Lubricator drive problems

Has anyone had any problems with lubricator drives using small roller clutches? There is so much rotational lost motion that the pump is failing to work. I have shortened the drive lever (on the lubricator ) to get more movement but there is still insufficient travel to get a uni directional movement of the pump shaft. The shaft the clutches are working on is not hardened and I wonder if this is the cause of the lost motion, the shaft is dead to size.

There are plenty of articles including drawings of this type of drive, it was covered by Neville Evans in his Penrhos Grange series, so someone must have got them to work.

Before I throw the clutches out and make a ratchet drive I would appreciate comments.

Hi Andrew,

Some of ideas to look at/think about:

1. ideally the shaft should be hard, but just as important the shaft must have an excellent finish, preferably ground. It will likely work unhardened (at least for a while) if it has a good smooth surface. Ground, hard stainless shafting is ideal.

2. is the shaft dry? if there is too much oil on the shaft the clutch's rollers may skid rather than drive.

3. is the pump outlet open? will it pump oil if you rotate the shaft by hand? (if the pump outlet is clogged, the pump will be hydraulically locked and type of drive clutch or ratchet drive will not matter - it will not pump).

4. roughly how many degrees is the pump lever swinging through? ideally it should be at least a 20 deg swing, 30-45 deg would be even better, for clutches or ratchets.

Hope these things help.

JD

Edited By Jeff Dayman on 13/04/2012 17:27:30

Hi Jeff,

Thanks for you reply.

1. Finish is not ground although I am about to make another pair of cranks and I shall leave them o/size before hardening and lap them to a thou oversize.

I have found an article on page 37 Jan 1987 of vol 158 of ME entitled "Clutches and Lubricators - A Warning". The author had the same problems and hardened out oversize shafts which cured the problem.

2. Shaft is not dry, the inner clutch is in the tank! Can only cure this by a complete redesign!

3. Pump outlets are open, hydraulic locking is not a problem.

4. Swing is less than optimal, increasing the length of the drive levers is a problem because although I am not building to Duke of Edinburgh standards I need to stay fairly close to a prototypical layout. The loco is a BR Standard Class 5 in 71/4" and the drive comes off the expansion link pivot so there is not much swing to start with. I have measured about 15° of movement at the lubricator. It looks as though I am going to have to shorten the driven/lengthen the drive levers to get some results.

Any further thoughts would be useful, but I think I have to make some new shafts.

Regards,

Andrew

Hi Andrew,

Not sure what brand of clutch you are using, but Koyo are one brand and have some handy engineering literature at the link below.

http://www.koyousa.com/brochures/pdfs/cat113ex.pdf

They do mention some h8 to h10 shaft tolerances for their clutches, which are pretty small tols. If you let me know the nominal shaft size you have I can tell you exactly what the h8- h10 limits would be for it. However, this may not be exactly applicable to your clutches unless they are Koyo.

In industry I have specified many of these clutches and they do work well if the shaft surface condition and size are exactly as per manufacturer's recommendation. Unfortunately in the live steam world the clutches are often sold like wood screws ie " here's one for 1/4 shaft and here's one for 5/16 shaft" with no shaft spec tolerance and finish data along with them, so people sometimes get in trouble. To make them work well you need to know the clutch manufacturer's recommended shaft sizes and finish. If you buy them from a proper industrial bearing or drives shop at least you will know the model and make and can look up the engineering literature online.

Does you clutch have any markings? you may need a magnifying glass to find them, but usually the clutches have a maker's mark on the side rim, and a part number. If you Google these, you may be able to find shaft spec data for your specific clutch online, and work to that.

JD

They came from my local bearings/belts/transmission supplies dealer. I am not sure of the make but I will break one out in the morning and check. I seem to remember looking at a spec online but it was a few months back and I didn't keep a record.

h8 tolerances are away beyond my capabilities! -0 -18 micrometres!

I'm doing well to get to the nearest thou!

Thanks for the information.

Regards,

Andrew

Andrew,

I had problems with a commercial lubricator I bought a couple of years ago. It used a hardened steel shaft with roller clutches, and was unreliable. I fitted new clutches but it still failed. The shaft was only supported on one end were it passed into the tank. It was tilting when the pump plunger was forced down by the cam. I made a new shaft from silver steel which I hardened right out. I also drilled a hole in the other side of the tank, in line with the original bearing. The new shaft went right through both holes and was supported at both ends. The tank material was thick enough to use as a bearing so it was an easy job. It's worked fine ever since, and the feed is easy to vary if needed. I emailed the manufacturer to explain the problem but had no reply.

Hope this helps

Regards, John.

Thanks for your post, John W. Not sure why it doesn't appear in the thread.

Perhaps David Clark can move it to this thread?

John W had experienced similar problems with unreliable roller clutches on a commercialy produced lubricator, but beefing up the assembly and supporting a fully hardened drive shaft at both ends cured the problems.

Thanks for that John, it further confirms the direction I need to go in. Do you know what sort of angle the drive lever is making? A previous post suggests that at least 20° swing is needed for reliable operation. If I could get that sort of movement then my existing set up might work anyway.

Regards,

Andrew

what is happening to your lubricator is normal after they have been working for a while , it is the rollers inside the clutch that are gummed up with thick steam oil so it is not working as it should . to solve this problem all you need to do is wash the clutch's out with parafin or similar cleaners

robert

To Robert Barker, thanks for your post. This is a new build, it hasn't run yet so gummed up rollers are not the problem! The problem lies either with the design or my workmanship. Probably a bit of both!

Andrew,

The angle on mine is 16.5 degrees. it is the large Steam Fittings lubricator, and this is the minimum it will work at reliably. there is no problem with the clutch running in oil so far, maybe the type of oil affects this. I think any misalignment of the clutches is the main cause of problems.

Regards, John.

Hi Andrew,

One other thing about the pump design drawn in several of Neville Evans' loco series. The plunger/follower design did not make sense to me as it was drawn. It may have been carried over from the Ewins design, I'm not sure. Anyway my sketch below shows a possible alternate way to make it that may be stronger and be easier for assembly and disassembly. I also agree 100% that better support of the drive shaft at both ends would be a good idea. One caution re the suggestion to clean these clutches with paraffin etc - fine if the internal roller springs are metal but many small roller clutches now have polymer springs - these should not be cleaned with any mineral solvent.

Thanks to David Clark for getting all the posts for this thread in the right place!

Thanks to everybody for the contributions. I have got the lubricator working after a fashion by increasing the driven angle on the lubricator. In the light of all the comments I may do a rethink on the design once the Loco is running and I can see what's happening in steady state running conditions.

If it ain't broke . . . . . .

Thanks,

Andrew

Hi Andrew

Was not me, probably Diane.

regards David