A Cracker locomotive

[sbwhart]

Looks good to me to Arnold 

Hope you soon start picking up. 

Stew

[arnoldb]

Ron, Dave, David & Stew; Thanks gents 

  Feeling better, but had some social commitments that detracted from my shop time - but had a load of good fun with some mates.

This engine is taking on a life of it's own  - I've started to deviate so far from the original plans that I'm pretty much making things up as I'm going along now 
Yesterday I turned up the crank-side cylinder head.  There is enough space to add a pack nut if needed, but I decided to first try without one:


The piston followed next.  On all the engines I've built so far, I seem to have made the pistons slightly too large, and they all needed a LOT of running to loosen up, so this time I went for 0.01mm under-size rather than my usual 0.005mm as a test; a new piston is easy enough to make.  Threaded M2 through the centre and then drilled 2mm to half-depth to guide the connecting rod before parting off:


Also made a start on the connecting rod - just some 2mm brazing rod threaded M2 on the end with the tailstock die holder - and a small retaining plate.  I was originally going for a full-blown cross-head, but with the cylinder head being fairly thick, I decided to try the engine as-is.  The bits I ended up with yesterday:


And assembled on the cylinder:


Today I started by drilling the right-hand frame for mounting the cylinder block, and also increased the "bearing" hole for the engine in size; I want to add a bit of packing between the engine and the frame to minimise heat transfer from the engine to the frame, and I don't want the bearing part of the engine in contact with the frame:


Then I started off on the crank - just a bit of phosphor bronze turned down and parted through a bit to thickness with the 3mm centre hole drilled:


On to the rotary table on the mill, and a hole drilled for a press-fit crank pin and whittled away to leave a (to me) pleasing looking web; the original plans don't have a crank web, but it should help to balance the engine a bit as well:


Parted off, and it looks fairly presentable:

The crank is 4mm thick, so I drilled and tapped it for an M3 grub screw through the web - rather than using threads or retaining compound to fit it to the axle.

I was still busting my head on how to retain the cylinder to the block, and had all kinds of weird and wonderful and complicated schemes floating around my noggin...  The block still had to have two holes plugged and that gave me an idea for a simple solution; plug the holes in the block, but leave the plugs sticking out to retain a spring...  I couldn't find suitable spring wire, so I used some more brazing rod; it is actually quite springy - and after a flurry of activity pressing in the crank pin, turning up and pressing in the main bearing and a temporary assembly, I had the ugly duckling together - with the idler shaft and gear acting as an impromptu main shaft/flywheel:



  Looks horrible  , but I had to give it a test 
  Started right up and runs like a champ - without a decent flywheel and at a pressure below what my compressor's gauge can measure
Please take a Dramamine before watching the video 

  Gave it a blow on breath power, and it runs easily; so after a bit of cosmetic work, I think the engine will do 
 , Arnold

[DaveH]

Arnold,

Well that is damn good,

(me thinks your pressure gauge is duff !!)

Really great Arnold, fair zips along, 

 
DaveH

[sbwhart]

Give that man a coconut
 


I like that retaining spring, neat idea. 

Well done

Stew

[Stilldrillin]

         Yeee HAarrrr!   

Nice one Arnold! Well done......

I can see that grin from here ! 

David D

[Rob.Wilson]

Nice going Arnold 


Rob

[modeldozer]

Nicely done.  Like the idea of designing/adapting on the fly.

Abraham

[arnoldb]

Thanks Gents 

Work life keeps interfering with this build  - the week and Saturday was gone before I knew it.

This morning I made the flywheel.  Decided to try out my new small lathe even though it still needs a proper bench made for it and bolting down, so I expected some problems.
The first one was the darn "safety" spring-loaded chuck key; it's a royal pain in the butt, and I stopped and gave it a serious look-at with a big hammer and it fell apart:

Then I assembled just the shaft with the square drive and handle again; left the rest of the crud off.

I'd already cleaned up the outside of a bit of 32mm cast iron on the Myford, but I faced it and made an undercut on the small lathe:

Had quite a bit of bother with chatter; if you look carefully at the sides of the undercut, you'll see.  So definitely no more work on the small lathe till I can get it mounted properly and bolted down...

Finished flywheel with a hole drilled and tapped M3 for a grub screw:


I previously mentioned that I want to make a spacer to insulate the engine from the chassis, so that was next up - from a bit of plastic sawn from an old printer cover:


Then I spent some time making up bits 'n bobs needed to get the chassis to a running condition.  Some "tubing" from brass stock to keep the centre gear  shaft in position, soldered all the axle bearings to the frames with electronics solder (I learnt from my other loco attempts that bearing retainer comes loose if it gets a bit hot on the frame, and a press fit for the bushes shrinks the inner diameter requiring a lot of manual effort with a reamer to open up back to size), a small spacer for the flywheel to prevent interference with the slightly protruding axles, and finally I silver soldered the pinion gear to the main drive shaft and assembled the lot.  View from below:


And standing on a bit of track:


  It runs as well - couldn't test it on a full track, but it does (with the "duff" pressure gauge on zero  ):

  Guess I have to work with some copper next:

I have to think a bit on the boiler; the plans as-is does not use a regulator or safety valve; it relies on the wobbler cylinder getting blown off the port face if the pressure gets too high in the boiler.  The chassis as-is seems extremely lively, so I think I will add a regulator; I like to see slow-running engines.  That means adding a safety valve as well - which is a good idea in any case.  So I have some calculations and a bit of design to do before getting around to the boiler...  Hopefully next weekend.

 , Arnold

[DaveH]

Arnold,
"I stopped and gave it a serious look-at with a big hammer and it fell apart:" Oh Arnold hang thou head in shame

Really coming along very nicely. What a little runner.

Although looking at the video again, I'm not sure if you are not pushing with that flexible tube.

As usual a great bit of posting, nicely photographed.

Great stuff Arnold.
 
DaveH

[arnoldb]

Cheers Dave  - Must have had a Jeremy Clarkson moment with that hammer  .  You got it wrong; I'm _pulling_ it with the tube 

Had a bit 'o time in the shop today 

First off:  This is the start of construction of a boiler for the Cracker.  Boiler making can and has been a very contentious matter. 
I'm by no means an expert on boiler making; this is only my third boiler I'm building, but I have put a lot of effort into researching and trying to understand the subject and the acceptable methods of calculation, construction and testing that goes along with it.
My local government does not have any detailed regulations regarding model boilers, but what I have been able to find mimics the "Three Bar-Litre" rule as used in the UK.  This boiler falls well below those limits, and will receive a complete hydraulic test when done; the results of which I'll show.
If any of the MadModder moderators would rather not have me post this, please do remove the posting.

On to the build then...
Some copper work; and at the risk of being classified as a complete lunatic, I actually enjoy machining copper.  It has a personality of it's own, so takes a bit of care to work with - and therein lies the challenge and the fun for me.  It does not want to be rushed - but dawdle at peril as it will work harden.  If it comes off in little curls, things will come out just dandy.

First off, the boiler shell from some 42mm OD/39mm ID copper tube; sawn to near-length, and set up to trim the ends in the lathe.  I just lightly chucked the pipe on the outside of the 3-jaw chucks inner jaws, and set up the fixed steady close to the jaws to get it on centre; you can see the ring left on the copper tube from that.  Then I moved the steady closer to the tailstock - leaving just enough room to get the carriage in there to clean up the pipe end:


Light cuts with a sharp tool, and it was done - for both sides of the pipe:


Next, the end plates.  The ideal thickness for this boiler would have been 1.4mm - I have 1mm and 2mm thick copper plate, so the thicker one it is.  Two bits of copper plate, marked out with circles 10mm in diameter larger than the ID of the copper tube:


Off to the band saw, and bits sawn off.  When sawing plate, there is always the risk of the sawn-off bits dropping in between the slit on the table and the blade - a sure-fire way to have the excess bit land between blade and bearing or between blade and drive pulley, ending with a snapped blade.    Guess how I figured that out sometime ago.  So for sawing around roundy bits, I've adapted a method of sawing in at a couple of tangents, but stopping just before breaking through the end on each cut.  The blade will push/bend the nearly-sawn off bit away, and the curve can be followed quite closely.  With copper it's easy, as it's quite malleable.  Before breaking through on the last cut, just stop, wiggle the excess around, and it will snap off, leaving a little tooth that's easy to file off.  This shows the excess bits and how things come out:


Once completed for both "circles" I just filed off to the line; 5 minutes of well-spent exercise:


Completed end-cap discs and a relation to the boiler tube:


Some fairly deeply scored rings on the end plates - one on the ID of the boiler tube, the other smaller by the thickness of the plate itself.  These are for reference only, but - they need to be well-scored, as the plates will go through several annealing steps:


My fire bricks are in an appalling state - I wanted to nip off from work and get some new ones for a change during the week, but just didn't have a chance...  Getting ready for the first annealing - with the scribed lines on the bottom, as they are less likely to "disappear" this way:


Showed them the Sievert torch with a 20mm nozzle - 20 seconds, and they glowed dull red - here cooling down and black from the heat:


A quick dip in water (copper does not need the quick cooling for softening- I was just in a hurry) and much to DaveH's chagrin, the hammer needed to come out again

To form the end caps, one needs a former about 0.25mm  to 0.5mm smaller than the "ID of the boiler tube less double the thickness of the end plate".  I was loathe to turn a good piece of available stock down to size, and in no mind to faff around with turning wood to make a former, so I scratched around my bits 'n bobs and found a CCC (Cheap & Cheerful Chinese) socket that was just on size at 39mm OD.  What was nice about it, was that it's corners were nicely rounded over.
I aligned the back of the plate along the earlier scribed rings as best as I could visually with the socket, and using another slightly bigger CCC socket clamped the lot in the vise:


Then started hammering the lot down with an ~1kg hammer:


Just a couple of whacks at 45 degrees along the circle, turn, more whacks and repeat.  No force needed - just a small bend to start off with.  This is was actually the hardest part - with each turn here, the alignment has to be checked on the scribed lines after each turn.  Super precision is not needed - close will do.  With each whack, the copper work hardens, so trying to go all out and just flattening the sides is not even an option.

Once around, the plates are work hardened, so anneal again and repeat - next three photos shows the progress before annealing and repeating each time (Well, You DO like pictures don't you  ):



  (there was one hammer blow completely out of order on the left-hand plate)



With the final round of hammering, I offset the front socket downward so that I could get close to the edges to really get things tight:


Turn everything a bit, more hammering and repeat.  Takes a while, but it's a great stress relief!

The end cap on the barrel; it's nearly a fit, and if I could be bothered earlier to turn a proper former to size, it would have just slipped in.  In fact, a good whack with a hammer would make it stick in the boiler barrel, but that's not good enough - it needs to be a bit under size to allow for proper silver solder penetration later on:


After minimal work on the lathe - just a skim over the edge and turning the ragged end down to size, I ended up with the completed end caps:


Back to the boiler tube, and some near Arnoldidiot proof layout and marking:


A while ago I bought a step drill, as other boiler builders were singing and dancing it's virtues for making nice round holes in copper.  Well, I'm now singing and dancing along  - none of the "rounded triangular" holes from normal drills here; just a nice and round hole  :


The step drill goes up in 2mm increments, but I needed a 15mm hole in the barrel, so I used the step drill to go to 14mm, and then the boring head to open up the hole to 15mm:


The end caps needed some holes poked in them; one of them just a 15mm hole for the flue tube, and the other another 8mm hole for the steam take-off/regulator mounting.
I used the tooling plate in the mill for drilling the holes, but that precluded the use of the step drill as it could not drill deep enough (well, at least not without poking a hole into the tooling plate  )
Seeing as I had two end caps to machine, I used two cap screws as locators, clamped the first end cap down and drilled it 6mm:


Then opened the hole successively to 10mm and 14mm with end mills:


And bored it out to 15mm with the boring head.  A completely boring post by now...:


The second end cap received the exact same treatment, except that it had an additional 8mm hole poked in it:


After cutting some 15mm pipe to length,I ended up with a few coppery bits for today:


Some Scotch Brite cleaned the bits up nicely, so I decided against pickling over night.   I still need to make the needed bushes anyway.

 , Arnold

[sbwhart]

Lovely clean copper work Arnold   


And well shown to boot 

Stew

[arnoldb]

Thanks Stew 

Not a lot done today  - just made the bushes and filler cap from phosphor bronze.

The safety and steam take-off bushes are threaded M6x0.5.  The filler bush is threaded M10x1.25; M10x1 would have been better, but I have not found taps and dies for this yet.
I also hollowed out the filler cap as far as I could to get rid of excess mass that would need heating up and made it look approximately like a steam dome.  In fact, I'm seriously contemplating using the filler cap as an actual steam dome; the regulator bush on the backhead is not far above the maximum water line, and if the loco lurches a bit, water is bound to get into the main steam line.  It's a fairly simple job to add a dry pipe that will extend part-way up the steam dome, and it won't hamper filling too much...


I still have to decide what I want the chimney to look like...:


 , Arnold

[DaveH]

Arnold,

Don’t worry about the boiler. In the UK all they say is go and see “your boiler inspector”.  You ain’t got one Arnold.

Nicely documented and made. As usual well photographed, I see you made good use of your tooling jig.

This is a very nice posting, makes me want to make one.   We could have a race!

It’s coming on, looking good.

DaveH

[saw]

Fantastic I just love it. 

[arnoldb]

Dave, Benny,  - thanks gents.

Dave, I might not have a boiler inspector, but knowing the "system" here in Namibia, one might be "invented" at any time  - besides, I'd rather have things up to standard, especially since I'm showing it publicly and I do value my own and other people's body parts   . 
I love that tooling plate; I can kick myself for not making it earlier in my short machining "career" - and there will definitely be more of them made 
Do you have tracks - or are you going to fit rubber wheels to yours ?  -  - we can definitely have a race 

Well, a coolish day here in Windhoek today, and nothing heats up a cold shop like a big torch  - so I started soldering things together.

First off, some flux around the bushings, and left the flux to dry out a bit while I bent some rings out of some 40% silver solder.  I have two types of silver solder - this 40% cadmium free, and some 40% that contains cadmium.  The non-cadmium needs a higher temperature to melt and flows less easily into joints.  It is also good to note that if solder containing cadmium is used, there are potential health risks associated with it - so I tend to use those very sparingly - only if I need to fix up an already-soldered joint or if I really need the slightly lower melting point:


I also brushed some flux around the holes on the inside of the barrel - I just use a small paintbrush for this:


Then I used a permanent marker to draw "rings" around the holes - this is just some intentional contamination to prevent solder from flowing all over the show.  One can use a soft lead pencil or error correction fluid ("Tippex") for this as well.  I pushed the bushes into their holes.  The rings of solder will actually go on the inside of the barrel:


The assembly was then put down on a fire brick resting on the bushes, and I added the silver solder rings on the inside, with a bit more flux on the rings.  Then I closed up the one side and one end with fire bricks standing vertically.  The front side was left open, as that's where I would be applying the heat (right at the very bottom), and the left side so that I could look into the barrel and check on the progress:


I heated that lot up playing the flame along the bottom - it needs to get dull red for this solder to flow.
The first couple of times two years ago that I tried silver soldering, I had a lot of problems.  The biggest one was thinking the job was a bad 'un when the flux turned black and stopping the heat at that point.  Once I discovered that the flux I have turns black, and with a bit more heat goes crystal clear and the work needs to glow dull red, things suddenly came together.
Once I could see from the open end that the solder had flowed, I left it to cool down a bit, then turned it around to check the result:

While it might look like a dog's breakfast, it is actually a good 'un; the yellowish coloured rings are where the flux did it's job of cleaning and protecting the metal from the flame, and the pinkish-orangey shiny stuff is actually flux that floated to the surface.  There is a nice fillet of silver solder all round the base of the bushes that was wicked through.

Into a bit of pickle it went; I use Citric Acid which is available in the cake baking supplies section of the grocer just down the road.  It's relatively cheap, non-toxic (in fact, I mix the powder with water and just have a quick taste now-and-then till it tastes sour enough) and can safely and environmentally friendly be disposed of down the drain:


While that lot was pickling, I turned up a new bush for the backhead.  In the last post I said I'll add a dry-pipe, so I needed a longer bush tapped M6x0.5 with a short section in the back just drilled out to 3.2mm for the thin copper pipe I have:


Ready to solder the bit of copper pipe on it:

The pipe still needs to be bent to fit up into the middle of the steam dome and trimmed to length.

The end caps are a loose fit in the barrel to allow flux and solder to wick in, but that presents a couple of problems when trying to solder things together, as nothing wants to stay put, and one have to resort to jigs or something to keep things in place.
I chose to resort to the "or something" bit 
I used an automatic centre punch at a slight angle to pop some evenly spaced dimples around the circumference of each end cap - the slight angle causes the soft malleable copper to raise a nice burr on one side of each punch mark:


Now it doesn't just fall down the barrel any more - it has to be lightly tapped into place, and it will leave an even gap right around for the flux and solder to wick in:


More rings of solder; one to fit the barrel and one to fit the flue, and a slight flare added to the flue by tapping it on the end with an old lathe centre I have lying around:


A bit of fluxing later - flux brushed around the inside the barrel where the end cap will go, around the end of the flue (with it's ring of solder already in place) and around the outside and inside the flue hole of the end cap:


Then I tapped the end cap gently into place in the barrel, added the flue, and ring of solder.  I used the other end cap partly pushed in on the bottom (leaving it sticking out so I could get a grip to remove it again) to keep the flue in it's correct position, and supported the bottom end cap in a bit of excess copper tube sawn off the barrel initially.  Some fire bricks were stood on end to help retain and localise heat:


I carefully brushed some more flux over the ring of solder, and heated the lot slowly at first; the flux I brushed on the ring in the barrel was quite wet, and I wanted it to dry out without bubbling all over the show.  Once it dried out and stopped bubbling, I turned open the tap on the torch and played the flame just below the bottom of the end cap, moving it around the outside of the barrel.  The fire bricks really help here by deflecting the flame around the back of the barrel and heating it there as well.  Once the solder around the barrel flowed, I kept the heat on a bit longer and the solder around the flue followed suit.

Once again, the top of the job looks a bit unimpressive - I would have liked a nice even fillet of solder around the barrel rim, but there's a couple of bits that look like there's not enough solder in there.  The fillet around the flue is quite satisfactory:


The back side is a different story though  - There's a nice even fillet of solder around both the flue and the barrel rim, indicating that the solder flowed between the bits as I had intended, and the joints are good 'uns  .:

Apologies for the crappy photo; it's a bit difficult to get the light to catch the inside of the barrel and get the camera at an appropriate angle and focus "down there" 
I'll use a bit of the other silver solder I have to fill in the top rim fillet - if it is really needed.

I put that lot back in the pickle to overnight and called it a day; hopefully I'll get some more done tomorrow.

 , Arnold

[sbwhart]

Nice bit of boiler smithing their Arnold   

Stew

[Stilldrillin]

Very nicely done Arnold! 

David D

[saw]

Way to go Arnold 

[arnoldb]

Stew, David & Benni - thanks gents 

Well, a mixed bag of results for today...

After leaving the lot in the pickle overnight, I started fluxing up the last bits for assembly:


Once again, rings of solder and some extra flux:


Showed it the torch, and got a horrible result.  Some flux had run off the side and some silver solder followed that.  Flux had also flown across nearly the entire end cap, so solder everywhere 
And worst of all, if you look carefully at the bit where the flue comes through the end cap, there's no fillet - in fact it looks like there's no solder in the joint  :

That'll teach me to remember to draw on anti-flux lines and not to use so much flux...
I plonked the boiler back in the pickle for a couple of minutes to get the top cleaned up, and used another ring of solder and a more conservative amount of flux, and ended up with a good clean fillet around the flue.
The boiler was then put back in the pickle to clean up properly.

I made a quick T-piece to fit the boiler back head bush and my pressure gauge and hydraulic pump:


Then collected together all the bits needed for the pressure test - pump, gauge, some ptfe tape, a bung for the safety bush, the T-piece, and of course the boiler which cleaned up nicely:


Some ptfe tape on the bung and T-piece:


All connected up and the boiler filled to the brim with water, before screwing in the bung:


An overview of the layout - ready for pressure:


The boiler maximum pressure as I calculated it would be 40 psi.  This means the hydraulic test must be done to 80 psi - which is 551 kPa.
The first test is to take it up to pressure, and then release it.  The second test is to take it to pressure and make sure that it will retain pressure for at least 20 minutes.

The pump is very quick - just two and a half strokes on the first test, and I'd overshot the pressure already, but that's ok:


I released the pressure by unscrewing the filler cap - you can see how little water came out - just a tiny puddle:


Back up to pressure again, and once again I overshot the needed pressure:


I left it and spent some "office" time to remotely start the month-end run at the company I work for.  Took about 30 minutes, and this is what I found when I got back to the boiler:

  I'ts a good 'un - it's just a pity I ruined the last bit of soldering.

 , Arnold

[sbwhart]

Well done that man
 

Stew

[DaveH]

Arnold,

Fabulous tutorial on making a boiler, - you made it look easy.  (But I don’t think it is)

The boiler is very nicely made – looks great.

Really good informative post, and well photographed.

Thanks Arnold for taking the time to show it.

 
DaveH

[Stilldrillin]

I really need to practice silver soldering....... 

Very nicely done, and shown Arnold! 

David D

[arnoldb]

Thanks Stew    I still have a lot to learn about boiler making though.  There are hopefully some more complex ones in my future; this one is just practising the basics.

Cheers Dave  - I hope I didn't show too much, but rather too much including the little mishaps than too little.  It's not really difficult, but it does take a bit of thinking through and planning. 

David, Thank you  .  I'm enjoying the silver soldering; it does seem to take a bit of practice.  Not with heating things, but in the preparation.  The hardest part for me is figuring out just how much flux to use...

This weekend I'm having to divide time between the shop and my day job...  Just part of the fun of working in IT I guess; some things need to be done when other people are sleeping and having weekends 

Did manage to steal a bit of time in the shop though, and started on the steam regulator - another deviation from the original Cracker plans as it's not included there.
I simply "stole" Dave Watkins's design for Idris's regulator and adapted it on the go.  Not many photos, as it was all just basic lathe work with 8mm hex brass rod.  One exception is the spindle, which was turned from some 4mm stainless steel rod.  That was just turned down to 2mm for about 16mm, then to 3mm for another 10mm  and threaded M3 with a tailstock die holder, and a taper turned toward the collet chuck to _just_ before it would part off:

That left a nice concentric spindle.  The taper was then polished up slightly with some emery, and the very last bit turned off to part the spindle from the stock.

A very out-of-focus photo of the bits made today:

From left to right: 1) Regulator body with M6x0.5 nose and drilled through 2.5mm and then opened up and threaded M6x0.5, 2) the spindle, 3) M6x0.5 lock nut, 4) bush threaded M6x0.5 right through on the outside and drilled 2.1mm through on the inside and the tapped M3 for the spindle part-way through, and 5) pack nut for the spindle.  The bottom 2 pieces are the steam take-off and nut - both threaded m6x0.5, with the take-off an nut designed to clamp down some 3.2mm copper pipe with a silver-soldered on ferrule.

After taking the last photo, I silver soldered the take-off to the regulator body, and dumped it in the pickle to clean up overnight.  Hopefully I'll find a couple of minutes tomorrow to finish the regulator.

As an aside...  I don't like gardening very much, but I do like plants and animals.  The plants in my garden are mostly drought-resistant cacti and aloe species; they don't need much attention and like our weather.  In fact, they are MUCH better at predicting weather than the Met office.  On the way to the shop this afternoon, I spotted a welcome sight; one aloe had started pushing it's flowers, and that means we only have another one or two cold spells before our short spring and then summer is on us  - that's good for shop time:


 , Arnold

[DaveH]

Arnold,
Nicely done, ideal size for your new lathe.

The photo makes them appear to float

Coming on, won't be long now.
 
DaveH

[arnoldb]

 , Thanks Dave

  I really must get that small lathe sorted  - it's just standing there doing nothing.

  Hoptical disillusion; the parts are lying on my "ultra-high-precision surface plate" - aka thick sheet of safety glass...  If the focus is out, things "float".

And no progress to report on the cracker; I finally got some shop time today and squandered it on this lot  :


 , Arnold