BOLLAERO based in line twin project

[SmithyCranker]

Hi guys, long time lurker, first time poster. I've been working on what started out as building 3 BOLLAERO. 18s. I started with pistons and cylinders and when I made the crank cases I found I was unhappy with them all and all had some sort of "custom cut" or error. As the failure stewed In my head for a day or so it cooked into a completely crazy idea..."Hey, I should build a opposed firing, separated crankcase in line two stroke diesel twin with a throttle?" So here I am, halfway done and just figuring out to show it to you guys. I know it's a bit ambitious for a first engine, but I'm feeling hopeful. Any constructive criticize (that hopefully doesn't have me remaking parts too much, LOL) is appreciated. So first question, the crank is made out of 12L14 which probably wasn't the best choice, but the cuts Intimidated me. SHOULD I harden the crankshaft or run it in its current state? Here is a few photos:

View attachment 1418313735306.jpg

View attachment 1418313752601.jpg

View attachment 1418313919438.jpg

 

[Piston_Broke]

You will likely end up with a very warped crank shaft if you heat treat it.

 

[SmithyCranker]

That is what I feared. I think the shaft will be strong enough as is, I have no idea what kind of power to expect so hard to tell, but the crank pins are 3/16 so there is a little meat. I'm hoping to get this thing to run well enough to power a rc boat, through either water or air propeller.

 

[GailInNM]

I have used 12L14 for crankshafts on several engines without problems. Your crankshaft is of ample proportions that you should have no problems with it. In recent years I have switched to 1144 stressproof. It is stronger, but the main reason is that it does not tend to warp when the crankpin is cut as 12L14 sometimes does. It cuts almost as easy as 12L14 does.

You should have a good runner as you are starting with a proven design for all the timing. I did an inline twin compression ignition engine a few years ago that was about half the displacement of yours. I built 2, one with a 12L14 crankshaft and the other one ulsed 1144 for teh crankshaft. If you are interested, the drawings are posted at:

http://www.homemodelenginemachinist.com/downloads/lobo-16-cc-twin-cylinder-2-stroke-diesel-161.html

Gail in NM

 

[Cogsy]

From what I've recently read, I believe the 12L14 may 'sweat' some of it's lead out at a high enough temperature to harden it, which doesn't seem ideal to me. I don't know if that means it can't be successfully hardened, but I wouldn't risk it, especially when, as Gail says, your crank should be fine.