Model Row Boat
by Paul Jeffries
Many years ago in a boat magazine I saw an illustration of a rowing mechanism for a model boat. The drive came from one source but the rowing could be controlled to go forward, reverse, left and right independently.
Please could you tell me where I could access this information again?
Sorry, I don't off hand. The only RC model row boat that I know of is from the old MAP plans service. The boat had an "Action Man" (GI Joe in America) figure rowing. As I recall the drive mechanism was a single motor, but I don't believe each oar was independent. Instead it used a rudder for steering.
About fifteen years ago I researched building one of af Chapman's gun sloops as a rowing RC model. Nothing ever came of it, but I considered a few different solutions for the rowing mechanism. Three of them stood out:
- Single motor with differential
This idea would use a single motor driving each side through a mechanical differential.
The best example of a differential is the drive axel on a rear wheel drive car or 4x4.
For a row boat the motor and ingoing shaft would be along the boats center-line. One outgoing axle , or shafts rather, would point to starboard and one to port. Each outgoing axle would have a crank for the oar motion and a simple brake controlled by a servo. By using the brake on either side, the opposite oar would get more torque and force the boat to turn.
Sounds simple enough in theory. There are several problems with this design though. Without going into too much detail, the nature of a differential makes it near impossible to tune to run synchronized. To synchronize we need to add some form of encoder feeding back to the brake servo. By then the complexity has spiraled out of control, and we're better off looking for another solution.
- Dual Motors
Running each side with its own motor is better. Synchronizing the two is still an issue, but not nearly as bad as the differential design. It could be done by adding a switch (reed, hall effect, photo interrupter etc) and some form of latch circuit. Each motor would run until both port and starboard switches are made before starting the next cycle.
Finding usable low-voltage gear-motors has never been easier or less expensive thanks to the vast surplus market.
I'm not sure if Maplin would have anything useful, since you're in the UK. In the US I'd look through online surplus houses like All Electronics, Electronic Goldmine, Surplus Center, American Science & Surplus, Herbach and Rademan to name a few.
Replacement motors for the Heng Long RC tanks could also be of use. They are tightly integrated with a corresponding left and a right hand side. They may still be too fast though.
For small model boats, the Tamiya Educational and Robotics series have some very inexpensive dual motor/gearbox kits.
- Single motor, fix coupled oars
This is by far the easiest solution. The oars are mechanically tied together, so they will stay synchronized. Some sort of circuit may be desirable to make sure the oars are out of the water when stopped, but would not be absolutely necessary. Steering would be done with a rudder.
Again, Tamiya Educational Series has some good motor/gearbox solutions for small model boats. There are usually several options for a final gear ratio.
I'm sorry I couldn't be of more help with the specific article you were looking for, but I hope you'll find some of the above useful.
Best of luck!