Mamod / PPS powered loco - build in progress!

alan2525 · 19-02-2008

I thought it was about time I posted some of my stuff! This is a little steam loco I'm working on. I wanted to build a small live steam model and the old Mamod locos were always fun. I wanted to see how I could build my own rolling chassis with outside frames and try to get a loco that was far more scale than the little toy looking mamod loco!

It's based very loosely on a Kerr Stuart Sirdar 0-4-0 Tank Engine.

I've changed the dimensions a little to allow the use of 42mm copper tube as the boiler barrel and fitting of PPS Steam Models osscilating cylinders. I also added some crank weights to add something else to watch in the absence of valve gear!

The second image is a quick render of the 3d model of the loco which I've used to generate the toolpaths for cutting out the brass parts. The boiler in the background was a piece of 1 1/4" copper tube I used to practice my silver soldering on.

**Bunkerbarge** · 20-02-2008

Very nice piece of engineering there Alan. I take it the original wouldn't have oscillating cylinders though, or did it?

Love the rivet detail, will look superb when it gets a coat of paint on it.

alan2525 · 20-02-2008

Nope I've used some (a lot of) artistic license on the greasy bits under the footplate. I didnt fancy machining the cylinders and hackworth valve gear on this build! Depending on how well it works out In my next loco I'll probably machine those myself.

adrian norris · 28-02-2008

How did you do your rivets? What wheels have you used?

alan2525 · 01-04-2008

I used copper rivets from MacModels, to get the exact length I pushed them through a hole drilled in a piece of 4mm aluminium sheet, snipped off the ends and filed to length. I countersunk the holes on the back and then peened the ends over and filed them down flat.

For a raised rivet I use a rivet snap held vertical in a vice and then peen the other end over, finally finishing off with another rivet snap to give a neat appearance. I actually used a blob of bluetack to position the buffer beams on the top of the vice to align everything and keep the bits in place. That way I had two hands free to hold the rivet snap and hammer.

For smaller rivets I was considering buying (or making from a pair of molegrips) one of these tools:

Dave Noble - Tools

I used wheels from IP Engineering for the loco! I was going to turn my own but had some of those spare and they do run nice and true too!

linebacker55 · 03-04-2008

Hi Alan, What gauge is your Mamod project going to run on?...narrow gauge looks like.
Have you a layout already? Your brief biopic say's you model anything worth saving, how diverse are your projects?

...I've considered live-steam in OO gauge, but I'm going to wait for a while yet, and see what other models Hornby produce.

You've a fine start to your Engine, you are obviously a very competent machinist, and I hope it goes as good as it's starting to look...excellent rivet detail....

Best wishes...jules

alan2525 · 03-04-2008

Jules,

The Loco is a 16mm/ft model of a small 2ft gauge Loco it runs on 32mm track. It's based on a Kerr Stuart Sirdar but I've reworked the drawings to allow enough space to fit R/C and gas firing. It's a little longer and a fraction wider too. I'm designing it in CAD as I'm making it too.

In the past I've modelled WW2 subjects and Tamiya 1/20 F1 cars, I've also been interested in Sci-Fi but for some reason the Railway Modelling bug just hit me and thats taking up more of my time.

I've never been a fan of narrow gauge, but my Dad's built a garden railway so I have somewhere to run the loco on! I've always been amazed by model engineering and have never had the confidence to work on a live steam project. I wouldn't call this model engineering as the amount of engineering involved is a minimum using the oscillating cylinders!

It's a learning curve though and now I can happily make things like curved smokebox doors where previously it was a mystery! I've also learned silver soldering and lots of other skills that'll surely be useful in subsequent projects!

linebacker55 · 03-04-2008

There's alot more to soldering than most people realise isn't there?

I've made a few Loco's in 4mm scale and I have to use Low-melt solder and be very careful vis-a-vis Iron temperature. The white metal I work with usually dissolves if you go too far with the heat, and I've been very hesitant to use it in any great strength, so I use mostly superglue Gel... and solder only the brass chassis. I use a thirty watt iron for that, but I've found practising on low melt with even an 18 watt iron is risky at best.

any ideas?...jules

alan2525 · 08-04-2008

Sorry I can't help you there - soldering white metal kits is going to be problematic as the melting point of the part and the solder is such a close range. Do you use one of those soldering iron stations with the temperature control? Those are very good when soldering sensitive electronic components where you have to avoid cooking them!

The main problem with silver soldering is the other extreme - getting enough heat. I use a Bernzomatic propane torch. It works great and the silver solder seems to flow much better than soft solder too.

Here's an update on the progress on my loco!

I've made the combustion chamber for the external gas burner:

alan2525 · 13-04-2008

I made the chimney on my Taig Lathe today. It's only temporarily fitted in the photo below as I still need to machine the saddle part where it fits onto the smokebox.

I should get around to drilling and threading the footplate and buffer beams - in the photos it's still propped up with a piece of brass flat.