Autogyro project

[Roy Hill 3]

I have set myself a project to see me through the Autumn and Winter and into the Spring of 2019. Having seen a video of the German Autogyro MTOsport, I was smitten and I have to build a 1:5 scale model. I have assembled a list of requirements and was given, what I think, maybe a suitable motor. This is where the bottomless chasm of knowledge and advice available from the RCME readership comes into play! The motor is a 30cc Big Bear, from a redundant strimmer. My questions are:- How should I produce an 'interface' between the existing output onto which I can secure the propeller? What size of propeller would be appropriate to keep the model reasonably scale? Should I leave the existing 'pull start'? As the rotor disc will be about 2 meters across, what material should I use to construct the blades? I have perused all the existing videos and threads available but would welcome any further information. Happy landings, Roy

[Roy Hill 3]

Following my last post, progress has been made. At present, the only plans I have to refer to are from the Pilot's Handbook, scaled up! Photos will be on subsequent posts. I have elected to dispense with the strimmer motor and gone electric. Once I have established the AUW, I will be able to calculate the size of motor required. I have made a base for the cockpit from ply and fuselage formers from liteply. The trike undercarriage is constructed and fitted. I am now looking at building the rotor mast, which has thrown up some questions! Should the mast be 'off-set' as in the full size? How do I calculate the size, (cord and length), of the rotor blades. Having studied the posts by the learned Tom Wright, does anyone know if the rotor heads which he uses are still available or do I have to fabricate one myself? Any help and advice is greatly appreciated. Happy landings, Roy

[J D 8]

Some pics of this project are needed I recon.

[David P Williams]

Hi Roy - you probably already know, but the UK agents for AutoGyro are Auto-gyro.co.uk, based at Halfpenny Green (sorry, Wolverhampton Business Airport as it now calls itself).

I used to work for them when they were Rotorsport UK based near the Long Mynd - that part of the operation is now the compliance/licensing/continued airworthiness unit.

They're nice chaps - if you're anywhere near Halfpenny Green I'm sure they would be happy for you to photo, measure, etc. If not they may be able to supply pictures, drawings and relevant info.

Edited By David P Williams on 16/09/2018 19:12:56

[Richard Harris]

Hi Roy,

Nice project and one on my 'to do' list. To answer your question regarding the offset head, this is done to compensate for prop torque and whether its to the left or right depends on the prop rotation. I have tried this method on my Mantis design and it works fine, it just looks odd with the control arms angled to one side. The tried and tested method on our pusher models is to offset the motor. The amount depends on several factors, prop used, distance of the fin from the prop and position and size of the vertical fin.

Because of the engines mass on a full size it is impractical to do this so they will either offset the mast or more commonly use rudder trim to suit. To those that can remember there was a micro Mold kit of the Wallis many years ago, the designer built in rudder offset and profiled the fin to have a flat bottom aerofoil to try and overcome this issue. I believe they were not very successful as I'm sure all of these extra 'get arounds' were subject to change from one builder to another. With the offset motor, rudder compensation through all of the RPM range is neutral and is the way I always go.

Another point worth noting is the forward sweeping mast, this is purely to get the CG correct with two pilots on board, this is always a tough one to get around when putting pen to paper designing a model.Far easier with an electric version as you can move LiPo's around to get things correct, its increasingly harder with a lump of IC engine position where you don't want on a miniture version.

The HK heads are no longer available which is a pain, but at a 2 metres rotor span it would be too small anyway, you will have to build your own I'm afraid.

Good luck with your project

Rich

[David P Williams]

Yes the full size MTOSports have a degree or two 'sidethrust' on the engine, plus the rudder is setup with an offset with the pedals at neutral.

[Roy Hill 3]

Great replies, Chaps. Firstly David. I was aware of AUTO GYRO UK. I wrote to them asking for some drawings or dimensions. They put me in contact with the manufacturers in Hildesheim in Germany who in turn put me on to the chap in Southern Germany, who is licenced to build scale models. He invited me to buy an air-frame kit at 1500 Euros plus delivery! Since then, I have got to know the owner of a full-size MTO Sport at the local airfield who has given me 'carte blanc' to photograph and measure at will. Great guy. Thank you for the info on side-thrust etc. JD8 - I will post some progress photographs very soon. Richard - Thank you for your input. Your note on the forward sweeping mast is very interesting. In order to reproduce as much scale as possible, I will construct one straight one and one as per original. I suspected that the HK head would be discontinued, so I will manufacture one. Once again, pictures to follow and thank you all. Roy

[Roy Hill 3]

Sorry about the delay since the last posting. Birthday, Regimental events, family matters and a computer which refused to accept photographs have caused a bit of grief. However, some progress has been made. This was all I had to begin with! I toyed with the idea of enlarging the the page from the Pilot's Handbook but, of course, as the image enlarged so did the lines. Out with the Vernier gauge and the calculator, then copy onto the drawing board. 3-Ply and Liteply was sourced and cutting began. A bit of 'fettling' and all looked well. I stumbled upon an oleo from a redundant (crashed) Chipmunk, which will serve as a steerable nose-wheel for the MTO Sport. There will be considerably more sanding and fettling to be done at a later stage.

A break from carpentry followed with a return to metal-work in the shape of the undercart and tail-boom. Bending the ali into the correct angles was no problem using the tried and tested method of soap and heat. The tail-boom was a different story! The last time I welded ali was in 1964 so I elected to use 'fish-plates' and rivets. Certainly easier but not quite as scale as I would have preferred. Considerably less bad language, though.

Who could resist a trial assembly to check that things were going according to plan. I have used nylon bolts and blind nuts on the undercart and tail-boom assemblies to reduce the possible damage on landings. It appears to be a bit 'nose-down at the moment. It's not as severe as the picture suggests but some realignment will be required.

The current job is forming the solid nose, which will be in 2 halves.

I'm reasonably pleased with it, at present. I'm now engrossed in drawing the tail feathers which will be increased by some 10%. The mast(s) will follow, one will be scale to include a forward tilt and the other will be straight. I still need some advice on how to calculate the size, (length and chord) for the rotor blades. If it were to be absolute scale the rotor disc would be 2.2 meters diameter. I will be constructing the blades myself, so any advice would be greatly appreciated. That's about it for now, folks. Happy landings, Roy

[Roy Hill 3]

Hello all. Other commitments have hindered progress recently, however I am now back on the case.I am designing and constructing the 'teetering' head and rotor blades but I need someone, Tom Wright perhaps, to confirm my blades size calculations. The expected AUW of the aircraft is about 7 Lbs (112 oz) and each blade should be 36 inches long and about 2 inches wide. Using Tom's formula, from a previous post, it should give me a loading of 3.96.This is at the top end of suggested measurements. Does anyone have any comments or suggestions before I get the tools going? Roy

[Former Member]

[This posting has been removed]

[Roy Hill 3]

David. I'm so sorry. It must appear quite insensitive of me. Perhaps I should have asked for Richard Harris to help me. Regards, Roy.

[Roy Hill 3]

Hi Chaps. Work on the autogyro continues, albeit at a rather slower pace than I would enjoy! I have constructed a prototype teetering head, which works reasonably well however have come to a stand-still. Where can I obtain a linear servo to engage the pre-rotator? I've searched the internet and all those advertised are no longer available and they are from USA, anyway. I've seen some 'conversation kits' which are also sold out!

Does any-one know where I can get one? Happy landings,Roy.

[Piers Bowlan]

An interesting project Roy. Have you considered using a separate motor to spin up the rotor head? Probably wouldn't need to be too big and perhaps that way you wouldn't need a clutch, or a servo to drive it for that matter. Another thought, is that I used to have a MFA sport 500, back in the day, which had a sprag over running clutch in the head. Could be useful as you don't need to disconnect the drive, just stop the motor and the rotor free-wheels. This type of thing. I guess these clutches are available as model helicopter spares too. Good luck.

Edited By Piers Bowlan on 09/01/2019 06:55:28

[ken anderson.]

nothing to do with your thread Roy...Tom Wright was a very nice and generous man...RIP, and also young Rich Harris.....both very helpful...thanks to them both...

ken anderson...ne..1....appreciation dept.

[Roy Hill 3]

Thanks for that, Piers. I toyed with the idea of using a separate motor to spin up the rotor head but it would need some way to disengage otherwise the rotor would eventually be driving the motor. This would facilitate a linear servo! The thought of using the clutch crossed my mind however I think that this would involve bearing internal sizes matching splines and so on. Thanks for the input anyway. Hi Ken. Agreed! Regards, Roy

[David P Williams]

Roy - if you have a look through the large Panther autogyro thread on here you will see at least one example with a pre-rotator built using the main gear and one-way autorotation clutch from a 450 size heli, so the rotor never drives the motor.

[David P Williams]

Found it - it's halfway down the page here

[Roy Hill 3]

Hello David. Thanks for that info. I will give it greater scrutiny later! Roy