Author Topic: Fuel for Cox 1/2a engines (Read 2870 times)

DanielGelinas · « **on:** March 19, 2012, 07:40:19 PM »

Just bought some sig champion 35% nitro for my little 1/2a cox engines.
Is 20% (10syn 10castor) oil content enough? I assume not.
How muchore castor do you add?
Thanks!!

-Dan

kenneth cook · « **Reply #1 on:** March 20, 2012, 05:54:16 PM »

Hi Dan, that is my fuel of choice, I never added additional castor to my Sig fuel. I also never suffered a failure due to it either. That fuel runs very well in Cox engines. It is hard on Cox plugs on that percentage nitro. For plug longevity you need to add additional shims. I typically use this fuel in all of my 1/2A combat engines including Cox. The recommendation is to have fuel of 20% oil content. The only ball socket failure I ever had on a Cox engine was using a Black Widow. This was my fault not resetting the ball. I find that the Sig fuel stopped all problems of reeds gumming up after they sat dormant as well. I'm not saying not to add additional, I just don't feel a need to do so. Ken

DanielGelinas · « **Reply #2 on:** March 20, 2012, 07:18:20 PM »

Thanks Ken!
What do you mean by 'resetting the ball'

thanks

-dan

Elwyn Aud · « **Reply #3 on:** March 20, 2012, 07:44:02 PM »

The piston/rod joint on a Cox .049 is a ball and socket affair instead of a wristpin like you find on most engines. After enough use the rod starts to get loose and you have to reset it with a special two piece resetting tool.

kenneth cook · « **Reply #4 on:** March 21, 2012, 05:54:12 AM »

Dan, eventually the connecting rod will poke a hole out of the top of the piston. While one of your engines is apart, hold the piston and grab the rod. Push it in and pull it back out and check to see if there is play. The play should be only about .001" -.003". This is a best guess at that as you do it more by feel. I've ruined a few until I learned how to do it properly. Larry Renger explained it. I used the cup which comes with the tool. Others have claimed the cup ruined the piston due to it mushrooming the head. The key is that you don't want any bounce while your tapping the tool. Square contact on the tool and repetitive (light but firm) hits constantly rotating the tool is key. This evenly sets the sides around the ball. The area that is correctly being bent back into shape around the ball is now work hardening. This area is less likely to open up again . The problem is YOU DON"T WANT TO OVERSET THE SOCKET. This will ruin the piston. It takes me several minutes to do this. Yes, one big hit would be nice but it doesn't work like that. I have a large anvil that is bench mounted. A solid concrete surface would be adequate as well. I then rotate the con rod to in all directions to check for tightness. http://www.ebay.com/sch/i.html?_from=R40&_trksid=p5197.m570.l1313&_nkw=cox+.049+reset+tool&_sacat=See-All-Categories Here is one like I use. This restores the timing giving you power back into the engine as well. Ken

DanielGelinas · « **Reply #5 on:** March 21, 2012, 08:48:17 PM »

Thanks Ken...I understand. I remember when I was young there was some play between the rod and piston.
The engines I have have just barely been broken in. I assume this has to be done after many flights?
Thanks,
-dan

kenneth cook · « **Reply #6 on:** March 22, 2012, 04:56:39 AM »

Dan, it can be done from the start if the play is excessive. The production Sure Starts are notorious for this play and if not dealt with, it will self destruct. I've had used older engines with little play, and some with a fair amount. What I did notice though is that some are quite hard while others are easier to set. Using this tool and a Davis Diesel .049 devarnishing brush I've seen some really good performance out of my engines. Ken

DanielGelinas · « **Reply #7 on:** March 23, 2012, 12:04:11 PM »

Thank Ken, I'll order the tool as I do have one of the new sure start engines.
-D

Bill Little · « **Reply #8 on:** April 10, 2012, 01:37:36 PM »

Hi Dan,

Late getting in, but I totally agree on getting, and learning to use, the re-setting tool. I check ALL of my Cox engines before I run them to see if the connection needs to be tightened up.

BIG Bear
RNMM/AMM

Author Topic: Fuel for Cox 1/2a engines (Read 2870 times)

DanielGelinas

Fuel for Cox 1/2a engines

kenneth cook

Re: Fuel for Cox 1/2a engines

DanielGelinas

Re: Fuel for Cox 1/2a engines

Elwyn Aud

Re: Fuel for Cox 1/2a engines

kenneth cook

Re: Fuel for Cox 1/2a engines

DanielGelinas

Re: Fuel for Cox 1/2a engines

kenneth cook

Re: Fuel for Cox 1/2a engines

DanielGelinas

Re: Fuel for Cox 1/2a engines

Bill Little

Re: Fuel for Cox 1/2a engines