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[benjaml1]

On the subject of the Model Boats water level detector I built one which worked ok but was worried about the long term effects of dc current passing through the water and possible plating/erosion of bushes in the boiler etc. My unit uses ac to avoid these problems.

Can distilled water act like an electrolyte ??

[TAG]

Distilled water does not act as an electrolyte but then one cannot detect its presence by the Model Boats water level detector. The boiler water must have some conductivity for this system to operate. Deminerised water is pumped around high voltage electrical converter equipment for cooling purposes.

[benjaml1]

Distilled water does not act as an electrolyte but then one cannot detect its presence by the Model Boats water level detector. The boiler water must have some conductivity for this system to operate. Deminerised water is pumped around high voltage electrical converter equipment for cooling purposes.

Thank you for that.... A capacitance probe would work ??

[TAG]

Yes, a company in the USA made a water level detector (based on capacitance measurement) with a neat water pump mainly aimed at the model railway fraternity but when I enquired about buying one I was told that they ceased production as they were losing money on it.

[benjaml1]

Thanks... 

[HS93 (RIP)]

Thanks for the comments on measuring gas tank pressures. This is my first venture into using a tank. Up to now I have been using gas canisters in my steamboats. I have been modelling at 12th scale but my boats are getting heavier and heavier with age. I am scratch building a 24th scale TID tug but getting the steam plant in has got quite challenging.The gas tank is close to the burner and fitted to a subdeck in the bows, pictures attached. The gas tank "plugs" into the sub deck and has underneath it's base a slotted copper heat shunt. The fixings are spring loaded so the shunt can be slid up to or retracted from the back of the burner. I think that a pressure gauge is essential when warming gas but as I was strapped for space and bushes I ended up using an adaptor to attach the gauge to the tank after filling. I agree with bunkerbarge I do not like the Roson valves.

On the subject of the Model Boats water level detector I built one which worked ok but was worried about the long term effects of dc current passing through the water and possible plating/erosion of bushes in the boiler etc. My unit uses ac to avoid these problems.

I like the look of your water pump, have you any more info I am at the moment trying to make a servo driven one to go with my water level gauge kit (I think it came from you) any help would be appreciated.

Peter

[Bunkerbarge]

I actually have one of the capacitance units at home, the guy was based in Orlando and I bought one off him a couple of years ago.  I've not yet had a really good play with it but the thing I find most interesting is the fact that the pump is driven by a servo.  If you can wait a couple more months I can take some pictures for you but I'm afraid I'm away until then.

[Bernhard]

hi...I have one El pump from Regner,,, http://www.youtube.com/watch?v=Loy2qdXYaCk   and one from Usa they dont make eny more?  http://www.home.earthlink.net/~bfindus/   i use that in my Lady Jane...

Bernhard

 regner Ebay    http://cgi.ebay.at/Regner-20220-RC-Speisepumpe-Neuware_W0QQitemZ270523446323QQcmdZViewItemQQptZDE_Modellbau_Modelleisenbahnen?hash=item3efc743433

[HS93 (RIP)]

I want to make my own,so any info would be great, especially valving and weather they use a return spring on the valves , if they are ball type etc

Thanks

Peter

[kno3]

The Regner pump uses tiny disc valves with springs.

[HS93 (RIP)]

The Regner pump uses tiny disc valves with springs.

thanks

Peter

[TAG]

Peter
Have quite a lot of info on pumps but need to do a bit of digging, bear with me. The pump in the pictures is an SVS unit (no longer made) the description stated it would pump about 15cc/min at 3bar, max pressure 4 bar but proportionally less volume. Its critical dimensions are 5/16" ram dia by 5/16" stroke I reckon it is near its limit pumping against 3 bar taking 0.4amps at 4.8v. the trouble with servos they have a limited speed and torque unless you buy an expensive one. I have just built a servo driven one using a Hitec servo with Kevlar gears but the best speed obtainable was 60rpm at 6volts. It was not a great sucess so have parked in the to be looked at another day draw. I have to confess that I usually buy pumps from a model engineer supplier then purchase a motor/gearbox unit and do the engineering to make it into a practical unit. I also threaten to make the next pump myself! Before buying the motor/gearbox it is useful to work out max torque required this being a combination of max pumping pressure and stroke, speed requirements are dictated by pump swept volume and how much water you want to pump.
You are right your water level detector was purchased from me.
I am a new boy to MBM and as we seem to have exhausted gas tanks do we need a new topic headed pumps?
Tim

[boatmadman]

Tim,

Could you let us have some info on your water level detector please?

Ian

[Bunkerbarge]

Topic split to seperate the water feed system posts from the gas tank thread.

[TAG]

Peter
I promised you some info on feed pumps, the one you saw on my post was a commercial unit from SVS (no longer trading). It is driven by a Futaba S3001 servo, it has a bore and stroke of 5/16" (8mm). SVS stated it would pump 15cc/min against a pressure of 3bar or reduced output at 4bar, current consumption is 400mA at 4.8v but is quite noisy on the down stroke. The first unit built was using a commercially built pump from a model engineering supplier, two bevel gears, a RS components motor gear box and put it all in a suitable frame work. It is interesting that SVS and I independently came up with the 8x8mm bore stroke combination driven at the similar speeds but different torques. Futaba servo 4.1Kg/cm and mine at 12.5Kg/cm mine runs easily (no noises) at 3bar 320mA at 6v.
As you want to build your own pump Model Engineer mag is running a series on an updated version of LBSCs Rainhill 3.5" loco and guess what the pump is 5/16x5/16". The construction of this pump features in ME mag 9 October 2009 so it should be easy to get a back number copy.
If you are wondering about sizing the motor/gear box to the water pump I can run you through the calculations that I use. You asked about valves, lifts etc. the best thing I can quote is from K.N.Harris's book 'Model Stationary & Marine Steam Engines, "As a very rough guide for engines with cylinders up to about 3/4" bore a pump with a swept capacity of about 1/80th that of the steam cylinder"........"valve liftshould be restricted to a max figure of 1/6 the diameter of the ball" 1/32 seems a popular figure. I use Nitrile rubber balls or for high temperature Viton.
Tim   

[Circlip]

J.P. Bertinat did two versions for the "Borderer" and "Marcher" engines which would also be suitable.

  Regards  Ian.

[HS93 (RIP)]

thank you for that info,at the moment I am paying with a few ideas one is an old Cheddar pump, the other idea is a part home made pump, using two commercial clack valves one in reverse and the third is a full home made version all are going to be servo driven i have got hold of a few cheap full metal geared ballraced HD servos for  test, I can distroy these at the price off them, I am trying to use 4mm for the ram as that is what has been used in the cheddar one I have, but I will bear in mind what you are using, I hope to make it so the ram is screwed in to the base and so can be changed to experiment, ill let you know how I get on

peter

[TAG]

Ian
You asked about my water level detector systems. I started using vending machine chips in the 80s, see Model Engineer (ME) Vol.195 No.4261 and moved on to more sophisticated electronics see ME Vol.198 Nos. 4920 and 4292. Here is a summary of the present units, an insulated electrode is fitted in a spare bush on the boiler at the required working water level. Easier said than done but there are ways around this if the bush is not in the required place. The electrode is energised by an ac signal (to avoid erosion/plating problems) and the chip that produces the signal detects whether water is shorting the electrode or not. The output from this chip is passed onto a PIC chip to carry out logic processing. A PIC chip is a programmable unit. The action of the detector circuit is as follows:
When water is detected at the electrode the the output to an electrically driven feed pump is nil or servo operated bypass valve remains in the closed position i.e. the quiescent state. When the water level drops below the electrode the feed pump starts or the servo valve changes over. Pumping continues until water is detected, this starts an on board timer (in the PIC chip) and pumping is continued. When the time expires pumping is stopped and the unit returns to the quiescent state. The reason for the time delay is to prevent hunting, the unit has four user selectable time delays to suit different pumping rates. One can also reverse the servo throw. It also has an alarm which detects pump failure although it has been pointed out that there is a bug in it. Unfortunately I presently have no one to reprogramme it. The unit has two LEDs which the status of the unit.  I now have a version which uses an optical unit for use on the water gauge glass instead of the electrode in the style of the old Cheddar Models ABC unit. This latter version has been proven but is at a stand still as the person who did my PIC programming died this year (any volunteers?). As a side issue the 5v low dropout voltage regulator on the PCB can act as a BEC for R/C.
 

[boatmadman]

Tag,

Thanks for that, very interesting.

If you get any takers for PIC programming, keep us informed, I am sure there would be interest in an optical level control unit - I am1

Ian

[around]

TAG,

I have also built my own PIC controlled, servo operated water feed system for a D10 steam plant (TID tug). 

I would be more than willing to look at the firmware in your existing unit and sort out any bugs/performance issues.  I also do surface mount PCB design and manufacture.  I will need to see the firmware listing, the model of PIC, the schematic showing the inputs to the PIC and a description of the issues.

Cheers,

Adrian

[TAG]

Adrian
Thanks for offering to help on the PIC programming. I will PM you in the next few days and give you a summary of where I am at, the problems and what I need to move forward. I can give you all the information you need but a lot of it is on paper.
Tim