3D Printed Stackable BRUSHLESS Motor Gearbox

This video was sponsored by Brilliant

Thank you for watching the video! Links to the CAD for this project are below as well as links to the hardware needed to assemble it.

CAD Files:

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Hardware List (Affiliate Links):

Small addendum to the video. The final torque value I gave was correct but the values shown on screen were wrong. The load cell was measuring weight so the maximum weight seen was about 9500g not newtons. Sorry about that.

Links to stuff I use (affiliate links):

[tHaHxr]

The problem with your torque measurement now, is that because of the high velocity you are coupling a significant amount of intertia. The motor inertia might seem very small, but because of the gearbox it is amplifier by n^2. None of the cheap brushless motors actually quote rotor inertia, but generally its somewhere around 30 gcm^2. That means that with your 64x reduction gearbox, you are dealing with an inertia at the output of about 0.0123 kgm^2 (note the change in units). Guesstimating the speed of the output shaft, its probably around 0.3 rotations per second, 1.9 rad/s. This results in an angular kinetic energy of approximately 0.0217 J. Thats quite a lot of energy stored, especially if you want to try to slow it down in a very short period of time. Point being is that you are generally measuring much more than just gearbox output torque.

Torque testing should indeed be done at zero speed.

Also, are you aware that there are specially wound BLDC motors meant for slow speed operation? These quadcopter motors are optimized to work in a constant high velocity, but the ones optimized for slow speed are much more well suited for most robotic and servo tasks. You can easily find relatively cheap ones if you search for 'gimball BLDC' and similar search terms.

[SuperMakeSomething]

Really cool design, thanks for sharing! If it is accurate, that amount of torque out of a 3D printed gearbox is wild. +1 for adding an encoder for better low-speed control.

[DanielLarby]

As you have concluded, measuring torque while using an ESC won't really tell you much.

There are some very nice alternatives to ODrive now that would work well with the size of motor you have.

In particular: the Tinymovr (R5) and Moteus controllers. They are much smaller than an ODrive, come with the encoder built in, and mount directly behind the motor.

[navid]

Great design. You are measuring 9500N of force by the load cell however, your load cell has a max capacity of 200N!

[nerdmanufactory]

You could try testing how much weight the gear box will lift at given ratios. Knowing that would help determine what kinds of applications you might be able to build this into. Long Term speed test for heat and wear would be good too.

[elQuestionare]

Why do people who use 3d prints often dont use any oil or lube for gears? I see it so often that they push bone dry gears together. But respect for the build!

[OMGWTFBBQSHEEP]

This gearbox is one of the better ones i've seen on YT! Good job. Btw since you can't do a static torque test, it would be nice to see what weight it could lift at a given radius. For example, build a simple drum with 50mm radius with a string attatched to some weights. Then you could try different weights and speeds.

Also, this would enable dynamic endurance testing which would be really interesting to see.

And, maybe even try different filaments. Maybe nylon or petg as gears?

[aterxter]

The major blunder in the test comes from the fact that when the shaft is stopped in the load cell, the motor stops, thus we don't det the stall torque but instead the torque necessary to annihilate the angular momentum of the motor's hub, shft, planets holders, planetary geers, ... everything that spins gets some angular momentum to annihilate with a counter torque if you want it to stop

[goldenpiston]

Brushless motors do not normally actually have a sine-wave drive. It's actually more efficient to use a trapezoidal wave, and hence what most ESC's use.

[nicholesward]

Do a weight test with the motor, like put a pulley on the end of the motor and a string/wire and keep adding weight until something fails.

[natescott]

That 3d printer is amazing. I've never seen print quality/ such a small bead from the nozzle in a hobbyist's printer.

[yashmokashi]

What I find most impressive about this quadcopter is the potential it has for DIY enthusiasts and makers. With the ability to design and print your own quadcopter without having to purchase expensive parts, it opens up a whole new world of possibilities for those interested in robotics, engineering, and design.

[hernancurras]

Amazing project, you tested, you printed, and posted the step files. Is a proof that you really know what are you doing. I enjoy your engineering projects. I will use this gearbox as a sailwinch for my rc-sailboat. Let's close loop this marvel.

[murman]

A quick way to electronically reduce the speed and increase your motor's torque is to desolder the connectioms to the three phases ( at the stator) and rewire them in a wye configuration if they are currently wired as delta. This will cause current to enter one phase and be forced to energize an additional coil on its way back out of the motor. The scope of this mod is to reconfigure the phase connections from parallel to series. The motor will have more energized coils at any given moment, thus increasing its torque. I've used this trick before with good success and my motors live longer and run cooler. Keep in mind that you will decrease the maximum speed. That is the tradeoff.

[Term]

Wow, thanks. One or two weeks ago I designed planetary gearbox for 5010 myself but I didn't get to assembly. It's nice to come across same idea, u saved me couple of hours of tweaking. Thumbs up!

[mikestewart]

The Jim Lahey clip earned my subscription Sir. 👍

[MDalton]

This is really cool design. Prints pretty easy too. Fantastic work.

[StephenGillie]

Planetary gearsets are 3-way adapters for gears. This design uses 1 of them as housing, and the other 2 change ratios like a car transmission. An old-fashioned manual transmission could do this more simply, or an Allison transmission is more elegant. Or add another motor (it can generate too, right?) and just 1 planetary gearset and you have a hybrid transmission. All 3 of those are modular designed to change while the vehicle is in motion, without having to stop and bolt in other parts. But this is a good learning exhibition - a launchpad to talk about transmission designs. Thank you for making the video.

[cn-ml]

Thats a really cool design, the rotating planet core that is just one free spinning stack of gears is quite fascinating. -1 for the torque test, because the peak is highly influenced by the inertia

[Henning_S.]

Just mount the arm with the load cell to the gearbox case and mount a longer shaft to the output shaft, so you can grab it with a glove to apply a breaking force to the output shaft. Now you can do continuous torque measurements at different rpm's without the influence of inertia!