Simchair MK III I2C twin throttle collective

by hc625ma Jan 5, 2018
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I would like to somehow integrate an actual idle-stop solenoid into the thing, any chance you can add some kind of mounting point for a small solenoid to the throttles?

Something like this https://www.adafruit.com/product/2776

Sadly don't have solidworks.

you can also do it with a 9g servo and a screw, easier to get and cheaper, 1 servo can be driven by the board directly without any extra stuff. If you have a good idea, draw it, it will help)

I've been thinking about it for a while, but it's not that easy to do (to integrate it into the lever frame properly, especially for a twin one) =) I think I will add it sooner or later, but can't tell you anything about when yet. Meanwhile, I can tell you the software version works quite good (there are only a few (if any at all) helis that actually support idle stop properly)


Thanks Alexey, that's great service.


There seems to be an STL missing from the single throttle package. The throttle_resistor_mount_v2 appears in the SLDPRT folder but not in the STL folder or am I missing something? There doesn't seem to be a way of mounting the pot.



Uploaded the file, check it out.

Oops, sorry for that Dave, will correct this in a couple hours, as soon as i will come home.

Hi planning on building the single throttle and am looking around for the parts. Having trouble finding 6x6x4 magnets, where did you get yours? Also does the decorative head fit the single throttle version, I intend adding a switchbox at some time?


Great design by the way!


Thanks for the quick response. Yeah I'll have to try a larger magnet, there are plenty to choose from! I watched your video too so I realise the decorative head won't fit the single throttle. Might have to build the dual instead.


A larger magnet can be a problem, but you can always glue it instead of fitting it to the socket. The only problem is you will have to find a good position for it, but I don't think you'll be having too many problems with it) The 5x5x4 magnet should fit without any modification. If you are satisfied with the 1st engine grip length of the dual throttle lever, you can just use its assembly and print a decorative cylinder instead of the second throttle grip. Also, please consider test printing a few parts at first (throttle grip frame and throttle) to check that they fit together correctly, you may have to adjust the clearance between them, this can be done by changing the printing speed if you don't want to mess with the model. I will make the single throttle version of the lever tomorrow if time permits)

Hi Dave and ty for your kind words!

I bought these magnets at a local store. You can try a 5x5x4 one that is widely available from china and tell me about your results! There shouldnt be too much difference, maybe it will require some calibration, but generally should work. The single throttle version is called a simple one for a reason- it has fewer parts and is a lot easier to build, but you cant fit the head on it. If you need it, i can make a single throttle version of the twin lever, shouldnt be too hard. But i wouldnt be able to test print it (i already have two of them lol). I have started working on wireless cyclic grip recently, the switchbox should follow shortly after)

This collective looks really cool. I'll make one once my printer upgrades are here...

I was thinking about the headbox/switchbox. I would add an additional micro controller in that box which communicates via I2C to the base. Thus only a few additional wires need to be passed through the handle. Further I would investigate the possibility to use some standard audio connectors (or similar) to make the heads exchangeable. Then one could use different heads for different helos...

Thank you for your kind words!

Yup, I am going to design one, as soon as I will have enough time and inspiration to do it) I was thinking about making the switchbox wireless with some popular radio interface, and to try to source power from AA batteries (Should yet experiment with this as I have no idea how long batteries will last). As things look now, a button controller will probably be a separate one (I believe an analog controller should do as much filtering as possible (without adding too much delay) to reduce sensor noise) Also, I am thinking of changing controller interfaces to i2c and using 14bit external ADCs (it isn't that necessary for the collective, but will be good for the cyclic). This will add a bit of extra cost, but in the long run, it will allow for wide range of devices to be connected without any need for hardware changes.

In my other projects I'm using a 12bit ADC with a I2C interface which talks to an Arudino Pro Micro connected as a HID joystick to the computer. Works really good... Got those ADCs quite cheap from China...
For my purpose I think a KA50 style button box would be sufficient...

However, I prefer a cable-based solution, too afraid that it powers down during a session :-D.

I just ordered a set of missing bearings for the collective :-)

I like cable-based solutions too, it's just hard enough to route wires through the 60-degree triangle of a limited height) Also, it's hard to make heads interchangeable while not having any wires or connectors on the outside of the lever. Well, in the worst case, the cable can always be hung under it)

I didn't print that handle, so I don't know how tight it is. However, a hanging cable is ok. Or one add some kind of 'protection rail' to hide the cable inside, like this one here: http://oh1ninja.la.coocan.jp/details/EC135/EC135_CP.jpg

Btw, consider printing a few test parts at first to check how they fit each other, every printer is a bit different, you may need to adjust the clearance between parts. The trickiest parts are probably throttle frames. Or you can try adjusting the clearance by changing printing speed, looks like faster speed = tighter fit.

Yes, if the printer head moves faster it may move a bit too far and thus the print size may vary...
I'm still waiting for a few upgrade parts of my printer... After that I'll print the collective. Currently I'm more into the fast movers :-D

Yup, it's quite a popular design) Well, I don't think there will be any problems with this approach, i2c is only 2 extra wires, you can use spare pins of the RJ-45 connector for that)

Yes, that's the nice thing about I2C :-)

OUTSTANDING a MUSTHAVE for any serious bell trident or BK117 flyer cant wait for the Cyclic