LBSC Style Ratchet Wheel Mechanical Lubricator

This design employs an oscilating piston assy - surely the spring tension holding the piston to the port face must exceed that of the incoming steam pressure or the piston/cylinder would simply be forced off the port face? I need to ask as my attempt at a static piston pump lubricatot failed (it doesnt pomp!).

Edited By DMB on 21/07/2015 14:49:04

Edited By DMB on 21/07/2015 15:03:08

Thanks all - but everyone has missed my point. If its the oscilating type the pressure of the ram must surely be greater of that of the inlet steam pressure, and by virtue the iol would escape from the assy by overcoming the resistance of the spring which keeps the two parts together? So how strong does the spring need to be?

Fizzy,

Don't forget that the pressure the pump actually needs to produce is proportional to the area of the ram. A 1/8" diameter ram has a cross sectional area of only 0.0123 sq. inches so to produce 100psi the pressure on the ram only has to be 1.23psi so the pressure trying to lift the cylinder off the port face is very low. Think that's right anyway!

Most good lubricators will easily produce several hundred psi. The biggest problem is getting the ram to be a good enough fit in the cylinder bore. I like the Jim Ewins type where the ram goes through two O rings which seal perfectly.

The LBSC oscillating type usually have a packed gland on the cylinder to seal the ram.

Whilst the ram may seem to seal perfectly when the oil is cold, as soon as it gets hot they may leak like a sieve!

John

Edited By John Baguley on 21/07/2015 18:26:30

Edited By John Baguley on 21/07/2015 18:27:57

The secret is the small cross sectional area of the hole.

DMB - A lot of commercial lubricators sold by our regular suppliers used to be made by one man ~(who owned that tiny stand at Ally Pally selling odd szes of silver steel cheap) but I understand he gave that up last year.

As I'm thinking about building a small oil pump can someone point me to a description / plans for this Evins lubriccator? I remember vaguely having seen it long ago, but have no idea where it was.

regards, HansR.

Edited By DMB on 21/07/2015 22:00:15

Like others, I am trying to get my LBSC 5" size pump to work. By experiment, the length of ram or distance of the hole in the ram to the end of the ram is critical. The drawing calls for a ram O/a length of 7/8" but doesn't give a dimension of the "pin hole" from the opposite end. If the ram is too long (but doesn't foul the end of the cylinder), then oll is not drawn into the cylinder/ pushed out. By using a slightly shorter ram, I am getting limited success - trials continue.
Incidentally, its the gland seal which is most important and not so much the fit of the ram in the cylinder I think.
BobH

Just a reminder , of those mini- O rings to be found in disposable lighters.

this is a bit of an old thread which Bob has resurrected!

there is often/always an error in LBSC's drawings for same. if you draw everything out 2 times fullsize or more, or apply a bit of maths it is clear that the ports dont coincide when the pump is at an angle when the crankpins are at 3 and 9 o'clock. the discrepancy is only just 1/64th out but is worth checking and dealing with. it makes a huge difference to how they work! the ports must coincide, and very careful drilling is required for the oscillating LBSC type!

the gland seal on the ram has never been a problem - after all the whole thing gets covered in steam oil. i had a loco with a commercially made LBSC mechanical lubricator made in 1963 and with a new owner is still ok and pumps 100% reliably as the day it was fitted. that is over 50 years regular use.

i only made one myself for my first loco 32 years ago, but have repaired quite a few over the years. i have fitted hydrostatic sight feed displacement lubricators to all but my first loco.

cheers,

julian

HansR

Details of Jim Ewin's lubricator can be found here:

Engineering in Miniature Jul '82 pg 48

ME 1999 Vol. 181 #4077 pg 401 & 4081 pg 636

2002 Vol. 188 #4164 pg 79

2005 Vol. 195 #4252 pg 87

2007 Vol. 199 #4314 pg 685

2008 Vol. 200 #4216 pg 29

John Purdy

Thanks for the replies - however I don't have access to the archives for J Ewin's lubricator, but from other pictures on the net it looks like an interesting alternative to LBSC's.
BobH

edit, info already posted

Edited By Ady1 on 12/11/2015 09:35:04