multiple layers to make sure it didnt rip free. I also made a version with "fingers" that went backwards into the fuselage and glued to in the inside of the fuse to get as much grip as possible.

The next few show a pusher style aircraft Im working on. There are no flat pieces of foam attaching the mounts, only edges. The advantage of this is I dont have to worry about a simple piece of foam coming lose and my motor flying off.
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Old Oct 08, 2012, 11:27 PM
Build straight - Fly twisty
Whiskers's Avatar
Australia, QLD, Little Mountain
Joined Feb 2010
4,176 Posts
I've seen methods of rubber-band motor mounting and I suppose they would have a bit of 'give' which limit damage in a *hard landing.*
The best thing is not to crash, and with a bit of practice that's easier done than said.
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Old Oct 09, 2012, 07:21 AM
Registered User
United States, OH, Troy
Joined Jan 2008
77 Posts
When I was starting out, I used a shock mount for my motors. I would take 4 toothpicks and glue them into the airframe so that the motor mound fit on. Then I would take a dowel and put it horizontally behind the motor. Grab 2 rubberbands and loop them around the motor in a way that won't rub and allows little slop. This method would not save a propeller, but I never bent a motor shaft with this setup.
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Old Oct 09, 2012, 11:11 AM
AKA Don
bz1mcr's Avatar
United States, MI, Houghton Lake
Joined Dec 2002
7,530 Posts
Dave Powers of RCPowers on youtube used to promote rubber banding motors on his 3D type planes.
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Old Oct 09, 2012, 02:22 PM
Damn this gets addictive.
Thechittyfather's Avatar
United Kingdom
Joined Oct 2011
515 Posts
I had the same issue. As mentioned above, spreading the load is probably your best bet. In the end if you get the mount right you will probably just get ripping around that area instead.
Each of my builds had a stronger mount than the one before untill I suddenly realised I'd quit crashing bad enough to do any damage.
1/16 ply makes for good way to spread the load well and the stick mounts available on line also have plenty surface area.
I would be concerned with brushless motors on a 'flexable' mounts. If the torque causes the motor to twist in the opposite direction it could interrupt the rythumn of the three phases. I've had it happen when testing motor/prop combos where the motor has not been fixed to something solid enough. You can hear them 'missfiring'.
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Old Oct 10, 2012, 03:16 PM
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Joined Jan 2008
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Many thanks for the feedback.

I think the best solution to my problem is just don't crash!
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