Jesse Open

Good work on the so called "rebreather" .
I have used them off and on for years on methanol fueled, glow igition engines with absolutely no negatives. Theoretical con-jecture aside, speed, idle and transition are not affected.
I have always introduced the vent products upstream of the carb intake. Works well .

Hub-spigot joint

swedge punch

Swedge forming the hub

Tube end before swedging

Intake pssed thru bulkhead

Yes, metal working is a blast, the planes are a good excuse to use the machines

I have owned several lathes over the years. The current lathe is a Clausing 4900 10" with 24" between centers. A good size for most everything I care to do. My first Bridgeport was a "M" type, the current one is a "J" model with hard chrome ways and 42 inch table.
Never owned any Chinese made machines but I have repaired a few
In this area there is a lot of very nice machine equipment often available in the used market.
A few years ago many of the public schools shut down their Industrial Arts departments. This also put a lot of clean, low time machines into the market.
Rather than using an electromechanical phase convertor to generate 3 phase power, they are both fitted with solid state Variable Frequency Drives.

My son has a huge, very well equipped wood shop with industrial level machinery and my wife's brother runs a custom cabinet and door shop. Both live nearby so woodworking machinery is a cinch.


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mitchilito

My Feedback: (6)

Wow Jesse, that is real dedication to make an intake tube! Is that a Saito 150 or 180? As I said somewhere earlier in this post I had a Saito 150 that I plumbed the case discharge DIRECTLY to the intake manifold (in between the carb and head). I expected it to destroy the required manifold vacuum but instead it made absolutely no difference and ran like a top. It was the neatest and coolest mod I ever did. The airplane I put it in stayed clean as a whistle.

I bought my Grizzly machines years ago and just love them. I used to tell people that quality-wise they were best thought of as mostly assembled "kits" because all the final finish work needed doing! The basic cast iron processing was/is fine and dandy. And I converted the mill to variable frequency drive a couple years ago - so cool.

Thanks for chiming in. Its fun to see this old thread continue on!

Jesse Open

The engine is an older Saito FA-50. Actually it only takes about 1/2 to 3/4 of an hour to fabricate a stack like that one.

Most of the older home hobby type lathes like the typical "South Bend" had fairly soft, plain iron ways. Add to that, they were rarely treated to proper waylube and it gets hard to find one that is not badly worn. The Clausing at least has very nicely finished, bright, flame hardened ways and holds accuracy well. In the meantime, I got to learn a bit about hand scraping and flaking in order to get decent accuracy with those old Logans and Southbend lathes from decades ago.

The machinery is like a hobby unto itself.It can compliment and enhance other hobbies as well.
One of my other hobbies has been Amateur Radio. I took an interest in microphones as part of that hobby, high end ribbon mics in particular.
A bit fussy to build as a typical ribbon is about 6mm X 20mm but only 2.5 micron thick. It is also corrugated and suspended very closely between two strong, magnetic poles. Between the motor element, the enclosure and the base, there are many opportunities to use machinery.As well as exercise a little creativity along the way. Much as we do with the toy airplanes.

mitchilito

My Feedback: (6)

What a work of art that microphone is! I saw a "How it's Made" on these and that inner ribbon was fascinating. Beautiful work.

I also have an amateur radio license - but only because I wanted to transmit on the 50mhz band back in the 72mhz radio control days. Sure don't need that anymore!

Jesse Open

You may be talking about the video that was put out by Rhode. An excellent video. I got my initial impetus to build ribbon mics from restoring and re-ribboning vintage mics for collectors.


BTW. I still use 50 mHz more often than not. It has been ultra reliable.


Things that work.

JohnHab

My Feedback: (1)

Hey Mitch, My 28% Jungmeister is getting to the point where I should start thinking about a engine. I have an OS 160T sitting in a box and I'm hopeful that the twin would work. Curious as to the approximate weight of your Rascal? I apologize if you already mentioned it.

Back in the day I too got my Amateur license to be able to fly 50Mhz.

mitchilito

My Feedback: (6)

Wow, I don't check back in on this old thread much, John. I was surprised to see a posting. My Rascal weighs somewhere around 14 -15 pounds. If you're using nitro (which if so I pity your poor Gemini internals) you might have enough power to satisfy you. I just could't subject these beautiful motors to the corrosion that comes with alcohol - especially if you are using any nitromethane. Yes, you can mitigate it to some extent with LIBERAL doses of Marvel Mystery after run oil - but you can never eliminate it. But if you convert to gas this engine just isn't a powerhouse and needs to be put in a lightweight airframe that doesn't require max power. That's why I chose the Rascal. It's the PERFECT airframe for this engine (in its current state) IMHO. I would guess that the gas converted Gemini 160 puts out approximately the power that the nitro powered Gemini 120 puts out - which really isn't that much!

From one old geezer to another: we're all dating ourselves when we admit to having an amateur radio license to operate at 50MHZ!

1967brutus

I can provide some real-world numbers:

At full chat and burning gasoline, the OS Gemini 160 will produce somewhere around 2 hp @7500 RPM (-ish) on practical settings, and close to 2,5 if all peaked out. As measured on the bench, Of those numbers I am sure, I converted one for a friend.
But doing so continuous will eventually fry the engine of course. The exhaust valves will start to act like glowplugs and the engine will lose power (as if it is running lean, but it isn't) and eventually that will lead to damage.

But it does not fry THAT easy. It will without too much trouble accept a decent warm-up run on the ground with subsequently a full 1 minute of full throttle climbing (what I do with mine when it has towing duty). At about 1 min 15 sec I have to reduce throttle a slight bit to not exceed the CHT limit I have set myself (and that limit has a safety margin, of course. I limit myself to a CHT of 130 degrees C, the power loss occurs at or around 145 deg C)
It will also accept "static peak RPM" all day long in flight. Static RPM rises by roughly 10% in the air, so to maintain static peak you will have to reduce throttle a bit, which in real life will result in approximately 80% of peak output, which comes down to 1,6~1,7 hp
My ASP copy does about 7400 RPM on the ground, and about 8100 in the air. If I limit myself to 7400 in the air, it won't overheat, period. It will stay shy of the 130 deg temp limit I did set myself. I have now over 60 hours and 5 seasons of rather intense use on it. It is on it's third set of sparkplugs. Valve lash remains constant (I check every 5 hours), so I am pretty sure everything is OK internally.

I run 10:1 fuel/oil ratio. I do not have hard info on whether the engine will run cooler on 20:1, but I would expect so.

Just for completeness: Regardless of what OS claims about the engine, make sure you stay well clear of 9K RPM in the air...
Prop for about 8K in flight or 7500 on the ground, tops, and throttle back when in a dive. The conrods are harder and harder to find, crankcases even harder, and the damage can be expensive.

mitchilito

My Feedback: (6)

Great info for us, Brutus! Thanks.

JohnHab

My Feedback: (1)

Thanks Mitch and Brutus. I'm hoping to come in at <15lbs. I'm at 5900' so maybe I should sell this NIB 160 and purchase Saito's new 40cc twin...Thanks

1967brutus

It won't be a powerhouse, but should fly without trouble. If you want unlimited vertical, buy the Saito, otherwise, your OS will do... My BigLift weighs 15 lbs, and is used for towing.
It is WAY overpowered for normal flight and takes a 7 lbs glider in tow to 650 ft in about 1 minute, give or take.
If I reduce power by about what I described earlier (slightloy over 7000 RPM), I can still easily maintain a 300ft/min climb with that same tow, at above 600 ft altitude.

At your locale, power loss is still acceptable by about 15%, BUT... this power loss also translates in less heat production, so your engine most likely will hold full throttle better (don't take my word for it, use telemetry and sensors to check this if you have the option).
So you should still have that 1,6~1,7 hp availlable is my estimate... Enough for 15 lbs all-up weight

mitchilito

My Feedback: (6)

I like the 40cc twin idea better, John. You'd probably have some welcome reserve of power.

1967brutus

No doubt about that, but planes can also have too much power or too much weight in the nose. More is not always better...

JohnHab

My Feedback: (1)

ok, Thanks for the input...you've got me thinking...Mitch, looking forward to the Jungmeister completion.

mitchilito

My Feedback: (6)

I thought I would touch base back here with what I've been doing lately with my little Gemini. It's still in the Rascal and working great with one exception: it wants to carbon up the exhaust valves - especially the right one. I'm adding de-caronizer (Sea Foam) to my gas which helps but hasn't eliminated the problem. I need to find a fuel that doesn't carbon up the exhaust valves I guess. It's an easy fix when they stick - I just apply a little Sea Foam directly to the valve stem an it's instantly free.

Anyway, I've always wanted to put the Rascal on floats and take it to the Joe Nall floatplane lake and I finally did it this year! It was so fantastic. I built the floats from scratch (foam and fiberglass) and they and the Rascal flew fantastic. It was a real bucket-list week for me and so much fun! See for yourself:

1967brutus

Lemme guess: You're using 20:1 fuel oil ratio?

10:1 makes that tendency go away. In the 7 years that I have been messing with small fourstroke gasser conversions, I still have to encounter the first carboned up or sticking exhaust valve in about 10 regularly flown fourstrokes and about 35 gallons of fuel.
Heck, 15:1 might allready cure it, IDK, never went there.

EDIT: Really cool vid of that Rascal on floats, and those floats really seem to perform perfect. Remarkably little spray coming from the "bows" and tracking really smooth in the water.
Also, pretty cool to catch a (brief) glimpse of the man behind these beautiful projects.