Well it's been a few years since I've been here on EB, kind of had to set Lego aside for a while as I've been working my way through college and haven't had much free time for it. Lo and behold, I find myself quarantined for a bit and so I've broken back out an old project! I've had this gearbox sitting on my shelf for ages so I've revamped it and started planning for the rest of the helicopter.

RC Helicopter WIP by jwarner1718, on Flickr

This is basically all the gearing for the vast majority of the model. A lot of the old components have been carried over but I've optimized it for size and stability, plus reworked a lot of the gearing. The whole thing can be looked at as three separate parts: the gearbox (in blue), the swashplate/rotorhead (in green), and the switch box (in red).

RC Helicopter WIP by jwarner1718, on Flickr

The switch box is controlled with a servo motor and has three outputs; one engages or disengages the front and back mini LAs as a pair, the second controls the left/right pair, and the third determines whether the pairs move in sync or opposite to one another. Using some clever gearing (you can see a little bit of it below, I might do a video demonstration if anyone is interested) this results in three positions of the servo:

• left/right pair moving opposite, with the front/back disengaged (this is left/right cyclic, which controls the helicopter's roll or left/right movement)
• both pairs engaged, and moving in the same direction (collective pitch control, which controls the altitude of the helicopter)
• front/back pair moving opposite, with the left/right pair disengaged (front/back cyclic, which controls pitch and by extension forward/backward movement)

RC Helicopter WIP by jwarner1718, on Flickr

Between these three controls you can replicate any pitch control of an actual helicopter, though probably a fair bit slower an M motor controls the adjustment of the LAs, which in turn manipulate the swashplate which pitches the rotors accordingly. There's also an L motor to control the actual spin of the rotor which I may just hook straight up to the battery box and run constantly while the model is switched on. I don't own any of the RC PF stuff yet so that would save me a remote and an IR receiver. You can see the mounts for those two motors below; the M motor goes on the left and the L on the right.

RC Helicopter WIP by jwarner1718, on Flickr

And here's the full construction, with all the motors attached and my little space guy for scale.

RC Helicopter WIP by jwarner1718, on Flickr

It's a pretty big gearbox overall, in part due to the turntable piece I used for the swashplate which kind of determined the scale, but also just because it's a really complex mechanism. The plan right now is to sit the pilot and copilot seats on either side of the servo which should save some space and keep it from getting too too big. I haven't decided exactly what kind of helicopter I want to build yet but originally I had planned on basing it off the Black Hawk or one of it's non-military cousins. I'm really liking the color scheme of this S-70C Blue Hawk so that might be inspiration.

I'm not exactly sure what my next big milestone will be, I'll likely have to transition to Stud.io to design the fuselage since I probably don't have enough parts to build to whole thing here. And classes start up in less than two weeks so this may end up getting sidelined once again who knows? But for now I'm just excited to have done something with it and want to hear your thoughts!

I would be very interested to see how the switching mechanism works!  

Is the square formed with axle connectors strong enough to withstand the forces on it without pulling apart?

Very cool!

That's good a lot of appealing mechanical complexity going on!

Oh man I’ve been waiting for updates on this one for ages, so glad you’ve come back 

2 hours ago, Hrafn said:

I would be very interested to see how the switching mechanism works! 

I'm not exactly sure how to embed a video directly to EB but here is a quick demonstration. Really the most creative part was using the bar with towball piece inserted into a knob gear to alternate between rotating axles. The towballs are slightly smaller than the knobs so it's a bit finicky but it works well enough.

 

2 hours ago, Hrafn said:

Is the square formed with axle connectors strong enough to withstand the forces on it without pulling apart?

Don't be deceived, the foundation is made of liftarms so it holds just fine!

Edited August 8, 20213 yr by Milan
Edited to embed the video.

@jwarner to embed a video, just paste its link directly in your post.

@jwarner, thanks.  Try https://www.bricklink.com/v2/catalog/catalogitem.page?P=58176&name=Bar with Light Cover (Bulb) / Bionicle Barraki Eye&category=[Bar] instead of the bar with tow ball - I have found it fits much better with the knob wheels in applications like this.

Ya know I think I may have even bought a few of those for that purpose, I'll have to give them another try!

23 minutes ago, Milan said:

@jwarner to embed a video, just paste its link directly in your post.

Thank you! Will do this next t time for sure.

38 minutes ago, Bartybum said:

Oh man I’ve been waiting for updates on this one for ages, so glad you’ve come back 

Thanks that means a ton! I'm glad to be building again, for however long it lasts

Briljant. I saw this project before and i love to see it again.

So you’re building a mechanical CCPM system? 
Absolutely fantastic. I’ll be following this. 
And you’re putting it in a helicopter at that scale?? Even more fantastic!

I couldn't not comment on it 

I am quiet impressed by this approach and very curious to see it in action.

I must admit that it seems to me you didn't choice the easy way to acheive this, but why not?

Once you'll feel ready, a short video of the mixer in action would be appreciate.

Steph.

@steph77 Thank you! I've gotta order a few parts for the gearbox as well as the RC parts, that'll probably happen in the next few weeks so I'll definitely be uploading a demonstration after that. 

As far as my approach I wanted to commit to full RC control, while using as few motors as possible since I still like a mechanical challenge. That meant I needed a way to switch control between different functions while keeping the disengaged sections static. That plus the general slop in such a large gearbox led me to the LA approach since the incorporated worm gears eat up the slack pretty well, and hold position when disengaged. 

On 8/7/2021 at 6:25 PM, jwarner said:

Well it's been a few years since I've been here on EB, kind of had to set Lego aside for a while as I've been working my way through college and haven't had much free time for it. Lo and behold, I find myself quarantined for a bit and so I've broken back out an old project! I've had this gearbox sitting on my shelf for ages so I've revamped it and started planning for the rest of the helicopter.

I really like your design for a helicopter swashplate gearbox, and I am so inspired by this that it would be the perfect solution for controlling the rotors in my large hovercraft model. When you have the time, is there a chance you can release instructions or a video on how to construct the gearbox?

Edited October 7, 20213 yr by HydroWorld Outlook
Understood, Milan. I just did not know if I was allowed to modify that quote.

On 8/10/2021 at 11:29 AM, jwarner said:

@steph77 Thank you! I've gotta order a few parts for the gearbox as well as the RC parts, that'll probably happen in the next few weeks so I'll definitely be uploading a demonstration after that. 

As far as my approach I wanted to commit to full RC control, while using as few motors as possible since I still like a mechanical challenge. That meant I needed a way to switch control between different functions while keeping the disengaged sections static. That plus the general slop in such a large gearbox led me to the LA approach since the incorporated worm gears eat up the slack pretty well, and hold position when disengaged. 

If you would like your helicopter rotors to spin much faster, I strongly recommend using a Power Functions-compatible BuWizz motor to drive the axle that spins the rotor head. It would look a lot more realistic to the speed that a real helicopter rotor spins at, but hey, its just an idea.

Edited September 18, 20213 yr by HydroWorld Outlook

This is really cool! I like how you did the switch box