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How was this Twin 049 made?551

How was this Twin 049 made?

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Re: How was this Twin 049 made?

Post  fit90 on Thu Mar 22, 2012 8:42 pm

FADEC, it's being used on GA reciprocating engines now. Why not just take it a step smaller? (FADEC-full authority digital engine control)

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Re: How was this Twin 049 made?

Post  ahrma_581 on Thu Mar 22, 2012 9:10 pm

PV Pilot wrote:There is a teaser video on youtube of a Gmark .12 twin and a few sad second of a dissasembled one. No real close up's of the crank pin setup and tiny bits, just a drunken flyby with the camera.

The google is your friend: http://modelenginenews.org/cardfile/gm12.html

Shows parts diagram and some photos of crank details. Could be duplicated with Cox cylinder/piston assy's, but I wouldn't want to build the bottom end with just a bastard file and a bench vise.

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Re: How was this Twin 049 made?

Post  dckrsn on Thu Mar 22, 2012 10:51 pm

......."but I wouldn't want to build the bottom end with just a bastard file and a bench vise."

Ha! Made my night. lol!
Bob

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Re: How was this Twin 049 made?

Post  RknRusty on Thu Mar 22, 2012 11:48 pm

Ahrma_581, welcome to the forums. That guy in your avie looks like Reverend Jim Ignatowski.

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Re: How was this Twin 049 made?

Post  Big Al on Fri Mar 23, 2012 5:17 am

WingingIt74 wrote:More precisely the crank. I can see how the case was made. I assume it just has a longer crank pin to accommodate both pistons? Ideally you would want them something like 90º from each other?

It's sprouted my imagination on trying to figure out and maybe building one.


http://www.ebay.com/itm/260982078736?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649#ht_500wt_1156
Several years ago that same engine (or one identical to it) was on eBay. At the time I also wondered if it could be a runner. I did a layout using stock Cox parts with thoughts of duplicating it and at first glance it looked like it might be possible by using a silver soldered crank assy. But alas, (see sketch) there was a serious fly in that ointment. Sad

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Re: How was this Twin 049 made?

Post  WingingIt74 on Fri Mar 23, 2012 7:29 am

hmmm, nothing is impossible. You just need a crank assembly that comes apart or a piston rod that has a cap.



image from here:

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Re: How was this Twin 049 made?

Post  WingingIt74 on Fri Mar 23, 2012 10:35 am

This guy said he isn't taking the tank off either... What's wrong with these people???

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Re: How was this Twin 049 made?

Post  WingingIt74 on Fri Mar 23, 2012 11:13 am

RknRusty wrote:Ahrma_581, welcome to the forums. That guy in your avie looks like Reverend Jim Ignatowski.
http://www.cbs8.com/Global/story.asp?S=13209288

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Re: How was this Twin 049 made?

Post  RknRusty on Fri Mar 23, 2012 11:51 am

RknRusty wrote:I sent him this question:
In the picture, one piston looks to be up while the other is down. How can it pull an intake vacuum or compress the fuel/air charge in the crankcase with the pistons working against each other? Am I missing something? Any chance you could take off the tank and show a picture of the rotating assembly? And the venturi too.
Interesting engine. Thanks,
Rusty
His answer, as we know was:
Dear rknrusty,

sorry, i am not going to take the engine apart. i do not know auything else about it. what you see is what you are purchasing.
- widow315

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Re: How was this Twin 049 made?

Post  RknRusty on Fri Mar 23, 2012 11:52 am

WingingIt74 wrote:
RknRusty wrote:Ahrma_581, welcome to the forums. That guy in your avie looks like Reverend Jim Ignatowski.
http://www.cbs8.com/Global/story.asp?S=13209288
I liked it better when I thought it was Reverend Jim. Laughing

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Re: How was this Twin 049 made?

Post  ahrma_581 on Fri Mar 23, 2012 1:37 pm

WingingIt74 wrote:
RknRusty wrote:Ahrma_581, welcome to the forums. That guy in your avie looks like Reverend Jim Ignatowski.
http://www.cbs8.com/Global/story.asp?S=13209288

That's funny, I'd forgotten where it came from. Just so we're clear, I'm neither the father nor the son in that article!!!

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Re: How was this Twin 049 made?

Post  WingingIt74 on Fri Mar 23, 2012 2:29 pm

ahrma_581 wrote:
WingingIt74 wrote:
RknRusty wrote:Ahrma_581, welcome to the forums. That guy in your avie looks like Reverend Jim Ignatowski.
http://www.cbs8.com/Global/story.asp?S=13209288

That's funny, I'd forgotten where it came from. Just so we're clear, I'm neither the father nor the son in that article!!!

lol!

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Re: How was this Twin 049 made?

Post  microflitedude on Fri Mar 23, 2012 2:40 pm

That's a car crankcase on the twin...

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Re: How was this Twin 049 made?

Post  nitroairplane on Fri Mar 23, 2012 2:45 pm

Big Al wrote:
WingingIt74 wrote:More precisely the crank. I can see how the case was made. I assume it just has a longer crank pin to accommodate both pistons? Ideally you would want them something like 90º from each other?

It's sprouted my imagination on trying to figure out and maybe building one.


http://www.ebay.com/itm/260982078736?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649#ht_500wt_1156
Several years ago that same engine (or one identical to it) was on eBay. At the time I also wondered if it could be a runner. I did a layout using stock Cox parts with thoughts of duplicating it and at first glance it looked like it might be possible by using a silver soldered crank assy. But alas, (see sketch) there was a serious fly in that ointment. Sad
Possible if you could do the second part as a screw on.

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Re: How was this Twin 049 made?

Post  andrew on Fri Mar 23, 2012 5:38 pm

Many times the second web is pressed on --- this is fairly common on multi-cylinder 2 stroke engines with needle bearings on the lower end of the rod.

But, in any case, I agree that the piston postions are problematic. To get the necessary crankcase vacuum and compression, the pistons should be mounted on the crank 180 degrees apart. Induction could be either reed or rotary disk. The picture clearly shows one exhaust port open and the second port covered by the piston. It may be that one of the rods or the rear web has snapped and only one piston functions.

Rotary disk induction may be more appropriate since a reed valve would require that the second throw be fully floating and unsupported. A rotary valve would add some rotational drag, but would support the rear rod journal.

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Re: How was this Twin 049 made?

Post  WingingIt74 on Mon Mar 26, 2012 9:47 am

Twins coming out of the woodwork lol! At least this seller is truthful in that they said it doesn't run.

http://www.ebay.com/itm/UNIQUE-COX-TWIN-CYLINDER-049-MODEL-AIRPLANE-ENGINE-/230767275537?pt=Radio_Control_Parts_Accessories&hash=item35bacd2e11#ht_4157wt_1224

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Re: How was this Twin 049 made?

Post  Cribbs74 on Mon Mar 26, 2012 10:02 am

The crankcase on that one was done well.

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Re: How was this Twin 049 made?

Post  WingingIt74 on Mon Mar 26, 2012 10:22 am

cribbs74 wrote:The crankcase on that one was done well.

Not sure if it's any better or not...


I guess you could do a threaded insert, can't tell with this one.

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Re: How was this Twin 049 made?

Post  Godsey3.0 on Mon Mar 26, 2012 1:27 pm

http://community-2.webtv.net/injunnut/UniqueSMALLModel/

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Re: How was this Twin 049 made?

Post  altidsulten on Mon Mar 26, 2012 3:14 pm

Nice engines in that link, but unfortunately the link in the article is dead. I would really like to see how he had made the crank.
Regards
Thomas

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