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Old Oct 02, 2012, 09:54 PM
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Piston re-setting, when is it time?

Simple enough, when is the the right time to re-set the pistion in cox engines?

How much play is too much?
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Old Oct 02, 2012, 11:32 PM
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Neenah, Wisconsin, United States
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Anything over .010 is time to reset back to ~.002". Depends on the RPM and nitro content you are using on the frequency of needing to reset the piston. Seems like new pistons require a reset after a few runs until the ball/socket of the piston is work hardned.
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Old Oct 03, 2012, 05:24 AM
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This may be a stupid question, but what is " re-set ".I have no idea what it means, i'm very interested because I have a few Cox 049 engines.

Thanks
Joe
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Last edited by Joe Blow; Oct 03, 2012 at 05:25 AM. Reason: spelling
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Old Oct 03, 2012, 06:47 AM
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Quote:
Originally Posted by Joe Blow View Post
This may be a stupid question, but what is " re-set ".I have no idea what it means, i'm very interested because I have a few Cox 049 engines.
Joe, it is not a stupid question. You need a resetting tool see:

http://coxengines.ca/cox-.049-piston-reset-tool.html

You put the piston upside down with connecting rod into the metal cup holder. Take the fluted rod, place flute end over the piston's ball joint. Give a light tap with a hammer, until the connecting rod ball end play is removed. This is called "resetting the piston socket".
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Old Oct 03, 2012, 08:42 AM
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Quote:
Originally Posted by OkiThumper View Post
Joe, it is not a stupid question. You need a resetting tool see:

http://coxengines.ca/cox-.049-piston-reset-tool.html

You put the piston upside down with connecting rod into the metal cup holder. Take the fluted rod, place flute end over the piston's ball joint. Give a light tap with a hammer, until the connecting rod ball end play is removed. This is called "resetting the piston socket".
Thanks for the answer, and yes I have seen this slop in the cup and ball in some of my older engines and now I know how to fix it.

Thankyou
Joe
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Old Oct 03, 2012, 02:05 PM
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Joe, your question is an ignorant question. By asking it, you receive a cure for your ignorance. An example of successful self medication.

I rotate the crank until the piston is top dead center, then I wiggle the propeller. If I can wiggle it very much without moving the piston, I figure it is time to reset. "very much" is a matter of experience
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Old Oct 03, 2012, 06:46 PM
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As a side note, it is also best to rotate the fluted rod a little each time you tap the joint. The fluted rod obviously has a missing area aroung the rod and that can cause the joint to become out of round, in other words ruin the piston.

George
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Old Oct 03, 2012, 11:42 PM
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Another side note is on occasion I've tapped it a little snug. Apparently no harm was done as after a run or two, it loosened up.
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Old Oct 06, 2012, 07:54 AM
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I usually reset mine around 7pm.
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Old Oct 06, 2012, 08:41 AM
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I got my reset tool some time back in the early to mid 1970's, it was an Ace R/C item, still have the tool. Now, can't remember if it was a Dale Kirn's Kirn-Kraft item. (History of Dale is at:

https://www.modelaircraft.org/files/KirnDale.pdf )
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Old Oct 06, 2012, 01:05 PM
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I have two reset tools, one is hexigon stock with Kirn Kraft stamped on it, the other is round with no identification. I got the kirn tool back in or about 1975

George
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Old Oct 06, 2012, 03:06 PM
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I just looked into my flight box tool box. I have the round one with no ID. The ones Bernie at Cox International sells are a nicer ones, come with a cup to minimize what I gather is piston top distortion. So far I've made good with the tool itself. Do my tapping on a hard metal surface.
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Old Oct 07, 2012, 04:59 PM
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Here are my Reset Tools... Notice that the working end of the kirn kraft tool has been reduced in diameter. This is done to protect the piston skirt from being hit by the tool if it is allowed to lean while being struck by the hammer. The piston anvil was turnned on a lathe and is used to kepp the piston from being forced out of round and it makes holding everything easier while resetting the rod.

George
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Old Oct 09, 2012, 02:05 PM
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Here is my reset tool. It is not turned down like George's deluxe version and I don't have the anvil bucket, but it works.
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Old Oct 10, 2012, 07:13 AM
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Quote:
Originally Posted by Curare View Post
Simple enough, when is the the right time to re-set the pistion in cox engines?

How much play is too much?
My experience and surely others is that the original Cox resetting tool is not really tht. I bought better ones forgot the name but you'll find that on ebay.
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