Collet type prop driver for spark ignition?
 

Hi, I have a second Rowena saw conversion of about 55~60cc. They are based on the old Stihl 08S saw / TS350/360 disc cutter. This one has had the crank turned to accept a Super Tigre 2000 style prop driver, complete with brass collet.

I want to convert back to petrol and have fitted a pickup, magnet and insulator. I'm just wondering about pinning the collet in some way in case it slips and alters the timing. Should I bother? what is the easiest way of pinning if it is required? I only have common hand tools and a pillar drill, so don't want to mess-up the good fit of the components, or stop the collet from binding up and running true.

This is it:-

http://i230.photobucket.com/albums/e...ps7ce6b37b.jpg


http://i230.photobucket.com/albums/e...ps16588f59.jpg

Clean the collet, the crankshaft, and the prop drive washer with pure acetone or lacquer thinner. Get it all figured out so it will be timed correctly. Then put some blue Loctite on the inside and outside of the tapered collet. Double check that your timing is correct. Then put a propellor on it, tighten it down, and let it dry overnight. It will probably never slip. You'll need heat to remove it whenever necessary.

I'm curious about your carb mounting. I have done similar things. Could you provide details about yours for my curiosity??

AV8TOR

Stihl carb mounting;
 

Here, (in pictures), is how I did mine. However, just using the plastic/phenolic spacer and screwing the carb mounting screws into the aluminum adapter allowed the carb to get too hot and was problematic. In the final design, I had to make another phenolic adapter that is attached to the aluminum adapter with countersunk screws. The carb itself then mounts to the phenolic spacer with screws that thread into the phenolic spacer instead of into the aluminum adapter.

Engine is a Stihl 62cc from a chainsaw.

AV8TOR

OK. Loctite it is!

My carb adaptor is easy - the inlet port has an arrangement of 4 threaded holes and a flat face. It's probably 30 years old or more.
http://www.rcuniverse.com/forum/atta...mentid=1909774
http://www.rcuniverse.com/forum/atta...mentid=1909776

I'm surprised your carb got too hot. The heat transfer along two 6mm bolts won't be very great. Glad it was fixed though.

Had to get a larger bellmouth for this, noticing that the black one in the pic had the same diameter as the venturi!

http://www.rcuniverse.com/forum/atta...mentid=1909783

Started first flick. A couple tweaks of needles and running very reliably. Not quite as much power as the DL50 on a Zim pipe, but more than the CRRC GF40i. It is a few hundred grammes heavier and a lot thirstier than the 40 though. 22*8 JXF seems about right / a bit light, so a 23*8 Menz should be spot on.

Sounds nothing like the DL or 40 at idle, very much Stihl chainsaw. Ring a ring a ding ding, chang, chang, chang..... :cool:. Low idle.

The rings looked new and after a couple tanks it has bedded in and is bouncy now.

Job's a goodun :D

http://i230.photobucket.com/albums/e...ps39576d2a.jpg

P.S. This plane has had the following engines in it:-

G62. Previous owner who kept crashing it (???).
mcCulloch 32cc conversion (gutless, but cheap)
DL50 (Oresome!)
CRRC GF40i (Well suited, light and responsive, just won't go 'up' out of the prop-hang on a windy day with rudder etc well-over).
Stihl/Dolmar/Rowena 30yr+ old conversion (Unlimited vertical, scary chainsaw idle sound :) )

Next question:-

Do I bother fitting the 3W can???

http://i230.photobucket.com/albums/e...psd94cacff.jpg

Hey, "if it works don't fix it!" Unless you just love to tinker like me... :rolleyes:

AV8TOR

It looks good to me, I would go with that setup like it is. I would only try the 3w can muffler if the people at your flying field say it is still too noisy for them. If they aren't complaining, you are good to go.

Nice setup on the engine. We used to convert the trimmer, engines etc. to glow engines many years ago for giant size planes. At that time we had no electronic ignition systems and you either used the heavy flywheel magneto ignition or ripped it all off and went with glow fuel instead. Many of us used Perry carbs and made Perry carb adapters for the engines. But one could use whatever was handy for a carb at the time too.

I would make a mark on the drive washer to engine so that should you ever need to take it apart you can align it back up easily. Plus it will let you check it after a while to ensure it didn't slip on you too.

Thanks!

P.S. Already marked with a dremel :)

What type and size of flexible tubing is that on the exhaust and do you care to share where I can pick up some?
Thanks

25mm boiler/heating pipe. I bought it on Ebay here in the UK. You will find it listed for RVs, heating etc.

Look for [1" Flexible exhaust tube stainless] or similar

Thanks, I appreciate it.

20*10" prop had a few full throttle outings and no slippage.

It idles exceptionally well and sounds (unsurprisingly) like a Stihl saw on tickover. About the same power as a DL50 on a Zimmerman pipe and a similar thirst for fuel. Maybe 10oz for a normal 10 minute flight. Not noisy on the '50cc' Yusa aluminium pipe, although the pipe does get hotter than when the 40cc was connected to it.

So old Glow conversions converted back to electronic ignition, recommended :cool: