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Author Topic: Piston/liner materials  (Read 1078 times)
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Fourfingers
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« on: March 29, 2017, 07:55:59 AM »

Cant see anything relevant to this so here goes:
AAC, ABC, SSC and so on .... i am semi-familiar with these terms, or some of them, having a steel set up, a chromed liner, and an ABC in Olivers, Ridley and Chinese glows resp., but:
Presumably longer life is the big advantage of the later variants, but faced with a choice (in the same motor) of say ABC vs AAC, what factors play here?
Thank you for your consideration.
jc
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Konrad
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« Reply #1 on: March 29, 2017, 09:13:39 AM »

That will take a book to cover in any detail. But the ringless aluminum piston in a tapered cylinder (ABC, AAC and ABN) was developed to free the engine from the drag (heat) of the piston sealing rings. Read extract more power at higher RPM.  The use of various material all have their unique issues when it comes to the manufacturing and operation of the engine.

All the best,
Konrad
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qazimoto
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« Reply #2 on: March 30, 2017, 02:54:19 AM »

Cant see anything relevant to this so here goes:
AAC, ABC, SSC and so on .... i am semi-familiar with these terms, or some of them, having a steel set up, a chromed liner, and an ABC in Olivers, Ridley and Chinese glows resp., but:
Presumably longer life is the big advantage of the later variants, but faced with a choice (in the same motor) of say ABC vs AAC, what factors play here?
Thank you for your consideration.
jc

ABC vs AAC?

Good question, and one I asked quite a while ago myself.

The answer from someone with a lifetimes experience was that ABC tend to be much more robust. A single lean run with an AAC engine can cause the top of the Chromed Aluminium Alloy liner to come perilously close to it's critical heat treatment temperature. This can upset the fits. Brass is much more forgiving.
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Konrad
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« Reply #3 on: March 30, 2017, 10:23:06 AM »

My experience as an engine builder with the ABC vs AAC is the opposite.
AAC is dimensionally more stable. The beauty of ABC is that the chrome is deposited directly on the brass. No need nor is it desired to use strike coating.  With AAC the aluminum actually is stiffer than brass. The two aluminum alloys expand at a closer rate. And with a 6.5cc engine the weight savings is close to 50 grams. The down side is that to chrome plate on aluminum the aluminum needs to be protected from the chromic acid in the plating bath. This often is a zinc strike coating. The added manufacturing steps makes the AAC P&L more expensive.

*I built (reworked) AMA F1 engines. I was also fortunate in having built, from casting and bar stock, the USA NATS winning engines for FAI F3D Pylon (89).

All the best,
Konrad
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Fourfingers
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« Reply #4 on: April 04, 2017, 04:31:45 PM »

Thanks guys for this.  I feel happy now to enter the next pub quiz armed with this info ...
Seriously, though - as a rank amateur Sunday test bench flyer, the finer points of these variants may not be so imprtant.  Sticking with short medium-rev runs (at least till a neighbour approaches with a shotgun ,,,) on oily fuel, i think my engines will outlast me.
Now I suppose someone will tell me test bench runs wear them out fast!  A bit like a car on short runs, shops, school run, etc useless after a year or two, perhaps.
All said, my new (to me) Parra Wasp (ABC) seems immaculate.
Must build a plane.
ff
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qazimoto
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« Reply #5 on: April 05, 2017, 07:57:05 PM »

Thanks guys for this.  I feel happy now to enter the next pub quiz armed with this info ...
Seriously, though - as a rank amateur Sunday test bench flyer, the finer points of these variants may not be so imprtant.  Sticking with short medium-rev runs (at least till a neighbour approaches with a shotgun ,,,) on oily fuel, i think my engines will outlast me.
Now I suppose someone will tell me test bench runs wear them out fast!  A bit like a car on short runs, shops, school run, etc useless after a year or two, perhaps.
All said, my new (to me) Parra Wasp (ABC) seems immaculate.
Must build a plane.
ff

Thought you might be thinking of the Parra range of engines. I have a few of the .15 size diesels and one converted to glow. Great engines, but I converted an AAC diesel to ABC with a new piston/liner/rod assembly when the option became available from Parra. Performance leaped by 1200 rpm with no other changes.  I guess that they're much better at making ABC p/l sets than AAC.
« Last Edit: April 05, 2017, 08:25:37 PM by qazimoto » Logged
Fourfingers
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« Reply #6 on: April 06, 2017, 03:58:45 AM »

Gaz - Indeed, Parras are the biz .... got hold of a T3 prototype recently and thats a beaut!
Not too sure about the comp arrangement on the Wasp though.  Keep catching the spanner in the prop.  As someone said, that props got your name on it!
I believe Snr. Parra does a conventional tommy bar conversion .... might go for it when payday arrives.
One Q for you:
The comp nut is almost touching the head now, Im not sure of the mechanics but is there more comp left after this?
Maybe could remove head shim and try without?
Thats two.
Cheers
jc aka ff
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qazimoto
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« Reply #7 on: April 06, 2017, 04:13:17 AM »

Gaz - Indeed, Parras are the biz .... got hold of a T3 prototype recently and thats a beaut!
Not too sure about the comp arrangement on the Wasp though.  Keep catching the spanner in the prop.  As someone said, that props got your name on it!
I believe Snr. Parra does a conventional tommy bar conversion .... might go for it when payday arrives.
One Q for you:
The comp nut is almost touching the head now, Im not sure of the mechanics but is there more comp left after this?
Maybe could remove head shim and try without?
Thats two.
Cheers
jc aka ff

Yes, I have both a T3 and a Wasp. The latter is still NIB. Love the T3, better made than an original Olly.

Usually the deal with a push/pull head is that you adjust it only when the engine is stopped. It saves fingers and usually once you have a setting it doesn't have to be changed too much. If you have run out of comp adjustment and it's still running undercompressed then it certainly needs a shim or two removed.

Normally the "gross" compression is set by the comp screw, and the fine adjustment by the shims. Parra have an explanation sheet on the topic.
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Konrad
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« Reply #8 on: April 06, 2017, 08:56:48 AM »

Thought you might be thinking of the Parra range of engines. I have a few of the .15 size diesels and one converted to glow. Great engines, but I converted an AAC diesel to ABC with a new piston/liner/rod assembly when the option became available from Parra. Performance leaped by 1200 rpm with no other changes.  I guess that they're much better at making ABC p/l sets than AAC.
With that kind of performance change I'd think the AAC P&L was worn out (or distorted). Or the ABC P&L has some revised porting.
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qazimoto
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« Reply #9 on: April 06, 2017, 09:02:17 AM »

Thought you might be thinking of the Parra range of engines. I have a few of the .15 size diesels and one converted to glow. Great engines, but I converted an AAC diesel to ABC with a new piston/liner/rod assembly when the option became available from Parra. Performance leaped by 1200 rpm with no other changes.  I guess that they're much better at making ABC p/l sets than AAC.
With that kind of performance change I'd think the AAC P&L was worn out (or distorted). Or the ABC P&L has some revised porting.

The early Parra 15 Diesel AAC p/l weren't so great.
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Fourfingers
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« Reply #10 on: April 06, 2017, 03:13:30 PM »

Gaz ... " the T3 is better made than the Ollie ...". Now theres an inflammatory opinion!
Not having seen or handled, let alone owned, a new Ollie, I couldn't say.  But the Parra T3 is exquisitely made to be sure.
So, get it out the box and give it a blast ....
What is extraordinary, perhaps, is that with 60 plus years of technology - machinery, materials etc., - the new lookeylikey Ollies are only a bit 'better' than the original.  Just compare cars over 60 years.
The Olivers - father and son - must have been geniuses.
Oh, correction - got a new Cub at auction - how could I forget?  Its close, Ill grant you that!
And the Ridleys - up there with the best too.
jc
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qazimoto
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« Reply #11 on: April 07, 2017, 04:05:48 AM »

Gaz ... " the T3 is better made than the Ollie ...". Now theres an inflammatory opinion!
Not having seen or handled, let alone owned, a new Ollie, I couldn't say.  But the Parra T3 is exquisitely made to be sure.
So, get it out the box and give it a blast ....
What is extraordinary, perhaps, is that with 60 plus years of technology - machinery, materials etc., - the new lookeylikey Ollies are only a bit 'better' than the original.  Just compare cars over 60 years.
The Olivers - father and son - must have been geniuses.
Oh, correction - got a new Cub at auction - how could I forget?  Its close, Ill grant you that!
And the Ridleys - up there with the best too.
jc

Those gnomes in Ukraine do a pretty good job. Yes, the Olivers got it right a long time ago. Made engines to a standard not just a price. The ones in the middle years could be a bit ordinary unless they were "MOD". The best Ollys were the R-250's made in Sydney, Australia. Blew the pants off the lot of 'em in Vintage A Team Racing. Not available anymore really. The Parra T3 is a very good engine. Yep I've got the lot, early mk3's, middle mk3's and a Ridley one, a Ruski mk3 and a few CS olly inspired mk3's. A pair of mk4's on of which is a Ridley, and a few Olly Cubs, a brace of R-150's (mk1 Cub copies) and a cs cub.

Trouble is I can't use them all, so many engines, so little time left :-)
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Fourfingers
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« Reply #12 on: April 09, 2017, 02:15:44 PM »

Gaz - "so many engines, too little time ..."
If you ever want to relieve yourself of a Rothwell, just PM me, please.
ff
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qazimoto
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« Reply #13 on: April 09, 2017, 07:52:08 PM »

Gaz - "so many engines, too little time ..."
If you ever want to relieve yourself of a Rothwell, just PM me, please.
ff

I left a few R-250's off the list. Also picked up a NIB Gordon Cornell 2.5cc British Goodyear Diesel. Haven't run it yet, and probably won't. Pity!
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« Reply #14 on: April 12, 2017, 05:24:18 PM »

Ray, there was a simple timing change to the 2.5cc ABC/AAC a couple of years ago, I can't remember whether the liner went up or down but that's all it was, 500+ rpm gain was the result.
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qazimoto
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« Reply #15 on: April 16, 2017, 07:16:32 AM »

Ray, there was a simple timing change to the 2.5cc ABC/AAC a couple of years ago, I can't remember whether the liner went up or down but that's all it was, 500+ rpm gain was the result.

I remember it as a spectacular RPM gain, it starts much better as well. Perhaps the new liner better sealed the head. We did have problem with the latter early on with the Parra 15D.
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