Arrow-copter. This is my dream-gyro

This thread is DEAD ! Thanks for the lack of input !
 
Yes, I think that we can trace the death of this forum to the change in format. Turns out that was quite the mistake. I appreciate those that run the mechanics of the forum, but there is zero doubt that the traffic on this site has absolutely cratered.....
Brian
 
NoWingsAttached;n1118357 said:
I have a thing about T tails. I built a wind tunnel to test all of the different tail designs for a pusher gyro back in 2008 thinking that a V tail would be great. I was right, although Ernie's cruciform tail is the best, the V tail is a close second, and the original Bensen design with the HS ahead of the VS is unbelievably stable! And I discovered the T tail stinks - it is by far the worst design of all, which tells me that anyone whoever designed a gyro with one did absolutely zero testing of models in a wind tunnel, quite obviously. And if they didn't bother to test aerodynamics of their design, what the hell are they doing designing and selling anything that flies and that my life depends on....

Apart from hear-say, what is your source of information?

A model of the ArrowCopter was tested in a wind tunnel. There were also extensive fluid dynamics simulations run on it. And it underwent a very stringent flight testing regime. And then I've been flying it for some 500 hours. And, believe me, stability testing was first and foremost on my mind.

The upshot: it is VERY stable with no adverse characteristics determinable -- it would not have otherwise passed certification. It was the first gyro to be certified in Austria and the authorities were all over it. Inside and out. They rode the rear seat during some of the crucial test flights.

The point is that you can't make a sweeping statement like this. I really wish you wouldn't just blabber on without knowing your stuff.

Greetings, -- Chris.
 
ckurz7000;n1122926 said:
Apart from hear-say, what is your source of information?

A model of the ArrowCopter was tested in a wind tunnel. There were also extensive fluid dynamics simulations run on it. And it underwent a very stringent flight testing regime. And then I've been flying it for some 500 hours. And, believe me, stability testing was first and foremost on my mind.

The upshot: it is VERY stable with no adverse characteristics determinable -- it would not have otherwise passed certification. It was the first gyro to be certified in Austria and the authorities were all over it. Inside and out. They rode the rear seat during some of the crucial test flights.

The point is that you can't make a sweeping statement like this. I really wish you wouldn't just blabber on without knowing your stuff.

Greetings, -- Chris.

Good to see I can still get a rise out of folks on RF, this place has turned into a ghost town and some lively conversation helps breath some life into the void.

My source of information is my home-built wind tunnel and my own observations, as mentioned in my post. Not sure how you could have missed that.

I will bet dollars to donuts that if the wind tunnel testing was done on the Arrow copter that it was undertaken in straight-line air, not rotational to properly model prop wash on the T tail in order to test the empennage for adverse yaw under power. It is very difficult to simulate well, unless that is specifically what you are designing the wind tunnel conditions for, as did I.

A whole bunch of gyros have T tails, and a whole slew of their owners love them - as you love the ArrowCopter. That's nice, but it doesn't make the T tail any better than being the worst design ever imagined for a pusher gyro. You are not wrong to love them, but the designers are mistaken if they think this is the best design for a tail and anyone who claims they are any better than the worst thing on the back of a gyro is mistaken. You folks can always learn how to fly it and deal with the adverse yaw - most especially when correcting for a bad landing while crabbing in a stiff cross wind. One good method is to land into the wind with zero roll. Another is to be sure the wind is on the opposite side of the tail as is the prop wash. If you get caught in a changing wind with your pants down, well, good luck friend.

Keep your spinny side up and your rubber side down.
 
Smack;n1122920 said:
Yes, I think that we can trace the death of this forum to the change in format. Turns out that was quite the mistake. I appreciate those that run the mechanics of the forum, but there is zero doubt that the traffic on this site has absolutely cratered.....
Brian

I have no problem with the new format........works fine !
 

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NoWingsAttached;n1123070 said:
A whole bunch of gyros have T tails, and a whole slew of their owners love them - as you love the ArrowCopter. That's nice, but it doesn't make the T tail any better than being the worst design ever imagined for a pusher gyro. You are not wrong to love them, but the designers are mistaken if they think this is the best design for a tail and anyone who claims they are any better than the worst thing on the back of a gyro is mistaken. You folks can always learn how to fly it and deal with the adverse yaw - most especially when correcting for a bad landing while crabbing in a stiff cross wind. One good method is to land into the wind with zero roll. Another is to be sure the wind is on the opposite side of the tail as is the prop wash. If you get caught in a changing wind with your pants down, well, good luck friend.

Keep your spinny side up and your rubber side down.

I don't want to step on anyone's feelings or ego so I apologize beforehand. I don't mnow your homegrown wind tunnel and the kind of instrumentation you have to measure forces, torques, position, flow etc. I also don't know whether you've done any fluid dynamics simulations on real gyros to identify weak areas in stability. And lastly I don't know how many hours you have flight testedthe ArrowCopter. But I do know what I have done in this area. And I do know that I habe observed none of what you are writing. So I can either throw out hundreds of hours of my own experience and knowledge as well as those of the team designing the ArrowCopter or be a bit sceptic about your claims.

I coose the former.

-- Chris.
 
Chris
Is the Arrowcopter still in production? I've heard lots of rumours that aren't worth mentioning here.

I balanced one recently in Germany, quite interesting.

Mike G
 
Hi Mike,

yes, the ArrowCopter is in production again after a hiatus. As far as I know the lead time is 6 months at the moment.

Can you tell me more about balancing thenArrowCopter?

Greetings, -- Chris.
 
Chris
OK I'll send you a pm.

I'm told it was discussed on the German forum but I could never get to read anything when I tried to get on it, I wouldn't have understood much anyway, it's all in German
Mike G
 
Mike G;n1123912 said:
Chris
OK I'll send you a pm.

I'm told it was discussed on the German forum but I could never get to read anything when I tried to get on it, I wouldn't have understood much anyway, it's all in German
Mike G


Yes, here is the discussion...

​​​​​​http://www.gyrocopter-forum.de/board...ten/#post20571

Apparently, and in this case, the vibrations in that ArrowCopter couldn't be eliminated. Things went better for a 'Calidus' that was also 'treated' by Mike, this time with success. From being a 'French unit' it was transformed into a 'German gyro'...

The whole thread is interesting and instructive. One of the posts mentions the subjective side of the problem, as some people may have a higher personal sensitivity to vibration, or perhaps they hold the stick more tightly... Who knows... It's clear that the matter is very complicated, that the 'stick shake' has many sources, and that they are not always in the rotor, or exclusively in the rotor...

My own ELA shakes wildly (at least I feel it that way...) but not always with the same intensity. It has 'good days' and 'bad days'... The last thing I've discovered is that the shake gets stronger when I push any of the rudder pedals. Hence, the vibration is probably originated there, and not in the rotor, at least in part... Who knows...
 
Xavier
Thank you for the link. A friend, who understands German, told me about it and when he tried to show me couldn't find the thread. I tried to get on to their forum but it keeps telling me (in English) I haven't finished registering but the instructions are in German!!!.
Nice to see the photos, that's me up the ladder. Helmut and Norbert were very welcoming, Helmut's trailer for the Arrowcopter is unbelievable.
The most frustrating thing was that they are just inside the German border so having driven through France and Belgium with their speed limits, I only had a few kilometers on the autobahn at 180 k/h. I will run the thread through Google translator to see what they say.
​​​​​​
I know I sound like a dripping tap (faucet) but get a frequency analyser on your gyro it's the simplest way to reduce the number of potential causes. It's a real pity you're not nearer I'm sure a decent analysis would help.
Mike G
 
A rotor like Arrowcopter produces strong 2/rev vibrations, due to high load and high forward speed. In tip plane as well as axially.
Unfortunately, even perfect balancing can not do anything against 2/rev vibrations.
 
JC
You are (as usual) right to say that the 2/rev vibration cannot be reduced by balancing (or tracking come to that), I've said it so often here that people have stopped listening, but the 2/rev vibration measured at the top of the mast (so due to the rotor) on the Arrowcopter I measured recently in Germany was reasonable compared to other well known gyros. It comes out on the lower end of the typical Eurogyro rotor 2/rev vibration. To be fair to the others, there wasn't a suitable accelerometer fixing point on the rotor head so we were measuring on the mast rather than next to the bearing.

I think that the very strong/rigid carbon fiber monocoque cockpit/mast tends to transmit more vibration into the cockpit than on some others (not all) but I always say if I'm going to crash I want to be in an Arrowcopter, it's built like a formula 1 racing car.

How do you like my new Avatar? When balancing rotors I often feel like Don Quichotte trying to fight windmills.

Mike
 
Mike,
To check my spreadsheet, do you measure the vertical vibration on the mast of the Arrowcopter with the corresponding environment: Mass in flight, rpm, forward speed? Thank you
 
JC
I gave up measuring vertical vibration at the mast when I realised it tends to follow the Y axis (avant/arrière) very closely, so for balancing I didn't need that third axis. I do measure vertical and horizontal axis in the cockpit now as standard if I can find somewhere to fit the second accelerometer. Vertical in the cockpit (the most disturbing for the pilot I think) tends to follow the Y axis at the mast but at a reduced level.

Mike
 
Did I understand you correctly, Mike ? You put both accelerometers in the cockpit, pointing left/right and up/down and none on the mast?

-- Chris.

P.S.: I love your Don Quixote allusion :)
 
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Mike,
Mu of Arrowcopter is higher that much others. Vertical force vibration 2/rev transmitted on the mast tip increases.
 
Chris
the PB4 has two connections for accelerometers. The Smart Avionics accelerometer probes are dual, there are two accelerometers in each probe at 90° to each other. So when balancing I capture 4 accelerometers at the same time. At the mast I have one probe with one accelerometer pointing left/right (X) and one fore/aft (Y). In the cockpit I have the other probe with one accelerometer horizontal left/right (the same direction as X) called X2 and the other pointing vertical called Y2.

The PB4 gives you a polar chart and you can select which pair of accelerometers you want to look at at any one time. In theory you can end up juggling 2 charts with 12 move lines (6 on each) at the same time but the technique I use simplifies things a bit (but not always). PB4 training now available:smile:

JC what makes the Arrowcopter have a higher mu? I thought it had a standard Averso rotor diameter so even if it flies a bit faster the rotor is probably at a higher rpm due to the weight.

Mike
 
Jean - Claude;n1124896 said:
Mike,
Mu of Arrowcopter is higher that much others. Vertical force vibration 2/rev transmitted on the mast tip increases.

Solo I cruise at around 175 km/h at a rrpm of about 360. Two up it is more like 160 km/h and 400 rrpm. If I didn't mistype on my calculator, that's a mu between 0.25-0.3 depending on the condition.

-- Chris.
 
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Mike
It seems to me diameter is 8.6 meters and chord 0.25 meters. Also, the wing reduces a bit the rotor load, and slows down rpm.
Then the better streamline allows a higher forward speed.
So, solo, Chris shows mu = 0.3
 
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