K80 wrote:Hi Rob
I am a newcomer to submarines, and I shall soon be building a Type VIIC U-Boat in 1:72
I am afraid that I am completely clueless when it comes to RC systems, besides radio sets, servos and speed controllers, I have little experience with such things.
You're far more educated than me on the subject, so maybe we could share information as our builds unfold?
I look forward to seeing your progress
All the best
I doubt that I am significantly better informed (if at all) than you K80, but will update you with my progress.
I have obtained a 50mm OD length of extruded acrylic tube and am in the process of trying to design a 3d printable set of end caps, motor and servo mounts. I have a single 385 brushed motor and a speed controller with BEC for the same plus some prop shafts and a pair of handed 25mm diameter 3 blade props. I have also obtained some servo rod bellows (don't know what else to call them) and some O rings for motor shaft seals and end cap seals. Some experimentation will be needed to get the appropriate depth of groove for the O rings in the end caps. I have decided to take a leap into the unknown with openLRS radio and have ordered a tx module and rx from Hobbyking (unfortunately only the global warehouse stocks these items apparently, so delivery time and final cost due to possible tax and handling charges remain unknown). As the first iteration of the design will be surface running (or possibly dynamic dive, depending on rate of progress) I have not addressed a ballast system at all. I suspect I should have gone for a bigger diameter tube to accommodate this in future, but lets get the mark 1 working first.
I have the following design decisions/questions which I would like some suggestions for if anyone can help;
- Do I need a reduction ratio between the motor and the props? One internet item suggests 2:1 reduction.
- As I am running a pair of handed props from a single motor, am I better with the gearing inside the WTC (requires two shaft seal) or in the wet section (has the gearing running in water, which might be good for wear, but bad for friction loss)?
- As the twin rudders are positioned well outboard, can I implement twin rudders or depart from scale to a single central rudder?
- Will a 3D printed endcap be sufficiently waterproof? Acetone smoothed ABS is supposed to work for bowls and vases, but will it take any pressure? If not, what do I do without a lathe?
- What problems have I not yet realised?