Engines > From Kits/Castings
Scott Flamelicker (Vacuum Engine)
Bogstandard:
My first real post about making engines on our new site, even though most of you have seen it before.
If I was allowed to have a strong drink to celebrate, I would.
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I gave up making things from castings a fair while ago, purely because the quality had got so bad (and still is amongst some of the well known suppliers).
A couple of years ago, I took a chance on a company I had never used before for castings, and bought two casting kits, this one and one for a full sized engine called the R & B, from Bruce engineering.
This one will be used to get me back into the swing of things, because no matter what people say, castings are not an easy way of making things, in fact, if you don't make them right, they can turn out to be an absolute eyesore, or it can cost lots of pennies buying new castings if you bugger up the initial ones. A lot of the second hand part built ones are sold by people who have become disillusioned when they thought they would be getting an easy build.
So now onto the way I get things done, others will have different methods, and as I don't like the way the instructions say how to build it, I will be doing it my way for some of the major parts.
So this is what comes in the kit. Everything you need to make the running engine, ball races, springs, even the fasteners, all except for the burner parts. That is because you have a choice of two methods, spirit and wick or butane/propane mix from a refillable gas tank. I will be going down the gas route, purely because in my steam days, I used to make refillable gas tanks, and I have a fully tested one waiting in the wings.
The quality of the castings, IMHO, are very reasonable, no surface blow holes or sags, intimating that something is amiss inside, and one thing I like the most, they haven't been over fettled by some gorilla using an angle grinder. I can take metal off easily enough, but putting it back on is a PITA.
The plans and instructions are well detailed, and I am sure if you follow them, you would end up with a working engine, which when finished, will be about 10" long by something like 6" wide, so not a small engine at all.
When I first bought the castings I had done a little bit of the cleaning up on the flywheel, just a couple of the segments. Now I have new files to fit the die filer, why waste energy.
In about ten minutes, I had the whole lot rough fettled, and not one single aching muscle or sore finger, it did a great job. This part will now be put away, and when the time comes to start turning and boring, a smaller and finer file will be fitted and it will be brought down to finished proportions.
This is the first piece that will get my major attention, the base casting. BTW, this engine is an Imperial build with BA fasteners, and because that are what are supplied, I will be using them.
So away with the metric measuring instruments, and in with the Imperial. Also, because the base is over 6" long, I will be using an 8" dial vernier rather than the 6" digivern.
The first thing that I did was to roughly check things for square and straightness, they were OK, then check for thicknesses and flatness.
By the time I had given it a good going over, I decided that the four top faces of the base bolt hole bosses were going to be my first datum points.
This is the first part that will need cleaning up, the bottom of the base. Once that is done, everything else should fall into place.
I don't like holding directly on the castings because of all the release tapers on them, so the first bit to be made will be a jig plate for it to be bolted to. That will allow me to mount and swing it about to known datums, and so everything will end up nice and square and straight.
If anyone is interested in a little more detail, here is a set of build articles that came from the public domain. I downloaded them and turned it into a PDF to keep it all together.
File name: Scott vacuum engine.pdf File size: 4.52 MB
As you will see. it is not a very difficult an engine to build, all it needs is to keep tolerances under control, as with all flame lickers, and a few specialist bits, like honing the bore and making a gas tank (if you go with gas). The gas tank build isn't shown in these articles, as I am worried someone with not enough experience or testing facilities would have a go and maybe hurt themselves, but the details are shown fully on the plans, or you can buy a commercial one, plus the feed tube and jet.
So I may as well explain things a little. Being from an engineering background, you always try to look ahead a little. Well with this post I am certainly doing that. A couple of hours spent making a few fixtures can save many hours over the build of maybe not an engine this small, but anything a bit larger and more complicated, and you will have trouble progressing very far at all without them, so I am taking the opportunity to save myself a little time, and keep things more accurate than I could ever have hoped for if I was just holding the castings in the vice.
First off, I grabbed a bit of my favourite stuff, 12mm thick ali jig plate. Then I machined it square on all sides, and it ended up about 3/4" over the size of the main base casting.
The parallel sticking up the side (there is another one in the opposite direction on the other side) is to help keep things from flopping about and vibrating while being machined, because it is sticking up so far above the vice jaws.
Almost any material can be used for the holding plate, as long as it is sturdy and accurate enough to do the job.
A cutout was put into one side, you will see why a little later.
You will also notice the odd hole here and there. When this stuff comes out of a factory as scrap, it has invariably already been used as a jig plate, you just gotta take what you can get.
So this is the basic holding plate made, all nice and square and flat.
I suppose you can guess what fits into the cutaway now.
So the next job is to find out where to drill the holes in the plate, and this is one of the very few times I will hold a basic casting as large as this in a vice. All because the are usually no straight sides on the casting, so making holding in a vice very unstable. I could have clamped it down to the bed, but that would have meant me removing either my vice or RT, and because I am only doing very light machining on it, I take the chance.
I have already decided that the top faces of these bolt hole bosses are going to be my first start datum points, so what I am doing, by eye, is finding the centre of each of the four bosses and spotting it with a ball nosed cutter.
This shot shows just how 'bent' the casting is, look at what should be a straight face on the side left hand top edge, and the same on the right hand bottom edge. Now you can see why castings can't be treated like normal bits of metal. They can be bent like a bananas at times, and what you should be trying to do, is not to take all the bends out, but get them looking a little more presentable.
So now having the four 'holes' spotted, I can measure up and come to a 'mean' position for the holes. By drilling smaller holes in the holding plate, than the larger ones in the base, it will give a bit of 'fiddle factor later on.
The small holes were precision drilled in the plate, and the larger hold down bolt holes were drilled by eye. On the underside of the casting, where it won't be seen, I put recesses for the screws that will be used to hold it down for initial machining.
Also I made four 1" long upstands that were threaded all the way thru. The upstands were first screwed to the holding plate.
The plate, tapped down onto parallels, had the four upstands all skimmed on the top faces to ensure they were all the same length
The cast base was then screwed downwards onto the four upstands, the screws went into the recesses while the sticky up bit of the casting went thru the cutout in the holding plate.
The whole lot was now gently tapped down onto parallels and everything given a final tighten up.
Then the gnasher came along and took off the hard skin, and the highs and hollows on the base. It took a cut of 0.020" to clean it all up
The fine sweeper then came on the scene, and with a 0.003" cut, took out all the rough machining marks and left behind a nice smooth, perfectly level surface.
I now have a main datum base I can actually work with.
Everything was cleaned down, the casting taken off and the upstands removed. The casting was then bolted, using all the same drilled holes, onto the holding plate.
Once it is mounted back onto the mill, by using a DTI, I can swipe down all the edges and standing up parts, and by gently tapping, I can get the casting into it's optimum position to have any machining done on it.
This will ensure, by using the holding plate as a reference, I will be able to locate all holes and ensure that they are all drilled in the right places and all parallel to each other. Almost an impossible job if you were trying to hold the raw castings by themselves.
This plate will also be reused for the other parts that need machining, so it will not be wasted.
I now hope this goes some way to explaining what the daft old bugger is up to.
John
lazylathe:
Nice one John!!!
A few more posts and i will be all caught up!
Your builds always teach me something new, which is what i really enjoy!
Andrew
Bogstandard:
I'm glad you like the posts Andrew, here is another one for you to pick through for tips.
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Most times, small casting kits just come with the instructions to file a flat surface somewhere on the casting and work from that. To me that is not acceptable, and why such a lot of beginners fall foul when doing their first casting builds. Usually ending up by throwing it under the bench when everything goes pear shaped.
Unfortunately, castings are all sorts of shapes, purely because the patterns have to release from the mould, and a flat face just won't cut it, so they have shallow tapers everywhere, nothing that you can get a true measurement off.
By me choosing this one major face to get perfect, now very easily, I can, if needed, get a few more faces square to it. Whereas before, I would be stabbing in the dark just where to drill holes and whether they are going to be parallel to each other.
As I said at the start, this build is a sort of prep for when I get onto the real deal, getting me used to working with castings again, because no matter what, if you do go in blind, you will almost certainly end up with some sort of error or bodge on the finished item.
I will say one thing though, working from drawings using bar stock materials is infinitely easier than using castings. It just isn't for everyone.
Now is the time to start to get the datums on the main bedplate sorted.
You will remember from last time, the bedplate was screwed down to the jig plate, but not yet squared up.
Mounted into the vice, as usual, bedded down onto a couple of parallels and the DTI was then brought into play.
I went all over the castings, looking for areas that matched for squareness, and by taking a few mean figures, I gently persuaded the plate to go into a position where, when machined, datum faces would be produced that would make sure that all the holes will be in the correct position.
The front and two side faces were cleaned up, the rear one can be done anytime as that will not be used in any marking up.
Some people will say I am removing too much of the casting features. All I can say is that I prefer to have an engine that is square, accurately made and not having to bodge things to get it running. If needed, the rough finish can be put back on once everything has been machined.
With the three sides cleaned up and totally square to everything else, it is time to get some measuring done.
The plate was blued up, and by using the two central upstands as datums, I found the centre point between them, and because I had the sides square, by using engineers squares, I could then mark up the centre line and an area of the plate to be machined to become the main vertical datum.
You can see here on my sketch and workings out the datum to be produced, and the exact positions vertically to the critical hole positions required.
Now the bedplate can be held accurately, it will be an easy job to get these holes drilled.
Don't worry about the vertical measurements being shown going to the wrong positions, they are in fact the hole centre heights from the datum face.
Back onto the mill again, and getting to grips with making the main datum face for the whole engine. What is required is to clean the surface off to remove all hi/lo spots. I found that taking a cut of 0.005" was enough to achieve the goal.
Once that flat area was completed, I jumped over to the cast in recess, and because it was full of lumps and bumps, I cleaned the whole lot up to make it look more presentable.
This is the finished result, all ready to have the bearing holes drilled and bored in the three uprights.
Now we are getting somewhere.
My DRO had remembered where the centre line was from yesterday, so it was just a matter of getting a zero datum from the end face.
Once that was done, it was an easy matter of spotting and drilling the three required holes. Horizontal work on the base is now done, except for drilling the oil cup holes, which can be done at any time, using the datums I have already created, even after it is taken off the holding plate.
Now this is where the plate comes into it's own. Swung to a vertical position, and clamped against the vice fixed jaw with a 3,2,1 block. This is plenty rigid enough for the jobs I am now about to do.
By having the 3,2,1 block hanging over a little, I can easily find the Y axis setting for the flat face I machined up last time.
And the machined end of the casting gave me the X axis position.
The X & Y were set to zero
And the figures that I had worked out were fed into the table, the table locks were then tightened up.
This put my quill spot on over the position that is shown on the plans. A hole was spotted and drilled.
A long series centre drill was then used to spot thru onto the second part of the casting.
The hole was then drilled using a long series drill.
Both holes in line. I don't have a machine reamer that will reach both holes, so this will be done with a hand reamer later.
I now moved to the second set of coordinates I had, then spotted and step drilled up to 12mm diameter.
The boring bar then came into action, and the hole was opened out to 13mm, the size of bearing supplied for the flywheel shaft support.
A nice slip fit for the bearing. Eventually, a pair of them will be Loctited into this hole.
So that is the baseplate basically finished, except for a little fine fettling and tapping one of the holes that I drilled earlier, and of course the three oil cup holes. I have already hand reamed the two cross holes.
I hope you can now see why I used the jig plate. Fairly easily, not only did I get the surfaces, top and bottom, level and parallel to each other, but also all the holes in the correct relationship and again parallel to not only each other, but to the base datums as well. So it was definitely worth doing on this build.
So the next step of the journey is to get that big lump of gunmetal into shape. I think this is one of those stages where I will have to hold the rough casting in the vice to get my first flat face, the bottom. Then take it from there.
John
lazylathe:
Ahhh Haaa!! You see i told you i would pick up some tips! ;D
I have a set of castings for a Coles Black Night Steam Engine that nothing is parallel or straight on them.
Now i have a tip on how to get them close and make some datum points for reference!
Andrew
Dean W:
I remember this one from another time, John. You picked a good one to help get things going in the Projects section.
Glad to see it again, if only to "re-remember" things that seem to dribble out of my head over time. :)
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