Making a Start - The Peak District Midland / Monsal Dale pre 1903

[Le Corbusier]

I have had another go ... but this time using 0.5mm nickel silver wire and some sleeve washers made from 0.7mm brass capillary tube with 0.5mm bore.

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This was quite an interesting exercise. Using the capillary tube sleeves encouraged the solder to flow even more. Because the drilled hole in the rail was .5mm the tube sat on the face of the rail. The solder has filled the drilled hole locking the wire in, flowed around the base of the tube and into the tube and also created a haunch around the tube. It appears to be a very strong connection To the naked eye it looks a fair bit neater than blown up like this for the photo.

My instinct is that the wire is about right at 0.5mm and the nickel silver is a little stiffer than it would be in brass.

[Armchair Modeller]

Looking very promising

[Le Corbusier]

I have been having a look at geometries with the switch drive.

I am relying on the trapezoid formed by the stretcher bars and switch blades to form a rigid unit with the soldering as above being strong enough to resist flexure and thus focussing the flexure caused by the point actuation to be accommodated within the switch rails beyond the planing. If the angles of the switch blades within the trapezoid are aligned with the stock rails correctly and flexure should be minimal.

I then want to see if I can work out a way of driving the blades using the rodding crank. The main problem here I think is that the rigid connection formed by the solder joint to the switch, will set up a moment stress on the joint unless the eccentric side to side movement is accommodated by some means. I have sketched up the geometry to see how much eccentric movement would occur at the junction between crank and drive rod to get a feel for the scale of the problem.

track plan.jpg

My drawing seems to suggest that the side to side movement within the drive rod, resulting from the pivot around the heel of the switch, can be contained within 0.7mm (over a 15mm throw) ... so the actual degree of movement given that the drive rod is itself 0.5mm is 0.2mm. Given that the pin of the crank will have a degree of slop in it, my thinking therefore is to slot the drive connection hole in the crank so that it becomes elongated ... 0.6mm front to back and 0.9mm side to side. The thinking is that this will remove any moment stresses from the drive rod solder joint, allowing it to slide and find its own position in relation to the crank, also rotating within the locating hole.

If the drive throw has to increase to traverse an extra track before reaching the crank, then (by these calculations) the side to side movement increases to 1.07mm ... so a side to side slide of 0.6mm over the 0.5mm rod - dimensionally this could also be accommodated within the crank.

I would be interested in any thoughts/observations on this.

[Armchair Modeller]

Rather than a circular hole in the crank for the drive rod, use a slot. This would not push the drive rod from side to side - just backwards and forwards.

[Le Corbusier]

Rather than a circular hole in the crank for the drive rod, use a slot. This would not push the drive rod from side to side - just backwards and forwards.

I must have been unclear .... thought that was my plan above

[Armchair Modeller]

Sorry, looking at your diagram and not at the text

[Le Corbusier]

Ah .... sorry I can see how that could happen. Whenever I am lazy I always seem to get caught out ... the cranks as drawn are simply a trace of the Ambis cast cranks.

[Colin Parks]

Hi Tim,


Good work on the switch experiment. Now, I understand the theory regarding accomodating the radial movement of the drive rod by slotting the crank, but would not the same principle of movement need to apply to the round stretcher bars as well? It could be that the 0.5mm nickel silver rod will not flex sufficiently betweeen the switches to allow for this.

All the best,

Colin

[Le Corbusier]

Hi Tim,


Good work on the switch experiment. Now, I understand the theory regarding accommodating the radial movement of the drive rod by slotting the crank, but would not the same principle of movement need to apply to the round stretcher bars as well? It could be that the 0.5mm nickel silver rod will not flex sufficiently between the switches to allow for this.

All the best,

Colin

Colin,

Strictly speaking you are correct. The way I am hoping to get round this is twofold. Firstly, when soldering up the stretcher bars to the switch rail I have soldered firstly the stretchers into the straight switch rail whilst clamped to the stock rail and carefully aligning them at right angles to the switch. Then when soldering the stretchers to the curved switch, I have clamped the curved switch to the stock rail and fixed the heal temporarily with it pre-curved to describe the arc, - the other switch is spaced off the stock rail using the check rail gauge and clamped into position. There is sufficient play in the drilled hole through the switch blade to accommodate the slight change in angle at which the stretcher penetrates the switch. This means that the shape of the trapezoid formed by the switch rails and the stretcher bars, whilst being rigid, houses accurately into each stock rail when the points are thrown. The second part of the equation is within the procedure of the soldering. By housing the wire through the blade and using the additional capillary tube sleeve, the joint is remarkably strong ... so the trapezoid creates a strong 'box'. The theory is that this box will have no movement at all within it, but will move as a unit - because of this the small amount of flex required for the rotation will be accommodated within the rest of the switch blades .... so here I am accepting there is a moment force at the joints but creating joints strong enough to resist .... time will tell. I am working on the theory that the drive rod is much more vulnerable than the stretchers and this is where the failure is likely to occur ... so designing out the moment connection (it may be soldered but the slot and rotation at the other end in theory should remove any stresses).

I soldered up the first pair of switches tonight and everything appears to work as intended. Of course, even if my theory does work, I may still be binning everything and starting again because my filing of the switches is not up to scratch .... but we will see. All good fun anyway

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[Armchair Modeller]

The stretcher bars look really good. Shows the advantage of you not having to worry about insulating the rails from each other.

[grovenor-2685]

the other switch is spaced off the stock rail using the check rail gauge and clamped into position.

Whereabouts in the switch length are you doing this? If this is at the switch tips it will not allow sufficient switch throw.
The switch opening should be 4.25", near enough 1.5mm at scale, much more than a check rail gauge.
At the heel end the swich needs to be set by the track gauge, both open and closed. How are you planning to arrange the heel pivots?
The stretcher bars do look very nice.
Regards

[Le Corbusier]

the other switch is spaced off the stock rail using the check rail gauge and clamped into position.

Whereabouts in the switch length are you doing this? If this is at the switch tips it will not allow sufficient switch throw.
The switch opening should be 4.25", near enough 1.5mm at scale, much more than a check rail gauge.
At the heel end the swich needs to be set by the track gauge, both open and closed. How are you planning to arrange the heel pivots?
The stretcher bars do look very nice.
Regards

Hi Keith,

Thanks for the input. If I explain my reasoning perhaps you can let me know if you think I will have a problem.

I have set the gap at both ends of the planing ... ie at the tips and also at the end of the straight part of the set. The gap I have set is pretty much bang on 0.8mm. (this is with the gauge set bang on at 18.83). I have been reading up various threads etc on use of gauging and there appeared to be a consensus that to avoid the potential for tightening across the blades it is a good idea to employ some gauge widening through the turn out .... so I was planning on using a +0.2 gauge for the final installation ... so this would set the blades at a 1mm gap.

I was working on the premise that, though not prototypical, 1mm would be sufficient to work ... I was under the impression that the 4.25" on the prototype was to mitigate against any chance of the back of the flange coming in contact with the switch, as with the forces involved should that happen there would be a high likelihood that the stretchers would fail and spring the switch open ... so a good tolerance of safety was included? Obviously no such risk pertains to a model and with the running clearance in P4 set at 0.28 - 0.36 and the flange at 0.4, I thought 1mm would work? The reason for using 1mm as opposed to 1.4mm was to reduce the movement required of the switch blades and so reduce proportionately any stresses acting on the rigid welding up of the stretchers as I describe above. Would be interested to know if you think this is just courting trouble?

I may change it anyway because if it simply looks wrong, but on a preliminary set up I thought it looked ok.

I am still thinking about the heel .... for my era there is no connection back to the stock rail. Any thoughts you had would be helpful.

Tim

[John Palmer]

I am following your experiments with interest because my future plans involve modelling North British pointwork on which round stretchers seem to have been universally used.

If I have followed your plan correctly, you are proposing to put a slot into a scale-sized crank. To accommodate a 0.7mm lateral displacement of a 0.5mm drive rod the slot will need to have a length of 0.7mm + 2 times the radius of the drive rod (0.5mm) making 1.2mm in total. You plan to have a a slot width of 0.6mm to provide clearance on the 0.5mm diameter drive rod. All this in a crank arm measuring about 3-4mm by 1mm. I'm not going to say that this can't be done but it looks like a very difficult task to accomplish accurately and for that reason my own approach would be to look for some different way of accurately simulating those round stretcher rods, preferably one that allowed them to pivot on the switches to which they are attached so that any above-baseboard drive connection to them can be rigidly attached and will not have the lateral displacement with which you are having to contend.

Those tube sleeves you have used look very nice indeed. Just thinking aloud, if a shoulder were turned upon them that could be accommodated by the void between the back face of the switch and the web of the adjacent stock rail, you might have a means of attaching the stretcher rod to the switch rails that would not require a soldered joint and would thus have a built-in ability to pivot - something like this:

Stretcher design.jpg

Of course, this would itself involve some very fiddly work and for that reason may be impractical, but if it stimulates other, better designs it may be of some use.

The 4.25” switch opening Keith mentions seems to have been the product of an evolutionary process. Some pre-group companies made use of a smaller opening, a North British drawing, for example, shows an opening of only 3.5” for a 16' switch. It would be interesting to see a sharper picture of the Bow Branches switch drawings already posted in this thread, and see what the opening is for those loose heel switches.

I illustrated a possible method for pivoting a loose heel switch here: https://www.scalefour.org/forum/viewtopic.php?t=3677&f=7#p31553, and subsequent prototyping indicates that the method works well and probably helps to limit any tendency of tip of the switch to rise above the stock rail. Here is a picture of my prototype in which you can just about see the pivot tube that is soldered to the underside of the heel plate and passes down to whatever depth you see fit – beneath the bottom level of the track base, if you wish.

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I am fortunate in that NBR practice, unlike Midland, was to make use of such heel plates which when represented in model form help to make the tube carrying the pivot for the switch much less obtrusive.

[Le Corbusier]

Hi John,

Thanks for the input ... much appreciated.

HEEL PIVOT
The heel pivot you show is very neat. Interestingly (and it gives me some hope ) ... my thoughts on a pivot were similar - I was thinking to use a brass rail chair at this point and solder a rod through and down from the base, then soldering the chair to the rail (at the sleeper point just before the heel joint). I was then thinking of using a shouldered bearing within the rivet hole in the sleeper, and capturing the rod within the bearing by means of a soldered washer ... similar to the way a Romford crankpin captures the coupling rods .... I am still working on this as the pivot is offset from the rail end and fishplate, and I don't know yet how much the end will actually move. I am thinking of using exacto plastic fishplates to join the rail ends here and I think I will have to extend the fixed rail right through the fishplate and cut off the switch at the back of the chair .... hmmm! The other option I am looking at is much cruder ... to fix the heel solid to a rivet in the sleeper, with cosmetic chair to mask - and rely on the flex of the rail to provide the movement and rely on the soldered up stretcher bars to resist the applied moment.

SWITCH GAP
On the gap width between switch and stock rail, I have been back and re-checked the dims - the 0.8mm brass spacer I made up definitely fits between the switch blade and stock rail along the complete length of the planing ... so with 0.2mm gauge widening my figure of 1mm clearance is correct. I mocked the rails and switch up using gauges and clips and there appears to be masses of room for the wheel flange?

DRIVE BAR
I am looking to absorb the lateral movement of the drive bar at the crank because I don't think I have the fine skills to do much more than the soldering shown at the blade tips. I just came to the conclusion that soldering everything up solid would be more robust all round. I agree that you idea looks very neat, I just don't think I would be capable of making it

I calculated the required lateral movement for the drive rod at the crank graphically rather than mathematically. I drew to 3 decimal places the switch in the normal position and then rotated it in CAD to the alternate position around the heel ... this gave me the accurate position of the drive end in both situations. I did the same for the crank, and this allowed me to draw the required slot and measure it accordingly. Using 0.5mm wire I reasoned on a 0.6 hole to give some tolerance ... though I might get away with 0.55mm. The total horizontal slot required for the long drive bar traversing two sets of tracks measures 1.05mm ... so 1.1mm to allow tolerance. My plan was to simply drill two 0.55mm holes next to each other and join them. I reasoned that this could be done relatively simply to the cranks, and then the drive rod could be captured using the crankpin approach as above and a drop of clock oil. It will be interesting to see if this is over optimistic.

Edit ... I was assuming that for my period (1902) it would be likely that the cranks would be cast? as these....

cranks.jpg

There appeared to be plenty of meet to facilitate a slot for the drive rod.

Tim

[allanferguson]

"....The other option I am looking at is much cruder ... to fix the heel solid to a rivet in the sleeper, with cosmetic chair to mask - and rely on the flex of the rail to provide the movement and rely on the soldered up stretcher bars to resist the applied moment....."

Put a rivet in but don't squeeze it fully tight, just enough to hold it. That will pivot very nicely.

Allan F

[Le Corbusier]

"....The other option I am looking at is much cruder ... to fix the heel solid to a rivet in the sleeper, with cosmetic chair to mask - and rely on the flex of the rail to provide the movement and rely on the soldered up stretcher bars to resist the applied moment....."

Put a rivet in but don't squeeze it fully tight, just enough to hold it. That will pivot very nicely.

Allan F

Genius and so simple

Just the issue of whether the pivot will cause issues with the meeting of the rails as it isn't located at the rail end? The compromise would be to make the joint at the edge of the chair and have a cosmetic fishplate with a saw cut in the top of the fixed rail. Or it may be that the movement is so slight that a little judicious filing of the rail end coupled with the Exactoscale fishplate will mask things.

Edit - I have just experimented to get a feel for the movement about a rivet pivot and it really is minimal ... enough to relieve stress in the rail but with very little filing to slightly round the edge & I would be surprised if it is an issue.I have just mocked up the movement of the blade graphically on a my templot export in CAD to 3 decimal places. With the switch to stock rail gap set at 1mm, the throw from the true line between the centre point of the rivet and the end of the rail is 0.04mm. It will be interesting to see if this is at all noticeable. If the blade is set at the half way throw for fixing the rivet, this sets a deviation of 0.02mm both ways, which I find it hard to believe will be readable - even at full size that would only be 0.06" which is less than a 1/16". (

[Le Corbusier]

Right,

I have had an experiment with Alan's suggestion using the rivet as pivot ... It works very well. Rather than trying to fit the rivet loosely, I fitted it securely and then soldered on two short lengths of rail. It only too a few rotations backwards and forwards and the rivet freed up nicely as a pivot in the sleeper. I have filed back the rivet to see how good the bond is and it is still nice and strong, so it should be easy enough to sino glue some cosmetic chairs to the rail which will also rotate. (obviously I will wait to file the actual installation when all is in situ). A quick touch of the iron easily releases the short rail pieces used to free up the rivet, allowing it to be bonded in place ready for the track - I can't use the blades themselves to free up the rivet as they are already linked via the stretcher rods.

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I think this is a nice simple and robust way of securing the heel and at the same time providing rotation. So the only stress left in the set up will be the minor displacement caused by the separate pivot points of the two rails ... and I am going to rely on the strength of the stretcher bar soldering to deal with this. Now on to Ballasting so that I can start to install the track work and see if it works.

[RobM]

Now on to Ballasting so that I can start to install the track work and see if it works.

Did I read that right ........ballasting then install the track work or did you mean that you were going to do some test ballasting before moving onto the plank?
Rob

[Le Corbusier]

Now on to Ballasting so that I can start to install the track work and see if it works.

Did I read that right ........ballasting then install the track work or did you mean that you were going to do some test ballasting before moving onto the plank?
Rob

Rob ... the whole thing is a test I am having a go at Howard's approach. ie constructing assemblies rather than the whole track on the templates. Then laying the sleepers and ballasting having dry assembled the track and dismantled. When the ballast is dry, then fixing the track down permanently. Only works if the track is built on the baseboard.

Chris did the same on Cadhay ... see ...https://www.scalefour.org/forum/viewtopic.php?f=9&t=3774&start=50 towards the bottom of the page.

Thats the plan anyway.

[RobM]

Gotcha Tim......I use Howard's method of pre-fabrication to a degree but with some of my own methods..........
Rob

[Le Corbusier]

Could I ask anyone who happens to model the limestone area of the Peak what ballast mix they use. I have been trying methods for laying the ballast and I think that the method suggested by David Thorpe over on Colin's track building thread is working best for me, ... Edit - I have been looking closely at Dave Frank's ballasting and his method over on his RMweb thread for Wharfeside - I am currently having an experiment with this. The pre war images I have for ballast on the Monsal Dale line all show quite a fine mix but with larger pieces showing through and areas between tracks which almost appear as a compacted hardcore material. I am hoping Dave's method will allow me to vary the mix during the application prior to glueing down. Dropping the ballast mix onto glue already laid down doesn't allow for this subtlety and just making up a part fine and part medium ballast mix doesn't give the effect I am looking for. ...but as of yet I have been struggling to find a mix which is redolent of the limestone peak.

Any suggestions of possible sources much appreciated. I have just received back confirmation from Lindsey at Attwood Agregates that they now have some limestone stone sourced from Buxton and am awaiting delivery of a sample of the ballast ... which will be interesting. viewtopic.php?t=4951

[grovenor-2685]

Hi Keith,
Thanks for the input. If I explain my reasoning perhaps you can let me know if you think I will have a problem.

Tim,
Sorry I'm a bit slow replying to this but I will in the next couple of days, needs some photos and/or diagrams and some thought. And i just got back from holiday and need to sort some things out.
Regards

[Le Corbusier]

I have another question to put out there on the topic of Ballasting, and particularly pre-grouping ballasting. All the photos I have show the ballast as being quite different from the regularity of later ballasting .... for example

Monsal Dale Station Ballast.jpg

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Ballast 4_zpshh0fhmdz.jpg

The ballast is quite a mixture and from what I have read it would appear that a finer layer was put on top of the main ballasting. This means that over time in areas the larger ballast projects through in some places and in others it takes up the appearance almost of compressed hardcore. The Monsal Dale picture certainly shows this variation.

Has anyone developed a technique to try and simulate this?

From my experiments, putting the glue down first and then scattering the ballast on doesn't give any real control over the varying textures/sizes and is pretty hit and miss if you use a variegated mix within the ballast. Building up the ballast dry and then using a dropper is better, but the application of the dropper has a tendency to wash the finer granules below the larger ones and gives a rougher impression than desired.

Maybe I need to build up the process working from course to fine, perhaps using some sand for the almost smooth areas? If anyone has any thoughts, or has themselves manage to simulate what I am after, I would much appreciate the input.

Tim

[TonyMont]

Hi Tim,

For this type of ballast I intend to use floor tile grout, it occured to me a few years ago, but as yet I have not tested it.

Regards, Tony.

[Le Corbusier]

Hi Tim,

For this type of ballast I intend to use floor tile grout, it occured to me a few years ago, but as yet I have not tested it.

Regards, Tony.

Hi Tony,

Floor grout as the glue? or as the ballast? .... sounds interesting - I am curious. I would be interested to hear the thinking.

Tim