RCABS and seals

[adriaticsea]

Hi All,

I've read an old discussion on the board with the topic on RCABS and seals.
It was advised to change the normal O-Rings in the Subtech seals with X rings, but I didn't understand a thing too well...I'll build the watertight fittings myself, do I have to use X rings to seal the propeller shaft exting from the wtc or I can also use a sealing ring or "Simmerring"?
Thanks in advance,
BEST REGARDS MAURO

[turbobearcat]

Hi All,

I've read an old

Hi All,

I've read an old discussion on the board with the topic on RCABS and seals.
It was advised to change the normal O-Rings in the Subtech seals with X rings, but I didn't understand a thing too well...I'll build the watertight fittings myself, do I have to use X rings to seal the propeller shaft exting from the wtc or I can also use a sealing ring or "Simmerring"?
Thanks in advance,
BEST REGARDS MAURO

I've just started to dust off my Kilo sub w/ the Dave W WTC, I know the seal alone keeps the water out but applying vaccum
inside the WTC will cause a leak from what I am told. I haven't had
alot of time to play for the past two months due to work and ready my cars for a Shelby Dodge carshow in Cincinnati this year which after next weekend I can get my other projects rolling or diving again.. I'm thinking over-engineering it and use both..but my other plan has been build two WTC that is separate from each other
and that way we don't run into the seal issue.

any takers on this idea?

then again you can always place the motor in the wet!


Mark

[anonymous]

Just replace the seals with

Just replace the seals with standard hardware store seals and your done. I did this on all my subtec seals that are using the RCABS system. No leaks.

Steve

[skip asay]

Here’s a perfect example of

Here’s a perfect example of the “power of the press”. One person had a problem with a SubTech seal, fixed it, and now too many believe that this “fix” is a necessary modification.
No, I am not “attacking” Dave Welch in any way. We discussed his leaker and the “fix”. This was well before Dave had any thoughts of producing WTCs so I assumed that it was a one time deal, which was almost certainly a result of less than adequate quality control during the manufacturing process. Dave’s been a good friend and customer for many years and the seal he had the problem with was most likely old enough that it had been hand machined rather than the newer ones which are CNC machined. It’s also very possible that the linkage rod passing through the seal was not up to snuff and needed the extra pressure that’s inherent with standard O-rings. That comes from personal experience with one of my own boats.

The seal insert used in all SubTech seals is V shaped (with the open part of the V facing the water). This design seals better as the outside pressure increases as from an increase in depth. What happens is that, as depth increases, the pressure DIFFERENTIAL between the nominal atmospheric pressure inside the pressure hull and the water pressure outside the pressure hull increases. Creating a vacuum inside the pressure hull does exactly the same thing. The initial testing, before I went into production, was to put a servo and link as well as a motor with a shaft (to test both linear and rotary sealing capabilities), inside a small test hull and then pull a high vacuum inside that hull before dropping it to the bottom of a 10 foot deep pool. I used the vacuum to simulate a depth greater than the depth of the pool. After about an hour on the bottom, it came up without a drop of water. Since then, I’ve been informed by many customers that they’ve had their boats far beyond any reasonable operating depth with absolutely no water coming in. I have at least 2 customers who’ve used these seals in home built tethered ROVs which have been down over 50 feet with no water! Think maybe they can take the pressure (differential)?

Skip Asay

[anonymous]

Skip. Thanks for the update.

Skip. Thanks for the update. Although I've never tried the seals provided in a vacuum RCABS system I'll sure give it a shot next time.

I've been down 10 ft. easy with your seals on a non RCABS set up and not one drop.

Sure makes sense about what you has to say about the seals though.

Thanks,

Steve

[bigdave]

Hi Skip,
Sorry for causing

Hi Skip,
Sorry for causing any confusion on the seal but all the ones I have tried (old and new) have leaked in the small WTC. I know as the vacuum builds inside they are supposed to seal better. But in my testing I have not found that to be true, and I don't claim in any way to be an expert in seals. I felt I had to pass on what I had noticed in my testing to the ones who used my WTC. I think the problem is there is such a small volume of air in the WTC that the pump develops a lot more vacuum than it a WTC with more air volume.
You know I would never attack your former products in any way. I have never stated this problem as being a fact, just an observation on my part. This is not the first time I have been told I am full of ****! Ha Ha! Again I am sorry my friend. Dave.

[Guest]

I think Dave may have

I think Dave may have the answer to his unique problem with the seals in his small WTC's. I use a larger volume (more air available, less vacuum) WTC for my models, and have never had a leak problem with unmodified Subtech seals using the RCABS. Use the SBS seals as supplied. Follow instructions to prevent burs or irregularities on pushrods, and use a drop of oil. If you find a leak, replace the flexible seal with Subtech replacement parts. If that doesn't solve the problem, and you decide to use "O" rings, you will probably solve the leak, but may also have more friction and reduced run time.

[adriaticsea]

Hi All,

thank you very much

Hi All,

thank you very much for all the replies, it seems to me that, considering that I'll build a quite large WTC (11"lenght, 3.00" diameter) I can go with the standard and non modified Subtech seals.
Now, I live in Italy and here is quite difficult to find idustrial shapes (rods/tubes) in american measurements...I've purchased a 4mm brass rod for the linkages and a 4mm anodised aluminium rod for the drive shaft.
I know that subtech pushrod seals are designed to seal a 1/8" rod, wich is a bit smaller than 4mm. Will they do a good seal on a larger rod too?
The subtech rotary shaft seal is designed for a 3/16" rod, wich is about 1mm larger in diameter than a 4mm rod. Will I have problems in sealing this smaller shaft?
Thanks in advance for the help,
BEST REGARDS MAURO

[adriaticsea]

Hi All,

I'd like to have

Hi All,

I'd like to have some more infos on SubTech products...it would be very useful for me if someone could answer to the questions I wrote on my last post.
I tried to contact Pandan Model Boats (Official European SubTech dealer) to collect some infos and prices on SubTech products, but I got no replies. I read on Pandan website that there has been a shift in the direction of the model company, but they also said that, starting from June 6, everything would have returned normal.
I emailed Pandan about two weeks ago on June 10 and got no replies...I'd like to know if someone knows something.
I need the seals in order to complete my WTC (you know...going without linkages and shaft seals isn't a very smart idea... ) and I'd like to have them here as soon as possible.
Thanks in advance for the help!!
BEST REGARDS MAURO

[drdave]

Skips seals work well without

Skips seals work well without modification I have had the same seals on my Scamp now for several years and during that time my boat has been at average depth of 6 to 8 feet down and one time in a Quarry at 40 feet and it alwyas comes back up without water in the WTC Dr Dave

[Stephen Vick]

Hi Y'all,

I will add my

Hi Y'all,

I will add my very recent experience to this thread. First; My S-33 uses both subtech seals (for the power switches) and Small World Models style O-ring seals. both perform very well however.... I have found that with the WTC under vacume any slight imperfection of shafts debris on O-rings etc... can cause a leak. I was never so sensitive to these details before, My WTC was leaking and I was losing my mind trying to find the source. I stripped it down to parade rest, cleaned everything, oiled and greased everything and Viola! no leak.
MY cylinder is 3.75 OD and has two dry spaces of 7.5 inches long each (not counting the end caps). Once all the electronics , batteries so on... are in, it has just enough volume to inflate a standard Blood pressure cuff bladder. I know it is pulling a nearly perfect vacume.
So it is my opinion that the question is not whether or not a given seal works properly, but how clean is the installation. I would say that my QA of a WTC has to increase tenfold to avoid leaks.
On the bright side RCABS is so slick in operation (and cheap) I love it. I think I will retro fit my Type II with this set up.
I Hope this helps.
Steve

[adriaticsea]

Hi All,

DrDave and Steve, thank

[color=#000000]Hi All,

DrDave and Steve, thank you very much for sharing your experience with SubTech seals. I'm now convinced that, considering the quite standard volume of my wtc (3" diameter and 10.5" lenght) the Subtech seals will do a good job, and I'll take care of their manutention as you suggest Steve.
The problem for me is different though]

[JWLaRue]

Steve brings up an excellent

Steve brings up an excellent point about needing to keep the shafts clean.....that's why I have taken to using stainless steel rods for my servo shafts. This eliminates the ongoing maintenance required to keep the brass clean.

-Jeff

[Stephen Vick]

Hi,

The subtech seals are machined

Hi,

The subtech seals are machined to very close tolerances, 1/8 inch for pushrods and 5/32 for shafts, so the answer is (in my opinion) No they won't work for metric.
if you want to use them (which is a good idea) Order the proper rod and tube from Ships and Things (or the other suppliers). I can remember trying to find 1/8 inch rod in Spain once, it was impossible, but now with the web nothing is impossible.
Good Luck,
Steve