Larking about...
Posted: 03 May 2020, 15:42
For Christmas, my son gave me a Lark Mk2 kit that he found on Ebay! The seller had started construction, but not got very far before abandoning it. I decided to convert it to electric, as I've already got two i/c powered Larks.
Martin Briggs and Martin Kaye had already done some work on this and sent me some CAD files. I'm fortunate in having an old friend with a CNC milling machine and a lathe, and he knocked me up an adapted chassis plate and motor mount:
Construction of the rest of the heli took longer than expected, as the previous owner had made a number of mistakes in construction, which I had to rectify before I could continue with assembly. However, a week ago it was ready for some tentative hops to see if I had the gearing right or not:
This was on a 3S pack, and was pretty marginal, but at least I was in the ball park. Unfortunately, the ESC I had intended to use died without warning before I even had chance to fit the rotor blades! It had only been powered up to set up the radio gear and make sure the motor direction was correct, and then it just stopped working!
I had an old spare kicking around, but it was limited to 3S, so I couldn't try it with more power.
I ordered a new ESC (different brand!) and a new pulley to raise the gearing. These arrived a couple of days ago, and were promptly fitted! I also made a proper battery tray, as the original method didn't seem secure enough to me:
BattMount-2 by Peter Christy, on Flickr
BattMount-3 by Peter Christy, on Flickr
BattMount-4 by Peter Christy, on Flickr
I also replaced the paddles that came with the kit with ones from a much earlier Lark. The ones that came with the model were mismatched by over 2 Gms, and even after balancing caused quite a bit of vibration. The older ones were matched to better than 0.01 Gms, and run perfectly smoothly!
Today I test hopped it in the garden between showers. No video as I didn't want to get the camera wet, but on 4S it was airborne at less than half throttle, and running MUCH smoother!
I haven't let it get out of ground effect yet, as there isn't much space in the garden! It is also quite tricky to hold a heli in the hover until it has been properly trimmed - which requires being out of ground effect! Also, I've had the motor cut once, and hiccup a second time, for reasons that are unclear at the moment. Not sure if its a receiver issue or an ESC problem, like I had with the Cobra, so I'm being very cautious for the moment.
Anyway, its keeping me occupied during the lockdown! Next up is to electrify my DS-22.....!
--
Pete
Martin Briggs and Martin Kaye had already done some work on this and sent me some CAD files. I'm fortunate in having an old friend with a CNC milling machine and a lathe, and he knocked me up an adapted chassis plate and motor mount:
Construction of the rest of the heli took longer than expected, as the previous owner had made a number of mistakes in construction, which I had to rectify before I could continue with assembly. However, a week ago it was ready for some tentative hops to see if I had the gearing right or not:
This was on a 3S pack, and was pretty marginal, but at least I was in the ball park. Unfortunately, the ESC I had intended to use died without warning before I even had chance to fit the rotor blades! It had only been powered up to set up the radio gear and make sure the motor direction was correct, and then it just stopped working!
I had an old spare kicking around, but it was limited to 3S, so I couldn't try it with more power.
I ordered a new ESC (different brand!) and a new pulley to raise the gearing. These arrived a couple of days ago, and were promptly fitted! I also made a proper battery tray, as the original method didn't seem secure enough to me:
BattMount-2 by Peter Christy, on Flickr
BattMount-3 by Peter Christy, on Flickr
BattMount-4 by Peter Christy, on Flickr
I also replaced the paddles that came with the kit with ones from a much earlier Lark. The ones that came with the model were mismatched by over 2 Gms, and even after balancing caused quite a bit of vibration. The older ones were matched to better than 0.01 Gms, and run perfectly smoothly!
Today I test hopped it in the garden between showers. No video as I didn't want to get the camera wet, but on 4S it was airborne at less than half throttle, and running MUCH smoother!
I haven't let it get out of ground effect yet, as there isn't much space in the garden! It is also quite tricky to hold a heli in the hover until it has been properly trimmed - which requires being out of ground effect! Also, I've had the motor cut once, and hiccup a second time, for reasons that are unclear at the moment. Not sure if its a receiver issue or an ESC problem, like I had with the Cobra, so I'm being very cautious for the moment.
Anyway, its keeping me occupied during the lockdown! Next up is to electrify my DS-22.....!
--
Pete