Why is ultralight weight so hard to make with a gyro?

[Friendly]

Chuck,
I don't want to sound like Abraham barganing for Sodom, but do you think we could go as small at 2in 6061 x .250?

 

[C. Beaty]

As it happens, Mark, the strength and stiffness of a 2 x 2 x 0.125 wall tube and a 2” round x 0.25 wall tube is about the same.

 

[Gyro28866]

If you look at pictures from Shelbyville last week, you will find a nice copy of a Benson B7M (round tube). and ultralight

 

[Jazzenjohn]

I was considering using 2 1/2" by .080 6061- t6 round tubing for an unbraced mast of with a length somewhere between that of a Bensen and a Gyrobee. Would that be suitable Chuck? Or would 3" x .065 be the better choice. No holes in it except on the ends of course.

 

[Friendly]

I hope you have this tread still going when I get back from Bastrop Flyin. ,But I have to go. Was suppose to leave this morning.

 

[Wiplash]

That's a brilliant design, highly efficient and optimized - probably the best out there. The only one that gives it a run for its money are Wallis machines. Odd that so few of each design are built and flown by others.

Are there plans available for Chuck's machine?

 

[C. Beaty]

Mark, the Bensen 2 x 2 mast is far stronger than needed but is an excellent roll bar for ground flips if there aren’t a bunch of holes at the seat back.

The Bensen B-7 had a round 2” x 0.065 mast if my memory is correct and its strength in flight was adequate. The cross section area of such a mast is 0.395 in² and if the material was 6061, its tensile strength would be ~16,000 lbs. minus holes.

Almost any mast with sufficient column strength to hold up the rotor on the ground will have sufficient tensile strength in flight.

The worst case in flight is bending strength. With the stick against a stop and with maximum flapping angle, the rotor thrust line could run at an angle of 18º to the mast. If the unsupported length of the mast was 4 feet, the bending moment would be rotor thrust x 4’ x sin 18º.

The moment arm for such a mast is 15”. Rotor thrust of 1,000 lbs. provides a bending moment of 1236 ft-lb. That would stress a 2 x 2 mast to ~27,000 psi, near the bending strength of 6061.

But that’s pretty extreme. I doubt if any gyro has had the stick against the stops with maximum flap angle while pulling 2 Gs on a 500 lb gyro.

 

[jany77]

ultralight

ultralight

b7m were using 2x0.083 but it doesnot make any more difference from 0.065 wall, inertia is almost the same as well as area of the tube ,i think the most important think when design the mast and brackets is where is the last hole placed between yoke bolt and let say seat brace as for example bumble bee has this distance 38" this part must take all the bending and torsional loads ,corect me chuck if im wrong sorry im not enginer

 

[C. Beaty]

My self-imposed rule is never drill a mast at seatback; clamp instead.

That rule originated years ago. I was test flying a young Coast Guardsman’s Bensen when the complete vertical tail came off and went through the rotor. A metal tail built from 3/8 x ½ aluminum bar stock with 0.032 skins riveted on and inadequate bracing.

I was left with no choice but switch off the engine and parachute it down. Landed square but on rebound, flipped over and clamped mast bent but didn’t break.

I related that experience in a SRC newsletter and Bensen picked it up and followed suit.

 

[jany77]

ul

ul

i totaly agree with you that the mast should not be drilled above the seat but in case of all bee gyroplane the seat angle braces are drilled in center of mast that is what i meant

 

[Terry_Smith]

Question: I saw Chucks post saying never drill a mast at seat back, and post#30 mentions the mast should not be drilled above the seat. I'm guessing this is simply for brackets for seatbelts, etc, without additional support like cheekplates? I've seen folding masts above the seat, but since they are supported by additional plating for strength, this wouldn't be a problem? I'm not an engineer, so I don't know all of the stress value calculations. I've read that Aluminum has a shear strength of 30 ksi, but I don't know at what thickness of aluminum they are referring to. This was T6061.

I may want to have a folding mast on a gyro when I get one, so I'm interested in finding out what calculations I would need to know and perform to insure that any change in the mast would be properly supported for safety sake.

 

[Jazzenjohn]

The broken masts I've seen were drilled for seatbelts. Ironically the device to make it safer for the pilot was the very thing that didn't. I've heard some masts were drilled for engine mounts and then they changed something like inverting the engine or stepping the keel and didn't replace the tube with a non-religious tube (i.e. not holy) I don't have alot of experience, but I tend to view folding masts skeptically. The higher the folding point the better, if at all. I can't imaging anyone putting a hole in a mast anywhere near a part of the body they'd want broken. The shoulder harness holes are often the same height as your neck...

 

[C. Beaty]

In a perfect world, the mast would only be drilled at the bottom cluster plates for keel attachment and at the rotorhead cheek plates.

For the stuff in between, use clamps.

Take a look at a Dominator; there are no holes in the mast except at top and bottom.

The greatest bending load on a mast is about in its center, where engine mount rails and seat back attach.

Drill the mast full of holes at the engine mount rails and you’ve got a dotted line for it to break in the event of a rollover.

 

[Aviomania]

Question: I saw Chucks post saying never drill a mast at seat back, and post#30 mentions the mast should not be drilled above the seat. I'm guessing this is simply for brackets for seatbelts, etc, without additional support like cheekplates? I've seen folding masts above the seat, but since they are supported by additional plating for strength, this wouldn't be a problem? I'm not an engineer, so I don't know all of the stress value calculations. I've read that Aluminum has a shear strength of 30 ksi, but I don't know at what thickness of aluminum they are referring to. This was T6061.

I may want to have a folding mast on a gyro when I get one, so I'm interested in finding out what calculations I would need to know and perform to insure that any change in the mast would be properly supported for safety sake.

Terry,

Folding masts are not as strong as one piece undrilled masts. The "cheeckplate" offer some friction lock but is not that much!!!!

If you extend the plate lets say 12"-16" above and below the holes on the mast, use clamps at the top & bottom extreme of the plates and use 0.25" thick material this should make a much stronger folding mast. I have never seen anybody making a folding mast like this but this is how i was going to do it if i needed a quick folding mast...... maybe i will draw up a plan or it.

On our G1sa "Genesis" we incorporated the next best thing WITHOUT compromising ANY strength. The frame does not need the mast to be assembled. You take out 4 bolts from the Base of the mast, remove the control tubes from the stick (another 2 bolts), un-tighten 4 more bolds and just slide the mast with the control tubes out. The frame is still in one piece, can be moved around and the mast is drilled only at the top and bottom.

here are some picks.

Ps. 30 ksi is 30000 lbs per square inch... so you must find the area of the material in inches and multiply by 30000 lbs... that will give you the strength for the material you are using...... but be carful...... is it loaded at shear or tensile?

 

[Passin' Thru]

On our G1sa "Genesis" we incorporated the next best thing WITHOUT compromising ANY strength. The frame does not need the mast to be assembled. You take out 4 bolts from the Base of the mast, remove the control tubes from the stick (another 2 bolts), un-tighten 4 more bolds and just slide the mast with the control tubes out. The frame is still in one piece, can be moved around and the mast is drilled only at the top and bottom.

Ah-Hah! NOW I understand why you designed it with the supplimental 1 X 2 tube behind the mast!
Back when I first saw the frame photos, I pondered why you designed it that way. At the time I could not see its purpose, but knew there must be one. Very clever, Nicolas! Very clever! :yo:
.

 

[Terry_Smith]

Nickolas,

Your solution is very well thought out. If it were possible to do that to the gyro I'm interested in, I'd be SET. But, I've been poring over the pictures of it online, and it isn't designed so that the mast would come out. It's well designed, but not for removal. But, I must say, you've come up with an elegant solution that I'd prefer to do over folding. I'm also looking at cutting out a section of my garage to get a smaller version of the gyro to fit, but I'm not too fond of gutting a garage door, motor, etc, plus having a different door installed to get it in, but sacrifices may have to be made. I might not end up getting the one I want either, if it looks to cost prohibitive to re-model the house for the gyro. Still, I have plenty of time to work that out. Thanks for the pictures - you've done a fantastic job on your gyro!

 

[Aviomania]

Ah-Hah! NOW I understand why you designed it with the supplimental 1 X 2 tube behind the mast!
Back when I first saw the frame photos, I pondered why you designed it that way. At the time I could not see its purpose, but knew there must be one. Very clever, Nicolas! Very clever! :yo:
.

Thanks Terry and Pete.

 

[RotoPlane]

One of the neat things about you Nicolas, is that you do not just follow the crowd design; you plow new ground and grow new and better ideas. And then you share them!

 

[Mike Schallmann]

CB -I guess my gyro is in a perfect world --the ONLY holes in the mast are at the base and at the cheek plates ALL other attachments are clamped -- I designed and built it this way over 12 yrs ago -it has worked perfectly--!!

 

[Passin' Thru]

CB -I guess my gyro is in a perfect world --the ONLY holes in the mast are at the base and at the cheek plates ALL other attachments are clamped -- I designed and built it this way over 12 yrs ago -it has worked perfectly--!!

Yeah, me too! I even changed the mast on my original plans built Bensen way back in the '70's!:yo: