ANeat

My Feedback: (15)

Hello guys; Here is a pic of my Poulan 46 with a Muffler a fellow modeler friend of mine designed for his IMAC plane with a BME 102. I was getting ready to run the Poulan so I thought "why not" I had welded up several for my friend and had a couple extras laying around so I made up a header and fired it up
With the open header I was getting 6800 with a Zinger 20X10 and 95 db at ~25 feet. Very loud but a sound any motor head would appreciate

With the muffler installed the RPM was 6300 with the 20X10 and the sound was 85 db @ 25 feet. Very nice and at about half throttle the prop noise was louder than the engine.

These were the first runs on the engine and I was pretty impressed with it other than I could not start it by hand flipping?? I could rope start it just fine so I dont know if something minor is keeping it from firing at the lower cranking speeds or is it just the nature of the Poulan??

I need to get an airframe for this motor now. Im going to try and change a few things and make up a muffler that I can firewall mount and run the header down to it.
Adam

LORD_RC

My Feedback: (1)

very cool! nice job. Im assuming thats aluminum? Did you make the header? how did you get the nice bend?

ZAGNUT

My Feedback: (1)

i've got a collection of old alum lawn chairs, all kinds of nice bends in 3/4 7/8 and 1" tubing, a lifetime supply of headers for real cheap.

ANeat

My Feedback: (15)

I use a JD2 bender to bend my tubing. The header in the pic is .049 6061 aluminum 7/8 dia. The muffler is 3" dia and 12" long. Im going to try some smaller mufflers with less baffling and see how far I can go before it gets to loud.

Zagnut; Your stuff sounds good if the material is any good. There are a few alloys of aluminum that cannot be welded or dont hold up very well to heat or vibration.
But if I had it I sure would try it too. Its hard to beat free
Adam

Volfy

My Feedback: (23)

Adam, that muffler setup looks great. I wonder if you could possibly "tune" the header pipe length to gain top end RPM.

These magneto ignitions do need to be flipped at a fairly fast rate to fire a decent spark. You might try closing the coil pickup gaps a little.

strato911

Depends what magneto module it has. I have read a few times that the PHELON magneto modules do not make a very hot spark. My Poulan 25cc (1st conversion attempt) has the Phelon module, and after MANY attempts (~50 flips?), I was able to start it by hand. Once it warmed up, it started with 1 or 2 flips.

ANeat

My Feedback: (15)

Well I tightened up the flywheel gap today down to .010. Im not sure what the spec is on the Poulan 46??
Anyway I got a couple pops but it still wouldnt start. When using the rope it fires right up. Im wondering if my fuel isnt fresh enough and has lost a little of its volatility (sp??) and needs a hotter spark to fire off??
The next time I run it Im going to mix up a fresh gallon and see if that helps.
Volfy; I plan on trying some different lengths. Just waiting on some more tubing to arrive.
Adam

strato911

I set my gap using a business card. It's a real tight fit, but probably not less than 0.010

Sounds like you have to get the flip speed faster somehow... If the rope trick works, why mess with it.

ANeat

My Feedback: (15)

Yea the rope works nice for now, as long as everything is clamped down to my picnic table. I cant imagine yanking on the rope when the motor is on a plane :stupid:

Seriously; The rope works great for bench running but something else will need to be done so it can be flipped or get a big electric starter.
Has anyone used one if the recoil starters on a Poulan?? I havent cut the stub shaft off the back of mine yet. I had one on a Quadra years ago, just a one way bearing and a big spring.
Adam

strato911

I hate to do it, but I'm gonna buy a stronger starter. My old one isn't strong enough. Untill now, the biggest engine I've had to worry about was my friend's .61 Webra.

ZAGNUT

My Feedback: (1)

instead of a big starter ($$$) and heavy batteriies why not buy an electronic ignition? extra sensors are cheap and allow you to easily move the ignition from plane to plane so it doesn't have to be more expensive.

dave

ANeat

My Feedback: (15)

I agree Dave; I think the only way I would go for one of the larger starters is if I came across a fantastic deal. It wouldnt take much more for me to go for the ignition. Ive been looking over suitable airplanes right now and playing with the exaust systems.
Adam

strato911

This is my first conversion attempt, and a primary factor in the design of the entire plane is to keep costs low.

Gutterpipe fuselage
Coroplast wing
Homemade landing gear
WeedEater® engine
home-made muffler (eventually - still in progress)

Over 95% of this plane was purchased from the NEW LHS (Local Hardware Store). Only the fuel tanks, Tygon and radio equipment is through normal RC sources.

When I do another, I'll probably do electronic ignition. I have to learn to crawl before I start running. Anyone got plans for a homemade electronic ignition system?

ANeat

My Feedback: (15)

Hey Id like to see a pic of that plane;

Id like to see plans for a electronic ignition. Anyone tear apart their C&H so they could "reverse engineer" a replica???
Adam

ZAGNUT

My Feedback: (1)

CH sells their circuit board and coils for pretty cheap if you want to DIY. the box,cable, and boot can be found in any respectable junk box and the sensor is about a dollar from electronics suppliers.

dave

strato911

The plane's not done yet, but thanks to Adam's prompting, I have posted preliminary pics in my gallery It's quite a departure from my previous project, a SlowPoke 25.



8 foot wing span + 17 inch chord = 1632 sq-in wing (I hope it's not to big)
Current all-up weight (all un-installed parts included) = 10.0 Lbs
Therefore, Wing loading = 14.12 oz / sq-ft

If it flies like I hope, I hope to use it as a trainer (big=easy to see, gas=cheap, 16oz fuel = long flight)

ZAGNUT

My Feedback: (1)

love that airfoil

ANeat

My Feedback: (15)

Dave Ill have to call C&H. I had a little sticker shock when I first looked at their conversion kit for the 46 Poulan. I dont need the carb mount; prop adapter or other stuff and the price on just the ignition isnt to bad.

Dennis; the Spad is pretty cool, did you go for the yardstick for a spar or something else?? Ive got one of those 25's I think I got it out of a Craftsman weed trimmer. Ive done most of the conversion but havent ran it yet.


Adam

strato911

For my sake, I hope you're serious Zagnut, but I'll understand if it was said in sarcasm.

strato911

Adam - I was concerned that yard-sticks might snap during a pull-out from a dive. Instead, I used Coroplast on edge, several layers (4 in the center, tapering in layers towards the tips). If the stress gets to much, the spar can flex somewhat. To further reduce the chance of "snap" manouvers, I used the slow 100oz-in GWS servos (0.33s transit for 60º) for everything but the throttle.

What's your opinion - will it fly? Is a 25cc Poulan enough?

P.S. I added some specs to my earlier post with the pics.

ANeat

My Feedback: (15)

Try a PBF; Now there is an airfoil :stupid:

strato911

What size PBF would be appropriate for a 25cc Poulan? The local surplus center has several of these referbished engines (without trimmer parts) for $60 CAD ($42 USD).

ANeat

My Feedback: (15)

I dont know; Ive heard some others talking about making a PBF for the Ryobi 31cc to see if they could get it to hover.

I would like to watch that :spinnyeye

Adam

Volfy

My Feedback: (23)

Egads! The Canadians have gotten a hold of our stealth technology!

Anyway, I've heard it said that as long as you got a good motor pulling up front, you can fly with an airfoil shaped with your wife's high heels.

strato911

Volfy - you seem pretty knowledgable about these conversions. How many HP can I expect from a 25cc? The LHS suggested (and sold) a 15X8 Master Airscrew for break-in. What should I use afterwards? What kind of RPM's can I expect? Do you think my "Blue Heron" will fly?