DougT

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A couple weeks ago I bought a slightly used H9 Funtana. Many people on this site(3D forum) are running Saito 100's on it and the AUW is 5.75-6.25#. I think I can build an Echo 21cc gasser and use some lightening techniques from the electrics I've built to keep the AUW the same. I posted my idea in that forum and not many people thought it could be done. I'll document each step and parts used. When successfully finished I'll also be sure to post in the 3D forum.

If anyone has any ideas I've missed, please post them.

Here is the starting conversion. Steel prop hub, alum backplate mount. 66oz. starting weight

My goal is 30-32oz COMPLETE.

DougT

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Here is the same engine with the beginnings of a super light muffler, cut down carb spacer, alum prop hub.

DougT

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Here is the carb spacer. I removed the two short, inner(cylinder side) mounting bolts and will order Ti bolts that go all the way through. This also rotates the carb so the throttle is a straight shop. It started out at 1.75oz. and is now at 0.5 and will end up a little lighter after the mill gets done with it.

av8tor1977

My Feedback: (6)

Well, first I want to say that I agree with the others that the plane is too small for a gasser conversion, but...

If you insist, you should use the older 23.6cc Kioritz if you can find one. See the "Don't forget the echo..." thread for lots of info. (You will have to do a search for it.)

Good luck, and please keep us posted.

AV8TOR

DougT

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av8tor,

I would like to find that 23cc engine but I had 2 of these. These also seem lighter as they only have two cylinder mount bolts and I think the bigger cc ones have four.

I am having ANeat weld a muffler for me. It should be light. The stock one was close to 9oz where the parts for the alum one weigh under 1.5oz. The prop hub in the second pic weighs 0.5oz.

smokingcrater

something else you may have not thought of... 3d planes are not overbuilt, by design they need to be light. pretty good chance that engine is going to rip the plane apart from vibrations... (I just fired up my homelite 25cc on my stinger 1.20 this weekend, pretty much destroyed what I thought was a great glueing job on the firewall. now it is completely glassed with three layers of cloth.)

DougT

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Tonight I went over to a friends house and used his lathe/mill. Took a bunch of weight off.

DougT

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The cases started out at 12 oz. for the front and rear combo. Now they're down to 7.7oz.

DougT

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The cylinder started at 9.5oz and now is 7.75oz.

DougT

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The carb runs the engine very well but was porky. So, it went on a diet. I milled away 3 surfaces. Down from 3.75 oz. to 2.75 oz.

DougT

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Found these plugs at the friendly local saw shop. Honda/NGK CM-6 plugs. I removed the porcelin(sp) from an old plug and threaded the inside. Med. locktited it in the cylinder and milled away the top for a smooth plug adapter. The stock plug was 1.2 oz. and the CM-6 is under 0.5 oz.

tkg

My Feedback: (1)

Before you spent all this time making it lighter, you should have ran it and see if it has enough power to do what you need.
A feather weight engine is no good if it won't even pull up its own socks
FWIW The Poulan 18cc Feather weight is also made as a 21cc and a 24cc too. The Poulan 25 is a different engine.

mikenlapaz

Share you engine's weight as it is? Too lazy to due as the subtracts and I'm sure you have it at your fingertips.
What did the other end of the crank look like and what does it look like now? Hollow?

ZAGNUT

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just read that funtana thread and it seems to me that you're on to something good. when considering the weight of the saito+mount+onboard glow power+heavier fuel load you might not be any heavier. and i doubt a saito is any smoother running than the echo. never tried a 15x6 on one of these but it should rev somewhere between 9-10k, which is right where this engine starts making power. have you tried this prop yet??

here's a couple things you may have missed:

the DA/3W plug boots are nice and light and fit the cm-6

you can also save some weight by tossing the mount. just use 4 bolts from the backside of the firewall straight into the engine case.

the rear stub of the crank can also be cut off right at the bearing and the bore for the oil seal plugged. i use the top of an aluminium body from an old capacitor, see the pic.

that prop hub looks SCARY to me!! i would use at least 16mm rod and fit it around the crank. relying on that little threaded stub to keep everything together is asking for trouble.


dave

tkg

My Feedback: (1)

ZAGNUT is right about the prop hub, it will alow to much flex and sooner or later the crank will break at the end of the threads.
CH has a prop hub that seats on the taper and uses a stud for the prop.
Another thought put the engine togather and look at the exhaust port. I think that the piston goes below the edge of the port. You can open up the lower edge of the port ( it won't change the exhaust timing) and the engine will run a little better.

DougT

My Feedback: (1)

I ran the Echo last year and it is very smooth. I'm guessing that it has less vibration that a Saito 100. I ran it with a 15-8 and was getting around 7400 rpm. If it wants more prop, I'm thinking the MA 3 blade 16" cut to 15". Would look very cool. As far as changing the ports, I think I'll leave it alone unless is seems underpowered.

I agree on the prop hub. I already sent off to have a new one made that fits over the taper and is thicker.

Weight is at 18.7 oz. That doesn't include the crank, piston, muffler, bolts, or gaskets.

Taylorcraft_ASEL

Doug,

Keep up the good work! Whether this works for you or not, you are sharing good and useful knowledge. I applaud you for attempting to do what some folks say is not possible. Keep the updates coming!

Ken

DougT

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The overall length of the engine is too long and will put the prop about 1/2" forward too much. I traced the mounting footprint and cut out the firewall, 1/4" spacers, and a new "rear firewall". This will all be epoxied/bolted together to recess the engine 1/2" rearwards.

ZAGNUT,

I am already mounting the engine by the case holes. The pic you posted has four while mine has three. Should be very strong and light.

DougT

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I weighed the crank/rod and it is 7.5 oz. The piston/pin is 1.5 oz. As ZAGNUT mentioned, cutting off the rear of the crank should save close to an ounce. I will leave the piston/counterweights alone as not to effect the balance.

That puts the AUW @ 26.7 oz.

Right now I'm taking all bolt measurements and am looking into different fasteners (Ti). All the stock bolts weigh about 3.6 oz. Some shorter titanium bolts will drop that weight to 2 oz. or under.

captinjohn

How about using a real light glow fuel carb....then you could use gas or glow fuel and save the weight of that heavy walbro carbby! Keep the good ideas and photos coming. Capt,n John

Taylorcraft_ASEL

Keep in mind that because it is gasoline, you can leave a pound of fuel "on the ground"

Gowge

Doug, this is a kewel project - lookin' forward to your progress reports.

GOOD LUCK!

DougT

My Feedback: (1)

Captn'

Do you mean a normal 2-stroke glow carb such as an O.S? Maybe a 1.08 or 1.20 size.

captinjohn

Doug....Yup Just about any large glow carb may work. You may have too just experiment to find the ones that work the best. Seems like I read a ASP carb works ok and the price is right.

DougT

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Captn'

What about the lack of pumping action in the glow carb? External fuel pump?

These are the pieces of the muffler. 1.5 oz. in the pic.