Hornet build update

[CLS447]

Birdy, it's 6AM here, Good Morning mate! What time is it "down under"?

 

[birdy]

Bout 7;45 pm now,then allow 5 mins for me to type this out.
Where's Reading P A.??

 

[Udi]

Crash Worthiness

Crash Worthiness

Some of you may have forgotten that crash worthiness is an important design feature of any aircraft. It goes without saying that crashes should be avoided at all cost, but having an aircraft with good crash worthiness is like having good insurance.

Don - you have said you don't mind that your mast would depart as a result of a blade strike. Would you mind if it takes your head with it? Are you planning on having a shoulder harness on your gyro? How is the harness going to be attached to the gyro?

Aircraft should not only be designed to fly safely – that’s a given. They should also be designed to protect their passengers in the unlikely crash. Unfortunately, in gyroplanes, a blade strike is not very unlikely.

Udi

 

[quadrirotor]

good remark... to be meditated!...

 

[donshoebridge]

Udi,

There are a lot of things in a gyro accident that can kill you. Having the mast wrap around you is only one possibility. But the fact still remains, gyro designers can spend thousends of hours digging throught NTSB reports, and cause of death reports, and short of building a gyro like and A-10, there isn't much that you are going to be able to do to stop the energy stored in a rotor system.

So other than making the mast out of solid A2, what would you suggest as a designed in safety feature?

 

[scottessex]

Let me tell you, I am REALLY GLAD my mast stayed on! I don't think I would have liked the rotor blades departing company with the gyro, or the mast breaking off. A jagged sick of aluminum in the back of the head is no good. After a blade strike the blades are usually damaged and now out of track and out of balance, you do not know which direction they will go. Kind of like breaking the stick off a bottle rocket and hoping it still goes straight.

 

[gyroblackwell]

Ok guys,

Lets put things into perspective here. Don puts a design that he has worked on alot. He shows FEA data that supports his design. Along come the "arm-chair" designers and pick at one little point that is made "off the cuff" without having anything to really back it up, and you are all over it! "BAD DESIGN" "BAD DESIGN" ...... I don't have a problem with constructive critizism.
I do have a problem with empty comments with little to no regard for the person that has the documentation to back the design.

The gyro bee has drilled holes in the mast. It can be a single tube or double tubes. I prefer the double tubes, because the mast support ends at the top of the seat.
Rick Martin did a number on his gyro bee not long ago. We saw pictures of the end result. Was his mast laying on the ground? is his head now missing from his body?

No!

Now if your intent is to scare anyone away from designing a gyro and or destroy further development of the sport, then by all means keep up the good work.

I like to have my design picked on as long as the picker gives me positive information. If you think it is wrong, then give an example of a fix. (not just saying build it like a dominator ron! ) anyone can copy a design. I dare any of you to go out on that limb of "true design" and do better !

clamping everthing to the mast IS a better way of doing things. BUT the parts count goes way up, and the weight goes right along with it. Now if you want to fly an illegal craft without the proper ticket as some here have done, then by all means build it beefy, and stick a huge motor on it!

If you want an ultralight, then you need to comprimise between strength, and weight.

We are trying to do this. I have made a number of changes to my design based on others input. That kind of response is what makes a design safer.

Just my opinion!

 

[scottessex]

That is why it is Experimental aviation. It is truly hard to get everyones opinion to be the same on anything.
I am anxious to see both designs fly! That is the biggest problem strength vs weight.
always a compromise somewhere.
By the way my mast bent right at the top of the motor mount, the keel, right in front of the seat mount.
I wish you both success in your new designs, that is what makes this great. I meant no critisism.

 

[willbow]

Crashworthiness???? How do you measure crashworthiness????

In ANY gyro made today .. the rotor and the tailfeathers are the only control surfaces a gyro has.

In the event that any of those components catastrophicly fail, especially at altitude - you are essentially a stone!!!!

How crashworthy is your gyro?

I can understand Scott's mast bending just above the motor mounts (btw - am very glad you were able to walk away from that one Scott)

Not to pick on the Bee, but it's mast is unsupported beyond the diagonal braces and engine mount and constitutes a 3 foot or so long lever. On the hornet, this same span area is less than 5".

It would take a tremeandous amt of force to make that 5" section of mast fold and even more force to exceed the tensile strength of the diagonals.

Sounds crashworthy to me

 

[Udi]

Don,

I apologize if my previous post came through as negative criticism.

Actually, I was impressed by your stress analysis. I think you are doing a very thorough job. I was alarmed, however, when you said:

A mast is not designed for blade strikes. Masts are designed to carry a useful load into the air

And

A blade strike is bad no matter how strong or weak the mast, and it if breaks off and leaves the general area, good!

As a potential customer, I want to know that the designer gave some thought to accidents. Doug Reiley, in another thread, wrote a convincing explanation why certain holes in the mast are not going to weaken the mast significantly in the event of a blade strike.

Saying that a gyro cannot be made strong enough to protect me in the event of a rollover or a blade strike does not make me feel warm and fuzzy about your design.

I hope this is taken as constructive criticism.

Will – when a Cessna 172 loses a wing in flight it would crash and burn. Is that a good reason not to make it crash worthy? You are an extremist, my friend. Making a gyro more crash worthy means that you pay attention to the consequences of small accidents like a rollover, a blade strike, a drop from 10 ft, etc. No aircraft is survivable from a catastrophic failure in altitude.

Udi

 

[willbow]

Sorry Udi .. didnt mean to come across as an extremeist .. it's just that no mast will survive a blade strike very well and I think what Don meant was that if the rotor does break off, better it fly away from you than turn you into deli meat.

Anyway, what would you like to see changed?

 

[Udi]

I don't want anything changed, Will. I have no issues with Don's design.

Udi-

 

[donshoebridge]

I was wondering when Doug's name was going to come up.

I've seen the thread/post that you are refering to Udi.

First of all, the mast is ridiculously over-strong for the flight loads it encounters.

Later in the same post he stated the following...

With respect to withstanding blade strikes, the mast is essentially a cantilever beam stood on end. Cantilever beams by their nature are not very strong for their weight, and that holds true for gyro masts. Bending loads that will break a 2x2 (or double 1x2) mast fall between 300 and around 650 lb. Not that much in the best of cases!

I fully agree with the numbers stated above - 300-650 lbs. But when taken in context with the earlier statement, some very important facts and questions come to mind;

1) With 500 lbs of lift and 100 lbs of drag, that sure puts the mast real close to the 300 pounds in my book. I wonder if the 100 lbs of drag is an average? I wonder where it peaks at with 2-per-rev? What happens to the drag component when you start pulling some G's?

2) Assuming rotor blades weight 60-70 pounds, with them near flight speed, say around 250 RPM, and a diameter of around 23 feet, how much energy do you think is going to be applied to the top of the mast if a blade were to hit the ground? Now I haven't figured it (because I'm lazy), but I'll bet a HELL of a lot more than just 300-650 pounds! Depending on where the blade is in its rotation (advancing, retreating, crossing left or right) the forces applied to the mast will decide which way the mast will likely bend/break. In all roll over cases, how many gyros have had the retreating blade strike the ground first?

 

[Dean_Dolph]

Don, some comments and observations from a non-engineer, unless the shade tree degree counts!

First of all, in my opinion, it is ludicrous to even worry about crash worthiness of an open frame machine. I'm perfectly satisfied with one that is designed to not have any in flight failures of frame and components. If a pilot has crash worthiness at the top of his gyro criteria list then the Little Wing or similar machine offers the best option.

And secondly, because, or in spite of, all the number crunching & analysis, empirical data/experience (Close to 50 years worth!) should convince us beyond reasonable doubt that there is very little problem with the mast, even with ground strikes. However, the supporting structure(s) have been a problem from time to time. The masts that got the most attention were on Fetter's original Air Command design. And even then there was/are two camps.

One wants the mast/rotor to depart and the other wants it to stay intact. The first camp believes there is less chance of injury if the mast/rotor leave the immediate area while the second believes there is less chance if the mast/rotor remain intact and somewhat limited on where it can go. In either case we can't predict what will happen in a blade strike although we might be able to suggest that the majority of the time it will........

I have witnessed a couple of ground strike incidents and it seems that the only similarity was that the machines all rolled to the left so maybe something can be made out of that.

I say again, give me a stable machine that will not fail in flight and access to the proper training and I think my odds of surving are as good as driving the Houston freeways.

 

[birdy]

I'v said before ,if you want to crash test an aircraft,make it a gyro.It's the safest machine to crash.
For an outsider this may be hard to accept[heavy rotors spin'n,prop,no protection]but I had a bit of practice at crash'n.
Left and right.
The time I fell left,with loaded blades["J" stick broke] the armchair desigener would say I would git me head ripped off coz the retreating blade striking the ground would force the mast forward.It did,but only bent it bout 15 degrees,the blades were written off[one broke off 18" in from the tip].
This mast isn't supported anywere above the top seat mount,and that's only a clamp.

I personaly can't see how anyone should git hurt if they are still alive when they get to the ground,no matter if you land on your wheels or your door.If you land on your roof,your already dead ,so this thread don't concern you.
Providing you fly it as a gyro,not a cessna.

 

[bones]

Scott,
Please explain why you ended up denting your bird that bad when you landed there, seems to be lots of open space..

 

[scottessex]

Basically I blew a head gasket on takeoff, I was unable to gain airspeed or altitude to turn back to the runway, I couldn't get over the powerlines either. So I put 'er down, hard, and bent the right axle. Everything seemed good, untill the weight started coming off the blades and settling on the airframe, the axle broke, and I had a roll-over. The full story and pics are in the general discusion section, under bad news from georgia.

 

[donshoebridge]

It's starting to sound like we're all preaching to the choir. For the most part, we're all in agreement.

The reason tempers flared in the first place was because there are a few people that are actually trying to design a gyro without stealing too much from other gyro designs, such as myself, and Tim Blackwell. Call it honor and integrity if you want. Both of us having been design engineers for many years figured (like many engineers) that we could do it either ourselves and/or better than previous engineers. This may or may not be true. Only getting off the ground will tell.

I have confidence in my design, as do others, and I will fly my Hornet when completed. Everyone here has what I call the "self preservation gene". Those that don't, usually crash trying to self train in a hurry, or put their aircraft together with wood screws.

But any ways... I think this topic/thread has about had it. Let's leave on a middle-note.

 

[bones]

Ouch sorry Scott, that would make ya just a tad cranky

 

[scottessex]

Yeah Bones it sucked!
The new rebuild thread is under the Bensen KB section.

And Don, I love your suspension set up! And all of the kids in my neighborhood better not leave thier bikes outside at night, or my gyro may have a new front wheel!