"One Perfect Part at a Time"

Machining Job for Roboboat

I just ordered a couple (2) 6-18 Volt Johnson 9167AK electric motors for the Roboboat project. I do not yet know if they are suitable. I’ll discover that once I receive them. This is part of the problem when buying something you can’t first touch and feel. Especially if it something you have never owned in the past.

The specifications seem to be OK and the cost was very low (about $7.00 each on eBay) so I figured it was worth the risk. That is all part of the cost when creating a prototype. If anything the motor’s physical size is what has me concerned. They just don’t seem to be big enough for the power they can handle. That is about 49 watts each. They weigh in at .45 pounds each so they seem to have some mass.

Johnson makes or sells a huge variety of small DC motors. These motors I picked are not the highest RPM but do have a lot of torque for their size. I also have to pay attention to the power they use as I don’t want to haul around large expensive batteries. I then also have to stay within the ratings for my speed controllers.

The reason I am posting this here is that part of my plan is to design and build (machine)suitable aluminium motor mounts for these (or any) electric motor I choose. High power also equals high heat so I need to design for the heat these motors are sure to produce. Of course I don’t expect to be running the motors at full power. (I could be wrong.) A lot will depend on prop size and pitch. Lots of variables.

The roboboat project is not intended to produce a high powered fast competition model boat. I am expecting scale like operation. At 1/16 the size of the original, the scale speed will also be 1/16. If the prototype ran at 48 MPH then the model only needs to run at 3 MPH actual to cover the scale distance. That’s a little less than walking speed. I am assuming the model will actually be able to run much faster than that.


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