Laheli LA500 Autogyro, Has this been reviewed? - Page 3 - RC Groups
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Jun 04, 2010, 08:30 PM
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Hi
My LA500 came in this week; all I can say is wow!
This is one good looking kit I am very impressed.
Johnny
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Jun 13, 2010, 01:48 PM
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Started building mine yesterday. A few observations:

Page 3. The one way bearing in the pre-rotation gear. The instructions show the writing on the bearing being upper most. This is true after you have turned the gear over to fit it on the rotating mast. But the writing should be down relative to the housing as it is pressed in, not up as it is shown in the diagram. Also the gear sits below the plate on the rotating mast not above as shown on the diagram on the right. And there isn't room for the lock washer and nut (J0424 & J0414) in the recess in J0119 as it is the nut catches on heads of the M3x8 bolts (J0418). In my case rather than look for a thinner nut, I removed the lock washer and used thread lock on the nut supplied.

The rotor head plate J0121 needed the edges sanding slightly to stop it catching on J0119. Otherwise the teeter action is too stiff.

The pinion gear for the pre-rotation motor is a loose fit on the motor and needs to be glued on (it would have been nice if it had been a press fit). This is the same on a friends kit bought at the same time and so isn't just a one-off.

Anyone thinking of using a lower KV motor and swinging a larger prop. There is only room for an 8" prop with the motor mounted in the standard position. I plan to raise my motor 1/2" to allow me to use a 9" prop. but this will mean modifying the servo mount (so I'll make a combined motor and servo mount that uses all 4 mounting holes together rather than just 2 for each).
Jun 13, 2010, 04:51 PM
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JochenK's Avatar
Russell,

I wouldn't raise the motor position, at least not right at the beginning. A motor position too far above the c.g. could mean that the gyro is pushed nose down when you apply power. And teetering head gyros are hard to get out of that condition.

Jochen
Jun 13, 2010, 05:43 PM
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Hi Jochen,

I have considered that. The small propellor and the A123 batteries held quite some distance above the keel both point at attempts to get the CG up and thrust line down. I had ordiginally considered replacing the keel with one with a drop in it in the vicinity of the prop so that I could keep he motor in the same position. But raising the battery higher at the front so as to raise the CG may equally help and would be easier. I've never built a kit yet without modifying it, it's all part of the fun, and if it doesn't work out, well it's only a model, hopefully I'll have learnt something and then build another.

Regards,

Russell
Jun 14, 2010, 07:25 AM
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JochenK's Avatar
Russell,

good to see that you already thought about this problem. I was just trying to preventnyou from doing something rash.

Jochen
Jun 14, 2010, 09:14 AM
Registered User
Hi Jochen,

In normal flight, drag from the rotor should prevent a power push over (PPO). It's only in low, no or negative g situations when drag reduces that I should need to worry. All those hours that Bensens and their derivatives flew before killing their pilots are testament to that. Ultimately, PPO does tend to get them in the end. I suspect that this model even without modifcations would probably do likewise anyway. Raising the thrust line will make it come sooner. But until it's fully built I can't say where the CG is.

Regards,

Russell
Jun 14, 2010, 04:47 PM
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JochenK's Avatar
Russell,

the drag of a teetering head rotor seems to have a peculiar behaviour. Last year I tried to fly a stabless teetering head gyro which, I have to admit, is a bit extreme and only worked for 39 secs before she fell into a turn. Anyway, I made the first hand launch with the set-up I used before on my flights with the teetering head and a horizontal stab at the back.The gyro was simply pushed nose-down into the ground. I then lowered the motor position as much as I could and tried again. Same result, she was still trying to play the ostrich. As I had run out of set-up options, I tried to approach the problem from another angle: I launched the gyro with just a bit more than half power - and that worked, though she would barely fly horizontally. Having no other option, I throttled up cautiously and to my suprise she did not dive down, but started to climb. I was even able to fly a circuit before I lost concentration and the gyro.

With a stab at the back, flying the gyro was not half as difficult and I don't see any big problems in flying the LA500. But it may be useful to remember that a rotor turning at low rpms seems to have considerably less drag than a rotor at full speed.

Jochen
Jun 14, 2010, 05:55 PM
It's all in the Blades!
SafeLandings's Avatar
Jochen, Russell,


The one thing I have noticed with the LA 500 is that the rotor seems quite short (though it could be the video). This would give a higher rotor RPM and may be the trick to helping with the tucking under that was mentioned.
I know that I have experienced it with the teetering head on the RPG, but my blades were spinning slower due to the length.
I am very suprised they have got the teetering head to work at this size but also very very impressed indeed.

Keep the build going Russell and let us know how it goes?


Rich
Jun 15, 2010, 02:27 AM
Registered User
It appears from this thread that nose weight will have to be added to achieve the correct C.G. even using the recommended Li Fe phosphate batteries. I am interested in this factor as I would like to use such a machine for aerial photography. Has anybody any information on this additional nose weight as I would not be adding a "pilot" anyway?
Ted (UK)
Jun 16, 2010, 09:14 AM
It's all in the Blades!
SafeLandings's Avatar
Has anyone started making the head yet? the main shaft on mine seems to be a tad short. I would have liked to have seen at least a couple of threads sticking above the nut...mine is a thread shorter inside the nut I may machine a new shaft up.
Looks like LA have got around the teetering head problem by making it a tight fit and not free teetering, but this may free off once flown?
I have omitted the A123 mounting brackets and making up some brackets for Lipo installation. I can then move the Lipo forwards and backwards and up and down for the best setting.


Its a lot smaller than I thought it would be!

Regards Rich
Jun 17, 2010, 12:25 PM
Registered User
Hi Rich,

See my earlier post. The main shaft nut is a little large and with the lock washer in place it is proud of the main shaft and catches on the heads of the bolts that hold the blade mounting plate and pivot block together (at least it did on mine) I removed the lock washer and used thread lock instead. Also I am pretty sure there shouldn't be any friction in the teetering action. I couldn't tell at first if it was the pivot block that was tight, or the blade mounting plate and tried sanding both sides. In the end I sanded a chamfer on the bottom edge of the blade mounting plate to stop it catching.

Regards,

Russell
Jun 17, 2010, 01:25 PM
Registered User
Tinmar's Avatar

LA 500 Head


Hi,

Rich, could you put a photo of your new bat mount on the site. I am changing my LA`s head to a 3 blade delta head. Should finish the head tomorrow. I will post a photo when finnished.

Martin
Jun 18, 2010, 05:32 AM
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JochenK's Avatar
Rich,

when I started experimenting with teetering heads, I used a head from a German foamy kit, the Slöpter. It was pre-assembled and had noticable friction between the teeter and the fixed part. I didn't think much about this and used the head as it was. My first flights went quite well, but with further use the Micromum with the teetering head got more and more difficult to fly. I took the head apart and removed all friction, but things didn't improve. It took me quite a while and a new airframe to get the teetering head Micromum flying again

I did not make the possible connection between the friction in the teetering head and the flying performance until much later and I'm still not sure there is one, but reading about friction in the LA 500 head made me ask myself if that riction wasn't intended.

I'm not too sure about all this, but I thought I'd mention it.

Jochen
Jun 18, 2010, 06:49 AM
Registered User
flying scrap's Avatar
hi jochen,i think you have a good point there,i have used a teeter
heads on helis but they have a bit of sprung steel rod to dampen it
when the rod broke (and it did often) the heli became a wobbly sod
to fly, the friction maybe doing the same job
pete
Jun 18, 2010, 04:18 PM
Registered User
My 2 cents. The purpose of a teetering head is to teeter and it needs to do so with each revolution of the blades. So those in doubt think about whether or not the head could rock back and forth SEVERAL HUNDRED TIMES A MINUTE with all that friction cos if it doesn't and it sticks the result will be a shed load of vibration passed back to the pivot bearings and the servos as they are forced to move instead.


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