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Post by Cro on Apr 28, 2015 12:33:52 GMT
There are from the usual suppliers but I didn't like the quality of them and like I previously mentioned the large rams on them were always too much so I made up a few batches of them for people
The only tricky bit really is making the ratchet wheel hence when I made quite a few at a time whilst I had it all set up. The rest is fairly simple.
Adam
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Post by gwr14xx on Apr 28, 2015 14:08:20 GMT
Hayden, Can I suggest that you incorporate some sort of restriction in each branch if you are going to use a single lubricator to feed 2 cylinders? Fluids always take the line of least resistance, so may still favour 1 cylinder if there is nothing to persuade it to do otherwise. The restrictors should only create a slight increase in the pressure generated. The main priority with any system using a 'thick' oil is that the feed port to the pump should be large enough not to create a vacuum on the return stroke of the pump as this can cause the pump to airlock if the ram is not a good fit, and subsequently the pump will stop working. The pressure circuit between the pump and the check valve should be completely air-free. If this is set up correctly, the rest of the circuit will sort itself out.
Eddie.
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Post by Roger on Apr 28, 2015 14:08:30 GMT
There's also a much simpler one by Jim Ewins. That one can have a spacer changed to alter the volume delivered too. It was featured in the Model Engineer August 2010 The ram has a slotted end and is moved by a crank pin. The ram slides in a bush and holes are uncovered as the ram goes up. There are two 'O' rings with spacers above the top one and between them so adjust how much of the stroke is effective. There's a separate non return valve but that's all there is to it.
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jma1009
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Post by jma1009 on Apr 28, 2015 21:32:08 GMT
i think you are all approaching this from the wrong angle.
firstly, roller clutches shouldnt slip if covered in oil. if they do then something else is amiss ie shaft not properly hardened and of incorrect size.
if water is in the tank then the check valve is leaking. i test all mine (although i use displacement lubricators with sight feed on my own locos, ive made quite a few mechanical lubricators over the years).
LBSC described a very simple method for testing mechanical lubricators. i rig up a more specific test using compressed air on my compressor to ensure the check valves dont leak on air at below working pressure of the locos. the steam chest pressure will always be below this in miniature. if the check valves leak on air it is a pretty good bet they will also leak with oil. i havent had a leaky check valve yet!
the oscillating pump ala LBSC has considerable advantages over the Jim Ewins type IMHO. the non-oscillating type isnt actually a Jim Ewins design as Martin Evans used it on his 'Jubilee' in 1958/9.
the fit of the roller clutches is very important and most are metric, as is the need to harden the shaft.
i dont agree with adam that a ratchet mechanism is better than a properly fitted roller clutch. but as usual in miniature the problems occur in the details and how these things are made and to what tolerances. the problem usually arises in vagaries of commercial 'parts' which might not be quite up to standard.
none of this negates the importance of having a properly set and made check valve that seals perfectly yet doesnt impose too much strain on the pump.
cheers, julian
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Post by steamcoal on Apr 28, 2015 21:45:49 GMT
Julian.
I see no issues with clutch/ one way bearings either as I have them in my machinery for 35 years and never touched them.
Does one need to build some sort of test rig to check the check valves. Would it need to be hydraulic or oil filled as do they have different properties under pressure?
Obviously the check valve opens and closes as the cylinder pressure varies during the power and exhaust strokes. Can too little pressure on the spring allow the ball to seal more slowly.
I might revert to the system installed on the Hunslet at present and monitor its operation. Is it dangerous to have a shut off valve in the feed line between the lubricator and the cylinder no matter what type of lubricator is use?
Hayden
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jma1009
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Post by jma1009 on Apr 28, 2015 22:28:54 GMT
hi hayden,
all you have to do is take off the check valves and clean all the parts in celloluse thinner then reassemble on the air line and test on air up to 80-100 psi independantly. if the check valves dont pass this test they need altering. if they dont leak at 120 psi the spring is too strong. if they leak at 80-100psi then the check valve seats are dodgy. it's as simple as that!
cheers, julian
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Post by Cro on Apr 28, 2015 22:36:58 GMT
Out of interest Julian why don't you feel ratchets are better than clutches?? I know we all have our own preferences just thought I would ask, I feel that clutches have to many variables that cause them to go wrong as have been stated above here with oil, non hardened rods or even rods too small plus older ones can wear out and it not always be easy to tell if they have. I know ratchet pulls and wheels can where out but these are simple enough to regrind and re harden if need be.
Adam
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Post by steamcoal on Apr 28, 2015 23:02:49 GMT
Julian. Thank you.
Should make some of my own.
Is brass or bronze best? Bronze me thinks?
Hayden
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jma1009
Elder Statesman
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Post by jma1009 on Apr 28, 2015 23:05:17 GMT
hi adam,
i did some extensive tests with roller clutches in the mid 1990s. what impressed me was the very small movements required to move them. with ratchet wheels to get them to move one tooth per stroke can be a bit problematic - generally there is a problem unless the teeth are extremely well made and the movement imparted to the ratchet lever corresponds. to get round this problem if you make them 2 teeth per stroke usually too much oil, and if 3 teeth per stroke far too much oil always! my own method to get round this problem has been to use a 1/16" dia ram on mechanical lubricators.
i have never understood the reasoning behind connecting a mechanical lubricator to the valve gear - the loco needs as much oil when notched up as when in full gear!
a loco i fitted with roller clutches in 1996 is still running perfectly with the mechanical lubricator untouched since made, and an LBSC style oscillating pump made circa 1963 is still doing sterling service on another loco albeit with new pawls fitted the same year. none have ever had 'blowbacks' through the check valves because the check valves were all tested on air and springs adjusted before fitting to the mechanical lubricators.
in my opinion the LBSC type lubricator never wears out or causes problems if properly made, adjusted, and fitted. the only reason they might cause problems is due to poor workmanship or fitting. the ports need very careful drilling.
i dont fit them to my own locos because i like to see the oil blobbing through a sight glass and all the locos ive built had sight feed hydrostatic/displacement lubricators fitted in fullsize anyway!
cheers, julian
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Post by Cro on Apr 29, 2015 9:16:22 GMT
Julian, I only have one loco with clutches and I do agree with even the slightest movement will drive the pump which is extremely useful as like you say when notching back it won't stop the pump from driving as it can do with a ratchet.
What I would say about getting good adjustment and set up on a ratchet is try get it on 1- click, if with a small ram this is still delivering too much then making a 72 toothed wheel wouldn't be a problem with well made, sharp pulls.
They are fun little things to play around with, although messy! When home I plan to make up another batch of wheels and try some 72 toothed ones.
Adam
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jj
Active Member
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Post by jj on Apr 29, 2015 11:59:35 GMT
I've now received the new pump ram O-rings from Steamfittings. The old ones had definitely worn - they did not drag on the pump ram at all, whereas the new ones do. This is after five years of regular steaming, so I guess I can't complain. Hopefully this will cure the problem.
Incidentally Julian I did fit hardened silver steel pump spindles of exactly 4mm diameter - the original mild steel ones were hopeless and soon had score marks - but I still get a little bit of backlash when oil gets into the fixed clutch, which prevents me setting the drive cranks to give a very short stroke. There's absolutely no backlash when the clutch is clean.
Regards, John
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Post by andyhigham on Apr 29, 2015 19:02:33 GMT
The problem with steam oil on roller clutches isn't the fact that it is oil and lubricating the rollers/shaft. The problem is thick sticky steam oil slows the rollers returning to position within the cage. Ideally the clutches should be outside the tank, lubricated with thin oil like WD40 (other spray fish oil based lubricants are available) and maybe even sealed to keep steam oil and other sh*t out
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jj
Active Member
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Post by jj on Apr 30, 2015 10:29:08 GMT
Hi Andy That makes sense. This photo on the Steamfittings website shows the clutch mechanism: link and you can see how thick steam oil would slow the action of the little plastic springs. Regards, John
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Post by steamcoal on Apr 30, 2015 12:47:23 GMT
I have my Hunslet lubricator operational again, the non clutch rocking type.
I re-seated the lubricator balls with a gentle tap and they pump fine now.
For the check valves I made a spigot to go between the spring and the ball to cup the ball centrally. This was missing on the inline check valve but the check valve on the lubricator had one. Each check valve now only has one ball.
I primed the line and tested the check valves, both work. Just to confirm my suspicion about the hydraulic blocking I closed the tap and gently oscillated the pump and with two or three pumps the resistance increased markedly. This was just with very slow movements of the actuator arm so I think that under normal running conditions the lubricator is easily damaged and the shutoff taps are potentially a dangerous items inline. I do not see they have any effective use but they can stay for the moment but remain always open.
I will now work on my Railmotor lubricator which is intermittent at full runnning speed but works at slow ahead. That I know is the hardend shaft issue so a new clutch bearing and shaft. Simple fix that one I hope.
Maisie has a LBSC one and she is fine! Julian.
Hayden
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Post by Roger on Apr 30, 2015 14:17:08 GMT
I can't see any logical reason to block the output from a fixed displacement pump, that's just going to break something. Perhaps there was a relief valve between the pump and the valve, so that when there was a restriction the surplus returned the output from the pump to the tank? That would make sense to me because as you've discovered, the pump is capable of delivering far too much oil.
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Post by steamcoal on Apr 30, 2015 19:25:39 GMT
Roger,
,There is no relief valve, just a shut off tap. crazy really.
I will experiment with the offset ram oscillator this weekend.
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Post by Roger on Apr 30, 2015 20:52:02 GMT
Roger, ,There is no relief valve, just a shut off tap. crazy really. I will experiment with the offset ram oscillator this weekend. Curiouser and curiouser...
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jma1009
Elder Statesman
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Post by jma1009 on Apr 30, 2015 21:49:33 GMT
i am similarly perplexed by Hayden's extra valves, the purpose of which i cannot fathom!
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Post by Cro on Apr 30, 2015 22:23:45 GMT
Only thing I can think of is that if if was oiling too much you could close the valve slightly (not fully) to restrict the flow till you get your desired amount?
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Post by steamcoal on Apr 30, 2015 22:56:07 GMT
Adam. I tried restricting the flow while manually pumping the lubricator but because the pressure of the oil is high the flow is either open or closed. I think that when one is trying to restrict the flow at that end of the cut off regime the aperture opening is absolutely small.
I would rather have more oil than none at present and wiping away residue is a small price to pay, certainly a better outcome than replacing piston rings or re honing a scored cylinder. I might look into a relief valve setup if it could work.
Does anyone know a lubricator pump output pressure generally?
Interesting subject in itself this lubrication.
Hayden.
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