Making a piston valve engine from mainly junk materials

[bogstandard]

Before we start with the next thrilling installment, I made a mistake on the last post about the height of the bearing blocks and if you had any that were low you should shim them up. I had forgotten that we have adjustment to cater for this later on, so you can in fact reduce the height of the others to match. The easiest way is to put a rod thru them all and flat down using abrasive paper and a flat plate, no not dinner or side but something like a piece of glass.
Tonights offering is the baseplate. I am making mine out of 2mm brass, the same as the top plate, and using standups underneath to give clearance for the crankwebs. This method is a bit flimsy but it is designed to bolt to the boiler and engine support plate, so making it totally rigid. If you wanted a free standing engine you could use thick aluminium plate but a minimum of 12mm thick, you would have to counterbore underneath to set all the mounting screws in but it should not be a problem.
First off is a sketch, on here just follow the measurements to make the plate, but please be aware of the datum lines, one is the longtitudinal (thats a big word for a monday night) centre line, the other is one of the short sides. All measurements are from these two datums.
All the photos should be self explanatory, except for the one simulating an engine build up. The rods on this are not the right length and will in fact be a bit longer, the feet under the plate are approx what it will be like, they have to raise the plate because that cranks have to protrude thru the plate.
Also on the third pic of the finished plate you will notice the corners of the cutouts are rounded off. I used a 4.5mm cutter but I wouldn't go any larger than 5mm otherwise the crankwebs might foul on the corners.

Next will be the crankshaft.

John

[Eddy Matthews]

Another superb installment John, and I'm still feeling that this isn't totally beyond my capabilities which is amazing!

I realise this is jumping ahead a great deal, but I do hope you'll continue on to include making a boiler, burner, condensor etc etc, so that we eventually end up with a complete steamplant? And maybe even consider a short discussion on any modifications that would be needed to convert the engine to a horizontal/diagonal type more in keeping with the majority of paddlers?

I've already had words with one of my clubmates so I can get some practice in on his lathe later in the year - We both have too many other things on right now do do anything immediately, but he's happy to let me have a go and guide me through the basics.... If that goes well, I can see the purchase of a second-hand lathe could well be on the cards for next year damn you!

[bogstandard]

Hi Eddy,
With regards to making a boiler, I have built a few in my time, even gas fired ones using the same technology as they use nowadays, but to cut a long story short I don't fancy starting to make boilers again when there are perfectly good boilers to be had at very reasonable prices from the professionals. Besides the fact I have seen some boilers that people have tried to make in their garden sheds using small gas plumbers blowlamps, I am not saying that it can't be done, and again I have seen some great ones, but the thought of me giving free reign to someone to attempt to make a boiler to my specifications, I'm very sorry but NO, I just couldn't bear the thought if someone was injured. Leave it to the professionals. I saw a chap once pressure testing the thing he called a boiler, he had it weighted down with a brick in a bucket of water and it was directly connected to his compressor, he was standing over it to see if there were any bubbles, you couldn't see my a*** for dust.

I am already looking at turning one of my engines into a horizontal, but it looks like it will be a bit more difficult than my oscillators, by the way I have to stop this build this weekend for a while, a gentleman has  commissioned me to convert one of my engines into a horizontal for him, so I expect to restart early next week.
The main problem is the pipework, if I can get it compact enough I will give it a go. I don't think it will look very pretty, in fact downright ugly (just like the ones we are building here), but as I said at the start of this project, it is a design and make as I go along and I don't even consider esthetics, just make it simple and make it work, that even a beginner has a chance of completing. In fact it might be easier to design a purpose made horizontal, I will get some fag packets together and see what materializes.

With regards to a lathe, don't blame me, it was your suggestion in the first place. But for the cost of a small lathe and all the related bits is less than the cost of a moderate kit, it does open up a whole new world in  the term 'modelling'.

John

[bogstandard]

Tonights offering is all to do with the crankshaft area.
As usual there is a sketch for items to be made. The flywheel can be made as is or like I have done, put a recess in each side for cosmetic effect.
There are two drawings for the crankwebs, one semi balanced and the other a lot easier to make but not as nice cosmetically.
Pic one is showing how I lap in the bearing blocks. The rod is about 1 1/2 times the length of the bedplate and is the same material as will be used for the crankshaft centre rods, 5mm stainless or silver steel. At this stage the rod is very tight in the bearings. Put a little bit of metal polish or T-Cut in the lubricator pots, hold onto the plate and turn the battery powered drill/screwdriver on (I wouldn't recommend an electric drill, too fast unless you have speed control).
Hold tight to the plate in the beginning, it will try to spin round with the shaft, if too tight hold plate in a vice until the parts start to rotate a bit freer.
As it starts to free off, slide the plate and blocks up and down the shaft. After about 10 minutes of this you should find that the parts now move a lot freer. Clean off everything very well to get rid of all abrasive. Put some 3 in 1 oil or something as thin into the oil cups and spin the shaft, it should be nice and smooth. This shafting can be used for making the crankshaft rods, we have only taken microns off the OD.
Pic two is showing the rough blanks for cranks and flywheel and the scrapmans bar end that they came from.
Three is the blanks ready for precision drilling. The distance between the crankpin (5mm) and the big end pin (4mm) is critical and should be drilled using machine cross slide for the setting. The distance isn't critical, but they must ALL be the same.
Pic four shows what you should be aiming for, all ten of my discs slide easily onto the two different diameter rods, I must stress again THEY HAVE TO BE EXACT for this design crankshaft to work. The 2.5mm hole is not critical.
Also shown is what the finished semi balanced crankweb will be like. I should get them finished tomorrow.

Next hopefully is building up the crankshaft.

John

[Eddy Matthews]

hmmm... The first bit that has really worried me!

It looks like a fraction off with the drilling and either it won't fit together at all, or it will lock up as tight as a ducks whatsit!

Would it be better to drill all the holes in one solid block and then part it off into the seperate bits that are needed?

[bogstandard]

At last, now we are getting there, you are starting to think like a model engineer. Problem solving is about 90% of the job when tackling something like this. It should be "How am I going to make it?" for every part that is not self explanatory. This is the satisfaction I get from making things out of all sorts of materials.
The only problem with your idea is getting the hole to drill perfectly straight when going so deep. Its about time people started to worry about making things shown here and ask the question, I have already done it so I can supply the answer, if you don't have the same machinery that I have,  I can come up with another way for it to be done. There are lots of ways to solve most of the problems. Making a little jig is the usual way to do it.
The easy way is to make a jig out of steel (see attached sketch) and follow the instructions.
The way I do it is to set stops for the part to sit against in the vice, and after the first one as long as you do not move any machine settings it is just a matter of dropping the next piece in and drill and so on, I drilled all ten of mine after the initial setup in less than 15 minutes (I deburred each part after it was drilled, and blew away the swarf before the next one). The small hole is drilled later, that isn't critical, its only a pivot point for the metal to distort around.
I think from now on for difficult bits I will take a photo of my setup, but most of the difficult bits have now been done. Ah well, we'll get it right one day.
By the way Eddy, I hope I didn't offend you in any way over my rather terse comments about boiler building, it was just my views being expressed, it was nothing personal.

John

[Eddy Matthews]

At last, now we are getting there, you are starting to think like a model engineer. Problem solving is about 90% of the job when tackling something like this. It should be "How am I going to make it?" for every part that is not self explanatory. This is the satisfaction I get from making things out of all sorts of materials.
The only problem with your idea is getting the hole to drill perfectly straight when going so deep.

Believe it or not, I did immediately think of the problem of drilling so deep that the drill bit wandered, but it seemed like a possible solution....  Obviously your jig idea removes that problem.

I have to admit that it's the first time I've ever been told that I'm "Thinking like an engineer"! - That has just made my day!

By the way Eddy, I hope I didn't offend you in any way over my rather terse comments about boiler building, it was just my views being expressed, it was nothing personal.

John

Not in the slightest John - I fully understand your reasoning. I still feel it's a shame that we won't end up with a totally self-made steamplant, rather than just an engine, but I can still accept the technicalities (sp?) and why you feel that way.

I'll just have to contact Sandy when the time comes and spend some of my hard earned with him

[bogstandard]

I went into the workshop this morning hoping to finish off the crankwebs and shafts, then a thought occurred to me, I hadn't even considered one of the major parts - THE DREADED ECCENTRIC - no, not me, but a little thing thats puts the dread into making small steam engines, and they are so simple to produce if gone thru logically. I have already done a bit of preliminary design work on the piston valve block so I know what lift is required.
Study the sketch, a bit offputting isn't it?
We are going to split it down into easy parts.
Start by turning the bar down to 18mm and face the end, put the 4mm wide groove into it, 1mm from the end. Measure 10.5mm from the faced end and part off at this point. Repeat the procedure. Remount the cutoff piece into the chuck with the groove inside the jaws, Face up until you have a length of 10mm (no longer, if anything go slightly under), you should now have what is shown on pic 1.
There are a few different ways to put the eccentric hole thru, but this one is bob on accurate. If you refer to pic 2 it shows my bits of metal mounted in a chuck of a rotary table and a DTI running around the edge. I use this setup because it is easier for me with my slight infirmity. As I said before, If you are doing this with a vertical slide, imagine the DTI in your lathe chuck and the part to be drilled in your vertical slide vice. Basically what you have to do is centralize the workpiece to the chuck.
Once this is done, just offset the workpiece by 3mm using your crosslide or vertical slide, put the drill in the lathe chuck and drill thru. Eccentric conquered. You should end up with bits like shown in pic 3, while I had the workpiece set up I took the opportunity to mark the end with the groove to help with setting up the engine.
Next, remember a few posts back where we set up in the lathe for putting on the anti friction bosses on the crankshaft blocks. Well the next operation is almost the same but a little more precise.
Take a piece of 5mm rod and mount it in the lathe and drill and tap the end 3mm. Move the rod back in the chuck until about 8mm is protruding and give it a good tighten. Slip on the eccentric with the groove towards the chuck and screw in a screw and washer to grip the part against the chuck jaws, see picture 4. By the way the 4 jaw chuck I am using here is not a 4 jaw independent but a 4 jaw self centring, same as your 3 jaw but with four, I find them a lot more accurate and more versatile.
Now take very fine cuts (max 0.3mm) for a distance of 4mm along the workpiece. Keep taking fine cuts until a boss diameter of 12mm is reached (not critical).
Take off eccentric and drill and tap the 3mm hole at the position as marked on the sketch, it can be anywhere around the boss.
You should now have eccentrics that look like the ones in pic 5 (mine have yet to be drilled and tapped).
Now wasn't that easy campers, next week we will be making a 24 lobe camshaft for an aircraft engine.
Thats it now until next week, I have some other work to do.

John

[gilessim]

Hi there John, thanks to you (on cnc forum),I resolved the problem of drilling a series of tiny holes ,using tiny (0.9mm) centre drills to spot first, worked a treat!. I got them from some polish guys who set up a market stall in a layby near my house here near Florence,I think they must halfinch the stuff from where they work in Poland! ,I also got a nice 5" 4 jaw ind. chuck new!,and 10 bars,8-10 mm round and square of good hss, 10 of the centre drills all for 50 euros! (about £30),by the way the chuck fitted straight on the boss on my lathe!.If you look on the new people section under engines on this forum I put up a photo of an engine I'm working on ,you'll see that the heads on the cylinders have 4 holes around them ,I did them ,after some thought, hole by hole on the mill ,but as Eddy suggested(but some time ago) all from the same piece,and then parted them off, as they are only 4mm or so thick I thought it would be ok ,but the drill did wander a touch on one ,luckily not enough to be seen with the pan head allen screw in it, but still annoying!.I have an idea for a v twin overhead valve engine I'd like to make,maybe I'll start a thread!...thanks and well done on your engine and very well explained!.I'm of the fag packet school like you (sometimes I don't even do a sketch! ,I'm too lazy!)I think these forums are great ! lets keep up the good work!...P.S. I'm with you on the fact that dogs can be a great help with these things sometimes ,they have a more relaxed point of veiw!....Giles

[bogstandard]

Hi Giles,
Nice looking engine you are making there. I like the look of what the chap who does the plans has to offer, they are very artistic and modern looking. Might even have a go at one myself, a bit of light relief.
Even though this is not an engineering site, I find the people on here very knowledgeable and willing to help as much as they can, When I was looking at making this engine, I didn't fully understand the working geometry of the piston valve setup, but I asked the question and everything was explained very easily to me.
I know what you mean about roadside markets on the continent, I was driving thru Czechoslovakia a couple of years ago and there was a huge market at the side of a motorway turnoff, all makeshift like a shanty town, but you could get almost anything there, from a box of matches to a car engine, all brand new (I don't suppose there is much call for second hand matches, but you never know).
Keep up the good work and if you need anything, just ask, and remember we all cannot know everything, and there is no such thing as a silly question.

John

[crash93]

Just out of interest which is the cnc forum you look on?  Peter

[bogstandard]

Hi Crash,
Even though I don't have CNC I found this site very helpful, v-e-e-e-ry technical in places. This is the one we were talking about.
http://www.cnczone.com/

John

[crash93]

Thanks for that I have regested , seem to be a bit USA based ,but looks good. Peter

[bogstandard]

Here is the reason for not posting the last few days.
A gentleman commissioned me to convert one of my uprights to a paddle engine.
Rather than rushing as I did the prototype, plus no need to convert back, by changing the position of the large gear bearing I was able to reduce the overall length of the bedplate by 20mm, giving a much more aesthetically pleasing engine.
Will be posting again on the piston valve maybe tomorrow or definite thursday.

John

[bogstandard]

Tonights little offering is showing how to finish off the crankwebs, showing an easy way to machine the webs to size all in one go rather than separately.
First off a bit of milling criteria. Due to the normal types of machines, either lathes with a vertical slide or the general purpose milling machines (like mine and 99% of most people) you should NOT be doing any CLIMB MILLING unless you really want a new facial feature that looks decidedly like the job you have in your vice, and maybe the cutter as well.
You only do a cut one way, CUT, rewind back, put on new feed, CUT, slower but safer.
DOWN CUT or CLIMB MILLING should only be done by experts with the correct type of machinery, and this is one of the main reasons amateurs like ourselves (and I have done it) have ruined a perfectly good job because we put the cut on the wrong way.
You should only be doing CONVENTIONAL or UP CUT Milling. The first pic is a copy out of a machine manual that explains it very well, if you can't understand it, just ask.
The second pic shows all my crankwebs mounted in the vice. The cunning bit is the bits of brass you see there. We are going to use the accurately drilled holes to our advantage.
There are two different sizes, 5mm and 4mm. If we get the centres at the same height it will be just an easy machining job. To do this by the way, when your vice jaws are tightened together they should be in line with each other and also the tops of the jaws need to run parallel with the end of the cutter in your chuck. Whenever I invest in a new vice the first thing I do is grind the tops of the jaws parallel to the base, for just this sort of job.
If we subtract 4 from 5 this gives us 1, half it and we get 0.5mm. Now search high and low to get some material to use as shims, anything solid, metal, plasticard, even shim stock if need be, of 0.5mm thick.
Put the job into the vice like shown on the pic and slip the shims under either side of the 4mm rod, push down and tighten the jaws. This now ensures that all machining is now parallel to the hole centres. This trick can be used anywhere you want to machine parallel to two hole centres.
You will also notice I am using a back stop again, this allows me to reposition the job after the first side is cut and use the same settings again, it all saves time, and they are so easy to make. I have even superglued a piece of metal to the inside of my vice jaws to act as a back stop when the diameter of my backstop rod was too large.
Pic 3 shows the first side machined, flip over and machine the other side, using the same setup.
Pic 4 is the finished job. Ten crankwebs machined in less than 30 mins.
Pic 5 uses the same setup for using a slitting saw to put the slot in, but two things here, after you have tightened up, remove the rods otherwise you end up with half round section, and don't try to do more than one at a time, it is by leaving the rods in for strength we can get away with it for milling the webs.
You don't have to use a slitting saw. a bandsaw or hacksaw will do the job, it isn't critical, but my way makes the bits look pretty.
Tomorrow we will get all the crankshaft completed and we will see if my calculations are right and the damned thing rotates.

John