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Post  Yabby Wed Feb 01, 2023 2:30 am

This might be a bit pedantic, but I noticed in the Piston Reset instructions there is nothing mentioned about putting the big end back onto the crank pin the same way it came off. Often the piston reset is done for the first time after the engine has been 'run in' ( break in ) or shortly after. No matter, whenever taking a piston out and putting the same one back in again.

My thinking is, the big end is also being 'run in' and formed to fit during the 'run in' such that the two marry up nicely to take into account any slight deviation in manufacture. Maybe I need to "get out more" lol!  but when returning parts back into an engine I have always done so with the parts the same way around etc. as they came out to maintain the engines tolerances and "run in" state of the parts and engine where possible.

Especially an engine that revs like a Cox TD and the effect of not putting them back in the right (same as they came out) way around may possibly be worse on smaller engines like the 010 and 020 where the revs are soo high and the tolerances so tight and there is little between correct and loose or worn out.

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Post  GallopingGhostler Wed Feb 01, 2023 5:59 am

Do you mean to realign the rod onto the crankshaft pin in the same orientation with the same side in? I'd think that over time, the cylinder tends to wear oval toward the top due to the side action of the connecting rod. Piston is free to rotate until it wears slightly oval, too, then probably settles into its own orientation. So, setting the connecting rod big end same way makes sense. But those are just my impressions. Tolerances are so tight that it doesn't take much to start to lose compression.

I've never mic'd the surfaces to check wear, except in automobile engines during overhaul. But then, my model engine experiences have been totally with reed valve engines, and not the higher performance Medallions and Tee Dees. There, I just reset the piston socket clearances and put it together without bothering with piston or connecting rod orientation.

Perhaps with these engines, that to most, Cox felt that orientation was not that significant, or they wanted to increase their piston / cylinder set sales? Wink
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Post  Yabby Wed Feb 01, 2023 6:21 am

yes, i meant as you were describing. So as that the same side of the conrod big end is up against the crank pin web as was before dissasembly. I only do it, because its a habbit from building other engines. I dont know if it is significant or not but thought it was good practice and was surprised its not mentioned in the doco at all.

Its possible that it really makes no difference given I have never read anything about it. I have nothing to go on other than assumption.

I just thought like I think you were implying also, that if the big end was worn in one way and then you put it back the other way, it may tend to open it out faster especially on really high reving small 0101 and 020 TDs. But then maybe the fact nothing is written about it and nobody really has high wear rate problems it just me looking for a problem lol!

I will still do it anyway as its a habbit. Smile

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Post  GallopingGhostler Wed Feb 01, 2023 6:39 am

Yabby wrote:I will still do it anyway as its a habbit. Smile
CEF Conspiracy Theorist? Doh! Very Happy lol!
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Post  Yabby Wed Feb 01, 2023 6:45 am

lol! lol! I Love This Forum!

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Post  balogh Wed Feb 01, 2023 6:56 am

Hey Yabby,

not only the radial gap between the big end and the crankpin, but the the small "play" in the balljoint up in the piston will allow the free alignment of the conrod anywhere between fully perpendicular to the pin, and slightly slanted, when running. So,  during operation I believe the big end eyes on both sides will be slightly - even if only microscopically - chamfered by the pin, resulting in an indifference in replacing the big end with whichever eye looking forward or aft. But yes, I also tend to mark with indelible ink the side of the conrod facing the backplate, before I remove the piston. It won't do any bad to reassemble the engine to the conditions before disassembly.
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Post  rsv1cox Wed Feb 01, 2023 7:17 am

Mega piston reset tool.

Resetting Pistons P1014926
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Post  Yabby Wed Feb 01, 2023 7:46 am

balogh wrote:Hey Yabby,

not only the radial gap between the big end and the crankpin, but the the small "play" in the balljoint up in the piston will allow the free alignment of the conrod anywhere between fully perpendicular to the pin, and slightly slanted, when running. So,  during operation I believe the big end eyes on both sides will be slightly - even if only microscopically - chamfered by the pin, resulting in an indifference in replacing the big end with whichever eye looking forward or aft. But yes, I also tend to mark with indelible ink the side of the conrod facing the backplate, before I remove the piston. It won't do any bad to reassemble the engine to the conditions before disassembly.

Good explanation Andras Thumbs Up Took me a bit to think through the chamfer............. But, yes, I can see what you are saying. Interesting thought and explanation.

As you also do, I will still replace them as they were when disassembled. So small and soo fast revving, especially the tiny motors you run at times in your speed pylon racer models and they are so hard to get now, I figure anything that might hellp them not wear out is ok. Mind you, maybe Cox really knew that the chamfer is almost self healing in a way such that it doesnt matter so much as to the way around. They are amazing little engines. People sometimes say they are only toys, but they are ingenious designed and manufactured toys then. cheers sunny

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Post  getback Wed Feb 01, 2023 8:12 am

I know what ur saying But if it were needed to bee oriented in a specify way it would bee marked or known that it need to bee , I think its the Conquest that has the COX imprint on one side of the rod toward the backplate so as to bee put back that way . If they did it for that and not for others well go figure . Huh...
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Post  balogh Wed Feb 01, 2023 8:25 am

This raw sketch with intentionally exaggerated radial pin gap and ball-joint play tries to explain, that the big end eyes get chamfered, making it indifferent  which side of the conrod is facing the engine backplate, when re-assembled. Sorry for the quality of the draft

Resetting Pistons 20230210

In fact the conrod is dangling on its big end, you can try it pulling it forward and back even in a new engine with the backplate removed, so the conrod axis is swaying around its perpendicular position during engine run, leading to the chamfering...
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Post  Yabby Wed Feb 01, 2023 8:36 am

balogh wrote:This raw sketch with intentionally exaggerated radial pin gap and ball-joint play tries to explain, that the big end eyes get chamfered, making it indifferent  which side of the conrod is facing the engine backplate, when re-assembled. Sorry for the quality of the draft

Thats a great explanation Andras Thumbs Up Well thought through. I would never have seen it myself were it not for your explanation, and the drawing makes it quite clear. It makkes me think Cox really did know what they were doing in this case.

I like drawings / sketches as you have done! Thumbs Up I get a bit annoyed with some of my engineers who spend a day or more using fancy software tools to draw a rough sketch/design/idea for discussion that could be drawn free-hand on an A4 sheet of paper in an hour, and if multiple copies are needed, in the photo copier. lol! Fast, simple, efficient. Of course the time does come when the proper tools need to be used.

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Post  andrew Wed Feb 01, 2023 8:50 am

Yabby wrote:......

As you also do, I will still replace them as they were when disassembled. So small and soo fast revving, especially the tiny motors you run at times in your speed pylon racer models and they are so hard to get now, I figure anything that might help them not wear out is ok......
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The vast majority of my rebuilding experience has been with agricultural engines (tractor and combine) with a few car and truck engines tossed in.  However, since retirement, it's been mostly small engines, both two and four cycle engines for lawn and DIY use, and of course, model engines.

We had a rack in the shop set up to hold all the parts from each cylinder -- if it came out of No. 2, it went back into No. 2, same orientation, same location.  The other requirement was cleanliness -- all parts were cleaned, wiped down, then relubed for assembly.  My Father's rules were so ingrained that I still follow them today.

a--
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Post  Yabby Wed Feb 01, 2023 9:20 am

andrew wrote:

The vast majority of my rebuilding experience has been with agricultural engines (tractor and combine) with a few car and truck engines tossed in.  However, since retirement, it's been mostly small engines, both two and four cycle engines for lawn and DIY use, and of course, model engines.

We had a rack in the shop set up to hold all the parts from each cylinder -- if it came out of No. 2, it went back into No. 2, same orientation, same location.  The other requirement was cleanliness -- all parts were cleaned, wiped down, then relubed for assembly.  My Father's rules were so ingrained that I still follow them today.

a--

That makes me laugh so much Andrew. Fathers rules. lol! lol! Nearly all of my engine building when younger was bike race engines and my Dad also had rules!! lol! Especially the rules on all threads get lubricated before being used in 'Hiroshima Wonder Metal' and the Warren and Brown set of torque wrenches officially calibrated each year must be used on all bolts on the engine where the manual has a torque setting.

We had a big board in the shed that was a check list, before I could fire the bike in the street and put it on the trailer. It checked off, all lockwire spots individually, all liquid reservoirs, all external bolts had a torque wrench check, each spoke on rims was checked. Disk brake petals checked and dialled, gear sprockets and chains checked and what ratios, fork settings, pressures, fluids, damping, similar with the monoshock, and of course the chain, stringlined wheels, slicks were checked and filled with nitrogeon,.................... so many checks all on a board and all ticked off before the bike left the shed. I was very lucky to have a father who was such a great race engineer and often he finished that check list after working all night if I had crashed in practice on sat to have it ready for me on sunday.

The cleanliness was the same. If you used a tool you wiped it with a rag and cleaned it and put it back when finished, the floor was spotless, and he cleaned the bike with a little cloth from the back of the back tire to the front of the front tire, as doing this sometimes found little cracks in things that otherwise went unnoticed until something failed badly.

He had one very very firm rule also that NO intoxicated people (my friends coming by to offer advice lol! ) were allowd in the shed with the race bike and NO alcahol was allowed in the shed if the race bike was in the shed. Old Bugger I was a very lucky young man!!! Thumbs Up

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Post  rsv1cox Wed Feb 01, 2023 10:04 am

If you used a tool you wiped it with a rag and cleaned it and put it back when finished

My routine Yabby.

Dad's can be great advisors and roll-models as most of us here can testify. I remember my Dad with a great deal of respect and affection.

Great thread here. Learning something.

Bob
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Post  balogh Wed Feb 01, 2023 10:55 am

Yabby wrote:
balogh wrote:This raw sketch with intentionally exaggerated radial pin gap and ball-joint play tries to explain, that the big end eyes get chamfered, making it indifferent  which side of the conrod is facing the engine backplate, when re-assembled. Sorry for the quality of the draft

Thats a great explanation Andras Thumbs Up Well thought through. I would never have seen it myself were it not for your explanation, and the drawing makes it quite clear. It makkes me think Cox really did know what they were doing in this case.

I like drawings / sketches as you have done! Thumbs Up I get a bit annoyed with some of my engineers who spend a day or more using fancy software tools to draw a rough sketch/design/idea for discussion that could be drawn free-hand on an A4 sheet of paper in an hour, and if multiple copies are needed, in the photo copier. lol! Fast, simple, efficient. Of course the time does come when the proper tools need to be used.

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Thanks again. Yabby, for your comments.

The explanatory sketch I sent is the remainder of my design engineer self dating back to the early 1980-s, when as a fresh university graduate, I started my carrier as a design engineer of pressure vessels and air cooled heat exchangers..drawing boards and ZX spectrum "computers" instead of sophisticated Autocad and similar tools.. that part of my carrier remains the happiest, because as it evolved later into executive positions of engineering companies, I had more to do later with sales, company management and administration than with engineering...what goes around, comes around..in my year of possible retirement in 2023, I am again involved in my current position in creating conceptual design of processes and systems saving water in power plants, and selling the idea to users around the world...but COX engines have always given me lots of engineering inspirations...
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Post  batjac Wed Feb 01, 2023 12:50 pm

andrew wrote:We had a rack in the shop set up to hold all the parts from each cylinder -- if it came out of No. 2, it went back into No. 2, same orientation, same location.  The other requirement was cleanliness -- all parts were cleaned, wiped down, then relubed for assembly.  My Father's rules were so ingrained that I still follow them today.

a--

When I was rebuilding car engines for fun, I went with the two liter Pepsi bottle method.  I had one of those carrying racks that they use for stacking the bottles.  Just convenient that they hold eight bottles, so mark one opening for #1 and then place all the pistons/pushrods in the rack in their proper order.


GallopingGhostler wrote:CEF Conspiracy Theorist? Doh!  Very Happy lol!

Isn't that part of the CEF TOS?

The Hot Rod Mark
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Post  Yabby Wed Feb 01, 2023 2:58 pm

getback wrote:I know what ur saying But if it were needed to bee oriented in a specify way it would bee marked or known that it need to bee , I think its the Conquest that has the COX imprint on one side of the rod toward the backplate so as to bee put back that way . If they did it for that and not for others well go figure . Huh...

Hi Eric, good pickup Thumbs Up the marking does make you think it was meant to be a certain way around, and then why not do it for the others, as you said. I have no idea. lol! I do like Andras explanation though for why its not critical, but that said, we both put them back in the same way as they came out. i think the way the engines run for people in general and the fact people dont have wear problems etc. tells us that its not a problem.

But old habitts.

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Post  Yabby Wed Feb 01, 2023 3:07 pm

batjac wrote:
andrew wrote:We had a rack in the shop set up to hold all the parts from each cylinder -- if it came out of No. 2, it went back into No. 2, same orientation, same location.  The other requirement was cleanliness -- all parts were cleaned, wiped down, then relubed for assembly.  My Father's rules were so ingrained that I still follow them today.

a--

When I was rebuilding car engines for fun, I went with the two liter Pepsi bottle method.  I had one of those carrying racks that they use for stacking the bottles.  Just convenient that they hold eight bottles, so mark one opening for #1 and then place all the pistons/pushrods in the rack in their proper order.


GallopingGhostler wrote:CEF Conspiracy Theorist? Doh!  Very Happy lol!

Isn't that part of the CEF TOS?

The Hot Rod Mark

Nice method Mark. Thumbs Up Something .... about mother of invention. Pushrods. Yikes! rods, buckets, lifters, soooooo much stuff. Your system would have been perfect.

Conspiracy theory from Oz to the USA is like trying to sell coal to newcastle lol!

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Post  GallopingGhostler Wed Feb 01, 2023 6:02 pm

Yabby wrote:
batjac wrote:When I was rebuilding car engines for fun, I went with the two liter Pepsi bottle method. I had one of those carrying racks that they use for stacking the bottles. Just convenient that they hold eight bottles, so mark one opening for #1 and then place all the pistons/pushrods in the rack in their proper order.
GallopingGhostler wrote:CEF Conspiracy Theorist? Doh!  Very Happy lol!
Isn't that part of the CEF TOS? The Hot Rod Mark
Nice method Mark. Thumbs Up Something .... about mother of invention. Pushrods. Yikes!  rods, buckets, lifters, soooooo much stuff.
Your system would have been perfect. Conspiracy theory from Oz to the USA is like trying to sell coal to newcastle lol! GaryB 'Yabby'
Sounds like a part of Critical Racing Theory. Very Happy Why we have Tach Races here! Doh! Very Happy lol!
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