Cox .049 Connecting Rod Irregularity?

First year TD 049/051 engines had the lube hole in the connecting rod. I have a couple of TD engines like that. Is that a thin wall #4 or #5 cylinder?

I second to Jason, I also have a NIB crystal boxed TD049, must be one of the first production runs, with the small oiling hole in the large end of the rod, the venturi does not have the screen yet (so must be pre-1973) but the cylinder is a tapered, stepped walled one with no millings of the top fin for the wrench...the color of the con-rod is kinda white-ish...must be a different alloy than later generation con-rods

While on this topic which .049 had aluminum rods? I have one somewhere.

I have a Thermal Hopper and its conrod is suspiciously white...I have never heard of aluminium conrods in COX engines though..

Jason_WI wrote:First year TD 049/051 engines had the lube hole in the connecting rod. I have a couple of TD engines like that.  Is that a thin wall #4 or #5 cylinder?

Not too sure yet as there is no number on the cylinder, and the piston is seized in the cylinder right now yet, so I cannot see the porting. I will get it apart shortly, hopefully and report back.

If there are 2 bypass ports each having 2 booster grooves - these are typically visible if seen from the cylinder bottom - then it must be a TD cylinder

gkamysz wrote:While on this topic which .049 had aluminum rods? I have one somewhere.

 ace Bug Jr. .049 (0.8 cm³)

Manufactured in 1953 (#370)

While the standard Space Bug had a large aluminum tank, the Junior came with a smaller plastic fuel tank.

Like the early Space Bug above, these two engines still have the glow head with the smaller thread diameter. They also have the original three piece piston with an aluminum conrod. The reed valve system consisted of two reeds in tandem, one having a thickness of approximately 0.05 mm (1/500") and the second one being about 0.08 (1/300") mm thick.

As a cost reduction measure the cylinder of the Space Bug Jr. has only one bypass port.

Engines like these were used in the Thimble Drome control line models, for example the first issues of the TD-3. The last version of the TD-3 came with the then brand new Babe Bee engine.  New is that cly use a small diam. plug ? i have seen this on Space Bugs and Jrs.

Ok. So, I was able to gently press the piston out, and after doing so, I was able to get a better visual of the cylinder. It had only one bypass in it, making it a #2 cylinder with open exhaust ports, then after a quick wipe down, saw the #2 in the side..... Now, as for the piston, how can one ID it to see if it was from a TD? Just asking, as after the disasembly, I put the piston in the cylinder, and put a drop of oil and it does move freely as it should. I then assembled the piston cylinder to the crankcase and rotated it also with no problems. If it was a TD .049 piston, would it still work in a #2 cylinder as thet piston should have a taper to it?

All 049 size pistons are the same except some made for early TD engines had a tapered design for matching tapered TD cylinders. Later pistons and cylinders even fot TD-s had no tapered design thus these are fully onterchangeable. The only later COX engine with tapered bore was the Venom as far as I know.

From Wikipedia https://en.wikipedia.org/wiki/Cox_model_engine
Cox 049 Cylinder cross-sections

Cox Venom Cylinder
Referring to the Cylinder Cross-sections above:

depicts a thin wall Tee Dee .049 cylinder with dual booster ports on the bypass port.
is a late model thick wall cylinder with slit exhaust and a single bypass booster.
is a Black Widow #1 cylinder with no bypass booster with a stepped wall.
is a pre-1955 cylinder used on early Space Bug, Space Bug Jr, Thermal Hopper and Strato Bug. Note how the thread diameter for the glow head is much smaller. No engines produced after 1955 used this cylinder.

I had a TD .049 older version that had a 3 piece piton set in it and oiler hole ( but blew it up at 22K ) can't say it was original but seems i have heard the fist ones had it .

So I just went and took a peek at the piston. It is not a 3 piece piston, it is the standard crimped in variety. Also while apart, I took my cheap digital calipers and got the following readings. At the top edge of the piston measured .4055", and at the bottom edge it came in at .406". I did not have another round quickly to measure, but may do so tomorrow.