Two seat helicopter build.

Jake2465

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Hi everyone,

I decided that I would go ahead and start posting pictures and updates on my helicopter build. I have been sourcing out critical parts for it for the last couple of years and am now in the position where I can begin welding the main frame together.

Here are some of the features of this helicopter:

The main rotor head is based off of a Rotorway Exec. This is the type that has a underslung head with two elastomeric bearings housed within a couple of blocks that are part of the feathering shafts.

The main blades are the same airfoil as the Exec except that unlike the exec, mine will turn CCW. The blade straps are the same as the Exec as well.

The engine is a Subaru EG33. It's stand alone fuel management system will be a Simple Digital Systems EM-5F. I had put a lot of thought into whether I wanted to go with the EG33 or go with the EJ205 / 207. After conferring with a couple friends on the subject, I had decided that the EG33, although heavier, was the more reliable option. This was mainly due to more displacement and thus requiring less cylinder pressures at the required HP for hover.

The main frame will be the standard 4130 tubing and have a .065 wall thickness. This will be the first thing that I will need to get going on. Without the main frame sitting there on my hangar floor, it will be hard to make any progress.

The landing gear will also be made out of 4130. I was planning to get spring steel for this, but I had received some advice from others and they mentioned that 4130 had proven to work just fine for this application.

sprag clutch and main upper sheave.jpg

Main blades.jpg

EG33.jpg
 
Cool!
I'll be watching
popcorn.gif
-brino
 
Great project. Will the engine have individual throttle bodies, or go to a common center location? Mike
 
Great project. Will the engine have individual throttle bodies, or go to a common center location? Mike

Good question. The EG33 has a really heavy aluminum intake manifold. I think it must weigh something like 30+ lbs. This question was also related to the computer and fuel management, so I will explain that one as well. I wanted the input of some other folks that have had success with automotive adaptations for aviation use. Originally I was thinking about trying to use the OEM computer and harness, but I was told this would not be a good idea and even more so for a helicopter. The owner of Simple Digital Systems has a good reputation on the homebuilt aircraft forum, so I listened to what he had to say. He said that the biggest problem with trying to use OEM was that the computer could easily be put into limp mode if it did not like what it was seeing. The other problem was that the very same computer would need to be tricked into thinking the car transmission was still connected to it since it ran that as well. Basically, the outcome of using OEM was about as good as a dice roll.

The answer came from what his business worked with. Apparently they have already done EG33 aero conversions with their custom fuel management systems with success. SDS has equipped many aircraft owners with reliable fuel management. This was the first time I had heard about SDS and I liked what I saw. Another important advantage was that I could custom make my own intake manifold (reduce a lot of that weight) and use a single throttle body. I was told that good success came from a 75mm throttle body from something like a Ford mustang.

The engine will have a normal intake manifold with plenum. This is because the ITB, although bad to the bone, would pull my torque peak over to the upper end of the rpm range. The OEM manifold is actually pretty well proportioned for the constant rpm that I am wanting to run the engine at in the first place (around 4000) with it's intake runner length.

I spoke with another fellow about the EG33 and he was bit of a specialist with these engines. He told me that these engines are actually very reliable, provided that adequate oil cooling is available. It would seem that these engines produce a lot of heat when running at a relatively high rpm for long durations. If the oil is allowed to get really hot, then the engine starts to suffer from improper lubrication. Also, it was found that the higher rpm ranges would cause the cylinder heads to get water cavitation. This was caused by the thermostat, so I was advised to remove it.

Another thing I may try to add would be a 2 quart oil filter to increase my oil capacity. It would be much simpler to just screw something like that onto the oil system instead of making a custom oil pan. So much of what I will need to do is already custom o_O.
 
Yes, I think a longer runner will serve you better for your use. A light aluminum tube intake with a box plenum would be fairly simple to fab up. On my performance V8 builds I generally run an extra quart of oil over stock with the addition of a windage-tray, and sump baffling, but that may be more problematic with the flat 6. A dry sump oiling system could be beneficial, especially from a cooling, and oil volume standpoint, but would add quite a bit of complexity/expense to the equation. You might want to check out these aftermarket pan options, Or modify your existing pan to suit. Mike
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Interesting project indeed.

I've been flying my Rotorway Exec 162F for nearly 18 years.

Curious what main blades you are using? As you know, the Rotorway blades are non-symetrical and you can't simply turn them upside down and run them "backwards".

Incidentally, you may want to rethink the main rotor lead/lag adjustment mechanism. It's probably the only thing I don't like about my RW.
 
Good question. The EG33 has a really heavy aluminum intake manifold. I think it must weigh something like 30+ lbs. This question was also related to the computer and fuel management, so I will explain that one as well. I wanted the input of some other folks that have had success with automotive adaptations for aviation use. Originally I was thinking about trying to use the OEM computer and harness, but I was told this would not be a good idea and even more so for a helicopter. The owner of Simple Digital Systems has a good reputation on the homebuilt aircraft forum, so I listened to what he had to say. He said that the biggest problem with trying to use OEM was that the computer could easily be put into limp mode if it did not like what it was seeing. The other problem was that the very same computer would need to be tricked into thinking the car transmission was still connected to it since it ran that as well. Basically, the outcome of using OEM was about as good as a dice roll.

The answer came from what his business worked with. Apparently they have already done EG33 aero conversions with their custom fuel management systems with success. SDS has equipped many aircraft owners with reliable fuel management. This was the first time I had heard about SDS and I liked what I saw. Another important advantage was that I could custom make my own intake manifold (reduce a lot of that weight) and use a single throttle body. I was told that good success came from a 75mm throttle body from something like a Ford mustang.

The engine will have a normal intake manifold with plenum. This is because the ITB, although bad to the bone, would pull my torque peak over to the upper end of the rpm range. The OEM manifold is actually pretty well proportioned for the constant rpm that I am wanting to run the engine at in the first place (around 4000) with it's intake runner length.

I spoke with another fellow about the EG33 and he was bit of a specialist with these engines. He told me that these engines are actually very reliable, provided that adequate oil cooling is available. It would seem that these engines produce a lot of heat when running at a relatively high rpm for long durations. If the oil is allowed to get really hot, then the engine starts to suffer from improper lubrication. Also, it was found that the higher rpm ranges would cause the cylinder heads to get water cavitation. This was caused by the thermostat, so I was advised to remove it.

Another thing I may try to add would be a 2 quart oil filter to increase my oil capacity. It would be much simpler to just screw something like that onto the oil system instead of making a custom oil pan. So much of what I will need to do is already custom o_O.

I own a gyrocopter... with a Subaru engine... note the gyro world is gravitating towards the Yamaha Genesis 'sled' (snowmobile) engines... that is another thread.

I did some research years ago on adapting automotive engines to aviation... here is the fruits of my research in a nutshell:
Automotive use is varied RPM, with medium loads...
Aviation use (and helicopter is the extreme of this); is high RPM with high load!
So how to modify an engine to handle that load and RPM???
The majority of heat (damaging heat) comes from the 'bottom end' of the engine (crank, rods, cam)...
When you build the engine, put .001 over bearings in it... to achieve the loosest clearances that are still within specs...
Then mount the largest high volume oil pump you can find (suggest to research the brand for reliability).
Then mount an external oil cooler (suggest one in airstream... as opposed to something in the engine coolant stream).
The result is: more oil moving around for a given RPM... thus more moving heat away from the bottom end of the engine.

I read of 4 cyl subaru engines... EJ25's... being built to 250-275 HP... and running it reliably!

On the engine computer... IMO you are on the right track... the Subaru computer monitors too many things; like whether a door is open, what gear the tranny is in, etc... ANYTHING it does not like... the engine goes to idle RPM...
NOT exactly what you want at a couple thousand feet AGL... :)
 
When you build the engine, put .001 over bearings in it... to achieve the loosest clearances that are still within specs...

Used crank shaft that averaged about .0003 from max limits, check :cool:.

Then mount an external oil cooler (suggest one in airstream... as opposed to something in the engine coolant stream).

19 row oil cooler, check :cool:.

I was advised that oil cooling is the bane of EG33 engines. They like to get rod knock if the oil is allowed to get too hot. So On top of the oil cooler, I will probably make this thing a 7 quart system. I figure if I can maintain 200 - 220deg F, then I should be alright.

My oil of choice will probably be Amsoil due to the constant rpm and heat generated.

Curious what main blades you are using?

I believe these may have been a set of blades with the roots just moved to the opposite sides. I looked at them real close and noticed that indeed when turned CCW (trust me, I wondered about that too), the upper air portion of the air foil has more curvature to it than the lower portion. I got this from simple drawing a chord line from leading edge to trailing edge of the blade tip and whipping out the caliper to make sure my eyes were not tricking me.

The guy I bought them from had no issues with the blades. His helicopter was also a custom homebuilt jobby with a Subaru engine. He just opted for a lighter set of composite blades and I was fine with that because I wanted blades with some mass that would allow for less hair raising autos. If I recall, each of my blades weigh around 33lbs.

19 row oil cooler.jpg
 
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