@bostonmacosx Can you provide an image or sketch of the setup? Not sure if the Drive Motor Sizing Tool is appropriate for your project. The motor is on land while the “dolly” (i.e. pontoons) are in the water? The calculator does not factor in water resistance / cross section as it is meant to be used solely for wheeled robots on land.
Something like this where there is a GT2 belt it will follow on each pontoon…kind of like these picures…top one for the motion and bottom for wht the rig will look like.
The motor will be on the rig with the electronics…easier that way…
May I ask why not…I estimated the weight of the rig as well as a 0 degree incline. It will probably be a few lbs due to the drag of the water but I added that to the weight of the rig.
In order to pull an object in the water, you’re effectively countering the drag of the object, current and built-in friction (and any air drag if applicable), which the calculations don’t consider in any way, shape or form. Accelerating in water is also different, so you need more hydrodynamic related equations. For example: https://physics.info/drag/
If there’s a current which goes at any angle, it should also be factored into the equation in order to determine the maximum horsepower (which will relate to the torque and rpm) of the motor.
When dealing with water, it is not so much the 7Kg weight as it is about drag. When you are talking about how fast you can stop and start, then the mass does matter quite a bit, as it will determine the forward momentum and how much force it will take to counter it. If you want to use less power to stop a floating pontoon boat, think about drag. When you are zooming along in a canoe, and try to stop, what do you do? By putting a paddle in the water and holding it with the web of the paddle at 90 degrees to the direction of travel, you create a lot of drag. This slows the canoe without expending a lot of energy. The same thing can be done with a pontoon boat. Have a flat blade or wall that lowers between the two pontoons and blocks all the flow of water. This will create a great deal of drag and slow the boat quickly at very little power cost to raise and lower the wall. If you need to get the boat going again, quickly, then you will need the larger motors. If it is just stopping the movement that has to be quick, then this might be a good solution.
