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Twister a 2 bladed autogyro


Richard Harris
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This is my first attempt at a build log on the new platform, so if I mess up it's my lack of user time on the updated site and not my stupidity...honesty 

 

My new design the Twister is specifically dimesioned to suit a 2  blade rotor system. 

A few more considerations are taken in to account like a longer distance between motor and rotor spindle, higher mast and minimal vertical tail feathers.

Probably a little trickier to set but once once trimmed  just as easy to fly as its 3 bladed counter part requiring less power.

As we are now are able to obtain balsa I have finally been able to start this last week it. Its fuselage is a simple box structure with triangular box section inset into the corners with several lite ply forners keeping them apart.

All has gone together ok so far, even had a little help from my daughter (though not for long).

 

A few photos of progress. As you can see the mast assembly will slide in and out as per Panther and is removable from that part incase of a breakage.

 

Rich

 

 

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A little bit of elbow grease later and I removed a considerable amount of balsa givng me a roundish fuselage which seems light but sturdy. A bit more sanding to do but it's nearly there.

The rear end has also been blocked up and shaped leaving a slot for the tailplane.

The depron feathers are only dummies as I play around with different shapes. Once I'm ok with the lines I will transfer these outlines to balsa.

Onto the cowl next.

 

Rich

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Flash Gordon DD,  before my time.......?

 

Giday I made a start on the mast and servo mounts, going to fit some Corona MG slim line wing servos this time. I've not tried them before, they are mounted on a plywood spacer giving the correct clearance si that are flat on the mast mount sides. Nice and simple to mount and they will hopefully give me the torque needed for the load share 'Razor' head unit carrying two blades.

 

The two smaller 3mm holes will be for the spruce mast securing bolts. As this will be for 2 blades the mast is angled a little further than the standard 5-6 degrees as used with a 3 blade set up. This gives a better pushes the CG further forwards si as to not make the model pitch sensitive.

 

Rich

 

 

 

 

 

 

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Edited by Richard Harris
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It will be interesting seeing how those Corona wing servos hold up.  I know they're rated at 5kg.cm or thereabouts but the slim control arms and small diameter of the output shaft made me wonder just how much load they would really take.  Saying that they have worked well when I've used them for ailerons or flaps on .60 size models.

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Mike,

 

Thanks for the encouragement, I'm slowly beavering away at it but it is slow progress. The best mass builds have been those that are simple and quick to build, I dont think this would suit.

I have a friend in South Africa who has made a programme up that calculates rotor loading, I made a quick video on it a month  or so ago.

He has since  tweaked it further and if there is interest I dont mind making another video using it to calculate the blade length for this model in both 2 and 3 blades?

Not sure if I can upload the programme to this site so it can be downloaded to use, it's an Excel spread sheet, anyone know?

 

 

Bob,

I've not tried these servos before so it will be a bit of a test. I have used Corona mini servos in the past and they seem to have enough torque for this type of abuse.

 

Rich

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Mike,

 

Yes it will use the Coolwind Razer head, though I will be testing this head unit on top of it. It's been sent for me to me by a friend and features a 15 degree delta offsite with a free flapping hinge, all 3D printed. Uses a 3mm wire as the hinge which is inserted into the main fixed parts. Need to add bearings and M2 bolts/nuts.

The U/C is a simple home made job and the spats were picked up from the Much Marcle LMA show in 2019, I bought a couple of sets as they were £2 a pair, wish I'd of bought more!

 

Rich20210428_204212.thumb.jpg.a66fbc1b80dc45461012adba8975fe33.jpg

 

Edited by Richard Harris
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  • 4 weeks later...

Slow progress but it's now kitted out,  all that's required is a light sanding then covering. As it stands at the moment it weighs a pleasant 950g with Lipo fitted, this gives me a good idea of what rotor span is required.

I will press on with covering then move to blade construction, the ones fitted in the photo are off another model just to mock up.

Hopefully by then we may get some warmer weather!

.Rich

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7 hours ago, Mike T said:

Smart! 

But in the 2nd pic, that servo seems to waggle the sub-fins laterally on their fore and aft axis?  I can't see what that achieves... ?

Mike,

There are rudders  inset into the sub-fins, their surface area amounts to a modest single rudder. So I'm hoping they will give me some form of yaw control. 

 

DD,

Of course a screen of some sort will be made as he prefers to fly without the goggles. Will knock something up this week.

 

Rich

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  • 2 weeks later...

Covering is virtually complete, this HK stuff really does shrink well. Just need to make or purchase some decals.

I had a go at making some litho plate bubbles to neaten up the push rod exits, this took me a few attempts to get something useable, I was given some good advice from a few fellow club mates.

I wasn't happy with the standard spinner so I machined a larger/longer one which I much prefer.

All the radio is now installed and those 'strange' rudders operate smoothly, how effective they will  be is a different matter.

Blades are next up to which I have made the blanks up out of some 1/2" balsa/ hardwood in readiness for a session on the belts sander, hopefully over this coming weekend all being well.

 

Rich

 

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Edited by Richard Harris
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