Tandem rotor gyroplane

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Kev C

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Jan 29, 2013
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17
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Welch, Minnesota, 55089
Joe,
Thanks! I have a Little Wing project in the wings currently but work (seasonal farm hand in N. Dakota & 160 acres I farm myself up there) gets in the way of my building habit. The tandem rotor is on my bucket list but your efforts have stirred new interest in the project.
 

joe nelson

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Jan 9, 2008
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265
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Cincinnati,Ohio
Just an update to the tandem project. I have had a large amount of non-related chores this winter and little has been done on the tandem. Hopefully, I can restart the work on the jig mount to give another axis of freedom.
 

joe nelson

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Jan 9, 2008
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Don,

I hope that it doesn't take to long, lol. The uncommanded yaw has always been a pain. I'm using the same ratio for size as the Chinook's (7to1) aft pylon. The aft pylon has 7 times the area as the front even though it's lower. With this jig, I'm doing captured testing that saves much time. There's no more going to the parking lot to end up with a broken model to rebuild.

The collection of parts has started for the next phase of this project. Gearboxes have been found that will meet FAR part 27 requirement for 2 times the operating rpm...plus they are reasonable priced. They are rated for up to 1000 rpm continuous with 200 pounds of torque. With the normal operating rpm of 350-400 rpm that is great! The 200 lb. torque rating it would allow the ability to pre-spin the rotors.

BTW, how's the MC4 rebuild going at the museum? I love that little bird!!
 

joe nelson

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Jan 9, 2008
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265
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Cincinnati,Ohio
I have the patent drawings for the MC4 and how amazingly simple it is built. On the other hand, the Chinook is the most complicated animal that I have ever seen. I got a look into the SAS closet on a MH 47, last year, and you need to be a f'g genius to fix the thing! I have often wondered how a Chinook would fly using a servo-flap control rotors making the hydraulic system unnecessary.
 

joe nelson

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Jan 9, 2008
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265
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Cincinnati,Ohio
I have been struggling with my gearbox selection for some time. The main reason is that I can't understand the manufacturer's charts. The major requirement, for my project, is that it except a 30 hp pre-rotation system at 350rpm. The torque is the limiting number at the 350rpm speed. As I read the manufacturer's charts no gearbox will handle the low rpm and hp that I require. The charts from several manufacturers show only a fractional hp limit at 350 rpm but a greater hp at a greater rpm for the same gearbox. This is confusing to me!
 

jhausch

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Dec 10, 2008
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135
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WI
Can you give us an example of what sort of charts and which companies gearboxes you are looking at?
 

joe nelson

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Jan 9, 2008
Messages
265
Location
Cincinnati,Ohio
I was looking at the information for the ZeroMax, right angle, 1/1 ratio, 3 way gearboxes. My requirements are 30hp and 350 rpm (471ft# torque). The C805806 gearbox rated at 400 rpm, 3.3 hp and 525 ft# of torque. In the notes, the gearbox is rated 5100 ft# torque for 1000 cycles. Is the 3.3hp/ 525 ft#torque a continuous rating? Does the 5100# of torque mean a higher hp can be used but with a shorter time than the 3.3/525 continuous rating?
 

Kev C

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Joined
Jan 29, 2013
Messages
17
Location
Welch, Minnesota, 55089
Greetings Joe, I see you're looking at gearboxes. Guessing you are planning to have direct shaft to each rotorhead (1:1)? I think that would require heavy hi-torque shafting. What about using reduction at each head? (cog belts?) The coupling shafts could spin faster & be lighter with much less torque. 90 deg gearboxes could be smaller.
Just picked up 90 Mac eng with good looking cylinders, hope to be back in the air this summer!
 

joe nelson

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Jan 9, 2008
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Cincinnati,Ohio
Kev,

The reason for the gearboxes is to couple the rotors with each other so I can overlap them and to maintain the same rrpm. With an overlap the airframe can be made shorter which makes for a lighter weight. Also having coupled the rotors makes for a similar rrpm in all attitudes. Coupling makes pre-rotation easier by using only one power source for both rotors.
 

Kev C

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Jan 29, 2013
Messages
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Location
Welch, Minnesota, 55089
Yes, overlap, I agree. I'm going to have to bring my drawings back from North Dakota and show you what I have so far. (I have no internet up there) If I understand correctly are you having the connecting driveshafts turn about 375 rpm, same rpm as the rotors? (1:1) I plan to run the connecting shafts about 1500-2000rpm. This would keep torque way down so I can use much smaller & lighter shafts, 90 deg gearboxes, & gearbox mounts. This would require 4 or 5:1 gearing at both rotorheads.
 

Kev C

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Jan 29, 2013
Messages
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Location
Welch, Minnesota, 55089
I'd have to use offset-gimbal type head so I can put the large cog pully where the pre-rotator ring gear is and the small cog pully fore or aft of that. Center shaft & swash-plate type head would have to keep 1:1 ratio.
 

joe nelson

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Jan 9, 2008
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Cincinnati,Ohio
Kev,

That's correct. I intend to run all boxes at 350 to 400 rpm at a 1:1 ratio. The only modification to the boxes is to add a chip detector and temperature sensor. If needed, I'll add an oil cooler also. I figure that these features are the things that will be needed to give you a idea of the health of your equipment.

The only thing that I still have questions about is the type of blades that I will use. I like the Kaman style servo flaps for the control system and all it's advantages. On the other hand, I still believe in the "keep it simple" approach with plain ole blades.

I should be starting the full scale gyro as soon as I finish a project for my grandkids.
 

Kev C

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Joined
Jan 29, 2013
Messages
17
Location
Welch, Minnesota, 55089
Hell-o again Joe, Thank You for having patience with me. I may have assumed wrong that your plan is going to be a pusher. Is all the power from the engine going to the driveshafts or is the plan to have a prop fore or aft?
 

joe nelson

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Jan 9, 2008
Messages
265
Location
Cincinnati,Ohio
Kev,

The rotors and gearboxes aren't connected to any powerplant except for spin-up. The major reason for the gearboxes are to make both rotors turn at the same rrpm. This also permits overlap without the fear of blade to blade contact.

The engine configuration on the models were tractors but this arrangement show no more advantage on a tandem rotor gyro than a pusher engine. The only advantage of a tractor powerplant is that it's in clean air unlike the pusher but makes little difference as far as stability.
 
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