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The Atom Special

A simple to build, tough autogyro with racy looks

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RCM&E Special Issue preview!

RCM&E Special Issue preview!

in the shops 19 Sep

Richard Harris12/08/2014 10:44:43
2061 forum posts
1892 photos

Around 3 weeks ago I was asked to design an autogyro to fit onto two A4 sheets with the intention of slipping it in to this years Special Edition.

I do like a bit of a challenge so set about the task the next day jiggling parts of a very simple design within the dimensions of A4. The hardest part was the mast length, I could have gone across the diagonal of a sheet but this would have restricted room for other parts. In the end I used the maximum length available and removed the vulnerable centre fin, opting for a twin fin set up. As there would be some sort of mechanism/ bellcrank set up at the rear I 'beefed' things up by adding two booms, making it far more rigid and a good sturdy mount for the tailplane.

Once all the parts were figured out I was left with very little room on the sheets. To get the fibre glass triangle to fit it had to be significantly smaller than what I would normally use. This was my biggest concern and I only managed to test this out this time last week due to the turn in weather. Luckily for me it worked perfectly and the maiden went fault free. Infact, I am really pleased with the results as it flies easily in light winds and handled the wind at Greenacres without any problems at all.

Because of its size I have named it the Atom Special. It uses the Hobbyking C30 head and because of the time constraints I was under I opted for a set of AJblades (44mmx450mm). If potential builders want to make their own blades I will go through the process and make a set up?

It is an easy build that can be built from offcuts etc, if you think it would be beneficial to builders I can add a list of materials?

So, I have a second model part built and will finish this off in the coming weeks adding photos as I go along.

Unfortunately I have no flying photos, so I will leave this up to the powers that be to add some.

I hope it will be of interest?


David Ashby - Moderator12/08/2014 11:16:52
10918 forum posts
1674 photos
609 articles

Well done Rich, no pressure there then wink 2

We met up at last weekend's Greenacres fly-in to shoot the model and, as Rich says, it handles the breeze very well indeed.

It'll be a build article and plan in RCM&E's 2014 Special Issue that's out mid-Sept so gather up your gyro bits and get ready for an easy build.

Chris Bott photo.


Chris Bott photo. 

Edited By David Ashby - RCME on 12/08/2014 11:41:14

Edited By David Ashby - RCME on 12/08/2014 11:41:35

Chris Bott - Moderator12/08/2014 11:25:44
6670 forum posts
1382 photos
1 articles

Don't know about the powers that be Rich, how about these to be going on with?



Chris Bott - Moderator12/08/2014 11:26:53
6670 forum posts
1382 photos
1 articles

oooh - Snap! thumbs up

David Ashby - Moderator12/08/2014 11:40:46
10918 forum posts
1674 photos
609 articles

Yep, I'm in the office without Atom shots so I nicked yours Chris teeth 2

adrian lawrence 112/08/2014 12:18:34
164 forum posts

Head ordered in anticipation

Richard Harris12/08/2014 12:18:41
2061 forum posts
1892 photos

Thanks Chris thumbs up

Materials list , some of these I would think 'Mr Average' balsa basher would have kicking around :

2 off sheets of 3.2 x 102 x 915mm medium grade balsa (fuselage sides/tailplane/fins and sheeting)

1 off sheet of 6.5 x 102 x 915mm medium grade balsa (fuselage base and some formers)

1 off sheet of 9.5 x 102 x 915mm soft balsa ( fuselage base and balsa infilling)

1 off strip 6.5 x 6.5 x 1220mm (boom )

1 off strip 6.5 x 12.5 x 915mm spruce (mast)

1 off sheet of 3x 300 x 300mm birch ply (U'C mount/ servo mounts)

1 off sheet of 3 x 300 x 300mm Lite ply ( several formers)

1 off sheet of 0.8mm Fibre Glass ( head plate)

1 off length of 3mm (10SWG) piano wire (U/C)

1 off length of 1.2mm (18 SWG) piano wire (rudder coupler)

I may well have missed some small pieces as this is just off the top of my head.


1 off Hobby king C30 head LINK HERE

1 off brushless motor LINK TO THE ONE I USED HERE but anything similar will be fine

1 off 30amp speed controller ESC

3 off servos SERVOS

1 set of AJ blades HERE

10 X 7 APC prop

1550 mah 3 cell Lipo at least 25c

50mm lite foam wheels (minimum)

6 off 3mm bore wheel collets (wheel retainers and bell crank retainer)


Pop bottles!!!!


Chris Jones 712/08/2014 12:27:40
282 forum posts

I really like the look of this but..... Is there a reason Autogyro masts are so long? I imagine it's to allow the blades to tilt back a little for lift and to get the air under them(?) but they look so ungainly. I was imagining this with the rotor hub almost on top of the canopy and think it would just look so much cleaner and well, sexier!

Question is, if it couldn't be done with the Atom, could it be done at all? (please note this is no criticism just an observation and a question. I know nothing about autogyros!)

Richard Harris12/08/2014 12:57:39
2061 forum posts
1892 photos


Good question, the Atoms mast is in fact short compared to the norm.

You are correct with your thinking though regarding the mast length, it has to have it's rotor tilting backwards for it to function. It's disc also tilts backwards and forwards/ left and right to give the autogyro direct control at any speed (including backwards flight). So some clearance is needed to stop tail strikes.

But a longer mast also adds a degree of stability and pushes up the CG position making it more manageable in pitch with different throttle settings.

No reason at all why you couldn't experiment?


Vecchio Austriaco12/08/2014 13:14:31
1498 forum posts
707 photos

looks interesting. could be a mass build candidate for 2015?


Chris Jones 712/08/2014 13:51:47
282 forum posts

Thanks Richard, bit beyond me to experiment I'm afraid but I think it would be an interesting thing to play about with for someone more talented.

Andy Nash12/08/2014 21:07:00
128 forum posts
29 photos

She looks great Rich.

Does it take off from water; it’s raining cats and dogs here!

Water floats perhaps, but is there enough space on the page?wink 2

Serious mate looks good, well done.


Richard Harris12/08/2014 22:24:36
2061 forum posts
1892 photos


As much as it would be good as a mass build I very much doubt it would happen.


Clear as a bell here mate, in fact I may pop out and see if I can spot some Perseid Meteor shower action later on!

First job will be to transfer all of the templates from the sheets onto their specific material. I have attached mine to some stiff card board and will cut them out so they can be re used if I feel like building a third model.


Richard Harris13/08/2014 10:57:00
2061 forum posts
1892 photos

Templates have been glued on to sheets of card with spray adhesive, then it was just a simple task of cutting them out with a pair of sharp scissors with a sharp scalpel being used for the holes etc.

On the prototype I just glued these directly to the material to be cut, removing the paper templates after with solvent.

Just a simple case of cutting round them to create all the parts needed now, particular attention is taken to the grain direction with the balsa parts. Shouldn't take too long smile




Richard Harris13/08/2014 11:52:03
2061 forum posts
1892 photos

There are a couple of holes to be cut out for the rudder servo, you will note I have added a semi circle to one side. This is for the servo lead to exit out of, a quick way to to this is too drill a 5mm hole like this


Then cut the rest out, job done.



Richard Harris14/08/2014 10:25:01
2061 forum posts
1892 photos

All bits are now cut out, but before the build commences there are a few formers to laminate.



The bulk head pieces F1 and F2 made from 3mm lite or birch ply.....





I didn't have any 3mm lite ply, only a  bit of 2mm so I will add an extra face to the front using 1.5mm birch ply.


The main formers F3 and F4 again are made from 3mm lite ply (these are from 2mm but it will be fine) but to there inner face are added cross grain 6mm balsa. using a piece of suitable 6mm spruce as an aid to get the correct slot between both, this slot will end being the mounting hole for the mast.....






The 10mm holes are for the servo leads to pass through.


UM1/UM2 and UM3 make up the U/C mount, again I had no 3mm birch ply so laminations of 1.5mm have been used. At the moment the two holes drilled are pilot holes.









Edited By Richard Harris on 14/08/2014 10:26:51

Edited By Richard Harris on 14/08/2014 10:29:25

Richard Harris14/08/2014 11:44:48
2061 forum posts
1892 photos

Everything is built around B1 which is made from 6mm balsa, I have no 6mm balsa left until I get to the NATS so some 5mm will have suffice. To the front of B1 is added B2 made from 3mm birch ply, this is the top reinforcer for the U/C legs which will have to be drilled later.

To the rear is glued centrally B3, on top of this is B4 with opposing grain direction.




This creates a kind of 'H' section which when the fuselage sides are in place gives us the square mounting holes for the booms.

In the middle of this lamination is mounted the rudder servo.Whilst it is easy to get at I trial fitted this servo, trimming where needed then added a couple of ply strips for the servo mounting screws to bite into.



Richard Harris14/08/2014 13:00:06
2061 forum posts
1892 photos

Moving on, one of the fuselage sides is glued to the rear parallel edge only making sure it is flush with the base of B1.


To the fuselage side at the rear end is glued D1, this will reinforce and position formers F3 and F4


Before fitting in place these formers their bottom surfaces are angled with a file so as to get a good joint with B1.


When done B4 can be mounted and glued square up against D1.


Then using a piece of 6 x 12 spruce as a guide B3 is butted up and fixed flush.


Removing after to reveal the mast locating slot



Richard Harris15/08/2014 10:25:47
2061 forum posts
1892 photos

A little more this morning.

Before progressing with the second fuselage side I added some hardwood servo rails, these to have a thickness of around 6mm. Mine are made from laminations of 1.5mm birch ply. Once on, I cut out excess balsa in the servo holes and drilled holes in the rear for the leads to run through. A bit rough but it won't be seenwink 2



The second fuselage was then glued in the same way as the first adding D1 at the rear.


Just a simple case of pulling in the fuselage sides at the front then adding the bulk head ( 5 min epoxy on this joint).



B5 is then added flush with the top of the fuselage sides butting up to the bulk head



Richard Harris15/08/2014 10:51:12
2061 forum posts
1892 photos

The rear of the fuselage top has now been sheeted with 3mm thick soft balsa, matching the radius to the rear of the fuselage. Soft balsa block is added to the top front of the fuselage directly on to B5, it has to be made up to a minimum of 30mm to get the required arc from back to front. The two photos below should give a good indication of what I mean, I will add some blocking on the underside as well to get that arc.



I have already made a plug for the prototype and this is covered in mag write up, I see no point in making another. But, it is just a simple case of infilling where it will go and sanding to shape so that it matches the bulk head top and the formers at the back.

I could make a blue foam one as an alternative if potential builders would like to see this?


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