First time I have ever seen a disconnected connecting rod on the other side of the crank shaft

rsv1cox Tue Jan 18, 2022 5:08 pm

In the past ten years I have bought over 600 glow model engines, over half of them disaster's that I have disassembled that had been used, abused, and put away wet. I searched them out.

But I have never seen this:

First time I have ever seen a disconnected connecting rod on the other side of the crank shaft Dscn1624

First time I have ever seen a disconnected connecting rod on the other side of the crank shaft Dscn1623

First time I have ever seen a disconnected connecting rod on the other side of the crank shaft Dscn1622

I was wondering why the crank would turn but the piston would not move. Broken connecting rod I thought, rather common. Could still be broken, I have not fully taken it apart yet but there are no broken parts laying in the bottom of the case.

The upside of buying these old engines, you never know what you're going to get, and I have seen some doozies. Keeps life exciting. Smile

And..............and it's just laying on the vice.

balogh Tue Jan 18, 2022 5:17 pm

Bob, with the backplate removed, even old and fairly used COX pistons allow the big end of the conrod to slip off the crankpin. With the balljoint loosened up and the bottom end worn slack, the piston on the TDC will allow this to happen and you can push the piston out through the cylinder top without removing the cylinder...seen that been there done that.

The COX crankcases have the groove machined in them around the track of the big end that keeps the rod on the pin - except where the cylinder screws in the case, as we know.

I wonder if the same groove is also there Bob in the engine you found with the rod off the pin.without the groove znd with a worn backplate the rid may have slipped off in a worn engine....or maybe the previous owner tampered with the rod when the backplate was removed, and replaced the backplate after the big end slipped off the pin, without puttong it back..?

rsv1cox Tue Jan 18, 2022 5:34 pm

balogh wrote:Bob, with the backplate removed, even old and fairly used COX pistons allow the big end of the conrod to slip off the crankpin. With the balljoint loosened up and the bottom end worn slack, the piston on the TDC will allow this to happen and you can push the piston out through the cylinder top without removing the cylinder...seen that been there done that

Your right Andras, but the backplate on this Wen Mac is snugged up tight to the cranks pin. no way it's coming off on its own. The piston is stuck at TDC, I'm soaking it in light oil. I'm betting the con rod is broken. Wiil know more tomorrow when I take it apart.

First time I have ever seen a disconnected connecting rod on the other side of the crank shaft Dscn1625

roddie Tue Jan 18, 2022 6:22 pm

Maybe the P.O. tried to force the stuck piston.. and snapped the rod in the process? They may have removed the backplate and discarded the broken piece before reinstalling the backplate? It is strange though.. Huh...

Even at TDC, you should still be able to see what's left of the rod.. if in fact; it broke at the crank-pin end.

Marleysky Tue Jan 18, 2022 8:31 pm

I am gonna guess that you have a broken end on the con-rod. Here is a picture o one with the back-plate removed, the cylinder at TDC and the con-rod off of the pin on the crank. Doesn't leave much room for the round hole to hide in front of the crank as shown in your picture. The con-rod does fall off the connecting pin at any point inside the case, the threaded back-plate hold the rod on the pin. No groove like on the Cox's,

First time I have ever seen a disconnected connecting rod on the other side of the crank shaft Dscn1113

rsv1cox Wed Jan 19, 2022 10:59 am

Yes, broken con rod right at the pin. What I couldn't understand was how the bulk of it got wedged behind the crank.

Pressed off the crank, no piston rod to worry about and dropped the piston out the bottom. Back in the parts cleaner and polished the cranks journal.

First time I have ever seen a disconnected connecting rod on the other side of the crank shaft Dscn1628

First time I have ever seen a disconnected connecting rod on the other side of the crank shaft Dscn1626

First time I have ever seen a disconnected connecting rod on the other side of the crank shaft Dscn1627

I had a spare piston. Pressed the roto-matic starter back on. Same problem as with the other one, wouldn't rotate in the clockwise direction. Parts cleaner and light oil cleaned it up.

First time I have ever seen a disconnected connecting rod on the other side of the crank shaft Dscn1630

First time I have ever seen a disconnected connecting rod on the other side of the crank shaft Dscn1631

First time I have ever seen a disconnected connecting rod on the other side of the crank shaft Dscn1629

NEW222 Wed Jan 19, 2022 5:49 pm

Another very nice engine there. Good job, and very nice that you had a spare piston.

getback Thu Jan 20, 2022 6:33 am

That is pretty wild you would not think it would happen , from the look of the CS web it has a lot of bevel to the back side and i would say at 10K or so Rs it could get back there at the right stroke . Did that sound like I know what I an talking about at 7:30 AM ? Snowman

rsv1cox Thu Jan 20, 2022 7:03 am

getback wrote:That is pretty wild you would not think it would happen , from the look of the CS web it has a lot of bevel to the back side and i would say at 10K or so Rs it could get back there at the right stroke . Did that sound like I know what I an talking about at 7:30 AM ?

You lost me at "CS web" Eric Smile

, but the rest of it sounds great. I agree, probably turning RPM's pretty good and at the right moment got caught up behind the crank. The hole end was just demolished.

getback Thu Jan 20, 2022 8:54 am

rsv1cox wrote:
getback wrote:That is pretty wild you would not think it would happen , from the look of the CS web it has a lot of bevel to the back side and i would say at 10K or so Rs it could get back there at the right stroke . Did that sound like I know what I an talking about at 7:30 AM ?

You lost me at "CS web" Eric , but the rest of it sounds great. I agree, probably turning RPM's pretty good and at the right moment got caught up behind the crank. The hole end was just demolished.

Crank Shaft Web = CS web

rsv1cox Thu Jan 20, 2022 9:17 am

getback wrote:
rsv1cox wrote:
getback wrote:That is pretty wild you would not think it would happen , from the look of the CS web it has a lot of bevel to the back side and i would say at 10K or so Rs it could get back there at the right stroke . Did that sound like I know what I an talking about at 7:30 AM ?

You lost me at "CS web" Eric , but the rest of it sounds great. I agree, probably turning RPM's pretty good and at the right moment got caught up behind the crank. The hole end was just demolished.
Crank Shaft Web = CS web

Sounds like a new internet web-site Eric, if I can find it, I will have to log on. Smile

The piston was out of an old Testors pipe-bomb, perfect pit and great compression. It will go back in the P-26. Wish I could find one with the throttle option as on my first one.

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First time I have ever seen a disconnected connecting rod on the other side of the crank shaft

First time I have ever seen a disconnected connecting rod on the other side of the crank shaft

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Re: First time I have ever seen a disconnected connecting rod on the other side of the crank shaft

Re: First time I have ever seen a disconnected connecting rod on the other side of the crank shaft

Re: First time I have ever seen a disconnected connecting rod on the other side of the crank shaft

Re: First time I have ever seen a disconnected connecting rod on the other side of the crank shaft

Re: First time I have ever seen a disconnected connecting rod on the other side of the crank shaft

Re: First time I have ever seen a disconnected connecting rod on the other side of the crank shaft

Re: First time I have ever seen a disconnected connecting rod on the other side of the crank shaft

Re: First time I have ever seen a disconnected connecting rod on the other side of the crank shaft

Re: First time I have ever seen a disconnected connecting rod on the other side of the crank shaft

Re: First time I have ever seen a disconnected connecting rod on the other side of the crank shaft