Maybe I missed this subject somewhere in this formum but I'm interested if anyone tried to convert such piece of equipment for RC plane.

15'' 4-CYCLE GAS STRING TRIMMER


[link=http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=54082]Harbor Freight has it for $79.99[/link]

RysiuM

Yes. Here is a picture of mine. There is a lot of info in the conversion forum.

Dave

Honda GX25, Shindaiwa 25 and 34, Briggs and Stratton 34...All ran about the same, around 7500 with an 18-6 Mejzlik..The Shindaiwa 34 turned 8000 with a larger carb...
Stihl makes a 64.9 cc backpack blower four cycle, 7200 with a 22-10 and 6400 with a 24-8..
There are pages about four cycle weed trimmers, do a search...

I just picked up the exact same trimmer from Meijers for $55, brand new display item, missing the spool
Started on the first pull (I've heard some can be difficult to start) Idle's beautifully
Still toying with the idea of conversion vs. using it as a trimmer
After reading everything you and AeroNut have done with glow plugs and Gas/Methanol, I'm wondering if it would work on a 4 cycle
One problem though, the carb doesn't appear to have adjustable needles (at least I can't find them)
Just need to take the plunge, I guess
Pete

A few years back I was all enthusiastic about converting one of these, until I found out what size, weight and power I will end up having. It is still much cheaper route than buying a Fuji 4stroke gasser, though. And unlike the Fuji 4strokes, you can actually fly these weedie 4strokes upside down.

Thanks guys. Sure it beats the price of Fuji. However after reading through this forum I see it doesn't perform any better than cheap 25cc 2-stroke (I was hoping for more torque swinging the bigger prop). Nope. I guess, the only benefit is the sound, not much worth the trouble and money.

RysiuM

R, In my opinion avoid the Ryobi 26cc fourstroke. I have one on a weed wacker and it has a really lousy carb. I'm pretty good with most engines but this one I can't master. I had it slated for a plane some day but a SuperTigre Diesel will get the nod instead.

I have a Ryobi weed trimmer. Purchased it when they first came out. It is very heavy and shakes badly. Are the new ones better?

You bet, I sell them too. I convert the smae four cycle that Fuji sells for $800.00 at Towerhobbies.com

www.bcmaengines.clearwire.net

I wonder, believe me, just out of curiosity, is anyone buying that? I mean 800 dollars for over 5 lb engine that has power of 2.5lb 25cc 2-stroke conversion and you can buy for less than 150 dollars (with electronic ignition).

When the first time I saw this Fuji in my LHS the sales guy (my buddy and very good RC-er) was very excited - wow, small 4-stroke. Next week when I asked him again he said, they just returned whole shipment as they couldn't figure out the way, how to sale them. Heavy, pricy and can be mounted only upright (what about inverted flying - who knows). Much cheaper way is to get any 40cc gas and 2 lb of lead.

RysiuM

I guess they were either ignoring the alternative 4 stroke conversions, or counting on hobby-snobbery to provide enough suckers who fold their arms and proclaim that they have an actual high end hobby product while you have some garden tool that was duck taped on.

oooohhhh, Duct tape....................hmmmmmmmmmmmmmm

I have a Briggs and Stratton 34cc, runs great and flies a GIANT stick (96" wing, 25 pounds) just fine. Slow but fine. I am now fitting said engine to a BalsaUSA Fokker DVII (fits perfectly) and am hoping to maiden it in a few weeks. Several friends have converted other brands, Honda, Ryobi, etc. Everyone has had great luck with them. If you are looking for power, go elsewere, its the sound that is so great about these. A buddy put a Honda GX31 on his Balsa USA Fokker DR1 mounted inverted and it flies and sounds like the real thing, and yes, I have seen the real thing at the Dayton Ohio Dawn Patrol (Man oh man was that a great show)

How does your engine mount work out? Mine was a real shaker but I think it had to do with the rigidity of the mount. I'm in the process of turning the fins off the flywheel but the belt on my lathe broke. I'm planning to check the balance of the flywheel when I'm done. If you do a search for my login name mgnostic you should be able to find a pic of my four stroke project

Mine is hardly shaky at all, no more than a standard two stroke that is. I do have a ryobi that is very shaky though.

Mine shudders a bit when you transition from idle to mid range rapidly (lack of fuel from being set so lean I think) but when running at any RPM steadily or transitioning any other way it is VERY smooth.

What prop and rpm you get?

I'm asking because I'm building 100" span Wilga, that may weight 15+ lb. I wonder what power I need for scale flying (no acrobatics).

RysiuM

It turns an 18/6@6500 RPM, it actually used to do 7000 RPM, I am not sure why I have lost power, could have something to do with messing with my carb and not getting it back to "Just right" but at 6500 it flew the 25lb 96" stick very well. The Stick would do inverted flight, loops, rolls, wing overs, etc, not alot of vertical, but enough to do the manouvers like I said.

Thanks. 6500rpm with 18x6 is qeuivalent to 7150rpm with 17x6 - this is the prop my Poulan 25 spins on gas/glow fuel. Good. I was affraid, that I would need to get something like 40cc + for my Wilga (I used to do acrobatic all the time), but it looks like it should fly with my Poulan.

RysiuM

I am flying a Bud Nosen Aeronca 102" with a Homelite 25cc, I actually use a 18/8 @ 6000 RPM, does all the basics, but just the basics, very slow flier with that engine.

This is scale project. First I was thinking about 4-stroke (Ryobi) for it, but as there is no benefits from it, I decided to use common 2-stroke conversion.
The original Wilga is very slow plane: stall speed is 40mph, cruise speed is below 90mph. There are not so many pilots allwed to do a loop on full scale Wilga and roll is plain impossible. The plane is used mostly for sport flying and glider towing. Sometimes for skydiving, but only 3 guys (plus pilot) can fit in there.

So my 1/4 scale (actually 22.5%) should take off at 10mph, and fly at 20 mph and be able to fly straight and level.

RysiuM

Any pics of this plane? I thought you were talking about a Witch Wilga for a while. THAT would be cool at 100in.

That sounds exactly like my Aeronca, you will have no problems at all with a 25cc, I certainly dont. Here is a picture of my DVII with the four stroke gas engine mounted and the muffler we made for it.

Just a few (WIP) in the thread [link=http://www.rcuniverse.com/forum/fb.asp?m=3296590]http://Power for 23% Wilga (PZL-104) scratch build[/link]

RysiuM

Propnut,

What size is the DVII and where did you get your engine?

Thanks

Sky Pilot, check out this thread on RC Scalebuilder, I posted everything (A little long winded) on there.
http://www.rcscalebuilder.com/forum/...870&PN=1&TPN=2