I have a NIB Dynaflite Chipmunk kit soon to start building during out imminent Southern hemisphere winter.

From what I have read, it seems that a Ryobi conversion is a popular choice for this model.

I am in a lone modeller situation and have no personal experience at all with gas engines, but recently acquired a Ryobi blower-vac motor as a gift so have a powerful reason to go down this track. I have now downloaded plenty of seemingly neutral instructions on the procedure so have plenty of theory behind it all.

My research to date suggests there are three specialist outfits in USA that can supply custom-made conversion components. In alphabetical order these seem to be Carr Precision, JAG Engines, and an outfit called Paragon who seem to be pretty secretive when it comes to supplying information.

I`d be very interested in any information or opinions offered on these suppliers before I make a further move. Can anyone out there help on this.

Thankyou.

Alan W

Carr has a very good reputation in this part of the US. Their prices are reasonable and they do good work. You can buy the conversion parts and do it yourself "down under" if you want. I don't have any experience with the other two suppliers you identified. Good luck and happy flying.

If you do need more info on this subject,check out the $49.99 thread I just started.I have used the carr product and seen the other two.None of them are bad.
I have also used the B&B parts and can heartily reccomend them,especially the mount,which is simple,as short as possible (with the carb and muffler on the back the Ryobi is already a long package)cheap,and bulletproof.See.
WWW.bennettbuilt.com

I have used the Carr parts on three engines. One of them being a Ryobi. Everything was made well and they were always very helpful when you called them on the phone. I know that Carr is a good place.

B & B also has a good reputation but I personnally don't have any experience with them.

The Ryobi does tend to be longer than typical glow engines.

By theory, it is possible to make a shorter engine from the long shaft engine than from the short shaft. After you look at them and the parts, you will know what I mean.

To buy the bigger carb from Carr will make a nicer engine for model airplanes.

Run the engine as a leaf blower some before you convert it. A couple tanks maybe.

It is very unlikely that you will be able to start it by hand. A regular electric starter works OK on mine.

The motor will get a lot nicer after 2-4 hours running. But try to do most of it in the air.

After you get going with it, you will find that it will not be or sound that much different from a glow engine.

You will find that gasolene stinks inside your car compared with glow fuel. You might want to try something like Coleman fuel or something like it down there if you are going to haul it inside the car.

The engine should run right around + or - 7,000 rpm. With the stock weed whacker carb you will want to use a 16-10. With the big carb you will want to use an 18-8. Remember that the engine is a torquer not an rpm engine. So if you start running it at 9,000 or so, you will find that you will have overall less power.

The engine has a stamped steel connecting rod in it and some of the counterbalancing is in the flywheel.

Use like a 12 oz tank. It will run forever on a 16 oz.

Good luck

Jim

A buddy of mine and I just converted two of these engines using the Jag parts and they turned out wonderful. The only thing that was complicated was the facing off of the flywheel to lighten it. Since my friend has machining skills and the equipment it was not to bad. He faced off the front of the flywheel and then he removed all of the cooling fins. It really lightened the engine up well. The Jag cast engine mount was very nice as was the round cast aluminum muffler that they make for this engine. One of the engines was a short shaft and the other is a long shaft. It was equally easy to convert both engines. They are both mounted in a Hangar 9 PT-19. We ran my engine about a week ago. It wouldn't start by hand but fired right up with the electric starter. It turned a Master Airscrew 16x8 classic at 7400 rpms and idled all the way down to 1200 rpm easily. I'll let you know how the flights go soon. It ended up costing about $85 for the parts to convert it. Considering I was given the engine it has turned into a real bargain. Jags website shows the engine mounted in the Dynaflite Chipmunk if you care to see it. Later, Maximus

I posted a reply to you but of the hour and being I wasn't paying enough attention and posted it as new, You might like to locate it. Sorry

Thanks guys,

That information is all good. The Bennett website is new to me. We`re shifting home in a couple of weeks and when the dust settles I`ll get started on all this.

Thaks again.

Alan W

Just had a used ryobi given to me and I'll be buying a US41 tonight. Our field has a noise restriction of 93db. Will those mufflers on the bennet web site do the job?
Edwin

AND another thing! How about a CD ignition system? Can you save a bunch of weight going with that instead of the mag.
Edwin

The B&B manifold,er,muffler,is very noisy and I very much doubt would come anywhere near a DB level of 93.Its advantages are its small and cheap.
Ijust put a Ryobi converted with a bisson muffler and B&B mount on it on my trusty mail scale and it came in at about 42oz.a CH black box and a small battery pack will run about 6oz.Memory tells me a Ryobi flywheel and coil are just about 16oz,and are displaced by the CH setup.You can do the math and comparisons to a G23,US engines 35,Quadra 35,etc....and factoring in the cost of a CH conversion decide whether its right for you.
I like the conversion since it fits in the fuse better without the flywheel,the black box and battery pack can be moved around for CG purposes,the CH unit can be used on other engines,and if I ever get tired of it can be easily sold.
My $C.04 worth......

Why not use the stock Ryobi muffler that comes on it? It's very quiet. You can remove some of the internal baffling if you want less restriction.

The only stock mufflers I have seen dont have stacks,and generally direct the hot exhaust gases and any oil at the fuse.I have modified them by brazing in a stack,and you are right they are quiet.,but they are a cheap steel stamping and are very heavy,showing 9oz on a mail scale.Removing the baffle brings the noise level back up.I have a couple put away for some experimenting in the future though.

I have also modified them by braising on stacks and such. You can also change their shape some by heating with a propane torch and hammering. Even without the baffles inside they're quieter than something like the bennet cast aluminum ones which are just deflecters and are loud.
They're worth experimenting with if you can afford the weight up front.

Ok question, how well does the carb work in the air being in back of the engine? I see a major prblem being able to suck enough air, how long is the engine total? Thanks!

Not sure what you mean,but if you are referring to the carb being buried in the cowl behind the engine and air intake to it,its not a problem IME.
Keep in mind many of our most powerful designed for purpose engines (ex,,,ZDZ,3W,DA) are set up the same way.A "cold" air intake is easy to arrange....if its needed.
I just put a tape on a Ryobi in my shop and it measures 6.5" from the rear of the carb to the front of the prop driver,with a Bisson muffler in place,with the B&B mount adding maybe 1/4" more.. For comparison A 38 cc Quadra 400,(which uses a side mount carb and muffler) in my 1/3 Spacewalker with a bell mount measures exactly the same at 6.5".

Thanks Kevin! I wasn't sure if it would draw air good enough to keep running good. The lenth is the bad thing I need a llittler shorter engine for my Tri-plane. How would compare to a 1.20 2 stoke in power?

Well I sold my large two strokes a while back and memory fades,so the best way to answer your question is to say a decent Ryobi will turn an 18x6 or 16x8 Zinger at 7000 with no problem,but will outweigh a 1.2 2stroke glow by a large margin.Trying to replace a stout 1.2 2 or 4 stroke glow with a Ryobi,even with a CH ignition is a marginal deal,and probably not a good idea if performance,such as the dreaded hover and unlimited vertical is your idea of fun.This would be the work of something like an RCS 1.4 IMO.
Gas looks better and better the farther up the size scale you go,and 1.20 sized planes are about minimum for conversion.
My C$.04 worth....

I'm looking for a replacement for a Pica T-28, I have a Thunder Tiger 1.20 2 stroke on it now but unhappy with it and kinda wondered if a Ryobi might be a awnser. Looks lighter than a G-23 qnd is a little more CC's it's a 80" span and weighs around 15lbs but with nosewheel weight is a problem.

I did a lot of work on Ryobi engines, and am/was stumped by the many changes they made to the cylinder setup, just to reduce the maximum RPM that the engine would be able to do in a weed whacker.
On the elder types, I experimented with enlarged membranes and rotary inlets. I finally got about 7000 rpm with a Menz_S 18x10. The work, and drawings of the modifivations are documented on my personal web at www.reivers.myweb.nl
The plate valve now flies somewhere in Texas. I traded it with a Ryobi engine.
I hope the information is useful.

I just recently completed a Ryobi conversion and I would like to share my experience.

I discovered that a simple piece of squared aluminum tubing makes a good engine mount for a Ryobi conversion. The dimensions can be 2.5"x3" or 3"x3" with a 1/8" thickness. Make a template for the mounting screws, transfer that to the mount and use a 2" hole saw to cut an opening for the carb.

I also used aircraft ply to create the carb spacer. After tracing the shape using a carb gasket I cut the spacer using a scroll saw. I then used 30-minute epoxy to seal the wood. To ensure a perfectly level spacer I placed it, when wet with epoxy, between two flat steel surfaces and placed 50 lbs of weight on them. This pressure resulted in a flat glass like finish on the spacer.

The only things I had to pay for were the prop hub and additional gaskets. I balanced the flywheel but I did not machine the fines. The stock muffler does cause some back pressure but it does allow you to pass any noise testing.

I hope this helps.

Norman

Side view of Ryobi engine mount with firewall mounting plate

I have a ryobi 31cc in my Dynaflight PT 19 and it flies great. I bought it at the huntsville swap meet, it has conversion parts from Jagg engines. I don't know if Jagg converted it or someone just used Jagg parts. It will start by hand, but is real hard to start that way. It starts easy with a starter. It turns about 7200rpm with a 16 x 8 prop. It pulls the 89" PT 19 great, but is not a speeder by any means. It is my first gas engine and I would definatly buy another.

fossil

fossil,
That's a sharp looking PT 19. What is the weight? Can you do some mild aerobatics with it?

It weighs about 12lbs and thats weighing it on a bathroom scale so it could be a little off. Since it is my first giant scale airplane the controls are real mild till I get over being nervous flying it, but I am sure if you increased the throws some it would do some mild aerobatics.

Thanks,
fossil

Here's a shot showing how I made my mounts and the homemade muffler. I'm getting 7100rpm now on a Zinger Pro 18x6. Here's a tip, if your motor starts going rich when you fully open the throttle (4 cycling), clean your spark plug! Mine started doing this with only about a gallon of fuel run through it on the test stand. Cleaned the plug and regapped to .018 and it's running like a champ now. The homemade muffler gave me a little over 500rpm increase.