Crane Fly Trainer Autogyro

Hi Steve

Your avatar suggests you might know a thing or two about these alternatives to fixed wings.Have you had much success to date ?

The mg90 servos are IMO as bomb proof as it gets at that price level,we have never managed to break one.or had any fail.

Your build has beaten the thread ,We look forward to seeing your photos .Thanks for posting.

 

Tom.

Hello again Tom. My post on page 12 covers my success todate, I have had great fun building and flying twin rotor gyros IMO this is the best way for beginers to get hooked on the fun of true rotory wing machines .Helicopters are rotory screw machines. Being of the older school (before artf ) building is 50% of the fun of the hobby.My success with single rotor machines seems to be the higher I can throw them the longer they fly.

Cheers Steve

Well, she would have been sitting on her wheels tonight if I was paying more attention earlier when bending the piano wire. Another trip to the model shop required.

 

Are the blades 18" long ?? Looked through the threads a few times, but I can't see a mention of the exact measurement (or is just a 36" length cut in two to make the pairs of blades in the earlier pictures).

 

Cheers,

 

Simon

Sorry Steve I have so many messages that my old brain is getting unreliable lol.

Hope you find the Crane Fly does the job .

My observations at the field suggest that most failed attempts can easily be explained I have made the list below in case its any help to builders.

 

My take on common reasons for failed attempts

 

Unsuitable weather conditions for maiden flights.

 

Model to advanced for pilot eg to fast and sensitive .

 

Over controlling an out of trim model.

 

Insufficient rotor speed at point of launch or attempted ROG.

 

Model out of trim beyond available remaining stick movement.

 

Insufficient application or over application of power.

 

Failure to use back rotor during rotor turns.

 

Failure to reduce power to cruise setting once airborne

 

Attempting rog from unsuitable ground.

 

Unfamiliar assistants hand launching

 

And the one that can even spoil the flight if the model

is trimmed and flying ok DISORIENTATION. this may help to make it easier..... fly a circuit direction that's most comfortable ,keep close in without needing steep turns ,allow for down wind drift ,and don't be distracted by other people talking to you (unless of course its an instructor). Apply bright areas of fluorescent trim.And fly short sorties.

 

 

 

 

 

Hi Simon

 

Your observation re the tail tip dihedral is correct the measurement should have read 3.75" not 4.75" thanks for spotting that.Your lower setting should be ok though.

Each rotor is 18" long.

I guess you need good four channel stick coordination to fly the helicopter? if that's the case fitting a rudder should be fine ,but in the early stages of getting to grips with autogyros a low work load and minimum distraction can be a big advantage.

 

I see you have fitted 4mm nylon bolts to the mast base and stay anchors .

shame about the piano wire was it that brittle Chinese stuff ? you cant beat the genuine"John Bull", swg ,is the clue ,if you can find it !

 

All my blade sections are sanded and shaped by eye balling ,sanding to the 6-7 mm max thickness at 30 percent chord leaves little work to get a flowing upper profile ,watch out at the t/e its thin enough as it comes .

 

We look forward to more photos and the results of the maiden .

 

Good Luck

 

Tom.

 

 

 

This the section I will be using for the test flight ,I recon a touch thinner might be a little more efficient .

 

Simon,

If I were you I would fit the rudder as you are at a stage where you can, you can always leave it unplugged for the time being?

 

Tom,

Try something in the region of 4 grammes as tip weights and see how things go?

 

Stephen,

 

The LA 500 is a super flier, very forgiving but you need to keep the throws minimal. Try not to worry too much about turning the pre rotator off until you are up in the air.

The negative with the 500 is the head, I rolled mine once on the ground and that head just exploded. Its hard to get hold of parts cheaply!

 

 

Rich

Couldn't resist a quick mock up.

 

Hello Tom and fellow gyronuts

Fettled the Cranefly today shaved the AUW down to 21.75oz and increased hang angle to 15 degrees.I took a couple of photos and then had to work out how to post them as I am new to these forum things but I think it has worked.

You may notice that I have raked the wheels forward and put the battery in the box.I think it is easy to build this model tail heavy if you are not careful.

Have fun Stephen

Hi Everyone.

 

My Crane fly Maiden.

 

Well the weather turned out to be perfect this afternoon ,Richard ,Fred ,Pete and me all had new autogyros to maiden .Mine was of course was the Crane Fly , built as my thread describes

.

The wind was 2-5mph NW allowing us to fly down sun so as there was a lot to get through the lads voted to get the Crane Fly maiden out of the way first , After checking the model out a low power taxi run was tried to establish good rotor run up and reasonably straight ground tracking,that seemed ok so a faster run was tried lowering the rotor angle with the stick to keep the model on the ground ,no problem there .

 

The main thing was to be sure the rotors were up to speed ,otherwise attempting to take off would result in a roll over to the left and crash.

 

A good final check around the model and this time a gentle acceleration into the light wind lowering the rotors as they came up to speed, then adding more power, letting the acceleration increase for a second and then easing in some back rotor gave a nice clean lift off.

 

Found I was holding in some forward stick so the rotor required trimming forward ,no problem though did some ultra slow passes for Pete's camera ,(unfortunately our cam ace Stuart was not available) then climbed high for an auto-rotation landing .

 

TBO the model was ridiculously easy to fly ,but I did find as the wind dropped to zero a rog or run launch would not get the rotors up to speed ,so still air operations will probably need a little more negative rotor reflex ,will fly again tomorrow with the rotor trimmed forward ,it looks like 5 degrees back will be about right.

 

Tom.

 

 

 

 

Hi Simon

Hope your getting over that bad cold ,my son has been quite ill with the same thing.

No problems with questions ,all are welcome just ask away .

Re your balance question,if you put the pins at 50% chord the angle the l/e points down should be fairly equal for each blade .

 

I did add the carbon l/e t/e before adding the twist .For the information of all ,Firstly be careful when applying pressure to the rotor T/E mine ended up a fine profile (which I think accounts for the high blade efficiency) but could be easily fractured by excess hand pressure.

 

The so called blade twist is interesting as mine is a progressive t/e turn up emanating from a point 6" inboard from the blade tips ,the leading edge remains at a constant angle to a parallel surface.This works very well except in very low or nill wind conditions then the blades wont get up sufficient speed to fly.

 

If l/e tip has a little negative incidence and combined with the positive t/e it could now be said to have a twist. This (twist) runs up much more readily even in nill wind but may be a little less efficient ,not that would be noticed as a significant change in performance.

 

The build is looking good Simon,the blade weight could probably be adjusted by extra coats of sealer.

 

Cheers

 

Tom

Hi Stephen

 

Thanks for the photos your build is coming on well.The hang angle you have selected should be about right.

 

The rotor section also looks very good but if I am correct you may have omitted the rotor root tongues ? and its hard to see if the the rotor bolt holes possitions.

 

The lack of tongues could effect flap resistance and so coning characteristics (i am sure you know this) but the changes to the original design may also result in differing trim and control characteristics,how much is not easy to predict.

 

Also blade strikes could result in more damage to all parts of the head and blades ,The c/g position will also be different with the blades fixed at 30% But your approach seems to comply with convention so give it a try and let us know the results.If it still performs the same as my version that might suggest that very low rotor loadings result in high tolerance to design changes.

 

Keep us posted

 

Tom.

Posted by Tom Wright 2 on 24/01/2012 18:24:10:

Crane Fly Autogyro

 

Second test flying session

 

WITH ROTOR TIP WEIGHTS FITTED

 

A 3g weight was fitted to each blade tip.This was tried to check the effect on the amount of left rotor trim required.

 

Again the wind speed was nil so rotor spin up was tricky .The first taxi runs revealed a tendancy for the model to roll left ,it did not do that without weights .Application of right rotor helped and with the rotor roll head trim now set at zero ,the flight characteristics were similar to test one but now some control lag was evident but this was not a problem.

 

I conclude that the roll right on the ground was due to the lack of motor offset to the right but the original set up was generaly easier and required less head scratching .

 

More tommorow

 

Tom.

 

 

Hi Simon

The final set up suggestions have not yet been posted ,flying has taken priority due to the calm weather ,will try and post tomorrow.Can say though if your using the recommended servos with three holes per arm I am on the middle hole.

 

The hang angle on mine at the moment is on the shallow side about 10- 12 degrees.

 

Tom.

I'm using MG90's on mine which have fitted perfectly. Be good to see your final settings. Might be worth quoting a distance from the horn center with regards to servo throw etc.

 

Cheers,

 

Simon

Simon quick link pivot to arm centre = 10mm. The mg 90s do fit well .

 

Cheers

Tom.