Building a 3.5" WTC

[salmon]

I have been fascinated with a piston system since Will Oudmayer handed me his Walrus and had me get the sub to periscope depth then play with it. He is a R/C Sub Drug peddler. I was hooked. I have bought several of his subs. He also encouraged me to build my own.....fast forward 5 years and here I am.
I think I have all the major components made, now it is time to assemble all parts together.

Here are the parts:
Motor endcap


I am using a brushless motor (Engel). So this end was designed specifically for that motor. The motor shaft extends outside and is a direct drive.
The tray behind it holds the servos, but underneath is a pipe to direct the water in and out of the piston. I almost made a square tube if I needed room, but this worked out fine round.


The servos, leveler, and ESC fit fine on the shelves, however, another ESC (another Engel one) will probably need extending.


The piston is 2.5" and has a stroke of 6"


The gears were 3D printed, but cast in resin. The 3D printer pieces seem to be real brittle. I dropped a tray and it broke.


The rod has a stop on it that will trigger the micro switch.


The micro switch that the end stop will trigger.


The power self holds the piston controller and BEC and both microswitches.


Then there is the battery tray. I will be using 10 cells of 3000MH NiMh. They are clustered that most of the weight is lower.


The next bulkhead holds a nut in it that the end cap will screw into.


This will hold the end cap in and will have two o-rings to seal it.


Here the end cap is assembled

[salmon]

The final view, this WTC will be 19.5" long (+/-)-ish.

[bob_eissler]

Very nice! How much water will the piston tank displace?

[salmon]

Thank you! A little over 23 cu inches (that's if I did my math correctly).

[JWLaRue]

Very nicely done, Tom!

-Jeff

[salmon]

Thank you Jeff!

[sam reichart]

That looks awesome, Tom. I see people building out their own ballasts systems and think to myself that engineering systems like that takes a lot of talent; far more than I possess. Thankfully, vendors keep making them for those of us that just don't have that engineering gene.

[scott t]

Looking good Tom!

[salmon]

Thank you Scott and Sam. I do not know if I do have the engineering gene. More like the Rube Goldberg gene LOL That being said, Will Oudmayer is my inspiration I am building off of. Then add to that a lot of trial and error.
Hopefully in the next week or two, I will be able to wet test it.

Peace,
Tom

[salmon]

Playing is fun. This will be my pushrod seal. The center has a small o-ring that the two halves lovingly squish between them.



There is a nice resistance to them. We will see if this seals or leaks like a sieve.



All is on the bench and getting wired up.

[salmon]

This has been a long and learning journey. I still have not gotten this wet, so it may be a flop to begin with!

Here is where I am at, All systems now work. I originally was going with brushless, but there was a problem with the setup (need to send back for replacement, but Corona virus haas things at a standstill). So, I went with brushed. To do that meant some re-imagineering.
The water passage had to be changed because the brushed motor is a lot larger than brushless. I split the water into two paths to overcome this.

Then needed to do some reduction gearing to bring the rpm down. So created a bulkhead to house the gears.



Anyways, here it is:



Opening it is based on Will Oudmayer's way of doing it.




Battery section. Bought Chinese NiMh AA batteries, claimed 3000Mah. Don't believe it. These do not last more than 10 minutes before dying. So, I either have a short, high drainage, or they are cr@ppy. I have new batteries coming in.

The piston controller is from http://momo-sauerland.de (really awesome people to deal with!)
My piston is almost 7" in length and a 2.5" diameter.

[salmon]

Then the engine room.....a couple of servos and a brushed motor (buried in there). I used a 3 to 1 ratio for the gear that are also 3D printed. All of this is an experiment to see what works or not.


So, soon, this will get dunked and see if it sucks water in and goes thermal or if it sucks water in dives and keeps electronics far away from getting wet.
Peace,
Tom

[scott t]

Tom this is very cool. I replied back in January that this looked good but I took time to study what you have done and it is very cool.
The way it all fits like a puzzle is very cool. Keep on buddy.

Scott T

[thor]

I may have missed this earlier, Tom, but what boat are you planning on installing this in? Very nice work so far!

[salmon]

Matt
The Skipjack. Will Oudmayer built a piston system for his and then challenged me to build one.
Scott, thank you! Maybe the puzzle reflects my jumbled mind? LOL


Peace,
Tom