Cox Engines Forum
You are not logged in! Please login or register! Guests are limited to posting in the "General Questions (Guest Posting Allowed)" section only. Becoming a member is fast, easy and FREE!


Log in

I forgot my password

Search
 
 

Display results as :
 


Rechercher Advanced Search

Latest topics
» GSCB meet this Sunday
by GWILLIEFOX Today at 7:00 am

» The Breezy Hill Flyers "Black Fly-Day" Event !!!
by Kim Today at 6:46 am

» *** Double SIGH ***
by Kim Today at 5:15 am

» 1/2A Non-Contest Control Line Gathering
by Kim Today at 5:02 am

» Drill Press Question
by Jason_WI Today at 2:06 am

» Rebuild videos?
by Sunbird Today at 1:24 am

» Submarine ARA San Juan Lost in the sea ....
by batjac Today at 1:14 am

» testors mccoy running poorly video
by batjac Today at 1:10 am

» Phishing email from someone posing as you
by RknRusty Today at 12:51 am

» Recent engine acquisitions
by MauricioB Yesterday at 10:08 pm

Cox Engine of The Month
November-2017
MauricioB's

"Cox Tee Dee .010"



PAST WINNERS
Speed Contest 2018
CEF Traveling Engine

Gallery


Win This Engine!
The Traveling Prop
World of Aviation

cox piston with bulge on top

View previous topic View next topic Go down

Help! cox piston with bulge on top

Post  happydad on Sat Aug 29, 2015 4:23 am

yesterday or the day before someone, it's really late here is So. Cal., showed a Cox piston with a bulge on the top of the piston head. We all thought it was a loose connecting rod banging into the head of the piston. This picture comes from a Cox Dragonfly I was cleaning up to put on ebay. As I looked it over I thought I saw a little bulge on the top of the piston head, so I flicked what I thought was crud off the piston and to my surprise this is what I saw.

I'll post the pic when host it gets fixed. I can't host from my pc or from postimage.com ????
sorry it took so long.  Something happens when you get old, but I can't remember what it is.  Blow up Mad!   HD


a hole in the top of the piston with the connecting rod poking thru. look closely.

happydad,.  still retired, but ... Head Bang Head Bang Head Bang Head Bang Blow up Mad! Blow up Mad! Fireworks Fireworks
avatar
happydad
Platinum Member
Platinum Member

I Support My Forum

Posts : 1158
Join date : 2012-05-28
Age : 72
Location : Escondido, CA

View user profile

Back to top Go down

Help! Re: cox piston with bulge on top

Post  getback on Sat Aug 29, 2015 7:52 am

Looks like you got the finished product from the other day pic . I think that was Joe that had that other one ( yea that s nice ) Sad
avatar
getback
Top Poster
Top Poster

Posts : 4268
Join date : 2013-01-18
Age : 60
Location : julian, n.c.

View user profile

Back to top Go down

Help! Re: cox piston with bulge on top

Post  TDbandit on Sat Aug 29, 2015 9:09 am

Punched crown as I call it, happens when the con rod is reset too tight or the engine has a lot of time on it, also does happen with a excessively loose rod. I diagnosed one the other day with a club member, it was an old babe bee that had great compression and ran fine but suddenly started loosing power and kept quitting, he brought it over to me and I checked it out for him and found it had lost compression so I checked the head to make sure it wasn't loose, it wasn't so I popped the head off and there ya go, same issue. sucks. Only fix is a new P/C set Sad (Bandit)
avatar
TDbandit
Platinum Member
Platinum Member

Posts : 862
Join date : 2014-12-01
Age : 46
Location : Fort Valley Georgia

View user profile

Back to top Go down

Help! Re: cox piston with bulge on top

Post  RknRusty on Sat Aug 29, 2015 11:41 am

TDbandit wrote:Punched crown as I call it, happens when the con rod is reset too tight or the engine has a lot of time on it, also does happen with a excessively loose rod. I diagnosed one the other day with a club member, it was an old babe bee that had great compression and ran fine but suddenly started loosing power and kept quitting, he brought it over to me and I checked it out for him and found it had lost compression so I checked the head to make sure it wasn't loose, it wasn't so I popped the head off and there ya go, same issue. sucks. Only fix is a new P/C set Sad  (Bandit)
Or just another piston. I wouldn't hesitate to scavenge a piston out of the parts drawer and use it without replacing the cylinder.
Rusty

_________________
Don't Panic!
...and never Ever think about how good you are at something...
while you're doing it!


My Hot Rock & Blues Playlist
avatar
RknRusty
Moderator

Posts : 10436
Join date : 2011-08-10
Age : 61
Location : South Carolina, USA

View user profile

Back to top Go down

Help! Re: cox piston with bulge on top

Post  TDbandit on Sat Aug 29, 2015 2:01 pm

RknRusty wrote:
TDbandit wrote:Punched crown as I call it, happens when the con rod is reset too tight or the engine has a lot of time on it, also does happen with a excessively loose rod. I diagnosed one the other day with a club member, it was an old babe bee that had great compression and ran fine but suddenly started loosing power and kept quitting, he brought it over to me and I checked it out for him and found it had lost compression so I checked the head to make sure it wasn't loose, it wasn't so I popped the head off and there ya go, same issue. sucks. Only fix is a new P/C set Sad  (Bandit)
Or just another piston. I wouldn't hesitate to scavenge a piston out of the parts drawer and use it without replacing the cylinder.
Rusty
You're right *bops self in Head* have a habit of replacing p/c sets as matched sets keep forgetting that cox is one of the few that you can mix, match cylinders and pistons (bandit)
avatar
TDbandit
Platinum Member
Platinum Member

Posts : 862
Join date : 2014-12-01
Age : 46
Location : Fort Valley Georgia

View user profile

Back to top Go down

Help! Re: cox piston with bulge on top

Post  fredvon4 on Sat Aug 29, 2015 2:19 pm

When I retired a few years back, found this site, and started up my model airplane playing after a very long absence, I went way over board not realizing Cox made millions of these lil buggers. I did not know Bernie or Jason were reselling NOS and purpose built engines.

Long way to say I bid and won a LOT of engine Lots and the occasional good looking Baby Bee, TD, or Medallion

Later I read Paul Gibeault's mouse motor set up recipe and hints

Sorted all the parts paying attention to cylinder configuration and then cleaned each Cyl and piston, finally trying each piston in a cylinder until I got good at the drop out fit

Next I taught myself how to set the pistons with what I believe were junk pistons

Then I reset each piston and found that I should have done that first as now I needed to go back and re-establish best fitting combinations

OK a lot of words (for new folks who may not know this stuff) to say that Bandits mention of "keep forgetting that cox is one of the few that you can mix, match cylinders and pistons " is partly true but proper fit may require some thought and work

ON the other hand; I remember as a kid just running the bee-gee-sus out of the Cox .049s with any old fuel we could scarf up for weekend flying. Some times we just mixed and matched parts to get one working never thinking about the engineering behind making one run the best it could or last for any length of time
avatar
fredvon4
Diamond Member
Diamond Member

Trusted Seller
Posts : 2215
Join date : 2011-08-26
Age : 62
Location : Lampasas Texas

View user profile

Back to top Go down

Help! Re: cox piston with bulge on top

Post  jsesere on Tue Sep 01, 2015 11:54 pm

Yeah that was mine. I swapped it out for one in better shape. I may put it on an old Bee and let it run until it blows. Remember to always wear eye protection. Very Happy
Joe
avatar
jsesere
Rest In Peace
Rest In Peace

Trusted Seller
Posts : 1606
Join date : 2010-09-05
Location : Salem Oregon

View user profile

Back to top Go down

Help! Re: cox piston with bulge on top

Post  Sponsored content


Sponsored content


Back to top Go down

View previous topic View next topic Back to top

- Similar topics

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