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General control line discussion => Open Forum => Topic started by: Clancy Arnold on July 18, 2009, 05:04:52 PM

Title: Rare Cox piston
Post by: Clancy Arnold on July 18, 2009, 05:04:52 PM

I purchased a set .010, .020 and .049/.051 Cox Rod resetting tools.

Tried the .049 size one first to get a feel for doing the resetting.  Did two engines.  Hay this is easy.

The third engine had .011 end play so it deffinitely need resetting.  Only one problem, the reset tool would not clear the rod.  Got out my magnifier and a bright light and found that this was a different type of piston.  The rod is retained by a stamped sheet metal part setting in a grove in the piston.  Contacted Marvin Denny and told him that I was considering asking Larry Renger what did I have.  Marvin agreed.

Sent Larry an email and described the piston.  Larry stated that it is a rare Cox piston from a very early production run. 

Larry asked if I had a W head to go with it.  I do somewhere!!

Clancy

Title: Re: Rare Cox piston
Post by: Clancy Arnold on July 18, 2009, 05:57:45 PM

Since posting this I read a writeup by Warren Ledbetter of AU that it actually has three parts.  The piston, sheet metal retainer and a wire clip ring that snaps into a grove on the inside of the piston.

Clancy

Title: Re: Rare Cox piston
Post by: Jim Thomerson on July 19, 2009, 01:14:10 PM

My Spacehopper has that kind of piston.  I discovered it just as you did. I replaced the piston with a modern piston and the engine runs fine.  So I would guess that that kind of piston was used in Space Bugs, Jr. Space Bugs, and Thermal Hoppers as well.  Maybe the present piston came in with the TD and the Baby Bee.

Title: Re: Rare Cox piston
Post by: Garf on July 19, 2009, 02:19:22 PM

I have serveral of those too. I think they came in the earliest engines. I used them in my attempt to build a diesel engine because the rod is stronger.

Title: Re: Rare Cox piston
Post by: George on July 19, 2009, 09:06:43 PM

Here's one of those type pistons that I ruined years ago by using the wrong reset tool.

Title: Re: Rare Cox piston
Post by: Mike Scholtes on July 20, 2009, 10:53:22 PM

As a Space Bug Jr owner since 1955 I can say, Yep!

Title: Re: Rare Cox piston
Post by: George on July 21, 2009, 10:30:02 PM

Quote from: Mike Scholtes on July 20, 2009, 10:53:22 PM

As a Space Bug Jr owner since 1955 I can say, Yep!

My first "brand new" engine was a Space Bug Jr. I remember having to drill intake holes in the firewalls. Of course the Space Bug and the Thermal Hopper had the same problem. Never had the cage mount for the TH.

George

Title: Re: Rare Cox piston
Post by: Mike Scholtes on July 21, 2009, 11:31:19 PM

And I still HAVE that Space Bug Jr, and the Firebaby it was mounted on. It served yeoman duty in sport FF models and a slew of half-A CL models, including the Wing Ding machined balsa kit, which (no surprise here) I still have. All with holes drilled in the firewall for the intake. I think us model builders all have a variant of the same mental illness that causes us to keep stuff for 50 years that we have not used for the last 45 years. Did I mention the Green Box Nobler kit I have had since 1963, that I bought at the 1963 Nats in Los Alamitos?