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September-2020
sosam117's

"Traded an electric charger for this "Complete" (original) Cox Thimble Drome Olympic .15 engine. Right corner is photo as received."



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Post  Gordinir8 on Sat Aug 15, 2020 6:12 am

One of my engines has a play and I need to buy a reset tool to make it true again it but I noticed that if you want to speak with numbers it's not very easy to hold this tiny piston and measure it. Things can be very easy with a piece of fuel silicone tube and a toothpic! This way you can keep the Conrod against the piston while at the same time you can compress it with the caliper or with the micrometer. In this case play is 055mm or .021in


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Last edited by Gordinir8 on Mon Aug 17, 2020 7:34 am; edited 2 times in total
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Post  balogh on Sat Aug 15, 2020 7:42 am

A smart setup! I cannot measure the play though just keep knocking until there remains a hardly tangible one when you pull on the rod. I also spin the rod around to make sure it doesn't stick to the edge of the cup
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Post  Iceberg on Sat Aug 15, 2020 9:46 am

Interesting setup!
Please humor me. What is the perfect piston play?

Thanks
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Post  Cribbs74 on Sat Aug 15, 2020 10:21 am

.002 is the number that is usually thrown around. Enough for the oil to creep into. To be honest though it isn’t super critical. At least not in my experience. I do resets mostly for longevity and not for performance. I measure play by feel. Some are tight and some are probably just right. After being run they settle out pretty even with each other.

I like the apparatus you made to measure.
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Post  Marleysky on Sun Aug 16, 2020 11:50 am

How do you eliminate that Photobucket Black Stripe across your pictures?? [url=https://servimg.com/view/19103929/1131]Piston resetting  Acd45910[/url

Kinda ruins the view.
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Post  Gordinir8 on Sun Aug 16, 2020 12:24 pm

By paying subscription I guess but I am not willing to do.
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Post  Surfer_kris on Mon Aug 17, 2020 3:57 am

Just attach the original image to this forum instead.
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Post  Gordinir8 on Mon Aug 17, 2020 4:22 am

Are you sure? I thought that image has to be host somewhere! Gonna try it thanks.
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Post  Surfer_kris on Mon Aug 17, 2020 5:05 am

It will technically be hosted on the forum (or another service "servim"?), and everyone will be able to se it here. Just use the "Host"-button with a tiny floppy drive disc on it.
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Post  Gordinir8 on Mon Aug 17, 2020 5:35 am

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Post  roddie on Mon Aug 17, 2020 9:33 pm


Hi, I saved your photo and it previews fine for me with Windows Photo Viewer.

I have the Cox .049 reset tool. When I use it, I place the "cup" on a very solid surface. An anvil usually. I like to use a small hammer and tap very lightly on the tool; checking the ball/socket clearance after each tap. Being careful NOT to get heavy-handed; I rotate the tool approx. 120 degrees after each tap.. until the rod will not drop by gravity.. but will move if shaken. If your "setting" feels a little tight.. it might be fine. Some people here have mentioned that they set theirs' on the snug-side.

I'm led to understand that the ball-socket joint need only be reset "once".. as part of a break-in measure. Under normal operation, it shouldn't need resetting again and should hold it's setting due to work-hardening.
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Post  happydad on Tue Aug 18, 2020 1:48 am

roddie wrote:

Hi, I saved your photo and it previews fine for me with Windows Photo Viewer.

I have the Cox .049 reset tool. When I use it, I place the "cup" on a very solid surface. An anvil usually. I like to use a small hammer and tap very lightly on the tool; checking the ball/socket clearance after each tap. Being careful NOT to get heavy-handed; I rotate the tool approx. 120 degrees after each tap.. until the rod will not drop by gravity.. but will move if shaken.  If your "setting" feels a little tight.. it might be fine. Some people here have mentioned that they set theirs' on the snug-side.  

I'm led to understand that the ball-socket joint need only be reset "once".. as part of a break-in measure. Under normal operation, it shouldn't need resetting again and should hold it's setting due to work-hardening.

roddie: That is exactly how I do my piston resetting. Always being sure to rotate the tool, and light to medium hits with a ball peen hammer. Anyone remember those??  My dad used those when putting rivets into sheet metal. WW2.  He was a single parent before he met my mom.

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Post  Gordinir8 on Tue Aug 18, 2020 4:05 am

Thanks for info, this is what I have in mind also. Tool is on its way.
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Post  gasface on Sat Sep 05, 2020 4:15 pm

Some really great info thanks. Very Happy
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Post  Tee Bee on Mon Sep 07, 2020 7:12 am

That’s a neat measuring technique! Thanks for sharing.
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