1/48 scale Type VIIC U-201 build

[Monahan Steam Models]

Not a lot to report today. Spent most of the day doing one last final leaf and pine needles clean up on the property before the big snow storm begins tonight through next week. Stacked another half cord of hard wood on the back porch so we can stay toasty.

Still managed to get a couple small mechanical tasks done on the build today. Also thanks to the trouble shooting help of David and Ken, I was able to finally solve the servo travel issue for the forward planes using the Depth Cruiser module.



After figuring out where I went wrong with the DC module set up, I decided to design and build a set of telescoping double universal joints similar to the solid versions that I made the other day. Simple, quick and dirty.



Nothing fancy.



Set made and finished. Time to install.



Fit just like the solid non telescoping versions did. These were probably not necessary but it gives some freedom of play in the driveline.

Here’s a link to a short video of the motors running with the new universals.

https://youtu.be/v2oeXsjbrhQ

Nick

[Monahan Steam Models]

After a number of successful tests with the first design of the magnetic coupler, I redesigned it to be 3/8” shorter in length. This helped reduce the offset angle of the double universal joints from 30 degrees to 18 degrees.



Here is the little brother version next to the original. It can still hold 4 magnets per half, so eight total but I find four total to be a good starting point. The connection is strong enough not to slip under full power with some drag applied to the shafts but still able to slip easy enough if the shaft is stopped by lightly pinching the spinning shaft. With the current magnet set up, the amps only jump .200 when the shaft is stalled. Work great at low rpm as well.




The double universal joints have a much friendlier angle now.



Space is starting to fill up in the aft section but it is easier to see how everything fits together and has it’s own space. The aft trim tank extends over and above the servo/motor module.



Another view of the same.


It looks s getting there. Still lots more to do still. At this point the port and starboard lower stern hull halves can be permanently bonded together. I will probably do that very soon.

Nick

[Sam Victory]

Very good idea to avoid overloading the motor. The magnets can also be replaced in time if they fail magnetically. I have had this idea before, using magnetic coupling to complete the connection between the motor and the propeller, and the number of magnets at each end of the connector to achieve the right reduction ratio. I also designed a radar rotation device for the I-400 submarine (for dry hull submarines), also using magnetic coupling, which is easy to disassemble.

[neitosub]

Glad the wobble problem got solved! Was really surprised at how smooth those brushless motors ran when you showed them at the Dive Tribe meeting yesterday. Might go with a brushless setup myself in a future build.

Nate

[Monahan Steam Models]

Thanks for sharing this Romel. I may explore something like that just to see first hand how well it works.

For now I was able to test the magnetic coupler this morning. It works really well. With the motor at almost full throttle and grabbing the coupler with my hand to stop it, the motor kept spinning while the coupler remained stopped. Amperage draw from the motor only climbed about 1 to 1.5 amps while the coupler was stalled. That was using all four magnets in each part, so eight total. The number of magnets could probably be reduced by half. I did a live demonstration of the magnetic coupler during today’s Dive-Tribe video meeting.

A problem that I discovered this morning is the outrunner brushless motor casing (the part that spins) was not running true to the axle centerline. They wobble fairly bad. I’m guessing the center shafts are bent. Bummer because I really liked how well the 350kv motors performed. The wobble was more noticeable once the longer magnetic shaft coupler assembly was bolted up to the motors. I know the mag shaft coupler runs true because I tested in the lathe.

I’ve since swapped out the 350kv outrunners for the 500kv motors I had on hand and the wobble problem was solved. The initial tests for the mag coupler has gone well so I’ve revised the design so that the overall length was about 3/8” shorter. Doesn’t sound like much but this will allow me to gain a better angle with the double universal joints which will further improve the shaft connection smoothness. I like quite and smooth running gear.

[redboat219]

https://vbn.aau.dk/en/publications/design-and-construction-of-permanent-magnetic-gears

[Monahan Steam Models]

Nick,
would offsetting the shaft of the magnetic coupler to one side work, something like on a countergear? M is the motor P is the propeller, instead of intermeshing teeth you use magnets.
.

Yes that would work. The motion at slow speed would experience a bit of cogging motion. Not sure off the top of my head what the work transfer efficiency would be between the two parts

[redboat219]

Nick,
would offsetting the shaft of the magnetic coupler to one side work, something like on a countergear? M is the motor P is the propeller, instead of intermeshing teeth you use magnets.
.

[Monahan Steam Models]

Started work on the magnetic shaft couplers today. I have to say spinning them by hand and hearing the click click click of the magnets slipping and grabbing again is somewhat therapeutic in a strange satisfying way. We’ll see if it’s still therapeutic in normal operating conditions.



The side of the coupler that is fixed to motor has four 1/8” dia. X 1/4” length magnets embedded into the mating face of it with all magnetic poles facing the same direction. The center of the coupler supports two stainless steel sealed ball bearings. (Had them on hand, may switch to ceramic ball bearings later)




The output shaft side of the coupler also has the same four embedded magnets with opposite facing poles than the motor side coupler. A 4mm center shaft engages with the bearings in the motor side coupler to keep everything supported on the shaft axis and rotating freely during slippage.



The two parts of the magnetic shaft coupler snapped together.



Sneak peak of the motor module installed with one of the magnetic couplers in the hull and connected to the port side shaft. The double universal joint has a bit more of a offset than what I would prefer to see but the assembled components rotation by hand is still very smooth.

[Monahan Steam Models]

Spent most of the day with out power to the house. We’re in the middle of adding more solar panels to the already massive system we have currently. We’re rated as a small power plant for the local grid. In addition to the panels we added to the system today we also added a bank of Tesla power wall batteries and brought in a crane this morning to set the back up generator on its concrete pad. Lots of redundancy.

The shop however is on a separate 3 phase electrical system so I spent part of the day in there enjoying not being back in the Stone Age.

I finally was able to get a piece of the material that I was looking for last week to create the stern plane shaft system that I had originally had in mind for this build. It’s a piece of 3/32” X .014” wall square brass tube. Nothing special to get unless you live in the sticks!

Anyways here’s the original stern plane design that is completely removable from a bonded together hull.



Here’s the finished parts that make up the assembly. The center link arm has a square hole that accepts a short length of 3/32” square tube to be freely slide through it. This allows the center link arm to be dropped down into the narrow hull space where the assembly lives.



3/32” tube slide into center link arm




Each dive plane has a square drive socket and round bearing surface to mate up to the bearing in the hull add square drive shaft from the center link.



Stern planes rough assembled on internal shafts.



Everything connected together. A partially threaded pin with 1/16” od shaft will provide the outer most plane support through the molded abs stern plane guards. This will also keep each stern plane in place.

Nick

[Monahan Steam Models]

I love your attitude, Nick.

You are a master builder as well! Target boats, Tug boats, STEAM ENGINES, and Submarines. A very skilled craftsman for sure!

Rob
"Firemen can stand the heat"

Thanks Rob! I just like building stuff and there’s so many different types of neat things to make and ways of making them.

[rwtdiver]

Finally got around to working on the stern plane linkage today. The piece of material that I was searching for locally a week ago to make the original stern plane shaft mechanism that I had wanted to make was ordered and should be here this week. That design will allow the shafts and lever arm to be removed from the hull after the hull halves have been bonded together. For now I’m using the compromised design that I came up with a week or so ago.

The rest of the linkage stays the same.



Here is the main link to the stern plane shaft. The link end at the aft end uses 1/32” brass wire and is the stepped up to 3/32” brass tube before being stepped back down to 1/16” brass rod. This is done to reduce flex in the link.



Top view of the main link connecting to the intermediate stern plane lever arm situated between the propeller shafts. From the intermediate lever arm the linkage is connected to the servo link connection arm on the forward end of the stern torpedo tube support. Also visible is the servo link arm connection for the rudder gear.



Another view of the same.



Now with the stern torpedo tube mounted in place and rudder linkage connected. Still need to connect the rudder and stern plane rods to the servos but that will only take a few minutes. Everything is designed to be removed and easily worked on just as Bob Gato quickly noticed and pointed out earlier in this build thread.

Besides finishing up on the torpedo launch linkages, the last major mechanical connections that need to be made will be from the motors to the shafts. I have a crazy idea of designing magnetic slip clutches for each motor to shaft connection. This has been done before and is not a novel idea by any stretch. It is an added fail safe not to blow the main system fuse should the props become fouled and motors overloaded. Probably not needed but hey, I got the free time to do what ever the hell I feel like doing.

Nick

I love your attitude, Nick.

You are a master builder as well! Target boats, Tug boats, STEAM ENGINES, and Submarines. A very skilled craftsman for sure!

Rob
"Firemen can stand the heat"

[Monahan Steam Models]

Gantu,

Great photos! Thanks!

Nick

[Monahan Steam Models]

I am playing with this too! I can do flat surface to flat surface, but been playing with simple notches to give better grip and to push through small weed issues. Magnets slide off each other pretty easily. I can add more magnets or go bigger, but might create an alternate universe and distort time and space. Look forward to what you discover as well. I could also slightly angle the magnets to improve gription (grip and traction).

That’s awesome Tom! I will definitely share what I find.

What I can see being some initial design objectives would be the gription as you point out would need to easily overcome any parasitic drag in the shaft and bearings as well as normal operating conditions. The magnetic coupling must slip before the peak amperage draw from the motor becomes higher than whatever is determined to be the ideal threshold limit. With a twin motor twin speed control the combined peak amperage draw from both before magnetic slippage occurs would need to be lower than the main fuse.

[gantu]