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Author Topic: Bringing a steam engine back from the dead  (Read 10049 times)

bogstandard

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Bringing a steam engine back from the dead
« on: July 28, 2009, 08:06:44 AM »

Just to give you a little insight into the journey I am undertaking.

I was approached by a member of the site, to see if I could 'do' anything with an engine he had built.

No names or pack drill, but he told me that I could show the rebuild on here, if only to help others that have gone or going to go down the same route.

I get requests like this fairly often, and it does go to show that there is a problem out there, and not always the fault of the unsuspecting builder, and I will be making a few comments about that along the way.
I have been on this rebuild quite a while, and have put many hours into sorting out this very poorly engine. In fact, if it was purely a financial decision, this engine would have gone into the recycle box, in the hope that maybe one day a lump of the metal would come in handy. I came to an agreement that I would take on the challenge of getting this engine to run if I could do it without time limits and any raw material costs, postage and packing and a small donation to my tooling fund was forthcoming, and we agreed a reasonable figure.
As it turned out, some bad news and medical appointments for my wife soon had me falling well behind schedule, but every now and again, I could get a little more done.
The engine still isn't completely finished, just a few cosmetic bits to do, but yesterday, the engine turned over very nicely thank you, when it got a dose of oil and air into it (by accident of course), you shouldn't run unfinished engines.
So spurred on by that revelation, by the time I have completed this post, it should be in the hands of the owner.

Just a warning, I will be using machinery that I am sure very few people own, but if you have a little think about the processes, you should be able to find your own way of doing things.

So, time to stop beating my gums, and show you what I have been up to.

First off, this is the engine in question. Click the link. I think it is geared towards a fairly low level of machining skills, and you should end up with a very useful engine to use in a model.

Now a statement, this engine will NOT run if made exactly to the plans. I will show the reason for this statement a little later.

http://www.stuartmodels.com/inprod_det.cfm/section/casting/mod_id/89

So now let's get to the article.

The member had built the engine as best he could, and because it didn't run when air was fed to it, he attempted to turn the engine over and bed it in using mechanical means.
First major mistake. If an engine won't run, DON'T try to force it to. There is invariably something wrong, and until it is put right, the engine will NEVER run.

So this is how it turned up, but I did break it down into component parts for the initial inspection, other things were found to be amiss a little later. Some of the problems lay with the builder, but the main culprit is what forced him to turn the engine over mechanically, and that is to do with the supplier.



SO, TO THE FIX.

After finding out that the machined port faces were square to the base bottom, I made up a quickie ali plate, with two parallel faces so that is could be remounted accurately into the vice after a little work was carried out on the casting.
In the top RH side of the pic, you will notice that I have already made a start on a new crankshaft.




Once the ali plate was tapped down onto a parallel, I levelled the port faces and tightened it to the plate when I had it running 0-0 along the parallel I was measuring against.




I was very surprised to find out that the casting is in fact brass, rather than the normal bronze. It must be that ST are cutting back on quality even further.

Anyway, getting away from my personal gripe, I roughly centred a 1/8" (3.2mm) endmill over each port hole and cut down to a depth of 50 thou (1.25mm).




Once all eight ports were machined out, I made some slugs of brass to fit in each hole. They were about 0.002" smaller than the hole size. To make room for the silver solder.




A bit of flux (I am trying a new one and don't know what it will turn out like, it is Tenacity#5, supposedly even better than my favoured 4A) down the hole, a plug inserted, and a small ring of easiflo 0.5mm wire around each one.




A bit of heat until the solder flows, then a quick quench followed by half an hour in a citric acid pickle bath. I did notice that the new flux was still very active while the job was heating up, also I noticed that there was a lot more copper plating from the pickle bath than I would normally find. It looks like the whole casting is made of copper, whereas normally, there would be just areas around the soldering that were copper plated.




After a good dose of surface grinding and a little bit of mill work, the casting is ready again to be machined, this time with the holes in the correct place.
I did remove a few thou of casting thickness, but there is still plenty of meat on it to take it. The new port holes won't be as deep as the originals, as I will only be penetrating the slugs and picking up on the oversized and out of place holes that were in there before.



I did no more work on the crankshaft, as I need to get the cylinders into their correct positions first. I will eventually mod the crank disc thickness to take into account the thickness I have removed off the casting, only then can the crank pin be fitted.


The gum beating is over, so the next bit will just be showing the processes involved.


Bogs



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SteamboatPhil

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Re: Bringing a steam engine back from the dead
« Reply #1 on: July 28, 2009, 09:39:25 AM »

Nice job so far Bogs, I did one a while ago for a club member, and like you have found the drawings are not all they should be. Fortunatly I tend not belive a lot of drawings so had checked before (just as well), but the whole building of the engine took a lot longer than it should have (as I think you are finding out)
Keep up the good work
PS is it me or is the crankshaft bearing hole off centre?
Phil
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gondolier88

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Re: Bringing a steam engine back from the dead
« Reply #2 on: July 28, 2009, 10:16:11 AM »

Shocking that a company like ST are supplying castings like that- come back Cheddar thats what I say!!! <*<

By the looks Phil I think it's the casting that's off center and the bearing is correct- time was you could have taken for granted a ST casting being spot on.

Greg
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bogstandard

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Re: Bringing a steam engine back from the dead
« Reply #3 on: July 28, 2009, 11:07:16 AM »

You are quite correct Greg, it is the casting that is out, the hole was checked and was near as damn it spot on.

I don't want to rub anyone up the wrong way, but nowadays, not just ST, it is very difficult to find good quality casting sets any more in the UK.
Over the years, all the old foundries have gone, and it seems they are using back yard casting people to produce them, and are overcharging for a grossly inferior product.

I have a friend that gets me flywheel castings from the US, that cost half the price they do here, but the quality is absolutely fantastic. They are even heat treated, and machine like butter. The ones produced here are hard skinned, mismatched, full of "xxxxx" and blowholes, and if they look similar to what is required, they will do.

Phil, it would have been a great deal quicker to build from scratch rather than do a rescue, but it is the challenge that I enjoy.
A couple of good days work and you can easily knock one of these up from a kit.

Bogs


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bogstandard

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Re: Bringing a steam engine back from the dead
« Reply #4 on: July 28, 2009, 03:42:24 PM »

Could whoever censored this post please PM me and tell me what the offending word was.

As far as I am concerned, I used correct terminology, and would be grossly insulted if the correct english language terminology was censored.

If I did make a mistake by accident, I would like to know anyway, just so that I don't do it again.

The next part of this topic is ready to be posted, but I will not carry on if the english language in it's correct context will not be allowed, as the total meaning of such posts will be lost.

Bogs
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Colin Bishop

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Re: Bringing a steam engine back from the dead
« Reply #5 on: July 28, 2009, 04:50:38 PM »

Looks like that's automatic censoring applied by the website software. Try using the word with spaces between the letters.

Colin
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bogstandard

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Re: Bringing a steam engine back from the dead
« Reply #6 on: July 28, 2009, 07:47:46 PM »

Thanks for the explanation Colin, but as I cannot remember what I had written, it is very difficult to rectify. But if what I suspect, the word is "xxxxx" (s-l-a-g), then the dictionary really needs looking at. We will soon know, because if it picks this up, it will get censored.
 
Well I just did a preview, and it did change it, but I don't know any other correct words to replace it with, other than even worse ones. Maybe I should use those with spaces in between.

Anyway, now we know, if you see something blanked out in my posts, it is a word that has two meanings, but my meaning isn't the bad one.

So rather than just showing the finished bits, I will also show how I do it. It might not be the same way as other people do it, but I know my method works for me.
This is so, if you are making an engine, and you are not sure how to do something, my way just might show you the direction to go in.
If you don't understand anything, please ask, because some of the things us metal murderers get up to, can look like black magic to the layman.

Don't get confused by the gizmos, these are used just to make my life a lot easier, and other methods can be used to achieve the same result. In fact, the second pic down can cause confusion. I have made a system where I can swap my rotary table (RT) chucks between the lathe and RT. So I can turn a piece on the lathe, spin the chuck off with the part still in it, and then mount it straight onto the RT, and vice versa. Not a thing that is normally done.

Now to it.

Using my coaxial indicator, I centred up the RT to the quill (the up and down bit that you mount the chuck or tool holders into).




Having previously turned up a holding mandrel on the lathe, and without taking it out of the chuck, the chuck was unscrewed off the lathe, and screwed onto the matching thread on the RT. This put the mandrel on the centreline of the quill.




The RT was set to zero on it's angle scale, and the machine DRO was zeroed up all round. This is showing it in metric, just after this, I reset it to read imperial, as that is what the drawing calls for.
The X (side to side) axis on the mill was locked up, as all movement for this operation will be done on the mill Y (front to back) axis and the RT degree scale. Around the edge of the rotary table, it is marked 0 to 360 degrees with a fixed pointer to show you how many degrees you have moved.




The casting was dropped onto the mandrel, thru one of the cylinder pivot points, but it was not tightened down, yet.




This is the method I use to make sure that the holes are drilled perfectly in the correct position around the cylinder pivot, even though the pivot centre and the crank centre might be slightly out. This will automatically ensure that when the cylinder swings from side to side, even if the centres are slightly out, the holes will line up perfectly with the ports in the cylinder (assuming the holes in the cylinder are on the centre line, which on this engine, they are).
This shot is taken slightly from the side to show what is going on.
I mounted up a bit of rod, the same diameter as the crank hole into the chuck. By moving forwards on the Y axis only, disregarding what the readings were, I moved it forwards until the rod slipped nicely down the crank hole.




Then I tightened up the screw to lock the casting onto the mandrel. So now I had the two centres perfectly aligned down the Y axis. The rod was withdrawn, and the Y axis was wound back to the zero position.




This is what is required on the drawing. The PCD (pitch circle diameter, an imaginary circle that the centres of all the holes lay on) is 15/32", so that was halved, giving 15/64", and the Y axis moved forwards by that amount.




As shown on the DRO. The Y axis was then locked up. All work now is using the RT and the quill.
0.2344" is the same as 15/64", but in decimal




As can be seen from the drawing, there is a spread of 38 degs between the port hole centres. That means 19 degs either side of the centre line.
So a quick calculation gave me settings for the RT. 19, 161, 199 and 341 degs. 19 degrees either side of the 0-360/180 deg centre line. A quickie centre drill at those settings, followed by drilling down thru the silver soldered  plugs, until the correct sized drill hit the previously drilled ports.
Once one side was done, the same thing was done on the other cylinder pivot point by repeating the exercise.




I took this shot on an angle to show how the new holes join up with the previously drilled out of position holes. It doesn't matter that they are not quite in line, the steam will find its way thru. The main thing is that the holes on the surface bearing face are in the correct position now.



So basically, the main casting has now been rescued, and things are as they should be.

I do hope that this isn't too technical for you to understand, but I don't think there was an easier way to show it. The position of these port drillings is one of the most critical parts on an engine like this for it to run smoothly and efficiently.

Don't worry, most of the stuff to follow isn't as technical as this,


Bogs

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gondolier88

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Re: Bringing a steam engine back from the dead
« Reply #7 on: July 28, 2009, 09:19:22 PM »

Very good explanation- those holes were SO far out of line it's almost unbelievable!!

Ahhhhh a workshop...one day! :((

Got an interrim inspection from our estate agents in the next couple of weeks- will have to make our front bedroom look less like a brass foundry/boatyard and more like a casual hobby room!!!

I like the idea of the interchangeable chuck- why center work multiple times when you can do it once- prividing ST havn't made the chuck though!!! %) {-)

Greg
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bogstandard

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Re: Bringing a steam engine back from the dead
« Reply #8 on: July 28, 2009, 11:02:57 PM »

Greg, even with the holes that far out, the engine would still have run, but a lot more inefficiently.

It has taken me many years to get a proper workshop.

Imagine getting a large mill/drill up a flight of stairs, then standing it on a sheet of steel to stop it going thru the bedroom floor. That was my first 'real' workshop. You make do until you have the time and means to do it properly.

I was lucky, and over the last year or so have done a complete rebuild, full of most of the toys I ever wanted (space prevented me going further). That will now have to last me now, until I go to the big workshop in the sky.

Just take things steady, and build it up gradually.

But always remember, it is the machinist that makes the machine sing, not the other way around.

You can have the best equipment in the world, but unless you can use it correctly, it means nothing.

Bogs



 
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bogstandard

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Re: Bringing a steam engine back from the dead
« Reply #9 on: July 29, 2009, 05:22:59 AM »

I left it last time with the main casting sorted, and the cylinders to be brought up to spec.

I will wait until I have finished the bottom bearings of the cylinder before deciding what to do with the pistons and rods. But just to make sure, I gathered the bits together to make sure I could make new of everything if required.




This is a lump of PB2, a little more difficult to machine than PB1, but it was the correct size for the job. So armed with a razor sharp HSS tool, I wacked off the metal until the bearing spigot was at the correct size.




Now this is where a benefactor comes onto the scene. Look what he dropped off. I have been contemplating buying one of these for a few years, but never got around to it.




WOW, it went thru that tough bronze as though it wasn't there. It works on the principle of deforming the chip as it comes off the cut, so stopping it jamming around the tool tip. You can see the swarf on the crosslide, it just curls it up in two dimensions, and throws it out. Unfortunately this tip holder can only go deep enough for a 7/8" bar, so I will look around for a longer nosed one that will cope with larger diameter bars, now I know what a wonderful system it is.




The first one ready for the next stage.




Soon followed by it's twin.




Now comes the stage where people make their main mistake. They do one component machining operation, then do the next component, then go back and drill and ream holes.

WRONG

You must finish off each component separately to it's conclusion, only then change over the component and carry out the same ops.
The first op is to machine the spigot for a wringing fit into the bore.




Then drill and ream, or bore for your finished sized hole. By doing it this way, it will ensure that the hole is truly concentric with the bore. Only then do you swap over and do the next piece. The outside shape has nothing to do with the well running of the engine, this spigot and concentric related hole is the bit that needs to be spot on.




Once the two bearings were done, it was found that the pistons and the rod ran perfectly in the bores, so I decided just to make new pistons which were a little small on diameter, and will be made at a future machining spell.
Getting away from the pistons and end caps now, notice how close the holes are to the port faces. I think that the cylinder covers were fitted first, then the port faces were machined down a little too much. To such an extent, that the brass screws that held the covers had almost half the heads machined away.

I can see another fix coming on.




Grab a bit of brass rod on nearly the right size for 7BA. Then a quick and dirty exercise to make a length of threaded rod. 30 seconds work to cut a length of thread about 3" (75mm) long using the die holder off the lathe and a rechargeable drill.




I wasn't too worried about the quality of the thread, as long as it screwed into the holes.
Like the repair to the main casting, bits of rod were screwed into the holes after first dipping them in flux. Then they were silver soldered into position, using the same method as used on the main casting.




A quickie machining job and the cylinder was back to square one, ready to be drilled in a better position.




The problem now was that I had steel cylinder covers with holes in the wrong place. So a bit of brass plate was cut to size and annealed, a mandrel turned up to bend the brass around to get to the basic shape, then a bit of bending in the vice soon had two new brass covers made. I will drill, tap and fix them in position after I have made the new pistons.



Almost flying now, something must go wrong soon.


Bogs

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gondolier88

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Re: Bringing a steam engine back from the dead
« Reply #10 on: July 29, 2009, 09:39:24 AM »

Hi Bogs,

Theres no stopping you!!! Those PB guides will provide a lot better bearing surface anyway.

Manufacturing aside, the design of this engine isn't too bad- I like the larger dia. piston rods and it's nice to see an oscillator with cylinder covers too.

Your right with the building up gradually- i've got some really good bargains over the past few yaers which allow me to do what I can without proper machine tools, but i'm at the point where a lathe would really let me start doing what I want to- what's your opinion on getting an old belt-drive lathe for example and putting a 1/2hp motor on it as my first lathe- or would that be a silly thing to do?

In my view if I could make one engine on it from castings then it would pay for itself financially, but many times over by teaching myself as I go along.

Greg
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bogstandard

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Re: Bringing a steam engine back from the dead
« Reply #11 on: July 29, 2009, 11:40:15 PM »

Greg,

I have been down the route you suggested, and the lathe cost more to get it working correctly and accurately than it would have cost for a decent second hand machine. But on the other hand, the lathe is about 25 years older now, an old myford ML2 with broken castings, and my friend still uses it almost daily, so it looks like I didn't do too bad a job of it.

Anyway, back to the refurb.

As can be seen from this pic, the holes were a lot more out of kilter than I first thought. It is no wonder that the port faces weren't sitting against each other.




This was just too much to try to straighten up, so there was nothing else to do other than go on one of my silver soldering binges.
The port holes were out of line and too large on a couple of them, so I went the whole hog and plugged up everything there was, even the port drillings, and start from scratch.
First off, make the bad holes even bigger. Stick a few bungs in there and get out the blowtorch.




This is how they ended up. Just like original, with no holes, but with an extra bit of meat here and there.
A little bit of machining soon had them looking a bit sweeter.




Faced off, and all holes in their right places, and square.




On the ST plans it showed the port drillings being done on an angle, from the port face to just inside the cylinder top and bottom.
This engine, as far as I can ascertain, is really for the beginner to model engineering, his first build maybe. To put angled ports on such an engine is absolutely stupid. A newbie will have trouble cutting things on the flat, never mind on an angle. Even I get it wrong sometimes, and I have done a few in my time.
So, I have made the port drillings how they should have been designed into an engine of this type.
Make a recess top and bottom to allow steam to enter the cylinder, drill the ports straight in from the port face, then drill straight down until the two parts are joined. Dead easy to do, and almost guarantees success for the newbie.



Because of all the hot work that has been done on these cylinders, I suspect that the bore has distorted slightly, plus any flux runoff may have eaten into the walls a little. So I will make a plastic cylinder hone, and grind the bore back into shape before I make the new pistons to fit, I am only talking about a couple of tenths, so it won't really make much difference to the spigots I have turned on the bottom cylinder bearings.

I grabbed a bit of PVC rod and turned it down to about 1 thou under bore size. Then using a couple of different grades of valve grinding paste, then finishing off with a chrome cleaning liquid, I got the bores nicely cleaned up. I am not after micro finishes and sizes on these bores, as long as they are smooth and within a thou or so they will be fine. Don't go chasing your tail trying for perfection. For an IC, flame licker or Stirling, yes, then try for the best you can. With these small engines, near enough is usually good enough.




Nice semi matt bores, and both measure the same.




I am making new pistons, and here they are in rough size. They still need to be turned down to length and diameter (0.002" or 0.05mm smaller than the bore).
I have now marked each piece as part of an assembly, with either one or two tiny pop marks on each part. This will ensure that when I have finished, I will have two perfectly fitting assemblies, with all parts matched to each other.




I found in my little stash, two perfect matched o-rings to the crappy ones that were in there. So I did a quick check on the plans for groove dimensions. If I had made the grooves to the plans, the o-rings would have been sitting lower than the piston edges, and so performing nothing to sealing the pistons, just there for decoration. The great ST strikes again.
So armed with a bit of paper and a pencil, the CORRECT dimensions were worked out.




Pistons now to size, o-ring grooves and widths correct.
Now V-E-R-Y happy with the piston and ring fit. They should work perfectly.




Bogs


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Martin [Admin]

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Re: Bringing a steam engine back from the dead
« Reply #12 on: July 30, 2009, 11:29:13 AM »



 I've never seen a steam engine built before, it's a fascinating read!
 Please go into as much detail as you like .... I, for one, am learning all sort of things I never knew existed!
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oldiron

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Re: Bringing a steam engine back from the dead
« Reply #13 on: July 30, 2009, 11:52:45 AM »

  You can definitely include me in those very interested. I build live steam myself, the railway variety mostly, and I'm very interested in your techniques. I've learned a few more along the way. Just because we all don't say anything doesn't mean we aren't interested. I'm content, for the moment, to sit and watch and listen and learn.

keep it up

John
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bogstandard

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Re: Bringing a steam engine back from the dead
« Reply #14 on: July 30, 2009, 11:56:45 AM »





So now onto the big ends. I like the very hard wearing properties of ali bronze, so instead of phos bronze, I wacked some hex ali bronze down to the required size.




It was soon into the lathe for a bit of shaping, drilling and tapping.




The pair were then slipped onto the mill and cut and drilled to shape. Great I thought, everything had gone smooth as silk and I had the new big ends within 5/10ths of drawing, so basically, spot on.
Before I cleaned them up, I wanted to see how they fitted. Then the problem reared it's ugly head, they didn't, fit that was.




As you can see, they wouldn't fit onto the crankpin.
Then I thought, how come a great company like Stuart Turner could make something that was wrong, I must be me at fault, as they are so great, they would never make a mistake or ten.
So I double checked the parts to drawing, yes, I had made them correctly. So why didn't they fit?
Oh! Dear, someone in the world famous ST empire must have had a slip of the pen and marked up the plans incorrectly, Oh! and someone must have forgotten to proof read and test the drawings, FOR OVER 10 YEARS!!!.




I just wonder how many pairs of these big ends have been made over the years, and how many have had to be remade, just like I will have to do, and how many people must have complained about it, and how long would it have to be before ST put the plans right. Plus maybe reimburse the poor newbie for the wasted man hours and materials, not.



So if anyone wants a duff pair of big ends to not fit a Stuart Turner V-Twin engine, the send me the cost of postage, and you can have them.

It is my own fault, I know how bad Stuart Turner casting sets and plans can be, I should have checked and quadruple checked beforehand.

I got a new pair of big ends made, with the holes in the correct place this time. By the time I had finished working them, the ali bronze had gone rock hard, and I had trouble dressing the burrs off them. Just what is needed.




The next job to do was to get the tensioners made and sorted for the other side of the engine. New spring holders and knurled nuts were made up, these just need a set of acorn nuts making to lock everything up when the tensions have been correctly set.




This shows the throttle valve area.
No instructions for making the stop or setting it up came on the plans, so using my experience on what is required, I fitted a stop pin, and dressed the throttle stops. This is so that when in the fully one way position against the stops, the horse shoe cutouts in the valve face align perfectly with the port holes drilled in the main block, so depending which way the valve is swung, either fully fwds or reverse is obtained, and variable throttle and stop is obtained between the two.




Now that I had the port faces being pulled against each other, and putting the big ends in their running positions, I could dress the the face of the crank disc to give a little running clearance. I gave it 0.020" (0.5mm), which should be more than enough if ever the cylinders get blown off their faces at an angle because of excess steam pressure.




Now that I had all the bits set up for correct clearances etc, it now warranted setting up the RT to do a little offset drilling. Waiting until now meant I only had to set up the RT just the once and get all the bits done at the same time.




The RT was centred up, offset in the Y axis for the drilling for the pin in the crank disc. Notice that it is sticking up from the chuck jaws a bit, this saves drilling into the chuck jaws as you break thru.




Next offset was for drilling the holes in the bottom cylinder bearings. Because I didn't want to drill into the chuck jaws, I put a couple of washers underneath as the jaws were tightened up, just to raise it away from the jaws slightly, so as the drill broke thru, no damage would be caused to the jaws. The washers are removed before starting to drill.




The same offset was used for the top caps, but thinner washers this time. I didn't have as much to hold onto with the chuck jaws. I was just a little more careful as the drill broke thru.




All bits drilled, and the washers lived to be used another day.




Now these bits have been finished, it allows me to progress a little further and get other parts that have been made previously, fitted onto other assemblies.




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oldiron

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Re: Bringing a steam engine back from the dead
« Reply #15 on: July 30, 2009, 12:24:08 PM »

  Thanks for continuing with the build.
 Your comments on poor drawings aren't limited to ST. A number of years ago i started into LBSC's "DORIS" with drawings and castings marketed by a well known manufacture. I believe the drawings were done on 1948, and yet the still carried at least one major measurement flaw, that being the distance from the frame to the cylinder center line being short by .062". I, and I'm sure many others didn't pick up on the mistake until after the swarf was on the floor. I've made the correction successfully, but why, in all those years, weren't the drawings corrected.
  I have a question going back to the earlier posts. I have a rotary table that appears very similar to yours. Like you I made a threaded mandrel to fit the MT center of the table. Problem is, how do you keep the mandrel/chuck assembly from turning when you're doing machine work? For anything but straight down drilling (such as for valve covers) the assembly can't be relied upon to stay in place.

John
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bogstandard

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Re: Bringing a steam engine back from the dead
« Reply #16 on: July 30, 2009, 12:49:04 PM »

John,

That is a standard Myford adapter.

You will find it about 2/3rds the way down the page.

http://rdgtools.co.uk/acatalog/MYFORD_LATHE_USERS_NEW1.html

All I do is treat it as though I am fitting the chuck onto a lathe, spin it on and wait for the 'clunk'. I have never had it come loose, and I have done some heavy machining with it. The only down side is that because it sticks up in the air a little, and so is not quite as rigid if the chuck was bolted to the table. But that is easily overcome as you can take out the adapter in no time, and mount the chuck as normal.
 
I really use this in a production capacity mainly, so very rarely do large pieces need to be turned and then RT mounted or vice versa.

There is also the need to consider that you do loose a little on the throat depth of your machine, so really it should not be considered viable for a smaller mill with limited throat distance.

Bogs
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Colin Bishop

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Re: Bringing a steam engine back from the dead
« Reply #17 on: July 30, 2009, 05:24:49 PM »

A bit belatedly, I have been following this thread lost in admiration. Like many others, any comments by me would be quite superfluous - glad you are carrying on.

Colin
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boatmadman

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Re: Bringing a steam engine back from the dead
« Reply #18 on: July 30, 2009, 05:28:55 PM »

Bogs,

I am watching and reading avidly! Its great to see how you do this.

Ian
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bogstandard

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Re: Bringing a steam engine back from the dead
« Reply #19 on: July 30, 2009, 07:36:21 PM »

Thank you gents for the comments.

It seems like that people really are interested, and I hope that my ramblings now, and maybe in the future, do help a few people along their journeys.

It takes all sorts to make a model boat.


Bogs


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bogstandard

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Re: Bringing a steam engine back from the dead
« Reply #20 on: July 30, 2009, 08:50:38 PM »

The engine is now going together rather than having fixes done on it.

I think that this post might be of use to a few of you who build small engines, or a tip about holding round things that can be used by anyone.

This shot shows a normal small engine crank build, and to me is one of the worst types.
What should be done?, drill a slightly undersized hole, wack a pin in and hope it goes in straight? Or make a slightly oversized hole so that you have clearance for silver soldering, wack the end of the pin to deform it so it holds in the hole whilst soldering, and again hope it ends up square? There are many ways of doing it, but I will show you how I go about it to almost guarantee that the pin will be square and secure in the hole.




First thing I do is thread the hole, to about the same size as the normal plain hole.
Then I turn the pin up out of silver steel (drill rod) that is rather larger than the original sized pin.
First off you turn the length and size of the crankpin you want to go thru the big end. Make sure you end up with a nice clean shoulder where it joins to the main bar.
Then cut a length off the rod to allow you to form the other end.
Holding the crankpin in your chuck, you turn down the sticking out end to the size that is required for threading, and while you are doing that, form another shoulder, like shown. My integral 'washer' is about 0.025"(0.6mm) thick. Then thread the stub to whatever size that is in the crankdisc. Turn a small undercut on the thread, to ensure it screws all the way into the hole.
After that, turn down the diameter of the 'washer' so that it doesn't overhang the edge of the crank disc.




A little high strength loctite on the thread and it is then screwed into the hole tightly. The small shoulder will ensure that the pin ends up perfectly square to the crank, even if the hole was tapped slightly out of square and the thread isn't too tight a fit.
Dress off the back of the hole so the thread is flush, and put one or two very small pop marks around where the thread and hole meets.
If ever the pin gets worn, a good grip with a pair of pliers or vice grips and you should be able to screw it out, make a new one and refit it. I don't harden the pin, as I prefer the replaceable pin to wear rather than the big ends. It is easier to remake a pin than big ends.

Notice the pliers I am using. Go to the local market and buy a couple of pairs of the larger type electicians pliers, mine were 1 squid a pair. Clamp them in the vice, with a washer between the tips to hold the jaws apart slightly. Then just drill a series of growing holes, these are metric with 0.5mm between each size. Make two sets, imperial and metric if you want. The jaws drill fairly easily, similar to a slightly tough cast iron. They are indispensable for tightening things up without damage, or holding round parts whilst tightening or grinding or WHY. The holes don't have to be perfectly spaced or square to the jaws.




When I made the basic crank and disc, I made on the back of the crankdisc a 'rubbing face' to reduce friction, I left it overly long because I didn't know how thick my 'washer' would end up being. After the pin was made, I reduced the rubbing face by the thickness of my washer. So now everything has nice small running clearances.
But those damned big ends came back to haunt me yet again.




When I tried to turn the engine over by hand, I was STILL getting interferance, even though they were made to the modified drawings. The pic shows what I eventually had to do. Hack the corners off. Then the engine turned over very nicely after that was done.




Bogs.
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craftysod

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Re: Bringing a steam engine back from the dead
« Reply #21 on: July 30, 2009, 09:34:18 PM »

Bogs
I as many others are watching this thread,to watch someone as skilled as you,and many other skilled builders.
As has been said,we cannot ask questions,as your far above some of us with the engineering,but it is fascinating
to see (and your pics and words) how you go about solving problems.
And you are giving other skilled men like yourself another way around how to correct the wrong
Keep posting
Mark
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gondolier88

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Re: Bringing a steam engine back from the dead
« Reply #22 on: July 30, 2009, 10:19:19 PM »

Love the pliers idea Bogs, will make a pair of those asap!

Greg
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Shipmate60

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Re: Bringing a steam engine back from the dead
« Reply #23 on: July 30, 2009, 10:47:05 PM »

Topic tidied up with some posts deleted and others modified to ensure continuity.

Bob
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bogstandard

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Re: Bringing a steam engine back from the dead
« Reply #24 on: July 31, 2009, 12:32:37 AM »

Many thanks Bob, it will now look correct to the casual viewer, with everything in the correct order.

I thought I had better explain what I call a "rubbing face", there is most probably a correct name for it, but I tend to call things by what I see if I don't know the right title, maybe I should have called it an 'anti friction raised portion'. If someone knows, please let me know.




In engineering, if you have plain faces rotating against each other, as this engine has, you machine a small proud bit so that it holds the turning part away from the main face. I hope the sketch shows what it is about.

It is that bit which I reduced in thickness, to allow for the thickness of the shoulder on the crank pin.

I could just use a washer to do the same job, but I machine it on, because if the engine is disassembled then rebuilt, the washer might be forgotten, and the engine then runs like a bag of nails.
Remember all the times you put something back together again, and there are bits left over. Well if it is a washer, it might have been used for this purpose. Expect loud noises.


Bogs
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