OTW Design WTC (Dive Components)

[corsaire]

Has anybody had experience with OTW's WTCs ?

I've read these don't use propel gas,what then? Their website is not too explicit, and most importantly do they back their products with good tech support and
customer service?

Which module or unit could be suitable for a model such as the Akula II for example?

Thanks

LeCorsaire

[sam reichart]

I had one of Bob's original WTC's in my Type XXIII. that one used an onboard compressor to allow the ballast system to move water in and out. His current setup uses a pump system... plenty of folks on here can give you details about them... Bob is a top notch vendor; you won't find yourself stranded if you have questions or need parts. I couldn't recommend him enough.

[JWLaRue]

I have several of the OTW dive modules. All continue to work flawlessly. The OTW dive modules come "almost ready to run", meaning that all you need to add are servos and the radio receiver. Speed controller, pitch controller, ballast system management electronics, pump and solenoid are all included.

This is a pump-based ballast system that uses a pump to move water into and out of the ballast tank. The ballast tank is sealed, except for the plumbing to the pump. When water is pumped into the tank, the air inside is compressed. A solenoid is used to prevent the water being expelled due to the higher internal pressure when the pump is not running.

If I recall correctly, these modules come in two diameter sizes (110mm and 90mm....roughly 4.33 and 3.54 inches) and Bob will customize to length (within reason, of course....there needs to be room for all the parts!).

As for customer service, OTW (Bob) is top notch for both his hull kits and dive modules. Delivery has always been either on time or earlier. (usually earlier) Any questions that I have had have always been answered quickly.

-hope this helps,

Jeff

[corsaire]

I understand OTW uses rubber boots (glands) as opposed to the 1/16" push rod seals commonly used in most sub applications here. Are these rubber glands effective at all?

[JWLaRue]

As I stated in a prior post, these dive modules work flawlessly.

As to those rubber boots, they work very well. Unlike the pushrods seals you are referring to, you do not need to ensure that the pushrods stays as close to perpendicular to the axis of the seal. The boot allows for a lot of leeway of side-to-side motion.

-Jeff

[sam reichart]

those rubber boots were awesome and work flawlessly, unless you're careless and poke holes in them with the pushrod (I won't mention any names...)
;-)

[bob the builder]

I just finished trimming up one of Bob's Type VII kits. There is a section in there that shows the cylinder undergoing leak testing in my pool if you want to watch:

The cylinders are pricey.. no two ways about it, but they're bulletproof and work very well.

[corsaire]

It really sounds like an excellent sub module, I wonder how the "guts" in the dry section seals against the water, "O" rings?

[JWLaRue]

Correct, O-rings on the end caps.

-Jeff

[bob the builder]

Bob's design is nice in that once you release the pressure on the seal with the thumb screws, the whole thing just comes apart. With the seals on some of the other cylinders out there sealing on the inside face, it can be hard to get the end caps in and out sometimes, and often results in chipped or broken resin end caps.

[Guest]

You can use air pressure. A single light stroke of a bicycle pump is sufficient to pop caps off quickly and without damage. never use canned or high pressure air though, unless you want your caps embedded in the nearest wall!

Regarding the OTW system. Jeff mentions that the ballast tank is sealed. I have only messed with one of these once, a unit that was built for their Type VII kit. The tank was vented above the probes, so that air is compressed in to the dry spaces. This reduces the pressure the system runs at, and allows more of the tank to be filled. The pump used was a modified shurflo unit. This uses a slinger disc, and the manufacturers state 15psi maximum for this pump- at that pressure flow rate is close to nothing so it really operates best at pressures up to about 10 psi.

For a completely sealed tank system you need at least 15 psi for a half filled tank, and over 40psi to fill it to 70% full. Sheerline use such a system but they use centrifugal pumps, geared pumps also work. The ballast tank has to be very stoutly constructed, as the forces on it are considerable.

[JWLaRue]

According to Bob back last year, he moved away from the vented ballast tank design. Let me go check with Bob to see what the current design is.

-Jeff

[Guest]

Okey dokey.

[JWLaRue]

Okay....here's the scoop from Bob:

"Our standard system is still vented but we can supply a non vented system which works just fine. All the 3.5 inch specials were non vented."

So my bad for conflating the two together!

-Jeff

p.s. I world like to note that all of my OTW dive modules are of the vented type and work great.