The Atom Special

[John T]

O.k, tried again today.

Slightly thicker shims and the rotors spun up more quickly than before. There still seemed a lot of lift and I managed a short flight before I got disorientated and ended up with another walk to collect it from the hay field. No damage this time. It's a strong design Rich!

I flew another model for a bit while I had a think and decided to increase the shim thickness a bit more (an extra 0.2mm in total). The next attempt was much better. The rotors spun up quickly in the breeze, and when it was airborne it seemed a little less "pitchy". For the first time I actually managed to land it on the patch . Very pleased with myself! I'd almost resigned myself to another trip to the hay field.

One thing I am having trouble with is disorientation. I think I might put a large orange patch on the outside of one of the fins to see if that helps.

[Mark Bishop]

RCM&E Atom Special by Rich Harris. 12 flights so far, without incidents. My first autogyro, a great challenge and a lot of fun. I have a Revolver which will be ready when the latest COVID lockdown in Melbourne, Australia finishes.

thanks Rich.

[Andy J]

Whilst waiting for a Panther parts to arrive thought I would re commission my old Atom which I never got flying. Thought there was some crash damage to repaired but apart from cleaning off the cobwebs little has to be done apart from repairing the blade hubs reinforcing ply.

Two apparent issues need to be looked at though, the first being that the thin plexi glass triangular head plate which has been stiffened with thin ply allows the blades to hand down at an alarming angle. Is this correct or do I need to go looking for a stiffer material?

The other fault is the control rods to the head which are M2 have bent so the loads are obviously too great. Did note the build did use M2 but thinking a M3 shaft may be better.

 

Edited By Andy Joyce on 18/08/2020 11:11:15

Edited By Andy Joyce on 18/08/2020 11:13:50

[Andy J]

Cleaned up the blades to add the shims but noted there is a mass error between them;

22.96grm 22.92grm & 22.76grm so the max error being 0.2grms. Do I need to reduce this error and to what accuracy?

[Richard Harris]

Mark,

I missed your post, great job on your Atom and good to hear you have managed to get 12 flights under your rotors

Andy,

I would stick with the 0.8mm thick FG sheet triangle as it was tried and tested before publication, you may get a bit of blade hang but not a lot. Also, not sure if it is the photo but it looks like your LE may have a radius on it? if this is the case you may struggle to get the blades to spin up, much better with a sharp lower edge,

Regarding your blade weights, the closer you can get them matching the better.

Rich

[Richard Harris]

Double post......

 

Edited By Richard Harris on 18/08/2020 22:14:31

[Andy J]

Thanks Richard will now purchase the correct thickness material to make the head plate.

As to increasing the weight of the lightest blade am I better adding this mass at the longitudinal CoG position or at the blade hub?

[Andy J]

All can ignore my last para in the above re blade balancing. When I measured the CoG position of each blade I noted the lightest blade (the one in the middle of the stack as pictured) has a CoG position ~2mm further out from the hub root and explains why all three blades balance with each other on a static two blade balance bar set up.

So to keep the current static balance the same, intend to add approx 0.2grms of mass close to the root of the lightest blade.

[Andy J]

New blade plate arrived today so managed to get all three newly balanced blades mounted.

Then thought that given there was a wind blowing today I would do some testing of the blade rotation. In the back garden surrounded by trees and walls the turbulent wind did get the rotors spinning but not at high speed. So then proceed to take the model to the front of the house which had less obstructions. It was at this point that the rotation speed suddenly picked up with the rotors making the necessary swishing sound so flight speed was obtained. No noticeable vibration or lift was noticed whilst holding the model but I then realized I had no means of slowing down the blades. Think at this point I tried pitching down the model to face the wind but then the blades or head must have deformed and the result was a tail strike with the parts quickly being blown away.

So the moral of this tale is don't try run up tests in high wind!

 

 

Edited By Andy Joyce on 21/08/2020 13:45:34

[Richard Harris]

Andy,

Your lucky it was only the tailplane and not your head that got caught! It's safer if you have the model turned on and power to the head servos when testing blades in the wind, words of wisdom and don't ask how I know

Rich

[Andy J]

Had been using that method of applying power to the model Richard but as I stood up after putting a 450 helicopter on the ground some years ago I knocked the throttle as I stood up. The resulting spin up caught my leg inflicting several deep cuts requiring A&E treatment. Result is that helicopters are now banned in my household.

Don't wish autogyros to be included in that list, so will take extreme care in future.

Just acquired an Astro 15 gearbox, so the Panther will be next model on the build list.

[Andy J]

Tried some rotor tests today but finding the walking pace runs all end quite abruptly when the rotors begin to turn at a faster rate with the model turning sharply to the right which cant be controlled with the rudder. Is the caused by the gyroscope effect of the rotor when the tail lifts from a three point contact with the ground?

[Richard Harris]

Andy,

If your model is rolling to the right it probably needs trimming to the left. I am pretty sure my rotor disc was trimmed a few degrees to the left for level flight.

Rich

[Andy J]

Yes I did put some left trim on Richard but not sure what the issue is. Possible is just a tweak required to the undercarriage. Note the motor has no offset. Should it have any?

[Andy J]

Just found you added 1 deg to the left in your original article published in RCMF.

[Steve Colman]

Just recently started flying the Durafly Auto-G2 and I've become totally hooked. I think that the Atom would make a good follow on model to further pursue this fascinating world of autogyro's before moving on to something like the revolver2.

 

Does this seem like a sound plan or should I consider another route?

Many thanks.

 

[Richard Harris]

Steve,

 

The Atom Special is a very robust autogyro that is cheap to build and fun to fly.

You will have no problems with it if you are happy flying the Auto G.

Coolwind sell all the necessary bits and theres a rumour AJ blades may be starting production again.

 

Rich

[Steve Colman]

Many thanks for your reply Rich, I was kind of hoping you would respond.

I have set up an account with Coolwind and it would be awesome if AJ Blades started up again.

Cheers,

Steve.

[Cliff 1959]

Hi Guys,

I'm cracking on with building the Atom Special (with a couple of mods of course), some of you may have seen my videos on YouTube, are there any tutorials on blade making. I've found a couple of videos but is there one specifically for the Atom? Sorry if it's contained within this thread but a search revealed no info. on recommended construction.

Cliff (Cliff Harvey RC Planes)

[Stephen Jones]

On 18/09/2014 at 20:45, Steve Jones 2 said:

 Here You go Cliff ?

It is not hard or expensive just time consuming. 

Or you could follow my videos ?

Steve.

 

 

 

 

 

 

Rich is the master at Blades and has posted several videos and threads on 'How to'....

Here are some pic and the process i use for mine...

 

The blade blanks are made from the selected hardwood or spruce leading edge and 6mm balsa. For this i used 6mm sq and 46mm balsa to give a 52mm wide blade. Slightly wider than the AJ as suggested. As you see I tape them on Grease proof and use 30 min expoxy to join

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Leaving overnight to set straight

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Then the fun bit with a razor plane carefully rough profile

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Keeping the leading edge sharp and the trailing not too thin to allow for sanding

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Rear cut outs added and before the root is cut at an angle the blade cord balance is found (CoG) using pins and some scap triangluar.

A line is marked on the blade 1mm behind the balance point to give slightly forward CoG

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Reinforcement plates are cut from 0.8mm glass fibre sheet

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And stuck in place

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Another view of the sanded profile before reinforcements added

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Next a 4mm 0.4mm strip isadded to the blade TRAILING edge to give slight negative shim for spin up

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Once this is done the 3mm mounting holes are drilled and the balancing begins.

Will follow up with more pics soon

Steve

 

 

 

 

 

 

 

 

 

 

 

 

 

[Cliff 1959]

Cheers Steve, just what I needed, this lot will keep be busy today while I'm at work lol

[Cliff 1959]

Hi Steve, I've made my blades but I was wondering about the angle you've cut at the root end, I don't see that mentioned on the pdf, is it necessary?

[Stephen Jones]

1 hour ago, Cliff 1959 said:

Hi Steve, I've made my blades but I was wondering about the angle you've cut at the root end, I don't see that mentioned on the pdf, is it necessary?

Hi Cliff,

I quoted Steve Jones 2 post above They are Not mine.

 

But, yes the root thickness is important in order to achieve down angle of the blade when it is bolted to the Delta plate. Also you need to glue a shim to the underside of the blade to get the down angle of the blade on my blades 1/64th ply was all i needed but you can adjust by adding more.

Cheers, 

[Stephen Jones]

Hi, Cliff

 

I have just checked my video and it does show that i remove 30 mm x 80 mm triangle from the root trailing edge leaving 20 mm at root.

After i have found my balance point I glue 20 mm x 50 mm ply strip at root drill my anchor hole 20 mm in then remove a small triangle section of this allows the blade to have a downward angle so that the leading edge is lower than the trailing edge.

Hope that helps if not ask richard or Steve Jones 2.

 

I made my blades lighter than the Atom blades and a little narrower to aid a better spin up.

I can not see why they would not also work for the Atom.

 

Cheers. ?

[Richard Harris]

Enjoying the videos Cliff, you should  to link them here for others to see?

 

I think the taper your talking about is at the root of the blade?

Many years ago before fibre glass plates were thought of  we used to make 15 degree delta heads, these were very much like the original HK head. The plate uses a polypropylene hinge in order for the blades to flap up, this hinge line was offset by 15 degrees in order to help spin up and rotor RPM. If you lift the blade upwards it induces negative incidence to the angle of attack of each blade.

I adopted this idea by taking it from the plate to the blade root on the Whippit and have used the idea ever since, It seems to work as I have blades with no negative shim and they spin up well. I also tried a funny shaped triangle also with good results, its just a pain to make so stuck with the simple idea.

 

Rich