Hi all,

Have been reading on RCU for Quite a while now but never chimed in until now. I found all the info here Quite usefull and interesting. As this is my first post I will try to do it right. so here goes.
I recently found an old weedeater in the back yard that was given to my son. It was burried under a bunch of old bicycle and motorcycle stuff. Turns out it still ran.(it was there for years) It was a Homelite 31cc trimmer. Just the ticket for a first conversion attempt. I sent the flywheel to RS engines to be Machined,ordered their conversion kit, and went to work on the case. And Here are the Results:

Final Weight with Prop came in right at 4.5# , this is with muffler, V-Stack, and aluminum saftey spinner nut.

Fuel used was 91 octane, with 100-1 Amsoil Mix

RPM Results.......TopFlight 20x10 Power Point.......5400rpm
(was kind of dissapointed)

MA Classic 18x10 wide blade ......6400rpm (getting better)

and my final test today......15x8 Power Point........ 9400 rpm (just a test but WOW)

Next test will be with a 16x8 or 16x10 apc or MA Classic.

Final Cost with the two new big props. $110.00

Not to shabby for my first attempt. Going to put this engine on a Dynaflight FlyBaby, 84 in. wing span. Havent built it yet, but probably will over the summer.

Sounds good!! Try to keep the RPM in the 7000 rpm range static. From your tests it looks like an 18X8 might be just about right. That will give it little room to unwind when it gets flying.
Adam

Adam,

Thanks for the advise. Still want to do some experiments with 16 and 17 in props. maybe even try some big three blade props. will also be checking static thrust with a digital fish scale eventually. going to build a test stand just for doing so.

Initial test results were done with engine mounted to the fence in the back yard. Kind of crude but it worked.
David

Yea 20X10 is a little much to expect out of a 31cc gas. The higher pitched 16 and 17 inch props will give you more airspeed and the lower pitched 18 inchers will give you more thrust. The airplane you choose and your taste/flying style will determine what balance of speed/thrust you prefer.

A fence post is great for a test stand, I clamp my stuff to a picnic table

BTW; beware, You start doing conversions and you will have more engines that you know what to do with :stupid:

Adam

You're telling me! I have converted 3 engines and have two boxes full of others I've collected/scrounged. I've got "ideas" for all of them, but not enough $ or building time for the planes and radio gear.

Adam, love your TIG welded stuff. What type of welder do you use? Any advice for a soon to be TIG owner?

Doug

As for engines I think I have 6 engines either converted or in the process and Im just about to start building a plane for one of them. :stupid: I get a kick out of doing the conversions for sure.


I dont think I will be "engine poor" again

Doug; As for the Tig welder I use a Lincoln 175 Square wave setup. Its pretty compact and does a great job. I think any of the name brand machines out there are very nice.

The best advice for any weldor is to practice, and practice a lot. Get scraps of whatever you are going to weld and start running beads. If I havent welded in a while I will run a few practice beads on some scrap before starting.

Also welding with a Oxy acetelene setup is great practice for Tig. and If you can find a welding class at a vocational school or something take it.
Adam

As this is my first engine conversion, I am all ready hooked on the idea of building large scale engines, far cheeper than any others out there. IMHO you can never have too many engines. My next conversion will hopefully be in the 45-60 cc range. They may never be TOC type engines, but they will be good enough for a poor boy like me. Being a single parent doesnt leave too much extra money. But like most people in our hobbie,

I AM HOOKED
David

wow! i never thought of that, putting one of these engines on a plane and actually flying it :stupid:

dave

Hey RENORACER, who is that RS Engines / Conversions ?

I may need to send a flywheel also, to get turned.

This is right up my ally, I got 4~25cc Homie's at the local junk yard for $3.00 scrap rate !!!!

Some can be fixed, and some want. I also got my EYE :stupid: on
a 2.0ci, poland 46cc engine ,

To many engines ta work on, but it's fun.

You can hacksaw/file the fins off on most engines pretty easy. The flywheel is pretty low quality aluminum. I turn mine on a lathe but if I didnt have it I would get the saw out :devious:
Here is the link for RS
http://www.rsengines.net/
Adam

Mikie888,

the address for RS engines is , http://www.rsengines.net/

If I had a lathe of my own I could make my own prop hubs, turn down flywheels , ect. Unfortunatly I dont ( yet) but maybe something to shoot for in the future.

The guys at RS engines are great, very helpfull, and very quick to respond to any questions you have. They also have carbs, plugs , and other items not listed on the web site. Just shoot them an e-mail .


Aneat:
I thought of trying to cut the flywheel with the saw and file method, but wasnt to trusting as to weather or not it would throw off the balance. Have you or anyone else tryed this with good results? I almost did, but was a little bit too affraid of possible shrapnal flying around.

David

Here is a pic of a Ryobi with the fins removed by the saw/file method.
Adam

don't be afraid to cut the fins off with a hacksaw. it's more work than doing it on a lathe but the results are the same if you work carefully. after i file off the rough cuts i sand it down on a large belt sander table in my carpentry shop and constantly check the thickness at different points around the circumference.

in the pic is an echo flywheel that i sanded by hand with sandpaper glued to a marble slab before i remembered about the belt sander in my shop :stupid:

dave

Hey!!!! nice job you guy's , I like it.

Hey !!!!! I thought of and idea, when you finish saw'in and file'in,

You could put, on your prop balancer to check for balance ? :stupid: Well would that work???

Hey~~ RENO ~~Thanks for the link.

I checked the balance on my Ryobi 4 stroke flywheel before removing the fins, then rebalanced it back to the same spot. I used a Robart prop balancer.