- Jun 18, 2020
- Reaction score
I may have already replied but I couldn’t find it if so then ignor me. I also ask forgiveness for spelling as I have a double vision issue that makes typing extremely difficult. Sometime a misspelled word completely changes the note . I do proof read with a magnifying glass but even that aid I still miss things.Ray-
not derailing my thread at all =) I love to hear the stories. I've heard it said that at a META power check in a maintenance hanger, if you were standing in the wrong spot you would be struggling just to breathe...one day I hope to experience the real thing, but until then, this is what I have =)
so. I’ve built many rc scale warbirds. My handle should give a clue to my favorite.
your engine task is a daunting project. I don’t think anyone has built or even presented a cadd model of this engine. It was on my list but even with access to solid works I have stayed away. I do have the Hobson 18 cyl plan set and have reviewed it page by page. Then given thought to your project. When scaling models one thing come out quickly. That is not everything scales perfectly nor functionally. Cadd makes numeric things relatively easy. But when you transfer this to an operating machined engine it may not work out as you planned.
starting with the crankshaft is where I’d start too. Tom from Tom’s maker site has done a very nice job of creating and building an 18 cyl. Radial. On his cadd and cnc. Reading and looking at the Hobson drawings shows some great ideas as. The issue I see is that the engine may take many assembly steps and pressing the crank together may cause issues. Looking at Whitesbook you can see the complexity of it. Those movable counterweights may not be necessary as the vibration probably won’t be present as the material and proportionate strength, may not scale. Hobson only uses a 1.000 bore. So the piston is already designed as are the rings and assembly fixture. I looked at the two piece rod but I don’t think there is room enough room for a strong enough bolt without changing other things. The 18 cyl. crank has a splined insert crank pin. In real life it must have been a huge project to remove and replace this. I don’t know the torque needed. To get around this I look back on some drag racing issue we had with narrowed rear ends befor custom axels were made. A large axel was cut off near the flange then turned down to fit in a hole bored through the flange. This provided a bearing surface. Then the flange and axel were sssembled. Some were press fit then welded. The best were pressed then drilled on the hole line for a dowel,pin and welded. These were incredibly durable in the era. So for the new radial a slip fit could be made using the same feature it would be removable for assembly and disassembly. Modern two stroke small engines use press fit cranks.a hard prop strike or crash udualy knocks them out of slighnment or bends them. But some careful machine work would probably work on this model. Inventer may have some stress analysis available. I did a lot of this in industry with some expensive software. I even had vibration software. It’s been a long time since I even looked at my notes on this . I’d try it my self if I ever get out in the shop again. Doctor would probably commit me if he knew what I’m doing as it is. I’m not supposed to play any sports not even tiddlywinks . I ventured out to the batting cage . By using an eye patch I was able to hit a few pitches but I’m out of the game for good.
anyway. I just wanted to stay with you on this. I hope you can put up some screen shots as you go.
hood luck as you go on.