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Old Mar 16, 2014, 02:51 AM
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Question
Which engine equivalent to the Cox .049TD?

Hi,

I am considering building Fred Reese's 1/2A P-51D next winter from a plan found on Outerzone. I built and crashed this plane when I was a teenager (kit from House of Balsa), but at that time I owned a Cox TD .049. Today I can't find one new so I was wondering which engine could replace the Cox. (Brodak?)

Thanks for your inputs.

-Paul
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Old Mar 16, 2014, 03:38 AM
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There are tons of TD's for sale new and used on Ebay a clean used one will do you just fine.
http://www.ebay.com/itm/VINTAGE-COX-...5#ht_827wt_960
http://www.ebay.com/itm/COX-TEE-DEE-...#ht_177wt_1198
http://www.ebay.com/itm/COX-TEE-DEE-...0#ht_67wt_1198
http://www.ebay.com/itm/Nice-Cox-Tee...ht_2607wt_1198
above are links to 4 up for bid found in less than a min.
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Old Mar 16, 2014, 04:22 AM
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No I want a NIB engine. This plane needs a very good engine. Have a look at the excerpt from F. Reese's building article below.
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Old Mar 16, 2014, 04:58 AM
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Bare in mind this original plane was flown with larger servo's rx and batteries the weight of the original flying craft will not be as near as light with modern servo's rx and battery.
1/2A P-51D Mustang by Fred Reese 1976 36in span. Any 1/2A in good condition such as the 049 or 051 on 25% nitro will fly it better than Freds 1976 version. A modern carbon/plastic speed prop will out perform all props sold for the TD in 1976. The RX gear will be at least 2oz lighter. A modern 2S 350mah lipo pack will be lighter than 1 cell of the 4 cell nicad pack / or AA dry cell used back then.
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Old Mar 16, 2014, 05:03 AM
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The original plans stated 24 to 28oz weight all up. A modern version can be made under 19oz.
You can use a single micro servo per aleron and one for flaps for a 5ch plane.
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Old Mar 16, 2014, 10:09 AM
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United States, WI, Milton
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Really Good Engine Needed- Then.....

Quote:
Originally Posted by Paul_BB View Post
No I want a NIB engine. This plane needs a very good engine. Have a look at the excerpt from F. Reese's building article below.
NORVEL-

Why use some of the engines that need constant "tinkering" Use the .061 RC version and have a great combination...

Tom
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Old Mar 16, 2014, 11:14 AM
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Yes Norvel just have to tend with the added weight /power of that engine and muffler.

http://www.nvengines.com/index.php?p...mart&Itemid=65

Norvel: NV Big Mig 061 R/C
Price: $74.99
Specifications
Displacement - 0.061 cu.in. 0.99 cc
Compression ratio - 9.5 - 11
Average performance - 4,000 - 18,500 RPM
Weight - 2.01 oz / 57 grams
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Old Mar 16, 2014, 12:46 PM
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Quote:
Originally Posted by teeceeveecee View Post
NORVEL-
Why use some of the engines that need constant "tinkering" Use the .061 RC version and have a great combination...
Thanks for the tip, Tom.


Quote:
Originally Posted by Amp Abuser View Post
Yes Norvel just have to tend with the added weight /power of that engine and muffler.

http://www.nvengines.com/index.php?p...mart&Itemid=65

Norvel: NV Big Mig 061 R/C
Price: $74.99
Specifications
Displacement - 0.061 cu.in. 0.99 cc
Compression ratio - 9.5 - 11
Average performance - 4,000 - 18,500 RPM
Weight - 2.01 oz / 57 grams
18,500 RPM? with a 6x3 black prop and with the muffler? Wow. And the throttling range is nice. Is this engine reliable?
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Old Mar 16, 2014, 02:48 PM
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Here is what Rusty had to say:

RknRusty (Thursday, 14 March 2013)
Rating:

The Big Mig .061 has replaced the Cox Tee Dee .049/.051 on some of my CL planes. Though the Tee Dee is a great dependable performer, the Big Mig .061 will blow its doors off. And even with the added power the NV gets Much better fuel economy. With an ounce of fuel a Big Mig will still be in the air long after the Tee Dee has landed. Even with a muffler you can prop it for as much power as you'll ever need for a 1/2A plane. They continue to get faster the more you fly them. My oldest Big Mig turns 28,800 RPM with a 5" prop. The recommended 6" prop doesn't do this engine justice.
It's happiest really unwinding with a smaller prop.

rknRusty
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Old Mar 17, 2014, 03:49 AM
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Thanks Amp Abuser.

On a side note - I remember long ago I tried to throttle my TD .049. I fitted my TD with a Tarno carb but I also had to add a muffler to get a reliable idle. But then it lost all its power and looked more like a worn out Babe Bee.

-Paul
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Old Mar 17, 2014, 12:48 PM
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Quote:
Originally Posted by Paul_BB View Post
No I want a NIB engine. This plane needs a very good engine. Have a look at the excerpt from F. Reese's building article below.
Fred recommended a 6x3 gray prop, for a Tee Dee on a HOB Mustang, I would use a 5 1/2 x 4. black prop. The Tee Dees really did a lot better with the smaller props.

Used Tee Dees are perfectly fine if you:

1. Replace the old compression glow head. Use a high compression (two fin) head like below. Make sure to replace the copper washer.



2. Make sure the plastic that holds the venturi is not cracked.



3. Make sure the con rod is not loose. A piston resetting tool will fix that problem. If a Tee Dee has a lot of time on it, it is a common problem, but easily fixed.

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Old Mar 17, 2014, 01:45 PM
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Thanks for all the info madsci_guy.

But if I can get 18,500 from the NV Big Mig .061 R/C and also good idling... I think I'm already hooked.
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Old Mar 17, 2014, 02:07 PM
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With little props, even a fairly high idle is ok, most planes will drop from the sky likely even at 6,000 rpm.
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Old Mar 17, 2014, 03:57 PM
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If I built that mustang this would be my set up a 5x5 glass /plastic prop carb with muffler on a TD.051 to keep things light on the airframe. About 20k on 30% nitro in the air unloaded ish my guess. Engine as shown is 74g./ 2.64oz. and to the right a TD RC .051 78g. 2.8oz with only a head mod.
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Old Mar 18, 2014, 01:27 PM
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I've got a HOB P51 on the board also. Is there a lot of difference between the Norvel ABC .049 and BigMig .061? What prop would you recommend for the NV 049? 5.5?

I was going to put an 049 Medallion in the P51 but found a new 049 NV at a garage sale. Based on what you guys are saying the Medallion would only be good for slow flyby's. lol Thanks for all the input and experience!
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