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All finished and thoroughly tested. WTC works perfectly. FM transmitter/receiver, static dive tested to 7 foot depth. I will be making some dive videos later this summer or fall. I have a few videos posted to the Facebook Group R/C Submarine Ballast and Dive Systems. Here is some my text documentation from that group. I posted a lot more pics, videos and documentation on that FB Group.
" Revell 1/72 Type IX C (late) U-505
WTC Build.
Some of this was in an earlier post, but I will repeat it here to get it all in one place. Sorry this is so long, but there is a lot going on here.
Building the Basic Cylinder
The first thing I needed was a small metal lathe. I have never used a metal lathe before, so starts the learning curve. I chose a Central Machinery Mini Lathe from my local Harbor Freight store. I bought a set of tools for the lathe while I was there. I bought some additional tools and a four jawed chuck from Amazon to round out what I needed.
My tube came from Amazon, 2.5" PVC dust collection pipe. Yes, it's not lexan, but hey, this was my first attempt so I wasn't going to pull out the big guns.
The bulkhead material is HDPE. Easy to machine.
I started on my first end-cap and researched the proper shape for the o-ring for the particular durometer (50A) I was going to use. One of the basic things about o-ring grooves is that they need to be wider than the o-ring thickness, so that as the outside diameter is compressed, the rubber has somewhere to go. I put the bulkhead and o-ring on the end of the tube and filled the tube with water. No leaks with 18" of head. Beginners luck I guess.
Next were the recesses for the motors.
I planned to recess the motors so that the shafts would stick through the bulkhead. This would be a tricky lathe setup. I drilled two pilot holes for the motor shafts and then got the 4 jawed chuck close to what I thought would center the first pilot hole. To get it true to center, I brought the tail-stock up to the work, with a centering spindle in place and worked the four jaws until the pilot hole was exactly in the center. Then I machined the recess so that the motor would be a tight fit. I also had to make sure I didn't nick the o-ring groove. It was very close. The entire operation was not as easy as I had hoped because there was a boss on the motor for the bearing. I had to grind a special tool to make a recess within a recess for the bearing boss. The first of several special tools I had to make.
The second operation for the aft bulkhead was the recess for the seals I was planning on using. Rather than using o-rings, I opted for the much better cup seals. They have a U shaped cross section and push tighter against the shaft and outer recess the higher the pressure gets. Pretty neat stuff. Fortunately, I was able to use the boss tool I made to get this done.
After all the work on the aft bulkhead, making the forward bulkhead and wet chamber bulkheads was a breeze. Well, as long as I remembered that when you move the tool into the work, it's the radius you need to use as reference. If the diameter is used, you either end up with taking off twice as much material as you planned, or you remember to divide that number by 2. There's that learning curve again.
The ballast bulkheads did have some tricky work in them, as I decided to put o-rings in the holes drilled for the wire conduit. Had to make an even smaller tool for that.
I tried using one speed controller for both motors, but was not happy with the motors not starting up at the same time, so I went with two DC forward/reverse speed controllers.
I chose a small diaphragm air pump with a DC forward/reverse speed controller, naively thinking that I could have perfect control of the incoming and outgoing air flow. The pump had speed control, but diaphragm pumps only pump air one way with the motor going forward or reverse. Learned something that day.
Then I decided to try a geared pump. Well, they are heavier, use a heck of a lot of power, take up more space and are not air tight when at rest. Ditched that idea.
Back to the diaphragm pump, which also is not air tight when at rest. So how was I going to control the flow of air in both directions? I settled on two micro valves. A two port valve to stop the airflow when the pump was at rest and a 3 port valve to allow air in and out of the ballast chamber.
I also extended a brass tube along the top of the ballast chamber and stopped it in the middle, cut the end on an angle and bent it towards the top so that in the event of the chamber completely flooding, the tube would see the last available air. Also, the air intake and exit uses the entire WTC, so air is pulled or pushed through the WTC and the antenna/snorkel tube. The air supply exit at the aft bulkhead is near the top, but has a short silicon tube that extends down to the bottom of the aft chamber. This is to prevent any water that might enter from dripping on the motors and electronics. I have attached a napkin diagram to show how this all works.
My initial trials with just the WTC and some lead strapped to the bottom went well. Next I did some tests with the WTC in the hull. Those went well. Then I put on the deck and conning tower. Didn't go very well. Not only are you having to off-set the weight of the hull above the waterline, BUT you also have to off-set the flotation of the snorkel mechanism. Duh! There was just not enough reserve capacity in the ballast chamber. Out came the 2200mAH battery and I enlarged the ballast chamber and made a longer wire conduit. Now I had reserve ballast capacity, but a smaller 1300mAH energy supply. Luckily I kept all the equipment as efficient as possible.
The servo rods start small and then are sleeved to a larger size where they exit the bulkheads. From there they are further sleeved to accept 3mm magnets. All soldering was done with the magnets removed. And as stated previously, all control rods are in a straight line from servo horn to the control surface. No multi linkages or Z bends.
All the pass-through tubes are friction fit, no seals. HDPE is relatively soft. I bought a number drill set to have more choice in tolerances.
Hopefully this helps anyone considering to undertake the design and building of their own WTC. If I can do it, you can do it!."
" Revell 1/72 Type IX C (late) U-505
WTC Build.
Some of this was in an earlier post, but I will repeat it here to get it all in one place. Sorry this is so long, but there is a lot going on here.
Building the Basic Cylinder
The first thing I needed was a small metal lathe. I have never used a metal lathe before, so starts the learning curve. I chose a Central Machinery Mini Lathe from my local Harbor Freight store. I bought a set of tools for the lathe while I was there. I bought some additional tools and a four jawed chuck from Amazon to round out what I needed.
My tube came from Amazon, 2.5" PVC dust collection pipe. Yes, it's not lexan, but hey, this was my first attempt so I wasn't going to pull out the big guns.
The bulkhead material is HDPE. Easy to machine.
I started on my first end-cap and researched the proper shape for the o-ring for the particular durometer (50A) I was going to use. One of the basic things about o-ring grooves is that they need to be wider than the o-ring thickness, so that as the outside diameter is compressed, the rubber has somewhere to go. I put the bulkhead and o-ring on the end of the tube and filled the tube with water. No leaks with 18" of head. Beginners luck I guess.
Next were the recesses for the motors.
I planned to recess the motors so that the shafts would stick through the bulkhead. This would be a tricky lathe setup. I drilled two pilot holes for the motor shafts and then got the 4 jawed chuck close to what I thought would center the first pilot hole. To get it true to center, I brought the tail-stock up to the work, with a centering spindle in place and worked the four jaws until the pilot hole was exactly in the center. Then I machined the recess so that the motor would be a tight fit. I also had to make sure I didn't nick the o-ring groove. It was very close. The entire operation was not as easy as I had hoped because there was a boss on the motor for the bearing. I had to grind a special tool to make a recess within a recess for the bearing boss. The first of several special tools I had to make.
The second operation for the aft bulkhead was the recess for the seals I was planning on using. Rather than using o-rings, I opted for the much better cup seals. They have a U shaped cross section and push tighter against the shaft and outer recess the higher the pressure gets. Pretty neat stuff. Fortunately, I was able to use the boss tool I made to get this done.
After all the work on the aft bulkhead, making the forward bulkhead and wet chamber bulkheads was a breeze. Well, as long as I remembered that when you move the tool into the work, it's the radius you need to use as reference. If the diameter is used, you either end up with taking off twice as much material as you planned, or you remember to divide that number by 2. There's that learning curve again.
The ballast bulkheads did have some tricky work in them, as I decided to put o-rings in the holes drilled for the wire conduit. Had to make an even smaller tool for that.
I tried using one speed controller for both motors, but was not happy with the motors not starting up at the same time, so I went with two DC forward/reverse speed controllers.
I chose a small diaphragm air pump with a DC forward/reverse speed controller, naively thinking that I could have perfect control of the incoming and outgoing air flow. The pump had speed control, but diaphragm pumps only pump air one way with the motor going forward or reverse. Learned something that day.
Then I decided to try a geared pump. Well, they are heavier, use a heck of a lot of power, take up more space and are not air tight when at rest. Ditched that idea.
Back to the diaphragm pump, which also is not air tight when at rest. So how was I going to control the flow of air in both directions? I settled on two micro valves. A two port valve to stop the airflow when the pump was at rest and a 3 port valve to allow air in and out of the ballast chamber.
I also extended a brass tube along the top of the ballast chamber and stopped it in the middle, cut the end on an angle and bent it towards the top so that in the event of the chamber completely flooding, the tube would see the last available air. Also, the air intake and exit uses the entire WTC, so air is pulled or pushed through the WTC and the antenna/snorkel tube. The air supply exit at the aft bulkhead is near the top, but has a short silicon tube that extends down to the bottom of the aft chamber. This is to prevent any water that might enter from dripping on the motors and electronics. I have attached a napkin diagram to show how this all works.
My initial trials with just the WTC and some lead strapped to the bottom went well. Next I did some tests with the WTC in the hull. Those went well. Then I put on the deck and conning tower. Didn't go very well. Not only are you having to off-set the weight of the hull above the waterline, BUT you also have to off-set the flotation of the snorkel mechanism. Duh! There was just not enough reserve capacity in the ballast chamber. Out came the 2200mAH battery and I enlarged the ballast chamber and made a longer wire conduit. Now I had reserve ballast capacity, but a smaller 1300mAH energy supply. Luckily I kept all the equipment as efficient as possible.
The servo rods start small and then are sleeved to a larger size where they exit the bulkheads. From there they are further sleeved to accept 3mm magnets. All soldering was done with the magnets removed. And as stated previously, all control rods are in a straight line from servo horn to the control surface. No multi linkages or Z bends.
All the pass-through tubes are friction fit, no seals. HDPE is relatively soft. I bought a number drill set to have more choice in tolerances.
Hopefully this helps anyone considering to undertake the design and building of their own WTC. If I can do it, you can do it!."
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