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[rhavrane]

Bonjour Tom,
This model : http://electronique-ljm.com/index.php/modelisme/22-cat-carte-niv-o-vap (I have 6 of them) must be calibrated hot, full tube then empty tube, so why not on plastic if the tube is between 5 and 8 mm in diameter.
Example : https://youtu.be/Nl5x1b802nk

[Geoff]

A very interesting and informative post. I have been steaming for nearly 15 years now, and I tend to follow the KISS principle (Keep is Simple Stupid!) - works for me!


There was reference to lagging the "condenser". I don't do this but sight the condenser right next to the gas tank so its just touching. This gently warms the gas tank thus maintaining pressure and a good quality frame. This also addresses the latent heat of evaporation. Basically a liquid is turning to a gas so changing state and needs energy to do this which it sucks out of the surrounding air and hence cools the gas tank!


At the end of a 25 to 30 min run the gas tank is hand warm which is perfect.


I would concur that most "condensers" supplied with engine kits work perfectly but are typically only just adequate in terms of volume. So I used an old "Andrew's" tin which is about 1.5" in diameter and 3" high so can contain more condensate. As mentioned don't forget to empty it at the end of a run as otherwise it blows yuck all over the model - how do I know this!


Cheers


Geoff

[TomF]

Thank you again to all you experts in the field of steam.
The P71 pump arrived yesterday along with the boiler and engine.
Before I discount the P71 pump for use as a water pump I wanted to rig it up to see if it will fill the boiler under pressure.
Is it likely to just work or not work, and could I damage anything?
Thanks again
Tom

[rhavrane]

Bonjour Tom,To my opinion, no problem testing this pump as soon as you install a check valve (otherwise it will never be able to operate properly), at worst, instead of injecting water into the boiler, nothing will happen, thanks to the check valve I mentionned and  the pump will possibly leak if it spins.
I am quite interested by your test, the way you will install this pump and replace its original drive pulley designed for a belt, thank you in advance fo pictures or videos.

[TomF]

Im not sure how I will be testing it yet, I will probably "lass up" an electric motor to drive it.


I would install in boat with a right angle bevel gears so that the pump is in line with the steam plant and not at right angles.
If it works Im going to have to work out ratio of gears to get the reduction right.
This is what I had in mind - if I need a larger reduction I could use worm gears.
Probably keep with brass gears and an open arrangement as shown in the pic.

[rhavrane]

Bonjour Tom,Based on my experience with electric pumps, single acting ones, I would kindly suggest to not exceed 300 RPM.
The one I bought :
https://www.ebay.co.uk/itm/204181251147?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=0as5azlqrci&sssrc=2047675&ssuid=pISQXRDgTXG&var=504764073177&widget_ver=art

[TomF]

Here is a link to the microcosm P71 pump running





https://www.youtube.com/shorts/ye_MNrWhLcA


Sorry but more questions

• How should I lubricate the engine?
• Any suggestions on how I could simulate boiler pressure, without actually connection to the boiler?
• I will need to work out the rpm the pump needs to run at to make a pully wheel from back of the engine to the pump - any ideas or do I need to by an rpm meter?

Again thank you in anticipation.
Tom

[1967Brutus]

You are going to need a MUCH slower motor for that pump.
Your steam engine will consume about 5~15 ml of water per minute and that most likely comes down to less than 30 pistonstrokes per minute.


The engine (assuming you mean the M30 by that) has a displacement lubricator for internal lubrication. refill that one before every run.
External lubrication (rods and shafts) either manual or by wick-oiler.
The pump, just an occasional drop of oil on the moving parts, EXCEPT the plunger. Do NOT oil the plunger.

The only way to simulate boiler pressure is by hooking that feedline up to the boiler, and pressurizing the boiler with a bicycle pump or similar.

[JimG]

Would it not be possible to simulate the pressure by fitting a narrow outlet to the pump outlet. This should create a resistance to flow and therefore back pressure in the delivery. Ideally you would use a machined nozzle with a fine hole but a length of brass or copper tube with the end crushed nearly closed might do. The silicon tube used here however would need replaced as it will just balloon under pressure.
Jim

[1967Brutus]

Would it not be possible to simulate the pressure by fitting a narrow outlet to the pump outlet. This should create a resistance to flow and therefore back pressure in the delivery. Ideally you would use a machined nozzle with a fine hole but a length of brass or copper tube with the end crushed nearly closed might do. The silicon tube used here however would need replaced as it will just balloon under pressure.
Jim

Unfortunately, no... The pressure in that case will only be present during the delivery stroke, but as soon as that ends, that pressure will fall off and be absent during the suction stroke (on a single plunger pump) which has a noticably different effect on the functioning of non-return valves.
In case of a double acting pump the pressure will build up again, but the short period of no pressure has an effect.

This would for example be noticable in that a pump throttled to have some backpressure, will still be able to selfprime or handle an air bubble in the suction line, because no delivery=no backpressre, so the pump will be able to discharge that air.
It will not do that against a continuous backpressure, because the airbubble being compressable, it will not discharge into the delivery line if a pressure is present.

[carlfmiller]

Tom you hit the mother lode of expertise here-- questions all addressed!  Nothing I can add except just a bit of caution about the complexity factor. If you are new to the field seems to me a KISS suggestion is appropriate. IMO what you want is a straightforward install into your launch so you can "see how it goes" and then come back later with enhancements like the water pump, P5 valve, and (didn't Rafael insist?) a whistle. If you get "hooked" as we all seem to be, you'll be building another model soon and into that one you can install a steam plant that has everything and you'll know by then how to handle it all. On your first go-round, be satisfied with 20 minute autonomy so you won't need the "extras".  Everyone does wish you Good Luck and have fun!  -Carl

[TomF]

Thanks, Carl, wise words indeed. I'll get the steam plant up and running next, and take it from there.
Tom

[Geoff]

What I have done in the past is to run the steam plant in the model in the bath and time it to see how long it takes to run out of water, then turn the gas off. In this way you can establish a base line of time. A steam engine on the bench will give a much shorter run time as no load on the engine.


Simplistically I tend to think of a boiler as being able to give so many "puffs" of steam, so an unloaded engine will use the puffs much quicker than a loaded engine, so loaded will last longer.


Its the same basic deal with speed, if you run your engine fast then it will use the available steam quicker, yes more speed but less duration. The corollary is also true.


With a steam engine you tend to need large props which turn slowly for the reasons above.


With my models I typically get 25 to 30 mins per sail on a regular basis and I time them so I know when I need to bring them in to avoid having the boiler run dry.


If you do run the boiler dry just leave it alone for a couple of hours until you can tough it with your fingers. Typically a single flame cannot generate enough heat to damage a boiler due to the mass of copper. Its not at all wise so on one model with a ceramic burner I have a gas cut off valve. On the other which is more cramped which uses a blow lamp burner I use a car windscreen washer pump to shoot a jet of water onto the burner which puts it out.


A dry boiler is not dangerous other than you may set fire to the wood lagging and hence the model. Under no circumstances inject water into an overheated boiler as it will immediately flash vaporise and create superheated steam which will shoot straight up and the shock may damage the boiler.


Its all good fun and I would agree with the other comment - KISS - just get the steam plant into the model to gain experience and if satisfied leave it alone. If not then you can start to get complicated. Initially I would counsel you keep the complications to a minimum until you have gained practical experience.


Steam is fun and you can't beat the smell of steam, hot oil and burnt fingers!!


Cheers


Geoff

[TomF]

Finally getting back to my steam launch, thanks for all the contributions to this post so far but realise there is something I still need to get to grips with "the plumbing".
I have taken the route of KIRSS (keep it relatively simple) and do want to add a water pump and whistle. So the question is where do these get plumbed into the steam plant?
I have made a sketch of where I "think" they should go, and don't know where the return should come from.







Inlet marked with arrow, I think this is normally used to drain the boiler.



Plant layout - I have already made a base from ply covered in aluminium checkerboard, with a brass frame that will drop down into the deck. The pump will be driven from an electric motor and the gas tank (shown facing the wrong way!) and condenser lagged to match boiler.






Showing where I propose to add a "T" piece for the whistle. At the moment the whistle is shown in a temporary position.

[rhavrane]

Bonjour Tom,

Nice project indeed  , I have this plant and it runs quite well : https://youtu.be/TO16806-3pM ==> https://youtu.be/0sdyREhRPj8

As you will install a mechanical pump, your drawing is incomplete, a by-pass valve for return is missing as you can see it on this example :https://youtu.be/QqgnnKakl_o

And "of course", you should have a check valve on the boiler (red on my video) which is absolutely mandatory.

This is the major problem on this boiler, I wanted to install one and didn't find where to put one. Your pump will never operate without one because the pressure of the boiler will be stronger than your pump. Plug the pump directly on the water level is not an option.

This is an example of what is commonly done on boilers built to receive a pump : https://youtu.be/VZVgnLSGGH0

[1967Brutus]

The connection at the bottom of the level glass IS the feedwater connection. It is NOT usable as blowdown, since it does not connect to the lowest point of the body of water in the boiler, therefore will not drain the boiler entirely, and due to it being connected to the level glass, it will also pass a lot of steam when blowing down. This makes blowing down the boiler, to say the least, a risky undertaking.
If an engine driven pump is going to be used, a non-return valve at the feedwater connection is an absolute necessity, but if an electrically driven feedwater pump is used, this n-return valve can be omitted.
For an engine driven pump, the bypass valve connects back to the feedwater tank, for the electrically driven pump no bypass is needed.

My advise would be to fit the whistle as shown in the picture, and NOT in the steam discharge line to the engine.

I strongly advise AGAINST lagging the gas tank, since that will insulate it from any radiation heat. That tank cools down due to evaporation of its content, and it can use ANY heat you can get to it, in order to maintain fuel pressure.

My advise: this tank can safely hold about 60~65 grammes of gas, and using a precise scale when filling, is highly recommended. Anything above 65 grammes of gas presents serious risks when the installation is in a moving object: Sloshing of the liquid gas can cause liquid to enter the fuel line, causing a burner blow-out.
Therefore, allow for the tank to remain easily removable.

The safety valve of that boiler works OK when new, but the ball valve is not stainless, and it will get stuck if not very zealously maintained and tested, which brings the returning task of setting the release pressure.
I replaced mine with a Gravisil ball (5 mm diameter if I am not mistaken), which seals excellent, and remains functional because it does not rust stuck.

The condenser is a bit of an issue, it is way too small and will be filled to the brim within about 15 minutes of operation... You need to figure something out for that or your boat will leave a trail of oil on the pond. Something like a continuous drain or something, collecting the oily condensate into a larger tank.
In my experience, 100 ml should be sufficient for about 1 hr of runtime.

[TomF]

Thank you, Brutus. That is super useful. I also saw your previous post, which answered a lot of my questions.
My idea is to fabricate a removable glass fibre tank that will fit in the forward part of the boat under the deck to collect the overflow from the condenser tank. I'll create a "take off" point near the top of the tank using a union fitting and plumb copper tube back into the fabricated collection tank.
I already have the non-return valve on order, so I will still fit it in the line to the tank.

[1967Brutus]

Thank you, Brutus. That is super useful. I also saw your previous post, which answered a lot of my questions.
My idea is to fabricate a removable glass fibre tank that will fit in the forward part of the boat under the deck to collect the overflow from the condenser tank. I'll create a "take off" point near the top of the tank using a union fitting and plumb copper tube back into the fabricated collection tank.
I already have the non-return valve on order, so I will still fit it in the line to the tank.

https://www.youtube.com/watch?v=WJJe1eHWLmw

If you pause this vid at 00:15, you can see how I solved it. Better yet, scroll to 10:25~10:30, better visibility.
I replaced the "emptying cap" of the condenser/oilseparator with a teflon plug, pierced by a piece of 2 mm OD, 1 mm ID copper tubing, that runs all the way to the bottom of the condenser/oilseparator. This way, you leave the oil separator body undamaged.

There is quite a bit of velocity in that condenser, and having any significant level in there only reduces its inner working and necessitates the emptying after the run (if you don't, then the next cold start, producing between 10 and 20 ml of condensate in mere seconds, will overflow the condenser)

The thread used for that plug is M8 x 1,25 if I am not mistaken. Not a common bolt thread, but pretty good availlable as dies and taps nonetheless.
You can without a problem extend the draintube with some 2 mm ID silicon tubing to get the discharge to a tank at some distance.

There are no issues fitting a non-return valve in the feedline, but with a single feedline and no bypassvalve, it also serves no function.

If your TX allows, use a speedcontroller for the feedpump, and control it via a slave channel and a programmable curve to the steam throttle.
Assuming constant boiler pressure, the feed quantity is proportional to the throttle position. This will save you the trouble of setting up a boiler level detection system and either manually or automatically starting/stopping the pump.
A continuous feed is also better for the boiler (thermal stresses are more constant) and steam production ( no "shots" of cold water intermittently entering).
Setting up the curve is relatively easy: all it takes is 4 separate 10~15 minute runs at steady throttle position (1/4th, 1/2, 3/4th and full), and this works well enough for me to never have seen the need for a better system in 120 runhours.

I mean, if you want to adhere to the KISS principle, direct feedpump speedcontrol is AS simple as it gets... No additional servo, no additional bypass valve, no alarms or detection, all you need is the possibility for a visible confirmation of the pump functioning.