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Reply to "Continuing Saga …"

Thank you!

I completed the HO scale 567 and am selling it to a fellow in the Military Modelers Club of Louisville. He also asked if I could design a version of the FM opposed piston diesel. Probably… I just need a good cross-section and a lot of images. I only need a couple of bona fide measurements upon which to build the 3D model. I gave him a small discount since I knocked of the power takeoff hub, one of the tiny oil lines and one exhaust stack. I replaced the missing stack with some 0.040 X .125 styrene. Still blows my mind that the valve detail printed like the machine didn't care that it was half the size of the other model. I'm designing a bare block model with all the access ports and cylinders open. It's a diminutive model as you can see sitting on a die.

567 HO Primed

The next discussion is about the S-38. If you followers aren't interested, please let me know and I'll cease and desist.

I printed out the landing gear for the S-38 and attempted to make an entire set using resin alone. To do this I drew the model with a 1/8" hole down the length of the long strut. After growing, on the right hand set I didn't get the un-cured resin out of the bore and after post-curing, it solidified, necessitating me attempting to drill it out. I made a "D" drill out of a piece of 1/8" drill rod, but right at the very end, the hole began to wander and it pierced the side, rendering the strut kaput. I cut the strut off and drilled the rest of the hub to accept some brass for a new strut. 

For the left side, I drilled some small weep holes so I could flush the bore with alcohol before post-curing. This worked and I got a clean bore that accepted a piece of 1/8" brass tubing. I then drilled the mounting lugs to accept 3/64" brass rod reinforcement. In an attempt to press-fit the brass into these new holes, I overstressed the whole deal and in a slip, broke off the now-reinforced long strut, leaving me with two lower portions-only landing gear.

In addition to breaking off the long strut, I also shattered one of the mounting lugs. Since the brass was already in place, I built a new lug with Bondic. It took two tries to get it right. I first built it over the round brass pin, but the brass was too smooth and the Bondic pulled off. I then squashed the brass with a vise grips and did it again. This time the Bondic fix was quite strong. I had to hand file it to return it to its 1/8" original size.

S-38 Gear Reinforcement

Today, I located these lugs points on the fuselage. There was already some solder residue there and two small pin holes that showed the previous location. I didn't have much clearance to drill these holes. I was just about to buy an angle drill from Harbor Freight when I remembered that I may already have one. I did. It was a Dremel angle head that I use very infrequently (although I should use it more since it makes using some tool bits more easily). While it's pretty compact, I still had to grind about a 1/4" off the drill bit's shaft so it could clear the floats and let me go in at a good 90 degrees.

S-38 Angle Drill for Gear Holes

The holes worked and both gear fit where they're supposed to.

S-38 Gears in Holes

I used the old long strut to get the measure of the pieces I would have to manufacture.

S-38 Gear Measure

There are 1/4 -20 threaded holes in the engine nacelles and I first made the larger 1/4" lower strut with those threads. They didn't thread in nicely and they at the wrong angle. I don't think the engine geometry is totally correct, but I'm not going to attempt to fix it. I then turned the threads off the strut and let it float a bit in the hole. I want to able to make final adjustment and will epoxy it all together.

I drilled the bottom of the big end with a 3/16" drill to accommodate the small end. The other end of the this part had a lug turned to go into the resin hub. On one hub I drilled it with 1/8", but the other one didn't see stable enough for such a large hole and I went much small with a #42 drill. This meant that the two struts are actually different. I don't expect this gear to be weight bearing. It's just being fit in these pics. After all the soldering is done, I will install them permanently.

S-38 Gear Final FitS-38 Right Gear FitS-38 Gear Fit 2

Speaking of soldering. I spoke with a fellow in the tech support group of Harris Metals (a division of Lincoln Electric) and got some advice on solder and flux. My situation is atypical, soldering such small material to such massive material. We decided to go with a high-temp flux so it stays active during the extensive heating cycle and using 60/40 solid core solid to lower the melting temperature. I've ordered both materials from Amazon. Onward and upward.

 

Attachments

Images (8)
  • 567 HO Primed
  • S-38 Gear Reinforcement
  • S-38 Angle Drill for Gear Holes
  • S-38 Gears in Holes
  • S-38 Gear Measure
  • S-38 Gear Final Fit
  • S-38 Right Gear Fit
  • S-38 Gear Fit 2

OGR Publishing, Inc., 1310 Eastside Centre Ct, Suite 6, Mountain Home, AR 72653
800-980-OGRR (6477)
www.ogaugerr.com

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