"Everlasting" blowdown valve

Designed by LBSC, and described in his book "Shop Shed and Road", I've made two Everlasting blowdown valves for blowing down the boiler.

A normal needle valve could be sufficient, but because I have to mount them on the back of the boiler, it would be difficult to operate the valve. This design of an 'Everlasting' blow down valve overcomes this problem; it is operated by a lever. Everlasting does not say anything about the valve's lifespan (although it should be trouble-free for a long time according to LBSC); it is the name of an American company who makes (and still do) these valves, and on which LBSC's design was based.

I've made a slightly scaled up design, suitable for the 7¼" gauge loco. The actual valve opening is 4 mm in diameter. The main halves of the valve body are turned from bronze rod.

On the in-let part a M10 x 1 mm thread was cut out of center, with the aid of the 4 jaw chuck. 

On the out-let part all the holes were bored and a thread was cut (M7 x 1) for the connection the blow down pipe. By doing this in one set-up, all the positions and orientations are according the drawing. I wonder how LBSC made this, without all the dimensions on his drawing and without the comfort of   a digital read out on his milling machine. 

On the CNC milling machine the outside contour was cut to size.

The difference between the cut and un-cut parts. That is the nice thing is about CNC milling that you  can just watch how the part is made. 

The milling program first cuts the contour in a spiral movement and finishes it, with a light cut of 0.5 mm down to the final dimension. This gives a smooth surface.

The parts were screwed on a temporary fixture with some M3 bolts

The in- and out-let halves of the valve body completed.

The valve arm, cut from solid brass and later parted off from this block with a saw cutting blade in the milling machine.

With a home made punch, the square hole was opened up. A small spindle will operate this valve arm. 

The valve arm in position in the out-let halve of the valve body. Only a turn of about 30 degrees will quickly fully open the valve. Judging by what I've read in locomotive operating manuals, this valve enables the fireman to briefly blow down the loco boiler during the run or while waiting on a siding. This way the boiler could be cleared of scale and sediment which settles on the foundation ring, without having to blow down entirely. 

The square ends milled on the spindle with a small dividing head.

The spindle, just before parting off  from the stainless steel rod.

The spindle, valve arm and a Teflon valve seat. In the original description by LBSC, he used bronze or stainless steel for the valve seat. But in those days Teflon was not available. 

A quick set-up for CNC milling the operating lever. 

The two completed valves, the left one in opened position and the right one closed. 

The final assembly with a small packing ring on the spindle and the remaining screws has to be still taken care off.  

Completed with a small handle.

The position of the valves, just beneath the footplate. 

Cylinder cladding

The cast iron cylinders have a  metal sheet cladding. No real technical function on the model, just for the  appearance.

The main cladding plates, after a test part was made to get the final dimensions.

The main plate was made of 0.75mm mild steel. It was rolled in bending rolls and the top radius was bended over a 16 mm steel rod on the sheet bender. 

A quick test if the plate would fit on the cylinder, held in position with some small magnets

The front an back plate are hand cut and filed from 1,5 mm mild steel, and hold here in position for marking holes.

Two M3 holes were made in the cylinder casting, and with small pointed Allan screws the plates the marking for the holes in plates was done. A small tap with the hamer on the plate was sufficient to copy the location of the position on to plates.

A view of the cladded cylinder

The front and back cladding plates, with  the holes of the glands made. This was a job of measuring it of the actual job.

Some brass angle profile was fixed with M2 screws

Only the screws on the front an back plates have to be unscrewed to remove the main cladding plate, so the oil check valve can be reached for maintenance if needed. 

The rear of the cylinder.

A CNC milled brass cover of the valve spindle. 

The two cylinders completed

While the cylinder was dismantled anyway,  I've made some oil groves in the cross-head, so it will be well lubricated.

This was done with the boring head and a small cutter, made of HSS. 

Oil check valve

The mechanical lubricator supplies oil to the cylinders. Two check valves (or none return valves)  are used, so that the steam from the steam chest is not escaping through the pump, and thus disturbing a constant oil feed to the steam engines.

With my other locos these valves are made as check valves with stainless steel balls, acting as valve. This design was used by LBSC and Martin Evans in most of their locomotive designs.
Although this works fine, it is not the best solution under all circumstances. Once in a while a piece of dirt or grid will enter the oil feed system and the valve will not close properly. When this occurs, within a few minutes steam will be 'boiling' in the oil container and a mixture of oil and condensed water will start to emerge from the lubricator. Due to lack of lubrication the locomotive will come to a halt very soon.  Cleaning out the pump, pipes and valves takes some time. After refilling and pumping fresh oil through the system, the problem is not always cured. Than the disassembling of the valves is needed.

 Maintenance on the oil check valve of my 5" gauge loco, in the running shed of  Leek  in 2015 

I talked about this occurring problem with several model engineers. There are several solutions nowadays for this problem, using modern materials that are now available.

This was a solution I've tried in 2004 on my 5" gauge 'Didcot'. The inner part of the valve is shown in the picture. It works like an old type bicycle valve. A silicone tube is used as the valve; oil pressure will lift the tube from the holes and steam pressure should close it. I found that it wasn't a success and couldn't dependent on. If the cause was the material of the silicone tube or the overall dimensions of the valve I do not know. It was later replaced for a normal ball valve, which is more reliable but not a 100% 'fail save' solution. 

A German model engineer (Ralph-Peter), whom I've met at an international steam meeting in Leek,  explained me his methode to overcome the problem. He drew up a sketch of his valve, which he used with succes on his own locomotives. This check valve does not contain a stainless steel ball, but a small spring loaded valve that has a rubber seat. He even found that during an inspection of his valves after some time in operation, that small pieces of grid were embedded in the rubber seat, without disturbing the proper working (sealing) of the valve. A longer trouble free operation of this type of valve is thus expected.

I've made a drawing of his sketch in Solidworks, suitable to my locomotive

The spring loaded valve body contains a small piece of rubber, which is pressed against a small embossed part of the valve seat. 

The main body is 10 mm in diameter and 18 mm long. The valve seat and end cap are screwed in with Mf 8 mm thread.

For turning the embossed part on the valve seat a special tool was ground with the aid of small diamond cutting blade in a high speed Proxxon grinder. 

This tool cuts the valve seat in one operation.

The main body of the valve is positioned on the top of the steam chest; a small feed pipe will deliver the oil droplets straight into the live steam pipe. 

It looks a bit big; but it will be inside the steam engine cover afterwards and out of sight all together. 

A small piece of round 5 mm Viton-rubber was inserted (press fit) in the valve and cut  al little bit over size with a knife. Afterwards the rubber was grindend  square (flat) on the lathe to the correct length with the Proxxon grinder. Because the rubber is sitting on the valve seat, a smooth and flat surface is needed.

 The components of the valve: on the left the end cap with stainless steel spring, in the middle the valve with the small rubber insert (on the photo black, but later replaced by Viton which I could get from a friend), and on the right the valve seat with the small bulge that functions as the valve seat. The body has a small extension pipe, so that the oil is fed directly in the main live steam pipe.

Viton was used for the valve seat.

Because the type of my "Viton" O-ring was not exactly known, a test was done by putting the valve in cooking water for some time.

Afterwards I could see that the seat withstand the heat without much problems. The spring loaded closing force was perhaps a bit high.

The valve spring was cut to length, so that closing force was about 200 grams;  firmly closed, but not over stressing the rubber valve seat.  The valve is easy to be opened by the oil pressure from the lubricator.

I hope this type of valve will solve the problem of leaky valves; I'll keep you posted!

This week I've also made an in-line version of this valve for my 5" gauge locomotive, so I can test it very soon in running conditions when the loco is in steam.

(By now, June 2016, I can tell you that it works just fine on my 5" loco)

It is in principle the same valve, but the end cover is now drilled with a 2 mm drill and a union and nut is made.

The valve has three small groves, so the oil has an unobstructed way passing the valve.

Reconnecting the oil pipe.  (It was disconnected, so the oil could be blown out with compressed air, before silver soldering the ferrule to the pipe)

The valve in-line in the main oil feed pipe.

Guard irons and drain-cock operating rods

The locomotive is completely dismantled for the drilling the last holes for fixing of the final parts. The guard irons, brake rod bearings and some angle profile for strengthening had to be fixed. 

It takes about two evenings, for only taking the loco apart; and every corner of the workshop is now full with loco parts.

The rear guard iron in position;  bend of 3 mm steel plate

The frame standing on the four guard irons. Being a German loco, everything has to be painted bright red. 

At the rear of the frame an extra 10 x 10 x 2 angle profile was riveted. On the real loco this gives extra strength to the frame; on the model I do not think it is of any real advantage, but making a model it's nice to include these details

For seven and a quarter locomotives ground level driving is the standard in Europe mainland. Although most tracks are level and in good condition, derailments do sometimes occur on this gauge. Because the cylinder drain-cocks are relative low to the top of the rail, damage is likely in case of a derailment, even with the guard irons on the frame.

To prevent this, a sturdy extra detachable guard iron was designed and produced of 30 x 10 mm steel bar. This can be screwed with 4 high strength M4 Allan screws to the frame.

The extra heavy guard iron, on the frame (in transparent mode)

The guard iron attached under the frame.

Extra supports silver soldered to the guard iron, so it can withstand some impact force in case of a derailment. Also for loading and unloading in the car, this guard iron will make sure that the loco is not damaged..... but if the car will like this?    :-(

  For operation of the drain-cocks a set of levers are made of mild steel.

Operating is now possible from the top of the frame, to the underside of the cylinder. The last few levers will be made coming weeks.

After that I can start to paint and build up the frame. (and there are many parts)