1/96 Thor Permit

[Parallax]

Thank you all, it all makes a lot more sense now. It is amazing how much stuff I initially got wrong. I never touched the wheel collars, but that was clearly where I needed to start. Bob I will make sure the valve is seated all the way back before I go any further. I don't think I bent it the arm very significantly and hopefully I have stopped butchering it.

Hunter, Thank you for the heads up on the video, I found it here and I believe that is David Merriman explaining how it all works:

https://www.youtube.com/watch?v=wSqcUBQy1ac

[Parallax]

I recently had my ballast pump burn out at a pool run in Shrewsberry. It looks like the cause is the repeated partial flooding in the WTC. I've had a lot of leak problems over the past few months, and while I am certain most of the issues are of my own making, I would like to move on to a new system.

In the meantime, I would still like to use the sub. While talking with everyone at SubcomEast, the possibility of doing away with the snorkel system and retrofitting the WTC to a pure gas system was brought up. I feel like that might be a very good option, but I need to figure out a few things before I jump on the retro.

I have never been able to 100 percent isolate the leaks. There was a leak coming from the forward end cap due to a weak seal, however using Teflon tape between the cap and the O-ring seems to have effectively stopped that. There had been a small leak coming through the port I ran the antenna through but that has been solved as well. I have done a bunch of leak testing, and I believe wherever it is leaking from is not repeatable with how I am doing the tests. It might be a depth issue, or odd angle, or even a combination of movements at the same time.

So my current plan involves the following:
Completely dissemble the unit, and replace all of the end cap and bulkhead O rings with wider ones, after having milled out the seats to accept larger seals.
Check all servo seals and replace when necessary.
Remove all of the snorkel system components and seal off the ports.
Replace the emergency gas tank with a full sized tank.
Pick up a bunch of fireworks on the way home from next build day.

I will need to figure out what size O-rings to get for both the end caps as well as the servo seals. I also need to figure out where to get an older style gas tank as I know they have fallen out of favor with the community.

[bob the builder]

It sounds like you already have the gas backup device, correct? If so, creating a larger reserve tank for gas is no major fabrication. If you don't have one, I can hook you up and then follow the procedure below.

Just go to your local hardware store and grab some 1" or 3/4" copper pipe and endcaps. Cut the pipe to length (say, maybe 4" or so?). Drill a hole to accept a new Schraeder valve (tire valve), remove the core of of the valve, and solder the body in place. Add a hole for some small brass tubing for your air line connection and solder that in place, then solder on your end caps, screw in your valve stem and you're done! 10 minutes, tops.

Once you have the new reservoir, just connect it to your existing plumbing in place of the smaller emergency blow tank.

For testing, I recommend installing a small piece of brass tubing in the end cap of your cylinder and attaching a length of the same air hose as your gas backup system uses Clippard sells it online or there's lots on Amazon, too. 1/8" OD and 1/16" ID. Once you attach that to your brass tube nipple, you can submerge your cylinder and blow into the hose to check for leaks.

If you really want to do things right, run your receiver antenna into this hose as far as you can get it (it's a pain in the ass, but worth it). This saves cutting your receiver antenna, which I do not recommend at all. Cap your hose when you're done testing and you're ready for the wet!

Bob

[salmon]

While leaks can be frustrating, they can be found. Have you tried to blow air into the WTC and look for bubbles?
If not, the Schrader valve on the endcap will need the stem removed. Then a hose is placed over the Schrader valve and put an awl in the hose that goes to the float valve in your sail. Place the Sub-Driver underwater and gently blow into it. You may want to hold onto each end of the WTC just in case you get too aggressive. If you do not see any bubbles, flood the ballast tank and try again. This will help you determine if it is outer bulkhead seals or inner bulkhead seals. You can try sucking the air in as well. When you create a vacuum, you can clamp the hose closed maintaining the vacuum you created and look for small stream of water coming in. As badly as your motor housing is rusted, either the chlorine from the pool is doing a number on your or your getting a large amount of water in. If it is a large amount of water, the bubbles will show up immediately. I had a leak in one of my cylinders (it was less than a quarter of a teaspoon of water) and when I did the blowing air in, the bubble would form very slowly. It turned out to be a area around the pushrod the silicon to seal it in must have had a path for water to come in. A little RTV rubber and a bit of sucking air in, sealed it up.

[JWLaRue]

It sounds like you already have the gas backup device, correct? If so, creating a larger reserve tank for gas is no major fabrication.

That’s an option that we discussed with Mike during last Sunday’s fun run. I even have all the necessary parts on hand if he wishes to do this.

-Jeff

[JWLaRue]

While leaks can be frustrating, they can be found. Have you tried to blow air into the WTC and look for bubbles?

We helped Mike with a fair amount of leak testing. So far no obvious source of the leak(s) have been found. The amount of leaking has diminished since he wrapped some Teflon tape around the end caps where the o-rings go. However I think the end caps still fit too loosely. We’re going to try replacing the o-rings with slightly ‘thicker’ ones to get a tighter fit.

I’m thinking that during our next SubBuild day we should completely disassemble the dive module and give it a thorough going over.

-Jeff

[Parallax]

Hi Bob, thank you for the information on building a new air tank. I do have a backup cylinder already and I will go this route for sure. I need to take some measurements of my ballast tank to see if there is enough room for a 4" tank (probably). Also, can you run the clippard lines you were referring to through the servo seals with out any trouble for the antennas?

Jeff I am going to order new seals and hopefully they will be here before the next build day. Do you think Erich's file technique will be sufficient to widen the grooves, or should I look into putting the caps on a lathe? I also agree I need to completely disassemble the entire unit for servicing.

Hi Salmon, Jim Butt actually has a aquarium set up for leak testing, and Jim and Jeff walked me through running a hose through the schrader valve to do the leak test. I know we tried the test with the ballast tank empty and filled. We found leaks coming through the forward seal and thought we had solved the leak issues by wrapping the end caps in teflon tape. That said, I do not believe we tried the vacuum test you are suggesting, so before disassembly on the 28th I should run that test as well. This also may sound like a dumb question, but how do you repair a seal with rtv while still allowing a push rod to operate through it?

I still believe most if not all of the problems I am running into are because my inexperience at the beginning. For instance I had a lot of flooding early on which is why the pump is so badly corroded after sitting in the water. I should have been a lot more proactive about the leaks themselves. Finally, at least some of the leaks have been because I did not use a checklist before operating the sub, and would then occasionally forget to check to make sure everything was working properly before use.

[salmon]

Parallax, sounds like you have good help already. Jim and Jeff both are knowledgeable and experienced. If the leak is actually coming from the seal itself (o-ring) and not from around were the seal is installed, then it needs to be replaced. It is pretty easy to do if you need to.

As far as not following a check list? I have done that. Flooded my WTC more than once.

[JWLaRue]

Jeff I am going to order new seals and hopefully they will be here before the next build day. Do you think Erich's file technique will be sufficient to widen the grooves, or should I look into putting the caps on a lathe? I also agree I need to completely disassemble the entire unit for servicing.

My preference is to use a lathe as it will yield a better, more consistent groove than doing it by hand. Worse case, we use a file and be careful.

-Jeff

[bob the builder]

Linkages in a SubDriver are 1/16". The Clippard hose is 1/8" diameter. So, no. You can't run the hose out the linkage seal. I'd go with a much larger hose, pull out the core of the Schraeder valve and slip the hose over the entire valve stem. That will make it much easier to run your antenna down the hose, too.

[Parallax]

Hey Bob, thank you that makes more sense to me now. Using the valve stem certainly sounds like a better idea then how I am currently running my antenna through the aft end cap. Also do you know what the inner diameter or cross section size is supposed to be on the 3" sub driver cap and bulkhead O-rings? I need to make a decision on how much oversize I want on the cross section of the replacement rings.
Jeff, I might need to go the file route. My buddy Paul has a machinist lathe but I am not sure I will have time to head to his place before the 28th, and I have not yet ordered the new rings yet.

[eckloss]

Jeff I am going to order new seals and hopefully they will be here before the next build day. Do you think Erich's file technique will be sufficient to widen the grooves, or should I look into putting the caps on a lathe? I also agree I need to completely disassemble the entire unit for servicing.

I actually made some progress on my end caps. Before I explain it, let me just say that I absolutely suck at drawing up things in CAD. I've never really solidly learned any software. My skills are beyond basic. Having said that, I was able to finally figure out how to put a concave gouge around the outside for the o-ring instead of a flat channel. They seal much better now. A much better fit for the o-ring. Now I shall eat cookies and celebrate my level of genius

[Ralph --- SSBN 598]

O-ring grooves have been square notches for a reason.

When the o-ring is compressed in a square groove, the o-ring material has some where to spread out in to.
The o-ring when compressed should spread out and touch the bottom of the groove and both sides of the groove but still let the o-ring spread in to the bottom of the groove corners.
This gives the o-ring 4 surfaces to seal to.

An o-ring in a round groove does not let the o-ring spread out so all the compression is above the groove and usually between the two parts needing a seal.
This can cause the outside part to damage the o-ring.
The o-ring can not compress in to the void spaces so it exerts pressure on the outside part and can distort this part or even break or crack it.

A round o-ring groove also requires the gap between parts to be larger to allow the o-ring some where to distort to.

A round groove vs a square groove requires much more force to get the parts to go together.

[eckloss]

A round groove vs a square groove requires much more force to get the parts to go together.

I have to disagree. In using both square and round grooves, my own experience is that the rounded groove provides a much easier fit and a more consistent seal. I do understand though what you are saying about more room to spread out. In my observation with the rounded groove the ring spreads more outward onto the inside of the cylinder, sealing nicely.

[Ralph --- SSBN 598]

I understand and have myself made rounded o-ring grooves.
I always come back the square groove.

The o-ring was patented in the 1890s with a trapezoid groove having soften rounded bottom corners.

O-ring manufacturers have tables showing what size the o-ring groove should be for a given o-ring size and material.
I have never seen a table with rounded bottom grooves for o-rings.
Example table form manufacturer