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Td .051 powered speedster

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Td .051 powered speedster

Old 10-29-2020, 07:51 PM
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combatpigg
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Default Td .051 powered speedster

Hello to all fellow Cox TD abusers..!
The plan is to build as fast of a TD .051 powered plane as I know how to do.
The project will involve stealing some technology from what I've gleaned from others.
This wing will be smaller than what I've usually built. Credit for the smaller wing area than what I've used in the past goes to Amp Abuser's .049 Speedster.
The fuselage is based on the smallest frontal area / rectangular shape I could come up with. while using the stock engine mount lugs and a DuBro plastic engine mount. I suppose using a backplate mount would allow slightly less width up front, but I can't find the one I've got.
The engine is a brand new TD .051 I got for $85 shipped. I'll get a "baseline" RPM with a 4.2 x 4 APC on 22% nitro. Why 22%? I bought a jug of 66% Torco boat fuel and will use very basic math to cut it with methanol and castor.
I plane on shaving the inside of the piston



, detailing the crank fit, removing every last bit of rod slop, opening up the venturi to 5/32" and running it with a Nelson head once the TD head burns out.
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Toad (10-30-2020)
Old 10-30-2020, 06:05 PM
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It has been ages since I took a brand new TD out of the box and ran it. Last time was when gas was .99 cents.
I mixed up a batch of 22% nitro from a jug of Torco 66% boat fuel. Torco puts 17% oil in this, mostly all synthetic since castor will not mix well above 45% nitro. Torco does not publish this info, but I got this 2nd hand off of a Boat Forum.
My intention is to run 25% oil and at least some castor with almost everything I own. Oil is the most expensive ingredient, so guess which ingredient fuel suppliers will scrimp on first..?
The Cox TD comes with a "Run Sheet" that claims this engine will do 21,000 with a 5 x 3 prop.
Here are my results
5 x 3 Cox rubber prop. TD Head
2 head shims..[break in run] 20,200
1 head shim 21,500

4.2 x 4 APC
0 head shims 24,500
1 head shim 24.700

engine is ready to rock...!
The model is almost ready
Just re-upped with AMA and paid my $5 to the Fed Bureaucrats to make America safe again.
Last detail will be finding a local land owner to grant permission to fly.




0 head shims 22,000

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mgnostic (10-31-2020)
Old 10-31-2020, 04:14 PM
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A tiny bit of progress today...I found a Galbreath / Nelson head for the TD and it responded with 25,000 plus...!
Much time was spent trying to make handling refueling and starting the engine convenient with a cowl that has such limited access to the fuel line.
I hate putting holes into the cowl of a plane that is supposed to have the least drag possible. Easy access to the fuel line with hemostats is the only practical way I know of for fueling and starting the engine. Routing the fuel line so I don't create accidental pinches is proving to be a PIA so far. The cowl comes very close to where the fuel line plugs into the nipple on the NVA.
The other SNAFU is the servos drift at rest [neutral] with the new Spektrum Park Flyer radio I just got. HS65 servos and a 6.6volt LIFE RX battery. The binding procedure was simple enough.
The new RX doesn't have any antenna whiskers which is nice [if it works].


Last edited by combatpigg; 10-31-2020 at 06:55 PM.
Old 11-01-2020, 11:48 AM
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Another typical 3 day build? On our old speed models we run the fuel line outside the fuselage laying against the side. Maybe 1 1/2" long. It is split and there is a piece of 3/32" or 1/8" tubing to join it for fueling and to pinch. In the front view it is really not visible. We sometimes also closed the needle and pushed the whole plane onto a starter that was mounted on the toolbox. Open the needle until it fires, adjust it and off you go.
Old 11-01-2020, 12:20 PM
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Yes..now that you mention it I have seen the solidly mounted "hands free" starters that CL Speed Flyers use. That would be a worthwhile project to build.
Old 11-01-2020, 01:29 PM
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451 rpm more then the galbreath adapter, 1 shim.

https://kamtechnik.com/product/ktk-11/


https://www.youtube.com/watch?v=SIq19FW5EKE

Tee Dee .049 / Kamtechnik Turbo Plug Adapter
APC 4.2x4 /
1 head gasket 24,386 rpm with throttle sleeve.

Last edited by Pond Skipper; 11-01-2020 at 01:42 PM.
Old 11-01-2020, 02:59 PM
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Originally Posted by Pond Skipper View Post
451 rpm more then the galbreath adapter, 1 shim.

https://kamtechnik.com/product/ktk-11/


https://www.youtube.com/watch?v=SIq19FW5EKE

Tee Dee .049 / Kamtechnik Turbo Plug Adapter
APC 4.2x4 /
1 head gasket 24,386 rpm with throttle sleeve.
Thanks for the link..!
I intended to buy some and give it a try.
Old 11-01-2020, 04:52 PM
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Originally Posted by combatpigg View Post
Yes..now that you mention it I have seen the solidly mounted "hands free" starters that CL Speed Flyers use. That would be a worthwhile project to build.
Yes, I was thinking of doing one more for the combats.for flying on my own. The switch is the trick. A toggle switch is likely the best, but sometimes in the excitement you forget to shut it off. Maybe a foot pedal. A momentary switch is not great, as you need to have both hands pushing the plane on.
Old 11-01-2020, 11:08 PM
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https://kamtechnik.com/

Turbo heads for the TD .020 and TD .09 / .074 Norvel / Queen Bee are now in stock.
Old 11-01-2020, 11:22 PM
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Old 11-03-2020, 07:05 PM
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The little .020 makes that 1 ounce tank look like a 55 gallon drum...!
Bipeflyer was the guy who devoted a lot of time to .020 builds. I keep an eye out for a good deal on a TD .020..especially now that these heads are available.
Old 11-03-2020, 07:29 PM
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Hi Chuck it is my diy 1/2 oz tank

Old 11-03-2020, 07:33 PM
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Yes you have a good shot at 130 mph TD .020 with today's micro gear.
Old 11-04-2020, 10:27 AM
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Those are great looking tanks..!
The ultimate tank for a 40,000 rpm .061 would be a low profile bubble-less tank that fits under the pipe. I think about 1.5 ozs would be enough to make a few passes...but not much more.
Use a pressure tap off the pipe to ramp up the pressure on demand....but I'd try to see if CC pressure did the job before punching a hole in a 1cc pipe.
Old 11-07-2020, 07:10 PM
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Default Slow as molasses in January.....

Today was the first time I flew RC in a few years.
Since the failed 1903 Wright Flyer project.
The engine was down on power, but the plane launched strong on a 5 x 3.
The plane flies very well.....like what you would expect from a pylon racer or a speed plane.
At this RTF weight and small wing area the landings are "urgent" with not very much glide...but acceptable.
The engine might need a hole drilled in the cowl above the air intake. I will test to see about that.
I wish there was better news to report, but the plane wasn't fast enough to video.


Old 11-07-2020, 09:22 PM
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Happy to hear you enjoyed some RC flying again!
What is the squares, weight and span?
Fiberglass next by the looks of it eh wut,,

Old 11-07-2020, 09:32 PM
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What are you using for recording gear perhaps a upgrade the 4k non name brand cams are cheap under 100 bucks

4K hat cam action 60 to 120 fps for the fast ones
Old 11-08-2020, 01:25 AM
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The camera I've got is a Canon VIXIA HRF 300. So far I've only used it for the C/L videos I've shown recently.
Yes....I figured you might spot the fuselage mold halves. They is for a TD .049 with backplate mount [no side lugs].
The finished width of the fuselage ought to be 1 1/16"....so quite a bit more slim than the plane I flew today.
This plane has about 120 sq inches and IIRC it weighs about 10 ozs. It has what looks like perfect 0-0 trim on the elevator after flying it today, so I think the wing loading and CG is OK. I'll try to move the CG back just a tiny bit just to see if the glide can be improved a little.
I might have to pop a hole in the cowl above the engine air inlet, but I plan on taching it with the cowl on and off first.... to see what is going on.

Last edited by combatpigg; 11-08-2020 at 01:29 AM.
Old 11-08-2020, 03:48 PM
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What is the span 28?

Radial mounts are great heat sinks, thermal set NV can always use some help to gain top end.
The ones I tested / approved for Kamtechnik are the best I have two other kinds to compare
a break away and larger dia. version meh no comparison. Kam cools better bit more mass.
With the beams removed the weight gain is minimal.

Billet lower case with bearings would be nice.
I vote give the venturi some air / as the engine cools in the air setting goes rich / needs more intake
to keep the mix balanced or set NV level and hair lean.

I like longer tail moments it smooths out any quirks with less needed trim.

Old 11-10-2020, 12:11 AM
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The wing has rounded wing tips, so I'll just do a rough estimate of the area....
The "average span" is about 29 inches and the average chord is about 4 inches..
The plane weighs 10.25 ozs.
I checked the engine today and the cylinder isn't staying pumped up like it did when it was brand new. Instead of 25,000 plus it barely did 22,000 with the 4.2 x 4..This was with the cowl off.
Old 11-10-2020, 05:59 PM
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Ah bummer how much castor do you use?

I stick with 20% castor my go to:
https://www.ebay.com/itm/24-Nitro-Gl...t/224211455680

TD .010 - .020
https://www.ebay.com/itm/35-Nitro-Gl...t/224211457585

Some 3ch TD .049, .05 and .051 wings / flights posted on youtube:
28" / 86 sq. - 9 oz RTF
24" / 75 sq. - 8 oz
16.5" / 66 sq. - 6.19oz

Want to try a reed speed project the engines are lower weight.
If with throttle sleeve still bearable.
18" / 54 sq.
Old 11-10-2020, 10:46 PM
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Originally Posted by Pond Skipper View Post
Ah bummer how much castor do you use?

I stick with 20% castor my go to:
https://www.ebay.com/itm/24-Nitro-Gl...t/224211455680

TD .010 - .020
https://www.ebay.com/itm/35-Nitro-Gl...t/224211457585

Some 3ch TD .049, .05 and .051 wings / flights posted on youtube:
28" / 86 sq. - 9 oz RTF
24" / 75 sq. - 8 oz
16.5" / 66 sq. - 6.19oz

Want to try a reed speed project the engines are lower weight.
If with throttle sleeve still bearable.
18" / 54 sq.
The most powerful Cox 049 I ever saw was a KB. It turned 4.2 x 4 faster than any TD I ever owned. It belonged to Patrick Ulmer..the designer of The Blink and the Das Not Ugly planes. One thing that would lose weight is finding 5-40 aluminum prop bolts.
Old 11-11-2020, 01:53 AM
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My trick is a short .049 stud bolt and .020 bullet spinner on a .049
The stud bolt has a hex head lock it down to the crank threads.

I have done the same for a TD .020 with a tapped out TD .010 bullet spinner.
Hex point head is available for the .02 big plus when removing.

Also tapped .049 bullet spinners for .09's and recently had Valentine retap
two 09 bullet spinners for my TD .15 because the APC prop hubs are smaller
in dia. than the old school props saved bit over 4g to boot.



Old 11-11-2020, 02:02 AM
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.049 vs .020 bullet spinners.


Old 11-11-2020, 09:29 AM
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I am starting out with Torco 66% nitro fuel...which is about 17% oil...all synthetic. I dilute it to 22% nitro by adding methanol and Sig castor. So, I bring the oil content up to over 20%, but 1/4 to 1/3 of the oil is synthetic.
I didn't see any signs of running hot and the bladder was empty at the end of all 3 flights. The head is a Galbreath..I found 4 that I bought years ago when I started hoarding things so that I could still fly after TEOTWAWKI...lol.
My reasoning for buying 66% is that I would only pay shipping on 1 jug of fuel instead of buying 2 gallons of 25%
There was a core group of 20 guys locally and 50 nationally that I flew 1/2A Combat with for over 20 years. I think the average member of our group owned 2 coffee cans full of worn out and broken CoxTDs, while managing to keep a few good running specimens on hand for contests. We were all experts on how to prepare them...thanks to magazine contributors like Rich Lopez, Larry Driskill and Dan Rutherford. Once the Foras and Cyclons came out, we were no longer "engine experts"...we just became "engine operators". I have never bought any spare parts for my Fora or Cyclons. I gave my Fora away while it was still running strong. I lost my 1st Cyclon while it was strong and I have a 10 year old [replacement] Cyclon that is still strong.
I still have those coffee cans full of TD junk though...lol.
With Cox engines, the engine itself becomes a bigger part of the hobby and that's OK.
Your spinners look great. I should make a few and get a Hornet starter going.

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