Pool testing a model of the Mark-I
Submitted by parkviewadmin on Sun, 2006-01-29 17:43.
I was concerned about the how well the Mark-I might turn with the motor mounted midship of the boat, so I decided to build a small 30cm model using 25mm PVC tubing. Out came the scrap pieces of MDF and hot glue gun. I had a CD-ROM drive lying around, so I dismantled it, and extracted the head positioning motor. Part of the case was cut up to became a dodgy looking propeller. The shaft was constructed from two 25mm nails, soldered together. After soldering the propeller onto the head of the nail, I used a few layers of heat shrink to join the shaft of the motor to the top of the nail.
Using an old plastic gear, as a bushing, and a few bits of MDF to hold it altogether, I had an adjustable height and swivelling motor mounted midships of the model.
So after a quick bath test, where I found out I needed a more flexible power cable, I popped over to a mates house to test it out in in the kids pool.
With Bruce taking the photos, I was left trying to hold two 1.5 volt batteries, and the light gauge (unwound motor wire), and keeping the power flowing. Whilst it would go forwards and backwards quite well, the turning circle was pretty well non-existent. So, after arriving home, and uploading the photos, I thought why not try moving the motor aft, and have another go. This time, I hunted up a battery holder, and dual trio-pole switch, so I could easily reverse the direction of the propeller 
Back at Bruce's pool for a second trial run, we found that the model would turn very easily whilst going forwards, however, in reverse, the boat would be dragged sideways, instead of turning. Maybe it was because the front of the model lifted out of the water so much, that the hull no longer acted as a keel.
As you can see above, I will have to separate the motor from the electronics and batteries. Instead of building the superstructure straight onto the hull, I might strap it onto the hull, so I can move it around to get an even keel. Not bad for 5 hours of worth while work. I might hold off on the CAD redesign, until I have tested the real Mark-I.
Thanks Bruce for the loan of the Pool.
Note: you can click on the above thumbnail pictures to see a larger version.