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Two seat helicopter build.

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Jake2465

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#1
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.
 

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kd4gij

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#2
Sounds like a fun but lengthily project. I will be following along.:beer mugs:
 

FOMOGO

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#5
Great project. Will the engine have individual throttle bodies, or go to a common center location? Mike
 

Jake2465

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#6
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.
 

FOMOGO

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#7
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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jmarkwolf

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#8
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.
 

GA Gyro

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#9
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... :)
 

Jake2465

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#10
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.
 

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Jake2465

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#11
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.
I have been putting some thought into that rotor head. I think I like it so much because of it's simplicity, and making a clone head would not be too hard. The only part that would prove to be a good challenge would be those two 2.5deg holes for the feathering shafts. I would probably send the head out to a more capable shop for that part. My default line for businesses when they ask what its for, I always say it's for a "hovercraft" :rolleyes:. that way they don't loose their minds and boot me out the door.

The lead-lag issue is still one I have not figured out. I like the simplicity and that makes me not want to start articulating the head too much. I really don't want to begin putting rubber bumpers and things like that up there that absorb and release energy for lead-lag. It may be good to hinge that axis on a bolt, but it would need to be a hefty bolt and with the blade straps being used, I am not exactly sure how to do it. Last time I calculated it, each blade would pull about 16,000 lbs on the head at 520rpm.
 

Jake2465

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#12
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.
Would you happen to know how I could get a hold of the drawings for the rotor head? I have PDF files of the Rotorway build manual, but I noticed that they are not comprehensive manuals. There is almost no information about the particulars of the head. All of the information I was able to get came from my AP school happening to have a donated Rotorway rotting away in their building. I don't have the full picture though.
 

GA Gyro

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#13
Yeah... that oil cooler looks like it will keep the engine cool... I would definitely have an oil temp gauge though... :)
And I like your idea of an extra qt or two of oil in the system.

On the rotor head... that is obviously the magic part that keeps you from falling from the air like a rock... :blue:
I think I would consider finding a used low hour one from the factory... rather than attempting to make one in your machine shop...
I have made rotor heads for gyro's... prefer the 'sport-copter' design...
I decided it was just too risky... better to let the pro's build that crucial part... :)
After all... in experimental aviation... one only gets 'one' accident... :eek:
 

Jake2465

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#14
I think I would consider finding a used low hour one from the factory
I can't argue with that wisdom. :cool 2:. The one real nice thing about that head is that it uses those elastomers. I planned to buy those from Rotorway. I believe they are around $500 a piece. The only other option I know of would be to use matched angular contact bearings that are stackable. Besides that getting expensive real fast, the other issue is brinelling on the bearing surfaces from constant minimum feathering movement. The elastomers seemed like the best and easiest option to deal with.
 
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Jake2465

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#15
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.
Thanks for the link :). I checked out the site and it appears that they do not have anything off the shelf that I can use for the engine. The EG33 has a 17 bolt hole pattern for the oil pan.

I am not real familiar with a dry sump system, but it would appear to add weight and complexity to the engine. I would feel that going that route may be something to try after the helicopter is known to fly so that variable is not introduced along with all the other uncertainties.

My weight goal will be to try and keep the helicopter under 850lbs dry weight.
 

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#16
Jake, you should try to keep your oil temp above 212 deg., to boil off condensation in the crankcase and prevent the build up of acids in your oil. Mike
 

7milesup

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Thanks for the link :). I checked out the site and it appears that they do not have anything off the shelf that I can use for the engine. The EG33 has a 17 bolt hole pattern for the oil pan.

I am not real familiar with a dry sump system, but it would appear to add weight and complexity to the engine. I would feel that going that route may be something to try after the helicopter is known to fly so that variable is not introduced along with all the other uncertainties.

My weight goal will be to try and keep the helicopter under 850lbs dry weight.
Jake:
If you look at a lot of the LSA's with the Rotax engines, I believe that most of them are of dry sump configuration.

I should ask my nephew about the high performance end of things. They run 540 cubic inch engines at around 9500 rpm with a pretty decent size blower on it. 2000hp roughly, but he only has to run it for 30 seconds. LOL

Also, have you flown a heli before? ;)
 

Jake2465

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#18
Also, have you flown a heli before?
Yep, I sure have :). Got my license for it. Pretty much my calling in life and if the market outlook for helicopter pilot was not so bleak, I would have gone all the way to CFII. Instead, I settled for making it a hobby and going for aerospace engineering. That way I can feel good about myself designing a bolt for the executives that make all the money :rolleyes:.

:D:D:D HELICOPTERS:D:D:D
 

Jake2465

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#19
dry sump configuration
With weight being such an issue with this thing, I don't know if dry sump would really be that much of a benefit. Heat can be mitigated through the use of a good sized cooler and volume can be added just as easily and I would be surprised If I ever pull 3g in that rig. I wont be doing any "hold my beer" maneuvers because that's a good way to die.

I don't know, I guess I feel that dry sump is way overkill for what I am doing. I am asking the engine to run 165hp all day long. That's a fair bit of continuous power for 3.3L, but I would have been worse off with the 4 cylinder variants.

I plan to run my engine stock at first and see what happens. The EG33 had 230hp from the factory at around 5400rpm. Now, I highly doubt that engine could ever run that for any real duration (in the car engine bay with OEM plumbing) because of lots of heat being generated, but it's good to know the limits.

Before I make the 4 belt crank sheave I will need to take the completed engine in turn key state and put it on a engine dyno. I wish I could find a stock dyno map of this engine, but I was unsuccessful. So, I will have to make one so I can see what RPM can produce my 165HP. My assumption is that 4000 may just be good enough to get me there, but I am not certain. That's at 74% of the rpm range. Probably pretty close to what that engine used to have to work with when accelerating a car through the on ramp.
 
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Jake2465

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#20
Jake, you should try to keep your oil temp above 212 deg., to boil off condensation in the crankcase and prevent the build up of acids in your oil.
Mike, I had never even thought of that :eek 2:. I wonder what Amsoil requires for minimum and maximum temps. I had planned to use "Dominator 10W-30 Racing Oil".
 
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7milesup

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Yep, I sure have :). Got my license for it. Pretty much my calling in life and if the market outlook for helicopter pilot was not so bleak, I would have gone all the way to CFII. Instead, I settled for making it a hobby and going for aerospace engineering. That way I can feel good about myself designing a bolt for the executives that make all the money :rolleyes:.

:D:D:D HELICOPTERS:D:D:D

That's awesome! I wish we lived closer to each other because flying/building a helicopter has been one of my dreams. I flew for Netjets for 17 years before losing my medical and forced retirement (note my avatar, Hawker 800XP). Now I am heavy into large RC Scale helicopters and aircraft. Actually, RC is how I got interested in aviation 40 years ago.
Sorry to sidetrack there....
 

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Jake2465

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#23
Here is the first part of the build:

I need to weld this frame half together and then weld another one together just like it. After that I will need to stand them side by side and weld in the cross tubing. This is the heaviest part of the frame with its .065 tubing. Above this frame will be a 4 link strut that will hold the main rotor mast still. The top of the 4 link system will have the main bearing that will need to hold the load of the whole helicopter. This will allow the transmission to only worry about driving torque.

For reference, the bottom tube of this main frame is 6ft.
 

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Jake2465

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#24
4130 is some beautiful welding stuff. I am going to be using ER-70s-2 filler rod. I was advised that I could weld the frame together with tig, but I would want to go back over the welds with oxy acetylene and get them cherry hot and then let them air cool so they don't crack from engine vibrations.
 

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rwm

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#25
I am told that arc welding will magnetize aircraft frames and mess up the compass? True? With GPS do we care?
Robert
 

Jake2465

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#26
I am told that arc welding will magnetize aircraft frames and mess up the compass? True? With GPS do we care?
Robert
I would not fly X-country without a GPS. trying to look at a map and use both arms and legs to fly the machine is not exactly fun. Never heard of the arc welding magnetizing frames enough to cause compass issues. The obvious one was not to put literal magnets near a compass.

The one that made me have to ask if It was a joke was when I was told that mineral oil is flooded inside the frame tubing for corrosion prevention.
 

jmarkwolf

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#27
I can't argue with that wisdom. :cool 2:. The one real nice thing about that head is that it uses those elastomers. I planned to buy those from Rotorway. I believe they are around $500 a piece. The only other option I know of would be to use matched angular contact bearings that are stackable. Besides that getting expensive real fast, the other issue is brinelling on the bearing surfaces from constant minimum feathering movement. The elastomers seemed like the best and easiest option to deal with.
As far as the rotor hub, the factory does not publish these drawings. The bearing blocks and aligner blocks are also a critical part of this system.

RotorWay parts have suffered a significant cost increase recently, so the elastomerics may be much more costly now.

You'll likely need to demonstrate that you are a Rotorway owner before the factory will sell you parts. Definately don't mention you're building a ship from scratch. For that matter, don't even mention that when trying to buy parts from automotive/truck/tractor distributors. Many will refuse to sell you parts if they know the application.

You should also join ROG. It is the biggest/oldest repository of info available on the Rotorway helicopter. Link below:

www.rotorwayownersgroup.com

Be advised, this ship has been flying for decades and still needs some tweaks. Building one from scratch is a seriously daunting task.
 

Jake2465

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#28
That's good to know. The only Rotorway-ish components for this helicopter are the head, main blades and sprag pulley sheave. The rest of it is custom. But, those elastomers will be critical for me to get.
 

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#29
Cool project. Will be following.

I'm a long time RC guy & dabbled on the dark side (helis) for a bit. I loved the mechanics & technology but it got to a point when I started doing aerobatics the heli mode left thumb collective management was not properly re-booting with airplane mode. It was only a matter of time before one or both was going to bite the dust.

Hey, do they sell flybarless controllers for 1:1 scale yet? LOL
 

petertha

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#30
..I could weld the frame together with tig, but I would want to go back over the welds with oxy acetylene and get them cherry hot and then let them air cool so they don't crack from engine vibrations.
Can you elaborate on this? I don't have a TIG yet but many late nights of YouTube lurking, seems like TIG is the 'metal glue' of choice for all sorts of vehicles in tough or similar vibration environments - carts, race car chassis, motorcycles... Aside from some aluminum alloy bikes I don't see much mention of post heating unless related to alignment tweaking. But I am a complete newb. Is it because of thinner wall thickness 4130 tube more prevalent in aviation or..?
 
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