Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length.

[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