Chuffer's Workbench

[Chas Levin]

Three fine looking models packed with interesting engineering - no thanks needed for reading, it was a pleasure!

[Chuffer Davies]

A progress update on the installation of the Airfix turntable on our Clayton layout. I have now cut the well into the top of the baseboard and installed the turntable in it.  As previously mentioned, the Airfix turntable was chosen because it requires a very shallow well, approximately 6.5mm in our case, which meant the well could be milled into the 10mm thick plywood top of the baseboard.  Once installed the rails radiating away from the turntable were laid.  Each was aligned by eye by looking along the turntable to ensure the rails were straight on to the deck.  The feed line unfortunately is on a curve, but fortunately the radius is around 4' 6" so I just have to hope that there wont be an issue getting locomotives on and off the table.

 

When in use it is envisaged that the table will be operated from the main fiddle yard control panel, but the operator needs to be right next to the table to set up the initial indexing of the stepper motor.  It has therefore been necessary to build a local panel specifically for setting up the table.  The panel consists of three layers: the base is a sheet of 1mm steel which has been drilled for the switches and LEDs as well as 4 countersunk holes in the corner for attaching it to the baseboard.  The middle layer is simply a sheet of paper with all the labels for the switches printed on it. The panel's top layer is a piece of 1mm clear Perspex.  I have previously had bad experiences when trying to drill holes into thin Perspex and so I clamped the Perspex to the steel base plate and the holes for the switches and LEDS were cut out with a fine bladed piercing saw using the holes in the steel plate as a guide.  A hole sufficient to clear the switches was cut in the baseboard and the steel plate was attached to the baseboard with 4 wood screws.  The paper and Perspex were then placed on top and the switches installed to retain the Perspex top.  As of today all the above board installation of the turntable is now complete including the buffer stops which are actually right angled plastic brackets for kitchen cabinets from B&Q.  

The wall behind the turntable is a portion of the spiral carrying the running lines the 7 inches down from the top end of the scenic section of the layout back to the level of the fiddle yard.

 

I still have a lot of wiring to do under the base board so I now look forward to several back breaking hours sitting under the layout to wire it all up.

 

Frank

[Chuffer Davies]

After discussing how to install 'stay-alive' with Karl Crowther the other week, I have started installing it retrospectively into the model locomotives I have been building for Clayton (EM).  Just for the fun of it I decided to carry out a simple experiment to get a feel for just how effective this facility is.  As with all the tender engines I'm building, current collection is by means of the wheels on the nearside of the locomotive and the offside of the tender (the American System).  My models fully sprung using Continuous Springy Beams (CSBs).  The loco is fitted with a Zimo MX617 decoder and the stay alive comprises a Zimo 5800uF Capacitor and YouChoos Lifelink.

 

The experiment was achieved by laying a rectangle of tissue paper, 5mm longer than the wheelbase of the locomotive, across the track to interrupt current collection.  The locomotive was then driven at a slow constant speed over the tissue paper to see what happened.

I think this adequately demonstrates the benefits of the stay alive facility.  Obviously if the model is stationary and has lost connectivity at that point, the decoder won't receive the instruction to move, but as long as the model receives the instruction then the Stay Alive will kick in.  Unloaded there is enough capacitance to turn the driving wheels through approximately 540deg. 

 

I also wondered whether the Stay Alive would help when running the loco under Analogue control?  As suspected the decoder interpreted the loss of power as the controller being returned to zero and the loco stopped moving.  You can't win them all!

 

Frank  

[Chuffer Davies]

After my success with the design and build of a M-I-T (Motor-In-Tender) replacement chassis for Dapol's new Great Western Mogul, I was contacted by Pendon Museum with a request to build a replacement chassis for one of their locomotives originally built by Guy Williams.  The model in question is a 2-8-0 ROD.  Guy intended that this would be the backup for his famous 28xx locomotive built to haul the long mineral train (90+ wagons) on the Vale scene.

 

The model first featured in a Model Railway Journal article - edition 96.  Guy built the model for the article and as such it was in the original Robinson's design.  From the outset the model was built with the motor installed in the tender driving the loco's wheels through a drive shaft running below the fall plate. 

 

Some time later Guy decided to recreate history in model form and rebuild the model in its 'Swindonised' guise so that it could run at Pendon.   At the time Guy suggested that the chassis should be good for about 30 years which appears to be a reasonably accurate prediction.   I have been asked to provide a total replacement set of frames for the model.

 

My first task was to prepare the CAD artwork for the frames so that they could be etched in Nickel Silver.  As usual my start point was to import several work's drawings of the ROD into the CAD desktop and to then scale them to 4mm/ft in CAD so that the components could be drawn over the original engineering drawings.  Once complete the artwork was sent to PPD Ltd so that they could create the photoetch tool prior to etching the metal for me.

 

At the heart of the M-I-T solution is a simple 'U' shaped fold-up cradle in which all the drive components are mounted.  The cradle is designed to be installed as a unit by soldering it between the tender's frames.  Once soldered in place the cradle's bottom stretcher is removed.  The drive system is designed specifically around High Level's 13/20 coreless motor and a pair of High Level spur gears.  The drive shaft to the locomotive is supported in a pair of ball races.

 

The thin slots either side of the mount are clearance holes for CSB wires where fitted.   

 

I have just completed the build of the tender's chassis, including the test installation of the M-I-T drive system.  The M-I-T components cannot be permanently installed until after the frames have been painted so as to avoid paint contamination of the ball races and gears. 

 

The steel ball on the end of the drive shaft is part of a ball and socket universal joint available from Markits.  

 

When fitted to Guy's tender it is apparent that the drive shaft in my solution is mounted significantly lower than that of Guy's.  His solution can be seen in his MRJ article.  

 

 

Having completed the build of the M-I-T tender I have now started work on the loco's frames.  Early days as yet but so far so good.

 

 

I will provide further updates as the build of the loco's frames progresses.

 

Thanks for visiting.

Frank

Edited January 7, 2023 by Chuffer Davies
spelling

[57xx]

What a great appreciation of your talent to be asked to re-chassis that model. Great stuff!

[Chuffer Davies]

I have been asked to describe the process for ultrasonically cleaning models prior to painting.  Ultrasonic baths are widely used commercially for cleaning jewellery, clock mechanisms, glasses and any number of other things.  These are now increasingly used domestically.  I purchased my ultrasonic bath from RS Components but I'm sure there are many other retailers from whom they can be purchased.

 

 

The first stage in the process is to strip the model down as far as possible and give it a clean with traditional cleaning methods.  In my case I use a baby's soft toothbrush and SIF cream cleaner. 

 

I fill the bath with 10/1 mix of warm water and specialist cleaning fluid, approx 1.1 litres is required to ensure that the various parts of the model are fully immersed.  Marigold (or equivalent) gloves are essential as the cleaning fluid must not come into contact with skin.

 

 

The bath comes with a plastic tray but apparently the tray reduces the power of the bath and so I choose to place the model in the bath without the tray.  Everything goes into the bath including the wheels (Gibson in this case) but not the motor or gearbox.  In operation the model will vibrate around the bottom of the bath.  This is probably a good thing because anything that is not properly attached will be shaken loose and drop to the bottom of the bath.  

 

I clean the model for two x 8 minute cycles.  As can be seen from the following picture It is surprising how much muck comes off in the bath despite having cleaned it with SIF before hand. 

 

 

On completion, and again wearing rubber gloves, I thoroughly rinse the cleaning fluid off the model with water and then after touch drying with kitchen towel I first dry the model as far as possible with a hairdryer before placing it in the airing cupboard for a minimum of 24hours to ensure that any water that might be trapped inside the boiler etc, is completely eliminated.   This is especially critical for any steel parts such as the tyres of the wheels and the axles to avoid them rusting.

 

The model is then ready for painting, or in my case, for sending off to be professionally painted.

[Chuffer Davies]

I have already posted a picture of my latest model on Wright Writes, but felt readers might be interested in some additional pictures and information about this new model.

 

 

A year or so ago I posted a picture of a J52 that I had built from a set of my own etches.  At the time I thought I’d done a good job but it subsequently transpired that I’d made some errors in my design, specifically I’d given it an Ivatt cab instead of a Stirling, there was some detail missing from the cab roof, and the footplate was 2mm too wide.  I discovered these errors during a conversation with Paul Craig.  Paul has spent many years researching GN locomotives and is responsible for the design of several of the GN/LNER kits available from London Road Models.

 

It transpired that Paul was in the process of designing a J52/53 kit for LRM.  He convinced me that I needed a second J52 for Clayton, and I might like to test build his model rather than correct my original etches.

 

Whilst I discovered a few errors in Paul’s test etches there were no showstoppers.  Any mistakes discovered were reported back to Paul, along with occasional suggestions as to how the design might be simplified/improved.  In particular I have recommended that the superstructure should be made up from three distinct sub-assemblies these being the footplate, the cab/bunker, and the smokebox, boiler, firebox assembly.  The reason for this being that it makes the model easier to break down for painting and lining, and it also gives easy access to the inside of the cab for adding glazing and engine crew.    

 

A key feature of the new kit will be a 3D printed saddle.  Initially I intended to build this model with the printed saddle and got as far as installing the hand rails.  Unfortunately it subsequently transpired that the saddle supplied was dimensionally incorrect, and in the interests of maintaining momentum I replaced it with an etched saddle from my own J52.

 

 

 I have since received a replacement 3D printed saddle and have been able to test fit it to confirm that it is dimensionally correct.  In addition to the saddle the kit will also feature a completely new bespoke set of castings including those needed to represent the condensing gear.  In my opinion these new castings are as good if not better than any castings I have ever seen before.

 

Whilst the prototype is a humble tank engine, as a model it is possibly the most complex locomotive I have ever attempted to build because of all the pipework and levers adorning the outside of it.  Construction of my model is at last complete and I have now dismantled it for cleaning prior to sending it off for painting.

 

Some more pictures:

 

 

[Dave John]

Superb brassmanship.

 

I would agree totally with your comments on ultrasonic cleaners, wonderful things . 

[EasternO]

This is a fantastic thread by an exceptional craftsman. I'm looking forward to more content.

[polybear]

On 02/02/2023 at 00:00, Dave John said:

I would agree totally with your comments on ultrasonic cleaners, wonderful things . 

 

On the subject of U.C's, what are considered to be good (and not so good) models to look for?

[Dave John]

I don't want to clog up Chuffers thread , so I'll just post a lonk to the discussion ;

 

 

[Chuffer Davies]

Most readers will already have seen a picture of my new J50 on Wright Writes.  This model was scratch built in OO gauge by John Edgson and I assume it must have been a commissioned model as it was owned by a third party until their collection was sold on behalf of their estate by Tony Wright.

 

 

When I acquired the model my first task was to identify a suitable prototype shedded in the West Yorkshire area in 1930.  I settled on 586 which was a Bradford loco.  As far as I could determine the safety valve on 586 in 1930 was not pedestal mounted but the water filler caps were, the reverse of John’s model.  I decided to correct these details but there was a third discrepancy that I chickened out of.   This was the vacuum ejector pipe exiting on the offside of the smokebox on John’s model but on the actual prototype it should be on the nearside.  On John’s model the pipe runs under the flashing covering the gap between the boiler cladding and the top of the side tank.  To remove it from the offside and to reposition it on the nearside would have caused too much damage.  Most people viewing the layout will be unaware of this discrepancy and I’m prepared to live with it.  I also decided to replace the scratch built opening smokebox door so characteristic of John’s models.  On this particular model I felt the door was rather too bulbous.  The new cast door looks much better in my opinion. The only other modification to the loco’s body was to pack it with as much lead as possible.  This is because the loco needs to be able to haul prototype trains up the 1:50 gradient on our layout.

 

 

I model in EM and so the model needed converting.  The rigid OO chassis would have needed a lot of work to bring it up to standard and at the same time I was aware that Chris Gibbon at High Level had, for several years, been working on a J50 chassis kit for the Hornby model.  I decided to wait until this was available.  As soon as his kit was launched (in early 2022) one was purchased and within a couple of months I had a replacement chassis built reusing the Sharman wheels from John’s chassis.  I would normally build tank engines with a split frame chassis, but Chris’s design with removable spring hangers to permit the axles to be dropped, was sufficiently complex to make conversion to split frame difficult.  I therefore decided to build the chassis as per Chris’s original design installing my preferred ‘back scratcher’ pickups behind the offside wheel rims, shorting the rims of the nearside wheels to their axles making the chassis live.   The main features of the chassis are CSB suspension, and a HL 1320 coreless motor driving through an integrated 47:1 High Level gearbox.  The model is wired for DCC using a Zimo MX617 decoder.  These are currently like the proverbial rocking horse to purchase and I only have one left in the spares box so I hope the decoder shortage ends soon.

 

 

The model has now been painted by Ian Rathbone and I have carried out final assembly.  It is always a relief when the chassis is assembled with successfully quartered wheels Loctited to their axles, and lubricated bearings. I can then establish for the first time how well the chassis really performs.  On Thursday I took the model to club and ran it on the layout with a test train behind it.  It was loaded with 25 wagons but I am confident it is capable of hauling a lot more.  As you can hear on the following video the model has a slight ‘growl’ in the forward direction but it is silent in reverse.  I'm sure that under exhibition conditions it will be inaudible. The model performed faultlessly and so it will now be added to the locomotive fleet for Clayton (EM).     

 

 

[Chuffer Davies]

Hurray!  I've at last managed to get the ROD's chassis back to the top of the pile.  As far as possible I try to work on the 'one project at a time' principle but at the end of 2022 I uncharacteristically had 3 projects at different stages.  There was the re-built John Edgson J50 away with Ian Rathbone for painting, the test build of the J52 kit for Paul Craig was stuck awaiting delivery of the remaining castings, and so to use the time productively I had started work on assembling the ROD chassis, having prepared the CAD artwork and had it etched much earlier in 2022. 

 

In January the J52 castings arrived and work on the ROD was interrupted in order to complete and sign-off (so to speak) the test build for Paul Craig.  I also wanted the J52 finished so that it could be sent off for painting.  Just as I was about to contact Mr Rathbone regarding the J52, Ian pipped me to the post and emailed me to say the J50 is ready.  The two locos passed in the post and the ROD was again pushed back so that I could carry out final assembly of the J50.

 

Its been a couple of weeks now since I picked up the ROD once more and I have now successfully test fitted the driving wheels and coupling rods and have built the pony truck.  Unfortunately I've had to build the pony truck twice.   The first time, when I test fitted the wheels, I discovered that the pony truck was too wide by approximately 1mm.  I therefore had to replace the frame spacers before adding the spring detail.  The prototype truck has both leaf and coil springs and not having the ability to make castings I have had to attempt to recreate the detail using a combination of etched parts and other bits and pieces.  I think the end result is a reasonable representation of the real thing, but once the wheels are added the detail is all but obscured.  Some may feel it wasn't worth the effort but I would suggest that adding such detail is very much in keeping with the Pendon ethos.

 

 

 

Next update will be when I've built and fitted the cylinders and slidebars.

 

Bye for now,

Frank

    

      

[polybear]

On 09/01/2021 at 20:54, Chuffer Davies said:

Unfortunately, I have not been able to find a supplier of 0.7mm half round N/S and so I make my own from 0.7mm wire held in a homemade jig.

 

Metalsmith sell it in brass, along with 0.8mm and 1.0mm

HTH

[Chas Levin]

13 hours ago, Chuffer Davies said:

The prototype truck has both leaf and coil springs and not having the ability to make castings I have had to attempt to recreate the detail using a combination of etched parts and other bits and pieces.  I think the end result is a reasonable representation of the real thing, but once the wheels are added the detail is all but obscured.  Some may feel it wasn't worth the effort but I would suggest that adding such detail is very much in keeping with the Pendon ethos.

 

 

      

Eminently worth the effort Frank in my humble opinion. That's the kind of detail that those who look for it always spot and those who don't wouldn't miss anyway!

 

It's a beautiful sight.

[Chuffer Davies]

 

A bit more progress on the chassis for Guy's ROD.  I have now built the basic cylinder/slide bar assembly along with the crossheads and connecting rods. It all went together as designed but when attempting to install the assembly into the frames it became apparent that I am going to have problems fitting the front brake hangers because the rear cylinder covers are obstructing the space where I expected to install the hangers.  I'm not quite sure how this will be resolved but I'm sure I'll come up with something.

 

As with any typical eight coupled model with outside cylinders, where the connecting rods are attached to the 3rd axle, I had clearance issues between the back of the connecting rods and the crank pin nuts on the 2nd axle.  Bushing out the connecting rod sufficiently to clear the standard Ultrascale crank pin nut looked wrong.  Instead I decided to turn up some alternate (non-standard) crank pin bushes in the lathe and tapped 14BA, as per the attached photo. 

With these installed on the 2nd axle and a 0.4mm thick washer between the coupling and connecting rods on the 3rd axle, the connecting rods now clear the crank pins albeit by about 0.1mm.

 

I'm not quite on the home straight yet as I still have the leaf springs, brake gear and draw bar to install.  There is also the vexing question of what to do about the valve gear and associated eccentrics between the frames? 

Regards,

 

Frank         

[Buhar]

On 22/09/2021 at 22:41, Chuffer Davies said:

 

Hi Frank

 

Please can I check my understanding of your M-I-T system? The tender mounted motor transfers its drive to the shaft to the loco via spur gears with no reduction so the shaft runs at the motor’s original rpm. The 2mm steel shaft is supported with two ball-race bearings fore and aft under the motor cradle. The initial flexible joint in the tender is a length of tubing (currently and for the foreseeable) Caldercraft Coupling Rubber and from there that is a length of steel shaft that will extend under the fall plate to the ball joint part of a Markits universal joint positioned so it will connect to the socket part of the universal joint under the loco footplate.

 

In the loco the socket part of the joint is attached to a steel shaft supported by two further ball races either end of the gearbox which is a High Level Roadrunner Compact+ which has the worm and a spur gear set-up.

 

Now to the questions:-

 

I presume that as the gears in the tender are spurs there is no need to and end thrust bearing, but what about in the loco? I can’t see one and so presume there are no issues as the thrust delivered by the motor is absorbed by the tubing and the UJ.

 

Is the shaft from the tubing to the ball joint part of the Markits joint or have you removed the ball and refitted it to your own shaft?

 

If the slotted tube at the loco end Markits or your own concoction?

 

Is the shaft in the tender after the tube supported only by the tube?

 

How do you fix the miniature ball races which I presume are a steel casing?

 

How do you arrange the loco to tender coupling? Is it a simple pin and hole that you can drop together after you’ve encouraged the ball into the socket?

 

You indicate that by ensuring the shaft runs under the loco footplate the system works with driving wheels 5’2” or less and that 6’10” or more may be possible with an inverted gearbox. Inevitably, I’m looking at 6’0” or 6’6” 4-4-0s (small boilered Scottish engines) plonking the underside of the driving axles at 11mm to 12mm above rail height, bang in the way and with the rear axle so close to the cab that any gearbox would intrude. Have you had any thoughts about this, maybe somehow getting under and up to the leading axle or would I be stuck with a shaft from tender coal door to firebox door (as has been done).

 

Many thanks for your explanations so far and for you inspiringly tidy and practical work.

 

Alan

Edited March 14, 2023 by Buhar
Failed to remove quote box

[Chuffer Davies]

Hi Alan,

I'm pleased to know that you are interested in my M-I-T system.  I will attempt to answer all your questions but inevitably some answers may trigger additional questions from you so feel free to keep asking them until you are satisfied.

 

I'll start by correcting a couple of points in your initial description of the system. 

 

I have to use a 1.5mm shaft in the tender and the Road Runner+ gear box because I was unable to source any ball races with a 4mm o/d and 2mm i/d.  The ball races I use are 4mm o/d and 1.5mm i/d meaning that I am then forced to use a 2mm o/d x 1.5mm i/d sleeve on the shaft to mount the High Level spur gears.  The ball races are needed because, as you have identified, the drive shaft rotates at the same speed as the motor and a brass bearing (unless it was sintered brass) would quickly overheat at that speed.

 

The socket of the ball and socket UJ is located in front of the loco's rear chassis spacer, not under the fall plate.  The N/Silver frame of the High Level gearbox is a replacement that I have designed (with the help of Chris Gibbon) to accept the ball races.  I don't think there is enough metal on Chris's  RRC+ gearbox frame to drill out a 4mm hole for the front ball race and the back hole may already be too big (not sure though).

 

Now to your specific questions:

End thrust: The ball races appear to be capable of accepting an amount of end thrust and so I have fitted sleeves fore and aft of the gearbox frame, and pushed up against the ball race at each end to absorb the end thrust.  This has not been a problem so far......   The ball of the UJ is located approximately half way into its socket and does not manage any end thrust.

 

Drive shaft:  The Markits UJ comes in 2 sizes: 1.5mm or 2mm.  This dimension only applies to the hole in the end of the socket but the ball always comes with a 1.5mm hole and a length of 1.5mm steel shaft.  The length supplied is only sufficient for the shaft between the two UJ's.  I have to purchase additional 1.5mm rod for the High Level gearbox and the spur gear's shaft.

 

Slotted Shaft: By this I assume you mean the socket of the ball and socket UJ.  This is part of the Markit's product.  It also has a grub screw to lock the socket onto the end of the gearbox's drive shaft.

 

The central part of the drive system between the UJ's is supported solely by the UJ's as it needs to move horizontally and vertically as the relative positions of the loco to the tender changes.

 

Mounting the Ball Races:  I use Loctite to secure them into the holes in their frames.  The ball races have a rim to one side to help their location and I always put this rim to the outside of the frame because the ball races have to absorb any end thrust.  

 

Draw Bar Mounting:  The majority of my models are permanently coupled but I have one model where it was easier to retain a draw bar pin which allows the tender to be quickly coupled/decoupled from the loco.  Either system works because the benefit of using a neoprene tube for the UJ in the tender is that this prevents the centre portion of the drive shaft (between the UJ's) from dropping to the floor when the tender and loco are separated. 

 

Wheel Diameters:  So far the biggest driving wheel diameter I have managed to model but still keep the drive under the fall plate was 5' 8" and this was the Great Western Mogul.  It all depends on how high the fall plate is located in relation to the diameter of the driving wheels.  So far I have been unable to come up with a gearbox design for loco's with larger diameter wheels which still allows the drive shaft to pass below the level of the footplate/fall plate.  As the loco's I'm building for Clayton will all have wheel diameters of 5' 2" or less I have not put any significant effort into designing a solution for models with larger diameter wheels.

 

Regards,

 

Frank

 

 

 

[Buhar]

Thank you very much for the reply, Frank.  I don't know where I got 2mm for the shaft from.

 

That is all crystal clear now, I'm glad I asked, the only issue being fitting ball races to the original style of gearbox.  I see Chris has the Tender Riser back in stock, but that doesn't help with the other end.  I suppose replacement plates could be sweated onto the ends maybe using the leg of a chassis jig for alignment.

 

There are 6mm O/D spurs available that look (on Sketchup) to be pretty well concealed behind wheels, ashpan and brake gear and allow the drive to be transferred upwards after passing under the rear driving axle on a 6'6" driver, but I think any playing with that idea that is well down the line.

 

Thanks again

 

Alan

[Chuffer Davies]

More progress on the Pendon ROD to install the brake gear and the underhung leaf springs.  I must admit that it has been a bit of a fight this time. 

 

 

I hinted at an issue with the positioning of the leading brake hangers in my previous post.  On the prototype loco the hangers fit in the gap between the frames and the cylinder end plates, but in the model there is insufficient space.  I looked at how Bachmann had resolved it with their OO model, but their frames are so much narrower than those of the prototype, there is sufficient space. It's just in EM and P4 that the problem occurs.   I have had no choice but to remove sufficient material from the cylinder end plates to provide space for the brakes.  It was not the easiest task to perform but as its hidden behind the slide bars it will be impossible to see the damage when the build is finished. 

 

 

 

It also became apparent that the rear brake pull rod could not be correctly mounted centrally between the frames because it would interfere with the pinion gear of the modified gear box.  Instead I have had to position it off centre to avoid the gear.  It is only when looking at the underneath of the loco that the modification is apparent, side on you wouldn't know.

 

 

Despite these set backs I am still pleased with progress and can now start adding the fine detail such as the drain cocks and sand pipes.  The task I have continued to put off is building the valve gear between the frames.  I have designed it with the potential of having working eccentrics but I am still not sure whether it is worth the effort given the typical viewing distance of model locomotives on the Vale scene.   

 

It remains my long term aim to redesign this chassis as an EM/P4 replacement chassis kit to go under the Bachmann model.  All these learnings will be retrofitted to my original artwork.  I don't want future builders to hit the same problems that have tripped me up during my build of this chassis.

 

Regards,

 

Frank

 

 

[Chuffer Davies]

Meanwhile four months later!

 

 

The build of the ROD chassis for Pendon is now complete and it is ready for final testing prior to it being dismantled one last time for cleaning and painting. The completion of the build has been problematic and has taken me far longer than I expected.  Despite numerous attempts to adjust the quartering I just couldn’t get the chassis to run smoothly.  Individually the wheels rotated freely in their horn blocks but as soon as the rods were fitted the chassis appeared to stiffen up despite there being no obvious tight spot to indicate a quartering issue.   After a while I got so annoyed with both it and my inability to sort it, that to get some respite I set the chassis aside and started another project.  This is very unlike me because normally I try to work on one project at a time.  This new project has been equally frustrating for a completely different set of reasons, but that is a story for a future time.

 

Returning to the ROD a few days ago I started thinking about sourcing a replacement etch and starting again, but over the weekend I had one last attempt at getting the chassis to work and finally its running sweetly.

 

I previously mentioned that I planned to include a representation of the inside valve gear.  I already had a set of Martin Finney eccentrics in my spares box and had designed the etches with the intention of attempting to make the valve gear work.  The build has turned out okay and the chassis now has working valve gear.  I decided to mount the eccentrics on a thin walled 1/8” inside diameter brass tube connected to the axle by a grub screw.  In the event there is a problem with the valve gear in the future, removal of the grub screw will permit the chassis to be run with the valve gear remaining static.

 

 

Of course, despite all the effort, in reality the valve gear can only be seen under a strong light and when viewed from a particular angle.  Visitors to Pendon will be hard placed to even see that there is any valve gear between the frames, let alone whether it is moving or not, but that is not the point when it comes to Pendon modelling.

 

So far the ROD has been tested at home and I have also carried out an initial haulage test on the gradient of the club’s Clayton layout.  The ROD successfully hauled 40 mixed goods wagons up the 1:50 gradient on a 4’ 6” radius.  Critically this loco has to be capable of hauling the long mineral train on the Vale Scene at Pendon which I believe is around 90 wagons and so, before I once again dismantle the chassis for painting, it is my intention to visit Pendon and try it out.  I’ll let you know how I get on.  

 

 

 

Thanks for reading,

 

Frank

[cctransuk]

On 26/07/2023 at 15:27, Chuffer Davies said:

 

 

... over the weekend I had one last attempt at getting the chassis to work and finally its running sweetly.

 

It would be interesting to learn what you discovered to be the source of the 'stiffness'.

 

CJI.

Edited July 27, 2023 by cctransuk

[Chuffer Davies]

On 26/07/2023 at 16:14, cctransuk said:

 

It would be interesting to learn what you discovered to be the source of the 'stiffness'.

 

CJI.

Now that is an interesting question!

If I'm being totally honest I don't precisely know what the solution was.  As I have already documented, the symptom I was experiencing was that, although the wheels appeared to rotate freely in their individual horn blocks, once I added the coupling rods the chassis stiffened up significantly and the wheels would no longer revolve if I pushed the chassis along the track.  The stiffness was not as you would typically expect.  There was no one tight spot to suggest that the crank pin holes needed opening out or the quartering adjusting.  The one thing that I was certain of was that the spare set of coupling rods I'd built were now worse than the original set, so  I dismantled the chassis one more time and.......

 

Firstly, instead of the 1/8th inch reamer I'd been using, I replaced it with a 1/8th inch drill bit in my mini drill and gave the horn blocks yet another seeing too. 

Secondly I checked the fit of the connecting rods in the crossheads and made sure they were a nice floppy fit.

Thirdly I filed the crossheads to make them a looser fit in their slide bars.

 

I then reassembled the chassis with the original coupling rods, re-quartering the wheels by eye (as I always do), et voila it was suddenly working.  Was it one specific thing I did, I don't know, but in combination the problem was at last eradicated.

 

I normally try to keep everything as close a fit as possible when building my chassis, but in this case by loosening everything up slightly it has resolved the problem I was having.

 

Frank    

 

[gr.king]

"I'm not sure what I did, but it works now" is always a little frustrating, but at least it does work properly now.  Close tolerances everywhere are very nice if you can get away with them, but if not, I'm always happy to remember that a certain Russian (and Chinese) made rifle with "slack fit" parts was much more reliable than many others of its time, and even if not terribly accurate was on the winning side in numerous conflicts.

[Chuffer Davies]

Building a locomotive chassis to a specific brief is different to building one for yourself.  The 'Brief' was to build a chassis that was capable of hauling the long mineral train on Pendon's Vale Scene.  Whilst this train is normally hauled by Guy William's famous 28xx, currently Pendon has no suitable substitute loco if the 28xx needs servicing. I had tested the ROD as far as I could on both my test track at home and on the club's Clayton layout but eventually it needed to be tested on the train for which it is being built.  On Tuesday morning I set off to drive the 190 miles to Pendon Museum. Fortunately the weather was kind to me, the sun was shining, the traffic on the M1 was for once moving freely, and I was able to enjoy the four hour drive to Pendon's car park in the beautiful Oxfordshire Village of Long Wittenham. 

 

After a private tour of the museum, including a look around the back of the layouts to see those areas that the public don't normally get to see, Tony Sheffield (the Pendon locomotive CME) invited me into the fiddleyard of the Vale Scene to give the ROD its long awaited test run.  I was first given a demonstration of the 28xx hauling its famous train.  You need good sight to see the back of the train sitting in the fiddle yard.  The train is well over 20 feet long and its back stands under the scenery of Pendon Parva village.  The power was applied and after a slight slip of the driving wheels the 28xx dug in and started its train.  The 3 link couplings remain taught when the train comes to rest in the fiddleyard and so the 28xx doesn't have the luxury of picking up the train one wagon at a time, it starts the whole train at once. 

 

After this amazing performance by a locomotive that is now over 50 years old, Tony removed the 28xx from its train and invited me to place the ROD in its place.  The controller was turned and ------ the ROD polished the track.  Tony gave the train a slight helping hand and after a couple of feet the ROD dug in and away it went.  It then hauled the train all the way around the Vale back to the fiddle yard only slipping momentarily as it went up the short gradient at the entrance to the fiddle yard.  Tony explained that the fiddleyard has another slight gradient at its exit, just where the locomotive stands, and this is why the ROD couldn't get the train started.   He then went to his work bench and returned with some offcuts of lead flashing.  These were incrementally placed on the boiler of the ROD until there was sufficient additional weight to enable the ROD to start the train. 

 

This is how much additional lead is needed to allow the ROD to meet the Brief:

 

  

I now have to find a way of hiding this lead in various crevices of the chassis and/or Guy's loco body.  Once installed I will then return to Pendon to try once more.   So close but no cigar! (yet).

 

 

Many thanks to the Pendon team for their hospitality and for their kind words of encouragement.  Better luck next time, hopefully.

 

Regards,

Frank