Two seat helicopter build.

I think part of it is the chrome-moly 4130 tubing and other shapes that are usually seen on aircraft weldments. In older days, and even now, much aircraft welding is done with oxy/acetylene gas welding to a high standard. The joint is preheated, then welded, and then post heated for stress relief and maintaining the proper grain structure. It is probably a good idea to do it with TIG welds as well. The structure is highly stressed, there is lots of vibration, and processes that can leave heat affected areas that can crack from poor grain structure need to be avoided.
https://www.millerwelds.com/resourc...eneral-motorsports-and-aerospace-applications
 
I won't be building one. as I ride in enough choppers over the years for me to not like them ,However on a positive not this is a really cool project and will be wishing you luck on the way and keeping a look in to see the progress. This will be an interesting project to watch and I'm sure will bring you much satisfaction and joy when this beast is in the air
 
The original air frames for the Rotorway kit are all oxy-acetylene welded, at least they were back when I bought my kit.

Only had 1 weld crack in nearly 18 years.
 
petertha said:
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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Post heating is used to anneal the welds. Welds generally make for strong but hard and britle joints. Frames with engines tend to vibrate and that can lead to cracked welds. Old time acetylene welding would heat a large portion of the metal, so a side effect was that it took longer for the welds to cool down. This helped in keeping the welds safe from cracking. Tig welding heats a small area really hot, so it cools faster and that is not ideal.
 
I was reading about helicopter heads. I had no idea they were so complex. I never envisioned a need for lead/lag. Why is this? Strictly Coriolis effect? What happens to performance if you just build a simple head with out this? I assume that is where the elastomeric bearings come in?
Robert
 
rwm said:
I was reading about helicopter heads. I had no idea they were so complex. I never envisioned a need for lead/lag. Why is this? Strictly Coriolis effect? What happens to performance if you just build a simple head with out this? I assume that is where the elastomeric bearings come in?
Robert
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Movement of the helicopter forward, backward, and side to side leads to differential blade speeds through the air on the advancing and receding blades. The speed differential makes the helicopter want to roll. The pitch angle of the blades (angle of attack) is changed during each revolution to compensate for that. Changes in lift and drag happen each revolution as a part of this, which makes the blades speed and slow differentially. Without room to move and damping, the rotor would soon self destruct from fatigue.
 
rwm said:
I was reading about helicopter heads. I had no idea they were so complex. I never envisioned a need for lead/lag. Why is this? Strictly Coriolis effect? What happens to performance if you just build a simple head with out this? I assume that is where the elastomeric bearings come in?
Robert
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Because of the way the blades operate in a phase around the axis, the blades are always changing their angle of attack. Its very hard on conventional bearings to only move a couple degrees back and fourth while getting several thousands of pounds of axial load. Elastermeric bearings for these helicopters consist of shim stock brass and very thin neroprene rubber layers all sanwiched together. Make a thousand layers and that stack of stuff can move radially a few degrees back and fourth. The axial loads that they can handle are amazing.

The lead lag thing is not as crittical, but still important. Most times the lead lag only is like a degree or something around there. Its not much. Blade drag and lift are some of the reason for lead lag. If no joint is incorporated for it, then physics dictates that the blades will need to flex a little bit to perform the same operation. If not, then vibrations will be felt.
 
The lead/lag adjustment on a two-bladed helicopter is for assuring the rotor system can be balanced (180 degrees apart, nominally). Otherwise, the resulting imbalance, will drive you crazy, and wear out parts prematurely, and can be dangerous.

Visualize a string pulled taught from the outboard tip of one blade, through the "center" of the rotor shaft and pulled to the outboard end of the other blade. If the blades are too far to one side of that string or the other (not 180 degrees apart), an imbalance will occur. Further, there needs to be an adjustment mechanism because it's not only the geometric requirement of the two blades needing to be 180 degrees apart (nominally), but very small changes in weight of one blade or the other, will affect the this balance, such as uneven paint wear on the end of a blade vs the other.

A fully articulated rotor hub (three blades or more) is vastly more complex. If the imbalance described above occurs on a fully articulated hub the whole ship can self destruct in a matter of seconds. Do a Google search on "helicopter ground resonance".
 
jmarkwolf said:
The lead/lag adjustment on a two-bladed helicopter is for assuring the rotor system can be balanced (180 degrees apart, nominally). Otherwise, the resulting imbalance, will drive you crazy, and wear out parts prematurely, and can be dangerous.

Visualize a string pulled taught from the outboard tip of one blade, through the "center" of the rotor shaft and pulled to the outboard end of the other blade. If the blades are too far to one side of that string or the other (not 180 degrees apart), an imbalance will occur. Further, there needs to be an adjustment mechanism because it's not only the geometric requirement of the two blades needing to be 180 degrees apart (nominally), but very small changes in weight of one blade or the other, will affect the this balance, such as uneven paint wear on the end of a blade vs the other.

A fully articulated rotor hub (three blades or more) is vastly more complex. If the imbalance described above occurs on a fully articulated hub the whole ship can self destruct in a matter of seconds. Do a Google search on "helicopter ground resonance".
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Indubitably :cool:
 
Jake2465 said:
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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Hmmm...

Something to think about...
The EJ22 engine has had an issue with the business end of the crank 'snapping off'... literally!
Might want to plan for a support bearing at the far end of your drive arrangement... unless the power will be Xmitted to the transmission straight inline (similar configuration as an auto to tranny).
Designing, fabricating, and mounting a frame to carry a bearing at the far end of the drive pulley (sheave)... would not be difficult if it was planned in from the beginning... IMO the frame must be mounted to the engine!
IMO I would shoot for a little excess HP... say 175... :)
No substitute for HP... as there is no substitute for CU/IN... :grin:
 
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