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polulo gearmotorsToday I'm going to start working on mounts for the motors so that I can attach them to the chassis (to be designed later). The motors I chose are three Pulolu's 30:1 37Dx52L mm Metal Gearmotors with 64 CPR Encoders. It's not likely I'll use the encoders, but I like having them there just in case I decide to. These guys run off 12V which I'll supply with a volt booster; however they do run pretty damn well on 9.6V (really 10V from my NIMH batteries). The torque on these things is great, almost so much that I can't stop them from spinning with my fingers.

So let's figure out how to make these as my first 3D Printed parts...

 

Alwamotor mount testingys be sure to test your motors when they arrive, because the first ones I bought (different brand and model) were rubbish. The gears were so tight up against the cover that the motor refused to spin very much or just not at all.

 

 

 

 

 

motor mount v1.0

motor dimensions

motor mount v1.1 testfitDesigning the CAD drawings for the motor mounts was pretty difficult as this is my first CAD drawing. Since it's also my first 3D printed practical parts I had a lot of trouble getting the screw holes to line up and to the ight size. Apparently plastic shrinks after you print it and not the same way horizontally and vertically. The picture furthest to the left is the first version to this mount after I had finally got the screw holes where I needed them. Fortunately I was able to get some good schematics on the motors.

A problem with this design is that I had problems putting the motor in with the top mounting plate not being open. This also created some overhangs that don't print well unless I print it vertically with the motor plate facing down.

 

motor mount v1.2

motor mount v1.2 testfitOn revision 2 I've fixed the problems I had and the motor fits in perfectly. I've also made some flanges to attach to the chassis. I've also added some holes for the bolts and impressions for the nuts. This worked out so well I decided to use nuts and bolts for all of the parts and try to avoid using solvent to weld things together. Everything will be modular. A thing I learned from Ben Heckendorn, don't build anything you can't take apart.

 

 

 

  

motor mount with motorNow with the final version with the flanges and mock-up motor in place. I'm very pleased with how version 1.2 worked out and after testing I did realize that the bolt holes have a bit too much tolerance so the bolts can wiggle just a bit. If its a problem later I'll have to design version 1.3.

 

 

 

 

 

 

Well that's all for now. Next on the agenda I need to build the lower tier of the chassis so the motors have a body to attach to.