twin bee on ebay...can't figure this one out

aungmyatoo wrote:Abit risky to buy these twins on ebay!

I agree with you on that. I am not bidding on this one.

Phil

Well............. The seller DOES have a 100% approval rating.

As for me, I'm curious but not interested.

SD

I find this one a little unusual.

Without seeing the inside and the crankshaft (or its components), I find it difficult to comment as I have witnessed many ingenious miniature (and I mean miniature!) engine contructions.

However, I have looked at the pictures and the crankcase body looks longer than usual - maybe it is my eyesight!

I agree with Ian.

The crankcase body is made of longer than usual extruded aluminum suggesting yet another experimental engine from Cox.

SD

I bet it runs. He sold a cute twin Pee Wee a couple months ago.
http://www.ebay.com/itm/UNKNOWN-PEE-WEE-TWIN-CONTROL-LINE-FREE-FLIGHT-MODEL-AIRPLANE-ENGINE-NEW-/121062538078?nma=true&si=LbVW0KkT2S2JXbHz%252F513%252BS1UgIM%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557
edit- On second thought, it's gotta just be a paperweight.

SuperDave wrote:I agree with Ian.

The crankcase body is made of longer than usual extruded aluminum suggesting yet another experimental engine from Cox.

SD

From the head on view, it does look like it was made from a standard crankcase extrusion. Imagine those came in as 10 - 15 foot bars, so it wouldn't be difficult for someone with access to the raw material to cut off a bit longer chunk.

However, has anyone read/heard any story/rumor/whiff of a rumor of Cox prototyping an opposed twin? It may be this wasn't so much an official experimental engine as a back door/tool room special done by someone in their spare time.

The only twins I will buy are the geared ones.

Something looks funky with it on the added cylinder. No way a standard crank was used as the crank pin is not long enough. Seller states both pistons move in and out at the same time. The only way for that to happen is if another crank jornal was added at 180 degrees off the other one.

Shelf queen at best and looks like it might get spendy with 6 days left.

That is a cool peewee.

Phil

I asked them to take a pic with the tank off.... as it would help their sale as well as out curiosity...

Jason_WI wrote:...Seller states both pistons move in and out at the same time. The only way for that to happen is if another crank journal was added at 180 degrees off the other one...

You're right Jason, that's the only way it could possibly make draw and inject fuel. It could work if the venturi size isn't a bottleneck.

SuperDave wrote:I agree with Ian.

The crankcase body is made of longer than usual extruded aluminum suggesting yet another experimental engine from Cox.

SD

I think its safe to say it's definitely experimental, but definitely not Cox.

Mark Boesen wrote:

SuperDave wrote:I agree with Ian.

The crankcase body is made of longer than usual extruded aluminum suggesting yet another experimental engine from Cox.

SD

I think its safe to say it's definitely experimental, but definitely not Cox.

Ok, after looking at case a second time I agree, it is definitely longer. However I've never heard of Cox ever playing with twin cylinders. Hopefully Mud will comment. I do believe that particular size of extrusion the case is made out of was available.

It broke $100 overnight.
Phil

I looked at the inside of the crankcase when I cleaned the engine. Removing the tank shows a black disc with one rod connected on each side. I will not disassemble the engine further. You cannot see the crankshaft.

I would still like to see a pic though

I am not buying it!

[quote="ahrma_581"]

SuperDave wrote:
From the head on view, it does look like it was made from a standard crankcase extrusion. Imagine those came in as 10 - 15 foot bars, so it wouldn't be difficult for someone with access to the raw material to cut off a bit longer chunk.

The second photo from the left seems to show the front cylinder on the wrong side, but comparing this with the front view, the other cylinder seems on the wrong side. (compare needle valve positions) It would seem like if you were doing this from bar stock, you might profile the non-cylinder sides to save a little weight, but it would be a real hassle to do this in front of and behind the cylinders.

Perhaps two cases were cut diagonally, tig welded together, then polished up to hide the seam. I have some aluminum brazing rod (no not the the nasty 3-in-1 stuff) that might be able to do this as well.

The spacers under the cylinders are interesting. I wonder if perhaps custom rods with demountable big-ends were used so that a one-piece crank could be used. That might require a little higher deck height than the stock extrusion. Maybe this was just done so that stock extrusion could be used, as a saddle would be needed for the wrong-side cylinder to mate to, so might as well put a spacer on the other one to make it look like it belongs that way.

On Edit: Zoom is my friend. The photos on the listing are fairly high res, and by zooming in on this one:


I can just make out the lines where two cases were cut in a Z shape (a z with right angles) and mated. See the faint horizontal line just behind the front cylinder, and just ahead of the rear cyclinder, and the heavy scratch down the middle of the case, that stops clear of the two horizontal lines. VERY clean workmanship from the look of it.

Yep, I can see it now that you point it out.

For those who can't see the whole image on your monitor, right click on the picture and select "View Image" them click it again to enlarge.

Holy cow. it topped $260 and it isn't over yet!

Phil

Is this possibly where they two were attached? I can quite clearly see a zig zag line. I put in arrows where it gets more obvious. Hope I am not crazy.

I think the way that it was put together was cutting it from one corner to the other kinda like in this picture

I think Rolla is right.

The step cut would be easier than a diagonal cut if a mill was involved.

Coincidentally most small lathes can use an end mill in this manner, with a small part fastened in the tool holder.

A step cut also facilitates line up.

Now the work to make the seam near invisible is something entirely different.

Phil

Im still putting my $$$ on the cross cut... Not that tough to do some simple math, set the engine block in the vise at a 45 degree angle and mill down to finished dimension