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Motor mounts and bearing blocks for things that move

When building or customizing robots, motorcycles, go-karts, electric vehicles, conveyor belt systems, or just about anything that moves, you will eventually run into the problem of having to tie all of the motion components together into a single system. If off the shelf components don't meet your needs, you can waterjet cut custom frames, motor mounts, and bearing blocks.

Let me show you an example from my fighting robot “Jaws”. I needed a bearing block which would give maximum support to the wheels, but would occupy a minimum amount of space and weight. The solution I came up up with was a ¾ inch thick 6061 aluminum bearing block with a bronze bushing inserted into it. Using a bronze bushing kept the size down compared to using ball bearings.

After the bearing blocks were waterjet cut, I drilled holes in the edge of the bearing blocks in order to base mount to mount them. The bearing blocks rest on their cut edge and are held in place with bolts and nuts. Below you can see a rendering of the part, and a photo showing it installed inside the robot.



Illustration : Rendering of the 3/4 inch thick aluminum bearing block from Jaws.


Illustration : The bearing block installed inside Jaws.


Note that if you are base mounting this type of bearing block (mounting along the cut edge),  you will want to use low-taper waterjet cutting in order to keep your driveline straight. For face mounting, you might be able to get away with using regular cutting if you can drill or ream the hole where the shaft passes through in order to give it an even diameter all the way through the material.

Now let's take a look at a different bearing block system, this one from MattyCiii of the Endless Sphere Technology forums. He needed a special bearing block for a custom electric bicycle he was building for himself. He designed a bearing block to be made in two pieces, each 0.625 inches thick. When stacked together, they are exactly the width of the 1.25 inch thick tube that they mount to. An aluminum tube fits in the large hole in the blocks, and a ball bearing fits inside that, which supports the shaft. You may notice that there is a small gap at the bottom of the bearing blocks. According to MattyCiii, this allows the bearing block to grip the aluminum tube tightly when the bearing block is clamped in place. Here is how he describes how it works:

The gripping capability is actually a combination of two things: First the gap, and second, the flat plane you see on either side of the gap is not fully flat – it’s angled in slightly. So take for example that last picture: imagine only one of the hose clamps is clamped down tight. There would be about about a 1 degree angle between the other flat part of the mount and the square tube it’s mounted on. As you tighten the second hose clamp, it pulls the piece tight against the flat and slightly shrinks the diameter of the hole. I’m not an engineer by trade, I didn’t do any calculations to find a ‘best’ angle for this purpose – but it works as designed (miraculously!)



Illustration : A stacked bearing block before mounting. Photo courtesy of
MattyCiii from .



Illustration : The bearing block from the previous photo mounted in
place on the electric bike. Photo courtesy of MattyCiii from .



When building things that move using a waterjet, you're not limited to just bearing blocks. One common problem faced when building an electric vehicle is mounting the motor to an existing frame. Waterjet cutting allows you to easily make custom motor mount plates that match the bolt pattern on the motor, as well as the mounting points on the frame.

Here is a great example from Roberto Melendez of MIT. In building the Cholocycle electric motorcycle, they needed a way to mount their 25 horsepower electric motor to a Kawasaki motorcycle frame. With waterjet cutting, they were able to construct mounting plates which fit both the motor and the frame perfectly.




Illustration : The waterjet cut motor mount attached to the front of the electric motor
for the Cholocycle. Note the rear mount disassembled in the background.
Photo courtesy of Robert Melendez .




Illustration : The motor installed on the Cholocycle motorcycle frame.
Photo courtesy of Robert Melendez .

Now let's take a look at an assembly of waterjet cut parts that combines a motor mount with bearing blocks. For the LOLrioKart project, Charles Guan wanted to add a powerful electric motor to a shopping cart (yes, really). In order to do this, he needed a way to attach the motor to the frame, as well as a way to hold it in line with the driven axle. His solution was to use the waterjet to make a combination motor mount and bearing block out of ½ inch thick aluminum 6061. He used the stacking technique to make the plates thicker and thus provide a more stable attachment where the assembly rests on the cross member tube. You can see the separate pieces as well as the assembled drivetrain below.



Illustration : 1/2″ 6061 aluminum plates and motor for the LOLrioKart drive
train. Photo courtesy of Charles Guan



Illustration : The assembled LOLrioKart drive train.
Photo courtesy of Charles Guan