sizing a thruster for a little marine system

[leonardorlando]

Good morning,
I am a representative of a group of Italian students who are developing a project for their university. The project consist in a robot system (MAYBE INFLATABLE) that floats on the water, also rough water, and can be autonomous or remote controlled. This System will be 1.5 metres long and 1 metre large. The robot must have the possibility to carry a person, so the weight can reach about 150 kgs (with the person). We prevede that if this robot will be successful we can sale a lot of them to many organization. Here is the problem:

What kind of thrusters do you advice?
We are going to use two Brushless DC Electric Thrusters.

Which value of Thrust we have to consider? Why, in your opinion?


Thank you, we are waiting for your answer

 

[Silvertip]

Re: sizing a thruster for a little marine system

Since this project has to carry a person, and is about five feet long, weight is going to be a factor. So my question back to you is why use two thrusters when on that size vessel, one would be just fine, steering would be simpler and much less power in the form of batteries would be needed. I suggest you look at an American made trolling motor such as the Wireless MotorGuide or the MinnKota Power Drive. These systems have electronic steering and motor controls built in and are already are wireless. The smallest of these delivers 40 pounds of thrust which would be more than adequate to move your vessel -- at a fair rate of speed I might add. I have a 55# thrust Power Drive on my pontoon boat and it pulls that around with no problem. Wireless units are not generally available in the smaller motors. However, an older 25# manual control trolling motor would meet requirements as well but would require some engineering for remote control of steering and speed. Any of the motors I mentioned will operate for hours from a single RV/Marine deep cycle battery.

 

[4JawChuck]

Re: sizing a thruster for a little marine system

I think you will find this manufacturer produces a lighter product already suited to your project, their power head come prepackaged for attachment to a kayak which is about the weight and size you require. Not cheap but in Italy this german mfg should cost the same as a US based mfg.

http://www.torqeedo.com/us/hn/products/ultralight.html

Superior thrust with less power, their props are designed for efficiency not weed wacking. Their lithium maganese battery technology is far superior to lead acid with less weight and higher range not to mention stability in storage and cold weather with no charge memory effect too.

I would re-think inflatable and go injection molded chambered construction, more durable and UV stable for long duration missions.

Check out the video;

http://www.torqeedo.com/us/sn/image-library/videos/ultralight.html

Their "cruise propeller" really moves a small boat too!

http://www.torqeedo.com/us/sn/image-library/videos/cruise-40-r.html

 

[Silvertip]

Re: sizing a thruster for a little marine system

A used 24# troller can probably be found on e-bay for $25 or so. Even a new one can be had for less than $100 on sale.