Engines > From Kits/Castings

Scott Flamelicker (Vacuum Engine)

<< < (2/6) > >>

Bogstandard:
Yep Dean, this post has been moved from place to place, and now, hopefully it has now found a permanent home where, after these build notes, up to now, are displayed, the engine can actually be finished off. That is of course if I am able to do it. After a layoff of almost a year due to personal issues, it will be difficult for me to get the old sinews moving again.

Andrew,

That is why we all post on here, to me, not for the glory, but to help people like yourself who are following.

Why struggle, trying to figure something out, when someone has already done all the hard work for you.

I still read almost every build post avidly, there are tips I can pick up as well.

################################################################################


Even though it looked OK from a distance, when I got up close and personal with this casting, I was a little disappointed, as will be seen. I spent nearly an hour, trying to make a decision how I was going to machine it back to how I wanted it. At least one specific face had to be machined perfectly square to the foot, and then bored for the cylinder.

As you can see by the fettling marks, this side has an outwards bulge, and when handled, is more pronounced than shown on this photo.




As can be seen from this shot viewed from the side, the shape is more like a leaning parallelogram rather than an oblong.



When viewed from the top, you can also see that it tapers from one side to the other.
Luckily, although in parts, the casting is under nominal size, there is enough meat on it to get it all square.




I decided the best place to start was the already fettled base, which was reasonably flat, so it was gripped in the vice with the base set level to the table.
I just needed to make sure the cutting forces were kept as low as possible.




With a bit of extra support from the backstop, I used my flycutter, cutting in one direction only (towards the backstop) and with only a 0.005" cut, the base was cleaned up after a couple of passes.




This shot shows just how much inwards lean at the top there is on the sides. The next cut has to be getting the side face that requires boring square to the base.




The casting was set up again in the vice with the base sticking out.
By using a 3 2 1 block and a nut and bolt just slightly smaller than the holes in the block, I jacked the base end up so that the base was perfectly square to the table. Hopefully it will remain in that square position while the face is machined. The block and jacking screw were left in position to help support the part.




I tried to skim this unfettled face with my flycutter, but the skin was a little hard and didn't really want to cut. You can see by the machining marks just how far out this face is.




So I resorted to one of my favourites, a 16mm razor sharp cutter. This went thru it like it was butter.




This slightly fuzzy shot shows just how bent the face was, and this isn't down to full cleanup depth yet.




After going down to just over 60 thou, I had the face cleaned up, and yes, it was perfectly square to the base.
Now I have these two faces, everything else will be an easy job. Even though the angles are slightly out to each other on the two angled faces, as of yet, I have decided they won't be machined, and left as cast.




To me, it is looking better already.





Last time I had got the two faces square to each other and nice and flat. This time is getting the third face square or parallel to the other two.
This is the standard set up technique, one good face down and tapped onto a pair of parallels, with the other square and flat face against the fixed chuck jaw. A piece of soft material, in this case ali, is placed between the moving jaw and the fourth rough side. Doing that puts all the pressure onto one small point and takes up some of the irregularities on the job. You don't want to go putting on heavy cuts while in this sort of setup, in fact, I changed my normal cutting direction, from X to the Y axis.




The top surface was soon cleaned up.




I need the big offset hole in the top cleaning up for a feature I will be adding, so the boring head was roughly centred and set to work.




This is as far as I want to go with this piece at this time. It still need a few small holes drilling, and boring for the cylinder sleeve. But I want to wait until that is finished first, as the boring is a more controllable exercise than bringing the sleeve down to size.



John

Bogstandard:
Some of you will recognise this bit of brass left over from the swing up threading post, but the threaded bit on the end is just perfect for what I want.
I just took the thread down until it was cleaned off.




A quick change of tool and I had a spigot of the right size formed on the end.



A large profile tool soon had a nice radius formed.




Drill out the end a bit.




Then opened up to the required size. All this by the way is being done by eye, except for the spigot on the end size.




The bit I want was parted off.




Now comes the experience bit. All my working life, and a bit before, I have been hand shaping parts on the lathe, using a few basic tools. The basic name for it is called graving, a basic watchmakers technique which uses shaped hand held cutting tools similar to what a wood turner uses, but much smaller. I am not using those this time, just files and a sanding block, and I use it just to give me something unique that is very quick to do.

It is not difficult at all, and a lot of lathework started off just this way, but it can be dangerous if you don't know how to hold the tools correctly, and also, you are working with your fingers very close to a fast spinning chuck, and as you all know, machines have no feelings, and they will chop you up just as easily as they chop up metal and other materials. So unless you are VERY safety conscious and scared to death of your machines because you know what they can do to you, don't even try it. I am only showing the basics here, and even though it can be dangerous, it is a perfectly recognised way of shaping items in the lathe.

First off, the part was remounted back into the self centring four jaw chuck with the bit I want to shape up to the outside of the jaws. Using hand and eye coordination, plus a boring bar, I roughly profiled the inside of the part to match the outside bit which had been machined.




Using just a few files and a sponge emery block, I blended all the rough cuts into one smooth flowing rounded shape, getting rid of all the maching marks at the same time.
A sheet of white paper put onto the background helps in seeing that everything is blended together, having just nice rounded curves with no flat spots.




A quick dose of Mrs Buff had a nice basic shine added to the part. Just before final assembly, it will be given a final deep lustre polish.




As you have most probably already guessed, this is a nicely shaped funnel for the water jacket,  instead of the horrible gaping hole that is shown on the plans.




Total time, just over an hour. Time well spent as far as I am concerned.


I don't know if I put people off by my comments about hand graving and the safety issues, but in all honesty, if you care to take the time and train yourself to work very closely to the chuck, it can be a very rewarding experience.

I have forgotten the amount of boiler funnel caps I have made for people, but something like that can really put the finishing touches to a steam plant or a distinguishing part for an engine can really set it out from the ordinary.

As I have shown before, where I turned up shaped steel handles, they are not available commercially, but if you can have a go yourself, almost any turned shape is possible. From little hand turned finials in place of nuts as on my mine engine, to a spinner shaped cone to fit my small turbine and elbow engines. All done in a matter of minutes, and totally unique.

For my graver rest, when I use a graver, I just mount a bar in my toolpost and bring it close up to the job, so no special lathe fitments are required. BTW, great gravers can be made out of worn out files, just grind up the shape you require on the end and leave most of the teeth on there, they give a good non slip surface to hold onto, but make sure you leave the original handle in place.


The next bit of natural progression for me was to get the cylinder made, and a nice big lump of cast iron was supplied. In fact, enough to make two, if I don't get the first one right.


It was mounted up in the chuck, the free end gently centre drilled and a rotating centre was used as support. Then it was just a matter of cutting it down to size.




By taking things steady and slowly, the outer surfaces were brought down to exact sizes and lengths.
The machined up bit was then held in the chuck while the rest was parted off.
But due to an unfortunate accident, where I couldn't take the weight of the piece that was being parted off correctly, it trapped my favourite parting off tool and snapped the end off. Back onto fleabay to find a replacement. You win some, you lose some. I still have the left hand version of the same tool, so I will be OK until I find another.

Normally for taking off such a large lump I would have used my power hacksaw, so it was my own fault for trying to do things too fast.



As you can see by comparing it to the digivern, it is a rather large cylinder.
I checked to see if I had enough length on my boring bar to get the bore done, and it looks like I will get away with it, if I take it steady.

The 4" long lump at the side was the piece that trapped my parting tool and broke it, all because I couldn't support the weight.




Away we go, my way of boring a cylinder.


First off, I am using a four jaw self centring chuck, not a 4 jaw independent. I find they are a little more accurate than a normal 3 jaw.

One of the first things you will notice are the brass shim protectors, you could use cut up drinks cans instead. Cast iron, although fairly hard to penetrate can have the surface bruised very easily by unprotected jaws, these are used to help prevent that. There is no need to go to white knuckle tightening up, they grip rather well without going that far.
The flange was faced to correct thickness.




By using different sized drills, I gradually removed most of the material to come out of the bore.
I left 3/16" to bore out. You can go much closer than that, but I like to use the run up to final size to gauge how the bar is cutting. Writing down the cut put on and seeing if it matches with the amount taken off.




The boring tool was set up in it's holder. Making sure that it will go all the way thru the part. I also set up the saddle stop so that it works just after the tool has gone all the way thru.
This is really sticking out a bit more than normal, but this is a 16mm diameter tool and I have found that they are more rigid than a normal steel one of the same size, so if normal cutting pressures are kept low (no big depth cuts) then everything will be fine.




So the sleeve was remounted into the chuck, but using a slightly different method.
The flange goes fully up to the jaws, to stop the sleeve being pushed inside the chuck as I put a new cut on. Secondly, the protectors are still used, but the jaws are only tightened just enough to stop the part spinning in the chuck.
If you tighten up too much, the outside walls will be pressed inwards and when the boring bar takes it's cut, it will be off the metal that has been pushed inwards and you will find that when the chuck pressure is taken off, you will end up with a triangular(if using a 3 jaw) or square (if using a 4jaw) shaped hole, not perfectly round. I hope you understood that.
If possible, I always try to bore thin wall items with the bored part being outside of the chuck jaws.

Anyway, back to cutting out this hole. I rough cut out at 0.025" cuts for the first few, until I got within say 15 thou of required hole size. Then remove the material until it leaves about 0,002" to be removed. The closer you get to size, the finer and slower the feed you use.
I do the final cut, measure that it is either spot on or very close to size, then using a very fine feed, take another half dozen cuts with no more cut on at all, just using the same setting as the final one used to get down to size. This is to take off any material that wasn't cut because of the tool flexing as it went down the bore.
All this lot took well over an hour, but hey, the job isn't going to get up and run away, so time shouldn't enter into the equation, other than the longer you take on it, usually the better results you get.




The bore, measured at either end was exactly the same, one thou oversize, so no tapered bore. I suppose I should have used my deep bore gauge as I was doing the job, but I couldn't be bothered to unpack my instrument cupboard to get to it.
The surface finish was smooth as silk. I love working with cast iron for that very reason, you can get fabulous smooth finishes on it.



The last pic shows the sleeve sitting on a bar of metal. Cast iron again, and that will end up as the piston. A job for next time.

Actually, the instructions that came with the engine suggests honing the bore at this time. Personally I think that is the wrong way to go on an engine such as this, so after the piston is brought down to size, it will be lapped in with the cylinder bore, that will give an even smoother and less friction of fit than honing could achieve.

John

Bogstandard:
I will most probably spend more time on getting a good finish between the bore and piston than I have spent making the two parts.

To me, they are the most important part of an engine, and getting it right first time will eliminate any queries about them when it comes to get the engine running, if there are any problems.


Because there was so little spare length to hold the billet in the chuck (3/16") to complete the piston by normal methods, I am using a feature that is normally put in last to actually help me make the part. When you see the finished article, you will see why I went down this route.
First off, I did a fine face off on the end, then drilled and tapped a 3/16" x 40 tpi thread in it (normally the last bit to do). This is going to be the main datum for the whole machining exercise.




I now went over the whole billet, rough skinning it down to within about 0.050" of finished size all over.

This is removing metal from the other end of the billet.



The O.D. was taken down in two stages.



The final part was to remove the bulk from the inside.



So this is what I ended up with. I now need to be able to hold this fairly rigid while I bring everything down to size.
Time to make a mandrel.




Using a piece of bar end, I turned a spigot sticking out on the end and then faced the end off smooth. The spigot was then threaded 3/16" x 40 tpi.



The part was then screwed on tight onto the spigot screw and faced end.




I need to get the heaviest of the machining done first, as the screw will be gradually shortened to a couple of threads by the time the centre is bored out.

First off, the piston was brought down to exact length.




Followed very gently by removing all the inside of the piston by boring. You can just see at the bottom of the hole where the screw has been shortened by the boring exercise.




The OD of the piston was then brought down until it just fitted inside the bore, just a nice push fit.




You can now see how much metal was removed, I suppose because the piston needs to be very light just so that friction and reciprocating forces don't get too high.

If I had tried to hold this with a normal chuck, I would imagine it would have collapsed.



My mic said I had 0.0006" clearance (about 0.015mm). That will be spot on for when I start to lap the piston to bore. Hopefully I will end up with about 1 thou clearance (0.025mm).




You can also see that the bar end will act as a perfect piston holding handle for doing the lapping with.


Now the dirty work begins with the lapping.

Almost everything after that is straightforwards machining and sticking or silver soldering together.


With regards to showing lapping etc. The US lads have a definite advantage over me in that department. They have retail access to very cheap soft laps, whereas in the UK, although most probably available, they will be neither as cheap or accessible as the US ones are.

So I personally have to use old and trusted methods for achieving what is required.

I will just explain something that I haven't shown.

When the unlapped piston was pushed thru the bore, I noticed that about 2/3rds the way up from the end (opposite to the flange end of the cylinder) I noticed there was a slight binding up between the two parts. If I had had not been so lazy and used my bore gauge from the start, rather than using an internal mic at each end, I would have picked this up and taken a few more non feed cuts when I was boring the cylinder. As it was, I used my bore hone to straighten things out. There was most probably only about a tenth to be removed, and it only took a couple of minutes to hone it out.

All operations were done on the slowest setting my lathe will go, 65 RPM.

After that, it was just a matter of starting out with a bit of diamond paste gently spread onto the surface of the piston. I wouldn't recommend using diamond if it was a non ferrous bore or piston, as it tends to permanently embed itself into the soft metal surface, so if it isn't all completely removed, it will carry on wearing away the bore as the engine is running. After a good wash down with thinners, I used a commercial chrome polish, cleaned down again, then finished off with rouge paste.
These operations took just over an hour, gently rotating the sleeve up and down the over the piston in a sort of figure of eight movement until things start slackening off and getting easier with each different compound. I recharged each compound about 3 or 4 times, when it started to get filthy loaded with cast iron sludge. You have to make sure that the whole inner surface of the bore is lapped to the outer surface of the piston.
In the beginning, the sleeve had to be held fairly tight to stop it rotating with the piston, but as things went on, it got easier to hold. The final lap was actually done with just one finger pressure moving the sleeve up and down.




I tried to get a flash shot showing the semi chrome finish on both the bore and piston, but failed miserably. Because I am scared of boogie men, I won't go out to the shop in the dark to take another picture.
Anyway, another take my word for it, they were s-m-o-o-t-h as silk.

In fact, just by gently sucking and blowing on the flanged end of the cylinder, the piston went up and down in the bore.



I have taken a shot of the bits and bobs that I used for the exercise, and I will try to explain how the hone works.

On the left is my commercial cylinder hone, designed for things like brake cylinders and small i/c bores. I paid less than 20 squid for this off the net, from a motor factors. If you buy one from a model engineering supplier, they will cost you double that, for exactly the same thing (or even less contents).

This one will work with bores from around 3/4" up to about 3.5". You can buy extra stones, both harder and softer grades in different lengths, to cater for different materials and depth of bore. I have found the ones supplied have done a great job on all the different bores I have honed.

The way they work is that when the stones are fed into the bore, they lie flat against the inner surface, and by gently rotating in the bore, and moving it in and out, as I did my lapping, it will gradually make the bore perfectly parallel and round. In use, you keep it well lubricated, I use my general purpose hydraulic oil that I use on my machine for the gearboxes and local lubrication, and by adjusting a thumb screw at the back of the spring, you can make the stones cut harder or softer. The closer you get to perfect, the softer you have the setting.

These hones are not really for getting a very smooth bore, but they will do if adjusted correctly, as I said, they are used for getting things straightened out. You will find that after use, if you have followed the movement regime I mentioned earlier, there are minute scratches in the bore face. As the engine is running in, oil will get trapped in these tiny scratches and help prevent the piston seizing in the bore as the two bed in together over time. Eventually the scratches will be worn away and you will end up with highly polished bore and piston.

From certain model engineer suppliers, you can buy casting kits that when made up will do the same thing for the outside of the pistons, they are called external hones.

The lapping I have done does away with this engine running in period, and the engine should be able to get up to full speed from the start.

On the right hand side of the pic are the three compounds I used for lapping. The green stuff at the back is my own diamond lapping paste that I made up a few years ago, and it is used to get most of the sleeve to piston undulations removed. Next one down is a commercial chrome polish. This is for getting things started to be really smooth, then followed by the jewellers rouge which imparts a nice polish to both surfaces.

People use all sorts of different compounds for lapping, these are just the basic ones I use. If I was doing a non ferrous bore or piston, I would actually use an aluminium oxide grinding paste (the stuff used for grinding in valves on a car) instead of the diamond paste. The ali oxide actually breaks down into a harmless sludge during the lapping process, so is easily washed off, and causing no further wear to the parts.




So that is the cylinder bore and piston finished, except for drilling a few mounting holes. That means I can get back onto making things.

So you have to imagine what I look like now, hands filthy, embedded CI dust in the pores, the front of my white t-shirt covered in the same stuff, and a ring of dirty oil around my lips, from sucking the piston in and out



I need to find where to bore the hole so that when the sleeve is fitted, not only is it parallel to the base but also the correct height from it. The conrod has a fairly wide sweep up and down, and if those two are not correct, within reason, the conrod will catch the edge of the cylinder.
So using an old fitters trick, I filled the cast hole up with a bit of sheet lead tapped into position so that it grabs the inside of the hole. There are many other methods that can be used, bits of wood etc, but I find that this way suits me.




By using a few hand tools, and a copy of John Stevensons precision oddleg scribing calipers, I got the centre hole spotted to within a couple of thou. When working with castings such as this, that is perfectly good enough.
It took the opportunity to mark up where the faced area needs to be cut to.




Using my coaxial thingybob I soon had the centre found and the table zeroed up and locked.




I was soon boring thru both the top and bottom faces.
I did find out the the boring head actually removes double the amount that is set, the normal thing on a lathe, but no problems keeping things accurate, it is marked up in half thous.




It was soon up to a position where the sleeve could be gently pushed thru both top and bottom faces. I should have no trouble sealing the sleeve into the hopper.
There was a problem with the boring head, I had made the key handle much too small, and it hurt my fingers as I took the facing cuts. Because of this, I actually forgot to take any pics of the facing exercise.
I will soon be able to knock up a more comfortable key, and maybe another time I can show it facing off.




But it actually did a superb job, totally square to the bore, but I did have to go to 0.025" (0.6mm) deep to clean off the casting face so that the sleeve flange sat flat all the way around.




The two parts pushed together. I'm very happy with the results.




I am now in the process of recentring everything up, because if I now make the cylinder head and stick it onto these two bits, I can drill all the holding bolts at the same time rather than having to spot thru from a previously drilled cylinder head, and maybe make a mistake.




John

Stuart:
Nice to see your builds John

I always find a new wrinkle to a machine problem that will come up in the future


I like many other I look forwards to many more


Stuart

lazylathe:
I think i am up to date now John!
More great info to be gleaned from that post.

Looking forward to the upcoming ones too!

Andrew

Navigation

[0] Message Index

[#] Next page

[*] Previous page