today's work

[Ken_NJ]

Here I'm issuing the typical Diver-hand-signal, 'first dive of the day'.



Couldn't have an event without a typical David hand signal!

[He Who Shall Not Be Named]

Wow. Thanks David. I remember that piping and the shed... right side of the lake there, as I recall. I'm glad it was easily found. My Arkmodel will be sporting your twin motor WTC when it's ready to go.

Yup. You can see the piping array if you Google Map the lake.

David

[goshawk823]

Wow. Thanks David. I remember that piping and the shed... right side of the lake there, as I recall. I'm glad it was easily found. My Arkmodel will be sporting your twin motor WTC when it's ready to go.

[He Who Shall Not Be Named]

David - do we know what failed on that Arkmodel that caused the need to dive for it? Interested since I own one...

Hey, Sam

The boat was trimmed just a tad heavy, and Mike was new to the helm.

He managed to nose that model under one of the water pipes that cress-cross the North Lake, a network that is fed from the nearby water processing shed.

The WTC was working fine. Loss was a simple 'entrapment' situation in about four feet of water.

Finding it was straightforward and easy: as I ducked my head underwater to listen, Mike would cycle the motors back and forth. I would move in any direction that made the noise louder to me. Before I knew it, it was right under me. Easy-peasy.

Mike bought it RTR from Nautilus Drydocks, but we opted to change out the original WTC with one of my two-motor 2.5 WTC's.

David

[goshawk823]

David - do we know what failed on that Arkmodel that caused the need to dive for it? Interested since I own one...

[He Who Shall Not Be Named]

Successful salvage of Mike Bratley's sunk 1/48 Type-7 at the recent Groton event. Some fool had to go in after it!






Here I'm issuing the typical Diver-hand-signal, 'first dive of the day'.



David
The Horrible

[rwtdiver]

David,

Your work and craftsmanship ceases to amaze me!



I am always amazed at the perfection that goes into your design and the perfection you put into your stern section and the control linkages! So clean and straight forward!

Rob
"Firemen can stand the heat"

[He Who Shall Not Be Named]

[goshawk823]

One of the biggest "eye openers" for me when looking to reconstitute my old WTC 3.5 was the miniaturization of so many of the components that are employed these days. Servo size being the biggest change. I've been out of the game for quite a few years. and the shrinking of receivers, servos, ESCs, etc. is frankly mind blowing. Thanks for the tutorial, David.

[He Who Shall Not Be Named]

AN IMPROVED PUSHROD SEAL

Two of my old watertight cylinders (WTC) were recently pulled out of long-term storage and readied for shipment to new homes. The 2.5" diameter unit was unique in that it had three motors and was used aboard my 1/72 FOXTROT class model. The smaller, 2" WTC, featured two motors and that unit used aboard my little 1/72 Type-7 r/c model submarine.

We've been producing WTC systems for over three decades, and in that time, they have seen much improvement and enhancements. Recently I improved the seals used to make watertight the servo pushrods that form part of the model submarines control surface linkages.

I'll chronicle here the installation of those new seals as well as a quick look at what it takes to re-certify a retired and upgraded WTC for use.

What makes r/c submarines unique from all other r/c vehicles is the need to 'keep the water out'. It's not enough to provide the watertight enclosure -- typically a length of transparent Lexan cylinder capped with cast resin bulkheads at each end -- the system also requires watertight seals to pass drive shaft(s) and pushrods. Internal bulkheads divide the system into three separate compartments: forward dry space, where the battery and mission switch reside; ballast tank; and after dry space, where most of the control and propulsion devices are located.



About twenty-five years ago I started mass producing pushrod seals through the expediency of casting an O-ring within a resin body.

Typically, this type of pushrod seal is secured within the after 'motor-bulkhead' of the system with RTV adhesive. The RTV around the seal body, and the O-ring within the bore of the seal effecting a water barrier between sea and WTC interior. The internal O-ring making an interference fit between itself and the pushrod. However, the use of only one O-ring, over time, results in a loosening of the fit between seal and pushrod and leaking results. Recently I resolved this pushrod seal design shortcoming by simply employing two, not one, O-ring within the seal body.



And here you see the difference between the two versions of the pushrod seal. No need to create new tooling for the upgrade. Just jam in two instead of one O-ring during tool preparation. Make the pour and extract a dual O-ring pushrod seal. Simple as that!





The single and dual O-ring pushrod seals share the same body geometry. Only difference is the number of encapsulated O-rings within.



This particular motor-bulkhead featured three direct-drive 380 sized motors that drove my 1/72 FOXTROT model. A friend needed it for his recently completed FOXTROT model -- I had not operated my FOXTROT WTC for over ten-years, so I sent it somewhere where it would see further good use.

(I pulled the 75mHz receiver from that WTC and kept it for myself. Yeah! Oh? well... screw him, tough **** -- he can come up with his own receiver. 75mHz equipment is no longer in production and has to be husbanded... 'My Precious!!').

So. re-certification started with a function test of all the devices: servos, angle-keeper, battery monitor-fail safe, electronic speed controller, low pressure blower, and battery eliminator circuit. During those checks I found that the rudder servo was dead... tits-up... deceased... broke-****... kaput!... had assumed room temperature.

Here, just forward of the pulled receiver, you see the replacement servo ready to be installed.



Replacement of the bum servo started with removal of the control horn and pushing it and attached pushrod aft and out of the way. Then the brass retaining strap was removed. It was then a simple matter to yank the offending servo -- hurling it viciously against the shop wall -- and install the good servo. The strap was made up. Hobbies are great stress relievers!



The newly installed servo is tested after being cinched down with the common brass strap used to hold all three servos down securely on the device tray.

Note that two of the pushrod horns have already been popped off their servos and those pushrods pushed well aft. The after ends of the pushrods are now well clear of the after face of the motor-bulkhead, this to permit application of a torch flame without damage to the motor-bulkhead itself.



In order to pull the pushrods out of their respective seals I had to clear the magnetic couplers from the after, wet side of each pushrod. I applied heat to an extended pushrod with a torch till the CA holding the magnetic coupler failed. With a little care, by pulling the pushrod aft as far as possible, provides enough distance between torch flame and motor-bulkhead to prevent damage to both motor-bulkhead and magnetic coupler, as you see in this picture.



The bare pushrods were then pulled forward and clear of the seals and motor-bulkhead. If need be, to protect the after face of the motor-bulkhead from flame, a wet hunk of rag would be used as a heat-sink/flame barrier.



Popping out the old, single O-ring, pushrod seals was an easy mater as they are secured and made watertight within the motor-bulkhead by flexible, relatively weak gripping RTV silicon gasket-making 'glue'. You see me using a short length of brass .25" rod as a pushpin to force each seal aft and away from the motor-bulkhead. Easy-peasy.



Swap out of the three pushrod seals was a straight-forward operation and only took a few minutes.



A length of .063" brass rod was used as an 'insertion tool'. I mounted a seal on it, slathered on some RTV, then jammed that sucker in there! Didn't even have to buy it dinner!



Before re-inserting the pushrods, I cleaned them up with a wad of '000' steel wool. Each was then coated with silicon grease.



... and inserted.



The same operation done on 2" WTC's pushrods. As each pushrod was pushed through its respective seal, and the forward control horn made up to the servo, the servo was cycled back and forth with the aid of a 'servo setter'. Any binding between pushrod and seal was reduced by careful bending of the pushrod, up-down-left-right, at its forward end. An acquired skill, I can assure you.



Re-certification included checking for proper motor and drive-train operation. The propulsion battery was hooked up to the ESC, and the servo setter made up to the ESC's lead that normally would make up to the receiver. In this usage the servo setter is used to command motor direction and speed, just as though you were using the transmitter throttle stick -- but without all the hassle of breaking out the transmitter and hooking in the (now removed) receiver.

Testing of the LPB was done the same way.



The WTC mechanics all in working order, the last step to re-certification is a leak test. The equalization valve (a common Schrader, tire-valve), projecting from the wet side of the motor-bulkhead, had its core removed and a flexible hose slipped over the valve body. This permitting me to blow air into the cylinder. The WTC was immersed completely in water as I blew into the hose and looked for air-bubbles escaping from the system. Most leaks result from gaps between a seal body and bulkhead -- these are fixed by dabbing a small amount of RTV sealant over the offending area and drawing a suction on the test hose to draw the sealant into the void. A few minutes later the water test is repeated to affirm a watertight system.

And I'm done.

[Das Boot]

Then pay close attention!

I got your attention.

[He Who Shall Not Be Named]

This is my next boat.

Then pay close attention!

[Das Boot]

This is my next boat.

[He Who Shall Not Be Named]

[He Who Shall Not Be Named]

I love this "Old School" stuff David!

If i were only 40 years younger and had the tools, space and the shop and most IMPORTONLY your talent and skills, I would really love to build submarines using your methods!

You are the MASTER!

Rob
"Firemen can stand the heat"

when (and if) the lights go out, only those with 'old school' skills will be in demand. If you can get things done with you hands, you will assume the stature of a frig'n community treasure.

Question: What can you do now without electricity?

Yeah... thought so.

David