Motor Mount in Foamular 250

 The Foamular 250 we are using is rated for compression of up to 25 psi (lbs/sq-inch).   It is more stiff than other foam I have seen in model airplanes and a bit heavier.   We cut out the foam where we don't need the strength, so we are not hurt by the weight.   For motor mounts it seems like this extra strength could let us just gorilla glue some screws into the foam.   We tried this and it seems to work fine.

 For this experiment we used M2x20 screws.  So 2 mm diameter and 20 mm long.  The motor mount uses 4 screws but for this test we only used 2.   We drilled two holes in the foam and filled them with water (poking small nail in to get all the air out).   Then we covered the screws with gorilla glue and put them in. 

First we tried just putting a weight on to hold them in:


But it was hard to get it to hold both screws down well.   So we put a piece of plastic over and a clamp and let it cure overnight.


So for the test this is what it looked like:


And here is the video of the test:


It took 17 lbs of pull to break it.   This was only 2 short screws.  In the real plane we would use 4 longer screws.   It seems strong enough.

After the holes looked like this:  I had dug out the missing foam in the center so the mount could lay flat even with the string going behind the center.

And the short small screws after.  It looks like the gorilla glue held to the screws and to the pink foam and the pink foam is what failed. 


So I think this is a fine way to mount motors on planes made with Foamular 250.    Not too heavy and strong enough.


Update Jun 9, 2021

     It occurs to me that if the motor gets hot the screws could get hot, which could soften the foam, and cause it to fail.   So there might be a problem.   We will probably test a battery full on the ground before launching into the air.


Comments

Post a Comment

Popular posts from this blog

Switching from iNav to Ardupilot for Flight Controller

   We had been using iNav software for the flight controller but have decided to switch to Ardupilot the following reasons:    1) Ardupilot can have a "companion processor" like the Jetson Nano that does vision/AI and decides things like which way to go.   We really want to explore what can be done with AI on a solar powered airplane.   Like can it avoid clouds and stay in the sun more, can it scan the horizon with a telephoto camera looking for boats, can it head for a boat automatically, etc.   This seems fun.    2) Ardupilot can use a companion processor to communicate over cell data network (4G) to a ground station.  With this we could fly all around Anguilla and still have communication between the ground station and the airplane.  So from the ground we can change the mission plan during the flight.    We could decide to go to a particular boat, or decide to come home because the change of rain has gone up.   Or if we don't have AI avoiding clouds we could do it
Read more

Stabilized Camera / Pan-Tilt

Image
  With a "two servo micro gimbal" you can tell iNav to stabilize your camera.  The flight controller already has tilt sensors and a computer, so with the iNav software setup right it can control the servos and stabilize a camera.  You do need to have 2 extra servo outputs on the flight controller.     There are a number of these on Amazon.   If we just search Amazon for "servo gimbal Mini Pan-Tilt mount FPV" there are several for under $25 but you may have to put in your own servos.        You can also 3D print the plastic parts and add your own servos.   This is for a Raspberry Pi or Jetson Nano type camera but should not be hard to get it to hold a DJI Camera. There are also head trackers so that the airplane can point the camera where you turn your head.  This increases the feeling of being on the airplane, so can increase the fun.
Read more

Crowd Funded and Crowd Researched

  After I get one prototype working reasonably well I will update this page with conditions for a prize for improvements in the design. Crowd Research Prizes         The "goodness number" (GN) will be miles flown in one day (relative to air).         Improvements of X percent over the previous GN  will get a prize payout of the amount X * Y dollars.   The Y will start at $200 but can increase as we get crowd funding.             Each time a prize is awarded the GN benchmark will be adjusted.  Technical Requirements   Must use Fomular 250 or foam on Amazon   Must use Maslow CNC if any CNC unless expected prize payout is more than twice the cost of the CNC.  If a new CNC is once accepted it will always be an option for future contestants.   All parts except solar panels and Fomular 250 must be from Amazon   Must be solar/battery/electric - no gas/fuel or fuel cells, etc   Solar panels can be anyplace with public prices but we like solarealdrone.com   Must use iNav on flight con
Read more