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Author Topic: Is there an easy way to swap engines in a full fuselage stunter?  (Read 796 times)

Offline frank mccune

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           I am contemplating changing all of my planes to one size and make of an engine.  Is there a simple way to do this on a full fuselage airplane.  On a profile, it is  quite easy but carving on the nose to get at the mounting hardware, may be a bit of a hassle.  I checked my Christal Ball and I saw a 12" 9/64 drill in my future. Lol

         Suggestions and/or comments?

                                                                                                                                                             Tia,

                                                                                                                                                             Frank McCune


Online Ken Culbertson

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Re: Is there an easy way to swap engines in a full fuselage stunter?
« Reply #1 on: October 09, 2018, 05:52:16 PM »
No

You did say EASY!
« Last Edit: October 09, 2018, 07:51:45 PM by Ken Culbertson »
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Online Randy Cuberly

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Re: Is there an easy way to swap engines in a full fuselage stunter?
« Reply #2 on: October 09, 2018, 06:45:30 PM »
Some engines can be swapped out without too much grief but not very many.  For instance RO Jetts, at least the large ones can be exchanged with PA's with a minimum of labor.  A few others can be exchanged by drilling larger holes in the mounting lugs.  Oversize holes allow replacement of one for another if the mounting pattern isn't too different.  Some of Randy Smith's PA engines have mounting patterns with the holes slotted in somewhat of an X-pattern and enlarged holes to allow swapping out with a few other engines.  Most often however the difference in shaft lengths require some modification of the front of the fuselage to allow mounting the engine farther forward or aft or adding or removing some material from the fuselage to make things match up. 

However, I think the best thing is to simply build for a particular engine or particular type or size of engine and stick with it!

If you're serious about stunt get some PA's or RO Jett's and build around them.  The investment is more than worth the cost!  Or of course there's always the Chicken"s way out and just go electric!

Randy Cuberly
Randy Cuberly
Tucson, AZ

Offline Gerald Arana

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Re: Is there an easy way to swap engines in a full fuselage stunter?
« Reply #3 on: October 09, 2018, 07:05:30 PM »
It depends.....on  What the other guys said.

Or you could cut off the motor mounts completely and radial mount any engine (that isn't to wide) with an extra fire wall and an (heaven forbid) RC mount.

Good luck, Jerry

Online Ken Culbertson

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Re: Is there an easy way to swap engines in a full fuselage stunter?
« Reply #4 on: October 09, 2018, 08:22:22 PM »
           I am contemplating changing all of my planes to one size and make of an engine.  Is there a simple way to do this on a full fuselage airplane.  On a profile, it is  quite easy but carving on the nose to get at the mounting hardware, may be a bit of a hassle.  I checked my Christal Ball and I saw a 12" 9/64 drill in my future. Lol

         Suggestions and/or comments?

                                                                                                                                                             Tia,

                                                                                                                                                             Frank McCune
OK, now that we know it is not easy but there is a way to make a "universal" mount from 1/2" aluminum channel stock.  Glue/screw the channel to to the doublers and cut a rectangular slot that will allow any engine you chose to fit within the rectangle.  Now slip a 3/8" square maple into the channel and drill it out for your current engine.  Fit it with recessed blind nuts or anchors.  Now if you want to change engines, you just drill out a new set of maple inserts.   I wish I had a picture but the last time I used one was in the 80's and the plane it was in never made it to the 90's.  The only downsides were that the vibration transfer was not as good as pure maple so you had to make sure to balance your prop & spinner thoroughly and you can't sand aluminum so you have to make them short or use a huge spinner!

FYI - this works on a profile as well but your best solution is to "Chicken Out" and go electric.

Ken
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Offline peabody

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Re: Is there an easy way to swap engines in a full fuselage stunter?
« Reply #5 on: October 10, 2018, 05:42:05 PM »
I believe that there is a "motor mount system" available from Brodak that clamps the engine with aluminum pads.
Windy used these with a great deal of success.
http://brodak.com/motor-mount-system.html

Offline Bob Hunt

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Re: Is there an easy way to swap engines in a full fuselage stunter?
« Reply #6 on: October 11, 2018, 05:56:44 AM »
Actually there is a fairly easy way to switch engines in a full bodied stunt model. Years ago (when I still flew glow...) I would inlet the motor mount beams in my planes to accept 1/8-inch thick steel plates that would extend fore and aft of the area in which the engine would reside. These plates were held to the mounts with either blind nuts above the beams, or by using tapped brass inserts (I know many modelers do not like to use the inserts, but they never gave me any trouble...). The plates would then be tapped to accept the engine of choice. If I wanted to change engines all I had to do was make new plates.

Interestingly, I tried to save weight at first by using aluminum plates. I had two sets of those crack while practicing at VSC (on separate years...). Each time I replaced them and everything went fine for the rest of the week. After two such episodes I switched to steel plates. The extra nose weight was negligible.

The attached photos of the first replica Caprice engine compartment shows the above to good effect I think. Note that the engine shown is a Magnum .36. I switched to an Aero Tiger .36 before the model was even flown with the Magnum.

Bob Hunt



Offline MikeyPratt

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Re: Is there an easy way to swap engines in a full fuselage stunter?
« Reply #7 on: October 11, 2018, 09:18:17 AM »
Hi Frank,
Lots of good suggestions here, Bubba is right make a steel plate and swap the plate with the new engine.  It would also ad to make a plate that looks like a horseshoe so the mounts are connected.  This will greatly increase the strength of the front end help reduce the vibration.  One of my Magnums was built with the plate and it was really easy to swap engines.

Later,
Mikey

Offline Tim Wescott

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Re: Is there an easy way to swap engines in a full fuselage stunter?
« Reply #8 on: October 11, 2018, 09:38:06 AM »
I'm doing Bob Hunt's plate thing, but so far I've done it with 3/16" or 1/4" aluminum, and rather than insetting the motor mounts I just set the crutch higher in the fuselage.

I don't have a lot of planes finished using this system, but at least two profiles with it have just lasted and lasted and lasted.
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Online Ken Culbertson

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Re: Is there an easy way to swap engines in a full fuselage stunter?
« Reply #9 on: October 11, 2018, 11:09:12 AM »
Actually there is a fairly easy way to switch engines in a full bodied stunt model.

Bob Hunt
I think I like Bob's method better than mine and definitely use steel.  I would avoid Aluminum with only 1/8" grip.  3/16 is ok if you have the tools to tap aluminum without overcutting the threads. But, back to the original question since all of these methods are great ways when you are building....but not retrofitting.  I still contend that there is no easy way to switch if you didn't plan for it when you built it.

+ when you are done the muffler and needle valve still don't fit the cowl ...aggh...

Ken
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Offline frank mccune

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Re: Is there an easy way to swap engines in a full fuselage stunter?
« Reply #10 on: October 11, 2018, 12:14:39 PM »
       
        Thanks for the replies!  On profiles, no problem but built up!!!!!!!!!!!!!!!!!!!!!!



                                                                                                                             Be well,

                                                                                                                             Frank McCune

Offline Steve Helmick

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Re: Is there an easy way to swap engines in a full fuselage stunter?
« Reply #11 on: October 11, 2018, 02:20:52 PM »
I think I like Bob's method better than mine and definitely use steel.  I would avoid Aluminum with only 1/8" grip.  3/16 is ok if you have the tools to tap aluminum without overcutting the threads. But, back to the original question since all of these methods are great ways when you are building....but not retrofitting.  I still contend that there is no easy way to switch if you didn't plan for it when you built it.

+ when you are done the muffler and needle valve still don't fit the cowl ...aggh...

Ken


Steel isn't needed, and 1/8" aluminum would be perfectly ok, at least up to .46's. You should countersink flathead (socket head) machine screws from the opposite site and put washers and elastic lock nuts on top of the engine mounting lugs. Then bolt these plates to the maple engine bearers. The late Larry Cunningham devised the "U" shaped version and thus it got named "The New Mexico" mounting plate. I made simpler strips for each side and liked the results.

Other than that, some engines have one pair of holes that are the same, but the other two aren't. ST G.51/Royal 45/Magnum/ASP .40>.53 fall into this category. Drilling an extra pair of front holes in the G.51 bearers makes it swap with the others. If you're not willing to do this, oh, well! I would point out that if you crash hard on pavement, the chances are pretty good that the engine is toast anyway, and the extra pair of holes won't decrease the value any!        D>K Steve

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