HSS will work. In a pinch, I have also cut them off with a Dremel and a cutoff wheel. They are not as hard as everyone thinks. Once you break through the surface hardness, you can hack saw them right off.

AV8TOR

I agree i cut off the long shaft on my 21cc weedeater with a standard hacksaw with ease, i don't even think i broke a sweat.

I use an angle grinder! but then that's just me!

Rich

Ok, the story so far.

I finally got round to making the propshaft. My leafblower is now starting to look like a plane engine! With the standard exhaust it weighs in at 3lb 4oz, bearing in mind that the stock exhaust weighs 6 oz! Does anyone know how much an aluminum one weighs?


Rich

Pictures so far;

That's a nice looking prop hub. I am assuming that you made it because of all the aluminum chips I see on the ground. But if you didn't make it yourself, where did you get it?

I usually gut the stock mufflers and braze in two brass outlet tubes of 1/2" i.d. or slightly larger. These mufflers weigh the same or slightly less than the aluminum mufflers you buy.

Anyway, nice work.

AV8TOR

Thanks! I made it this morning from 1 1/2" T6 bar. I tapered the inside to fit the tapered crank and cut a key into it so it's tight on the shaft and doesn't spin I just hope I don't have to take it off again! I also cut anti slip grooves onto the end so the prop doesn't, umm, slip! Yeh I suppose I better go and clean up the mess!

Do you think the crank still looks long?

Rich

Oh I nearly forgot! Regarding the exhaust, I would love to use the standard exhaust to keep the cost down but it doesn't fit in the cowl! [&o] Did you mention somewhere that the exhaust volume for 25 to 30cc engines is 700cc? I will have to design something that fits in the cowl and send my drawings to Wackerengines. I would prefer a Pitts style so the exhaust exits at the rear of the cowl but they don't really look very efficient with that sharp right angle bend?!? Am I right in thinking that way?

Rich

Oh it's a beautiful day outside and what do I end up doing? Sitting in my dungeon (basement) making airplane stuff! On the agenda today 1- fit prop nut. 2- get aluminium prop washer. 3- replace rear crancase bolts with studs so I can mount engine directly to firewall and 4- make test stand (yeh a 1/2 thick pine board!)

1 - Can't get a 3/8 24 thread prop nut anywhere so what do I do? buy any prop nut that looked right and I'll re machine it! Ok can you get a 3/8 24 tap anywhere? (I had to sell all my tools when I left England so I have had to start from scratch!) No! Had to buy a whole tap and die set from Harbour Freight (hey I'm only threading aluminium so it'll do)! Next can you get a Q drill anywhere for said tap? No chance in hell!!!! (Unless I buy a whole 100+ piece drill set for $70!!!!!!) So I had to use a 5/16 (again it's only aluminium) Well it worked althought the propnut is a tad stiff but hey at least it won't loosen! I had to drill a 3/8 x 1/4 counterbore in the propnut as the thread on the shaft didn't go all the way to my propellor.

2- Can you get an aluminium washer anywhere? Yeh right! Out with my aluminum plate and on to the lathe I went!

3- The studs were no problem and yes they will be cut shorter when the engine finally goes in the plane. Does anyone here suggest that this engine be rubber mounted or will straight onto the firewall be ok? My P47 has a fibreglass fuselage but there are blocks of ply either side.

4- The engine test stand (The plank!) was easy and I fitted the original leaf blower tank to the back of it. I now have to make up some sort of throttle linkage but I think that's it for today! I have to go and clean up now![]

Any ideas re the rubber mounting anyone?

Rich

Hi,

No, I don't think your prop shaft is too long, it should be fine. Also, I never rubber mount any of my gassers, and most people don't. No problem there either. A lot of people use an aluminum backplate mount, but I usually mount mine straight to the firewall with studs like you are doing.

That 700cc muffler volume you mentioned was in another thread about a 70cc engine. A rough rule of thumb is for the canister, or muffler chamber to be about 10 times the cylinder volume.

On a couple of mine, I have used a copper elbow and tubing to go back to a homemade canister (Pitts style) made out of thinwall steel tubing. One is on an Echo 23.6cc that turns over 9000 rpms, so it seems to work pretty good. Everyone says it sounds just like a real airplane in the air. If I can find one, I'll try to send you a picture of it later. Most all the manufactured ones you see have a hard right angle to them. I agree that this doesn't seem very good for flow, but they seem to work...

Your engine looks great. I hope you are enjoying the project. Converting the engine is the first part of the fun. The next part is getting to see the looks on people's faces when you fly the airplane, and then tell them where the engine came from!!

AV8TOR

P.S... this might be nothing more than nit picky, but I would jigsaw a hole in your test stand behind the cylinder to allow air to flow through...

People are likely to say it is not necessary, but in a cowled installation the air has to flow over the engine to exit the cowl. (Hopefully) On your test stand, air can exit everywhere but not flow through the engine cooling fins very well. Just my thoughts...

The other thing you could do is just flop the engine over so that it is cylinder up, but then you are going to cuss me because you are going to find out the bolt spacing isn't "square".

AV8TOR

Thanks again AV8TOR!

Yeh I was going to drill out the plank behind the engine as the cylinder nearly touches it but I just didn't have time to do it today. The engine has to come off so that I can de coke it and just generally clean it up and fit all new gaskets before I run it. I also have to find a place around here that supplies do it yourself cables for the throttle linkage. Yes I am enjoying it, keeps me busy during the day, even though my house is falling down around me!

Rich

Rich....your Homelite looks a lot like mine!!!! [)] Capt,n

Hey Capt'n That looks good! Sometimes I wish I had the short crank version like yours! It's lighter!

Rich

HURRAY! IT LIVES!

Well today was spent putting the engine back together, gutting out the muffler, drilling outlets in the muffler and finishing the test stand. When all was finished I tried to turn the engine by hand to get a feel of the compression (No fuel or ignition) and instantly the prop sliced my finger! Ok dumb boy put the gloves on! Fueled it connected the glow plug diver and on the first flick the engine started!!!!! The only problem now is that it wont stay running!

So here is the question On the carb there are two fuel pipes, on the tank there are two fuel lines. On the last attempt to start the engine I connected the fuel outlet from the tank into the top brass pipe (nearest the glow plug) on the carb, at the rear of the carb (rear of the engine) adjacent to the throttle linkage. the other pipe I connected to the primer bulb then to the other brass pipe on the bottom / front of the carb. Is this the right way on a Walbro WT391? I couldn't test it again as my glow plug driver ran out of charge and I won't be able to test it now until the weekend.

Nearly forgot, both of the mixture screws are 1 1/2 turns out.

Thank you.

Rich

HELP!

Ok I got it running and the mixtures set but still can only get 1/4 throttle before it bogs down and dies! Any suggestions? I was told on another thread that there is a fuel needle that needs adjusting under the cover that has four screws to let more fuel in but I don't know how to adjust the screw. Any suggestions?

Rich

First, make sure that diapragm under the cover with the four screws is nice and pliable. If not, you will never get it tuned right. They often dry out and get stiff, and have to be replaced.

That diaphragm has a spot in the middle of it that presses down on a very small lever that raises a needle valve. That lever is normally adjusted to be about level with the surrounding metal surface. Very carefully bend it so that it is slightly above the surface of the surrounding metal, then reassemble and give it another try.

AV8TOR

Thanks again AV8TOR!

The carb is brand new so the Diaphram is ok. I will try re adjusting the needle on my next day off (prob Thursday) and I will let you know. Apart from that the engine runs really well and starts on the first flip after priming! It even idles upside down with no plug driver so I'm happy with it overall. Once it's up and running I'll post a vid if your interested.

On a slightly amusing note, I ran out of gas for my Briggs and Stratton 4 stroke lawn mower so I put some of my glow mix in as that was all I had! I had to mow the lawn you know! My God I think that's the best that mower has ever run! Even on tall grass the RPM hardly dropped! (It would have stalled before as it's extremely elderly and picked up from a dumpster dive!)

Rich

P.S. Yeh I know it's probably going to wreck the carb but hey it's nearly dead anyway!

meridianclocks your doing fine work. The engine looks like my 25cc. You might want to look at Dave's Discount Motors for Walbro carbs with 11mm venturi. WA167 I believe. The stock carbs on blowers and weedies are normally small for duty on planes. Glad you are enjoying the convert.

drill bits and taps http://www.mcmaster.com/

Thanks! I'm using a WT391, I have two new ones, they are 11mm Thanks for the addy for the drills

Rich

I have some questions thats kinda simular, I have a scooter with a 33cc 2 stroke air cooled engine. I bought some new 25% nitro fuel for my aftershock and i was wonder if i could mix a bit in my scooter to make it go faster or more powerful. The fuel mix is 25 to 1, Can anybody tell me how many parts of nitro i can put in or should put in? and would it work with a spark plug?

Bio Rev: Are you going to add pure nitro or the Glow fuel you talk about? The spark ignition should work fine with glow fuel. Good luck.........Capt,n

I am gonig to add glow fuel. As for how much i'm just going to add little bits at a time until i feel a performance difference.