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D&E Mini. WTC 3.5 " - Questions

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Postby MIT » Sun Jan 18, 2004 1:16 pm

I am looking for some explaining from people that own a D&E miniature 3.5 WTC.

I got this, fully assembled, so I am going through the motions of checking everything out. Several questions stick out that I would like clarifications.

1. D&E WTC's appear not to have end cap tightening screws. (???). What I am talking about are screw rod assemblies to pull both ends together tight. As an engineer, this puzzles me a bit. Does hydrostatic pressure do a good enough job of keeping the end caps on ?

2. The vent valve / Equalization valve. This relates to No. 1 in way. I understand what this valve's purpose is. But, if one where to siphon air OUT of the compartment, the negative pressure would help make a better seal with the endcaps. Any comments on this one ?

3. Ballast section. This particular WTC has two sections. It is identical to the one shown in Issue #40 of the Sub Report used in a 1/96 Ohio class sub. It has two compartments. One equipment, the later ballast with an adjustable piston on the ballast used to help with establishing the volume of water to be used. There is a float foam assembly that is connected to the propel / valve tank / servo actuator (what I call in a nice way, the toilet bowl system). My question is: with no vent valve, how does the D&E WTC 3.5" ballast section flood ?
There also seems to be a set screw on the top of this WTC with some potting silicone. It looks like a tension adjustment screw.

I hope someone or some folks can answer these for me.

This WTC is very nicely designed by the way. I particularly like the unique adjustment solution of the APC. Nice job by Dave !

Thank you

Nick



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Postby Britt Boyette » Sun Jan 18, 2004 2:17 pm

Did you read the instructions?
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Postby MIT » Sun Jan 18, 2004 2:35 pm

No, instructions came with it.

I hoped my fellow subcommittee members could just answers these very basic questions, so I could start some water trials.

Do you have an answer to any of these please ?

I would also like a discussion on #2. Instructions would not cover this for sure.

Thank you.

Nick
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Postby sam reichart » Sun Jan 18, 2004 3:32 pm

NIck- CAVEAT- this is how it is on my WTC 3.5...

1. O-ring pressure on th eend caps has always been enough for the cylinders I have. Just remember to bleed off any internally trapped air by depressing the valve on the end cap.

2. I'll leave this one to the more learned than I...

3. that screw you see on the top of the WTC with the silicone sealant is what allows the ballast tank to flood. When you throw the stick on the transmitter left or right, it either depresses the valve inside the tank to allow Propel to escape, or it moved the valve that's sealed against that screw at the top of the tank. If that opens, water will flood in from the openings at the bottom of the ballast area. So adjusting that "tension" screw as you described it will allow that valve to seat more correctly on the top of the tank.

hope that helps some.

regards,
Sam
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Postby JWLaRue » Sun Jan 18, 2004 3:42 pm

....I'm curious.....

What APC adjustment ability?

-Jeff
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Postby MIT » Sun Jan 18, 2004 4:16 pm

First off,

Thank you very much Sam, for the info. That helps alot.

The APC in this WTC is mounted such that it cradles against the middle bulkhead.

The APC cover is off, and two holes are drilled in the sides of the remaining bottom case. These holes allow for a "C" shaped brass wire to be insert into these holes such that the APC can pivot like a swing. The back side of the "C" brass wire is supported (glued) to the middle bulkhead. The APC can pivot back and forth (fore and aft shipwise). On the exposed IC (this is the cool part) a brassthin plate has been siliconed on, such that it does not make contact with the IC's exposed pins. The plate is slightly longer than the IC and the extra length is bent 90 degrees up forming a servo horn with a hole in it. A brass control rod runs from this pivot support plate to the front end cap, exiting through a linkage seal, where and adjusting screw assembly allows one to adjust the relative angle of the APC to ships lengthwise level from "outside" the WTC. A simple thumbscrew assembly secures the adjustment.

Very nice idea !

I will post a picture of it.
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Postby JWLaRue » Sun Jan 18, 2004 4:41 pm

MIT,

Many thanks for the APC adjustment description. That's what I thought it might be.

It's nice to see that Dave isn't bashful about 'borrowing' good ideas from others so as to enhance his products. :;):

-Jeff
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Postby MIT » Sun Jan 18, 2004 4:58 pm

I presume that you are the "inventor" ?

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Postby JWLaRue » Sun Jan 18, 2004 7:21 pm

MIT,

Nope. A different member of the SubCommittee came up with it originally. But I used the basic concept in my WTC and remember showing it to Dave several years ago. His comment was something like "that's a much better way to adjust the APC."

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Postby Sub culture » Mon Jan 19, 2004 9:09 am

You don't really need rods to hold the end caps in unless the WTC has to withstand internal pressure i.e. as with a Piston tank system, or compressed air system. Also if you decide to use the seals in such a way as they butt onto the end of the cylinder (as opposed to sealing inside the cylinder like the D&E designs) then you will need rods to compress the seal slightly.

In many cases friction from the o-ring seals is sufficient to keep the end caps in place. As you dive deeper of course, water pressure will push the end caps in.

Negative pressure in the WTC isn't to be encouraged.
This will more likely lead to leaks than prevent them, because water may be sucked past the seals.

A little positive pressure however, is no bad thing in my experience and it helps to detect leaks before diving your boat.

If you haven't got any yet, buy a tube of good quality silicone grease (I recommend the Servisol brand). Use this on all your seals- it keeps them supple and protects the o-rings from perishing.

Cheers

Andy
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Want to dive your boat in crystal clear water? Then you had better Dive-in- http://www.diveintomodelsubmarines.co.uk
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Postby TMSmalley » Mon Jan 19, 2004 9:37 am

Hi Nick -
Dave supplies a beautiful set of instructions for his WTCs and as far as I know he doesn't supply his WTCs with the APC adjustment device you described. Did you buy it new from D&E or used from another party?

If you want a copy of the instructions, shoot me an email at tmsmalley@yahoo.com - I think you will find them an invaluable resource for the installation, operation and fine tuning of the WTC.

TimImage



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Postby Bob the Builder » Mon Jan 19, 2004 3:00 pm

Here's something that occured to me:

If a WTC is sealed in a cold environment (say lake-side on a cool morning), is run for a while and then taken out and set in the sun, is it possible for the warm expanding air inside the WTC to "blow" off the endcap, or is there insufficent volume or pressure for this to happen? You'd think a black sub hull would get things pretty warm in there.

Just a thought...
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Postby MIT » Mon Jan 19, 2004 3:19 pm

Andy, Tim and Bob

Thanks for your responses.

Tim, I have sent you an e-mail. Thank you for the offer.

The APC was bought from a third party, but the way the whole thing is installed appears to have been done by Dave. Because of the way the whole thing is assembled, someone would have had to have access to the middle bulkhead prior to assembly of the WTC.

The whole thing is too perfect to have been done by a third party. Esspecially since the same brass screws, seals and hardware match up. Maybe Dave can solve the mystery ? Maybe he made a few for trial purposes and decided not to continue making them that way.

I am pretty sure that person I bought this from did not make these changes.

I will take some pictures and send them to you Tim. Maybe you can post them on your website. It is a very nice way to adjust the APC for various subs that you use the WTC in.

With respect to the endcap retaining scheme I was think of making two external clamps out of SS rod (1/4" diam)that would run along the outside length of the WTC and clamp both ends with a "c" clamp assembly, much like "Quick Clamps". This would not affect the water integrity, by avoiding the addition of more holes in the endcaps if one where to run rods internally to the WTC, and would provide the added assurance of a better seal. The clamps would not have to tightened down very hard.

What do you folks think ? Is this overkill ?

Nick



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Postby sam reichart » Mon Jan 19, 2004 5:55 pm

Bob the Builder wrote:Here's something that occured to me:

If a WTC is sealed in a cold environment (say lake-side on a cool morning), is run for a while and then taken out and set in the sun, is it possible for the warm expanding air inside the WTC to "blow" off the endcap, or is there insufficent volume or pressure for this to happen? You'd think a black sub hull would get things pretty warm in there.

Just a thought...

this happened to me a SubRegatta a few years ago with my Thor LA and a WTC3...I would have been fine if I would have remembered to vent the air inside of the cylinder through the endcap valve before I put the hot sub into the cooler water. I just had to dry out the battery compartment for a bit. Embarrassing, but I won't forget again.
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