Throttle Quadrant

On internet many DIY-projects can be found for building a Boeing 737 Throttle Quadrant.
Most of them use a sandwich construction of 11 wooden plates connected with 8 mm full threaded rods.
The throttle, flaps and speedbrake handles rotate around a central rod and switches and potentiometers are attached to the wooden plates.


When checking one of these TQ projects on I noticed that the design of the plates could be requested as a DWG file.
Using the DWG to DXF converter on I had this converted to a DXF file so that I could open and modify it in Inkscape.

For the wooden plates I purchased a 244 cm x 122 cm x 6 mm MDF plate and had it sawn in 29 cm wide strips that nicely fit on my CNC router table.
In Inkscape I had to do some processing of the converted DXF design so that Estlcam was able to trace the outlines of the panels (no gaps) and create G-code for each panel so that it could be milled with the CNC router.


As I don’t have a lathe I purchased a complete set of knobs for all levers at (‘Boeing 737 Throttle full handle set’)
These knobs appeared to be solid, so I’ve used the CNC router to make holes in the throttle knobs to fit the pushbuttons for the autothrottle disengage function.

Also I modified the design of one of the throttle handle plates a bit so that it better matches the notch in the knob.

Many throttle quadrant projects found on the internet are ‘passive’ implementations, that is, they’re not motorized.
I’d like to have the levers moved automatically by the autothrottle however.

After some more searching on the internet I found a very instructive YouTube channel ‘Buildaboeing‘.
A couple of the videos on this channel show various aspects of the construction of a motorized throttle quadrant using servos.
Most important difference with many other DIY throttle quadrant implementations is that all functions are motorized: not only the throttle handles and stab trim wheels, but also the speedbrake, parking brake and stab trim indicators.

There are some cockpit builders that have created very realistic implementations for the throttle handles with motors and a clutch so that even under autothrottle control the handles can be manually overridden, but these are expensive solutions. I decided for the somewhat less realistic, but cheaper implementation with servo motors as seen in the Buildaboeing videos.

Another difference with other projects is that instead of ‘normal’ potentiometers driven by gears Peter from Buildaboeing uses sliding potentiometers moved via levers by the throttle handles.
Instead of two microswitches at the outer limits of the reverse thrust handle paths he used potentiometers with gears: according to him this more closely resembles the original reverse thrust handles: when moving them they only trigger after halve of the rotation.


Something he mentions in one of his videos but didn’t implement is that the reverse thrust handles in real life can only be moved when the throttle handles are in idle mode.
It was an interesting challenge to see if I could find a solution to add this to my implementation.

For driving the trim wheels I used a solution with bike chains as found in some other implementations. I want to use cheap derailleur jockey wheels that can be bought at Aliexpress for just over a euro a piece.
I spent some time finding suitable, small and narrow enough chain tensioner wheels. Until I read the annotations on the pictures in the document ‘How to build a B-737 300/800 throttle quadrant’ by Francisco Gago of February 2004 where I found that the ‘K’NEX Hub/Pulley Medium‘ is very suitable for this.




trim wheel


Fuel cutoff handle with two microswitches




Interesting links:
Youtube kanaal Buildaboeing

13 thoughts on “Throttle Quadrant

    1. Hi Quinn,
      I’ve tried to forward the Inkscape design files for the throttle quadrant to you, but get a message that your e-mail address doesn’t exist?


      1. I can send you what I currently have, but it’s still ‘work in progress’ which has not been cleaned up yet for public release and may be subject to changes, depending on the outcome of my tests.
        Unfortunately the electromagnetic clutches that it is based on are not for sale anymore where I bought them. The alternative ones that I mentioned in one of my blogs seem a good replacement, but may require some modification of the panels in which they are mounted and I have not yet tested them.


      2. Hmm, I thought I already mentioned the possible alternative for the clutches in one of my blogs, but it seems I haven’t yet.
        Here is a side-by-side comparison of the bigger clutch that I have now and the possible alternative:
        Original (big) and possible alternative clutch
        But note that I haven’t tested it yet. It has the same D-axis and gear size/nr of teeth as the original one though.
        Here is a link where the alternative ones are still for sale.


  1. Hi

    What a brilliant site, thank you for all the info.

    I’m looking into making a throttle, I have a small 6040 Chinese cnc machine where I use Mach3 as the software to run the cnc. For the drawings I use Vectric software.

    Are you able to share your plans for the TQ?

    Best regards



    1. Hi George,
      Currently I have most of the 2D drawings in Inkscape (SVG format), but they need to be cleaned up because they contain various things that I have tried.
      To streamline that cleanup I’m working on a Sketchup 3D model that only contains the parts that I have really used, shows how everything fits together and allows to export individual parts to STL or DXF format. Unfortunately it’s not completely finished yet: in parallel I’m working on a PCB design for the TQ that connects all the electric components with an Arduino and to make the PCB ‘future proof’ I also want to support alternatives for the servos, so I’m testing and including optional drivers for DC and stepper motors, although it may be a challenge to fit those in the same limited space. I have a small stepper motor that would fit, but want to test if it has enough torque to move the handles.
      The current status of the Sketchup Make 2016 3D model can be downloaded here:
      The latest free version of Sketchup is web only, but the free 2017 Make version still can be downloaded from and allows importing of the above 2016 model.


    1. Hi, I’m afraid I’ve never been able to correctly print to scale from Sketchup on a single page so far: it always creates multiple pages with the model in the middle of them.


  2. Files won’t download. Could you send them to me please. Fantastic project. I am working on one that I printed but need help trying to figure out how to wire everything. It’s a 737 file for printing. I have almost 90 hrs. In print time and still printing.
    If you could possibly help me I would appreciate your time.


    1. Hi Randy,
      Which files did you try to download?
      I’m storing all my designs on Google Drive and use public download links to that because it offers revision control, otherwise I completely loose track of the large number of files and updates. Similar to ZIBO.

      I have no idea how the throttle design that you downloaded works, so it’s a bit difficult to tell how it should be wired. Doesn’t the author of it have any documentation?
      Also for my own throttle design I still need to figure that out. I’m working on a PCB design for it because there are so many connections to make, but I first need to finish the other electronics because I promised that to some other builders that use my radio designs.
      Too much to do, too little time 🙁



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