Did I improve this gyro??????

[Aussie_Paul]

The gyro is a 2 seat side by side with a Subaru twin carg fitted with a Rotax "C" box and a 76" w/d prop.

The Rotax gearbox was reversed lowering the thrust line 7.5". I stepped the keel further tp allow prop clearance, and angled the rear keel up towards the h/stab at 4 degrees to help the flat plate stab work a little more efficiently. I also shifted the rear keel 8" further back to give more moment arm to the h/stab.

This created a close proximity of the rear keel to the ground (make a great plough furrow!!!). The owner was not concerned having the pod a bit higher.

I then lifted the front keel up 5". The problem that develops then, for the outback gyro drivers, is that the nosewheel can break off!!! I figured a way to have a spacer and some bars with rod ends from the bottom of the spacer arrangement up to the keel approx 19" behind.

Comments welcome, as I might have stuffed up by not anticipating something. :eek:

Aussie Paul. :)

[Victor Duarte]

paul, i have no skills to tell you whether good ot not, so excuse me asking this, but if you get the occasion, couls you post a closer pic of the nose wheel please ?
i like the design (flexible bar?) and i m curious about the behaviour on a bumpy terrain, looks good ! does it absorb rough bumps?

thank you paul

[Douglas Riley]

Paul: You've made a bad situation better, no doubt about it. The questions are "how much better?" and "is it better ENOUGH?" Can't answer those without knowing the vertical position of the CG compared to prop thrustline -- the usual drill. Do you have those numbers?

If the CG is still below the prop thrustline, I'd be reluctant to count on that HS to compensate. It's rather small and not quite high enough to catch the prop blast.

[mceagle]

G'day Doug and Paul.
I am very familiar with this machine and I would like to point out that the stabilizer in the bottom photo is not the one fitted in the top photo. The area of the stabilizer is 5.2 sq. ft. and it is approx 7.5 ft from the C of G. Even being a flat plate, I am sure you will agree that it would have more power than that fitted to most personal gyros with stabilizers (excluding the SparrowHawk).
As far as the stability is concerned I will have to reserve my judgement until we get it back to Broken Hill and put it through some basic tests. It flew extremely well and docile before the above modifications, probably due to light weight construction below the C of G and and the tall mast, topped off with the weight of big rotors and an electric prerotator.
We have experienced pilots here who are familiar with the way it flew before the engine lift and the keel lift so the results should be interesting.
Unless I am reading it wrong, the above keel lift would not have improved the C of G at all because all you are doing is lifting the whole gyro up. In fact it would have had a detrimental effect on the C of G because of the extra weight below the C of G in extending the suspension. All that was achieved here was giving the rear keel more ground clearance

I would also querie the wisdom of adding 4 degrees angle of attack to the stabilizer without first knowing what angle of attack the horizontal reference flies at. The gyro was originally balanced to tend to fly 2 to 3 degrees nose down and that is why the stabilizer was fitted directly to the keel. Unless the gyro has been re-hung to allow for the new stab angle, then I would now expect it to have some pitch instability (bobbing of the nose) at a certain airspeeds as it hunts for a compromise between the "natural balance" angle and the stabilizer induced angle.

[GyroTyro]

It appears to me, after looking at the photos, that you may also have changed the angle of the prop in relation to the keel. That alone would have a tremendous effect on the thrust of the prop.

[Aussie_Paul]

.....The VCoG to Thrust line offset has come down from 9.5" down to 2.5". The tail was shifted back 8", and the rear keel set at and angle of 4 degrees front down to help the flat plate stab work a little better. If the final tests dictate I will replace the flat plate stab with an upside down rotor blade stab adjusted to fine tune the 2.5" offset.

Tim, we shifted the thrust line down 7.5". The only "stuff that went down with it was the wheels, the rear keel and tail feathers. That is why the change was 7" not the 7.5" that we lowered the thrust line.

Zeeoo I will take a close pic of the nose wheel for you soon. :)

Gyro Tyro, no the engine is still the same as it was when I started. The rear keel angle has altered.

Tim, sorry to muck with yours and Roscos design of many years. The owner will be the best indicator as to whether I have improved it or not. He is inexperienced as you know, and is s**t scared to fly it when the weather is rough. What a waste of a great machine.

I did not want the job, but the owner tried for 12 months to get help, so in a weak moment I said "yes". Now I am glad I did, as I have learnt a lot, mostly how easy it is to get it right!!!!!

The difficult part of course is "knowing that you have to!!!!!!"

After the hundreds of flights I have conducted, testing pitch stability with various configurations, I knew exactly how to make Bill feel happy and safe in that nicely built machine. :D

I prefer the 110 hp Hirth gearbox with the 2.24 to 1 redrive ratio. It allows the use of a 68" prop, and the keel clearance problems don't arise. I realise that there is a small propeller efficiency loss, but that is compensated for by the gearbox not needing to be rebuilt as often as the 75 hp Rotax box and the front keel does not have to be lifted as much.

That is my reasoning for the successful stable machines that I help people build. ;)


Aussie Paul. :)

[Victor Duarte]

Zeeoo I will take a close pic of the nose wheel for you soon. :)
GREAT THANKS paul ! i ll take a pics of the beer i offer you ! ;)
cheers

[mceagle]

.....The owner will be the best indicator as to whether I have improved it or not. He is inexperienced as you know,

Aussie Paul. :)

Paul, I would certainly be interested to hear what the owner has to say.
I am sorry but you are wrong. An inexperienced nervous pilot is not the best judge of degrees of stability. As you yourself are very quick to point out - what on earth would an inexperienced pilot know about stability. It has taken most of us 20 years and we are still learning (I am at least). The quest for better stability has been going on for as long as I can remember, and those willing, will still keep learning. I would certainly take the word of a very experienced pilot over an inexperienced one.

[Aussie_Paul]

...... but he knows when he is uncomfortable. Experienced pilots like you are talking about, Tim, fit that catagory. They never feel uncomfortable due to their skill. Get them to conduct some truly stick fixed testing, and you will see them uncomfortable!!!!!!!!!!

Are you saying that a thrust line to CoM of 9.5" with that rather ineffective stab for the geomtry is suitable for a beginner gyro pilot? In other words is a very pitch unstable gyro suitable for a beginner gyro pilot?

I wouldn't, but I am a novice yet, compared to the Yanks. :o

Aussie Paul. :)

[Chopper Reid]

The nose wheel design is fantastic in a word !! My gyro [built in Broken Hill] has over 3500 hours on it now and despite the roughest punishment thrown at it over all those hours, the nosewheel has not required any attention at all. I mostly have to use padocks for a "strip".
I would like to reinterate what I have said before about the Rosco's and Tim's machines, their design has over 50,000 hours of actual flying experience built into them, these hours are outback working hours, not social Sunday fair weather flying. They fly in all weather conditions, mostly close to the ground where they get buffeted by turbulence created from trees and hills and by whirly winds and thermals. These gyros are easy to fly and fly well. When you hop in a Rosco or Tim's gyro, you are not going to become a "test " pilot !!
Paul, an inexpereinced pilot flying a C172 or 182 in windy conditions would most likely feel very uncomfortable.

[Aussie_Paul]

....that is not the point. I consider them to be longstanding great friends since 1984, when I think we started out together. They make extremely well built gyroplanes, and once again, BUT, they can be made much safer and much more user friendly for beginners starting out with gyroplanes. The aerodynamic, and physics knowledge re gyroplanes has increased around the world during the last few years.

Tim, Rosco and I never knew any better 10 to 15 years ago. I allowed people to build gyroplanes that we now know to be more dangerous than can be built with today’s knowledge!!!!!! :eek: Some of these same people have modified their machines and enjoy their flying a heck of a lot more.

These people Brian, do not sit in their gyros every day for work. They are recreational flyers who might only do 10 or 20 hours per year, maybe less!!! They do not have the skills necessary to be able to enjoy flying unstable gyroplanes in rough air. :(

HTL gyros are not easy for a beginner to fly, and they are at odds with proven aerodynamics and physics regarding safe and stable gyroplanes. Not only that, they use more fuel than a CLT machine.

Brian, the Cessna is stable and helps the nervous newbie, BUT a gyro with the thrust line 9.5" above the Centre of Mass, with a small flat plate h/stab will try to invert in rough air, and if the pilot does not catch it in time it willPPO and invert. That is not as you say "easy to fly"!!!!

As I always say, "I only look at a gyroplane through the eyes of a student almost ready for solo. Is their gyro going to help or hinder the student to become successful?"

The Broken Hill gyros are extremely well built, with the engineering suited to the outback harshness. They are also pitch unstable, and as such, are not suited to recreational student gyro pilots.

In the past quite a lot of gyro pilots came from rural, backgrounds, and mostly had above average mechanical ability and understanding, as well as being quite co-ordinated with machinery.

These days there are more people, that do not have the above advantages, wanting to become involved in gyroplanes. The gap between student types has grown. They are not mostly the rural types now. You guys probably do not see this, but as a CFI, I do see the evolutionary change of the student base. :D

With stable trainers and stable machines to solo them into, they will be successful. That will help the gyro movement grow, and should help with improving our image. ;)

Aussie Paul. :)

[Victor Duarte]

The nose wheel design is fantastic in a word !!
Just well said.

Paul you promised me a photo ! ;)
If i dont get it i will call my friend "kewl kangoo" to bash you :D :D :D
cheers

[mceagle]

Victor, that is one cool Kangeroo.

Paul, I have the greatest respect for your flying ability, firstly for the time you spent training in one of the poorest gyroplane examples of engineering and stability, (AirCommand) and secondly because of the time you spent training in the standard RAF, which in my opinion is one worse than the A/C. It is no doubt a credit to you to have improved the RAF to the stability standards that you say you have. Well done!
However I do get the impression from your posts that you think that you are the only one in Australia that has ever done any stability and handling testing. Just in my area there are at least 3 of us that have been involved with research and development since the early eighties and it is an ongoing procedure. Obviously we are not the only ones. You should read more into the notes of the late Fred Hughes or read some of Birdy's posts more closely. I could go back further and talk of the developments of Gerry Goodwin or Harley Newman and many others during that time. In more up to date times, members like Murray Barker and Max Tout have all been involved in R & D and have contributed something and made their ideas and advice freely available for any gyronaut that wished to learn. I apoligise to the many others I did not mention as I only used these names as starting examples. I will not try to list some of the improvments made because they are too numerous to mention but I figure that if I was doing a considerable amount of R & D, then there was a fair chance that many others have been also.
Some of the R & D carried out in the past in this area (back in the 80's and 90's) included stabilizers, stabilizer size, stabilizer angle of attack, stabilizer volume, (same for rudder), ground stability, in air stability, stability in manouveres, effects of balance, C of G, mass distribution, engine thrust angle (both laterally and vertically), rotor pitch and diameter, additional lifting devices, joystick movement ratios, many different reduction drives, Re-drive ratios, suspension rates, suspension travel, nose wheel steering, tire diameters and widths, brakes, different propeller efficiences, and of course many different engines. I could go on a lot further but this thread is probably getting too boring.
I will repeat though that many others in Australia have been involved in gyroplane R & D and we all owe them a debt of gratitude, even if it served only to avoid someone else from making a similar mistake. There are even some who have paid the ultimate price for carrying out their R & D.
I would not blanket all offset thrustline machines as unstable, especially if you have not flown them. If this was the case then you would have to qualify a large percentage of General Aviation aircraft as "unstable". The reason why they are not considered unstable is because they have built in stability enhancements to compensate. (stabilizer angles, engine thrust lines, stabilizer size and moment arm). Have you ever wondered why the Concord has such a large rudder - think about it.
So too a gyro can be stable with a thrust line offset - it may be just not quite as easy to achieve as it would be with CLT but it can be done.
Incidentally Paul, if you call the stabilizer on the machine in question small (5.2 squ foot x 7.5 ft moment) then what do you call the stabilizer on the Hybrid with the large canopy?

[Victor Duarte]

tim,
Well hung , uhh ? watch out your sheep :D :D

ok just joking, Paul , your front wheel looks really nice, i m not the first to say so, your design could fit a lot of gyros, the one i expect to build soon and others.
let us know how it behaves on rough terrain, on landing.
cheers

[Aussie_Paul]

....Tim, it is aerodynamic and the machine is CLT. Eg. The thrust line is 1" above the CoM with 180 kg of people and 30 litres of fuel.

I agree with almost all of your post Tim. The gyro world owes a lot to yourself, Rosco and all the others you mentioned, mostly for engineering and mechanical R&D.

I have not done anywhere near the R&D that you and others have done. My R&D has been solely focused on pitch stability, and to a lesser extent noise.

I don't believe that just because the machine is HTL that it is unstable, but the question is how much HTL can be fixed with band aids????

Yes you can make a HTL gyro stable (I just wonder why you haven't) with a very large h/stab, and or thrust line tilt but it won't be very stable at full power and zero airspeed.

I think it was Doug Riley who said that you would need an aerodynamic h/stab the size of a barn door to stabilise the Raf 10.5" offset. The machine that I have modified had a 9.5" offset!!!!! and very little in the way of bandaids to help fix the preventable problem.

Dr. Stewart Houston from the Glasgow University told me that the Raf thrust line would have to be angled nose down at 18 degrees to offset the 10.5".

My basic point is that I have conducted stick free and stick fixed testing on these machines, and they are not stable in the aviation meaning of stability. It is that simple. They are great machines mechanically and can be flown by experienced pilots, they are not stable and they are not suited to beginner inexperienced pilots. And I am sure everyone must know by now as I harp on it enough!!!, :eek: that those people are the most likely to die, and more so in a pitch unstable machine.

Bill Drewery is a prime example, as are a couple of guys from Tassie who converted the HTL machines I let them build before I had proven the theory. Now they have converted there machines and love flying them in the "crook" weather, that they were not game to fly in when their machines were HTL.

Tim, please don't make this into a "you and me" or a "them and us" scenario. We all have our areas of where we have more expertise than others, and you have far more areas of expertise than I have, and I am jealous of the level of workmanship that you and Rosco operate at.

As I said above "My R&D has been solely focused on pitch stability, and to a lesser extent noise."
My piloting skills are not that great, but my pitch stability testing is very up to speed.


Aussie Paul. :)

[mceagle]

Paul, I agree there is not much advantage in perpetuating this discussion. I would like to mention before I sign off that a delibrately designed in stability aid is not a "bandaid" solution.

[Chopper Reid]

Paul, I wasnt having a go at you, I was responding to zeeoo's query regarding the Rosco nosewheel of which I have one on my gyro and the fact that it has be trouble free and done its job very very well for around 3500 hours that I have punished it for. I put the rest of the stuff in to qualify my comments .There are a number of people building things for gyros that have very little testing hours built into them.
I did mean exactly what I said when I commented about a low hour pilot feeling nervous on a windy day even in a C172 so its not really surprising when a low hour pilot feels nervous flying a gyro on a windy day regardless if its a CLT gyro or not. From what I have read on this forum, the CLT gyro is regarded as handling better than a non CLT gyro.
Tim and Rosco certainly are big and ugly enough to defend themselves :D and have probably forgotten more than I know about gyro's plus I'm not a instructor or a technical advisor.

[mceagle]

Zeeoo, (Victor) I will see if I can post a picture of the nose wheel that you requested.

[Victor Duarte]

A full bunch of thanks Tim, this one is also to keep. yours ?
cheers

[bones]

Tim do you have brakes all round or just on the nose wheel, how do you find the drum brake ?

[mceagle]

The brake is only on the nose wheel. Weight transfer makes the brake quite effective though a good pilot rarely needs a brake. It will hold the gyro back as well as the dual discs on an AirCommand. As the rpm come up on the AirCommand, some weight comes off the mains and it starts to skid along. The single nose wheel brake also pulls the gyro up straight every time (as long as you do not lock the wheel).
I guess the ultimate would be effective 3 wheel brakes.

[quadrirotor]

This one, Victor, is not bad at all...

[Victor Duarte]

nice work anyway.
just wonder if suitable for really rough landings, i mean like wild fields, wild grass etc
tsss... Paul, i will call my friend "kewl kangoo" :D
thanks andre

[bones]

Yes Tim i very rarely use the brake apart from prerotating, thanks, was thinkin of converting mine to the front wheel as well to have all three, because of what you said about the revs coming up which happens all the time as i have a Wunderlick pre

[Chopper Reid]

Andre, yes, a very clever looking nosewheel BUT, how many hours has this nosewheel had and how many of those nosewheels are there on other gyro's ??
My concern is for guys like myself who have to use rough paddocks as strips and needs a very rugged nosewheel.

[Aussie_Paul]

......This time solo in gusty thermally conditions. It does everything right.

Geeeeez, I am not very good at the motor bike handlebar style of controls!!!!!!!!! :o I keep forgetting to apply power!!!!!!!!!! :eek:

Stick fixed testing coming up during the next couple of days. :D

Aussie Paul. :)

[mrford61]

G,day Paul,

Just curious as to whether that bend in the axle tubing would comprimise the strength of it to any great degree?? The stub axle must stop very close to the bend.

Personal thing, but I like the motorbike set-up. You can maintain full control while shooting (not that I do!) , photoing , picking your nose , scratching your nu......... well you get my drift. :p

[Victor Duarte]

Thanks paul !

[Aussie_Paul]

I had to make the axle tube out steel for that reason Mark.

If a guy had any brains he would not post those pics!!!! BUT I wan't to know where I may not have thought things out correctly. The more eyes the better. :D

Aussie Paul. :)

[birdy]

Ay Mark,I like to have a seperate throttle so my free hand don't wander too much.

[mrford61]

Paul,
ahhh, steel. The undercarriage of my first gyro was all steel, the builder sacrificing a little bit of weight for the extra strength.

I have put this double keel sort of a thing on to get the axle down. The wheels still have a bit of a slant but hopefully it wont matter.

[mrford61]

Birdy,
use the free hand to throw rocks at the "red and whites" when they bail !!

[mceagle]

There in lies the problem Birdy, if you have a separate throttle, you HAVE to use two hands. I am like Mark and find it much easier to fly with a twist grip throttle.
Birdy, how do you think you would go chasing cattle on your scooter, stearing with one hand and with a side throttle?

[birdy]

Thats wot I ment Tim,it stops my left hand from gitn into trouble.
I'v never had any trouble shoot'n left handed....................oops,wot did I just say.