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Baby Hunslet Project

What is a baby Hunslet? The Hunslet locomotive company of Leeds, England produced many narrow gauge engines for the slate quarries and mines of North Wales. There were a number of variants as the engines were tailored for the planned function and the design was continuously evolving. Collectively these small locomotives have become known as Baby Hunslets and many of them have survived into preservation.

The picture is Annette and I on James Evans's beautifully restored Velinheli at Launceston.

The variants are too complicated to cover here. For the definitive history I would heartily recommend the excellent book QUARRY HUNSLETS OF NORTH WALES by Cliff Thomas ISBN 0853615756 but even this book admits that we may never know the full story. Why the confusion? Well, the locomotives werenít identified by having the works number stamped in the frames. When the works at the quarries were overhauling engines and they had a good chassis, a good boiler and a good saddle tank then these would become the first engine completed and as the nameplate is fastened to the tank the assemblage would often assume the identity of the tank. The book details a long an complex trail of components moving about. The main variants were

Frame Shape The early engines for the quarries had their frames cut away at the front and back. This was to allow them to be hauled up and down the inclines within the quarry to get them to their working levels. Initial engines of this type had an ornate profile whilst later engines had a simple cut away.

Engines intended for the Port or the Main lines had straight frames with no cut away. This caused problems later when these engines were transferred to the quarries as the deep buffer beams grounded on the inclines.

Cab

 

Simplistically, Port & Main line engines had cabs, quarry engines did not. Naturally there were exceptions brought about by transfers and so on. Many of the quarry levels had very low clearances precluding a cab and despite the bleak weather conditions the drivers reckoned a cab hindered their work as they were forever getting on and off the loco.

In preservation a number of the cab less engines have gained cab

Boiler

 

The original boilers were domeless, later there were boilers with domes. To add to confusion there were engines which wore their brass dome cover when there was no dome within.

This is by no means an exhaustive list of the differences. Read the book mentioned above for more detail.

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The Model Project [the picture is an Agenoria kit]

After years of their being no kit available for the baby Hunslet there are now three. Typical ,just like buses, none for ages then three all at once. Which of the three manufacturers you choose depends to some extent on your preferences on materials and techniques. The three are: -

Wrightlines This kit has a brass chassis and a whitemetal body. If you like working with WM this could be the one for you. I havenít built one these Hunslets but I have built other kits in the range with great success. The demo model on their stand looks superb.
Mercian This is an etched kit. I have tried to build one and was not impressed with either the fit or the quality of the etching. I never got as far as finishing the model.
Agenoria This is, in my opinion, the best of the kits for the Baby Hunslets. As I write there are three versions available. SL1 is the cab less Alice class kit, SL3 is the cabbed version of the Alice class and SL4 is the Dinorwic Port Class. For imminent release are SL5, the Penrhyn Port Class and SL6 the Penrhyn Quarry class.

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This Project - The Agenoria Hunslet

The standard kit is excellent and many have been successfully built looking good and operating smoothly. The kit was introduced before Romford introduced their extended 1/8" diameter axle extensions. As a result the kit has a working inside frame which can be built for either 14mm [proper 2 foot gauge @ 7mm/foot] or 16.5mm and dummy outside frames.

EDM Models Modifications

The following modifications take the excellent Agenoria kit as a good starting point. Whilst you can build the kit as standard and produce a super model there are some aspects of it which could be improved to improve the running and ease the construction. Before I started this improvement project I had built two of the engines as per the instructions and, were I just building those two, that would have been good enough. However, I have several to build which set me thinking of alterations. The final straw was a request to build two to a narrower gauge than 14mm which ruled the working inside frames out.

The targets for my improvements were: -

Working Outside Frames

With 14mm or 16.5mm gauges this would be personal preference only but to work with narrower gauges it is essential.

Also this is part of a personal hang up. As I help maintain a larger Hunslet [click here to see it] with outside frames I find the inside frame idea alien and believe that a model outside frame engine should have working outside frames.

Larger Motor & Flywheel The standard loco has a Mashima 12/20 motor and 38:1 gears which sit at an angle in the firebox. This combination makes the loco underpowered and too fast. I wanted a higher ratio gear set to get slower running, a larger motor and, if possible, a flywheel to smooth it all out.
Suspension I felt that better running would be helped with some sort of suspension. Two varieties are being tried, three point suspension where the driving axle is fixed and the leading axle pivots and a full sprung version.
Saddle tank & boiler barrel Soldering up the saddle tank is a bit of a finger burning experience. OK if youíre doing one but a real pain if youíre doing a few. Also the desire to fit the larger motor and gearing requires a rethink to the saddle tank to accommodate them
Couplings The standard kit makes little provision for practical couplings supplying a casting for a prototypical coupler. As I favour Kadee coupler and one of my clients has specified them thatís what will be fitted.
Dumb Buffers In the standard kit these fold up from flat etches and are very fiddly and you will burn your fingers with the soldering iron. With a client specifying they be removable and more than twenty to make an alternative had to be found.

This is the ongoing saga of this development. It is a work in progress and the job has to take priority over keeping these pages up to date so they might well lag behind actual progress.

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The Chassis

 

I mocked up an outside frame chassis using the dummy parts and some commercial sprung hornblocks which proved the concept but left something to be desired in terms of finish and rigidity. I started drawing out my ideas in AutoCAD which I use in the day job. Once I had done this and considered the fit to the loco how the gears and motor could fit I realised I was about 80% of the way to having drawings suitable to become artwork for etching. I decided to progress this idea to getting etches done partly to produce these models and partly to gain experience of the process. A spin of drawing the frames in CAD is that the common elements of the three chassis shapes donít have to be redrawn only the differences.

It took a couple of goes to get it right but I now have etches for each of the three chassis profiles to be built up into working outside frame chassis.

The picture to the left shows one of the etches folded up and ready for the suspension to be installed. With the motion bracket added the chassis becomes a strong unit. The holes in the top clear coupling fixing screws and the slots have soldered up coupler mounting brackets slotted and soldered into them

Suspension

The chassis will accommodate two options. The two chassis on test have sprung bearings running in either cast brass or delrin horns. In this design the weight of the engine compresses the springs and the loco rides with the weight carried on the adjusting screws. Should the chassis encounter a dip in the track the spring will push the wheel down into the dip and maintain contact and electrical pick up.

The second option uses the same bearings and hornblocks but the springs on the leading wheelset are removed. Instead a frame stretcher above the axle has a screw fitted which bears on the centre of the axle giving a three point suspension.

Either suspension gives the ability to deal with obstacles far larger than the real thing had to cope with.

There is also a cast brass version of the hornblock. It advantages are that it can be soldered to the frames but its disadvantages are that it takes a lot longer to get to run smoothly because of the distortions in casting and its a bit thicker making it difficult to use in the 16.5mm gauge version.

My preference would be to use the brass version not least because the plastic one can be hard to obtain. I am currently investigating ways of setting the casting on my mill to both thin it down a bit and to clean up the bearing surfaces.

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Wheelsets

The picture shows an early test assembly of a 14mm gauge wheelset

The kit is designed to use Romford wheels and axles. Until very recently that meant you had to have an inside frame as extended axles were only available in the form of 10BA threaded extensions to carry the fly crank. Romford now has a 1/8" diameter extension available but you are still restricted to either 14mm or 16.5mm.

As one of the goals I set myself was to produce a chassis that worked for 1/2" to 16.5mm gauge a different wheel and axle was required. The wheels used are Alan Gibson 3' 0" diameter 4mm scale wheels and 1/8" diameter silver steel axles. With the outside frames the same axle length is used for all gauges with the wheels pressed on to the relevant back to back dimension. The wheels have metal tyres and injection moulded centres. They press on to the axle and slide quite easily if lubricated with a bit of saliva. Over time they appear to grab the axles so a day later they are very hard to move and most unlikely top move unintentionally.

The flycranks are also a moulded product that is a press fit to the axle. A 1mm screw and bush provides the crankpin. As with the wheels these are a press fit which seems to increase its grip with time. Just to be sure a small spot of threadlock on the axle as they are pressed on for the last time guarantees they won't move.

To ensure consistency an quartering the wheels and cranks are pressed on to the axles using jig and spacers. My favourite tool is my GW models wheel press.

Motor & Gearbox

The base model is designed around a small motor and a 38:1 gearbox that sits at an angle in the firebox. To my eyes this has the loco running too fast and underpowered. As I have said before were I building a single loco I would probably stick with this combination but .............

......................................with a few to do I decided this could be improved. High Level Models make an extensive range of gearboxes which can be see at High Level Kits Yet despite a lot of help from Chris Gibbon at High Level we concluded a special was needed. Between us we drew up a new design based on the standard gears and had it etched especially for this project. This gearbox is now available to order from EDM models.

The new design folds up from a single etch and features a 108:1 ratio. As you can see from the test assembly on the left the motor now sits along the saddle tank. The gear tower is entirely within the firebox. It might yet be possible to fit a slightly larger flywheel both in diameter and length bit that will finally be decided by the saddle tank

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Saddle Tank

The original kit has a saddle tank and boiler that is made up from a partially formed wrapper, a partially rolled bottom, half to the boiler, three spacer/formers and a few smaller parts. This is another of those items where if you were building one or two and not changing the drive you would live with this arrangement. The two preformed items tend to be under bent and made of springy brass so are trying to pull apart. The spacers and formers have to be aligned by eye and soldered into place. It gets a bit fraught and usually results in burnt fingers

The new drive going in the saddle tank required something a bit different to be done. I have decided that the way forward is to risk the fingers one doing one superb soldered tank and use this as a pattern for a resin casting. This resin casting can be cored so the tank is hollow and can accommodate the motor and gearbox.

This is where I am at as of June 2002. My friend Phil Traxson of Port Wynnstay models is a resin casting expert and is helping me with this aspect so to some extent the project is at the mercy of Port Wynnstay's delivery schedule.

Well that's the revolutionary progress to date. Some other bits have been made and are being worked on as detailed in the pictures below.  Model making is only a part time business and hobby and comes nowhere near paying the mortgage so the day job has to take priority. Recently I have been away from home quite a bit and as I type this on the 7th July 2002 a regular commute to Copenhagen looks like being a real possibility.

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Anyway, I'll try to keep the pictures updated and here are some of the chassis construction to be going on with.

Getting a square and true chassis

The first of the bearings id assembled and centered in the frame cut-out. Its glued in place with the slow setting Araldite. This gives you time to adjust it and left overnight gives a very strong bond. The key at this stage is to ensure that the bearing is vertical.

in this view it is held in place by a spring bearing against the opposite frame. the trick here is to get it set up right as the last job for the day and then to go to bed so as not to disturb the set up.

Adding the second bearing

Once the first bearing has set the second can be added. Again this is glued with slow setting Araldite and one axle of the alignement tool added. The spring in the middle keeps the hornblock pressed into place. Mine is home made but commercial versions are available. Mine was designed for doing inside frames so a couple of extra bearings space it out to keep the pressure up.

There are two things that you have to ensure at this stage. Firstly the bearing must be vertical and, secondly, the axle needs to be square to the chassis. Once again set it aside for the glue to cure. If your desperate to get on with something the coupling rods canbe cut from the fret and the two layers soldered together.

Adding the second axle.

The next stage is to fit the second axle. The coupling rods are used to space the second set of bearings the correct distance from the frames.

This time the second axle of the jig is passed through the bearings to be fixed with the pressure spring in place. The coupling rods ensure that the axle is both parallel to and the correct distance from the first axle.

Again Araldite is used to fix the horns and care is taken to ensure they are vertical. Set aside until the glue has gone completely off.

Using the brass hornblocks.

One of the problems with the brass hornblocks is the time it takes to get them to run smoothly as a lot of fettling is required to iron out the distortion caused by the casting process.

There is some payback at the assembly stage though in terms of speed. The same process as detailed above is used except that instead of glue a solder paint is spread into the joint. Once everything is lined up a quick wave with the miniature blow torch or resistance soldering unit melts the solder paint and in a matter of minutes its cooled down and you can move on to the next stage.

The only thing you need to be careful with is to resist the temptation to cool is down faster with a wet sponge or something this can both damage the bond and move it out of alignment.

New Motor.

The original arrangement uses a Mashima 1220 motor which is a quite high revving machine. The new arrangement allows the use of the 1224 motor and has room for a couple of flywheels to smooth the drive and give it some momentum.

Cylinder Fabrications

These are the cylinders and slide bars for the first chassis. I gave a lot of thought to having them made as castings as they are a fiddly finger burning exercise to solder up.

They are seen here having had some cleaning up but they have not yet been fitted to the crossheads. This results in the slidebar being a bit thinner when finished. A final polish is done when they are soldered into place.

Body Part Assembly.

Several hours of work are required on each kit pressing the rivets out on the body panels. These are half etched from the back and then pressed through from behind. This can be done using a centre punch or similar but is best done with some sort of riveting tool which ensures they are all done with the same pressure.

I use a GW models rivet press. I have mentioned GW models more than once but I should perhaps say I have no association with them other than being a satisfied customer. I would heartily recommend their products.

More Rivets.

There are lots of Rivets. This view has the cab roof and coal bunkers in it.

Footplates

The footplate and buffer beam unit has a number of rivets that need pressing out before it can be folded to shape and soldered up.

The etched springs in this view are just used as a location guide for more detailed castings.

 

Well that's as far as its got for now. Progress needs the co-operation of the day job, the saddle tank casting to be resolved and then we'll be getting on with it.

Time for an update
Well its been ages since anything got added to this page. I did complete the two engines I was doing for other people and I did take photos of them but somewhere along the way the photos have been mislaid so I cant add them to this page.

Sadly the bit we never got resolved to our satisfaction was the boiler / saddle tank construction and having got the two custom engines done we haven't progressed this. Also influencing the absence of progress has been the withdrawal of the Agenoria kits that form the basis of the construction.

As a tempting morsel I'll mention that I have ideas to reintroduce this but without the dependency on the Agenoria models

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