Su251-53

[parovozParticipant @parovoz]

Hello All,

A few of the team here asked to see a bit more of  the construction of the Su class in 7 ¼” gauge. After a long design and research period Metal cutting started in anger in 2003. First up was the tender as I wanted to have that ‘in the bag’ before I started on the loco. This project is almost entirely built from photographs, I was not able to physically see an actual preserved engine and the only ‘drawing’ I had at the start is the one reproduced her from Le Fleming and Price. I finally acquired a large number of drawings a couple of years ago, when the work was basically complete….. Luckily they confirmed that in most cases I was correct in my assumptions and the bits I got wrong are not noticeable.

 

The tender is on a welded steel backbone frame made from heavy box, the bogies are air braked with low pressure air at 20 psig on diaphragm cylinders, basically vacuum in reverse…. There is also a manual hand brake on the front bogie. Under test, the brakes seem to be reasonably effective.  The body is 2mm brass throughout so that it is solid enough to sit on. It all makes for quite a heavy tender which can just be lifted by 2 people… There are a couple of air receivers under the tender frame for the brakes. There are also a couple of ball valves for the water output from the tender so that it can be uncoupled without draining if required. An interesting feature are the try cocks for the water level, presumably to check it when the surface is frozen over.

 

The hardest part was getting a good photo of the rear deck water fillers. In the end I managed to get a still capture from a TV video ( a great train journeys thing ) that showed just enough to be able to interpolate the position of the fillers. When I finally found a top image a number of years later I had luckily got it pretty well correct, but there was a lot of agonising and rechecking that fuzzy still to get to that stage. Building purely from photographs brings an interesting set of challenges, the cross checking of dimensions from several views takes time, but builds confidence that sizes are correct. Then back tracking to the key sizes on the general arrangement is the final check. It seems to have worked with only a few minor proportion errors that no one will notice.

Suspension is interesting, a combination of leaf and coil. That made life easy as I could harden and temper the leaf springs normally making them #@$ hard, then calculate the required spring rate on the coils…. Easy….

Finally there is a hand air pump located in one of the front cavities to top up the brakes if the steam driven compressor fails. That is a bit of the general paranoia here, there are a few examples of belt and braces redundancy on the loco that with hind sight were probably a bit too far. And at the other side a battery box for the rear lamps.

 

So that’s the tender…..

 

 

[parovozParticipant @parovoz]

And the platework……

The photos are not brilliant, I didn’t have a great digital camera at that time. Also the only purchase parts are the wheel castings. They are Highlander front bogie wheels.

 

 

 

 

 

 

 

[noel shelleyParticipant @noelshelley55608]

That is some mighty fine work ! Noel.

[noel shelley]

On noel shelley Said:

That is some mighty fine work ! Noel.

I’ll second that motion,  it would be great to see it at the MMEE in October, a good candidate for competition winner.

Andy.

[WearyParticipant @weary]

Thanks for posting the additional pictures showing your tender construction.  Really lovely work on a most impressive locomotive.   I was also interested to read of your ‘trials and tribulations’ caused by a shortage of primary information and how you overcame those, so thanks for posting that information too.  Your perseverance has certainly paid-off.

Phil

[parovozParticipant @parovoz]

So here is the Locomotive up to rolling chassis level….

 

Frames are 3/16 thick with 1/8” reinforcement plates in the area of the main horns. As per prototype there is a fair gap between the frame and the back to back of the driving wheels. The frame is fairly light and perforated compared to British practice, but with the plate stays and machined stays it forms a very rigid box structure. For a 2-6-2 it is LONG and actually I believe it’s as long as a Duchess! It’s just very spaced out between the front and rear truck.

 

All axles are on roller bearings ( tender too ) and the main axle boxes are steel running in cast iron horns. Driving axles are leaf and coil spring and are compensated. The compensation levers pivot on the inner pins of the brake hangers for convenience….  On the main driving axle are the eccentrics for a pair of axle pumps. That’s my paranoia kicking in again. I thought that it was safe to have a pair of large pumps so that the water level would hopefully pretty much maintain it’s self on our long track with not too much intervention. With hindsight I think that was a step too far? But it’s done anyway. Time will tell if it was worth the effort. I was intending this to be a ‘ near scale ‘ model but also be reasonably practical to operate.

 

Cylinder blocks are just two large square lumps machined from solid cast iron poured at the local foundry. The part I paid particular attention was to the porting and the valve liners etc. to get a large and even cross section area through the full inlet side of the steam circuit and a free flow on the exhaust side. More on that later….

 

 

 

 

 

 

 

[parovozParticipant @parovoz]

And the rest of the rolling chassis….

 

 

[parovozParticipant @parovoz]

Hello All,

On a thread on the “Decline of Model Engineers Workshop” there were comments on a lack of model engineering here. Allow me to redress the balance a wee bit…… here are some more photos of the build of Su251-53 covering the build of the locomotive chassis….

 

 

 

 

 

 

[DiogenesParticipant @diogenes]

Well I’m always pleased to see home-carved metal from whatever branch of the discipline it happens to be from..

..very nice indeed.

Your inside of your shed is much pleasanter than the inside of my house.😊

[parovozParticipant @parovoz]

Last photos of the chassis build and strip down prior to paint and final assembly…

 

 

 

[WearyParticipant @weary]

Absolutely stunning. Just so much detail to absorb. Thanks for posting.

Phil

[DalboyParticipant @dalboy]

I thought I had a lot to do on the Rob Roy when I get back on it. Looking good, hope mine looks half as impressive as yours

[Another JohnSParticipant @anotherjohns]

Absolutely beautiful! Sitting here with a coffee admiring the workmanship on both the locomotive, and on the composition and framing of the photos – what a nice start to my day!

JohnS, Canada.

[Nigel Graham 2Participant @nigelgraham2]

Magnificent work!

[duncan webster 1Participant @duncanwebster1]

I’d love to see that at MMEX, but we don’t know where Parzvoz is located. If he’s in foreign climes it could be difficult.

[parovozParticipant @parovoz]

I had contemplated MMEX. It’s a 300 mile trip from here, central Scotland. Plus there are certainly some logistics to deal with in terms of transportation of the loco, like a trailer and fittings and some additional handling equipment here to get from the workroom to the trailer….

[duncan webster 1Participant @duncanwebster1]

When Modelengineer ran a major exhibition they used to have a van go round the country and collect exhibits, and bring them home after. For anyone travelling any distance its a big commitment to go to the exhibition twice, once to deliver and then to collect.

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