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Author Topic: Radio Mounting  (Read 1067 times)

Offline Tim Wescott

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Radio Mounting
« on: April 23, 2013, 01:21:16 PM »
Seeing Joe's plane at the Tune Up made me realize that there are folks out there who have never gone through an RC phase, and yet may want to try using radios for Carrier (or, for that matter, scale).

So here's some pictures from my shop, and some explanations.  This is basically what I told Joe at the meet, with pictures of what I wished I had in my truck to show him.

Somewhere on the net there's probably a much better presentation -- Google around, see what you find.

When you go and put a radio (or any other electronics) into a glow-powered plane, there are two basic incompatibilities that you need to remember:  One, engines vibrate, but electronics don't like being vibrated.  And two, engines spew oil, and electronics don't like getting oily.  Of the two, the vibration problem is by far the more important one.

Always protect your electronics from vibration.  Always.  Receivers and batteries need to be wrapped in closed-cell foam rubber, and the foam bundle put someplace where it'll stay in place.  The top picture shows the receiver mounting in an RC trainer.  What you see is the foam that's wrapped around the receiver, tucked into the fuselage just ahead of the servos.

Don't use just any foam -- you want real foam rubber, and you want closed-cell.  Any real hobby shop carries it.  You'll get a big square of it, and cut off sections to wrap your stuff in.

I put these pictures out of order -- oops.  The second picture shows the battery wiring, with switch, charging jack, and battery.  Note that this is sitting on a pad of that foam rubber.

You can't wrap your servos in foam and shove them in a hole -- but you still need to protect them from vibration.  The third picture shows a servo out of a plane (who recognizes that servo?).  This servo has four mounting holes.  Each one has a rubber grommit, with a screw through the grommit.  When the servo is installed, you tighten the screw just enough so that the grommit grips the servo, but not so much that it gets chewed through.  You can get servo mounting kits at your LHS; these come with screws, grommits, and brass ferrules that you can use as standoffs.  The DuBro kit has a picture on the back showing what to do.

Mount the servos to a pair of rails (seen in the top picture) or into a plywood tray, or into a hole in some plywood.  The wood should not touch the servo anywhere -- if it does, it'll transmit vibration.  Instead, there should be clearance all the way around, and the servo should be located by grommits.  The fourth picture shows a plywood servo tray with one servo taken out -- and, right ahead of the tray, you can see the foam around the battery pack.

Guys that fly profile RC planes usually make a radio compartment in the wing.  Looking at Joe's plane it looks like he could do the same thing.  The usual RC way to do it is to make the compartment entirely behind the spar, where the curve of the wing is less.  I'm showing a compartment that goes both in front of and in back of the spar, because I know that Joe is retrofitting an existing plane, and wants to maintain balance.  There is no reason, particularly on a new build, why you couldn't make this compartment on the bottom of the wing and put your servo in the lid -- that way all of your wiring will be hidden, with just the top of a servo sticking out.

Another advantage of putting the compartment back there is that the servo is out of range of getting raw fuel dumped on it.  It'll get some exhaust slime, but that's better than raw fuel.  Putting the servo entirely inside the wing with just a pushrod coming out would be the bee's knees, but it's not necessary.

If you're cheap like Joe and me, then keep in mind that nearly every RC guy in creation seem to have spare servos, and a lot of them have spare wiring harnesses.  Some may even have spare batteries (I don't know if they still do, but the last time I bought a complete radio it came with transmitter, receiver, servos, switch harness, and battery -- if you fly electric, the battery and switch harness get left in the box).  If you want to save $10 or $20 and you have RC friends -- ask.
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The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Chris McMillin

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Re: Radio Mounting
« Reply #1 on: April 23, 2013, 03:10:36 PM »
Looks like an old Ace or Tower servo in white and a Kraft in gold? That's Nostalgia right there!
Chris...

Offline Tim Wescott

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Re: Radio Mounting
« Reply #2 on: April 23, 2013, 03:16:00 PM »
Looks like an old Ace or Tower servo in white and a Kraft in gold? That's Nostalgia right there!
Chris...

The white ones are Heathkits, that I built before I could legally drive.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Mike Greb

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Re: Radio Mounting
« Reply #3 on: April 23, 2013, 05:12:22 PM »
I mount my receiver and battery with foam mounting tape.  Had a servo mounted with  mounting tape, it kept moving around.  I glued it onto the side of the fuselage with silicon sealer and so far it has stayed put.

Offline john vlna

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Re: Radio Mounting
« Reply #4 on: April 23, 2013, 05:21:26 PM »
Mike,
I do something similar on my profiles. I use velcro for the RX and glue the servo on. No problems so far. The velcro allows me to switch rx's from plane to plane if needed.
John

Offline Tim Wescott

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Re: Radio Mounting
« Reply #5 on: April 23, 2013, 05:39:52 PM »
Mike, John -- are you running engines, or 'lectric.  Electrics vibrate a lot less.

I do admit that my "wrap it up in foam" reflexes are from about the same date as that Heathkit servo.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Mark Scarborough

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Re: Radio Mounting
« Reply #6 on: April 23, 2013, 06:52:01 PM »
Mike, John -- are you running engines, or 'lectric.  Electrics vibrate a lot less.

I do admit that my "wrap it up in foam" reflexes are from about the same date as that Heathkit servo.
LOL, I remember looking at those Heathkit radios thinking,, wow they are cheap,, I could do that,,

as to the foam rubber,, the guys that I pylon race with for the most part just use velcro to stick their recievers in the airplane,, the electronics now are pretty solid,, and not as PRONE to vibration damage,, now ESC componants are still some discrete units, mainly the capacitors,, and they would be prone to vibration, but they also need airflow to some extent,,

servos you need vibration isolation as well as allowing some latitude for the case when the servo throw exceeds the available motion of the surface, or throttle,,
Joe, I need to come visit,, I can set ya down the path in no time,,

one thing you really should consider,, using Nicads or LiFe batteries for the reciever( and transmitter) ,, Alkalines dont really have the right voltage drain curve to work reliably IMHO
For years the rat race had me going around in circles, Now I do it for fun!
EXILED IN PULLMAN WA
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Joe Just

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Re: Radio Mounting
« Reply #7 on: April 23, 2013, 07:26:03 PM »
Mark, I am converting to rechargeable batteries as I soon as I can.  As I advance and really get hooked (not far from that now!) I will get the more sophisticated  battery.  As always a visit from you would be welcome anytime you can get away.  In mentally reviewing  the 3 attempts Sunday I really feel the major problem was the tank set up. The first flight ran out of fuel on the first 5 laps. The second attempt the plane touched the ground on takeoff and I just let he grass stop the engine running.  The 3rd and last attempt here is what was happening.  First 4 laps it was running pretty good, but a bit slow. Then the engine started to drop speed like it was not getting fuel. I changed the throttle from fast to slow and then back. The plane picked up speed and then began to die again. Before the 7th lap  the same thing started happening again and the engine died.  I sincerely believe the tank was spilling fuel through the two fill and overflow tubes, loosing a bunch of fuel.  Lots of raw fuel on the wing, etc. Today I ran the engine as it was when I brought it home. Some syphoning on the table.  I now have one of two new reliable tanks I can place on the plane if needed. I set up the first and original tank with pressure line and pinch off on the overflow.  If this does not work I will change to a new tank. If that fails I will consider some of the other cures as were mentioned to me Sunday.  I still have the Hellcat which has yet to be run as well as the F7F that needs some crab tweaking, so you can see I have a lot to work on.  All this sure keeps me busy and more importantly..HAVING FUN!!
Joe

Offline Duke.Johnson

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Re: Radio Mounting
« Reply #8 on: April 23, 2013, 08:32:30 PM »
Joe
Just a thought about the engine changing speed/RPM's.  I had a plane that would not hold steady RPM's once, my pushrod/clevis was loose or had slop in it.  I just had to screw in or adjust the clevis to make it tight, problem solved.  I about pulled my hair out until I found the simple problem.

Offline john vlna

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Re: Radio Mounting
« Reply #9 on: April 23, 2013, 09:37:05 PM »
Mike, John -- are you running engines, or 'lectric.  Electrics vibrate a lot less.

I do admit that my "wrap it up in foam" reflexes are from about the same date as that Heathkit servo.

I run both electric and glow. I have had shock problems with esc's. Because of the discrete components Mark mentioned? No problem with receivers, even in a crash.
John

Offline Mark Scarborough

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Re: Radio Mounting
« Reply #10 on: April 23, 2013, 10:29:57 PM »
I run both electric and glow. I have had shock problems with esc's. Because of the discrete components Mark mentioned? No problem with receivers, even in a crash.
John

That follows along with my experience,, in Pylon racing at least,, I have had recievers hit the ground HARD ,, around 120 mph,, and survive while if not supported right, the ESC dies a horrible death by either some failure on the board, or one of the Capacitors getting damaged,, I usually use a generous patch of Velcro and wire ties around the wires on both ends, and the body. The Velcro acts as an absorbtion for the impacts,,, it seems to help..
Though in Pylon these impacts generally do not happen on every flight, ( like they do in Carrier) but we see enough to generalize trends too,,

I will say the advent of 2.4 has certainly revitalized my interest in  carrier,,
For years the rat race had me going around in circles, Now I do it for fun!
EXILED IN PULLMAN WA
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Offline john vlna

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Re: Radio Mounting
« Reply #11 on: April 25, 2013, 04:10:36 AM »
Here are a couple of shots of how I mounted the Rx and slider release servo on my Seafire


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