Print

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

[fredgraham]

Hi Folks,

Has anyone any idea how to determine/calculate how much oil should be pumped into a steam engine per minute/hour depending on bore, stroke and number of cylinders. I have scoured the internet for such data and although there is a lot on internal combustion there is nothing on steam engines.
It seems that most users provide a displacement lubricator and keep filling it up when it is empty. If it is pumped, which I suspect would be a bit more reliable, from the engine shaft (albeit geared down quite a bit) the pump size must have some relationship to the engine size.

Any ideas would be most useful, thank you, Fred Graham

[derekwarner]

Welcome Fred......in terms of reliability, could I suggest some reading in the following area of Mr Bernoulli ........it discusses the basic principal and leads to all designs of displacement lubricators

As you will see, it is technically and mathematically far more reliable and accurate than any variable mechanical means ........ Derek

https://www.google.com.au/url?sa=t&rct=j&q=&esrc=s&source=web&cd=6&cad=rja&uact=8&ved=0CDkQFjAFahUKEwjysKKD4K7IAhWCtpQKHVmCABM&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FBernoulli's_principle&usg=AFQjCNG6bbMu9tM0wTrxpH4y9gNzN154pA&bvm=bv.104615367,d.dGo

[BarryM]

Fred,
What size of engine are you talking about?
Barry M

[Brian60]

Or have a word with DerekWarner_decoy (forum member) He's into steam in a big way, both steam trains and boats.

[derekwarner]

Fred/Barry................true I am very interested in model steam, however am more of a very humble student of the likes of Sandy Campbell or and George Thompson...........for model marine steam...

I am fortunate to have access to many OZ model steam train engineers....however lubrication for steam trains & steam boats are very.....very different  aspects to consider

Both Sandy & George [Scottish gents] are members here on MBM & may pick up on this question.......... Derek

[BarryM]

It brings to mind the tale of the 4th Engineer on the 8-12 concerned about the temperature of a main engine bearing and its lubrication. Eventually he rang the C/E and asked his advice.

"Listen", said the Chief, "Spit on it - and if its spits back - it's too hot. Good night to you."

At the scale of marine steam engines we usually operate, precise lubrication is not of great concern. I assume you like to delve into the theory of things and tease out the details?
BM

[mrsgoggins]

I suspect our displacement lubricators know nothing about Mr Bernoulli since fluid dynamics play no part in their operation. Oil is displaced by the condensation of steam into wate, simples.

[mrsgoggins]

Or even into water. Woops

[sparkey]

  Judging by the amount of oil I get in my oil separator it works pretty well,never had a problem with this system simple and safe....Ray.

[Jerry C]

We use displacement lubricators because they work. The amount of oil required is very small. A litre of 600 steam oil will last a lifetime. My TVR1A does 3x 35 minute runs and the lubricator is not less than 1/2 full after an afternoon steaming. Less than 1 cc used. I can't think of a pump that will deliver such small amounts.
Jerry.

[xrad]

You only need a 'tiny' amount of STEAM oil for these little engines.  Ratchet pumps can be made to work, but are not necessary.


 I use ratchet/pawl pumps on my 3/4 scale steam train engines. you could hook one up to a crank cam. these come in various reservoir box sizes 3/4 inch square and bigger.  They generally work well, the only issue being ratchet wear.


good image here: 
http://www.maidstone-engineering.com/lubricator-ratchet-wheel-7-16-dia


these will , depending on the radius of the ratchet arm hole,and inner pump diameter, pump out as little as(or less than) 10th ml per 'whole' revolution.  basically, you might rotate 3-4 teeth per engine crank revolution, which is that many degrees of 'inner oil piston pump' travel.  But this is still a lot of oil for our 3/4 x 3/4 (or so) twins.  Even my Stuart triple worked fine with just a displacement lubricator.


As far as setting the displacement lubricator, that will depend on bevel of needle. If unknown, and it usually is, I tighten it snugly (not firmly), then back off 90 degrees(sometimes a bit more or less). usually helps to put a mark on the finger wheel, 12 o'clock position when closed. This will provide enough oil for two runs of about 20-30 minutes with average 3/4 bore engine (twin) using about 30-40lbs steam pressure of a mildy dry steam and average lubricator volume of about 7-8mls. Not superheated at 100 psi.......don;t forget to drain the water out and refill lubricator after each run. Then you can gauge useful volume. 

[southsteyne2]

As Derek has mentioned there is a big difference between miniature trains and model boat engines mostly model trains have cast iron rings which require a different formula to model boat engines as they mostly have o,rings which really were not intended for this purpose but that's another story, so it is mostly emulsified in the cylinder with no rigid rule as to the amount certainly not rocket science
Cheers
John

[fredgraham]

Thanks folks for all the comments and it looks like displacement lubricators do the job. The capacity of my marine engines has never exceeded 3/4" x 3/4" twin double acting and I use the LBSC ratchet lubricator for this size of plant. Thus far seems more than adequate.

Happy steaming All the best, Fred Graham