Machining an Engine.......
 

Hey guys,
I know several of you do really fine machining so I'd like to get your opinion on a project that I would like to take on....but I'll start at the beginning.
Last fall I took a class (the first of a three series class) in machining. The class dealt with basic lathe operation, threading etc. This spring I have enrolled in the second portion, milling. I'm supposed to pick a project and I'd really like to build a half-A engine. The instructor, by the way, encourages engines as he's built 2 cylinder, 4 cylinder, steam and external combustion engines. I've been browsing previous posts and I've looked into Schroeder Replica's . I'm drawn to the Schroeder Twin, though I'd really like .049 displacement better than .020 since .049 stuff is so much more abundant and cheap. Know any place where I might pick up .020 stuff cheap?
The simple single looks classy, but I really want to do a twin-a true twin (as opposed to the geared Babe Bees). I'll be spending quite a bit of time on mills and lathes in the next 10 weeks as I just picked up a second job working at technical services on campus as a cadet machinist (the current one is graduating at the end of the quarter). I've got access to good equipment (Bridgeport with digital x,y in the lab and Enco with digital x,y at work plus a host of lathes). And I know that the instructor would be able to help me with the silver soldering involved. What do you guys think. Are there plans that I'm overlooking? I know Mr. Coholic is a master of this sort of thing, what do you recommend? Thanks!
Derek

Machining an Engine.......
 

Derek,

You lucky bugger. I can do a lot with my Taig but I sure wish I had access to some REAL equipment.

Do the twin, but make it with two .09 cylinders, might be easier. Or, if you want a REAL challenge, try two .010s. :D

Just kidding. If I were to try the twin, I'd do it with .049 cylinders but I'd be tempted to use Norvel or Wasp parts.

But, Andrew Coholic is THE man. And a right decent fellow to boot. Excellent flyer and experienced in a great many aspects of the hobby.

Machining an Engine.......
 

Don't be skeered! Build a radial!! I can see a 3-5 cyl 049 pretty cheap.

Machining an Engine.......
 

Thanks for the encouragment :D

Yeah a radial would be really really cool, but shoot-the crankshaft worries me as it is :D

The other issue is this: I'd perfer to spend my time in the machine shop instead of autocad-as much as I enjoy autocad.

Do you think a conversion from .020 to .049 on that horizontally opposed twin would be too difficult?

Machining an Engine.......
 

I've never built one but aside from scaling up the parts, I would think that it should be somewhat easier in the larger size. If you're thinking of using a throttle, please consider using one that has an adjustable airbleed. A stock Wasp throttle would work with the added adjustable airbleed and the only thing you'd need to do in addition, is to bore out the barrel to suit the larger displacement. Trial and error would be required in that regard.

Machining an Engine.......
 

I wonder if an os 10 carb would be about right? does an opposed twin need twice the carb opening, or the same size as it is alternate firing? but it can't be alternate firing on a reed, could it? there would be no crankcase pulse... and who's going to do a monosoupape radial w/ babe bee cylinders and one valve... hmm, would probably fly a 40 size d-viii with that, now that would be cool!
anyway, alternate firing w/ disc valve would probably work... hmm, I'm frying my brain, maybe i'd better stick with buying 40.00 norvels and hacking balsa, and leaving the engine stuff to you guys! :D

Machining an Engine.......
 

I went poking about Schroeder's Replica site, and stumbeled across some pics of the twin being built: http://archive.dstc.edu.au/BDU/staff/ron/index.html
Looks intimidating. I am starting to lean towards the single, it's better suited to my experinece.
I'd still like to hear any advice or speculation that you guys have for the project though. Anybody know of any other designs? I like how the Schroeder Simple engines utilize cox bits. Though I'd like to work on that too. Seems there's got to be a way to drill and tap the heads for a short glow plug and still get decent performance out of the engine. Guess I better start collecting dead heads. Thanks for all the advice!
Derek

Machining an Engine.......
 

Wild Fred,

You may be right, the OS .10 may be a better choice. I believe that this twin though, has a double throw crank making it simultaneous firing.

Derek,

Aside form the crank, it appears that the rest of the engine ought to be reasonably doable. "Specially if you have a sympathetic instructor. I'd give a lot to be in your shoes,,, all that neat equipment. If you don't do an opposing twin, consider a V-twin driven off a single throw crank.

Conversion heads that use standard glow plugs allow for better throttling but the power loss, for me, is unacceptable. But, if you do a twin or even a single, it never hurts to experiment. If all you want is a runner, perhaps max power isn't an issue.

If I were in your shoes, I'd do the twin.

Machining an Engine.......
 

Hey boys, just back from Toledo and have another big bag of cox parts and engines to play with. Talk about cheap! I picked up LOTS of new parts/engines... nice :)

OK here is my experience having made the simple single, and many (allmost two dozen) 020 and 049 versions of the twins. Roger's 020 twin is a really sweet little engine. The 049 twin, which by the way was published in Strictly IC magazine as a series of construction articles, is easier to build due to the size. The machining is not that hard but you must be good at drilling a deep, small diam (1/16) holes (a lot of them!) and also be able to machine cut the threads for the cylinder mounting. The crank is silver brazed from 3 pieces and the rods are trapped onto the pins after assembly. You MUST make up an assembly jig to hold the front and rear journals together for brazing, as there cannot be ANY runout in a small engine this size or it will bind terribly and not run. Also it is tricky at first toget just enough silver brazing onto the pieces tobe joinded without it running into the rod ends and freezing the rods. A small oxy/propane torch is required. If you want to tackle this project I can tell you where to get plans.

That being said, I suggest trying the simple single first. It is another sweet little engine, rear disk induction and a good runner. Then try the twin, then a radial, etc!! :)

I also bought three cox Medallian 15's at Toledo and I am contemplating either making a twin 30 or radial 45 from them. Allways something new to think about!!

Also picked up thre 010's and there is some definite possibilities with those too...

OK thats all for now. Keep us posted in your efforts please! If you need any further help email me at [email protected]

Andrew

Machining an Engine.......
 

I ordered the plans for the Simple Single today. It will be a good introduction to the process and after that I'll tackle the twin if I still feel up to it. I'm sure I'll have questions in a few weeks. Till then I'll scope out parts-so far the cheapest I have found for cylinders is a guy on ebay who will sell 2 cylinders and pistons for 10 bucks and you get to choose from a variety of exhaust/porting options. I'll wait and see what the plans call for. Thanks!
Derek