Author Topic: Grow a piston - how much heat and for how long? (Read 3419 times)

Dennis Toth · « **on:** December 10, 2017, 10:55:55 PM »

Guys,
Has anyone grow a piston? I understand you can heat the piston then let it cool and it will grow few thousands. This is supposed to work on iron pistons. Question is how much heat for how long and how to cool to keep the increase?

Best, DennisT

Air Ministry . · « **Reply #1 on:** December 10, 2017, 11:22:31 PM »

Back in the day , one of the aces in a artical , says of the OS 35 - ( on a New disassembled engine - to stress relieve, harden , and ' grow ' the crown .).

" 300 Deg. for three seperate hours " ( more than the cost of the engine in electricity , these days

)
often I think the liner was done too . Then it said " Lapped in with TOOTPASTE ' ( dunno what flavour )

General concensous in Aus. is youd be lucky to grow a well used , thoroughly heat cyled , piston .

What type of Engine ??

Lauri Malila · « **Reply #2 on:** December 10, 2017, 11:44:36 PM »

If you go over 1000F/540C, bigger metallurgical changes start taking place in iron.
I bake my piston rings in 1000F (2 hours) and noticed that 24mm dia component grows about 5 microns in dia.
L

GERALD WIMMER · « **Reply #3 on:** December 11, 2017, 01:14:08 AM »

Hello I have grown successfully a number of pistons mainly for OS and Enya engines. Not much luck with Fox (different piston material). The most successful were larger lapped engines including Enya 45 Baldie and an old OS 40H which went on to fly many hours. Always heated to a dull cheery red and quenched in oil. It worked for me.

regards Gerald

RandySmith · « **Reply #4 on:** December 11, 2017, 01:34:22 AM »

Quote from: Dennis Toth on December 10, 2017, 10:55:55 PM

Guys,
Has anyone grow a piston? I understand you can heat the piston then let it cool and it will grow few thousands. This is supposed to work on iron pistons. Question is how much heat for how long and how to cool to keep the increase?

Best, DennisT

Hi Dennis

They will NOT grow a few thousands of an inch, more like a few 10 thou, if your lucky, You will have a very hard time growing OLD heat cycled engines, but to try, if you have a special industrial , or Lab oven that you can control use 700 degrees for 1 hour, if your using your home over, try 500 degrees for 30 minutes 2 or 3 cycles, or use the CLEAN cycle of your oven . DO NOT throw them in oil or water to cool, let that cool down naturally.
Do not try this with aluminum pistons as they have silicone in them and the lapp fit ones have been heat cycled already, also if you get them too hot, the composition changes and you get 100 of tiny bumps all over the surface

Randy

GERALD WIMMER · « **Reply #5 on:** December 11, 2017, 04:24:11 AM »

Hello
I did not say how many I stuffed trying

Did find if I let them air cool the amount of expansion was less then if cooled a little more suddenly. In the old days motors were harder to come by here in New Zealand so I was game to try it on any worn out engine and contrary to good sense and understanding, I had good luck with many but often only after carefully hand lapping the now oversize piston back in.
But a few were ruined, perhaps they were toast anyway as I saw it. Should have left well alone with some collectable engines like my factory modified Oliver Tiger MkIII engine and got a new piston made and fitted the 'proper' way.

A little knowledge can be a dangerous thing along with youthful enthusiasm but it was great when it worked!

Regards Gerald

bob whitney · « **Reply #6 on:** December 11, 2017, 08:46:04 AM »

heated a Rossi 15 diesel piston cherry red then quenched it in brake fluid (in between water and oil } .lapped it in a lap to fit snug g in the sleeve and used it for two years

Robert Zambelli · « **Reply #7 on:** December 11, 2017, 11:32:13 AM »

I tried a brute force approach on a well used Merco 35.
I heated the piston red hot with a Bernz-O-Magic and let it cool to room temperature.
The fit was very tight so I lapped it in with rotten stone.
I was surprised at how well the fit improved.
When I get a chance, I'll report on how it runs.
Bob Z.

Dennis Toth · « **Reply #8 on:** December 11, 2017, 12:55:29 PM »

When heating the piston do you have a ceramic plate or something else that doesn't pull the heat away? I assume the best way to heat it is from the top. Since that's the area that does the sealing but we don't want the heat being pulled in to the plate that the piston is sitting on?

Best, DennisT

GERALD WIMMER · « **Reply #9 on:** December 11, 2017, 03:17:59 PM »

Hello I used to heat the piston with my oxygen/acetylene set with some welding rod holding it free hand and would heat the whole piston with my cutting torch set on a gentle neutral flame being careful not to oxidize it (just do not hit that cutting button/lever !!

). Very hard to just heat the top but it is the area that will hold the heat longest if quenching it and where it seems to grow the most. Some pistons will expand a whole lot after this (normally OS and Enya) while others have very little growth after heating a similar amount to a dull cherry red. My advice would be to start with some stuffed, worn and cheap motors to learn/experiment with . The old Enya 45 6001 I did nearly 30 years ago had no fit to begin with but is still a strong runner to this day with an excellent fit and in fact recently helped me into a first place in classic stunt event with another excellent run.

Regards Gerald

RandySmith · « **Reply #10 on:** December 11, 2017, 07:52:55 PM »

Quote from: Motorman on December 11, 2017, 11:53:04 AM

Using high nitro fuel and a large prop on a Fox 35 with a full lean setting the piston re-formed itself. The trick is knowing when to shut it off lol. Oh, and it ruins the crank pin.

MM

If you do that to a FOX 35, then the trick is to know when it is about to shoot the crankshaft out the front of the engine.... then shut it off a few seconds before :-O

Randy

Brett Buck · « **Reply #11 on:** December 11, 2017, 09:08:56 PM »

Quote from: RandySmith on December 11, 2017, 07:52:55 PM

If you do that to a FOX 35, then the trick is to know when it is about to shoot the crankshaft out the front of the engine.... then shut it off a few seconds before

Now THAT is advice you can use! You can't get this sort of high-level help just anywhere.

Brett

RandySmith · « **Reply #12 on:** December 11, 2017, 10:02:23 PM »

Problem with all this advice is, your never gonna hear how many pistons people destroy !!! LOL

But maybe we will get a few funny crankshaft departure stories !

Randy

GERALD WIMMER · « **Reply #13 on:** December 12, 2017, 03:59:58 AM »

Hello
Yes I admit it, about 50% pistons destroyed but the other 50% that worked fine and were more then good enough for me!
And I did weld up a broken crankshaft on an ED Bee and run it without injury

and I should add this was with my old ox/acetylene set .
I think getting a job as a teenager at an engine rebuilders and then working for an marine engineering company and welding repair company gave me too many ideas to try on my innocent little model aeroplane engines!

Latter on it was the old SBC's that gave me so much fun in my old cars .
There are so many unusual repairs one can do with their welder and a bit of determination

Regards Gerald
PS my 10 year old son picked up my hammers and proceeded to repair the grass shoot for the tractor today after I biffed it , the apple does not fall far from the tree

Brett Buck · « **Reply #14 on:** December 12, 2017, 10:57:43 AM »

Quote from: RandySmith on December 11, 2017, 10:02:23 PM

But maybe we will get a few funny crankshaft departure stories !

For equal time, I managed to break the crankshaft on my 1972-vintage OS-25S in a similar manner, and I have yet to break a Fox crank at all. Although once I started looking around, I certainly found a lot of examples with a very consistent set of conditions, all of which involved too much RPM (rare) or lots of nitro (common). When you could get a replacement from the factory in a few days for $6.00, it wasn't much of an issue, now it certainly is a problem.

My OS-25S was out of commission for about 30 years before I found a replacement crankshaft, and I didn't find a replacement factory small venturi until a few years ago. That's better than my dad's old Phantom P-30 - my Uncle Donny tried to "grow" the piston, cracked it (as happens very frequently to meehanite pistons, far more frequently than successfully growing them) and it sat in pieces from the 50's until this summer, when I finally found enough parts to completely restore it, including an original celluloid tank. He said he always liked the engine because it was the only engine they had that would reliably start.

Brett

GERALD WIMMER · « **Reply #15 on:** December 12, 2017, 02:28:58 PM »

Quote from: Brett Buck on December 12, 2017, 10:57:43 AM

That's better than my dad's old Phantom P-30 - my Uncle Donny tried to "grow" the piston, cracked it (as happens very frequently to meehanite pistons, far more frequently than successfully growing them) and it sat in pieces from the 50's until this summer, when I finally found enough parts to completely restore it, including an original celluloid tank. He said he always liked the engine because it was the only engine they had that would reliably start. "

Hello Brett I am happy to hear you have been able to restore your Fathers P30 it must be very important to you now after his recent passing which helps during these sad occasions.
For similar reasons I have been trying to restore my old Cox ME109 Super Stunter as it was my first C/L model for my 14th birthday from my now terminally ill mother who has little time left.

Regards Gerald

RandySmith · « **Reply #16 on:** December 12, 2017, 03:07:03 PM »

Quote from: Brett Buck on December 12, 2017, 10:57:43 AM

For equal time, I managed to break the crankshaft on my 1972-vintage OS-25S in a similar manner, and I have yet to break a Fox crank at all. Although once I started looking around, I certainly found a lot of examples with a very consistent set of conditions, all of which involved too much RPM (rare) or lots of nitro (common). When you could get a replacement from the factory in a few days for $6.00, it wasn't much of an issue, now it certainly is a problem.

My OS-25S was out of commission for about 30 years before I found a replacement crankshaft, and I didn't find a replacement factory small venturi until a few years ago. That's better than my dad's old Phantom P-30 - my Uncle Donny tried to "grow" the piston, cracked it (as happens very frequently to meehanite pistons, far more frequently than successfully growing them) and it sat in pieces from the 50's until this summer, when I finally found enough parts to completely restore it, including an original celluloid tank. He said he always liked the engine because it was the only engine they had that would reliably start.

Brett

The Fox 35 shoots cranks for all the reasons you listed, plus one of the most detrimental things to the FOX is heavy plastic props, matter of fact if you use a heavy prop with 15% nitro, that is almost a guarantee to launch a crank !

maybe should have called me on the OS parts, I have NVA for 15 and up, maybe a few 10 and 09 ones, plus I normally stock parts for the 15 20 25 25 40 46, I still have 1000s of parts hundreds of venturis and NVAs plus other parts , even though I do not have every parts

Randy

Jim Kraft · « **Reply #17 on:** December 12, 2017, 05:48:38 PM »

Some cast iron pistons will grow quite a bit. I have done quite a few Super Cyclone pistons by putting a piece of music wire in a vice, setting the piston on top, and heating it to a dull red with a butane torch. When I get most of it heated I grab the music wire with a pair of plyers and turn it upside down to drop it in to a fairly full can of used motor oil. I usually use a small coffee can and if you do not have enough oil it splatters out when you drop in the piston. I had one Super Cyclone I did that to that has many hours of running on it now and still has great compression. Better than when it was new. I have tried others with no success. Just depends on the piston and if it was heat treated in the first place I think.

Brett Buck · « **Reply #18 on:** December 12, 2017, 06:21:35 PM »

Quote from: RandySmith on December 12, 2017, 03:07:03 PM

maybe should have called me on the OS parts, I have NVA for 15 and up, maybe a few 10 and 09 ones, plus I normally stock parts for the 15 20 25 25 40 46, I still have 1000s of parts hundreds of venturis and NVAs plus other parts , even though I do not have every parts

For the 1972 baffle-piston version?

Brett

RandySmith · « **Reply #19 on:** December 12, 2017, 08:06:13 PM »

Quote from: Brett Buck on December 12, 2017, 06:21:35 PM

For the 1972 baffle-piston version?

Brett

Yes actually I still have about a hundred parts for the OLD OS 20 in stock now, still in the pack !!
Plus I think I have heads cases cranks and most parts less the backplate
Randy

Dennis Toth · « **Reply #20 on:** December 13, 2017, 03:01:21 PM »

OK, with the meehanite piston what causes it to crack when heating, heating to hot (cherry red) or heating to fast (ala torch)?
Best, DennisT

Lauri Malila · « **Reply #21 on:** December 13, 2017, 04:22:30 PM »

Most propably the uneven heating and cooling of that relatively brittle material makes it crack. And, it becomes more brittle during and after the overheating process.
In general I don't care what people do with their junk and if it gives some extra hours of running, good for them.
But if you want to keep the materials mechanical and tribological properties more or less unchanged, the critical 1000F temperature limit should be respected. L

Brett Buck · « **Reply #22 on:** December 13, 2017, 08:27:05 PM »

Quote from: Dennis Toth on December 13, 2017, 03:01:21 PM

OK, with the meehanite piston what causes it to crack when heating, heating to hot (cherry red) or heating to fast (ala torch)?
Best, DennisT

Both, but cast iron has very poor heat conductivity and is also very brittle, so any sort of thermal gradient will stress it far more than say, aluminum.

Brett

Al Ferraro · « **Reply #23 on:** December 13, 2017, 08:55:40 PM »

In the spectacular crank shooter engine category that I witnessed are.
1: Henry’s Fox 35 Speed engine at Brodak. It spit out the crank out while warming up the engine in the pits.
2: O.S. 25 FP in a speed limit combat plane. It launched the crank while in the air.
3: Fox 35 Stunt in a speed limit combat plane. It spit out the crank after the prop kissed the ground while running.
4: Picco .050. My 1/2a combat plane, The engine turning 33000 rpm, launched the crank 3 laps after I got the kill on my opponent.
5: Fox MkVI with Nelson P/L. It would brake the crank pin off while in the air racing in Warbird and the prop would spin like a pinwheel after the engine shut off. I broke 6 cranks in that engine and move to the MK VII.
6: Fox 36x B.B. cracked the crank at the counter weight after lean run melt down with 50% Nitro.
Al

RandySmith · « **Reply #24 on:** December 13, 2017, 09:04:29 PM »

Quote from: Dennis Toth on December 13, 2017, 03:01:21 PM

OK, with the meehanite piston what causes it to crack when heating, heating to hot (cherry red) or heating to fast (ala torch)?
Best, DennisT

Fox iron pistons are very brittle and weak, should need to know that

Randy

RandySmith · « **Reply #25 on:** December 13, 2017, 09:09:26 PM »

I have launched a few cranks too , G21 35 ,Fox 35 and Fox 36 , most notable was I launched 3 cranks out of the Testors McCoy 19s, they were very fast and great for plain bearing 15-19 rat racing, just had to keep a supply of engines around !

Randy