Testing 3D Printed Stackable Gearbox

The modular design is great - even for repairs. But the forces increase with each stage, so the size of each stage should increase, too. i.e. the planet carrier on the last stage could be bigger and stronger. I could see your design getting used IRL. Obviously you are a mechanical engineer.

One pretty easy and cheap way to increase strength around where bolts are mounted in 3d prints is to add metal washers imbedded into the print, it helps spread a lot of the load out across more distance and gives a strong metal back.

Planetary gears need to run on a through shaft to a backing plate. By constraining the shaft on both sides you will reduce the lever action on the carrier plate. Longer gears will just make this worse. as you will be increasing the lever length.

A double sided carrier near the output might help. Also as others have said, longer planets and even potentially a larger pitch ring gear/planets.

This was so taking me back to my previous work as a mechanic for Barloworld, South Africa's CAT dealer. We have had so many failures in planetary systems that i cannot even tell you how many. I think that you are on the right track with identifying the output carrier as your weakest member so trt printing it in the strongest material that you have available. This will unfortunately lead to the next weakest item failing and so on. The idea here is to place a limit on the amount of torque that you want to have go through your planetary reduction drive as you can keep over engineering all the items ad infinitum and never reach a point where you are satisficed. If you look at your different CAT machines using planetary reductions, they are all designed and sold in different size and application markets, from handyman to relocating mountains. I really hope this helps as I am just a retired earthmoving mechanic on medical pension. Pieter (Pete)

You can get those same battery connectors in "anti-spark". They have a built in resistor. Saves the arc damage on the connector and is less stressful to the ESC. I love these gearboxes. Awesome work.

It would be interesting to see it printed in nylon, preferably with glass or carbon fibre to reinforce it. Also it should be printed at 100 % infill. With the nylon you could test it just after printing but also after letting it absorb moisture from the air to see which is stronger. Heat set inserts are great, I am surprised they aren’t more common, they are so easy to insert and they are pretty strong, but it seems a lot of people don’t like them or are scared of using them. I was printing the matterhackers E3D V6 mount and found one that didn’t use threaded inserts and it required very specific nut shapes and sizes to insert and specific length bolts, whereas the matterhackers one that needed heat set inserts was very easy to put together and just used the inserts I had anyway.

Cool video. I think one of the easiest improvements is turning the carrier into a cage like design so the planets shaft is supported on both sides.

One thing I noticed was that the planet gears spun concerning the carrier. This is indicating that there is too much force on one side of the planet gear for the carrier to handle. Putting another carrier on the other side would not induce a force on that side to help but may distribute the offset across the planets. Further, there should be enough room between the planet gears for the carriers on either side of the planet gears to be connected. The force could then be given to the planet gears from carriers on both sides and reduce the incorrectness of the torques on the planet gears.

I haven’t gone through all your videos so I’m sure you’ve done this before, but I would love to see you do pre-test analysis to predict failure. I think it would be a great learning experience to see how systems are modeled and remodeled iteratively to match empirical or experimental results. Great video, Mike!

Very entertaining thank you. I’m learning so much from your projects. On strength in plastics, it’s generally good practice to design out stress with radii and chamfers, especially for structural loading. The bigger the radius, the better distribution and transfer of stresses - minimise notch fractures.

One word, genius 👏 Very interested to see how this plays out!

Im extremely excited for the next video!

make that gears and carriers longer the more torque that are applied to them. First stage 1x, second stage 1.4x, 3rd is 2.2x, last of the four is 5x long

You know how I know you're a good person? Step files. Bravo.

Thank you for CAD and STL files.

Amazing design!

100% infill with Nylon or Nylon with carbon fiber content. Or with more classical materials: print a positive on the resin printer, make a negative from silicone, and cast a positive from polyurethane resin.

Heat set threaded inserts changed my life and the way I design prototypes man. Also, barrier to entry for CNC milling is pretty low. (Relatively, I have a CNC machine shop already) You can get a genmitsu pro for pretty cheap and with some mods to the backlash nuts it will most certainly machine aluminum. You can also solid print the bearing backings combined with the housing to give extra support to the pinions.

As far as improving the planet carrier, one thing that can be learned from impact drivers is that they capture the planet gear pin on both sides; What that means is that there is a second plate with a hole in the middle that restricts the movement on the ends of the pins, stopping them from twisting side to side. Usually the carrier is made from a single solid piece, which should not too difficult to 3d print.