Still learning about loading pics, but I never did find my build blog. Will start another

Hello Dave, I did try to start a build blog, but once started I was never able to find it again. I will log out and back to see if this resolves itself. I am not so hot with computers. I did try to load some pics. One of the boat I am roughly trying to model, and one of the C-face motor to stern tube mounting system I built today. it features a lip seal on the motor end of the tube to keep the salt water out, and I will load the tube with a bit of water proof grease as well. I am a bit concern d that the torque will turn the tube adaptor in the tube, so I made the bearing that fits in the tube about 3" long, and will use a loctite product to seal, and "glue" itself in place.

Steve

Steve
Glad to have helped. The motor is not that current hungry and at lower volts should not struggle too much with the reduction unit. The actual speed will depend on the throttle settings but if you use 12v the output should be just right for your purpose. The ESC suggested sounds perfect. The actual amps used will depend on the load placed on the motor so can really only be indicated with static info. You can buy cheap power meters that will give an accurate on water indication and holding the model as you apply full speed will give a good indication of the current being drawn. The real benefit is that you can ensure that you are not exceeding the watt rating on your motor or speed controller, both of which will overheat and damage if the amount is excessive.
In case you have not fitted one a big fuse on the battery feed is a good idea to protect your model from any electrical faults. Fuse needs to be just above the stall current rating so 25 amps seems about right. You may need to adjust this higher if the fuse keeps blowing and there is no obvious fault.
Depending on the time you wish to spend collecting logs will determine the battery size. I would suggest 12AHr as a good starting point, as you have lots of room and need the ballast a Golf/Wheelchair type battery may be a good choice but some may be costly and 2 12 AHr in parallel would work just as well.
I use stuffing boxes at the motor end of the shaft with a turned brass fitting that is threaded onto a sleeve over the shaft. I can then adjust if water is seeping but your solution should work well.
The control sticks on transmitters can easily be modified to have the spring return removed. You may need a small ratchet brass shim to ride on the internal serrated plastic adjacent to the internal part of the stick. I suspect this may not be present on the horizontal fitting so you may need to Improvise or turn the whole stick unit thro 90deg. if you are happy with a free floating stick this may nt be a problem.
Very Impressed with the nozzle. The pic loaded OK. Be good to see some more pics of the boat. You can load up to four pics per post or why not start a build blog. Your model and its proposed usage is certain to attract some interest.
Good building
Dave

Hello Dave, and thanks for your help. The motor is actually a MabuchI RS-755VC-4540 and is rated 50 watts at nominal 18 volts, but available to operate at 9-32 volts. 18 volt loaded speed is 7500 rpm, so I hope not to need all 18 volts to get the power I need. As I understand it, the loaded rpm will drop with proportionately with the volts, so a 9 volt pack would be 3750 rpm, for a final speed of 1500 rpm. 12 volts then would be a final full speed of 2000 rpm. This still seems high to me but perhaps as we scale down things speed up? Yes very much want good "very slow" performance, so I think I will go with this brush motor package, and see how it goes. Does 12 volts sound like a good place to start? Motor stall current at 18 volts is 22 amps, (full load is 4) and I suspect that as the volts used drop, the amps drop faster, so I suspect that at 12 volts, a 30 amp speed controller would be lots?. By the way, my stern tube is fully submerged and well below my waterline at both ends as I wanted the thrust to be in line with the boat. My stern tube has no seal, just a brass bushing on each end. Being salt water I want things pretty tight so am considering taking out the bushing on one end and replacing it with one I machine, that gets bigger on the motor end and has a machined area such that I can fit a 1/4" X 1/2" double lip seal for positive sealing. Fill the rest of the tube with waterproof grease mixed with some oil so it does not get too thick? Futaba 4 channel radio the "go to" radio? I would like a non returning stick for fast and slow, as well as non returning (not sprung back to middle) for the steering as when pushing objects, one often has the steering off center for quite a length of time. I tried to add a picture of the nozzle, but so far it does not look to have worked. Also wanted to show a picture of the keel and "Jaws" on the bow. The keel is 1" thick X 3/4" stanless steel bar, and acts as a shoe for the Kort nozzle. At the bow the jaws are this same stanless steel bar, but with angled jaws ground into it so one can "dig in" to a log and push it for the end or side.
Thanks again for your thoughtful reply.

Steve

HI Steve
Welcome to the site.
Sounds more like a commercial enterprise than a modelling topic.
Must be great fun to actually use a model to collect firewood.
I am not familiar with your particular motor and can't find any specs on the web, but with your set up it sounds good for the task you have in mind. As you can use plenty of battery power and weight is not a problem a good heavy duty SLA or two should give ample power. Not sure of the voltage for the motor but you can put batteries in series to achieve higher volts. The higher the AmpHr rating the better.
If you already have a speed controller I see no need to change. However more modern ESCs are likely to be more efficient and give you better low speed control. The amp rating need to be at least 50% greater than the motor stall current. Sorry but without knowing the motor stats its difficult to give more detailed info.
If your setup is using lots of watts (amps x volts) then you may need to water cool the motor if it is getting too hot to touch after say a couple of minutes hard use.
Brushless motors have masses of power and as you possible realise do not require maintenance of brushes. However low revving high power motors and controllers are not that cheap and can be difficult (at times) to reverse, so may not be that good in a tug.
I personally would stick with your existing set-up and see how it performs. Moving to brushless with that size prop will be an interesting exercise to get the prop speed down to a reasonable level. I have tried running brushless at lower volts. The problem is the current increases at lower volts so you have a shorter battery life and a big heat problem. I solved my problem by adjusting the control to the ESC on my Futaba 6EX transmitter but this was on a fast Fireboat and may not work as well on a slow tug.
Wishing you the Seasons greetings and good luck with your project 😀