7, 1/4 Denorwic Hunslet to Milna design

[clifford]

Hi all,

I have recently started running my Hunslet after setting up the valve gear etc.  However, Im experiancing one or 2 anoying issues that I would welcome members thoughts on, viz.:

Whether running on air or steam it is almost always a pain to move off in forward gear.  Having had it jacked up in the workshop, running under air, it inveriably stops on the same TDC 3/4 of the time.  I then have to go into reverse to move it off, or rotate the wheels just off TDC.

Ive tinkered with what I believe is the eccentric causing the issue i.e. admiting steam just before TDC.  So I slightly retarded the valve, to no avail.  Running at my club on Sunday, it then sounded slightly less of a 'balanced' chuff, if that makes sense?

Unfortunatly, the adjustment of the eccentrics cant be carried out without taking the sheaves off!  My plan is to mill a narrow and short slot in the back of each sheave to gain access to the grubscrews for minor adjustments!

Secondly: When first moving out of the steaming bays, it seems to be a bit of a devil with moving off.  Im putting this done to cold cylinders, and have the drain cocks open, but to no avail.  After a few attempts, it improves.  Then its ok.

Im guessing this is steam condensing when the regulator is first opened.  But this week it seems a bit worse than before.  

My plan, next time, is to have the regulator opened a little in mid gear to get stea into the cylinders to warm them up.  However, this issue seems quite pronounced, and I dont see others having such and issue...

Any thoughts would be greatly appreciated.

[Nigel Bennett]

Is it something daft like the coupling rods binding at that position? Or perhaps the piston just clobbering one end of the cylinder?

[borderer]

As said, always stopping in the same position does suggest that something might be binding, so that possibility should be eliminated first.

If it isn't a rude question, what procedure did you use to set the valves? The Milner design I think uses launch links which makes it relatively simple and if you position the eccentrics correctly, it is difficult to see how just one of them would be wrong.

[Bluff Chuffer]

I have experienced with a friends HUNSLET ( 5" Don Young design) over flooding of cylinder oil in the steam chests. The loco was fitted with hydrostatic lubricator and it could over oil the cylinders as it had separate steam supply, not from the regulator actuation.
With the balanced steam valves, there was very little means to displace oil trapped in the chest. This particular loco had drain cocks fitted to the chests at the rear position, (originally it looked like actuated with the cylinder drain cocks, but were disconnected). The loco would not roll easily once over oiled, resistance felt at 4 points of the wheel rotation, but these were not at piston TDC & BDC, but at valve TDC BDC.

This could happen with condensate build up.
I have also experienced the same with a ROB ROY when air test and over oiling of cylinders with oil can.
The wear on the eccentric straps was extremely excessive - they had been working hard to overcome the hydraulic resistance.

[jma1009]

Hi Clifford,

Some 18 months on from your “Valve timing, Hunslet” thread you appear to be no further on.

I had quite a bit of experience with the 7.25” Milner Hunslet design and my views on the Milner design are quite well known.

It has launch links with no suspension offset, so the valve gear is far from optimal, but it will work if made correctly, and set. Just don’t expect it to be able to be ‘notched up’.

It ought to be able to run very well in full gear if properly made and set.

You clearly haven’t got something right.

You need to have say 10 thou negative lead in full gear valve setting with this arrangement of launch links, and equalise the leads rather than set the valves “centrally” which means not a lot. Check the cut off in your full gear setting. Establish what percentage cut off it is. Tell us what it is! Tell us what the lead figures are for each cylinder front and back for Front Dead Centre and Back Dead Centre for this cut off.

Do your valves match the ports? To what degree of precision have they been made - both valves and those horrible round Milner steam chests (with their non-existant valve glands)?

The Milner launch link arrangement requires something like a 1/4” suspension offset to enable it to be ‘notched
up’.

Are you familiar with the strictures and process of setting valve gear?

Cheers,
Julian

[borderer]

Clifford, You have a PM.

[terrier060]

Sorry Julian, this time you are talking rubbish. My Hunslet will actually run in midgear, once it is moving, and will certainly run well fully notched up. And I think I am righht in saying that Nick's will as well!

[terrier060]

Clifford, have you checked the quartering, because that would certainly cause binding in one spot? The Milner hunslets run and steam well, but you do need to push them back and forth a few times with the cylinder drains open and the regulator cracked just to let the condensate escape before running. They will lockup if not as the water in the cylinder is non compressible. Would be nice to see a picture of your engine.
Ed

[jma1009]

I went back to Clifford’s previous thread before posting on this new thread.

I don’t think that what Clifford describes on this thread is an issue with quartering or over lubrication or condensate in cold cylinders. If these issues were present, he does not appear to have any issues with the loco running backwards.

Whether Clifford has given us a proper description is perhaps something that is another matter.

From his previous thread, he described “centralising” the valves. Not much else, and nothing like the checks of lead and cut off that I would exhaustively undertake.

If the loco runs ok in reverse but is awkward at one particular point in full gear in forward gear then if my understanding is correct (and it would appear that the valve setting is not as thorough as I would undertake from his previous thread) then it may simply be that the forward eccentrics are not set correctly, or that the centrality of the valves is masking the obvious additional checks required. When is a valve central?

I’m not going to respond to my old friend Ed Cloutman’s comments of “rubbish” except to say that if the late Don Ashton thought I was talking “rubbish” we would never have had the regular exchanges via email and telephone.

Yes, you can just about run in mid gear with a GWR type Stephenson valve gear with launch type links and everything being perfectly designed (with the correct suspension offset for the expansion link trunnions) with slide valves and direct drive, and everything being perfectly made and set. You would probably need the valve gear to be set for perfect events at say 50% cut off, and you would certainly get better results with slide valves and launch type links with indirect drive. You would probably do this on a downward gradient with a load behind if in mid gear.

But that goes against accepted full-size practice when ‘coasting’; the LMS particularly I think from memory advocating a 55% cut off when coasting.

Currently, we have Clifford’s loco that doesn’t even want to run ok in full gear!