"1/2 A" & "1/8 A" airplanes These are the small ones...more popular now than ever.

MDS F2A 2.5cc

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Old 01-27-2015, 06:08 AM
  #51  
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Originally Posted by Raddaddy123 View Post
You CAN increase the diam of aluminum/silicon piston by heating it to high temp. Then you have to drop it in very high heat state to cold water, prefarably salt water. It will "freeze" in expanded state. I give you here another hint on cold/hot massge: it is about tuned pipes or spun exhaust mufflers. If you have bad dent, don`t put any hard object in it to bend the dent out. Just fill with water almost full. close then the ends with paper towel plug and put in a freezer. When water becomes ice.it expands and the dent pops out, nicely and smoothly, without any bad marks. Then just polish it with aluminum polish and yo can sell the pipe as almost as new...
Ha ha, neat trick. I have used ice for bending tubing around a form before, works great.
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Old 01-27-2015, 10:09 AM
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This is a good idea, I have a copper tube that needs this fix will try it tonight!
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Old 01-27-2015, 11:59 AM
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As a trumpet player on the side (well, sitting or standing usually), I have watched a few "how do they make that?" videos showing thin wall brass tubing being formed around tight corners with a core of ice. Pretty cool technique, not exactly new either. Works for small diameter tubing.
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Old 01-27-2015, 01:08 PM
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I have a Supertiger .75 muffler in the freezer right now. Hoping.
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Old 01-27-2015, 01:13 PM
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I put this retro vintage muffler together with silver solder and a torch. I have a lil ding I need out then I may take it in to get chromed.
Made for a 15 size engine.


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Old 01-27-2015, 03:04 PM
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That's a very cool looking header you got there..!
It looks like it ought to work, too.
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Old 01-27-2015, 06:21 PM
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Thank you CP, technically It has three header pipes to a muffler!
The stinger was cut a tad long to adjust sound if all goes well I plan to knock off close to half.


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Old 01-27-2015, 07:43 PM
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That will look good sticking out the side of cowl of a steampunk vintage racer type design. The thin streamline version of the Butter Knife.
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Old 01-27-2015, 09:15 PM
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Originally Posted by MJD View Post
That will look good sticking out the side of cowl of a steampunk vintage racer type design. The thin streamline version of the Butter Knife.
Real cool one!!My hint: make three plates between the engine and muffler with one hole only to choose the amount of "purr: Different sound with each different hole configuration !!!
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Old 01-27-2015, 09:43 PM
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Go all the way, make it a servo adjustable slide valve. You could accomplish the same thing with an old used cornet silver soldered to an exhaust header, and a servo on each valve. Might want to add a bilabial valve in there, you can go up the harmonic series as the throttle advances. There was an old raspberry type muffler wasn't there once?
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Old 01-28-2015, 01:51 AM
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Good idea's!!!

I should have went with 4 different size headers with butterfly valves free flopping inside the muffler tube to imitate a 4cyl sound. Steam punk would work lol would have to nix the chrome idea to keep it rustic. The engine makes good power the engineer worked for OS and took his years of efforts into the Magnum line.
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Old 01-28-2015, 02:13 PM
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I have a whistle that looks like a good attempt at a muffler. I held it on, and it seemed no louder. It wasn't quieter, but it wasn't sealed either. It didn't seem like a great idea at the time. My Supertiger .75 muffler still has the dents in after freezing. So sad. I have a header and pipe for it, but was hoping to make this one nicer looking.
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Old 01-28-2015, 03:06 PM
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For a pipe dent, I'd go see a guy who fixes brass instruments for schools - they are great at getting inside small diameter soft metal tubes and making them look half decent again. Trumpet lead pipes are only about .453" ID and they fix those. Just a thought.
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Old 01-28-2015, 06:43 PM
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Yea thinking I need to chrome the brass was to help add some ding resistance. The silver solder will handle the heat with ease on the .15 so who know was fun to make all the same.
ASpeed bummer it didn't work! Another trick heat up the dent area then spray with a air can for PC it come out coooold. The trick has had some successes depending on the shape of the ding.
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Old 01-28-2015, 07:04 PM
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There are two pretty deep dings. It will work ok, just looks ugly. It is ok. I may not use it anyway as I have a pipe.
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Old 01-28-2015, 07:23 PM
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If the muffler was firmly capped off on the ends with solid plates and tie wire to help the ice build more pressure, then that might work.
If there is a crease involved with the dent, then the aluminum would need to have that spot annealed.
I've got no actual experience doing any of this, but my advice is priced accordingly.
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Old 01-29-2015, 08:27 AM
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I could bend some 3/8" rod and ping it from the inside too, but it isn't important. Basic body work. I had heard at one time, that a grease gun can pump up a piece of aluminum tubing to make a pipe too, at least for a 1/2A size.
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Old 01-29-2015, 09:57 AM
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Try a pressure washer:

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

https://www.youtube.com/watch?v=bCsg5pQimWI
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Old 01-29-2015, 10:33 AM
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You can preheat the center to encourage expansion
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Old 01-29-2015, 11:38 AM
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Geez, now I lost half an afternoon watching youtube videos on getting dents out and hydroforming motorcycle exhausts. Interesting though. I actually felt like working on a plane for a change.
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Old 01-29-2015, 02:53 PM
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Originally Posted by Raddaddy123 View Post
Hi, I live in Helsinki/Finland.. That`s 150 kilometres to St Petersburg. We have , over the years had hundreds russian /soviet engines carried over here, especially after the fall of Soviet CCCP state. The engine in question is a product of "Sovied army aero club" produced in THOUSANDS. In Soviet time these were distribute from the central organization all over the russian state to various youth clubs. Every young member could get one if he wanted. In Baltic countries, especially guys have them lying around by hundreds, because they could, via various conections, get in their hands "real stuff" that means Rossis, Novarossis, Irvine 15 etc. There is really NO COMPARISON to them and the. MDS
A hot tip is that both this engine and the TRAXXAS 15 car engine are almost carbon copies internally to Rossi mark II. You can get very good P/C , rod and various other parts just to ordering them from your hobby shop. Just take the parts of MDS with you and measure you have the right version of Traxxas 15. But still, I just bid 2ea NOVAROSSI 15 Aero Speed engines in Ebay for F2A treiner use for about 150 dollar total (less hipping) I would use the MDS spinner assy, the pipe and the pipe silicon joint ring and simply toss everything else. Just not worth trying to figure it out, The crank is very badly finished, also tempering absolutely too soft-wears out fast. Most of the bearings rough, rodsimply too soft material, will break... The compression is way off, you have to machine the head to make the engine run near it`s pek. On top of everything, the timing is very high resonane timing so you end up having reasonable power in the region of 25.000- 35.000 rpm. Are you really going to have an engine/model combo in this rpm region and how are you planning to gt there without whiping the model very hard ? Toss it an use whatever else. ...
Bob Davis lists a heavy duty Traxxas 2.5/3.3 rod (on Ebay) that might be a suitable aftermarket replacement-aircraft alloy and bushed both ends-might be worth an email to him....

ChrisM
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Old 01-30-2015, 06:35 AM
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Originally Posted by ffkiwi View Post
Bob Davis lists a heavy duty Traxxas 2.5/3.3 rod (on Ebay) that might be a suitable aftermarket replacement-aircraft alloy and bushed both ends-might be worth an email to him....

ChrisM
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Cool, might just do that!
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Old 06-05-2015, 04:35 PM
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Tonight I ran the MDS with a slightly older Profi F2A pipe with pressure tap, Hayes 3oz tank, CF bench prop. I expected to have to fiddle but it fired up immediately, needled easily - lots more pressure from this pipe - and staged easily. I had more needle to go but stopped at 30,500 rpm. What a sweet sound. The new and repaired rod seems to be holding up fine. Engine was not over hot and feels great after cooldown.

Needle behavior was smooth and predictable, the pipe pressure did a great job adjusting the fuel flow in step with rpm, no frantic needle cranking. This however is not as hyperactively timed an engine as more modern F2A engines, so I may yet see why pipe pressure seemed to be out of favor with the speed junkies I spoke to.

Might be time to finish the 24" SWR delta.

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Old 06-05-2015, 08:33 PM
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It sounds like the potential is there, plus great parts support
Pipe pressure is absolutely dependent on the silicone pipe seal..so engine damage will result if the seal burps. There's other ways to roast engines though, so if pipe pressure works well...then great..!
The Nelson FAI .40 uses pipe pressure because it was found that it could keep up with fuel demand and a 13mm venturi. Venturi size is a tuning tool too..it goes hand in hand with the pressure source of your choosing.
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Old 06-05-2015, 09:49 PM
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The seal is tight so far. I opened the stinger to 4.65mm from 4.2mm. This was recommended for the longer runs to reduce heat buildup a bit. Shortened a 6/32 pressure fitting, "tapped" a hole through the thin wall just ahead of the weld, and JB Welded the fitting in. An hour and a half in the oven at 175 and voila.

Prop is a 5.75" diameter Mike Hazel bench prop - patterned after a 5-3/4" long piece of wood with maybe a 3/8" x 3/4" cross section, and a crude diamond airfoil carved in, corners rounded. Sort of a heavy cooling fan with enough drag and crude "pitch" to load the engine lightly and blow some air over it, let it stage easily on the bench, but keep it under control.

10% Omega with a few % castor. Head button is the 10% "nitro" head I got with the Profi.
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