Darnell RN S class plans

Guys has anyone a set of the darnell S class sub plans/drawings showing the dive system installation?

David

Hi dgp,

To start with, I am sorry I don't have a set.

Perhaps let us know why you want them?

If it is the original Darnell setup - (steam engine/ air pump etc.) You may have problems getting it to work very well - technology moves on. I found this out the hard way if you take a look at the build log I put on here for the Darnell Type XXI.

David

Thanks David, problem is I dont know what Im doing , I bought what I though I could make into a WTC from the chap at MMB, 3x pvc tubes with ends I that I was intending to try and fit it into the S class in a WTC. Looking at the possibility of cocking the whole WTC construction process up with my lack of building skills I then reckoned that I would be better to try and install the dive system as seen in the 'simply submarines' book, hence I thought if I could get hold of a set of the Darnell drawings I would be able to fiddle betwen them and the setup in the 'simply submarine' book.

DAvid

Hi David,

I have just been having a look at all your posts on the S class and I think I can now see your problems "in the round." Do I take it that you have a "working" Darnell S class that you want to "improve"? (I don't see any photos which would help the people on the Forum.)

I suppose the first thing is what improvements you need to make (in priority order):

- Does it keep the water out? (It must stay dry for hours - no small dribbles!)
- Does it move and steer and float level on the surface?
- Does it dive (and surface!)
- Can you easily keep it maintained?

Looking at some more detailed points. The air compressor system you have is one of the more complicated dive systems but can be made to work well. (Paul C is very pleased with it)

Flat hatch or cylindrical WTC? If it is flat hatch now does it leak and can you keep it non-leaking? If you intend to go for a cylindrical WTC do  your MMB end caps seal well in the tube - I have seen some that don't?

I'm impressed by your honesty about your skill level. Everyone is learning all the time and some of us seem to know more and more about less and less!,You have prompted me to put up a "Beginners start here" section today. (My fellow admins have pointed out that we were lacking one.)

David

Thanks David I've taken a couple of pics of the tube, it is 34" long in 3 sections' 90mm dia. Originally I wanted the ability to use the wtc in other subs I wish to buy later on. I thought 3 sections as the model originally had 3 flat top sections build into the hull, first tube would have diving pump second would hold ballast tank and last one would hold the drive equipment.

I will endeavour to have the pics put onto the form ASAP.

David

Hi David

Well the tubes look potentially a good starting point. I take it that the end caps seal well? And yes the centre tube section could be a ballast tank (a bag or vented tank??) - typically positioned under the conning tower.

Using the tubes will mean re-doing everything though. Is that the way you want to go?

Any chance of posting a photo of the model itself to help decide what needs to go and what could stay?

David

Thanks David, I have stripped the original system from the boat, only 2 bulkheads currently in hull, I will attach pics of sub as soon as I get home from work, I was thinking of trying to use a system using the central tube as the ballast tank, pumping water in to flood the tank then reverse the pump to empty it, is there a particular 2 way pump that would be suitable? if so where could I get hold of one?
I was looking at the magnetic drive system for props in one of the associations mags, can you tell me where I can get more info regarding costs etc.

Sorry about all the questions!!

David

Hi there David.

Try your local car accessory shop for a windscreen washer pump, specify a gear pump which
is reversible (some of them aren't)

I recently got one from AFL for less than £10.

The magnetic drive in the magazine was one of my ideas, the rare earth magnets are available from CPC and other places quite cheaply. The Magnet carriers were turned up at work from some spare bits of Nylon.
The assembly is still on the shelf awaiting my next WTC...
Let me know if more info is needed.

John

What sort of water pump system are you aiming for?

You say pump in and pump out, but will the tank be vented or sealed?

If the latter then you need to make sure the tank is able to easily withstand at least 40-50psi, which means fairly robust construction is required.

If you go for a vented system, then there is no real pressure inside the system, which simplified construction to some extent, and also allows full use of the tanks volume, but you won't be able to blow your tank with the boat submerged.

Hi David,

Thanks for the photos (the internals look very similar to the Type XXI I refurbished (See build logs) and are probably best removed - my bulkheads had come become unbonded anyway.

I agree with everything everyone has said so far. You could use a vented tank, bag, piston tank etc. positioned in the centre section pipe section of the WTC. As Swipe indicates, your plastic pipe would not be able to withstand the pressure in a pressure tank system though. I have used plastic pipe for pressure tanks but coated in several layers of glass fibre.

I just wonder if you wouldn't be better off by using a single WTC with 2 end caps? (That's the way I went with the Type XXI).  You just slide everything in mounted on some sort of tray, and this includes the ballast tank. A piston tank in my case. I have also done this using a pressure tank.

I don't know much about vented tank systems but I somehow feel that if you want to use that system you may be better off using your original plan with 3 WTCs. Perhaps someone who favours vented tanks could help here? (I always worry where the air for venting is going to come from. Difficult if you are at the bottom of the pond?)

As John suggest maybe buy yourself a pump and do some bench trials. Pumping water in and out of a plastic soft drinks bottle will give you a feel for the pressure tank system and may frighten you enough to try another system?! As a first estimate, you will need about a pint and a bit of buoyancy - more if you want a really scale waterline. Try to keep the displacement (and weight) of the superstructure to a minimum. (My Darnell had about 1/4" thick resin at the top of the conning tower.)

Magnetic shaft couplings are perhaps not very necessary at this stage. I think most people are happy with oils seals (Simrit etc.)

David

A lot of the water pumps are poor quality these days. If you want to pump in either direction you will need either a peristaltic or geared pump. Centrifugal pumps pump unidirectionally, so you would need two pumps, They don't always make very good pressure but tend to have a higher flow rate than geared style pumps.

Peristaltic pumps can make very high pressure, but they pumps very slowly unless made large, so not a good choice for your boat.

Some older geared pumps used to have brass gears, but most of the modern pumps use plastic, which can be okay, but a common problem with those is that the driven gear loses its bite on the motor shaft.

Kavan produce a pump with lapped brass gears. At about £20 It's a little more pricey than a cheapy from Halfords etc. also it's a bit bigger than some pumps, but it has pretty decent pumping speed and should reward you with good service.

http://www.sussex-model-centre.co.uk/shopexd.asp?id=1283

Yes the "red pump"s were very popular with model submariners for a long time but the build quality went off when they started being made in China. This forum thread gives the whole story:

https://www.theassociationofmodelsubmariners.com/t286-pumps-geared-variety?highlight=pumps

Swipe - that Kavan pump looks very promising. Have you actually used one in a pressure tank system or any other system in your subs? If so any photos?

David

I still have a geared pump in a boat for over 10 Years without any problems.

Its a 24v one designated for a truck and runs ok on 12v.

John.

Thanks Swipe, I will be investing in one of those pumps shortly, is there a store that sells suitable ballast bags? Also could I use normal tubing like model aircraft fuel line material?

Right looking at t'other end of the sub, was thinking of using one shaft from wtc running both shafts using a gearing system, once again does anyone know of a source for brass cogs and gears?

Thanks for all the info again guys

David

Before you part with your hard earned £20 or so, maybe Swipe could say whether he has actually used one or that it simply seems like a good idea?

Do you have to have brass gears?

https://www.theassociationofmodelsubmariners.com/t555-motors-and-gearboxes-from-mfa-como

http://mfacomodrills.com/

https://www.theassociationofmodelsubmariners.com/t1119-technobots-good-useful-supplier

http://www.technobotsonline.com/

Are both good for supplies of gears etc - but probably more in plastic.

Suppliers of ballast bags - you've hit on the main problem. Finding a suitable bag?  Reading around, lots of people seem to have used various medical bags (dialysis etc??) but would you want to trust your sub with them? Maybe someone can offer some actual long term experience of using one successfully.

Hi

I have been having a clear out to-day and one of the things that I came across is the Darnell pump with the motor, would this be of any help??

Hi Fred I would be very interested in the items, just let me know how much you would want for them, anpother question Im afraid whats the best way to waterproof the control linkages and prop shafts at the stern?

David

dgp1957 wrote:Hi Fred I would be very interested in the items, just let me know how much you would want for them, anpother question Im afraid whats the best way to waterproof the control linkages and prop shafts at the stern?

David

Hi
First just p/m me your address, cost just the cost for the posting,

Second you need to talk to Alf Blake with regards to sealing push rod's.

Fred

Thanks for asking some good questions!

You have energised me to move some useful threads over to the Beginners Start Here section. Hope the threads are useful.

For the record, I use Simrit shaft seals and bellows.

David

Where do you buy them from David?

Below is a post David put in another section earlier today.



"Just got a set of O rings from this supplier.

(They also do shaft (oil) seals such as Simrit and also bearings.)

Sensible prices and postage and next day delivery by first class post."


]http://simplybearings.co.uk/shop/index.php?osCsid=bc25a0eff9daea1c50bef28c4c549995[/url]

Guys just to clarify, would I drill a hole of the outside diameter of the seal through the WTC end, glue the seal into the hole then pass the prop shaft through the seal?

David

I have just tagged some more info onto this earlier thread:

https://www.theassociationofmodelsubmariners.com/t266p30-prop-shaft-seals#8709


Hope it helps your fitting. I think that with reliable prop shaft seals you may re-consider putting side by side motors in rather than a single motor and twin props. Twin motors can help in turns a little.

David