Topic: Welman ballast bits (Read 11076 times)

bbdave · « **on:** November 28, 2012, 09:06:40 pm »

These are the bits i'm considering getting for the Welman any opinions/advice on suitability etc.?

http://www.ebay.co.uk/itm/281014483451?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649

http://www.ebay.co.uk/itm/390315372150?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649

http://www.ebay.co.uk/itm/390315372178?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649

http://www.ebay.co.uk/itm/RC-Submarine-100-Waterproof-Solenoid-valve-Air-Water-DC4-8v-18v-/271106018125?pt=US_Character_Radio_Control_Toys&hash=item3f1f2d8b4d

http://www.ebay.co.uk/itm/290519261788?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649

Dave

Subculture · « **Reply #1 on:** November 28, 2012, 09:25:34 pm »

Avoid like the plague- the gears are made from cream cheese. If you want a geared pump get a Kavan (best but £25-30), or one of those red things off ebay for about £6-7.

http://www.ebay.co.uk/itm/281014483451?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649

Okay.

http://www.ebay.co.uk/itm/390315372150?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649

Fine

http://www.ebay.co.uk/itm/390315372178?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649

Looks okay, but not seen or used one, so can't comment. Servo pinch valve works just as well and is cheaper and serviceable. Your choice though.

http://www.ebay.co.uk/itm/RC-Submarine-100-Waterproof-Solenoid-valve-Air-Water-DC4-8v-18v-/271106018125?pt=US_Character_Radio_Control_Toys&hash=item3f1f2d8b4d

No problem. Has it got enough volume for the Welman though? Can also use medical feed bags, adapted capri-sun drinks bags- the big 330ml ones with the screw cap are easiest to convert.

http://www.ebay.co.uk/itm/290519261788?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649

bbdave · « **Reply #2 on:** November 28, 2012, 09:46:10 pm »

Quote from: Subculture on November 28, 2012, 09:25:34 pm

Avoid like the plague- the gears are made from cream cheese. If you want a geared pump get a Kavan (best but £25-30), or one of those red things off ebay for about £6-7.

http://www.ebay.co.uk/itm/281014483451?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649

Which red ones? i have seen the Kavan ones i'll see what budget is available. I may try a different bag but have no idea yet what capacity i need yet so will leave that for a while, i'm not even 100% on the WTC size yet 70-80mm most probably

Dave

Subculture · « **Reply #3 on:** November 28, 2012, 09:59:22 pm »

This type-

http://www.wiperblades4u.co.uk/12v-Universal-Washer-Pump-EWP13.html

Ripmax used to sell them, and they were made in France. production has now moved to China, like everything else. Quality isn't quite so good, but should be fine for the bag type system, better than the white pumps anyway.

bbdave · « **Reply #4 on:** November 29, 2012, 08:12:20 am »

Well if i make my own pinch valve i will get the better pump do i need a strong servo for the pinch?

Dave

thegrimreaper · « **Reply #5 on:** November 29, 2012, 08:23:29 am »

On my Sheerline Akula it is recomended to use a ballraced servo opn the pinch valve, and to this effect I agree due to me unwittingly fitting an ordinary servo to my Vanguard which pops up rather too frequently at the moment when checked the shaft on the servo is already drifting off centre.

Regards Mark.

essex2visuvesi · « **Reply #6 on:** November 29, 2012, 08:24:17 am »

This is a good place for neptune spares, I bought all my neptune dive system parts from here for my Sewolf. postage is reasonable and managed to sneak under the customs radar so no taxes :)

https://www.toysonics.com/home.php?cat=876

Davy1 · « **Reply #7 on:** November 29, 2012, 09:36:28 am »

I have had one of the (Chinese) red pumps on long term test here:
http://www.theassociationofmodelsubmariners.com/t286-pumps-geared-variety
and it looks to be OK and always fails safe. Personally I wouldn't trust any old pump off ebay. Too much at stake!
A lot of stuff on pinch valves on the Forum that you should also find interesting.
David

Subculture · « **Reply #8 on:** November 29, 2012, 11:06:49 am »

I made a pinch valve up with a very inexpensive non-ballraced 9 gram servo. So far so good, but I had to use a miniature servo for space reasons. If I'd had more room, I would have fitted a standard size servo. Servos are very cheap from places like Hobbyking these days.

Couple of things to bear in mind with pinch valves. Many of the designs use a ball or rounded off shaft to pinch off the hose, these require more pressure than a pinch valve with a keener edge. I used some copper sheet folded over to make a small radius, nothing sharp at all. This was coupled with some fairly thin walled silicone tubing, which is very easy to compress.

Others have mentioned my hose will end up damaged with this set-up, but I've seen no ill effects to date, and I keep a close eye on the hose. Also worth mentioning that the way you profile the servo arm will make a difference. You want a nice smooth cam action that gradually squishes the hose, not an 'all or nothing' type action.

bbdave · « **Reply #9 on:** November 29, 2012, 10:06:35 pm »

Been looking for pinch valve ideas got a couple couldn't find much on the AMS site probably hidden within the threads i have a couple of ideas to try when i get some bits up together.

Dave

Davy1 · « **Reply #10 on:** November 30, 2012, 10:38:11 am »

Hi Dave,
There is a lot on there - with quite a lot of photos of the different systems. I think it is in the Questions and Answers section but you will find that the search engine works well.
Let me know if you are still having problems and I will find it for you.
David

Subculture · « **Reply #11 on:** November 30, 2012, 10:58:27 am »

Subculture · « **Reply #12 on:** November 30, 2012, 11:00:58 am »

I only made the above as a proof of the concept, but it worked so well I kept it.

Davy1 · « **Reply #13 on:** November 30, 2012, 12:36:02 pm »

http://www.theassociationofmodelsubmariners.com/t380-pinch-valves
Found the link for you, Dave!

David

bbdave · « **Reply #14 on:** November 30, 2012, 03:39:13 pm »

Thanks for that similar ideas to what i was planning. I have some 6mm fuel tube but the bore is very small where can i get some thin walled tube?

Dave

essex2visuvesi · « **Reply #15 on:** November 30, 2012, 04:42:04 pm »

you could try windscreen washer tubing

Subculture · « **Reply #16 on:** November 30, 2012, 04:47:05 pm »

Don't use windscreen washer tubing, it's too stiff.

For thin bore tubing, you can try Polymax. Ten pound minimum order though.

If you're using a normal size servo however, you should be alright with the thicker stuff. I used the thinner tube because I only had room for feeble little 9 gram servo, non-ballraced I might add.

Davy1 · « **Reply #17 on:** December 01, 2012, 08:54:39 pm »

I would only recommend silicone rubber tubing. (And I have never used anything else. We should perhaps have mentioned that in our posts on the Forum but it is the obvious things that don't get mentioned!)

That's because it needs to be easy to squash and have some "spring" in it.

David

Subculture · « **Reply #18 on:** December 01, 2012, 09:41:53 pm »

Picture seems to have disappeared that I linked to. Let's try photobucket-

bbdave · « **Reply #19 on:** December 02, 2012, 09:02:23 am »

I've registered on the AMS forum so will hopefully find plenty on there does the pinch have to be 100% or will a slight bleed be ok?

Now looking for a motor i'm looking for a 12v i was thinking of one of these

http://www.technobotsonline.com/mfa-motor-re-385.html

I don't need masses in the way of performance i already have a speed 500 but think that may be to big or i could go brushless

Dave

Subculture · « **Reply #20 on:** December 02, 2012, 11:08:13 am »

Too small.

500 size motor minimum for a boat that size.

You could have a word with Andy Nightingale, I think he had some 555 motors up for grabs a while back, he might still have one or two.

bbdave · « **Reply #21 on:** December 02, 2012, 11:58:41 am »

I'll stick with the 500 i already have then, it just seems a little on the big side but i'll give it a try.

Dave

Subculture · « **Reply #22 on:** December 02, 2012, 12:25:27 pm »

Depending on the 500 wind you have, it may need a gearbox to drop the RPM.

Your prop size will be about 1.5" diameter. Not sure what pitch you're going for, but assuming it is roughly the same as the diameter, you will want to be aiming at about 4-7000RPM shaft speed.

Davy1 · « **Reply #23 on:** December 02, 2012, 02:25:19 pm »

Gosh, just got back from dropping my sub through a hole in the ice at the Barrow pond. Happy Days!
Yes, the tendency of a pinch valve to leak a little is one of the unintended benefits of the system. It has happened that people have lost their subs only for them to rise from the depths, minutes or hours later.
Try that with piston tank! (Your sub stays sunk.)
Concerning motors, I wouldn't have thought that the 1:1 Welman was exactly a zippy performer so motor choice isn't going to be too fussy.
I find myself using MFA motors more and more. www.mfacomodrills.com Some gearing is a good idea (1:3 or there abouts) and the ones with integral gearboxes are very easy to fit and make chopping and changing gearboxes very easy if you get it wrong first time

David

Subculture · « **Reply #24 on:** December 02, 2012, 03:44:46 pm »

If aiming for scale speed, you're only going see about one knot, as the fullsize speed was reported to be just three knots, which is slow even by midget sub standards.

Not much fun, and I'd be doubtful on the level of control from the hydroplanes at such a slow speed unless you make them larger than scale.

Personally I think a moderate walking pace would look about right for this boat. Should give the hydroplanes enough speed to work efficiently, and enough pace to make the boat entertaining to run. Also will help the model produce a more realistic wash when running surfaced.

You can always throttle back for slower speed.

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Author Topic: Welman ballast bits (Read 11076 times)