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ABC PISTON MATERIAL - 4/28/2005 6:23:23 AM   
combatpigg



Posts: 10017
Joined: 11/22/2003
From: arlington, WA, USA
Status: online 		I would like to be able to overhaul AAC, ABC and ABN engines that have worn pistons. I have several examples where the liner is OK but the piston is cooked. I have the tooling to come up with usable pistons, but I don't know where to go to get the correct alloy to make the pistons from.

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RE: ABC PISTON MATERIAL - 4/28/2005 6:28:53 AM   
w8ye



Posts: 17909
Joined: 12/11/2001
From: Taylortown, OH, USA
Status: offline 		Have you heard of the resizing of pistons by pounding a mandrel of the correct size down in the inside of the worn piston to mash the head out enough to be able to restore the compression? There's a car guy doing it. It may not work for bigger engines?

Enjoy,

Jim

< Message edited by w8ye -- 4/28/2005 7:41:34 AM >

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RE: ABC PISTON MATERIAL - 4/28/2005 8:11:47 AM   
combatpigg



Posts: 10017
Joined: 11/22/2003
From: arlington, WA, USA
Status: online 		Yes, as a matter of fact, over in the 1/2A forum, JAPANMAN has made tooling to do that with COX steel pistons. There is also a car guy who can pinch the liners and double the service life. Amongst all who tune in here, someone must be able to tell me which alloy works best for running against a plated liner, and where to buy the right stuff?

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Led Zeppelin is NOT "old fogie" music.

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RE: ABC PISTON MATERIAL - 4/28/2005 8:37:12 AM   
ZAGNUT



Posts: 2436
Joined: 2/26/2003
From: tel-aviv, ISRAEL
Status: offline 		high silicon, low magnesium aluminiums like 390.0 and a bunch of other casting alloys with nearly the same number would probably be a good choice. i do believe that modern auto pistons would be a good source


dave

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RE: ABC PISTON MATERIAL - 4/28/2005 9:53:11 AM   
DarZeelon



Posts: 7249
Joined: 4/9/2003
From: Rosh-Ha'Ayin, ISRAEL
Status: offline 		Dave, CPig,


There is a certain kind of auto piston material that may fit the bill.
These are the 'hyper-eutectic' material pistons.

Hyper-eutectic means the liquid aluminium base has been mixed with more silicon that it can actually dissolve, as it cools to solid temperatures.

So the silicon concentrates in crystals inside the aluminium material and on its outer surface.
These silicon crystals are tougher than the aluminium and contribute to high wear resistance.

This alloy also has a very low coefficient of expansion.


Most piston+sleeve sets come in closely fitted, matched pairs, so they are not available separately.

Some engine manufactures (OS, TT to name a few) exploit the need of a modeler for new piston+sleeve sets, by charging outrageously high prices for them; many times higher than their contribution in the cost of the engine.

Others don't!

I don't think that even with the high prices, it will be cost-effective to manufacture your own pistons.
If you are not totally sure that you have exactly the right material, this is even less likely.

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MVVS - Jett - Nelson - Bolly - Mejzlik

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RE: ABC PISTON MATERIAL - 4/28/2005 4:42:14 PM   
downunder



Posts: 3273
Joined: 10/10/2002
From: Adelaide, AUSTRALIA
Status: offline
quote:

ORIGINAL: w8ye
resizing of pistons by pounding a mandrel

I tried that once on a totally worn out Magnum 40. Not being sure how much force it took to expand the crown I started out with gentle taps inside the crown in about 6 places then did a test fit in the liner. Surprise, surprise...it wouldn't even fit upside down from the bottom of the liner!

I ended up having to make a mandrel to hold the piston in the lathe so I could skim off some of the excess If I tried it again I'd do it with the piston supported maybe half way up inside the liner so it couldn't over-expand.

Oh yeah...and the Magnum worked reasonably well after but I made sure I ran it in for a while nice and rich

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RE: ABC PISTON MATERIAL - 4/28/2005 5:19:21 PM   
Motorboy



Posts: 1717
Joined: 2/7/2004
From: Bergen, NORWAY
Status: offline 		Hi, there are 3 difference aluminium to piston. These 3 type aluminium has difference materials mixed in aluminium. Translated from russian model engine builder book from 1980. The material number are from soviet periods.. but you can take contact with metal dealer and find which aluminium has the contens of one of the 3 aluminium has about same material mixed in aluminium..

Piston must be lapped before use to fit sleeve. Can not use turn fine surface before use, because there are a lot of "mountains and hill" in surface and loose compression..

1. (AL-25)
11.0-13.0% Silisium
0.8-1.3% Magnesium
0.3-0.6% Mangan
1.5-3.0% Copper
0.8-1.3% Nickel
0.8% Iron
0.05-0.2% Titan

Rest Aluminium

2. (AL-26)
20-22% Silisium
0.4-0.7% Magnesium
0.4-0.8% Mangan
1.5-2.5% Copper
1.0-2.0% Nickel
0.7% Iron
0.1-0.4% Chrome

Rest Aluminium

3. (AL-32)
15.0-17.0% Silisium
0.8-1.0% Magnesium
0.7-1.2% Mangan
1.5-2.0% Copper
1.8-2.6% Nickel
0.7% Iron

Rest Aluminium

Jens Eirik

< Message edited by Motorboy -- 4/28/2005 5:23:01 PM >

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Jens Eirik
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RE: ABC PISTON MATERIAL - 4/29/2005 5:08:58 PM   
combatpigg



Posts: 10017
Joined: 11/22/2003
From: arlington, WA, USA
Status: online 		Thanks to all who replied! I wrote down all of those recipes and then did a GOOGLE search on alloys and found US suppliers! You can see by the addition of nickle and chrome why those NORVEL pistons look the way they do. MOTOR BOY, have you built any ABC engines?

_____________________________

Led Zeppelin is NOT "old fogie" music.

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RE: ABC PISTON MATERIAL - 4/29/2005 10:59:37 PM   
Motorboy



Posts: 1717
Joined: 2/7/2004
From: Bergen, NORWAY
Status: offline
quote:

ORIGINAL: combatpigg
MOTOR BOY, have you built any ABC engines?


Never maked ABC engines cause has not tools to set chrome in sleeve. Mostly maked own model diesel engines with steel sleeve and cast iron piston..

Jens Eirik


_____________________________

Jens Eirik
All landings are just controlled crashes!

(in reply to combatpigg)
       Post #: 9

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