Cox Engines Forum
You are not logged in! Please login or register.

Logged in members see NO ADVERTISEMENTS!


piston Laping tool  Cox_ba12




piston Laping tool  Pixel

Log in

I forgot my password

Search
 
 

Display results as :
 


Rechercher Advanced Search

Latest topics
» Cox 020 PeeWee rebuild questions
by LooseSpinner99 Today at 11:24 am

» COX .020 POWERED FLYING WING
by TD ABUSER Today at 10:35 am

» Destructive deconstruction - The Chinese Russian Carrier gives in
by GallopingGhostler Today at 9:47 am

» Project Cox .049 r/c & Citabrian Champion
by 1/2A Nut Yesterday at 3:54 pm

» Cox Icon RC TRansmitter and servo
by cstatman Yesterday at 3:16 pm

» The Three Stooges
by 1975 control line guy Yesterday at 1:06 pm

» Cox .020 PeeWee/TeeDee prop-screw
by roddie Yesterday at 9:17 am

» I Got Cheated!
by getback Yesterday at 7:28 am

» OS MAX-D
by ffkiwi Sat Oct 12, 2024 3:27 pm

» R/C battery connector..Help
by rsv1cox Sat Oct 12, 2024 8:04 am

» Who purchased one of my manifolds and has a tuned pipe that will fit to it?
by 1/2A Nut Sat Oct 12, 2024 6:17 am

» **VOTE-ON-THE-NEXT-COX-ENGINE-OF-THE-MONTH** (October 2024)
by 1/2A Nut Sat Oct 12, 2024 5:47 am

Cox Engine of The Month
October-2024
MauricioB's

"Cox .049 Circa 1975, custom."



PAST WINNERS
CEF Traveling Engine

Win This Engine!
Gallery


piston Laping tool  Empty
Live on Patrol


piston Laping tool

Go down

piston Laping tool  Empty piston Laping tool

Post  davidll1984 Thu Sep 17, 2020 10:11 pm

piston Laping tool  Lappin10 is it possible To Find that tool picturs ????


Last edited by davidll1984 on Sat Dec 25, 2021 8:51 am; edited 1 time in total
davidll1984
davidll1984
Diamond Member
Diamond Member

Posts : 2318
Join date : 2020-02-12
Age : 39
Location : shawinigan

Back to top Go down

piston Laping tool  Empty Re: piston Laping tool

Post  Levent Suberk Fri Sep 18, 2020 2:15 am

Model Builder magazine May 1979:

piston Laping tool  Screen63

piston Laping tool  Screen64
Levent Suberk
Levent Suberk
Diamond Member
Diamond Member

Posts : 2236
Join date : 2017-12-24
Location : Türkiye

Back to top Go down

piston Laping tool  Empty Re: piston Laping tool

Post  davidll1984 Fri Sep 18, 2020 8:00 pm

Merci beaucoup très apprécié difficile à trouver maintenant les informations supplémentaires sur le porting son très intéressante votre aide est très précieuse est je l'apprécie Very Happy I Love This Forum!
davidll1984
davidll1984
Diamond Member
Diamond Member

Posts : 2318
Join date : 2020-02-12
Age : 39
Location : shawinigan

Back to top Go down

piston Laping tool  Empty Re: piston Laping tool

Post  Ken Cook Sat Sep 19, 2020 6:21 am

5/16" tubing with masking tape wrapped around the top is even simpler. If you need more friction to hold the piston wrap more tape around it. I've been using the same piece of tubing for probably 35 years.
Ken Cook
Ken Cook
Top Poster
Top Poster

Posts : 5613
Join date : 2012-03-27
Location : pennsylvania

Back to top Go down

piston Laping tool  Empty Re: piston Laping tool

Post  Ken Cook Sat Sep 19, 2020 8:37 am

Reading this article essentially for me offered nothing that I already didn't know from self taught experience. One thing the article clearly mentioned was the need for several piston cylinder sets on hand. This is due to the fact that your going to screw it up which they did all the time. The article also stated that no one tuner or piston fit will offer appreciable results, it becomes more or less of try it, if it works, it works. I only felt the need to do this when I would constantly hear the engine sagging. The pistons even though are nitrate hardened, they still swell and until all stresses are relieved from continuous expanding contracting cycles will continue to do so.

When I would break in a TD for combat, I used the fuel I was going to run for combat which was high percentage nitro fuel. It's been so long since I've done this, I don't recall my rpm numbers. I would use the black 5x3 full and run it for a few minutes at a time and record the rpm's. I would then use clipped down versions going down to 4" in size and I would aim for high rpm's which is the number I can't recall. You had to be quick in doing this as a newer piston can expand very quickly which galls the cylinder. You would listen for any audible sagging when going for the high rpms. If you heard any sagging, quickly shut it down and let it cool. This is when we would lap a piston cylinder and go through this entire process. This may require 3-4 times of light lapping before we could hold that rpm without issues such as sagging.

Keep in mind that the cylinders of a Cox engine are dead soft. Essentially, your wearing it out. This is a very crude caveman approach. You have no idea when doing this if your cylinder is out of round or the piston is out of round or both. Your wearing a possible oval into a circle or vice versa. When you did lap it in, you only used this engine for contest use as it's longevity was seriously compromised. You didn't fly this engine for sport use. While it would still run for a long time, it never fully developed it's lifespan like a stock engine due to the high rpm's we used them for. I had quite a bit of TD cylinders on hand and I believe I'm down to my last few.

While the article makes claims that there's no solution to loose fitting pistons, I fully disagree. My best engines I ever owned had literally NO compression what so ever yet they would run like a scalded cat. They would literally windmill they were so free. These engines were also the first to hand grenade but prior to that, they offered the highest performance. As the article mentions, you need to run it and record it, there's no voodoo magic that says it will work.

While everyone isn't striving for top performance, these same issues occur for instance when you have a fully cowled in engine which is where I encountered issues with speed planes.
Ken Cook
Ken Cook
Top Poster
Top Poster

Posts : 5613
Join date : 2012-03-27
Location : pennsylvania

Back to top Go down

piston Laping tool  Empty Re: piston Laping tool

Post  balogh Sun Sep 20, 2020 12:44 am

Very open words Ken. Thank you. I also prefer longevity to top performance and let the engine wear itself rather than myself attempting to loosen up the good fit of cylinder for some extra rpm.

I second to your opinion that COX engines last long,and can work many hundreds of hours before retire. COX ran an experiment and after 400 hours the engine still ran fine though the reduced compression required to use of electric starter at the end.

At high rpm-s the time for blow-by to lose combustion gases is limited and even if when hand cranking the compression feels weak, at high rpm the impact of blow-by is limited.
balogh
balogh
Top Poster
Top Poster

2022 Supporter

2023 Supporter

Posts : 4908
Join date : 2011-11-06
Age : 65
Location : Budapest Hungary

Back to top Go down

piston Laping tool  Empty Re: piston Laping tool

Post  944_Jim Sun Sep 20, 2020 7:50 am

Gents,
I would love to see these scanned to PDF and parked in the "library" here.

Thanks in advance.

_________________
Never enough time to build them all...always enough time to smash them all!
944_Jim
944_Jim
Diamond Member
Diamond Member

2022 Supporter

2023 Supporter

2024 Supporter

Posts : 2018
Join date : 2017-02-08
Age : 59
Location : NE MS

Back to top Go down

piston Laping tool  Empty Re: piston Laping tool

Post  Levent Suberk Sun Sep 20, 2020 7:42 pm

Download:

https://www.google.com/url?sa=t&source=web&rct=j&url=https://rcbookcase.com/data/media/4/05MB_May_1979.pdf&ved=2ahUKEwjynomZgfnrAhVj-SoKHdzAAhwQFjAPegQICxAJ&usg=AOvVaw1rM4Exu-F3uKrgeLoj8jse
Levent Suberk
Levent Suberk
Diamond Member
Diamond Member

Posts : 2236
Join date : 2017-12-24
Location : Türkiye

Back to top Go down

piston Laping tool  Empty Re: piston Laping tool

Post  Levent Suberk Sun Sep 20, 2020 7:46 pm

piston Laping tool  Screen67
Levent Suberk
Levent Suberk
Diamond Member
Diamond Member

Posts : 2236
Join date : 2017-12-24
Location : Türkiye

Back to top Go down

piston Laping tool  Empty Re: piston Laping tool

Post  davidll1984 Sat Dec 25, 2021 9:03 am

Here is my version of this tool a little longer for more control piston Laping tool  16404410
piston Laping tool  16404411
With this tool I can fix a piston firmly and center it Well With this tool I can modify the exterior to give it a tapper To fit new piston in old vintage cylinder Very Happy
davidll1984
davidll1984
Diamond Member
Diamond Member

Posts : 2318
Join date : 2020-02-12
Age : 39
Location : shawinigan

Back to top Go down

piston Laping tool  Empty Re: piston Laping tool

Post  roddie Sat Dec 25, 2021 2:18 pm

Ken Cook wrote:       5/16" tubing with masking tape wrapped around the top is even simpler. If you need more friction to hold the piston wrap more tape around it. I've been using the same piece of tubing for probably 35 years.

Ken helped me with this suggestion a while back.. and I used the body (tube) from a simple ball-point pen. Its outer-diameter is just under the inner-diameter size of the Cox .049/.051 piston-skirt. A few wraps of masking-tape will provide a firm grip.

EDIT: before you read-on; I had some cylinders which had "BURRS" turned-into them, likely by the improper use of a Cox wrench.

Here's some photos of lapping that I did, which saved X2 cylinders from the being scrapped.

piston Laping tool  Lappin21

I used Noxon 7-metal polish.. with great results.

piston Laping tool  Lappin22
piston Laping tool  Lappin23

Insert the piston (inverted) through the bottom of the cylinder using radial "cross-hatch" strokes while lapping (never use straight-vertical stokes) keeping LOW in the bore. AVOID lapping near TDC where there could be a desirable taper/pinch (many vintage cylinders had this feature) which you wouldn't want to touch.

piston Laping tool  Lappin24
piston Laping tool  Lappin25
piston Laping tool  Lappin26

A "burr" will generally be in the exhaust-port area, where someone may have incorrectly used a Cox wrench. It's not uncommon.. unfortunately.

piston Laping tool  Lappin27
piston Laping tool  Lappin28
piston Laping tool  Lappin29


Last edited by roddie on Sat Dec 25, 2021 2:36 pm; edited 1 time in total (Reason for editing : Burred cylinders-repaired by lapping)
roddie
roddie
Top Poster
Top Poster

2024 Supporter

Posts : 8658
Join date : 2013-07-17
Age : 64
Location : N. Smithfield, Rhode Island

http://www.stilburnin.com

Back to top Go down

piston Laping tool  Empty Re: piston Laping tool

Post  davidll1984 Sat Dec 25, 2021 6:35 pm

Well lets saying that I needed more firmness That the piston is firmly fixed to machine it outside to mount on a lathe Let's say it's a multi-purpose tool Not just for laping Small Cox Logo Babe Bee .049
davidll1984
davidll1984
Diamond Member
Diamond Member

Posts : 2318
Join date : 2020-02-12
Age : 39
Location : shawinigan

Back to top Go down

piston Laping tool  Empty Re: piston Laping tool

Post  Sponsored content


Sponsored content


Back to top Go down

Back to top

- Similar topics

 
Permissions in this forum:
You cannot reply to topics in this forum