The weather wasn’t very good this week, so I didn’t get to do any flying. The forecast was for heavy localised showers and, right on half past twelve, it rained. A lot. I might have got wet, or I might have got lucky, but, either way, it was just as windy as last week. If the weather had been calm, then I would definitely have had another go with the autogyro, but there didn’t seem much point with the weather like this.
I’ve been looking into the problems with the autogyro and come to a number of conclusions. Firstly, the video I captured was rubbish and didn’t tell me anything. If I try that again, then I’ll have to get the camera higher up. The next thing is that I don’t think I got the rotors up to flying speed as everything I’ve read says that there is a characteristic “whirring” when this happens. It’s supposed to take off at walking pace, which I achieved, but I think there might be something wrong with the rotor head. I went round all the factory fitted bolts and discovered that some of them were quite loose, which was causing a lot of play in the head. In addition to this, I’ve been reading the “Cruiser” autogyro build article from the November 2015 RCM&E, which is basically the same design as the earlier Atom. There is also the larger “Panther” autogyro article from the Model Flying Workshop Special, published in 2015, which contains all the original articles which were serialised in RCM&E from March 2013. These all contain basic instructions on the design of the head and how to test fly an autogyro. However, while they advocate short hops to ascertain the trim, I’ve seen a video on YouTube where an Atom was hand launched in almost gale force wind. This is something I’d never seen before, but you can apparently hand launch an autogyro very easily: https://www.youtube.com/watch?v=OdrfQxKu1Ik
This video is also interesting, as it suggests that the left wheel sticking to the ground is normal and that you can power on past it: https://www.youtube.com/watch?v=9OVpcZOvsOs
If the camera I was using had worked, then this is a carbon copy of my experience last week, except that I wasn’t brave enough to get it into the air. After some playing around on the ground, my feeling is that the left wheel coming up last is due to the anti-clockwise direction of the main rotor.
This is the other hand launch video of an Atom that I found: https://www.youtube.com/watch?v=5bVkgLwmBAc I’m just not sure I’m that brave.
Anyway, I’ve checked the balance by measuring the hang angle using some rulers and a bit of trigonometry. By my calculations it’s 18.5 degrees, which is spot on. I’ve also modified the 0.8mm shims on the underside of the rotor mounts as they were getting caught every time the blades got tangled up last week. I’ve now lengthened them and covered over them, but I suspect that this might be where my problems lie. When I spin up the rotors on the ground, I just don’t feel like I’m getting much movement of the air. Now, the HK head has a known problem in that it’s constructed upside down and shipped in a state where the rotors would give no lift (souce: modelflying.co.uk Atom build thread). I took it apart as directed, fitted the fibreglass triangle to replace the plastic one which breaks and rebuilt it the other way up. I’ve added the shims as instructed, which put the blades at a more negative alpha and aid in spinning up the rotors. I’m not convinced that this is right, though, so I’m going to do some more investigating before I try and fly again.
That’s it for this week, but work is taking over again, so I’m not sure how much I’m going to be able to do on the autogyro. I’ve got this close to getting it in the air though, so I’m not going to give up now.