7.25 inch gauge Milner Hunslet

[terrier060]

I have decided a new thread is in order, though I previously avoided it.



These Hunslet springs are giving me a headache. We have two Milner Hunslets in the club, Nick's is stable on the track while mine bucks all over the place and has derailed several times. The chassis are very similar to Milner's drawings, but mine may be a little heavier as it is the cab version.



I have tried to fathom why his rides smoothly and mine does not. I have tried stiffer springs but this seems to have made matters worse. Today we had a eureka moment when our member Wane suggested that it was probably because my springs were acting on top of the axleboxes, whereas the Milner ones are on the spring hangers which give nearly 6 inches more stability as you will see below.  You can see the springs in the lower picture.



Hunslets were little quarry locos built to run on uneven track with sharp bends, hence the 0-4-0 wheel arrangement. They were certainly not built for speed. There is a lot of overhang, the cylinders and smokebox at the front end and a very heavy firebox at the rear, particularly on the model where Milner has made the firebox larger to give good performance. Mine is a copper boiler made by John Ellis and is a great boiler and steams well, but does have a heavy firebox.



We think that my problem is having the springs directly over the axleboxes, basically on the wheel centres. This is fine on an 0-6-0 or locos with more driving axles as they are more inherently stable. The Milner design has the springs on the ends of the spring hangers which in effect gives nearly six inches extra outside the axle centres and therefore must help with stability. You can see this in the pictures below.



So how do I remedy this? There are two options as far as I can see unless I use some form of shock absorber. I can either go back to the Milner design, which in my preferred option. It is a good design and very easy to try different springs and very accessible to adjust them. Basically good design unlike the present one which is very awkward to adjust and means the removal of the injectors etc.  But this preferred option would mean removal of the boiler and would be a big job.



The alternative would be making working leaf springs which I have been told have natural damping properties. I could do this with a minimum of disruption to the loco, and without removing the boiler and all its associated pipework. I particularly do not want to disturb the pipework in the smokebox, though it would allow me to fit a snifting valve.



So has anyone, to your knowledge got a Milner Hunslet with working leaf springs, because I would very much like help with the design, as I know nothing about how to make them adjustable or what size and how many leaves to make?


Leaf springs by ed cloutman, on Flickr

[Roger]

Hi Ed,
I can't see that where the springs bear on the axle boxes can have the slightest influence on the springing, all other things being equal. Mounting them so they are compressed to a different amount, different spring rates, or using leaf springs is a different matter.

It would be very interesting to measure the load being carried by each wheel, because it may be that there are big differences that aren't obvious.

I'd certainly look at damping, I think that's a sensible thing to add whatever else you do, because it will allow the use of softer springing which will give the most adhesion.

[terrier060]

Forgive the crude sketch Roger, but I may be misunderstanding the physics, but would not the spring arrangement on the above sketch be more stable that the lower one, as the springs are spaced further apart and the outermost springs are nearer the ends of the loco frames therefore bearing on the frames 6 inches wider than the wheel centres?  The double line at the top represents angle iron bolted to the frames.

Spring centres by ed cloutman, on Flickr

[jma1009]

Hi Ed,

Your top sketch makes more sense and is what I vaguely recall of a Milner Hunslet I drove on and off for 6 months 10 years ago named "Pamela" but which those of us nicknamed "Gertrude".

Proper leaf springs are the best option, but I don't recall experiencing the difficulties you have had with 'bouncing' with "Pamela/Gertrude". We did however have a brand new and newly laid ground level track at Merthyr that was constructed to a very high standard and inspected at the start of every day and regularly tamped and adjusted at least twice a week. It had to be for what became a daily commercial operation.

Are the springs either side working on the cast fake leaf springs free? The slightest inaccuracy in the bits or holes through same could impart friction? However, 'bouncing' is usually the opposite so it is a conundrum potentially.

I do recall running one of my locos at a track in N Lincs that shall remain nameless around 2020. It was my 5"g Railmotor and had springs within springs ala Greenly departing from the original drawings, as it was otherwise quite bouncy, but it was ok on the rebuilt IWMES raised track, and it was quite ok on the ground level Ascot track. It was quite ok on the Cardiff raised track. But in N Lincs I took it off after 2 laps as the track in question was so bad. In 5"g I basically had my hand on top of the dome those 2 laps and my other hand on the rear buffer beam.

Although not visited myself, I am sure your Bridgend club track is very good, but some tracks suit some locos better than others.

If you posted some pics of the springing arrangement as is, I am sure you will get some further comments and advice. With 2 springs underhung either side for each axlebox for the Milner type, I don't recall any issues, and there is ample room in that configuration to provide long springs of the correct size and rating.

If you have instead one central spring crammed between the cast fake leaf spring and top of the axlebox, then that is going to be a seriously compromised arrangement not capable of tweaking to achieve the performance required.

[steamer5]

Hi Ed,
Not knowing the Milner Hunslet, I went googling…

Here’s a link to a video….music is rubbish but it shows the spring set up very nicely!

youtu.be/qx3KaR1ct9A

This gent has built his as per your first sketch, which I understand from your comments is how it was designed.

Cheers Kerrin

[terrier060]

Thank you both for your comments. I am lucky in that I have a direct comparison on our track between mine and Nicks. Nicks is to the Milner drawings which is exactly as the video shows, thanks Kerrin.

Julian, if you look at my pictue above you can see my springs, two to each axlebox between the box and the top of the horns. My point was,is this a less stable configuration than the Milner one? I think it must be as it is the only difference between the two locos which have chassis to Milner's drawings. The fact that the springs are further apart and spread over a greater length of the chassis makes the loco more stable?? I cannot see any other way of explaining it. If anything Nick's springs appear to be softer but the loco is quite stable.

I would really like to hear from someone who has built the Milner Hunslet with working leaf springs, otherwise I will just have to remove the boiler and revert to the published design. It is sad that the chap who built the chassis had not done so. I was told by Royston that this was his preferred method, but I gather this was on locos with more than two driving axles which is a different kettle of fish!

There have been several major teething troubles with this engine which I could have done without, as I want to get back to my Terriers. Having said that the basic loco is made to a very high standard and once these problems have been sorted out, it will be a fine engine, and I can then finish the tender.

[steamer5]

Hi Ed,
Another thought……the axel spacing is going to be issue, I built a Toby Tram & spaced the axels out a little more than drawn to balance the loco up, no issue with nodding, another guy built his as per the drawing & had the “nodding issue”. Given that you can’t do anything about the axel spacing, & as you rightly point out the firebox end is going to be heaver than the smoke box, as it stands does the loco sit level or slightly down at the rear, is it possible to add extra weight to the front of the loco? Suggest a temporary lash up to see if it helps……or makes it worse! Maybe on the spring front some slightly firmer springs on the rear axel boxes may help……. Mind you working leaf springs would be nice.
The Hunslets are a lovely looking loco…..I have first refusal on a 5” one…….maybe one day!

Cheers Kerrin

[Roger]

Sept 25, 2021 22:03:26 GMT terrier060 said:

Forgive the crude sketch Roger, but I may be misunderstanding the physics, but would not the spring arrangement on the above sketch be more stable that the lower one, as the springs are spaced further apart and the outermost springs are nearer the ends of the loco frames therefore bearing on the frames 6 inches wider than the wheel centres?  The double line at the top represents angle iron bolted to the frames.

Spring centres by ed cloutman, on Flickr

Hi Ed,
I can't see how that makes any difference. The axlebox only sees what's attached directly to it. If the combined rating of the two springs matched the rating of the one spring on the bottom, how would the axlebox be able to tell the difference?
The diffference in the performance can only be the spring rating and the type of springs, ie more damping with leaf springs than coil springs.
Maybe the rating of a leaf spring changes with deflection? I suspect the difference in performance you're seeing is just due to the spring rating.

It would be interesting to measure the spring rating of the locomotive that performs well. You'd need to measure the distance the axle moves and the change of load that the wheel is seeing. That's probably only possible using a weighbridge.

[terrier060]

Hi Roger

Image I am standing on the axlebox with my one arm above my head balancing the frames on it. Very unstable.

Imagine the same situation but both arms spread out in a Y above my head holding the frames. Is that not more stable?

The bottom sketch shows a modification I will do if I revert to the Milner design. It combines the spring with a piston in a tube acting as a shock absorber.


Stability by ed cloutman, on Flickr

[Roger]

Sept 26, 2021 7:39:09 GMT terrier060 said:

Hi Roger

Image I am standing on the axlebox with my one arm above my head balancing the frames on it. Very unstable.

Imagine the same situation but both arms spread out in a Y above my head holding the frames. Is that not more stable?

The bottom sketch shows a modification I will do if I revert to the Milner design. It combines the spring with a piston in a tube acting as a shock absorber.


Stability by ed cloutman, on Flickr

I can't see that it makes any difference. The axlebox can only move up and down.

[suctionhose]

For the third and last time, use stiffer springs!

[terrier060]

Sorry Ross - see paragraph three at the beginning of the thread.  I have already tried that and it made things worse.

[smallbrother]

I was puzzling over this on a long dog walk just now and unless you increase the wheelbase I can't see how you improve stability.

Like Roger, I think the position of the springs won't affect it.

Perhaps some extra weight either fore/aft may balance things up better?

Pete.

[Roger]

Sept 26, 2021 9:03:39 GMT terrier060 said:

Sorry Ross - see paragraph three at the beginning of the thread.  I have already tried that and it made things worse.

It sounds like something was preventing the heavier springs from doing what they were intended to do. It's worth another look at the setup with those to see what the problem is. Maybe there's just not enough travel?

When you say 'made things worse', what exactly do you mean by that? Is it rolling around just as much, or just derrailing? If it's rolling around, it sounds like the springs aren't significantly stiffer than the originals.

[ettingtonliam]

Whatever theory says, if the basic difference between the 2 locos is that the bouncy one has coil springs acting directly on top of the axleboxes and the stable one doesn't, then change the bouncy one to the original Milner layout.

[Roger]

Sept 26, 2021 11:37:24 GMT ettingtonliam said:

Whatever theory says, if the basic difference between the 2 locos is that the bouncy one has coil springs acting directly on top of the axleboxes and the stable one doesn't, then change the bouncy one to the original Milner layout.

I'm afraid that doesn't make sense to me. There's a good reason for the difference between the two, but it's not the place that the force is applied to the axleboxes. That simply can't make a difference, it has to be something else.

[ejparrott]

Leaf springs are better than coil. Period.

Bounce is always always always down to wrong spring rate. How much does the spring deflect when you lean on the cab roof in a 'gently resting' pose, and how much if you put your back in to it

[Roger]

Sept 26, 2021 13:11:43 GMT ejparrott said:

Leaf springs are better than coil. Period.

Bounce is always always always down to wrong spring rate. How much does the spring deflect when you lean on the cab roof in a 'gently resting' pose, and how much if you put your back in to it

If that were true, then all vehicles would have leaf springs. In fact they all have coil springs and dampers. Leaf springs are only better on a vehicle if there is no other form of damping. Locomotives are the only vehicles I can think of that don't have any additional damping. Presumably that's because the springing is very stiff and there's only a small amount of travel.
Friction is a poor damper compared to hydraulic forms, it adds stiction into the system which is undesirable. All modern rolling stock has springs and dampers.

[uuu]

If stiffer springs have made matters worse, why not try softer ones? I've driven softly-sprung locos, which wallow gently, rather than bounce.

There may be other things that may be coming into play, in generating a difference between the two locos. Has one got more friction in the horns? Some locos with spring beams and twin springs have a tendency to restrain side-to-side rocking - the beams and spring hangers have restricted wiggle room. Just ideas.

Wilf

[ejparrott]

Sept 26, 2021 13:20:29 GMT Roger said:

Sept 26, 2021 13:11:43 GMT ejparrott said:

Leaf springs are better than coil. Period.

Bounce is always always always down to wrong spring rate. How much does the spring deflect when you lean on the cab roof in a 'gently resting' pose, and how much if you put your back in to it

If that were true, then all vehicles would have leaf springs. In fact they all have coil springs and dampers. Leaf springs are only better on a vehicle if there is no other form of damping. Locomotives are the only vehicles I can think of that don't have any additional damping. Presumably that's because the springing is very stiff and there's only a small amount of travel.
Friction is a poor damper compared to hydraulic forms, it adds stiction into the system which is undesirable. All modern rolling stock has springs and dampers.

We're not talking about vehicles, this is a mostly-railway forum.