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Kerr Stuart KS4421 in EM Gauge


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Hi everyone - I'm hoping to build a model of this very old Diesel shunter in due course. I built a plasticard body as a teenager about 35 years ago but never progressed to a chassis. At the time I used the Roy Link drawings in Railway Modeller about 1979 but they were not dimensioned. I now have scaled drawings from a book owned by a friend, so I've finally decided to give it a go and build a new one that actually works.

 

However, one part I'm struggling to find information on is the driving chains. They are clearly visible behind the wheels in one photo of the right side, linking front and middle axles, but I can't locate a clear picture of the left side to see if it is the same or not. I wonder if anyone who knows the loco better than me, perhaps through visiting it at the Foxfield Railway, knows the answer to this, or has a photo showing the left side of the underframe? I think that visually it is important to include a representation of these, although it will only be cosmetic of course - I don't think Delrin chain goes that small!

 

Any advice greatly appreciated.

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the chain arrangement is Left hand of gear box to front axle then right hand front to middle axle and left middle to rear axle. its a loco i would like to model one day and was also disappointed at the unusable drawing in the modeller, but was able to take some measurements a few weeks ago. i took plenty of photos too such as close ups of the frames and in side the cab

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There are some drawings and photos in the recently-published book by the Industrial Railway society on Kerr Stuart ic locos:

 

https://irsshop.co.uk/epages/c06e4627-fbe4-483c-833b-6f5529d3cffe.sf/en_GB/?ObjectPath=/Shops/c06e4627-fbe4-483c-833b-6f5529d3cffe/Products/0138H

 

An excellent publication at a very fine price for the content in terms of both volume and information.

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  • Barclay changed the title to Kerr Stuart KS4421 in EM Gauge

After a couple more years procrastination it's time to try to make a go of this:

 

I've actually been interested in this loco. for some 40 years, since I got hold of an old Railway Modeller from May 1979 which had a description and a scale drawing. As I said in the first post the otherwise excellent drawing by the late Roy Link was unscaled which was quite a problem! Undeterred at the time I guesstimated and built this plasticard body which was intended to perhaps fit onto a Tenshodo 'SPUD' or something, but I never got any further with it...

 

WP_20190209_11_46_22_Pro.jpg.ffa574fe85eb9ec650b4c89b90f6ea6b.jpg

 

Fast forward to a couple of years ago and my friend Chris had obtained an excellent book on the internal combustion locomotives of Kerr Stuart, and, from this, I was finally able to obtain the all-important dimensions, showing that I was very close as a teenager. The loco. is a couple of mmm too wide and the same too long, and the bonnet is slightly too wide. The new brass one will be correct of course and in fact the superstructure appears to be pretty straightforward, but there are a number of issues in the chassis Dept.:

  • All that detail on the outside frames!
  • How to model the chains - static sprockets with a facsimile of the chains, or sprockets that revolve but therefore lack the chains?
  • How to manage suspension in a model that needs to be gear-driven?

I have some thoughts on these problems, but not all of the answers yet. However if I don't make a start nothing's going to happen, that's for sure. The only progress so far is a running plate that I made a year or so back - it is 15 thou brass. I feel that  10 thou would be more to scale, but probably not strong enough so I have used 15 and thinned the edges from underneath:

 

WP_20201101_15_50_50_Pro.jpg.f0b5f2d966f89dcab17c17bd5fb23641.jpg

 

Next time I will discuss my thoughts on transmission and suspension and I will be seeking advice!

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I'm a bit surprised that, given the loco's 'notoriety' and the wide range of obscure prototypes that have been modelled, nobody has produced a kit for this.  I think my first introduction to it would have been the RM article and I've seen it at Foxfield over the years.  I've an idea that I may have harboured thoughts about making it in 4mm but obviously never did!

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3 hours ago, Barclay said:

How to model the chains - static sprockets with a facsimile of the chains, or sprockets that revolve but therefore lack the chains?

Are you modelling it as the actual loco, or as a fictional other of the same type? If it's the latter you could always make some casings to cover the chains and sprockets. It's feasible that such a thing could be done in the name of safety and for keeping muck out of them.

 

If you really do want to model the chains and sprockets then I have no idea how to do that. Not to scale, anyway.

 

3 hours ago, Barclay said:

How to manage suspension in a model that needs to be gear-driven?

I'm not sure what you mean there. Do you mean having the links and radius arms of the prototype scaled down and working? Or just some form of hidden suspension to make the model sprung rather than a rigid or compensated chassis?

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1 hour ago, 5050 said:

I'm a bit surprised that, given the loco's 'notoriety' and the wide range of obscure prototypes that have been modelled, nobody has produced a kit for this.  I think my first introduction to it would have been the RM article and I've seen it at Foxfield over the years.  I've an idea that I may have harboured thoughts about making it in 4mm but obviously never did!

It is surprising we haven't seen a kit (we will now !)

 

1 hour ago, Ruston said:

Are you modelling it as the actual loco, or as a fictional other of the same type? If it's the latter you could always make some casings to cover the chains and sprockets. It's feasible that such a thing could be done in the name of safety and for keeping muck out of them.

 

If you really do want to model the chains and sprockets then I have no idea how to do that. Not to scale, anyway.

 

I'm not sure what you mean there. Do you mean having the links and radius arms of the prototype scaled down and working? Or just some form of hidden suspension to make the model sprung rather than a rigid or compensated chassis?

Just a fictional extra example, so I see your point. The chains would obviously be non-functional but they are visible so a static representation is probably the way to go.

 

I think I have a mental block about wheelsets moving relative to each other when they are driven by spur gears, because this theoretically puts the gears out of perfect mesh. However it must be done and gotten away with elsewhere - Penbits bogies for instance? There won't be room for compensation so I'm contemplating some form of springing at the moment, with very limited travel for the reason stated...

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2 minutes ago, Barclay said:

It is surprising we haven't seen a kit (we will now !)

 

Just a fictional extra example, so I see your point. The chains would obviously be non-functional but they are visible so a static representation is probably the way to go.

 

I think I have a mental block about wheelsets moving relative to each other when they are driven by spur gears, because this theoretically puts the gears out of perfect mesh. However it must be done and gotten away with elsewhere - Penbits bogies for instance? There won't be room for compensation so I'm contemplating some form of springing at the moment, with very limited travel for the reason stated...

The obvious manufacturer, is the excellent Chris from High Level. This loco would be right up his street.:lol:
Chris.

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@Rick_Skateboard on here knows a lot about Kerr Stuart diesel transmissions as he is rebuilding the real KS4415.

The real locos have turnbuckle-type traction rods to the axleboxes to keep the chains taut, and the wheelbase is therefore adjustable (within limits)!

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Just now, Ian Blenk said:

here's one I built in the late 80's, very basic!

ks.jpg

Looks good to me Ian.
I've seen the narrow gauge version being rebuilt at Boston Lodge. The transmission is a 'marvel' of engineering. I bet all those chains were a beggar to keep in tension!
Best Wishes,
Chris.

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2 hours ago, Barclay said:

I think I have a mental block about wheelsets moving relative to each other when they are driven by spur gears, because this theoretically puts the gears out of perfect mesh. However it must be done and gotten away with elsewhere - Penbits bogies for instance? There won't be room for compensation so I'm contemplating some form of springing at the moment, with very limited travel for the reason stated...

What I think I would do is the have the end axles fixed and unsprung, with the centre axle in hornblocks so that it can have some travel up and down to take into account any rough joints or changes of gradient in the trackwork. It doesn't need to be much travel and I'm sure the gears would stay in mesh as long as they are a large enough module.

 

Or two small HL Micromiser gearboxes and 10/15-sized motors powering the outer axles and an unpowered sprung centre axle?

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My Sentinel uses a modified 'under the counter' HL gear train based on Chris's Planet 'chassis' designed for Gordon Ashton and this has a compensated axle with the usual HL spur gears.  No problem with any movement.  If there is so much movement that gears are coming out of mesh I would take a good look at your track!  These are both 0-4-0 locos but I'm sure an 0-6-0 version could be achieved.

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Here's all the bits I accumulated a couple of years ago:

 

DSC_0067.JPG.1df8761c520b5b7f6f9b98204cec31c0.JPG

 

There is a tiny Mashima open frame motor that came with the Backwoods Garratt kit, a High Level Loadhauler, 120:1 to hopefully tame it, and some 0.5 module Delrin spur gears by Accu.co.uk. The intention was for the gearbox to drive the centre axle with spur gear drive via intermediate layshafts to the other two axles. This would take up too much room for my usual compensation, so I have been searching for another option. One idea that springs to mind is Continuous Springy Beams - I have followed their development with interest but little enthusiasm, since I'm perfectly happy with compensation, but I think they may help in this instance. The other option is to just spring the centre axle as Ruston suggests, and I may still go down this route - all I really require is reliable electrical pickup. One thing that is likely to be a problem is fitting the spur gear around or inside the gearbox and it may be necessary to modify the Loadhauler to achieve this.

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The gearbox has been assembled although with nothing fixed in place permanently yet. The motor run in and attached. Finding the space to attach the extra spur gear to this axle caused much head scratching until I realised the obvious solution- cut off the grub screw boss from the HL gearwheel, and reduce the boss of the Delrin spur gear, and it all fits in. All that remains is a tricky session with the Loctite 603, where I endeavour to fix the gears to the axle without fixing the axle to the bearings...

 

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DSC_0067.JPG.512d79f584479f52dbd45434758a62d4.JPG

 

Thoughts on suspension continue and I am coming round to like very much Ruston's suggestion to keep it simple and just spring the centre (driven) axle. I have a couple of 2mm hornblocks which could be fitted to slide directly in the frames. This would also avoid the problem of having to fit up the gearbox within the frames with no way of ever getting it out again.

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A timely update as there has been some work carried out on the protoype as well. In the last couple of weeks the engine has been checked over, a set of batteries temporarily fitted and the engine started at the first attempt. This was done as first steps to bringing the loco back into traffic as there has been a request for it to attend an event at the Middleton Railway, Leeds, in 2022. To this end the fitting of vacuum brake gear is being investigated to see how sympathetically it can be added to the loco.

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The decision was made to make the chassis as simple as possible. Rigid outer axles and a sprung centre one. The chassis frames were assembled from 15 thou brass and 2mm bearings installed for outer axles and layshafts. I don't normally build rigid chassis and am not used to having to build something dead square (sorry) so the 2 halves of the chassis were soldered together with the wheels in so I knew it would sit flat. The centre axles will run in hornblocks that slide directly in the chassis frames. No room for proper hornguides, but in any case, without coupling rods its location is not absolutely critical (sorry again).

 

The use of 2mm bearings, both those in the High Level gearbox and the Branchlines ones I bought for the chassis was interesting, as none of them would even look at the 2mm axles and shafts I had. The fit was more than tight, it didn't exist. I don't have a 2mm reamer, so ended up using the 'power reamer' - a 2mm drill in the minidrill to create enough running clearance (really sorry). I don't know why this should be necessary as when using 1/8" bearings the fit of axles is generally quite good, although I do have a 1/8" reamer to ensure smooth running. Anyway, all smooth now and hopefully no more engineering horrors to follow. As for the springing on the centre hornblocks, I am hoping that a length of brass wire will add sufficient spring and also prevent them revolving. Testing next weekend I hope...

 

DSC_0078.JPG.65b4cabeb7d5aa6e52d8579567ebce68.JPG

 

DSC_0077.JPG.60af9856b651a5a655d8783167db7012.JPG

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On 09/08/2021 at 10:23, avonside1563 said:

A timely update as there has been some work carried out on the protoype as well. In the last couple of weeks the engine has been checked over, a set of batteries temporarily fitted and the engine started at the first attempt. This was done as first steps to bringing the loco back into traffic as there has been a request for it to attend an event at the Middleton Railway, Leeds, in 2022. To this end the fitting of vacuum brake gear is being investigated to see how sympathetically it can be added to the loco.

Looking more closely at the photo's Sir Douglas sent me, there is a huge amount of slack in the driving chains. Can this be taken out by adjustment, or will you have to replace them? 

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23 hours ago, Barclay said:

Looking more closely at the photo's Sir Douglas sent me, there is a huge amount of slack in the driving chains. Can this be taken out by adjustment, or will you have to replace them? 

should be possible to take it out by adjusting the turnbuckle links to the axle boxes....

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Elsewhere on RMWeb last week, I learnt a new phrase - Task Appropriate Profanity. There was a lot of T.A.P. in my loft this weekend.

 

The plan was to sort out the springing and set up the drivetrain. Springing wasn't too bad - I have used lengths of 0.33mm brass wire, which bear against the top of the hornblocks, and they seem to do the job. I know the CSB enthusiasts seem to use steel wire. Is there a reason for this I wonder? Does brass lose its spring over time? At the moment there is enough spring to hold the back wheels off the ground in this shot but a little weight will have it sat down nicely.

 

DSC_0084.JPG.c91f261a908699dcc6fea49db545dc3c.JPG

 

 

On the drivetrain, I needed to lock the High Level and the new Delrin spur gear to the axle as it runs through the gearbox, so carefully introduced some Loctite 603 between them with fine brass wire and wizzed them round to spread it about. This was partially successful, in that the High Level gear locked nice and solid, and the Delrin one didn't. This was the worst possible outcome as it was no longer possible to remove the axle to deal with the loose gearwheel. I tried superglue but the previously applied 603 ensured it didn't stick. It was some while before I accepted the awful truth and sawed off one side of the gearbox below the intermediate shaft. This allowed the axle to be cleaned up and plenty of 603 to be applied before the gear wheel was slid back on. Only when the 603 had gone off was the side of the 'box soldered back on.

 

The gears on the axles were similarly secured but the layshafts posed a problem - it would be nice to be able to remove them reasonably easily as this allows the motor and gearbox to be dropped out. In the end instead of securing the gears I polished up the axles until the gears ran smoothly on them, as they do in the High Level gearbox. The shafts can then secured on the outside with just a speck of epoxy when I am happy with it all. Test running was a disappointment, with a tight spot on every revolution, just as if it had coupling rods. This was eventually traced to a slightly tight mesh on the forward layshaft combined with a small eccentricity of a couple of the gears. I think I can fix this by slightly raising this shaft to loosen the mesh. At this point my back was killing me from being hunched over the bench, and the wife was calling up the loft hatch telling me to stop swearing as she was trying to relax. "So am I" I replied, "this is my hobby"..... More next week.

 

DSC_0079.JPG.b4ede8afe59383c267ae7db24b5f25ae.JPG

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  • 3 weeks later...

Sorry for the delay - I really had done my back in, and the workbench is very far from ergonomic...

 

The photo shows how much I had to raise the forward layshaft to loosen the gear mesh. Annoying as I thought I had measured everything accurately. In the end it was quite a bodge, and then I found that the chassis still wasn't running smoothly. This was eventually traced to the gearbox side being slightly out of alignment, and it was tweaked true with pliers. Yes, I had tested it after soldering it back together, but models can be very bl00dy minded when they want to be.

 

DSC_0097.JPG.fc83c150283da1132ed847fefe268dfc.JPG

 

I have to say I'm not too impressed with the Delrin gears, some of which are not very concentric. I might expect this if they were 50p from ebay but they were a couple of quid each from a British supplier. Still, they work now, and the flywheel gives a very pleasant run-on of a couple of seconds. This is at maximum power of course, and the real one has a top speed of either 8 or 11.27 mph, depending on the gearing on this particular model, so it won't be running on full power very often. The re-positioned layshaft fouled the brass springs for the middle axle so they were replaced with 0.45mm wire secured at one end only. Still, just enough to keep the square bearings from rotating and to hold the back end off the ground, but it doesn't take much weight to set it down.

 

Next will be pickups, top-acting, and extensive testing before starting the cosmetic parts.

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