Crane Fly Trainer Autogyro

Rich

If you have a photos of a light weight bearing / housing set up that leaves the flapper top clear of projections 3mm or less please post as it would be of interest., this is the spec that I have now focused on for the Crane Fly,I have several flat top versions flying well, but would like to come up with a simple solution to keep within the thread spirit.and allow the blade tongues or hubs free movement over the plate when in ground strike mode.

Thanks

Tom.

Tom,

Boy its cold out there!

 

I am not sure I understand what you would like to see that may be of help, but here are a few photos I just took of a few of my heads with a 3mm shaft or smaller.

 

This is of my Little Little Nellie head, the flexible plate is bolted onto the top and captivates the top bearing, the lower bearing is captivated with a ply plate. The main hub is MDF, this worked ok but after 20 or so flights the bearings started to elongate the bore. This was cured by making a new one up and soaking the bore in CA. Works fine but was hard to balance the hub with all the mass around the blade centres. This is the head that the 3mm bolt sheered off with my out of balance blades. I gave up on this one. The round plate underneath is to stop the blades drooping and taking out the tail as the triangular plate is .8mm thick.

 

The next head is the REX head which was the test it and see model for my Nellie, the photo shown is the Mk 1 version with 3mm ID flange bearings. These worked for a while but kept failing on me, these were up rated to 6mm ID bearings and it was tested hard with over 100 flights before I was sure it was safe. Uses a simple GF disc top and bottom, these had to be doubled up to take the 6mm bearings. This works really well.

 

These are a few photos of heads that use a 2mm piano wire main shaft and a brass tube, below the head is a brass tube spacer. The whole assembly is held on at the top with a brass wheel collet. These were used on the small C30, Hobblite and Stilleto designs and again worked well. The main hinge for the head is silicone fuel tube which works fine for the small light weight models, the heaviest is about 150 grammes.

 

Last one is the same kind of theme and was used on some very early boom type models. Ply disc top and bottom with with a brass tube 1/8" diameter running up the centre. Again these were captivated using wheel collets. They worked ok but at that time I just couldn't keep an autogyro up long enough to let you know if they were up to it! I adopted this idea for the Twist.

 

Hope this gives you some ideas?

 

Rich

Just like to say its been great so far, very informative and simple, got my gyro fuse built, can't wait to test fly her.....

 

Graham.

Thanks for the photos Rich ,yes your right its cold out there, just got back from a three hour gyro session with four of the lads.

The chaps following this thread should note one of your photos shows a GF plate that has been scalloped to reduce stiffness ,Pete flew a 1.6 mm scalloped woven plate today on a 1.5lbs gyro similar to the Crane Fly,and it works well.I can post dimensions if anyone wants to use the easy to get high quality 1.6 mm GF sheet.

There are so many ways of producing a bearing housing ,as your photos show ,but having flown the bell motor mount idea a lot ,and as I now have a way of producing it with a low protrusion plate top,it will be the one suggested for the Crane Fly build

 

The flanged bearings came today and one in both ends of the bell motor mount does the job at a total cost of £4 .To save builders sending uneconomical orders to China I will soon have enough to post on just pm to be put on the list. .

 

This update to the plate and bearing housing will be posted asap ,so hang on if your about to assemble the bearing housing to the plate.

HI Flying dragon-uk.

 

Welcome to the thread and thanks for posting ,did not know you were on the build ,sorry about the delay in progress but the bearing change and several domestic commitments have slowed things down.

 

Tom.

Made up a plate with the flanged bearings this evening ,it is very light and low profile .

To complete ...three 2mm bolts will be added to clamp the housing to the plate more details to follow.

 

Crane Fly Autogyro.

 

Flange bearing update notes.

 

The flange bearings used are sourced from RC bearings LTD Middlesex ,bearing reference 3 x 8 x 4- F ,or pm me ,will send with 3mm long nut and GF (GF subject to availability).

 

The only tri plate mod required is to enlarge the center hole to 9.5mm clearance.this allows the bearing housing to be located under the tri plate. This arrangement also has the advantage of not requiring the spacer part from HK.

 

Preparing the tri plate fitting bearing housing GF washer and flanged bearings.

 

When the the faces of the tri plate have been sanded to a matt finish (do this outside preferably wearing a breathing mask).Mark out the tri plate as shown below.rub the bearing housing face over a flat piece of sandpaper to produce a matt finish,drill the 9.5 mm centre hole,and cyno to the tri plate making sure its spot on centre.

 

Cyno the gf washer on top of the tri plate again make sure its centered accurately ,when dry drill through the three bearing housing holes (2 mm clearance) and fit three bolts approx 6mm long 2mm diam, fit the nuts underneath using a trace of thread loc.

 

The flanged bearings can now be loaded into the housing ,do a trial dry fit first insert the rotor bolt and check for free rotation ,then using a trace of cyno or thread loc on the bearing flange inner face load the bearings and do take care not to get any sort of glue in the bearing moving parts.

 

 

 

 

 

 

 

Crane Fly Autogyro

 

Marking out the tri plate.

 

Check the triangle sides are all identical in length and the centre pilot hole mark is positioned so the three radial lines are of identical length.This may take some thought and some juggling to get spot on, so double check measurements before drilling any holes.

 

The point were the arc intersects the radials is the rotor bolt hole position and should be 25mm in from the triangle apexes.but do not drill the rotor bolt holes yet as any small discrepancies can be evened out after fitting the the bearing housing eg the distance from any bearing housing on line reference point to the rotor bolt holes should be equal.

 

 

 

 

Top view of the completed tri plate .

 

Bottom view of completed tri plate.

 

Cane Fly Autogyro.

 

Rotor blades continued.

 

Carrying on from the posts that describe joining the balsa l/e and t/e .also taking note of the stock selection comments to achieve blades of equal weight and strength.

 

Sand to a Aquila or clark y profile mine are nearer Aquila as shown below.

 

Aim to achieve an airfoil section max thickness of between 6.5 and 7.5 mm.

 

A simple profile jig could be made to slide along each blade ,this will make it easy to identify high spots and get a reasonably even section on all three blades.

 

An example of a simple rotor blade profile checker ,could be made from two 2mm lite ply off cuts laminated together.

 

 

 

 

Rotor blade root tongues.

 

Sorry about the rough drawing but it does give all the info to make this part.

 

The rotor blade root tongue ,QTY 3 required.

 

 

 

Fitting rotor root tongues .

 

STOP and think about this.....the rotors turn anticlockwise on this model so at this stage its would be easy to make the mistake of fixing the rotors to the tri plate with the t/e leading .

The rotor tongues must be fitted to each blade root with the L/E facing the direction of rotation.

 

The photo shows the blade L/E on the left, mark the three blade roots and double check before using med cyno to glue into place as shown ,do use clamps to ensure a tight joint. Just a futher reminder the tongues must be sanded to a even matt finish before gluing into place.

 

 

Rotor root tongues .

 

Discussion.

 

I have not seen this method of attaching light blades to the tri plate used on any other autogyro .I originally used it to reduce flap resistance on a over stiff tri plate.

 

This unconventional approach is bound to raise a few obvious questions such as is it secure just bonded with cyno ? why is the fixing bolt at 50% chord instead of 25-30%?

Well my comment on question one is .......ten autogyros flying from our local field use this method and a blade has never detached in flight ,part delamination has occurred during severe rotor ground strikes but pre flight checks should soon spot such a problem,and of course its easily fixed.

The security aspect of course relies on the bond quality,should builders have any doubts a mechanical back up should be used .One way of achieving this is to let in a hard point ,or points before bonding the tongues in place and screwing or bolting from the tongue underside into the hard point, if possible this should be done to avoid protrusions passing over the tri plate.and involve minimum additional weight.

 

Question two is easy to answer ..I dont know ! but what I have found is ...it seems to work well and ,results in the following advantages.....lower load transmission to the plate head and mast during rotor ground strikes ......less damage to blades ......and very quick and easy to replace .Theoretically there could be down sides but on such a light model the lads at the field have not been able to detect a difference between this and other methods .So it must be considered experimental and open to comment.

 

Tom,

Have you just glued the root on the underside of the blade or have you cut a slot to accept the gf root ?

 

Malcolm

 

HI Malcolm.

All my gyros have root tongues glued to the blade underside with cyno .A slot fix would make replacing a damaged tongue very difficult .

Fitting in a slot would normally be good practice but it could produce a shear boundary that may cause a blade break in a ground pitch over situation.or it could perform similarly,its hard to say without trying it and comparing results.

There are also other considerations but, to avoid rambling on to much the method suggested in the build notes seems to balance the strength to weight ratios quite well ,and this has been observed following plenty of hard knocks at the field.

It is very easy to make every thing twice as strong but the increase in inertia during crashes and the extra power to carry the extra weight can soon make a design unsuitable in terms of meeting the the original objectives.There's no such thing as crash proof model but suitably designed very light structures can take a lot of punishment particularly when flown over forgiving ground ,hard surfaces though generally take no prisoners.

If time allows I will do a static load test on both methods,thanks for the suggestion.

 

Tom.

After a lot of searching I found a UK supplier of 1mm smooth both sides woven laid GF.

Not cheap at £9 odd but one sheet should make three tri plates or two and enough left over for the other components .

 

Or if you build a larger scalloped tri plate this 1.6mm GF is excelent.

 

Take a look and if you know of a cheaper source please let us know.

 

To build a more sophisticated control mech this universal joint might come in handy for future gyro projects.

 

Tom.

 

Posted by Richard Harris on 02/01/2012 12:14:52:

 

 

 

I had a look at your thread, very interesting, but I think a possible reason for low build numbers, and probably will happen here to, is that the thread becomes impossible to read easily, unless you follow it from the start.

 

So you have the people who start with the thread, but by the time it gets to 5-6 pages, it is very hard to come in cold, it's almost a case of having to copy and paste all the essential bits into a document to make it readable.

 

I started reading another thread about the basic aerodynamics of gyros, and although the information was there, it is so padded out with extra words and comments, it is very difficult to read.

 

I have been considering a gyro for a long time, and when I have learnt all the reasons why they are built the way the way they are I will have a go.