This afternoon I was digging through boxes looking for one of my Kamtechnic radial mounts for TD/Medallion .049 engines.  In one box I found this engine that I made for a project a few years ago.  I don't think I ever posted about it here.






I drew up a quick trainer sized for reed valve engines around a length of 3" SIG airfoil balsa sheet.  At the time I was getting into bladder pressure for .049's, so that ruled out Bee engines.  I could have just used a product engine with a Brodak 1/2A mount, or a firewall and cheek blocks.  But I wanted to try something different and unique.  I wanted to do a beam mount reedie.  I've seen three or four methods of doing a beam mount reedie over the years, but they all seemed either too complicated, time consuming, or too expensive.  I pondered for a few minutes to figure out the quickest and cheapest method I could think of.  So I looked through my leftovers for some 1/16" aluminum angle and found some 1" angle.  ¾" would have been better, but whatever.  I figured I would drill a center hole in one side for the venturi and then four holes around it for the crankcase screws to make the crankcase backplate.  On the other face I'd drill four holes matching the lugs of a TD/Medallion .049 engine.  I could have just cut the second face for just the the lugs like a TD, but then I thought, "Why not integrate a mono-wheel landing gear?"  So I took a pencil and marked the holes to drill for the crankcase and the leg for the wheel.  Then I had to figure out which backplate to use.  I could use a spare horseshoe backplate, but since I was going to do bladder pressure, I needed a 128TPI needle.  I've done pressure with an 80TPI needle, but there was just not good fuel flow control with the coarse thread.  So I picked out a beat up postage stamp engine backplate with the 128TPI needle in it.  I carved the plastic to match the sides of the crankcase, then filed the aluminum tab to also match the crankcase.






And then, for good measure, I bent the aluminum angle to get about 3 degrees of right thrust.




The setup worked great.  I'd say it's about equal to Medallion engine performance.  Are the lugs inline with the crankshaft?  Nope.  But I'm not going to complain about a 1/8" offset when mounted to the fuselage.  Not for around 30 cents worth of aluminum angle and a couple of hours' effort.  If the offset bothered me, I could just put shims under the lugs to bring the crankshaft back in line with the fuse centerline.

  And the gear leg gets tweaked on hard landings, but that's easy to tweak back.

edit:  Hmmm... I have a couple of slab wing models I've built since then for TD's and Medallions.  Maybe I'll mount this to one of them and see how well this concept has aged.

Mark,
May I recommend you making a collage of the pictures and submitting this work as an entrant in the CEF Cox Engine of the Month?

That's just genius work! Why do we work so hard to strip a postage stamp engine for the NVA when one can build the model around this set up? Especially as the model becomes a more flexible airframe between this and a Medallion or Tee Dee.

I'm just slack-jawed...Bravo!

Mark:

How sweet it is! Yet another contribution from all your good work on behalf of C/L fliers.

Dave Mo... 

Well, I said I was going to use this on one of the slab wings planes that I built, but then I said, "Hmmmm...." (I Hmmm a lot).  I thought that this would be a great engine for my Skyray 110. (Build thread)







Mark

              Mark, didn't you build a few of these? I vaguely recall a pink Monokote Skyray. It looks great and that built up wing would certainly seal the deal.I bet it works great. Nicely done as usual.

Ken, that was back when I built three Skyray 35s and this 110.  And that neon pink Monokote was the worst Monokote I've ever used.

             Mark, your assembly approach is envious by all of us. I always say I'm going to do this and I get half way into it and I never fully commit. Your 1/2A version has some very innovative ideas for the Skyray. I hope it flies as well as it looks. I recently had 4 rolls of Monokote which went right into the trash. Two rolls were silver and the second the heat hit it, it krinkled up and pulled away from the edge like low temp TowerKote. In addition, it left color on the wood when pulled up and repositioned. I never ever had this happen with true Monokote. This ALWAYS happens with the more inexpensive clone iron on coverings. The color ends up being a gooey sticky mess that beds itself into the wood. The only real way I've found to remove it is with using acetone and a brush and rags. A real mess so I tossed all of it. White was the other colors and it too was acting unforgiving. Typically, I can go as high as 2-2.5 on my iron using Monokote without a issue, I can even put it on full to do stubborn wingtips but this stuff was krinkling like Econokote.

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