The "2-Bits" V-Twin

[Johnmcc69]

 
 VERY nice work!
 

 John

[RReid]

Roger and John, Thank you guys!

Got both pistons nearly finished today, in between some errands and other distractions, but didn't take a single picture. Pretty straightforward lathe work anyway. Just need to mill in the slots that allows for the swing of the con rods, and drill for the wrist pins, which will be on tomorrow's agenda.

[RReid]

I drilled the pistons for the wrist pins with pistons held in the vise and the vise laid over on it's side. Once drilled, I could then just rotate the vise onto it's bottom to mill the con rod slot.




The wrist pins were simply parted off some drill rod stock, and the ends rounded and polished. I like to use the plastic container lid as a catch tray, otherwise small parts like this tend to use their momentum to go bouncing away into dark corners.


The basic rotating assembly.
 

Putting it all together went fine, until I added the cylinders. There was some interference between the bottoms of the cylinder skirts and the conrods. I knew the skirts were a bit long, so was half expecting this. The easiest solution was to just notch the skirts a bit. I also found a bit of filing of the “fork” to be needed for full clearance of the “ knife”.




With that bit of fettling done everything went together fine and turned freely. Time to test it on the lathe!
<a href="https://www.youtube.com/watch?v=FKHrnVHdSF0" target="_blank">http://www.youtube.com/watch?v=FKHrnVHdSF0</a>
<a href="https://www.youtube.com/watch?v=iZiY2WtUEyM" target="_blank">http://www.youtube.com/watch?v=iZiY2WtUEyM</a>

[Kim]

That's great Ron!  Exciting to see it go around and around like that! 

Kim

[RReid]

Thanks Kim. I think it's both fun and also beneficial that it's so easy and convenient to run it off the lathe, verifying things stage by stage.

[90LX_Notch]

Ron-

I’ve been following along quietly in the background.  I can’t wait to hear it run.

-Bob

[RReid]

Thanks for your interest, Bob! I'm looking forward to hearing it run too, but it's gonna be a while yet. Luckily it's such an interesting and fun project for me that I don't tend to suffer much "get-done-itis"!

[crueby]

Excellent! All looks to be moving smoothly!

[Roger B]

     

[RReid]

Thanks Chris! Thanks Roger!

A few little bits for the 2-Bits. Exhaust valve stems, spring retainers, and springs & e-clips (store bought). I will either make and solder on valve heads to these stems, or try turning one piece valves from SS screws, a la Roger B.

[RReid]

The flywheels on this engine are designed to mount inside the crankcase, screwed to the crankshaft webs which snuggle into a recessed cavity in the flywheel. I'm hoping to get away with only one, to preserve the visibility into the open side of the crankcase as much as possible, but we'll see. The best candidate I had on hand was one of a pair of cart cast cart/dolly wheels I picked up on the last trip to my favorite salvage yard. The OD is good, just a bit over what's needed, but it would need a new center put in to fit it to the crankshaft, and the shape of it means the OD of the recessed portion is larger than I'd like, giving up a fair chunk of rotating mass. To be honest, the thing turned out to be a bit of a boondoggle and I may not even use it, but it will at least serve as a prototype!


The new center started as a rusty old steel rivet picked up off the ground along the Feather River on a camping trip a couple of years ago. Even though it was somewhat work hardened, I managed to lobotomize it for my purposes.


Just needs to be drilled for the attaching screws.


Perhaps more interesting, I also made a start on the four little rockers that will carry the cam motion out and up to the exhaust valves. A piece of brass bar was drilled for the rocker shafts, and also a small hole to help define the shape of the rocker head.


The rest of the job is all hacksaw and files. Here's a couple of shots showing the first one doing what it's supposed to.

[Kim]

... To be honest, the thing turned out to be a bit of a boondoggle and I may not even use it, but it will at least serve as a prototype!

Hmm... Looks like a pretty respectable fly whee to me! Why might you not use it?
(Inquiring minds and all... )

Kim

[RReid]

Hi Kim. The flywheel is OK, but somewhat compromised in weight because the "well" or recess that the crank web fits into is much larger in diameter than it should be per design. This is due to the existing shape of the cast wheel I started with. It will be a relatively small and light flywheel anyway, even when made to the drawing, so giving up weight for not a good reason seems a waste and counter to my desire to get by with just one if possible. I can get a couple of 1/2" x 2 1/2" discs of mild steel from McMaster for not too much money, which seems now to be a better approach.

The other reason is that it is just not "Right".

[Kim]

Hey Ron,
Yes, that makes a lot of sense.  You want it to do the job for you!  And especially "...it's just not right."  When you're spending this much time and effort on something, it's important that it feels right to you!

Kim

[RReid]

I've been continuing to piece together the valve train bits. Here can be seen the two rear rockers, their pushrods, and the two brass bushings that support those pushrods between the rockers and the cams. Notice that the pushrods overlap, one just behind the other to meet their respective cam. The two cams could be made individually and stacked, but I'm planning to try making them as one piece.


Those pushrod bushings are located by a shallow slot and fastened from behind with a 2-56 screw each through the crankcase cover.


A shaft was turned from 12L14 to carry the cams, the cam gear, and the points cam. All the shafts are generously over-long at this point, and the brass parts still need final shaping and prettifying as well.


The larger end runs on an Oillite bushing in the case cover, while the smaller end will also run in one that will be part of the gear cover/breaker points plate. That plate will be fastened via brass stand-offs soldered to the pushrod bushings. A drawing may help this make more sense.


Finally for today, the blank for the pair'o'cams. The brass is just a backstop. Since the part is clamped pretty near the edge of the chuck jaws a backstop helps in getting it set-up.