Kayak motor

Hi all! This is my first message here. Sorry if there is something familiar around at the thread, i couldn't find, please the admin to move it if necessary.

I am thinking of making a trolling motor with a straight shaft. I don't want to have issues with waterproofing my motor, so i will put it over the sea, at the side of the rail inside a waterproof box. I am thinking like the image i am sending. I am planning to use this 70110 brushless motor but it is out of stock for now or something similar. Of course with the right esc and speed controller and i don't know yet what battery. Generally i would like some suggestions for the parts. Do you think that my plan will work?
https://alienpowersystem.com/shop/brushless-motors/70mm/aps-70110-outrunner-brushless-motor-100kv-3200w/

 

Could and probably would work.
Search this site for a plethora of threads dealing with "long tail outboard" or "cordless drill outboard motor"

 

Thank you very much.

 

Excellent information in this thread:
Efficient solar powered (electric) kayak https://www.boatdesign.net/threads/efficient-solar-powered-electric-kayak.52833/page-6#post-745467

 

Search the forum for extensive descriptions of propulsion with a battery powered electric drill. That is an old thread but it may be of interest if you can dig it up again.

 

The o p link has reference to transmission kit. Small Gearing down losses might allow for a still more efficient arrangement compared to direct drive, as it might be possible to fine tune the RPM and torque to the Peak efficiency using reduction for a particular motor and prop. In the solar powered kayak motor link, the motor was only run at a maximum of around 10% of rated power, which might not be the best match of size, power and load. Hope this helps.

 

Thank you all for your kind replies. I would like to avoid gear down, because of the noise and also i would prefer avoiding the need of water sealing. I mean i will use a ready water sealed box for the motor, esc, batteries and controller to fit, but i wouldn't mind for the shaft. Because of that i was thinking that i could just use ceramic bearings for the 10mm stainless shaft to move inside a stainless steel tube that will be strong to avoid wobbling. Also this motor i am talking isn't much kv (it is only 100) so i think that i will have rpm around the needed for that use.

 

The gear down is done with silent pulleys and timing belt, which allows easy and fast change of pulleys until the best ratio is discovered. See a Alien Drive complete kits for example. The RPMs of at least some OutRunner Motors are too high without gear down, to match an efficient prop when run at design voltage and speed. There was reference on the second link to using ventilated noise shielding on the OutRunner Motors themselves which already have a loud unpleasant noise, even without gears. Putting the four components you mention in a slightly vented or sealed box might likely cause overheating to the point of a fire hazard, as these major components generate considerable Heat. It is hard to believe, but the trailing shaft doesn't need bearings to avoid wobble, especially if it is made of spring steel where it curves and self aligns to the horizontal. Myself has been using a geared down system with flex shaft an average of once a week, for many years. But you know your own situation much better than I, so some of these ideas may not work for you. Depends on the Range, speed, portability, and other factors that you need.

 

Dear friend, thank you very much for your advice. I don't know some of the things you suggest. I don't know what spring steel is. I was planning to use stainless steel 10mm shaft. The overheat is something i do mind. I thought if i could make a water jacket for the motor maybe i could solved some problems? Your idea with pulley gear down system is something i will surely consider. Could you please tell me something because i don't understand. If the motor is strong and i have higher rpm doesn't that take me more speed? What is the problem with having more rpm at the propeller? I was thinking that 100kv motor with 42v battery would bring me 4200 rpm. Is it too much?

 

Look at PC answers below.

PC. You can do a Google search to get information on Spring Steel.

PC. An aluminum heatsink outer case might work and would be much simpler. Google is your friend, will give some information.

PC. Yes, 4200 RPM would be too much for the 10x 6 propeller shown in the link, that would overheat the motor, and use up all your battery power very quickly. Your speed would barely increase after you reach what is called hull speed ( Google). But the ESC can be used if you don't go above around 1000 RPM as referenced in the second link above. The gear down is for reducing the maximum RPM and lowering the power drain on the batteries, while keeping the motor cool.

 

I found the cheapest and in the end simplest was using a longtail straight shaft connected to an 18v brushless drill. Speed approx 5 km. and a 4ah battery lasts about 2km distance. When it dies replace the battery. The was using a 5in prop.

 

You need to have thrust bearings in the shaft. Electric motors like you show are not designed to have a load parallel to the shaft. A trolling motor is cheaper and simpler. However, if you really want a longtail motor instead, modifying a trolling motor is still cheaper and simpler.

 

A battery operated kayak is a bad idea. Powerful batteries and water can result in deadly electric shock. Any battery that falls overboard is toxic to the environment. When the battery dies, it's that much more drag when paddling back.

 

I used this system both in Thailand and Australia over three years, I had no bearings, the shaft was threaded, and the pipe the shaft went through was an agricultural plastic pipe and no problems. The drill was in a waterproof bag

 

Something like this using teathers to keep the drill out of water