Advice re 1/8" bearings and coupling hook springs

[Penrhos1920]

What is the actual finished hole size in a 1/8" bearing for a standard axle? If it's 1/8" (3.175mm) then there's too much friction for smooth running and no play for axles to twist when running over a bump in one rail. Is 5 thou over about right? ie should I use a 3.3mm reamer to finish a bearing hole?

I remember Bernard Weller saying that a 40 wagon train used to extend by a wagon length as it started rolling as the coupling springs all took up the load. He claimed that the exactoscale coupling hook springs replicated this. However, the springs provided with Smith couplings are usually far too long and don't actually allow the hook to move except under massive tension. Has anyone found a reliable way of modifying the Smiths spring or a source of replacements that gives a realistic replication of the full size operation?

[Stephan.wintner]

Well clearly that depends on the actual size of the axle (3.175 mm? 3.180 mm?) And the degree of misalignment. I'd anticipate more like 0.013 to 0.025 mm (.0005 to .001 inch) clearance would suit, and I'd start tight, try it, then ream to suit.

Stephan

[ChrisMitchell]

For the springing of coupling hooks, perhaps a transverse spring from guitar wire might be a good approach : see the thread on the Pet Coke Hoppers for example…

viewtopic.php?f=23&t=7646&start=75#p99239

I think Justin Newitt does something similar

Regards, Chris

[davebradwell]

If you use a proper 1/8" reamer, made to appropriate standard, etc it should give you a hole that is between true size and 0.0003" over. Proper shaft material (not silver steel) will always be undersize (measure a Gibson axle) so they will always run nicely. 5 thou' over size is going to feel as if it's knackered and needs a re-build. This also applies to crankpins - the tradition of drilling out next drill size (0.1mm up) gives a bearing that already feels worn-out and 0.05 up is preferred while still quite loose.

A reminder that a 3.2mm reamer would be 0.12598" nominal size so already well clear.

There's a danger with coupling springs as they can cause the train to surge - the loco might be running smoothly but the brake van alternately speeds up and slows down and is a function of having any spring in the system. Kadee make springs to put between wheel and bearing on, say, 1 in 5 wagons I believe. It can be seen with Jacksons even with almost no give. Only solution is adding friction or eliminating the stretch which stores energy.

DaveB

[zebedeesknees]

My take on these is - wheel bearings - never fitted to frames, but in blocks sliding in guides. Therefore axle a close sliding fit in the bearing, a little 'slack' in the guides to allow the axle sufficient freedom in the roll plane. Crankpin bearings also close sliding fits.
I would dispute Dave B's assertion that coupling spring surge is a danger. After all, that's what the real thing did, and something I have been trying to achieve for decades. I use Exacto hooks drilled at the inner ends with some gold coloured springs from an old box marked 'Slater's', or where possible for a wagon a Smiths one in the centre pulled from both ends to the other end of the spring using drilled-out pinpoint bearing cups. This like the real thing too. The transverse spring is also a prototype idea, using multi-leaf springs. Slater's MR carriage kits use a p/b leaf doubling as buffer springs.

Failing all, winding your own with fine wire, p/b or guitar string, is not as difficult as it seems, once tried..

Ted.

[peterbkloss]

So can anyone suggest a good source for a parallel 1/8" reamer? resident in Norway I can have stuff sent via UK visitors but the supplier scene changing rapidly makes sourcing such things difficult for me, not really being an expert on tools ...

[Tim V]

Have a look at https://www.tracytools.com/ - I think I got my Dormer parallel reamer from them.

[peterbkloss]

So this one is what I am looking for?

1/8″ STRAIGHT SHANK HAND REAMER
£10.00

seems very reasonably priced ....

[Stephan.wintner]

So can anyone suggest a good source for a parallel 1/8" reamer? resident in Norway I can have stuff sent via UK visitors but the supplier scene changing rapidly makes sourcing such things difficult for me, not really being an expert on tools ...

Peter, that Tracy tools looks like a good site for many items.

I'll add, I have been a satisfied customer of Fohrmann, and being EU I think they will happily ship to you. They list both Norway and the UK on their shipping fees page. And they have many special model RR tools.

https://www.fohrmann.com/en/
https://www.fohrmann.com/en/reamer-d-1-49-mm-oe.html
https://www.fohrmann.com/en/reamers-cylindrical.html

I did not see a 1/8ths reamer there though. Perhaps I overlooked it.

Stephan

[Will L]

Wagon coupling springs. As an advocate of things sprung, you may be surprised to hear I don't believe there is any natural advantage to having springs behind your coupling hooks, or that they serve any really useful purpose. The traditional half inch long spring behinds a 3 link is, in any event, effectively rigid as far as our coupling forces are concerned. Ok reproducing the draw gear springing detail clearly visible on many more modern wagon chassis is a valid modelling objective, but what goes on under the floor of you average traditional 4 wheel wagon is another mater.

For our train running purposes lightly sprung buffer heads are much more effective at dealing with our coupling and buffering forces, give a better look in lots of circumstances, and should be enough to preventing buffering force induced derailments on corners. When we couple up 3 links there is always going to be a little slack, don't you get enough visible extension from that? When running 30+ wagon plus trains round Tony Mont's very hilly recreation of Buxton the available slack is quite enough to see the trains lengthen when climbing the banks and closing up on the way down. To get anything more realistic running than that your going to need a guard in his van with working brakes!

[peterbkloss]

So can anyone suggest a good source for a parallel 1/8" reamer? resident in Norway I can have stuff sent via UK visitors but the supplier scene changing rapidly makes sourcing such things difficult for me, not really being an expert on tools ...

Peter, that Tracy tools looks like a good site for many items.

I'll add, I have been a satisfied customer of Fohrmann, and being EU I think they will happily ship to you. They list both Norway and the UK on their shipping fees page. And they have many special model RR tools.

https://www.fohrmann.com/en/
https://www.fohrmann.com/en/reamer-d-1-49-mm-oe.html
https://www.fohrmann.com/en/reamers-cylindrical.html

I did not see a 1/8ths reamer there though. Perhaps I overlooked it.

Stephan

They only do 1.5/2.0/2.5/3.0 mm ... but Tracy looks good and I can get someone to bring one out for me!

But fohrman looks good for other things!

[Winander]

But fohrman looks good for other things

I've only looked at their home page but my eyes popped when I saw nearly £20 for a silicon mat that looks identical to one I got from ebay last month for £6.47 post free.

[davebradwell]

I've used Cutwel and Drill Services (Horley). Useful sites with a vast range of stuff and prompt delivery but they can't touch your £10 for a reamer.

DaveB

[davebradwell]

A further thought on this topic - if you're going to set your hornblock positions on the frames by the usual jigging method from the coupling rods, you want all the parts to be a very close fit to minimise the uncertainty of position that any slogger would allow. Running clearances should be added afterwards.

DaveB

[zebedeesknees]

Wagon coupling springs. As an advocate of things sprung, you may be surprised to hear I don't believe there is any natural advantage to having springs behind your coupling hooks, or that they serve any really useful purpose.

And you may not be surprised to hear that I disagree, Will. They served a purpose in the real thing, so we should be trying to understand and emulate that, within the mass restraints of our scale of course. It does mean getting the buffer spring and drawhook spring rates consistent, along with the masses of the vehicles.

To get anything more realistic running than that your going to need a guard in his van with working brakes!

We can do that with radio and battery power! Cost under £50 per brake van. Not sure how to get the fireman and guard to pin down the wagon brakes though, but those have been made to work with Masokits...

Ted.

[jjnewitt]

And you may not be surprised to hear that I disagree, Will. They served a purpose in the real thing, so we should be trying to understand and emulate that, within the mass restraints of our scale of course. It does mean getting the buffer spring and drawhook spring rates consistent, along with the masses of the vehicles.

But what was that purpose and how does it apply to what we are doing with something 76 times smaller? As I understand it springs on the real thing were basically there to stop the big expensive bit being broken. The real thing had to deal with a huge amount of weight and without the springs there would have been a greater chance of a vehicle being damaged in use. We don't deal with the kind of masses that will have that impact on out models. If I've missunderstood that I'd love to be educated.

I'll happily spring everything in sight but I draw the line at coupling springs. My couplings are rigidly fixed and will continue to be. I really don't see what the point in springing them is.

Justin

[grovenor-2685]

Once upon a time the only scale hooks available were the P4 (Studiolith) whitemetal castings. Without springing it did not take long for a heavy train to break the hooks. Springing them solved that so those that I fitted springs to are still in use. Not an issue now with proper metal hooks but I still think having a percentage of sprung hooks in a loose coupled train improves train dynamics in operation. Close coupled trains are another thing altogether, IMHO nothing looks worse than loose coupled passenger trains, but arranging hook and buffer drawgear to run with buffers in contact is very challenging, I chickened out and went for buckeye stock to allow use of KD couplers.

[Terry Bendall]

However, the springs provided with Smith couplings are usually far too long and don't actually allow the hook to move except under massive tension. Has anyone found a reliable way of modifying the Smiths spring

I rarely spring the coupling hooks I use but had a need to do so recently. I managed to reduce the length of the Smiths springs by holding the spring in a pair of tweezers and cutting with a disc held in a mini drill. No easy since sometimes the disc would catch the spring and pull it out of the tweezers and distort it but I only needed four. Some trial and error was needed to cut the spring to the length needed to allow the hook to move slightly.

Terry Bendall

[Will L]

Wagon coupling springs. As an advocate of things sprung, you may be surprised to hear I don't believe there is any natural advantage to having springs behind your coupling hooks, or that they serve any really useful purpose.

And you may not be surprised to hear that I disagree, Will. They served a purpose in the real thing, so we should be trying to understand and emulate that, within the mass restraints of our scale of course.

Ted,I think you know I would certainly agree with the general sentiment/approach you suggest, but as Justin comments I think the prime purpose was to prevent poor driving technique causing damage to wagons (i.e. pull the headstock off) and the relative strengths of our stock makes this generally superfluous, except when using white metal coupling hocks apparently.

[zebedeesknees]

Ted,I think you know I would certainly agree with the general sentiment/approach you suggest, but as Justin comments I think the prime purpose was to prevent poor driving technique causing damage to wagons (i.e. pull the headstock off) and the relative strengths of our stock makes this generally superfluous, except when using white metal coupling hocks apparently.

Indeed Will, and thanks. We need to separate purpose in the real thing and effect when represented in our models. I could perhaps have worded that better.
Irrespective of the real purpose, I want to see the effect in a model long freight as Penrhos suggested in his original posting. It's my train set...

By the way(1) I have many Exactoscale hooks in use and some in stock, but I never saw an Exactoscale spring, or method of fitting them.

By the way(2) Terry, I am sure that you are aware that shortening springs makes them stronger!

Ted.

[davebradwell]

In my live steam days, there was a saying that "you can't scale nature" and I suggest that will apply here. If you wish to fit soft springs so that the train can lengthen on gradients or whatever, that's fine but it will happen much faster and you'll probably just get demented surging unless damped by more friction.....which may cause its own surging...... It's basically a form of pendulum and will try and oscillate.

Do we know the couplings extended when under way or was that just when unsticking the load from rest?

DaveB

[zebedeesknees]

In my live steam days, there was a saying that "you can't scale nature" and I suggest that will apply here.

The version I heard decades ago was more mathematical - "You can't scale mass". Strictly correct, but not without a work-around.
I have a folder to hand... The main content is a photocopy of the complete article by one J.A.Newton which inspired me and others into 'Proportional Power Classification' (MRN Feb 1960) along with subsequent letters to the editor and others to me.
The key word is 'proportional', if we can settle on the weight of a scale ton in 4mm, then we could weight all our locomotives and stock such that the behaviour in movement satisfies. In their response in the April '60 issue, Messrs. Dawkins and Lyle suggested that 2.32g per proto ton would be appropriate by calculation, observing that Mr. Newton's locos, weighted empirically, were approximately double that.

From that, and drawbar testing observed at several Scalefora and at home, I have settled on a round and memorable 4g per proto ton for locos, and stock where possible. (Plastic opens are too light, and some cwm too heavy)

If you wish to fit soft springs so that the train can lengthen on gradients or whatever, that's fine but it will happen much faster and you'll probably just get demented surging unless damped by more friction.....which may cause its own surging...... It's basically a form of pendulum and will try and oscillate.

A bit like the real thing that I try to emulate. A freight guard's life could include quite exciting rides! It's all down to balancing the mass/friction ratios and the spring rates of the buffers and the drawhooks.

Do we know the couplings extended when under way or was that just when unsticking the load from rest?

LIfting a long loose-coupled freight from rest was a long process, as my ears confirmed, described in my article in the News recently (233?).
Gradients were an issue too. There's a lot more data to be found, but that's enough for now...

Ted.

[billb]

From that, and drawbar testing observed at several Scalefora and at home, I have settled on a round and memorable 4g per proto ton for locos, and stock where possible. (Plastic opens are too light, and some cwm too heavy)

This means a scale standard BR steel mineral wagon could weigh 30 or 95 grams depending on whether it was loaded or not.

Should there be a scale calculation for the density of coal?

[smardale]

The perils of ther sprung coupling hook...

The box van in this short video, is fitted with sprung coupling hooks. You can see the brakevan momentarilly catches on something and then surges forward with the extra energy stored in the spring, and of course the guard spills his tea.

https://www.youtube.com/watch?v=sMHFZ8t7xaM

(Still no excuse the vandalism that ensued later the same day)

[Alan Turner]

In my live steam days, there was a saying that "you can't scale nature" and I suggest that will apply here.

The version I heard decades ago was more mathematical - "You can't scale mass".

It's weight you can't scale not mass. That is to say you can't scale time within the context of what we do i.e. a dimensionally scaled model railway.

Unfortunately by only scaling dimensions you distort the dynamic response of the system.

regards

Alan