|Jan 11, 2013, 08:17 AM|
found myself in need of a G-62ish engine for an upcoming plane i've been drawing up so i went digging through the junk at a local saw shop. amongst all the crap there was a reasonably decent husqvarna 61 that looked like it had been run over. got it tore down and was surprised to see that the cylinder looked brand new on the outside...just a hair of black near the exhaust but the rest was bare clean metal, no oil, no sawdust. never, ever seen a saw this clean...especially not one that's 25 years old.
anyhow, got inside the saw and the cylinder, piston and ring looked very good, well run in but no scoring or globs of baked carbon. then i got down into the case and things started looking very different: major rotting of the magnesium around the crank bearings. i can only assume that this is because the bearing bores are machined after the case is painted and therefore don't have any corrosion protection from whatever nasty stuff gets put into today's gasoline. looked like just pressing out a bearing would destroy the whole case....can't use this crap.
it was then that i remembered that i have a couple of bridgeports, lathes and other machine shop related equipment surrounding me
hasn't run yet, still need to sort out the ignition, carb and get some props but the hard part is over. more pics and details to come...
|Jan 11, 2013, 09:32 AM|
was going to contour the case like everyone else does with their bar stock cases but the only rotary table i have for the mill has been in pieces under the bench for a few years now....and i'm doing all this manually, no CNC....so i chose the lightening hole method and was surprised that it actually weighs less than the contoured case would due to the very thin walls i could get away with. probably more rigid as well.
on both halves the bearing bore was counter bored for the bearing retainers which are loctited and staked in place. the front one is also pinned and the rear one also closes off the case.
|Jan 11, 2013, 10:02 AM|
decided that even though most multi screw hubs are smooth i wanted this one to have teeth. maybe a bit safer but mainly i just wanted to try doing it. since i suck at knurling i went with cut "gnarls" instead
also notice the broached keyway in the hub. don't really need it as the taper actually does all the hub holding duties but it will make it easier to re-time the engine if i ever need to tear it down. this was done on the bridgeport...actually everything was done on the bridgeport: all of the turning including the hub taper.
|Jan 11, 2013, 10:30 AM|
and some of the complete engine so far. the fins on the jug were cut way down and this saved over 4 ounces. was kinda ugly after the milling and filing and since i have no way to bead blast it back to a nice uniform finish i just hit it with high temp spray paint...hey, at least it's not "air hobbies" red
and yes, i know i'm missing the carb insulator block. i just put that carb on for the photos and to weigh it to see how it compares to other engines. i will be making up my own carb for use with methanol and it should also be a whole lot lighter than the tillotson which is exactly 5 ounces without any insulator.
so right now with the CM-6 plug, no ignition and no muffler it weighs almost exactly 64 ounces.....my ignition will add about 1.5-2 ounces and the new carb will be about 3 ounces lighter than the tillotson. mounts? don't need no stinking mounts, four screws through the firewall into the engine case with some 10mm thick aluminum washers as spacers...shouldn't add any weight. so that should put me in the ball park of the G-62 "lite", which is good considering that the zenoah probably has a lighter crank and cylinder than this engine.
how will it do power wise? don't know but since i'll be burning methanol i hope it'll at least be equal to the G-62. i've dropped the cylinder to get the squish as tight as i dare and cut the exhaust and transfers to gain back the duration lost to lowering the jug. on the degree wheel the numbers look good:
exhaust: 154 deg. duration
transfers: 118 deg duration
intake: 144 deg. duration
we shall see
|Jan 15, 2013, 04:47 PM|
Looks like a new one. Be sure to let us know if it works. I just got ahold of a Husqvarna 125B 28cc leaf blower. I'm looking to see if it can fly and worth the conversion. It is so new it looks off the shelf. Got it for $10 at a local surplus outlet, Grandview Outlets. $150 average new price.
One idea is to make it a .90 gasser heli conversion for sport flying. One or two lbs shouldn'y affect it, I hear a 90 can lift 15 lbs.
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