Building "Spencer" a Hunslet 4-6-0 Narrow Gauge engine in 3.5" Gauge

I'm building a live steam model of Spencer as detailed in Model Engineer Magazine. The choice of engine was really by chance, I was considering building a traction engine and a set of "Minnie" castings came up on eBay, I eventually bought these and the "Spencer" castings in November 2007. After a bit of investigation it looked like I would have to build the boiler of Minnie fairly early on as it is used to size the axles etc. I didn't want to get into boiler making straightaway so ended up starting on Spencer. Spencer castings are still available from my local Model Engineering Supplier Reeves 2000

I didn't now much about steam locos before I started this project but I'm learning :-) I knew even less about the War Department Locos but there is some good info out there. A particularly helpful site is the WOLS site created by Ian Hughes. There's some more interesting stuff on the War Office Light Rail site

Here's a picture of the full size prototype.

Use these links to jump to the section you are interested in on this page :-

Frames Buffer Beams Axle Boxes Preparing Wheels

Or try one of the other pages on building Spencer :-

Machining the Bogie Wheels

Machining the Driving and Coupled Wheels

Boiler Making

Boiler Making part 2

Boiler Making part 3

Boiler Making part 4

Boiler Making part 5

Boiler Making part 6

Boiler Making part 7



As is traditional I started on the frames, this decision helped by the fact they had been marked out, centre punched and rough cut.


Even with this head start it still took me a over a month of evenings to complete, the amount of effort and concentration is quite demoralizing as ultimately you end up with two bits of steel and a large collection of holes! I would not be surprised if many people give up at this point. It not something I've seen mentioned in any of the Model Engineering mags but speaking to fellow club members this seems to be a common problem. In fact most would avail themselves of the services of a Laser Cutting company for any future builds.


With the frames and horn plates done, the stretchers were tackled next. These were the first components started from scratch, and were completed over a few days.


With the addition of a few 8BA screws I finally had an assembly! The relief and satisfaction at getting to this point was palpable. I was so chuffed I took it to my local club to show off my efforts.

Buffer Beams


With re-newed enthusiasm I then started on the Buffer beams. Here's a picture of the rear beam after first attempt at riveting steel angle to it.


I had a lot of problems getting the rivets to a satisfactory quality and ended up lashing up a jig to hold the work and the rivet dolly together in the vice so I had both hands free to form the countersink.


This is what I've been working on this week, it's the rear buffer beam of Spencer I'm a lot happier with the quality of riveting. In fact I was so pleased I added a second row of cosmetic rivets to make the beams look a bit more authentic.

It's resting on the Drawings of the prototype in 60cm Gauge whereas the model is based on the 100cm Gauge version, I've added the extra inner row of rivets to make it look more like the prototype, unfortunately I don't have any photos of the buffer beams of the 100cm Gauge version so its a guess really

I've been experimenting with a 4" x 6" Belt and Disc sander, using it as a linisher. The 80 grit belt had cleaned the stretchers up a little too well leaving them slightly barrel shaped. I've bought a pack of assorted belts a bargain from "Netto" the smoothest belt is 180 Grit and that seems a lot less harsh. I wanted to tidy up the font buffer beam before riveting it and came up with this rather dodgy method of holding the flat plate with a magnetic DTI stand. No-one died but I'm not recommending it!

With the front beam and shiny I started off with the cosmetic rivets. These are much easier to do before the angle is riveted on.

Annoyingly I don't have a picture of both beams riveted to the angles. This pic was taken after I had separated them. I think they were riveted with the bottom edges nearest to each other


Here's the front beam after cleaning up the angle. Looks pretty chunky!


Had a bit of a break for a couple of weeks to give the Myford some TLC. I wrote up this up on the Myford Maintenance Page

Attaching the front beam was fairly straight forward.The beam was clamped with tool makers clamps and then spotted with the clearance drill size followed by all the way through with 8BA tapping size. Starting off with the the bigger drill has two advantages. You get the tapped hole absolutely central to the hole in the frames and it acts as a counter-bore so the threads don't stand proud of the surface. I found you could just how deep it had gone by the amount of swarf produced You have to be careful as it's easy to drill too deep. My new tapping stand came in handy again, So I'm glad I bought it.

The rear beam was more problematical. The rear beam is lots wider than the front and my drill chuck was fouling the edge before the drill was anywhere near the surface. What I needed was a pin chuck. I didn't have one so ended up making a pin chuck using the collet chuck and collets from my B&D Dremel clone. The thread is .277" x 40 TPI which turned out pretty well considering it was only the second or third thread I have cut on the lathe! This shows the collet I had to make to hold the 8BA tapping size drill (1.8mm)

Finally got to use my thinnest slitting saw too - 15 thou wide - I really must get round to machining the small vice castings I got from College Engineering Supply as this vice is really too big!

Here's a nice shot of the pin vice in use. You can see the lower edge has already been tapped.

An unexpected benefit was that I could use the pin vice in the tapping stand too - which is nice. I've ordered a spare head from eBay so I can keep this all together.

Here's a view of rear beam attached to the frames.

The whole assembly is now very solid and has a bit of weight about it. I'm pretty pleased. I'll need to paint it soon as the odd fleck of surface rust is appearing. I've ordered a cheapo airbrush to try out with my compressor.

The Dremel collet and mini drill chuck came today. The wonders of eBay

Axle Boxes

I now had enough confidence to tackle machining some castings. A major milestone as mistakes start to get expensive. A fellow Spencer builder - John Rothwell - had mentioned he had problems with blow holes and shrinkage on some of the Gun Metal castings so I made time to ponder the method of attack before starting. I modified this when I machined the second stick and I'll describe that improved sequence.


After careful measuring it seems the most critical issue is there is not much extra metal on the edges which slide between the horn plates. Probably the most critical part of the axle box! Both of the sticks had distorted probably due to the Tee shaped cross section. I first cleaned up these critical edges so I could use them as a reference.

The axle box was gripped by the critical edges with the flange part upwards in the machine vice so it looks like a capital "T" as the vice is gripping on unmachined surfaces cereal packet card is used to give a better grip. The top surface was skimmed until machined all over.

The face mill side cutting edges are pretty parallel so the edges of the flange where cleaned up as well to give a reference edge roughly parallel to the critical edges.

Next the casting is inverted an a skim taken off the bottom.

With the casting resting on the flange side face and a taller parallel used to lift it higher in the vice, a good bit of tapping with the soft faced hammer is required to level the casting.

The smallest amount was removed to give a smooth area and then the other side was machined. Small amounts were removed form both sides until the axlebox would just fit into the horn plates.

The depth is okay on these, they fill the horn plates nicely, I just need the flanges machining down to 1/16" to complete the roughing out.

I also still have to cut these into three and drill the axle and spring holes. I'm not sure whether to use "Tich" style spring pockets or underslung springing. The size of wheels may preclude under springing.


Here's the two strips of axle box showing the flanges cut down to 1/16".

Preparing Wheels

The rough idea with wheels is to fettle the castings, paint them and then do the final machining.


Here's the raw castings. The remains of the pouring gate has left a big lug on the side of the wheels. I tried my trusty bastard file on these and didn't make much impression.

Luckily I know the 80 grit belt on my belt sander will remove metal at an astonishing rate. This time I used the belt vertically and rotated the lug against it to get a nice smooth transition.

I then tried out my centre finder to see how circular the tread face was. As it turns out pretty accurate.

The wheels had some surface imperfections and a fair bit of flash around the spokes so out with the Black & Decker Dremel clone with a blue stone bit. I soon cleared the worst off. My approach is to not go too far down the beautification path as I want the casual observer to know these wheels are castings rather than cut from steel blanks. Makes sense to me the castings cost a lot of money! Here's the cleaned up front bogie wheels.

Here's the main drivers and coupled wheels.

A staged shot showing the Dremel Clone, it's the first time I've used it for something other than cutting seized nuts!

The final stage was to give each casting a serious wire-brushing to get rid of any loose scale and rust.

26/3/2008 - Choice of Paint and Equipment

After some discussion with a friend - John Baguley - who is about to paint his completed loco, Helen Longish I decided to follow his lead and use "U-Pol Acid #8" acid etch primer and Halfords own brand High Temp Engine Enamel. Luckily they do this in the two colours I need Satin Black and Gloss Red! The enamel can be thinned with White Spirit for spraying and brush cleaning which keeps things nice and cheap. A quick visit to my local Halfords Superstore had everything to hand.

I've done some spraying before with a cheapo compressor and spray gun so already had to hand a decent quality mask (look for EN 141 on the filters) and a plastic gun for spray cans - not essential but nice to use.

Another nice thing I happen to have is a weather station which gives be some idea of humidity and temp. Low temps and or high humidity are not great conditions for painting. I've avoided low temp being an issue over winter by storing parts and paint indoors.

Another nice thing to have is a small table top oven, I used this for cooking for three years whilst building an extension to the kitchen! I gave it a serious clean before hand and use fresh Aluminium foil. It will allow me to dry the paint quickly and hopefully get a nice hard finish on the enamel.


I've primer-ed the wheels. Initial findings look good. I started off with a very light coat on the first wheel (enough to be wet but not enough for great coverage) and as I went on the paint went on thicker and thicker. More due to impatience than any scientific method! I sprayed 4 leading truck wheels first then the 6 driving/coupled. The first 7 wheels would fit in the oven so got heated to a comfortable temp (under 60 deg cent) I had to give the 4 truck wheels a second coat due to not being fully covered but the following three didn't need it. These are all dry and coating seems tough. I wore vinyl gloves and held each wheel as it was sprayed, gives the best control over coverage.

Final three were left in a box to air dry.

They are still wet after 20mins so have stoved them for about 5 mins probably slightly higher temp too (60 deg plus). I'll see how they turn out. Very thick coating on these was drying on the surface but not below. May be okay as the worse areas will be skimmed. It's pretty hard to get good coverage on the spokes without over doing the front face.

After letting cool down even the thick paint seems to have stoved off quite nicely Have given it one more blast but has thinned out as it's dried. These were all sprayed at lunchtime so I left them til the evening before applying the top coat. The enamel was decanted into a glass jar that came with the cheapo airbrush.

To keep things as clean and dust free as possible the wheels were kept in a plastic box which has compartments just the right size.

The four bogies wheels were stoved at 60 degrees centigrade whilst I was painting the six driver and coupled wheels. Here's all the wheels the next day after one coat had dried.

There was the odd pin hole and thin spot where the paint hadn't fully covered so a second coat was applied and again baked at 60 degrees.

Next page Bogie Wheels!

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