Author Topic: Scratches in cylinder... how deep is determental? (Read 3628 times)

frank mccune · « **on:** October 02, 2018, 09:02:56 AM »

Hello All:

I have been struggling with not being able to get more compression than would be considered as next to nothing in an engine. I had a new ring fitted but to no avail. I pulled the p&c and noted that there were very fine "scratches around the entire cylinder. These are so fine that they can only be seen via a magnifying glass and a bright light. I think that they are just rub marks caused by the new ring. They are 360 degrees in the cylinder and all the same depth and width. Is this natural for a new ring that has not been run for more than 12 oz. of fuel on the bench. The ring gap looks correct at .001 or less.

The p&c on my lapped engines look like corduroy but they still have and hold compression.

Thought and or suggestions!

Tia,

Frank McCune

RandySmith · « **Reply #1 on:** October 02, 2018, 10:34:46 AM »

do the scratches run straight up and down, or do the run in a sideways spinning up and down direction?

Randy

frank mccune · « **Reply #2 on:** October 02, 2018, 02:01:54 PM »

Hi Randy:

Thanks for the prompt reply.

The "scratches: run the entire length of the cylinder wall and are parallel to the piston travel from the bottom to the top. This is good? It means that the ring is an equal area cylinder abuser. If the scratches were only present above the bottom of he stroke, then I would think that the cylinder/ring fit was bad. In this scenario, It makes me think that the marks are not scratches but marks caused by burnishing the high spots off the cylinder wall. Or could they be caused by irregularities on the face of the ring? No matter what the cause, no compression!!!

Any thoughts/suggestions?

Be well,

Frank McCune

Tim Wescott · « **Reply #3 on:** October 02, 2018, 02:08:00 PM »

It sounds like someone didn't hone the liner before fitting the ring -- I'm pretty sure that's required (but I await Randy's word).

There should be a light cross-hatching pattern in there, unless our model engines get a much different treatment than car engines.

frank mccune · « **Reply #4 on:** October 02, 2018, 02:22:05 PM »

Hi Tim:

Thank you for the prompt reply.

The engine in question is "new and unrun." It may have been messed with prior to my purchase. The pin in the piston used to stop the ring from turning in its groove had to be replaced due to damage?

? A new ring was then fitted but alas alack, still no compression.

There is no sign of any hone work as the cylinder walls are mirror smooth. Perhaps a light honing and all will be well.

Be well,

Frank McCune

Tim Wescott · « **Reply #5 on:** October 02, 2018, 02:33:55 PM »

Quote from: frank mccune on October 02, 2018, 02:22:05 PM

Perhaps a light honing and all will be well.

Don't do that on my word unless it's my engine! Wait for Randy -- I was tossing out a guess to see if Randy agreed or stomped on me!

Air Ministry . · « **Reply #6 on:** October 02, 2018, 08:54:31 PM »

The Theory is , if you can feel it with your finger nail , Its WEAR - Not ' Polishing ' .

The double cross hatch / busted glaze - if the Bore is Shiney , is necessary when reringing .

RandySmith · « **Reply #7 on:** October 02, 2018, 09:04:16 PM »

Quote from: frank mccune on October 02, 2018, 02:01:54 PM

Hi Randy:

Thanks for the prompt reply.

The "scratches: run the entire length of the cylinder wall and are parallel to the piston travel from the bottom to the top. This is good? It means that the ring is an equal area cylinder abuser. If the scratches were only present above the bottom of he stroke, then I would think that the cylinder/ring fit was bad. In this scenario, It makes me think that the marks are not scratches but marks caused by burnishing the high spots off the cylinder wall. Or could they be caused by irregularities on the face of the ring? No matter what the cause, no compression!!!

Any thoughts/suggestions?

Be well,

Frank McCune

Hi Frank

The surface needs a "cross hatch" in the cylinder liner to help facilitate the break in of the ring, scratches running up and down the liner will NOT do anything to help the ring seat,, and will actually hurt it, these were made by the up and down motion of the piston, You can take a brake cylinder hone and rough up the surface before installing a new ring, the cylinder honing CANNOT go just in a motion around the sleeve, it has to swirl up and down, so you need to move the sleeve back and forth while the hone is running, then remove the hone, switch the the opposite end of the sleeve , and do the same process, you just need a light honing, do not try to grind on the sleeve, just enough to see the light swirl marks, after clean it all well, and fit a ring with about .001 gap for non chromed, or .0025 for a chromed liner. I would spin the engine over many times before cranking it, just put some light oil in the cylinder, and spin the prop with your hand, many times like several dozen, then spin the other way, this will start the process of wearing in and the ring seating, without it getting hot and taking a chance of the end gaps touching, if the crosshatch is doing its job it will open up the gap as it seats, Some people use a drill to spin the engine over, again this will help seat the ring and make sure its not getting too hot. Afterwards when you run it on the bench, run it sloppy rich, and do not lean it until you have 2 or 3 runs on it, Then you can pinch the fuel tube, and let it burst into a two stroke for a few seconds, do this at least a dozen or so times each run, You will be able to tell quickly if teh ring seats in well.
Hint the steel sleeve will cut easy, the chrome one will take a much longer time.
another Hint I told you a while ago, some sleeves will NOT ever take a ring and seat properly, that was the reason I suggested a New liner for one of you engines.
If you try to breakin a ring with the type sleeve you are asking about, it will NOT seal, and you will just quickly ruin the ring, Then you will have to get another NEW ring to install.

Randy
Also if this is an OS liner with nickle, then it is toast ! you cannot do anything with them except for honing and having the liner chromed

RandySmith · « **Reply #8 on:** October 02, 2018, 09:10:54 PM »

Frank this is what a cross hatch looks like
and is the only way to properly get the ring to seat in most all model plane engines

Randy

Air Ministry . · « **Reply #9 on:** October 02, 2018, 09:19:01 PM »

Quote

The ring gap looks correct at .001 or less.

.010 Or Less . Er 004 to 006 actually , tho less than 005 on a 40 / 46 is only usual in the Arctic .

WHAT ENGINE IS THIS , PLEASE .

PS a shapened pencil tip , you shoul feel ' Ridges ' .

thinking its just your rings closed & bound , with heat . If its at ONE THOU. ( end gap ) . Do the finger nail on the ring trip , too ,
To see if its caught any Burrs .

RandySmith · « **Reply #10 on:** October 02, 2018, 10:56:18 PM »

Quote from: Matt Spencer on October 02, 2018, 09:19:01 PM

.010 Or Less . Er 004 to 006 actually , tho less than 005 on a 40 / 46 is only usual in the Arctic .

WHAT ENGINE IS THIS , PLEASE .

PS a shapened pencil tip , you shoul feel ' Ridges ' .

thinking its just your rings closed & bound , with heat . If its at ONE THOU. ( end gap ) . Do the finger nail on the ring trip , too ,
To see if its caught any Burrs .

You are very welcome to setup your engines with a 5 6 or 10 thou gap, You will Never have proper compression or engine life with that, when the cross hatch wears the ring in, rapidly, you will have an 8 to 14 thou end gap
GOOD LUCK with that !

Randy

frank mccune · « **Reply #11 on:** October 03, 2018, 11:59:38 AM »

Hello Matt, Randy dt.al.:

The engine in question is a "new" OS SF .46. I had plans of powering a Score ARF with it but I may have to resort to my ST .49 Sport.

Thanks for all of the replies,

Frank McCune

Brett Buck · « **Reply #12 on:** October 03, 2018, 12:22:24 PM »

Quote from: frank mccune on October 03, 2018, 11:59:38 AM

Hello Matt, Randy dt.al.:

The engine in question is a "new" OS SF .46.

If it's a new engine, why did you take it apart, and what did it do in flight that you did not like?

Brett

p.s. I presume you know that .006 end gap is too much, right? Might as well drill a hole in the piston...

Tim Wescott · « **Reply #13 on:** October 03, 2018, 01:04:03 PM »

Quote from: frank mccune on October 03, 2018, 11:59:38 AM

The engine in question is a "new" OS SF .46.

How can a new, ringed engine not have crosshatching in the cylinder? Just how much OLD is implied by your quote marks around "new"?

RandySmith · « **Reply #14 on:** October 03, 2018, 07:08:19 PM »

Quote from: frank mccune on October 03, 2018, 11:59:38 AM

Hello Matt, Randy dt.al.:

The engine in question is a "new" OS SF .46. I had plans of powering a Score ARF with it but I may have to resort to my ST .49 Sport.

Thanks for all of the replies,

Frank McCune

Hi Frank

How does a new engine have that many scratches all over the sleeve up and down it, do you think there was dirt and debris in it and was ran or turn over? If it is run on the ground and held there you can suck up enough sand and dirt to ruin one quickly

Randy

Air Ministry . · « **Reply #15 on:** October 03, 2018, 11:54:49 PM »

What Then is your Recomended ring gap ,

for say a OS 40
OS 45
ST 46
ST 60 .

RandySmith · « **Reply #16 on:** October 04, 2018, 12:16:08 AM »

Quote from: Matt Spencer on October 03, 2018, 11:54:49 PM

What Then is your Recomended ring gap ,

for say a OS 40
OS 45
ST 46
ST 60 .

I have been setting them up since 1970 with these specs, this assumes that you have a round sleeve that has a crosshatch cut into it , so that it will facilitate the ring wearing into the sleeve quickly, If you have a smooth or damaged sleeve all bets are off
OS 40 .001 inch
OS 45 .001 in
ST 46 .001 inch steel 0025 in if chrome
ST 60 .0015 if steel .0025 to .003 if chrome unless it is a NEW chrome sleeve with a full cross hatch cut into it, then you can start at .002

I have done on my personal motors near ZERO gap, and NOT ran the motor but turned it over very fast by hand, both direction and let the cross hatch wear the ring in round while is is NOT getting HOT like it would from running it, then I attach a drill to the front of the shaft and spin the oiled engine over to wear it in until I see the the ring open up, This will happen fairly fast. I set my gaps at the exhaust and can normally see them, unless the ring is spinning if that happens I just remove the head, clean out all the oil, and either very light oil or lighter fluid, turn the crank and look inside, you can see the ring gap trail up and down the sleeve, After its opened some, I run it very rich, and do the procedure I wrote a few posts up

You may have trouble re ringing and OS engine as they are very difficult to cut a proper crosshatch in, in that case, just break the surface and make sure it is scuffed, this is ONLY on OS Steel liners and not ones that have the electroless nickel plating

Another info bit, if using a brake hone, it will be quick and easy to crosshatch a steel sleeve, a Chrome will will take many times longer, and you will not get marks as deep

Randy

Brett Buck · « **Reply #17 on:** October 04, 2018, 08:37:48 AM »

Quote from: RandySmith on October 04, 2018, 12:16:08 AM

You may have trouble re ringing and OS engine as they are very difficult to cut a proper crosshatch in, in that case, just break the surface and make sure it is scuffed, this is ONLY on OS Steel liners and not ones that have the electroless nickel plating

Another info bit, if using a brake hone, it will be quick and easy to crosshatch a steel sleeve, a Chrome will will take many times longer, and you will not get marks as deep

This is all very accurate, but based on experience, I fear what might happen with the information!

On the steel liners, it's so easy that *people tend to overdo it*. I never did an OS, but the ST46 could be acceptably roughed up with a brake cylinder hone in a a few (maybe 10) passes at very low RPM or even by hand in a pinch. I have seen people take a Makita drill, jack it up to full speed, and grind away for 5 minutes. Not only does that start taking off significant material (as evidenced by all the black oil that flings everywhere), you have a problem with getting the right sort of cross-hatch- too shallow.

Point being is that *you have to be careful*, do it only when actually necessary - that is, you have a problem with the engine in-flight or you have a slow degeneration of the power over many flights - and you have no other choice. The slow degeneration depends on your situation, but on the ST46 it tended to manifest itself as having to set the ground RPM lower and lower as it wore out. You might start out needing 8400 rpm at launch to get a particular speed, and over the period of many flights, it will have to be set slower and slower to get the right in-flight speed. My cutoff, with the stock prop, was 7800 and sea level, when it got to that, it was time for a new ring. Everyone else's numbers will be different, but with an average-quality 80's manufacture ring that might be 100 flights, with a very good ring, it might be 500-600.

There is something missing in this story - we started with a "new, unrun" engine, and somehow it's now been taken apart with what sounds like significant wear, and as near as I can tell, never flown, then had a new ring from somewhere, by someone, installed. So there is no information on whether it actually ran OK, in-flight, in the first place

Brett

frank mccune · « **Reply #18 on:** October 04, 2018, 02:46:37 PM »

Hello Brett et. al.:

The engine in question appears to have never been run, There are no signs of combustion on the inside even though I ran 16 oz. of fuel through while running it on the bench. There are no washer marks on the lugs.

There are no loose or tight spots in the p&c as the ring is moved through the length of its travel. There was no light escaping around the ring when viewed with a bright light. There is no leakage around the cylinder head sleeve joint. The ring gap as very small. The smallest feeler gage that I had was .003" and it would not begin to enter the gap. I could not see any open area between the ends of the rings. There is just almost NO compression.

Perhaps I should abandon this fool's errand and just be happy to use an electric starter. Or perhaps I should borrow a brake cylinder hone and have at crosshatching. I have done this this many times with lawnmower type engines and never had a problem.

I purchased this engine to power a Score ARF but perhaps ST .49 Sport, HP .40, Fox .45 or the ASP 61 would do a good job in providing power for the Score. The ASP .61 is a large, 20 oz., engine that may be squeezed into the Score. It is also a very powerful engine rated at over 2.25 h.p.

Advice and suggestions welcomed.

Be well,

Frank

Tim Wescott · « **Reply #19 on:** October 04, 2018, 02:50:36 PM »

Quote from: frank mccune on October 04, 2018, 02:46:37 PM

Advice and suggestions welcomed.

Stop messing around. Get some 46LAs or Tower 40s and concentrate on flying.

RandySmith · « **Reply #20 on:** October 04, 2018, 03:13:58 PM »

Quote from: Brett Buck on October 04, 2018, 08:37:48 AM

This is all very accurate, but based on experience, I fear what might happen with the information!

On the steel liners, it's so easy that *people tend to overdo it*. I never did an OS, but the ST46 could be acceptably roughed up with a brake cylinder hone in a a few (maybe 10) passes at very low RPM or even by hand in a pinch. I have seen people take a Makita drill, jack it up to full speed, and grind away for 5 minutes. Not only does that start taking off significant material (as evidenced by all the black oil that flings everywhere), you have a problem with getting the right sort of cross-hatch- too shallow.

Point being is that *you have to be careful*, do it only when actually necessary - that is, you have a problem with the engine in-flight or you have a slow degeneration of the power over many flights - and you have no other choice. The slow degeneration depends on your situation, but on the ST46 it tended to manifest itself as having to set the ground RPM lower and lower as it wore out. You might start out needing 8400 rpm at launch to get a particular speed, and over the period of many flights, it will have to be set slower and slower to get the right in-flight speed. My cutoff, with the stock prop, was 7800 and sea level, when it got to that, it was time for a new ring. Everyone else's numbers will be different, but with an average-quality 80's manufacture ring that might be 100 flights, with a very good ring, it might be 500-600.

There is something missing in this story - we started with a "new, unrun" engine, and somehow it's now been taken apart with what sounds like significant wear, and as near as I can tell, never flown, then had a new ring from somewhere, by someone, installed. So there is no information on whether it actually ran OK, in-flight, in the first place

Brett

Hi Brett

This is NOT something I have encouraged people to do, one because too many people will just ruin the motor, and I have told people if you do this, it will be very quick to do a steel sleeve, a Nickle OS sleeve is NOT NOT ever going to work on honing, you can only have it chromed, a steel chromed liner will have a much tougher coating and will take 10 to 20 times longer to hone a crosshatch.
People must do this at their own risk, the ones that will NOT pay someone to do this for them also do this at their own peril .
Many sleeves CANNOT be saved and re-used, some can.
On ST 46 and 60s It takes me normally 5 or 6 seconds with a hand drill or stand drill running on slow speed, in each direction.
An OS Electroless Nickle coated sleeve will be ruined after 4 seconds.
A Chromed ( real chrome) sleeve will take anywhere from 30 seconds to over a minute in each direction
With OS steel sleeves I only do these by hand and just try to only scuff the lightly, then you will need to do an longer break in

I too hate to give people this info because I have already seen how many parts will get destroyed, and how many will not read all of this and do the wrong thing to the sleeves

I can also tell you for a fact that many people do NOT know anything about how things work, I have had many people insist that I use a sleeve that is NOT good, either not round, worn funny, or worn out/damaged , they really think that a new ring will fix everything, it will not. I also have had people insist I use an old sleeve DO NOT install a new one, then complain when it would not come up to high compression when run in

So anyone doing this, Please know what your doing, and be careful

Randy

RandySmith · « **Reply #21 on:** October 04, 2018, 03:19:56 PM »

Quote from: Tim Wescott on October 04, 2018, 02:50:36 PM

Stop messing around. Get some 46LAs or Tower 40s and concentrate on flying.

I would not put either one in a score, It needs a 52 to 60 in it

Randy

Brett Buck · « **Reply #22 on:** October 04, 2018, 03:24:18 PM »

Quote from: RandySmith on October 04, 2018, 03:13:58 PM

This is NOT something I have encouraged people to do, one because too many people will just ruin the motor, and I have told people if you do this, it will be very quick to do a steel sleeve, a Nickle OS sleeve is NOT NOT ever going to work on honing, you can only have it chromed, a steel chromed liner will have a much tougher coating and will take 10 to 20 times longer to hone a crosshatch.
People must do this at their own risk, the ones that will NOT pay someone to do this for them also do this at their own peril .

My point exactly, and why I have gone in and posted disclaimers and warnings, because people definitely *have* done it, at least partly due to my having mentioned in the past, and then completely wrecked the engine.

There is something missing in this case, and I am very curious how a "new" engine appears worn out and needed a ring replacement, particularly since *I have a strong suspicion that this engine has never been flown in an airplane* and it would therefore be impossible to know if it ran correctly or not.

Brett

Brett Buck · « **Reply #23 on:** October 04, 2018, 03:26:24 PM »

Quote from: frank mccune on October 04, 2018, 02:46:37 PM

Hello Brett et. al.:

The engine in question appears to have never been run, There are no signs of combustion on the inside even though I ran 16 oz. of fuel through while running it on the bench. There are no washer marks on the lugs.

But inside, there are strong indications of significant running. OS cylinders *do not* come with pervasive vertical wear in them from the factory, and I am not sure why the ring was replaced.

Brett

RandySmith · « **Reply #24 on:** October 04, 2018, 03:26:49 PM »

Quote from: Brett Buck on October 04, 2018, 03:24:18 PM

My point exactly, and why I have gone in and posted disclaimers and warnings, because people definitely *have* done it, at least partly due to my having mentioned in the past, and then completely wrecked the engine.

There is something missing in this case, and I am very curious how a "new" engine appears worn out and needed a ring replacement, particularly since *I have a strong suspicion that this engine has never been flown in an airplane* and it would therefore be impossible to know if it ran correctly or not.

Brett

And I have asked the same thing earlier up in the thread, a new engine should not have scratched up sleeve in it, so I will wait for more info

Randy

Air Ministry . · « **Reply #25 on:** October 04, 2018, 06:49:42 PM »

Thanks for the info. Randy .

Back in the early 70's a silly school teacher who HAD BEEN WARNED boght a KATIPO for her boyfriend , I was volenteered to build the model,
Whilst the brother spent the school holidays sorting the engine , with the mechanic with the DB5 Aston behind the old mans boat shed .

After endless p8ss*ng about , he motored it over for hours , dribbling oil in the intake . AFTEr theyed trued everything up .

Asked how it went and if theyed had any trouble , was told No Problems . Not sure she rearalised the hours involved in the endevour .
Katipos were renowned for being useless , in the end I think they were warned by the consumer goods outfit , and pulled of the market .

If someone could find one of these for Frank , we could keep the thread going for a decade or so .

Air Ministry . · « **Reply #26 on:** October 04, 2018, 07:04:28 PM »

Quote

or the ASP 61 would do a good job in providing power for the Score. The ASP .61 is a large, 20 oz., engine that may be squeezed into the Score. It is also a very powerful engine rated at over 2.25 h.p.

Advice and suggestions welcomed.

Oh Dear .

http://sceptreflight.net/Model%20Engine%20Tests/ASP%2061.html

You Need to Build a SWEEPER , if you want to use the ASP . The Early F M Big One .
Or you could build a 200 mph Carrier Plane .
Or Sell It .
If you dont fly R C .

Why did the man bang his head against the wall ?
Because it felt so good when he stopped .

Steve Helmick · « **Reply #27 on:** October 04, 2018, 08:16:05 PM »

At this point, I think Frank should lower himself to using an electric starter and run the thing until it develops some compression. I had the same thing with my T&L ST G.51 after rebuild, but it finally came right, and could be hand started now. I first flew the G.51 on a 12.25 x 3.75 APC, per Dan McEntee's recommendation, and would suggest using that prop on your .46 for first flights. Reminds me, I need to pick up a couple of those.

Steve

Edit: I believe it's our man Shug that has a Magnum/ASP .52 powering his TF Score. That's a good choice, being ABC with no darned rings.

Dave Hull · « **Reply #28 on:** October 04, 2018, 09:12:06 PM »

Matt,
Don't bowled out on Frank or be jamming donkeys in the wickets, I'm learning stuff on this thread.

Gully McDivot

PS--For those without an encyclopedic memory of New Zealand model engine history, check out Matt's Katipo here:

http://www.modelenginenews.org/ad/katipo.html

While named after a deadly spider, I think the upshot is you'd be better off running a Black Widow than a Kaputi