Building a 31/2" Gauge Locomotive Engine

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Bernd:
Can believe it was done without 3D cad? :offtopic: :lol:

Bernd

sbwhart:
A book writen by LBSC :bow: published in the 1930’is on the building of a 3 1/2 inch gauge model of a contractors shunting Engine TICH, (I bought my copy from ebay) a model that has introduced many people to the hobby. In it old Curley describes one method of cutting the steam ports in a cylinder, I quote from the book:-

“ To cut the ports by hand, drill a row of holes down each marked out steam port with a 5/64 in drill, and 7/64 in, for the exhaust port. Then make a couple of weeny (small) chisels, one from ¼ silver-steel, and one from 3/32 in. Just file to shape, harden and temper, and give each a rub on an oilstone. With these, a light hammer, a bit of ‘’common savvy” and a bench vice, you will find it easy enough to chip each row of holes into a rectangular port.”

It just goes to show you don’t need high tech solutions to a problem,

Just Common Savvy.

I guess out of necesity or Great Grandfathers had lots of it.

:D

back on topic for the next posting

Stew :wave:

sbwhart:
Steam Chest Cover

The steam chest cover was supplied as a phosphor bronze casting with an integral chucking piece so that it could be machined in the lathe. With my casting I found that when the skin was machined off it had deep blow holes right on the edge where clamp holes would be drilled, it was scrap !!!!. I don’t find Reeves casting very good quality particularly when you consider what they charge.

Option 1:- Send it back to Reeves and get a replacement, this would cost me the postage.

Option 2:- Get a piece of 1/8 brass plate and make the cover from this. Take the casting to the next Midlands Model Engineering Exhibition where Mr Reeves will have a stand, and have a bit of an eye ball to eye ball with him. :wack:

I settled for option 2

As it turned out this was faar easyer than machining up the casting all that was required was to square it up drill and tap the hole in the midle for the exhoust pipe, stick it on the steam chest with two way type (thanks Ralph) and drill the clamping holes:- Job Done :thumbup:

Pistons

The pistons are manufactured from S303 free machining grade Stainless Steel bar. The bar was set up in the three jaw chuck and for both pistons the diameter roughed out to within 1mm of finished size. The packing grooves were finished turned and the 7/32*40 drilled and tapped, and both pistons parted off.

The piston rods are manufactured from 7/32 Diameter S303 Stainless Steel. It was set up in a three jaw and threaded 7/32*40 with a die, and the rods parted of to length. The rods were screwed tightly on the pistons with high strength loctite and the end of the thread slightly peaned over to securely fix the piston. The pistons needs to be finished off to size on the rods with the rod running dead true, this can be done in a four jaw with the rod clocked up true, or in a collet not having a 7/32 collet a brass split bush was turned up so that the rod could be held in a 3/8 collet. The piston was carefully turned up to be a nice sliding fit in the cylinder, and the pistons marked up with a letter stamps L and R.

Divided he ad:
Nice looking pistons and plate there Stew :thumbup:

The use of double sided tape was passed to me by John (Bog's) Who no doubt learned of ot through other channels... anyway you look at it the more of us nkow about it the more will benefit :)

Not too sure about this action :wack: with that plate Stew.... You may find yourself detained at HM's pleasure!! :lol:

I like this build Stew, never really watched a loco being born before! (seen lots of part way through shots.... but never a blow by blow :thumbup: )

Looking forward to seeing it come together,

Ralph.

sbwhart:
:offtopic:

I had a few domestic duties this morning:- changing the straw and emptying the cesspit, and assembling some Scandinavian flat pack furniture, my wife has the sense to keep away when I’m doing this sort of job. I’ve a theory that flat pack furniture was invented by a Swedish Divorce lawyer trying to drum up business, after its introduction I bet divorce/matrimonial homicide and suicide rates went up.

:lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol:

Any way back on topic

Slide Valve

The slide Valve is made from a Phosphor Bronze Casting both valves coming from the same casting. After cleaning up the flash and checking it over with a ruler, it was apparent that there was barely enough material for some features to clean up, and some features will not cleaning up at all. The features that won’t clean up are none critical and won’t affect function, I’ll have to take care with the others.

First job was to set up my machine vice, the fixed jaw was clocked up square and with the casting sitting on a parallel, the surface skimmed up using a fly cutter, it was removed from the vice, the bur was cleaned off, and the other face cleaned up, it just met size. :thumbup:

Again the burs were cleaned up and the casting set up in the vice to skim up the edge, but this time it was set level with the top of the jaw using a parallel to site it up, this is a andy alternative when dealing with uneven casting you can even set to a line.

My vice was made by a friend who I worked with when I was tool-making, and all faces are dead square and parallel. For the other side it was set on a parallel far enough forward to allow it to be mic’d for size.

Tip:- Brush for cleaning away swarf safely: keeping things bur free, keeping swarf away, and tapping the component down onto the parallel is critical to getting things parallel and square.

The fly cutter is home made, one of the first things I made when I got my machine, it’s tailored to use discarded TC end mills that I’ve got a good supply of.

This is where clocking up the vice comes into play. Casting was set up on a parallel with an end protruding from the edge of the vice, with a big end mill the end was cleaned up, it was turned round and the other end treated the same.

With two flat faces and two edges square and two ends square, the next job was to mark out the features, it was clear that the oblong pocket for one of the valves would end up to wide, and that the slots across the top would be too deep, I don’t think this will be detrimental, but its just another example of poor castings. When you look at this component it could quite easily be made from a solid chuck of material, and far cheaper.

To machine the slots a ¼ and a 1/8 slot drill was used. The machine was set up to pick up the centre of the casting, this was done by finding the edge of the vice jaw using a fag (cigarette) paper with a 6mm dia set piece advanced until it just grabbed the paper against a parallel, remove the parallel and advance the table ½ the total of the 6mm plus the casting width.

The casting was set back up on a parallel and the ¼ slot drill taken all the way along the casting to the required depth. The cross slots are clearance on the slide valve rods are not so critical they were milled to width up-to the marked lines with the 1/8 end mill.

The casting was turned over for milling the pocket, the critical feature is the width facing the direction of travel of the valve this only has to be correct for a small depth say 1mm, so there is no harm to have the pocket stepped, I know this is the practice on full size engines. The pocket was carefully milled out, checking the critical feature by mic.

Tip for tricky milling like this, always feed into the cutter, and always lock the table, and put a mark on your dials when you reach the end of the cut.

Remove from the vice cut the casting in halve to give the two valves, and set each one up on parallels and mill to thickness.

This gave me valves that are dead square and parallel, the surface of the slide valve needs to have a very good finish and to be dead flat on the valve ports to make a steam tight seal, I'll tell you how to do this with my next posting.

Sorry if I’ve been a bit long winded on this part but quite a few of you have asked questions about, making bits like this, so I hope this will help.

:beer:

Cheers

Stew

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