Smallest lightest possible gyro..?

heyheyjc

Junior Member
Joined
Jan 27, 2007
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Ventura, CA
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My searches here haven't yielded anything much on this topic beyond the minimum engine power (40hp seems to be at least one consensus view), but little discussion about exploring the lower limits for the whole aircraft. Some back of the envelope calcs, Gyrocalc et al, make me think that fairly normal ultralight performance could be achieved down at roughly 175lb empty.

I happily admit this sounds ludicrous (and entirely ignores crashworthiness), but looking at a downsized Chuck-Beattie-style three tube floorplan out of composites, HMD panel, an Aixro 35hp engine, fast 18.5' blades, that's what I'm getting... I'm only 165lb myself, which helps.

Has anyone given this thought experiment much... thought? Where does the concept go horribly wrong?
 
I like this topic !
Okay, just to kick out some discussion topics, usually "lighter" means more "expensive".
Lighter also often means lower Safety Factor or 'less strong' (how strong is 'strong enough'?).
Usually, lighter engines mean less power and less power lifts less weight and goes slower.
Brian
 
Smack;n1122922 said:
I like this topic !
Okay, just to kick out some discussion topics, usually "lighter" means more "expensive".
Lighter also often means lower Safety Factor or 'less strong' (how strong is 'strong enough'?).
Usually, lighter engines mean less power and less power lifts less weight and goes slower.
Brian

- More expensive? No argument from me on that. None at all.
- Less strong, perhaps, but also lighter... so what are the features that really constitute crashworthiness for an open gyro? What are the accidents that are survivable in a Dominator, but not in an ultralight (and perhaps even less so in a 'nano')?
- On the power to weight ratio, 35hp in a 370lb AUW nano (10.5lb/hp) is the same as 42.5hp in a 447lb regular ultralight. Cruise is limited to 55kts either way, so we're mostly talking about climb rate and acceleration anyway.

I think why I'm interested is the idea that in the same way adding a lb of weight to an aircraft requires more power, rotor, structure, and therefore even more weight, subtracting a lb of weight means less power, rotor, structure... and therefore even less weight. Fuel and pilot are fixed 'costs' so there is a limit, but I wonder if existing ultralights are at that limit yet? Looking at modern motorbikes, bicycles (particularly) and race cars, I suspect not...?
 
If legal ultralight performance is the standard then what is the benefit of a 370 AUW UL v.s. a 447 AUW UL?

Other than for the pure challenge of producing such a machine there seems no reason to justify the higher cost.
 
Alan_Cheatham;n1122937 said:
If legal ultralight performance is the standard then what is the benefit of a 370 AUW UL v.s. a 447 AUW UL?

Other than for the pure challenge of producing such a machine there seems no reason to justify the higher cost.

Fair point.
I guess the big ones would be increased range and time in the air / reserve from the less thirsty engine (perhaps > 35% better than a Rotax 447).
Potentially increased maneuverability etc.
Easier storage and transportation...? I'm stretching here.
 
All good points, somehow Ken Brock got a 582 with prerotater and brakes to come in under 254. Now I know it was not a great design, but I think if you change the 582 with a 503 then you could add a tall tail and still make weight and have good performance. Just a thought
 
heyheyjc;n1122947 said:
I guess the big ones would be increased range and time in the air / reserve from the less thirsty engine (perhaps > 35% better than a Rotax 447).

I don't think anyone's been successful flying that engine so far. It looked appealing, and was de-rated slightly from the go-cart specs in aviation use, but if I recall it used plastic bearing cages which failed quickly in continuous high-output use. I've seen reference to magnesium cages being available for rebuilding, but not from reliable sources.

Expecting 35% better fuel economy compared to a 447 is also dubious. The wankels are notoriously thirsty.

The ultralight world has been waiting for a small,light, high-RPM four-stroke which will work with a reduction drive to turn a prop safely and durably at about 40 HP. Unfortunately, the wait continues.
 
PW_Plack;n1122980 said:


I don't think anyone's been successful flying that engine so far. It looked appealing, and was de-rated slightly from the go-cart specs in aviation use, but if I recall it used plastic bearing cages which failed quickly in continuous high-output use. I've seen reference to magnesium cages being available for rebuilding, but not from reliable sources.

Expecting 35% better fuel economy compared to a 447 is also dubious. The wankels are notoriously thirsty.

The ultralight world has been waiting for a small,light, high-RPM four-stroke which will work with a reduction drive to turn a prop safely and durably at about 40 HP. Unfortunately, the wait continues.

Good to know, if a bit depressing.
 
PW_Plack;n1122980 said:


I don't think anyone's been successful flying that engine so far. It looked appealing, and was de-rated slightly from the go-cart specs in aviation use, but if I recall it used plastic bearing cages which failed quickly in continuous high-output use. I've seen reference to magnesium cages being available for rebuilding, but not from reliable sources.

Expecting 35% better fuel economy compared to a 447 is also dubious. The wankels are notoriously thirsty.

The ultralight world has been waiting for a small,light, high-RPM four-stroke which will work with a reduction drive to turn a prop safely and durably at about 40 HP. Unfortunately, the wait continues.

Bit more research on this:
Better bearings are specifically mentioned in their one-sheets for their three aviation models, so at least the plastic cages issue is no more.
Looks like several paramotors and fixed-wings are using them, though of course how successfully long-term is almost impossible to determine.
Incidentally 5 - 7 liters (1.3 - 1.8 US gallons) / hour is quoted everywhere, though again how that translates to the real world is an open question.
I've seen references to up to 3x reduction.

What this adds up to, I don't know. Enough diagnosis, research, and incremental development can eventually lead to a reliable engine, but whether this has happened to Aixro yet... People will certainly keep trying, those specs are just too appealing.
 

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heyheyjc;n1122995 said:
Incidentally 5 - 7 liters (1.3 - 1.8 US gallons) / hour is quoted everywhere, though again how that translates to the real world is an open question.

The very best fuel-injected, four-stroke piston engines in this application burn about .39 pounds of gasoline per horsepower/hour. If the Aixro could manage .4, which is highly unlikely, 1.8 GPH would be about 27 horsepower. My suspicion is those fuel economy quotes are in applications involving full power for takeoff only, then dialing things way back for slow cruise.

But if they've solved the bearing issues, that's progress!
 
Leaving aside the engine question for now... two more questions:

- what does crashworthiness mean for an autogyro?
- what are the negative characteristics, if any, of shorter rotor blades? (assuming reasonable blade-loading, disc loading, tip-speeds etc as per C.Beattie's spreadsheet...)
 
And... back to the Aixro engine then. Heard something back from their dealer in the UK:

"Good Afternoon Jake,
It’s a little hard to hear this, as it sounds like someone is bad mouthing us. There are no plastic cages in the motors, this would be crazy...
I'm sorry I can not offer any customers details for you, but I can say, as an example, we have had a MOD contract for the past 10 years with these motors, and to my knowledge, it has no reason to be stopping...
I hope this puts your mind at rest..."

[FYI, MOD is Ministry of Defense, the UK's DOD - I'm guessing drones, unless someone has any other ideas?]
 
I have a friend of mine that has had 3 of them on his powered parachute. 2 died and 1 was stolen. He had great difficulty replacing the stolen one and now that it has blown up, I don't think he wants another one. I haven't talked to him lately, but I think he switched to a Polini Thor 250.
 
heyheyjc;n1123090 said:
It’s a little hard to hear this, as it sounds like someone is bad mouthing us. There are no plastic cages in the motors, this would be crazy..

For the record, I have no reason to "bad-mouth" Aixro. Perhaps the early users whose comments I read were mistaken. If so, sorry for the bad info. I'd love to see an engine like this work out.
 
PW_Plack;n1123147 said:


For the record, I have no reason to "bad-mouth" Aixro. Perhaps the early users whose comments I read were mistaken. If so, sorry for the bad info. I'd love to see an engine like this work out.

I certainly didn't read your post that way. I also don't see any reason for anyone at a dealership to know much about earlier issues, but equally they have much incentive to 'forget' about them if they did. Without certification and statistics and TBO's etc, so much of the information we can actually access about newer or non-mainstream engines is hearsay, or outdated, or speculation, or hype, or estimation... or absolutely spot on. Hard to tell which, the sample-sizes are just too small, we probably don't hear about most of the failures, nor most of the successes.

Many engines look good (that Thor 250 looks great)... and hardly any seem to work out. I can't help wondering if improved batteries (where all the big r+d money is) might push the ultralight market electrical before the ideal IC engine appears.
 
The airplane brand I cannot remember had one of these Aixro rotaries mounted on it. I believe Ron Awad flew it with the Aixro.

The owner of that airplane business wrote up his travails in dealing w/ Aixro (whether it was the Florida distributor or the factory in Germany, I do not know) because it seized.

He reported the bearing cage was indeed made of plastic. He had said the plastic was distorted and that the bearings were ruined, as he opened it up to determine the cause.

He said he was not compensated for the damaged engine that had only about 30 hrs. on the clock.

Shortly after I saw his posting, it was taken down.

​​​​​​​I am not against Aixro, nor rotary engines. I actually own a new Aixro that I had in mind to use for an ultralight gyro, since it weighs so much less than other light engines.
 
No one mentioned the Taggart Gryo-Bee. It takes a 40hp engine simple to build, and you can get all your parts from Star-Bee gyros. ( if you need the "original Taggart Plans" that used to be a free down load I have them saved. I also have a lot of the drawings in CAD..just email me)
 
Hi,
I've just joined and being disabled im no longer able to ride my Bike any more due to its just being so heavy, it puts a lot of stress on all of my metal work.
Could you possibly email me a copy of your plans as I want to build and fly one of these fantastic machines.
Just ONE question that I do have though, instead of useing a Rotax engine which in the u.k are expensive, would it be possible to fit a motorbike engine?, they are small light and relatively speaking something like my goldwing gl1000 engine or the BMW 850 engine being shaft drive and very reliable would do the job nicely I should have thought?.
Anyway, I don't have any autocad programs and to be honest I wouldent have a clue how to use the program, i know how to use vernier, micrometer and read technical drawings so would be grateful for the drawing in PDF format.
All the best.
Vic
 
Hi,
I've just joined and being disabled im no longer able to ride my Bike any more due to its just being so heavy, it puts a lot of stress on all of my metal work.
Could you possibly email me a copy of your plans as I want to build and fly one of these fantastic machines.
Just ONE question that I do have though, instead of useing a Rota engine which in the u.k are expensive, would it be possible to fit a motorbike engine?, they are small light and relatively speaking something like my goldwing gl1000 engine or the BMW 850 engine being shaft drive and very reliable would do the job nicely I should have thought?.
Anyway, I don't have any autocrat programs and to be honest I wouldent have a clue howtouse the program, i know how to use vernier, micrometer and read technical drawings so would be grateful for the drawing in off format.
All the best.
Vic
PDF FORMAT sorry
 
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