![emot-4.jpg](https://modelboatblog.tedatum.com/wp-content/gallery/jmotors/emot-4.jpg "The shaft is a rather small 1/8\\" diameter. There are splines to help hold whatever is installed on the shaft.")
propeller cpu
Motor Mount Ideas
I have a machine shop and engineering project for the Dauntless boat project.
I have done a fair amount of research on the motor mount of scale model boats that use electric motors. One thing that totally astonishes me is the casual use of cheap universal or “ball” joint between the motor and the drive shaft. What is typically displayed in the Dumas (boat kit manufacture) and other brands is a fairly noticeable angle between the motor and the drive shaft. Many times a crude plastic “dog-bone” connector is in use between the yokes.
Of course I have seen a lot of very good installs. The racers usually have found out the secret to best running is with straight shaft alignment. The modeler shouldn’t always follow prototype with a waterline level engine mount fastened to an angled drive shaft. Even if there are quality parts available to do it.
This is not a problem for an automobile and other low RPM drive-shafts that have no slop roller bearings built into the cross and yoke design. In my experience and opinion, slop is one heck of a problem for very high speed drives like are used in fast running model boats. I am talking 5000 to 10,000+ RPM. Would anyone build and run a dragster with the bearings removed from the U-Joint? Model boat builders seem to do it all the time. This is where a lot of the vibration noise is coming from.
I have installed hundreds of powerful motor and pump systems in commercial central plant HVAC system with a precision drive coupling between the pump and the motor. There are especially trained technicians with very expensive test equipment who do the alignment job correctly. For highest efficiency and lowest wear and noise (power loss) the two shafts and the coupling must be perfectly aligned. I believe no less care should be taken with the high RPM model boat drive line.
Yes, the quality model u-joints are made for a small angle but it is probably not wise to run anything more than a few 1000 RPM for short periods with that set-up.
So my design goal is to build a motor mount system with coupling and engine room drive shaft alignment built in. This includes the HQ stuffing tube mount through the hull. The prop end mount will have to be carefully designed if the boat design requires an exceptionally long drive shaft. I may even use ball bearings on the shaft and stuffing tube if I can figure a way to do it. However, I have read that BB’s are somewhat overkill as flanged Oilite bearings work great and are easy to replace.
A lot of time getting this part of the build right will pay big dividends when running out on the pond. I have read a lot of stories where the motor was installed (for the first time) the night before the big outing with a couple of straps to hull blocks and the u-joint expected to take care of all the alignment.
That’s not for me.
The XBee Meets the Propeller
I got some time this Labor Day weekend (2011) to get an XBee interfaced with the Propeller processor. The pictures show the tiny interface board required to change the pin spacing from the XBee to fit the spacing on the Prototype Breadboard. This is some more of the micro soldering I have written about before. That’s all this board does is change the pin spacing.
What I can see here is the XBee running in full duplex. That means it can listen and talk at the same time. Just like talking on the telephone. Well, maybe I can’t do that but the telephone does it very well. 🙂 That’s a pretty big deal in the world of communication and has certainly removed some concern from me determining if this system will work fast enough for good control. I think that is not an issue at all now that I can use the Propeller.
Dedicating one of the cogs (processors) in the Propeller to just manage the communications means I can do whatever else necessary with the other cogs and not slow down the two way communications with the shore unit.
Hot Props
The Texas heat is killing me in the unconditioned shop. It is keeping me away from experimenting with the Xbee and the Parallax Propeller (computer). The inside temperature in the garage shop has been hovering at 100 degrees while the outdoor has been 105 to 107.
This is NOT for a few days mind you. We have been getting this temperature every single day for over two months steady. Yes, every day.
My new shop fan helps a lot at 80 or 90 degrees but near 100 or over it is just like sitting in a blowtorch. No fun. I tough it out in the morning (on weekends) for a few hours but by 10:00 or 11:00 AM, it’s breaking over 100 again.
Actually the little control computers don’t mind this kind of heat. They are very low powered so don’t generate much heat on their own. It depends on how much power you pull from them. I can’t say that about the PC computer that I use to write the application software. I believe it is maxed out with 105 degree ambient air temp trying to cool the processor, hard drive and other PC components. I had one of my CNC computers (another machine) shut down from the heat after running almost four hours. Luckily I had just finished the part I was cutting and was bringing the HB2 back to home position. I don’t do long CNC runs anymore in a hundred degree shop.
I like the newer Propeller processor. With 8 processors or “cogs” it is a “hot” multitasking little controller. That is figuratively hot. Not environmentally hot. I definitely have it earmarked to be the processor on the boat end. I was thinking about it today, and I am going to also use it on the shore terminal.
I don’t think I need its multi cog power on the shore unit but my thinking is to keep the software programming the same “flavor” for the entire project. I can put the BS2 STAMP to other uses.
I have a few ideas how to design the shore transceiver. It will be a small standalone unit. I was originally thinking of using a PC or Net Book as the shore terminal with just an XBee for the communication. The more I thought I decided a control box would be a better interface and not so expensive (to fix) when getting too close to the water, if you catch my drift. A BS2 would be plenty of computer smarts to run things but as I said above, I’m going to opt for another Propeller.
But hey! Who says I can’t play with my options.
With the Propellers at both ends of the communications I can dedicate one or more cogs in each Propeller to just run the XBees at their best transmission rates. Decision made.
If the Texas heat takes a few days off over the holiday weekend, I plan to get a lot more done with testing the com link. Then I can start designing the Propeller proto boards for the real link.
I also discovered there is a new Propeller multicore processor in the works. It will be bigger and hotter that the present Propeller. But hotter will also be the heat it generates. I suspect it will be more useful in applications where enough “shore” power is available and chip temps can be controlled. I think the Parallax Propeller has a great future and will be useful for a long time.
The Propeller
I can say the Propeller is on the bench. But not the one that spins in the water. This is the Propeller that will serve as the brains of the project. The Parallax Propeller computer chip is actually the larger (.9 x.9 inch) chip near the top of the blue circuit board.
This is a kit for learning how to program and use the Propeller. I am 95% certain it won’t be the same propeller I will use in the actual project. (I’ll buy another, they’re not very costly.) The red and black wires you see on the board, I have just installed. They serve as the “basic wiring” to energize the Propeller on the test board. They are now a permanent requirement for the set-up to power up the processor. You can see the wiring on the box lid.
The USB connection is needed only to program the computer or read text as output in the debug mode. The 9 volt battery powers the Propeller, which incidentally only requires 3.3 volts. There is a regulator included on the Blue board.
I’ll soon have an XBee plugged into the Propeller board.