How I have to ask, is this effective for control line stunt engines?

Because at this present time I see it as a quick fix to combat a belled out liner caused by a lean run and it gets you back into the next heat with no parts exchanged.

I don't trust cold deformation nor monkeying around with the liner to jacket gap at all.

Thoughts?

Seems to work well enough for the R/C car people and they run a lot more revs and heat than a stunt engine. I would wager that the difference in piston / liner clearance between a worn out set and a new set is probably only a very few thou, squeezing the liners should get this back without too much trouble.
Many people worry about the plating (chrome, nickel) coming adrift. I can assure you that this won't happen due to squeezing. What have you got to lose by trying it, at worst about $30. Give it a try and report back, I have some ABC pistons and liners that could do with the treatment.

Regards,

Andrew.

Ok, this subject met with a bit of heat over at another forum but what gets me (the cynical part of me) is the hype surrounding the RC car world and what is needed to support that hype and thus the industry.
Cylinder squeezing seems to be popular with RC car engines and indeed, there is a highly praised person doing just this as a paid job.

But I have never heard of it ever used in aero based engines.

Is it because we have the lighter construction and thus thinner liners that really aren't suitable for 'squeezing?'
Is it because we are not so power obsessed and thus put up with a slight loss in power due to progressive wear?
Is it because we use a higher oil content and thus do not notice the slowly opening gap between the piston and liner?
Is it because when the piston is deemed to so worn as to effect performance, the con rod and liner is also and thus it is better to replace the whole set?
Or is it or traditionally conservative outlook on most things mechanical breeding mistrust with anything 'too good to be true?'

Did I mention that I am cynical about all of this?

Ok, this subject met with a bit of heat over at another forum but what gets me (the cynical part of me) is the hype surrounding the RC car world and what is needed to support that hype and thus the industry.
Cylinder squeezing seems to be popular with RC car engines and indeed, there is a highly praised person doing just this as a paid job.

But I have never heard of it ever used in aero based engines.

Is it because we have the lighter construction and thus thinner liners that really aren't suitable for 'squeezing?'
Is it because we are not so power obsessed and thus put up with a slight loss in power due to progressive wear?
Is it because we use a higher oil content and thus do not notice the slowly opening gap between the piston and liner?
Is it because when the piston is deemed to so worn as to effect performance, the con rod and liner is also and thus it is better to replace the whole set?
Or is it or traditionally conservative outlook on most things mechanical breeding mistrust with anything 'too good to be true?'

Did I mention that I am cynical about all of this?

Or is it because we don't pound the snot out of our engines on a routine basis, and therefore don't have as dire a need for this?

If you're racing, you are, by definition, (a) destroying engines, (b) messing with engines, (c) willing to put up with not-so-tractable engines as long as they go fast, (d) smarter than all of the engine manufacturers out there combined, (e), etc.

Hey Brian,
                  I probably suffer from being very conservative about all of this but one issue that worries me beyond restoring the gap between the piston and liner is sacrificing the intimate contact back to the cooling jacket by the same amount.

If you push the inside of the liner in say 0.005 of an inch then you form an air gap around the outside of it.
This forms a thermal barrier and promotes thermal instability.

Ideally you want your cooling jacket to be a shrink fit onto your liner, but with most modern mono block engine designs this is hard to do so the next best thing is a push fit.
Along comes your squeeze clamp and guess what happens to that fit?

That and the old car restorers adage of "well if that is worn out then what else is?" So many times I have heard my hot rod loving mates tell me that they have done something like a valve grind only to find that the head gasket needed replacing and then the piston looked a bit crook which led to the rings getting replaced which made them ......you know what I mean here. But this line of thinking might only apply if you run your engine below its peak and allow it to wear a bit more evenly.

 

Hello All,
I am a little surprised at all the negative comment. Lets face it, if you wear out an ABC or AAC P/L combination and there are no spares available, then what have you got to loose, apart from $30?
If it works you are back in business and if it doesn't you are $30 worse off and at least you KNOW it doesn't work! Why doesn't someone try it and report back. You can theorise until you are blue in the face, just do the experiment and then you will know!!!! If I had a suitable basket case P/L, I would try it like a shot.

Regards,

Andrew.

Hello All,
I am a little surprised at all the negative comment. Lets face it, if you wear out an ABC or AAC P/L combination and there are no spares available, then what have you got to loose, apart from $30?
If it works you are back in business and if it doesn't you are $30 worse off and at least you KNOW it doesn't work! Why doesn't someone try it and report back. You can theorise until you are blue in the face, just do the experiment and then you will know!!!! If I had a suitable basket case P/L, I would try it like a shot.

Regards,

Andrew.

Hi Andrew
Yes you are right, and these people have been doing this service for many years now, so it does work, whether or not stunt guys get good results we may see some time soon.

Regards
Randy

I disagree with you on squeezing the nickel coated liner! You are very probably correct that an OS nickel plated layer will peel at the drop of a hat. I wouldn't for a minute dispute that!

I think Randy's point is that if you squeeze the liner so that it is a bit undersized and then attempt to break it in (or worse, lap it) to get it back up to size, then you're going to wear down some plating.  If that plating is very thin, then you'll either wear through it, or you'll wear it so thin that peels (does that really happen?).  So if you were to squeeze a liner with a really thin plating, you'd have to be very careful that you brought it down to a better size without ever squeezing it under what it needs to be.

OTOH, if you squeeze a liner that's got a nice, generous plating thickness on it (whether it is chrome, nickel, or whatever), then you'll be able to remove some meat in subsequent breaking in or lapping without thinning the plating to the point where it peels, or outright wearing through it in spots.

That certainly makes sense to me, and is a simple question of thickness and wear, not particularly dependent on adhesion (regardless of whether the OS plating adheres well or not).

I think Randy's point is that if you squeeze the liner so that it is a bit undersized and then attempt to break it in (or worse, lap it) to get it back up to size, then you're going to wear down some plating.  If that plating is very thin, then you'll either wear through it, or you'll wear it so thin that peels (does that really happen?).  So if you were to squeeze a liner with a really thin plating, you'd have to be very careful that you brought it down to a better size without ever squeezing it under what it needs to be.

OTOH, if you squeeze a liner that's got a nice, generous plating thickness on it (whether it is chrome, nickel, or whatever), then you'll be able to remove some meat in subsequent breaking in or lapping without thinning the plating to the point where it peels, or outright wearing through it in spots.

That certainly makes sense to me, and is a simple question of thickness and wear, not particularly dependent on adhesion (regardless of whether the OS plating adheres well or not).

Tim

Exactly !


Randy

..... you would very easily be thru the coating to the brass.........

Regards
Randy

I'm a bit confused about this thread, especially about wearing out the chrome.  I had one LA 25 that wore out- typical worn out problems. wouldn't hold a setting, went leaner and leaner as it ran, impossible to hat start.  Took it apart and the sleeve had a big brassy patch below the ports and the piston would push through the top of the sleeve.  Got a brand new sleeve.  Surprise,  it had a big brassy patch below the ports.  The piston was slightly tighter, it topped out at the top of the sleeve.  But that little bit of size difference between a good running motor and a worn out one.

Since the worn out sleeve still had as much chrome on it I think a good tool to accurately crimp the top of the sleeve would be worthwhile.

I'm a bit confused about this thread, especially about wearing out the chrome.  I had one LA 25 that wore out- typical worn out problems. wouldn't hold a setting, went leaner and leaner as it ran, impossible to hat start.  Took it apart and the sleeve had a big brassy patch below the ports and the piston would push through the top of the sleeve.  Got a brand new sleeve.  Surprise,  it had a big brassy patch below the ports.  The piston was slightly tighter, it topped out at the top of the sleeve.  But that little bit of size difference between a good running motor and a worn out one.

Since the worn out sleeve still had as much chrome on it I think a good tool to accurately crimp the top of the sleeve would be worthwhile.

Hi Phil

The OS engines have no chrome?    They are nickle plated,   so I am at a loss that you have a 25 OS with chrome at the top and brass below the ports, I have never seen any like that in all the OS25s I have done here???
What I suggested is that ..if.. you were to do the sleeve pich / resize I would do it on a real chrome engine and  would not waste any time,money on trying to do a OS with the very thin nickle coatings.

Randy

An easy way to squeeze a liner is in an appropriately sized collet.  Having access to a free standing collet fixture or a small lathe with a manual collet set up will do the job.  Again, the collet has to be purchased the correct bore size or a soft collet employed that is bored on site.  A 5C collet can accommodate up to 1" in diameter.  Larger than that would take a different type, perhaps 16C.  If one has patience and a light touch, squeezing a sleeve in a collet will be easy.  You are probably talking tenths here.

Hello Randy,
You must have seen more nickel plated OS liners than most. So do you think that it is an adhesion problem or simply a wear problem? If it is the latter, then it may well be worth trying a re plating job. Electroless nickel plating is just a dip into solution and wait for the required thickness. If it is an adhesion problem, then there is no point plating over an existing nickel layer that will just fall off later!
There is a much better, electrolytic way, of coating nickel and this provides a better structure to the coating and it then becomes more hard wearing. I have an OS LA 46 liner that I replaced from an Ebay purchase. Just a little down on compression but otherwise fine (no brass showing!). I was hanging on to it as a spare. I could either see if the squeeze method works, or replate it with nickel that would be more hard wearing than the electroless stuff.
So is it peeling or just wear? I could be doing some wet chemistry, if the answer is wear!

Andrew

The plating of nickle compared to the chrome ,in this case, is this .. chrome does have a much better adhesion, or at least it maybe tougher simply because the coating is so much thicker.  Since the normal process of wear ,is that the soft part wears the hard part, this too is very bad on the liner coating, as the thin OS liners are really scored very badly from debris that either runs thru the chamber or sticks in the soft piston and cuts sratches in the sleeve.
The peeling that takes place in the OS sleeve happens much more often in RC or CL racing situations, when using a nickle engine in CL stunt with it running richer and a better oil ration seems to cut the peeling down a lot. They do however still wear thru the plating after some time.
I have found that the nickle plating in Thunder Tiger engines, which is a differant type of nickle plating is tougher (thicker) and last much longer than the thin electrolyse  nickle plating.
There are several people who do chrome old OS sleeves, you can strip the nickle and do this.
If you have access to the type of nickle plating that is on TTs  motor you may want to try that.  The other thing you could try is to use the same plating technique OS does , but to heat cycle the electrolyse nickle to full hardness ...before... it is ever ran in the engine

Randy

Eric,
The type of nickel plating  used on the LA series, is known to have lots of very poor properties, compared to electrolytically plated nickel or chrome. The OS nickle plating is just a dip process with no electrolysis.
I have never observed the peeling and worn patches on any LA engine, so as far as I am concerned the OS process, although producing poor coatings, is fit for MY purpose.
Randy sees far more engines than the rest of us put together, so if he sees a problem, then there IS one! Mind you the engines concerned have probably had a much harder time of things than any LA series that I own.
As far as the OS 40 VF is concerned, then I would suggest that the coating is electrolytically deposited chrome or nickel. I don't know for sure which it is. What it certainly is NOT is electroless dip coated nickel, of that you may be certain! You need to compare oranges to oranges, not apples!
As far as people who run LA series on pipes are concerned I too would like them to chime in and give us their experience. It would help to find what is the limit for the LA series nickel coatings.
Why would you doubt that there can be a plating problem on LA series engines? The coating process produces  a sub micron thickness of nickel. The nickel itself has known poor wear resistant properties and has poor adhesion. The LA series is just fine for sports use, but the whole design philosophy has been one of producing a product that is minimum cost. You only have to take a look at the component parts and compare it to the equivalent FP series, to see how this has been done.
Don't get me wrong I like the LA series, because it IS cheap and does the job required very well indeed. If you want a better quality product, then the Thunder Tiger GP25 and GP42 are better quality engines, that run as well as the LA series and are very similar in price.

Regards,

Andrew. 

My apologies Eric,
For some reason I took the wrong slant on your post. I thought you were saying that guys that ran their LAs really hard didn't have problems! How wrong can one get!
I suppose that having been in thin films and their properties for half a lifetime, one gets bogged down with detail! One thing that most people don't realise is that the same film, put down in different ways, can have enormously different properties. The more energetic the deposition method, the denser the material becomes and wear and stress properties can be tailored to what is required. This is way beyond the dip coating used by OS. I have used state of the art kit to put down and modify the properties of many materials.
  When one is thinking in complex deposition method terms, it is very easy to miss the levity in peoples responses!!!!!

Regards,

Andrew.