Making a piston valve engine from mainly junk materials

[bogstandard]

Hi All, back again. But not getting any feedback to see if anyone is still interested.
Who was the idiot who suggested building a composite crankshaft made up of thirteen separate parts (5 shafts, four webs and four cap screws).
Assembled it all, like trying to juggle with half a dozen kittens. Tightened it all up and the damned thing rotated perfectly, no fiddling, filing, nothing. So assembled the second one, exactly the same. So nothing else to do but carry on.
I knew something would go right eventually.
The sketch shows the different shafts required for the crankshaft, do not go over length on any of these, if anything slightly shorter (approx 0.1mm). It doesn't matter on the 60mm long one, this can be any length you like as it is the one that connects to your prop shaft.
When built there should be no shafting protruding anywhere into free space on the webs. The flats on the shafts are to allow grub screws to be fitted and the bruising to the shaft that they cause does not interfere with disassembly of the parts because the damage is on the flat rather than on the periphery of the shaft.
Photo 1 shows another way for machining the webs. I made a small shaft with about 5mm either end protruding out of the webs, these sticky out bits were turned down to 4mm (the same as the smaller shaft) and extended slightly inside the web. This method cannot be used where the shaft has to be removed for machining (cutting the slot) because the vice jaws prevent it from sliding out.
Second pic is showing all the bits for crankshaft assembly (my flats are not machined yet).
Pic 3 is the built up crankshafts, looking like they are ready for business.
My next job will be to make the bits to join the top and bottom together, namely the connecting rods, their screws and the support columns. Have got a bit of work to do on this yet as I need to keep the height to a minimum, so it will be conrods first then make columns to fit.

John

[Eddy Matthews]

Well I'm still following everything John. Not much to say as everything has been so well explained...

The assembled crank looks like a work of art - My hat is off to you sir!

The only thing that would concern me is assembling all those tiny bits with my size 19 hands! I wonder if I can talk my wife into getting interested in making steam engines, then I could get her to put all the fiddly stuff together!

[derekwarner_decoy]

OK, OK....I am bloody 22 thousand miles away....but yes... VERY interested John  :bow

When I look at the electronic pages of steam engines by Daniel Bourard I see crank positioning referenced as degrees, minutes & seconds & naturally the same for the eccentrics [No I did not mean Sandy]
JMC [even after spending 610 EURO] will not release any working detail on this issue

So is this positioning a BLACK art or what  & how do you achieve it ? :rant  

[bogstandard]

Eddy,
Could you imagine trying to make a solid crankshaft. I can do it but I don't think the likes of beginners stand a chance, that is why I designed it this way, a few simple components making one complicated one.
I see you have fairly small hands then, mine drag along the floor they are that big.

Derek,
I think you are confusing your very well made and complicated slide valve engine with this simple piston valve design. The timing is almost exactly like an oscillator where each crank is at 90 deg apart (this gives it it's self starting properties), as for the port timing, Sandy explained this to me on a previous post about piston valve timing and basically the ports start to open 90 deg before the piston crank, at least I think that is what I mean. I wouldn't even know where to start on timing yours, maybe Sandy can help.

Did some prelim work this afternoon on the conrods, made a couple out of plasticard to get the right stroke so hopefully tomorrow top and bottom will be connected.

John

[Eddy Matthews]

I used to work for an angine reconditioning company John, and operated their offest throw crank grinder, so I can imagine some of the things involved with making a crank in one piece - I don't think we'll go down that road!!

[sandy_ACS]

   

Hi All,

Excellent job John.... I think you will end up with a great little engine.

This method of crankshaft construction is quite common on small model engines, Saito use a similar system, as do I on some of my engines.
It certainly is easier, cheaper and a lot quicker than turning the darn thing from a solid billit, however, it does have limitations.

The other point about this type of construction is the more simple method of making the crankshaft bearing blocks, which can, as yours are, be simple bored blocks. A fully turned crankshaft would need to be mounted in split bearing housings, possibly with split shell bearings as well, which are much more complicated to make and accuracy levels necessary are that much tighter.
With this method, it is also possible to use ball races on all bearings, which would not be possible with a solid turned shaft, at least not for the centre bearing/s.
On larger engines it would be possible to use split roller bearings on the inner journals, however, for these small engines such items are not readily available. (at least not at a practical cost)

Valve timing..... The inlet port should begin to open when the piston is at top dead centre, or just leaving it.... with a simple piston valve, as John is using, this means that the crown (high point) of the eccentric must be ahead of (lead) it's associated crank pin by 90 degrees. This angle is quite critical and therefore must be accurately set.

The crank timing of 90 degrees between cylinders, which is not overly critical, +/- a couple of degrees would not cause any real problems, has nothing to do with the valve timing, this is, as you say, to enable the engine to be self starting.... however, this is only true when using double acting cylinders. (You would need 4 single acting cylinders, each set at 90 derees to each other, to achieve the same effect)

Derek..... your JMC also has 90 degree crank spacing, however, since it also uses Stephenson link valve gear with 2 eccentrics per cylinder and probably also employs some valve lap and/or lead, then the eccentric angles will not be at 90 degrees, but would be set at some angle as dictated by the valve gear type and the lap/lead requirements.

The next instalment of Steam and Steam engines will be dealing with just this subject, so hang on just a bit longer and you will be able to read all about it.

Ok, that is my two pence worth.

Keep up the good work John.

Best Regards.

Sandy. :vacat  :computer  

[bogstandard]

Sandy,
Many thanks for your words of wisdom, you can explain these technical bits a lot better than myself.
As I said at the beginning of this article, everything on here should be able to be made by a beginner so there would be no complicated bits to make, just be fairly accurate.
I am on a learning curve on this one, never having built a piston valve one before, I don't have access to any examples of what other people have designed and made, I just look at a problem, see what may work and make it, luckily up to now everything has worked out 100%, just by using good engineering practices. I have yet to fall on my a**e, but one day it will come, so I will take one step back, one step sideways and carry on. There are usually a lot more ways to solve a problem.
So in maybe a weeks time I will be trying to set the steam ports to the correct timing, its easy making the bits, it is getting them to work in unison is the problem., so your comments might be called upon again.

Thanks again

John

[bogstandard]

Didn't get as far as I wanted today, the great one got me scrubbed up with a hose and broom and I had to go, dare I mention it, SHOPPING. Aren't supermarkets wonderful, I always wondered where all our food came from.
Anyway, managed to get top and bottom joined together, so I took a couple of pics to show the development. The conrods are still not finished, the front one is what I expect it will look like, the rear is just the basic building block. And the thing still turns over, a bit tight, but that is easily remedied with a file and a hammer plus a bit of oil. I rushed these conrods so I think one of the holes isn't quite parallel, but as these are tryouts I am not worried.
You will notice a couple of raindrops in the background, twenty seconds later we were into a full thunderstorm. The dog can go for a walk by itself tonight.

Clean John

[bogstandard]

Hi All

Got the top and bottom joined with the right bits now.
First the sketch. This shows the dimension for the column length. As stated in a previous post about the thickness of plate used for the block support plate. This dimension is for a plate with a thickness of 2mm, if the plate you use is thicker then subtract the difference from this length, if it is thinner then add the difference to the length. If you don't do this you will end up with a mechanical lock on the engine. The columns can be any diameter from 6mm to 10mm, it doesn't matter, but if you use aluminium for the columns I would go for 8mm and above.
Also shown are the dimensions of the little end pins.
The conrods are shown as a raw shape, the engine will run with them like this, but you can hack to your hearts content as long as you don't get too close to the bearing holes and don't reduce the diameter to less than 4.5mm, you can have it square or round, maybe profile it like a car conrod, drill holes thru them, it doesn't matter, let your imagination run wild.
The first picture shows how I developed the conrods, starting left to right, a bit of plasticard, just to see if I was in the ballpark, then a couple of rough, and I mean rough made to check for correct length and dimensions. The next pair are the same except one was profiled to see what it would look like, these were correct dimensionally. The last are the finished rods and pins.
The second pic shows the engine with the new rods, I think it makes it look very beefy and powerful, what do you think? Also shown is a ruler against the engine, from the wrong angle, but it shows that the engine is about 4.5" high and it is the same length and 2"wide, not minute by any means but it should shove a boat of 4ft or over along quite easily. Sorry about that I have just reverted back to imperial, damn this government.
Now a question from me. Is anyone building this engine as I go along? Or as I suspect are you hanging round like vultures to see if I snuff it before I finish, or make one holy cock up of the whole thing so we end up with an engine that won't run.
Oh! ye of little faith, this engine will be finished, even if the dog has to do it, and if it won't run I can always put an electric motor on it (hidden in a box behind the engine), so it looks like it runs.
Anyway, joking aside, I have a question to ask as to what type of speed control and reverse you want on this engine. Basically there are two that I will consider, the first is the usual type that is a rotating disc. These are easy to make except for the disc itself, they have to have fairly accurate transfer grooves machined on them and do require a rotary table, I know you can use straight transfer grooves, but I have never really found them satisfactory, also these controls tend to leak steam even though they are finely bedded in.
The second is a control block where everything is sealed inside and doesn't leak, but it does require the use of a small o-ring to seal the output shaft (I would consider supplying the o-ring if you sent an SAE. UK only), and the machining has to be fairly precise, but if you have got this far in the build you shouldn't have any trouble making it with the experience you have gained already.
The reason I have to ask is that I will be designing the piston valve area this next week and it all depends on which one is required determines where I should put the inlet/outlet flanges on the blocks.
If you don't give feedback I will be going with the second option.
I won't be posting for about a week while I design the blocks and iron out any problems, but I will keep checking the site to see if there is any feedback. Last chance to vote is wednesday evening.

John

[bogstandard]

***************MODIFICATION***************

I was doing a bit of design work tonight on the piston valve control block, and have decided to change the internal port sizes to allow for easier setting up. This means that the eccentrics will now have a different throw.
So the text for the post concerning the eccentrics has been changed and a modified sketch has been uploaded.
If you have already made them as I have, at least you now know how easy it was, and they get easier the second time around.

John

[Eddy Matthews]

John, is there a reason for the fourth main bearing after the flywheel?

I think the engine would look a lot nicer without that bearing (personal preference), so I'm wondering if it's needed, or if it's just the way you do things?

[derekwarner_decoy]

Hi PD's..... just a few observations from Johns postings...

1) from Sunday  @ 5.35 to Sunday @ 7.51 is not a lot of time to shop for Vegemite, Garlic & a few packets of fags &   & some dog & cat food.... let alone more machining   & complete more of the engine assembly

2) I certainly have been watching each day in awe John  :post &  :kewl

3) Eddy... I acknowledge other engine manufacturers of similar style engines may not have a bearing journal outboard of the fly wheel, however consider the advantages

a) the additional bearing is machined & lapped on true axis with the other engine bearing journals

b) the inclusion was of little time or effort [just one more identical block, a few socket head cap screws & an extra pin]

c) the engine starts out converting up & down motion, then to rotational movement @ the flywheel,.... outboard of the flywheel the physics of nature want to revert the [resultant] loading back to push pull [in both longitudinal & diametrical axis]
d) this additional outboard engine bearing minimises the requirement in the next line of diametrical power transmission [bearing] support

So 10/10 John for bogstandard robust design  ..........

[bogstandard]

Hi Eddy,
The reason as Derek kindly pointed out is an engineering issue.
If the bearing between the crank and the eccentric on the flywheel end had been a lot longer and had a substantial support bearing in there then the fourth bearing could be omitted.
As it stands, the weight of the flywheel is trying to go downwards at an angle and will put a lot of wearing forces onto the bearing, so the fourth bearing ensures the downward moment of the flywheel is reduced, thus causing less wear.
I told you that this engine will be functional rather than pretty, but it will look a lot better when the steam chests go on.

John

[bogstandard]

Hi all,
Got on well today, have got basic plans for steam chests and piston valve. a bit complicated because the block is so narrow, I couldn't use any internal porting, plus I needed to bolt the thing to the block so it took a fair time to get all the holes missing each other. I will knock up a couple of blocks tomorrow and see how it all fairs. In hindsight I would have made the blocks 10mm wider and gone for a 15mm bore, but one of the criteria was that I used as much material from the scrapyard as possible, and this was the largest block I could get out of the sash weights.
Have come across a major problem, as you know I was trying to keep this engine totally metric, but unfortunately my supplier doesn't stock 3mm copper tubing, so we will be using 1/8" instead. When I eventually put up the drawings, if you see any pipework or steam fittings mentioned on there, the relative holes will be marked in imperial with all other measurements in metric. If you only work in metric, 1/8" is equal to 3.2mm tight fit, or 3.3mm sloppy fit, so it would pay to invest in a 1/8" drill.
I have got to get on with this at the moment, so I am designing around a sealed control valve, I have another commission this weekend so I want to get as much of this done as I can, so expect the next instalments sooner than I said.

John

[bogstandard]

Back again,
It's been a bit of a long haul this week, family commitments and all that other unnecessary rubbish like 'can you go and pick the grandson up from school', its only 3 miles, are they incapable of walking any more.
Anyway, managed to get it all designed, but all machining hasn't been done yet. The making of the piston valve control block will be done in two parts, the one here now gets all the holes in the right places, the next post will show what milling has to be done as the sketch would get very complicated if both were put onto the same one.
The sketch shows all hole positions but they are drilled in a sequence to prevent burrs destroying the smooth cylinder walls.
Here goes.
Pic 1 shows the correct size for blocks. Mark one small end and this will be your datum face.
The first op is to drill the 5.5mm hole as shown on the sketch small end, drill 36mm deep (including pointed drill end).
Second op, on the 16mm side you will see two 3mm holes and four tapped 2mm holes. These are all drilled thru to meet the 5.5mm centre hole all except the top one which is drilled 8mm deep. Tap the 2mm holes.
Third op, all the holes on the 18mm side are drilled all the way thru the block. The 3mm holes are the steam control holes and the centres between them need to be exact, so rather than marking out and drilling, use the machine feeds to get this spacing.
The four 2.5mm holes are for mounting the control valve to the main block (how this is mounted will be explained later).
All holes should be deburred but the four ends of the steam control holes should only be deburred very lightly.
The final op is to run a 6mm reamer down the main central hole, this will clean off all the burrs thrown up on the inside and leave a nice clean hole for the piston rod to run in.
Don't worry about the 2mm tapped holes going into the bore, these will be sealed with a screw when the flanges are bolted on and the bit of tapped hole left on the inside should act like a reservoir to hold a bit of oil, and it makes them a lot easier to tap.
Pic 2 shows all the holes required on the block.
Remember a couple of posts back where we made the conrods and I said to use your imagination, well pic 3 shows the rods I have made for my second engine which is going to have a makeover as it is being built to try to spice up this utilitarian design. You will notice that they are a different colour, they are made from aluminium bronze, a lot lighter and stronger than brass (another choice product from the scrapyard, recognizing what it is while rummaging is the problem).

John