Building a 31/2" Gauge Locomotive Engine

[sbwhart]

Options

1.   Bore out big and make oversize piston to suite.
2.   Bore out big and Sleeve back to size.
3.   Buy a new casting.
4.   Buy a chunk of Phosphor Bronze and machine this up.

A new casting would cost £ 85, a chunk of Phosphor Bronze would cost £ 35, I didn’t like the idea of going over size or sleeving the bore, as there was not much meat left in the wall of the cylinder. I bit the bullet and bought a block of phosphor bronze that had 1/8” machining allowance on it all round, the supplier (College Engineering Supplies) were prepared to cut the block to size with no additional charge. Going this way meant that some of the casting detail would be lost: however, this would be well hidden between the frames so was of no consequence.

Starting from scratch again:- this time squaring up the block was a lot easier, I simply held the block in my big four jaw chuck, got everything nice and square and brought it to size. As I was dealing with a solid chunk of material there was no need to plug the bores for marking out the hole centres.

Tip :- Mark the centre of the block and the bore centres clearly and extend the lines all the way round so you can pick up off these when you marking or machining other features, also scribe the diameter of the bores as a check that your machining is going OK.

The job was set up on a face/angle plate as before but this time clamping was easier because of the more uniform shape. A good big deep centre drill followed by progressively bigger drills, to get the meat out:- a job that was made much easier thanks to the modification to the tail stop suggested by John (Bogs) this stopped the drill spinning on the taper.  Swapping over to the boring bar to bring the bore to size, this time everything went OK.





Machining out Steam Ports

First Job was to accurately mark out the position of the steam ports as I’d got the scrap casting I marked this out as well, as I planned to have a practice on this first. The steam inlet port is 1/8” and the exhaust port ¼” wide, I acquired some slot drills these diameters. As my machine is graduated in metric, I drew out the steam ports in autocad with the required table co-ordinates.



I use the old Fag Paper Trick (cigarette paper for you folk living in the colonies) to find the edge of the casting, but I don’t run the machine, instead I use a plain set piece that is dead on 6mm diameter, salvaged from on old Video player, advancing the table until I feel a pull on the paper, the machine is zeroed and the position set to the co-ordinates.

A quick check that all looks OK with the marking out, and you can start to cut metal.



When milling slots like these I’ve found it best with my machine to first drill two holes slightly smaller than the slot at the extremes ends, this prevents the cutter pulling into the corner and giving you a “hockey stick end”. With my machine also I put a cut on from the same end, putting a cut on from both ends gives a series of steps in the slots, as the cutter is first pulled one way and then the other resulting in a slot wider than the cutters, and I take small 1mm deep cuts. Tip:- Don’t forget to lock the table in position.  It is quite a simple matter then to progress slowly and methodically to finish off the ports, it’s a job that I find satisfying.

Cutting steam ports I think is one of those jobs where it pays to have a practice on a piece of scrap first, to develop a method that best suits your kit and machine, you’ve nothing to lose, even if it means having two or three goes.

Drilling the steam ways into the valve ports was a matter of carfully marking out there position and transfering the line to the outside of the casting. The casting was then gripped in the machine vice, and getting it lined up with with the aid of a set square. As the drill has to go in on an angle it will run off if you don't start it with a good deep centre drill, filing a small flat will help, but even with this you will need to take it stead. These holes are on the deep side, and can run off if you don't take it easy and keep pulling the drill out to clear the chips.



Well that was the Job back on track a bit expensive, but I learnt one valuable leson:- you don't always need expensive castings

              

Have fun
 

Stew

[bogstandard]

Stew,

That proves my brain is on the way out, I now remember you showing me that on my first visit to your shop.

A real nice rescue.

John

[sbwhart]

Steam Chest

The steam chest is machined from a casting with the valve rod stuffing glands an integral part of the casting. First job was to clean up the casting and check it over with a ruler and look for blow holes. The casting was set up in the angle plate and squared up and the outside dimensions machined to size, it was then blued up and the inside features and stuffing gland position marked out.



The casting was set up in angle plate pushed up hard against a parallel so as to keep it square. The centre height gauge was used to locate the centr of one of the stuffing glands. A deep centre followed by a roughing drill followed by finishing drill all the way through, this was then drilled to depth with a 5/16*32 tapping drill and the hole tapped. The casting moved over and the second stuffing gland machined



Using a cranked turning tool the outside of the boss was then cleaned up.



The casting was set up in the machine vice on parallels and the inside cleaned up to the lines with a small end mill and the corners squared up with a hand file in the bench vice.

The clamping holes were marked out, the casting set up again in the machine vice and the clamping holes drilled. The steam chest was carefully positioned on the cylinder I used supper glue to fix it doesn’t set  straight away so you’ve got a chance to get the position right, alternately you could use two way type. It was set up in the machine vice with a tool makers clamp keeping the chest in place, the hole positions were spotted through onto the cylinder, the steam chest removed and the clamping holes drilled a tapped in the cylinder, taking care not to go too deep.

Tip:- use the tapping drill first in the steam chest only open them out to the clearance drill when you’ve spotted through to the cylinder.



Ok that will do for a few days

Have

fun

Stew

[Darren]

Please keep these coming Stew, I'm fascinated....

[Brass_Machine]

Nice Save Stew!

I am with Darren on this one. Keep em coming!

Eric

[Bernd]

Nice save Stew. Your showing some good use of a faceplate and angle plate to machine stuff.

I'm interested in what's going to go inside that steam chest.

Keep up the good work.

Bernd

[sbwhart]

Hi Bernd/Darren/Eric

Thanks for your support, I'm just finishing off the cylinder covers then I need to drill the cylinder block to take these, the next job after this will be the slide valves that go in the steam chest. I'm not quite sure when I when get onto these we're in the porcess of changing our computer system going over to a Apple Mac with a change of service providor and a home hub, so I can see myselve spending a bit of time on this, not being a computer buff I think it will be a bit of a pain 

I'll keep in touch through work whilst were getting new system running 

Have Fun

 

Stew

[John-Som]

Stew

I am finding the blow by blow account of your machining operations absolutely fascinating.  I must confess that so far I have not attempted to use the face plate and angle plate method of work holding and I suspect I may be missing out.
 
I had come to the conclusion that when boring out cylinders it is easier to set up the block in the machine vice and bore out on the mill ? This way I can, without disturbing the position of the block use DRO co-ordinates to position and drill fixing holes.  I also felt that it was easier to obtain a rigid set up on the mill than it is in the lathe. Maybe I am following the wrong route.

I would be interested in your thoughts on this.

John S

[sbwhart]

Hi John

I'm pleased that you'r finding my effort of interest.

Ther's more than one way to bore cylinders, the important thing is to drop on a method that gets the best result out of the equipment you have at hand. The main advantage in using the lathe is that you can use a good stiff boring bar and take advantage of the lathe's automatic feed, boring heads don't tend to be as stiff and small mills don't always have automatic feed.

But all this is relative depending on the size of bore etc, in fact I sucessfully bored out some cylinders for small traction engines (1" to 12" scale) using a boring head, in this case I held the cylinder in the verticle slide and the boring head in the lathe spindle,



Knowing what the best method to adopt, will come with experience, and knowledge, read all you can, ask as many questions as you can, and enjoy what you do. I've been involved with machine work all my working live, but I'm always learning I supose that's what makes this game so obsorbing.

Have Fun
 

Stew

[kellswaterri]

Hello all, I am inclined to agree on the lathe aspect for boring cylinders...mainly the fine feed fuction giving more control over the finish and also the rigidity of the boring cutter...I did all my cylinders on the face plate and as long as the set up is well balanced good results should be expected.
All the best for now,
                           John.

[kellswaterri]

 I also felt that it was easier to obtain a rigid set up on the mill than it is in the lathe. Maybe I am following the wrong route.
Hello all,
John S, would I be right that some ''Professional'' milling machines have a powered variable ''fine'' down feed, so your comment re. boring on the mill would be quite justified...I stand to be corrected
All the best for now,
                           John.

[bogstandard]

As Stew says, it is all to do with how happy you feel about doing the job.

No two people have the same thoughts on doing a job, it all depends on experience in using what you have, and how happy you are with the setup.

The safety aspect must always come into the equation, and if you don't feel safe with the setup, find another way to do it.

I will relay a fact that that was told to me over the last weekend by a friend who races motorcycles.

He had just heard that a well known tuning expert that he knew, had been killed.

The 'expert' was turning, using the faceplate of his lathe to mount a component on. The part threw off the faceplate, hit him in the chest, forcing a broken bone into his heart, he died instantly.

If that sort of thing can happen to a person doing it all the time for a living, we have to be doubly sure we have a rigid and safe setup when we do it.
 
I do faceplate work, but I am always aware of the dangers involved, and class it as one of the most dangerous things to do on a lathe. Vibrations due to being out of balance, can cause nuts to loosen off very quickly.

Lets be careful out there

Bogs

[sbwhart]

Good Advice John 

[sbwhart]

I'd like to thank John for reminding us of the danger of face plate work.

And to add to Johns warning I'd like to point out a few precausions we should allways make when doing any set up

1:- Only use clamps bolts T-nut etc that fit the fixture correctly, don't try and bodge with the wrong parts

2:- Check and double check that everything is tight down and won't work lose.

3:- Before powering up check that nothing is will catch and damage your lovely machine or injure yourselve:-  switch the power supply off from the machine and turn it over by hand.

4:- Run at slow speed all this face/angle plate work I did was with my machines slowest speed 70 RPM, before you power up check that you've got the correct speed selected, out of balance effects will be magnified by high speeds

5:- Don't stand in line with the work, stand to one side.

6:- Always wear safety glasses when doing any sort of machining, Keep your hair under a hat (if you have any) don't have lose bits of clothing flapping about, ties etc that can catch in the set up.

7:- Keep your hands or any part of your body well clear of moving parts.

When working out your best set up don't be afraid to break it down and start again, it may take two, three or even more atemps, take your time and get it right,  The safest set up is always the best set up.

And Have fun
 
Cheers

Stew

[bogstandard]

I would just like to add, I was in no way criticising Stew's setup, which was a nice rigid and safe affair. In fact it gave me a good pointer, must make me some of those cast lead weights, I always use clamping irons for balancing out, and the faceplate can soon become a bit crowded.

Up until fairly recent times, when mills started to come down in price and model engineers now have access to them, most of the work was done using faceplate setups similar to what Stew is showing, and was an acceptable method of machining.

The problem arises now, is that the techniques have generally slipped into the realms of forgotten about, and really, should you wish to try this method (and it is a good means of achieving what you want if you don't have milling machine access), then read up about the methods as much as possible beforehand, just so that you don't fall into any nasty habits by doing it by trial and error, that is when something nasty could go wrong.

I normally supply links for you to read, but couldn't find anything decent in the short time I looked. Even Rog's great link

http://madmodder.net/index.php?topic=594.msg2719#new

only had one paragraph on faceplates. So really you need to do a bit of homework first, before trying out this method of holding.

I am not trying to be a safety 'nanny', just trying to warn everyone that there are a few holes that you could easily fall into.

John

[Bernd]

All good suggestions gentlemen.

I'd like to add that a scrafical plate between the faceplate and work with holes drilled in the proper place for clamps can help at times. That way you don't need three hands to hold the part, tighten the clamp and hold the nut on the end of the clamp.

Also when it gets to the point of being very crowded with tooling the best bet would be to mount everything in a horizontal position. In other words take the faceplate off the machine. Place on a bench and mount the work and clamps. Ofcourse if it's to heavy this then will not be an option.

Bernd

[SPiN Racing]

Very very cool machine!!!

Im reading this watching all the progress, and cant help but be astounded by the work of people who made the real thing in the last couple hundred years.. with Huge stinking chunks of iron, to make the beautiful monsters they were.

I live in FLorida as you all my know.. and we dont have very much steam powered anything. BUT... when I was little in Ohio, around 5 or 6.. I remember seeing a steam show my parents took me to. This was likely around 1970 or 71.
The machines there were astonishing. Giant.. GIANT steam tractors with huge bands of steel with steel spokes, and steel spikes for the wheels. SOme had double wheels front and rear.. some had single. Many of the larger ones looked like some cross breed of trains and tractors. Many were cloth belt driven things, with all sorts of spinning wheels and gear reductions I would assume.

I also rode in a few steam trains when little, and still to this day cherish it.

Very cool critter you are making there. Cant wait towatch the progress as she comes together.

[Bernd]

Spin,

What your talking about are called traction engines. They were the prelude to the gas or diesel driven tractors of today. They were made on machines just like the home model builder has except they are/were a number of times bigger. They did the same thing, remove metal were needed. Just do a google on "traction engines" (with the quotes). You should see about 2 down videos showing these monsters in action.

Bernd

[SPiN Racing]

That is exactly the ones I was thinking of.

I have spent some time looking them over.. and thats what they were.

Amazing to a kid.. and now STILL amazing.

[bogstandard]

It is also amazing that they made them without the high tech machinery we have nowadays.

Heat and hammers were their main tools, with very rudimentary machining facilities.

They were craftsmen in those days.

Bogs

[Bernd]

Can believe it was done without 3D cad?     

Bernd

[sbwhart]

A book writen by LBSC    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.

 

back on topic for the next posting

Stew

[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. 

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 

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 


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    with that plate Stew.... You may find yourself detained at HM's pleasure!! 

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  )



Looking forward to seeing it come together,


Ralph.

[sbwhart]

 

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.

                                     

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. 






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.

 

Cheers

Stew