Automatic boiler water control pump

[NMRC]

Hi All
I have made up the pump for this project using a small 3/8" x 2" stroke loco hand pump.
It is operated by a 6v motor with reducing gearbox to run at 18revs per minute.
I have yet to do the electronics but realise the gears are very noisy and spoil the image of the boat.
I reduced the stroke but that made no difference.
Putting it on a rubber mat made little difference.
On sponge improved matters more but that became waterlogged during my experimentation so did not seem viable. It did not improve things enough to be the solution.
I have tried a miniature motor/gearbox before but it was just as noisy as well as underpowered.
The boiler pressure is only 10psi.
Has anybody had success in fitting one if so can you advise how ?

Regards
NMRC

[R.G.Y.]

As you probable know pumps are normally worked by the engine itself. How big is your engine?3/4" + 2" seems large to me. My double acting twin with a stroke of  1-1/2" +3/4 bore has a pump 1/4"+5/8" and still has reserve capacity. R.G.Y.

[steamboatmodel]

A "small 3/8" x 2" stroke loco hand pump" is far too large for this type of application. The last one I helped make was 3/16" x !/2" stroke powered by a converted servo.
Regards,
Gerald,

[NMRC]

Thanks guys
the boat is over 5ft long and was given to my father in law in the 1930s.
The engine loosely replicates the original which is a double oscillating with an overhead crank.
Even if there was the room I would not like to alter it from original hence the electric motor.
I did try to use a servo but it was not up to the job.
Even at this size the pump can only just keep up with the usage rate, which might be down to the relavively small amount of water moved on each stroke.I need to check whether I have excessive ball lift or valve seating.
And this is only one of various issues needing addressing!!

[NMRC]

So what am I doing wrong now?
Looking at the downloaded paperwork to visit Maplin's for the electronics for some reason I am looking at the by-pass valve!
Should it not be in the open position normally?
ie the pump is always working but just pumping around the by pass. When the water level falls the servo then closes the valve forcing the water into the boiler.
 

[antopia]

using electronic water control why have a bypass? just switch it off when not needed
If you are using 18 rpm and 3/8 x2" stroke it would fill a 5" gauge loco with ease so I would check
that the pump is pumping under pressure it sounds like not, 10 psi is nothing much to work against
does it have o'ring? do the balls seat?
is the hand pump horizontal?
hand pumps will not work in some orientations 
you can put a 10psi safety valve fitted to the pump with suitable hose to see if it passes water

I would expect to see a 5/32 x1/4 stroke pump for a large boat this would be more than ample for 2"x8" boiler with a single 3/4 x 1" stroke unit.

steven

[NMRC]

Hi all
Since I've been advised the hand pump is too large I,ve decided to invest in a peristatic pump.
I still need the electronics hence the visit to Maplins.
The comment about the by-pass valve was an observation pondering whether anybody had actually made up this up as per write up and how did it work??
I'm also mid way into building the gas canister valve and regulator which is worthy of a seperate post

Regards

NMRC

[derekwarner_decoy]

Hi PD's.......NMRC ...will the baby peristaltic pump be capable of pressure 30 to 45 PSI?.........Derek

[antopia]

hi NMRC,
I have not tried a motor driven pump,I have heard that it is difficult to supply enough torque but these are for
40-60 psi boilers.
I am not sure if a peristaltic pump would be ok,my knowledge of pumps is limited but here is my input
a pump has to deliver a reasonable pressure so if you have 10 psi boiler pressure it has to supply more than 10psi to deliver into the clack valve(one way valve) so assume a few psi more, I would think atleast 10% more.
now there is a power requirement to deliver this pressure so using a small ram there is not much force acting on the
motor but it is still a reasonable amount .the pump I made is for a gauge one loco and it is placed in the tender
on the last axle using a scotch crank there is not much weight on the tender even so it does not lock up and works
too well so it needs a bypass valve,using a motor there would not be much need for a bypass valve,but if it runs continuous then you would need one.
in figures I would be looking at 6v - 12v and a few amps to power a pump
I did read a write up for a gauge one loco using a servo it only just worked but would not sustain the boiler for long as
the power needed was too much
steam boats and small locos are very similar in all respects except the blast pipe, as a boat does not really need one.

if it was me I would make a ram type pump with a scotch crank on a motor with a gear drive this should work and not make too much noise even a small screwdriver would power a pump.
have a look at mb22 in the steam section Malcolm Beak has a pump attached to the steam plant,complete with bypass.
this should give you the idea,its pretty simple mechanics,if you have access to a lathe then you should be able to make
one?.

Steven
 

[NMRC]

Thanks for your input guys.
The peristaltic pump I was thinking about has a 10metre lift which I think is equivelent to about 15lbs per sq in.(tell me if I'm wrong). The rate is 80 millegrams per min which seems a bit on the low side.It takes a current of 300ma at 6v. So it looks maneagable but not ideal.
Your thoughts have put me in the I used to be uncertain but now I'm not sure mode.

Getting on to a more pressing issue one of the downloaded articles by Malcom Beak dated Nov 1989 on control of gas to fire the boiler refers to the article which I think I am using for this water sensor system. 
 { The method of sorting out the water level was described in the Nov/Dec issue of Radio Control Boat Modeller-but if you intend to make one be warned-there were a number of errore that crept in, so for goodness sake also get the Jan/Feb issue which has the corrections in it.}

Since the download has a November/December footer and I have already expressed some concerns over the by-pass valve it looks as though I need to look at this Jan/Feb issue which I presume is for 1989.
Any ideas how I go about it?
The download will also need to be to be modified if there are errors within it.

Regards

NMRC   

[antopia]

NMRC,
my only concerns were,I had to look up what it was,now for the mechanics it squashes liquid so its not a hydraulic pump as such, looks neat though ,so it has to move quite some way to apply enough force to make a pumping action,then it starts again.for steam we seem to see ram type pumps 2 or 3 strokes and its up to 300psi,the other, clacks have a
tendency to leak sometimes allowing some warm water into the pump,this is not uncommon,

I would be very interested to see your results.

being uncertain becomes of designing ones own system, don't ask how I know.

Regards
Steven
model engineering misconception
full size steam locos are 'not' any easier to bulid

[derekwarner_decoy]

Hi PD's.....well no  antopia  "it squashes liquid so its not a hydraulic pump as such"

The concept of a peristaltic pump is that it closes the suction stroke @ the commencement of the tube closure.......& so does not squash .....in fact eg., fruit...strawberies & peaches are transported in their own fruit fluid without damaging the product 

Having said this..........I agree that a [baby model] peristaltic pump is not the ideal concept for relatively high pressures vis... a boiler feed pump application @ 40>60 PSI  ....Derek

[NMRC]

Hi Guys
I did say at the outset that the boiler pressure is only about 10psi.
Now I have bought a pressure gauge I'm going out to the garage to fit it.
The boiler does not have one at present.
Water level was also an inexact science using a watercock which you opened to determine when you had filled it to the right level and another lower down to let you know when the water was too low ie.it showed steam rather than water. Hence my need for an electronic sensor.
But I digress, this lower valve I have removed to fit the clack for the pump.
I now need to make up a fitting to take both the clack and the gauge.

Regards

NMRC   

[antopia]

NMRC,
even gauge1 is inexact for water most gauges do not register correctly so you have to look at performance to judge
how much water is in the loco ,I assume also for a boat?

I use the process of watching for slight water coming out the blast pipe then open the bypass! or it will stop.
then there is a point at which the loco will ride differently that gives an indication water is too low.some people say the
colour of the blast changes but I have never noticed that one.I use a pop safety valve so cannot use that as an indicator.

if your boiler is a large diameter say 3- 4" a gauge glass would read more reliably and you can use this as a water level
sensor,I would have to look it up though not something I have tried yet but I know it works.

Steven

[monarch]

Try Maxitrak-they supply just the thing you're looking for I think.  It shines a light through the sightglass and would give an adequete signal for a relay & solenoid to work well for you.