application
Johnson Motors
I am not sure if these motors are keepers yet. Well, I will keep them but not sure if they will get installed in this project. The specifications seem good (see below) but the motors, well… they seem so small. I did find some two inch diameter motors but I don’t think they are as plentiful as these Johnson brand motors. The price for the two Johnson’s was about $7.00 each. I have seen a conflicting price on the larger motors but all I see now is about $10.00. At that price it is worth experimenting .
I purchased these Johnson 9167AK from a seller on Ebay. There are quite a few sellers with this motor so it must be widely available. I didn’t see it listed under this number on the Johnson Motor web site. I assume it may be some kind of overstock for someone needing a small motor of these specification.
Johnson Electric 12VDC Motor (6 to 18V) – Model 9167AK
Extreme Torque of 2.2 in-lbs
Super Grip Serrated Shaft
This motor is quite a bit larger than most hobby types. It’s suitable for any model or experimental use where high shaft power and torque are needed. Please note that there are a couple of different Johnson model 9167 motors. The 9167AK is the biggest one with the highest power.
Runs very smoothly over the range of 3VDC to 18VDC.
Light load Medium Load Heavy Load
3VDC: 1,400 RPM 850 RPM n/a
6VDC: 3,150 RPM 2,100 RPM 750 RPM
12VDC: 6,560 RPM 4,900 RPM 3,400 RPM
18VDC: 9,800 RPM 7,350 RPM 5,100 RPM
At 12VDC the motor has very impressive torque.
Starting torque is 2570 gm-cm = 36 oz-in = 2.2 inch-pounds, at 14 amps.
Operating torque at medium load is 440 gm-cm = 6.1 oz-in at 2.8 amps.
As the load is increased, the torque and current will increase correspondingly. Please check that the case temperature stays below about 100 deg C, in order to maintain long life.
On a dynamometer, the motor was able to generate a continuous 31 watts of mechanical shaft power, with a peak value of 46 watts (temperature limited). A typical small hobby motor can only produce 2-3 watts and a medium-size motor about 10-12 watts, usually not continuously.
Overall length is 3-1/2″ including terminals and shaft.
The body is 2-5/8″ long, 1-1/2″ diameter. Or 65 mm by 38 mm if you prefer metric.
The shaft is 3/4″ long. It’s 1/8″ (.125″) dia with a .130″ serrated end section that grips tightly to a suitable hub, pulley or shaft coupler.
The heavy duty self-aligning front and rear bearings are lifetime lubricated oilite bronze.
The brushes are low-friction and long-life graphite carbon, NOT just copper spring arms as in many small motors.
The armature is 5 pole and the spin is reversible by reversing the power wires.
Early Boat Thoughts
Now that I have been working with the proposed control system I realize the subject boat (to be controlled) does not have to be as big as I first envisioned. The first tests will be remote basic control. Just taking control response and range into consideration.
To me that indicates I can run early tests on a smaller and cheaper to build model boat. The smaller size will also mean a smaller single motor will be needed. Less battery size will also be a benefit.
For these reasons, I am considering downsizing my first vision of the model boat required. This change justifies my plan to start with the control system first. I am learning what I need as I go. I am not sure when I will be able to commit to the actual boat selection.
At first I was thinking the bigger the model the better. Still a good plan but a lot more cost than needed for an untested communication system. I was thinking of about a 48+ inch length and a 10-12 inch beam. Now I am considering 24-36 inch length and as wide a beam I can find for stability (and space to work)
If plans go astray, I will have less invested in this experiment. My biggest concern is the reliability of the wireless network. I will spend a lot of time testing that before I have to figure out how to put it in the boat.
The second concern is water proofing. I have built model boats and know I have to seal the electronics from the moisture. I am using an experiment board for now. Next step for installation in the boat will be a prototype board. This will provide permanently soldered components and connections. It will also be larger than a custom designed circuit. I do not know exactly what size the prototype board will be. I have a general idea from the boards I know that are available. So that is why I think I can downsize the model.
The truth I have considered is the first test vessel can be a very simple and crude “pointy box” with a motor and rudder. Ugly yes, but a consideration. I’d rather have a scale model looking test bed for the pictures, but I can be practical if I want or need to be.
When I get to GPS and other enhancements, then I will have to go to a larger test platform. Perhaps then I will include dual motor controls. Fun to think about but first things first.
I’m a Hack
I am starting to think of how many ways I can use the micro computers in monitoring and control situations. They can be set up to have their own network IP address and webpage, at least on the home network. It’s called the Spinneret Web Server. Not sure that I would want to make my data available to the world, at least not at this time.
There are just so many wonderful options that these controls can be set up to manage. I’m sure there is a business opportunity somewhere in designing and deploying these devices. I certainly will be finding and deploying my own beyond the RoboBoat Project.
I have returned to my first love of working with computer CPU’s (Central Processing Units). Back when I started there was nothing but assembly. I was working in machine language just trying to make LEDs blink in sequence. Much later on I was writing ham radio terminal programs in MS Basic on the Apple MAC computer. Getting the random serial streams to decode and display properly (using BASIC) was a real challenge. Somehow I got it working very well.
I enjoyed writing computer code for the control system (I/Net) that my real job (office building control systems) allowed. I became involved just as the code writing was evolving from the DOS environment into a higher generation language. Most of the “old boys” didn’t trust the new interpreters. They wanted to stick with DOS. Ha! I had to learn both methods.
I enjoy the process of writing code that works closely with the fundamental CPU process of the computer. I like it more than running a computer application. However, I can live just fine with the simple BASIC interpreters of these computers. Some machine level code (assembly) can be written to speed certain operations. Dedicated hackers (good hackers) can write their entire program in assembly if they desired. Not me, I’ll just give it a poke when I have to. Assembly is just TOO much detail.
The higher power Propeller computer uses a language called SPIN. But that system also recommends Assembly when needed for speed. There are lots of options to fit any need. I love it!
Heck, I may never get the boat built. Not true, I am on a mission there. I’d love to have the boat running simply as the reason to experiment with the programming. And also have something truly unique with which almost no one else is experimenting.
Stand back! You may get injured in all the hacking going on.