# Oh no! Not another Cracker? But there's always room for one more cracker!



## rpbidgood (Sep 17, 2010)

Hi everyone. This is my first post and my first build, I hope I get both right. I bought a lathe a few years ago, but employed it largely making pieces for my other main hobby - model boats. I made several cannons, drive couplings, bushes etc., but nothing that actually "worked". I have been "lurking"on this site for some time now, but the postings for Cracker; Nina; Idris have inspired me to try and make something that really does something. I have been working on a scaled up (45mm) Cracker (and the house) for about 4 weeks and have become so absorbed that I even bought a milling machine last week - what a wonderful machine! I wish I'd had it at the start, my side frames would have been much better (I'm not very good at filing). The wheels are made from some sort of duralumin type alloy that was lying around my shed. It's has a sort of greasy feel when being turned and produces long bits of curly swarf. The wheel bosses are large because I was worried that the soft alloy would strip if I screwed the wheels to the axles too tightly. I have since acquired a chunk of 'meehanite'? and have turned one wheel with a smaller boss as an exercise
 Anyway, a month and a large rubble sack of swarf later I have reached the position shown in the photographs. Next I have to make the cylinder and piston, an exciting but slightly daunting prospect.


Questions:
 (i) If I use a template to drill the exhaust and inlet holes on the standard, what angle before or after TDC should I go for. Common sense seems to suggest that the steam should be admitted almost immediately after TDC and the exhaust just after the bottom of the piston stroke, but could last for the whole upward stroke (I don't need reverse on this) - but common sense has let me down before.

(ii) I was trying to apply a nice surface finish on the standard with a fly cutter, but ended up with something that resembled a ploughed field -the brass seemed almost melted. I wasn't taking a deep cut, was the speed too high? the fly cutter is new, so should be sharp. I managed to redeem the piece with some judicious sanding, but it doesn't bode well for the piston.

I attach some pictures of the progress to date.


----------



## GordTopps (Sep 17, 2010)

Hi rpbidgood & wEc1 to our forum.

No doubt some knowlegable folk will chirp in with your questions

Regards from Sunny ( and wet) Spain


----------



## Tin Falcon (Sep 17, 2010)

First of all welcome to the board. and thanks for tel us a bit about yourself and interest in this hobby. 
I have built several Oscillators that all run well I have always layed out the hole according to print. 
Also perfect alignment is not needed the design is pretty forgiving. as for how to make a drill jig /template. 
IIRC A couple of the Elmers engines plans explain a jig as does the KN Harris book . 
I will try to get you a specific link or reference when I have time. Or someone else may help.
Tin


----------



## zeeprogrammer (Sep 17, 2010)

Welcome to the forum rpbidgood.
I can't help with the questions (I've just started out).
There's been a Cracker or two on the forum and I'm sure someone will pop in.
I have an interested in locos too so I'm looking forward to seeing your progress.
Have fun!


----------



## kustomkb (Sep 18, 2010)

Welcome, and very nice work!

Does your fly cutter look something like this?






You say it was new, does that mean it is a brazed carbide tip? If it is a high speed steel, (or carbide), relief angles will have a lot to do with its performance. Did it squeal while you were cutting? Also a thin piece will tend to chatter.


----------



## shred (Sep 18, 2010)

The Cracker motor is a simple oscillator-- I built mine to the plans and stuck the holes at the 'end' of the cylinder travel (actually I missed with the exhaust hole-- I had to enlarge it so they'd line up). Might not be the very best use of steam, but hey, it's a Cracker, not a super-heated piston-valve multi-cylinder jobbie


----------



## rpbidgood (Sep 20, 2010)

Kevin,

Thanks for your interest.

The cutter is very similar to the one in the picture - I think it's hss. (I attach a pic.) It didn't make too much noise, but the brass seemed to have 'melted" (exaggeration) and formed a 1/8" lip over the edges. Strangely enough, I used it again to form the final, flat surfaces on the cylinder and it behaved impeccably. Perhaps my technique is improving?

If truth were told, I was a little nervous about the boring operation, and it did look a bit agricultural initially, but after playing around with some different tools I managed to get it pleasantly smooth. Big sigh of relief. I'll have to hone it next.

If it is of any interest, I attach a picture of a wiggler (or is it a wobbler?) that I made to centre the cylinder. It uses a swivel joint from a model car track rod end. The spring maintains pressure on the job and the neoprene (fuel) tubing keeps everything in place. 

Wasn't the 'Wiggler' Batman's arch enemy. Even I wouldn't be frightened of the 'Wobbler!'


----------



## xo18thfa (Sep 22, 2010)

Alright, a Cracker. It's a great machine. Yours is coming along nice.


----------



## GWRdriver (Sep 22, 2010)

rpbidgood  said:
			
		

> . . . employed it largely making pieces for my other main hobby - model boats.


Welcome rpbidgood,
What kind of model boats? I also have an interest in model boats, specifically wooden boats that will need a steam power plant. Also, I would ask you where you are located as it's eventually helpful to know where one is loacted, but the "bits of curly swarf" told me what I need to know.


----------



## rpbidgood (Sep 26, 2010)

Hi GWRdriver,

The last boat was a civil war (American) paddle steamer - Coeur de Lion, but I have a varied interest. I have an unstarted 'kit' of the Disney Nautilus which will probably be my next project, once I finish this Cracker.

I always wanted to use steam power in my boats, but was put off by the price, and I didn't think I was capable of making the steam plant myself. This site has given inspiration. Who knows now?

[*u]Cracker update[/u]*

Tried drilling/tapping the cylinder to take the trunnion pin. I had grave reservations about my ability to drill/tap an accurate hole just a couple of mm deep. I failed dismally. How do you drill a 3 mm hole perhaps 0.1" deep and put a thread on it? (sorry about the mix of imperial and metric).

Hours of work down the drain (I am new to this and a slow worker). I'm going up the shed (workshop) to try plan B.


----------



## rpbidgood (Feb 12, 2011)

Commitments have prevented me working on this for a few months, but I have now managed to progress a little. Last week I finished the engine and attached it to my airbrush compressor. More in hope than expectation I flicked the flywheel and the little beauty started running! I've made boats, planes, helicopters, and all give a sense of satisfaction when they do what they're supposed to, but I don't think any of those compares to pleasure I got when my engine started puttering away by itself. Wife bemused by my smug expression. It needed about 15 psi initially, but soon was ticking over around 2 psi (if the gauge is accurate). Next step was to connect the drive chain - This worried me a little - I have used no gears and have a direct chain dive to both axles (14:18 tooth or 1:1.3 approx.) and it's been a long time since I "played" with meccano. Would there be too much friction? - but no, the wheels turned nicely, and after a few minutes the stiffness left and the engine ticked over again about 2psi - I can just about keep it going for a few seconds on breath power - wife impressed (I think).
I don't want to appear sycophantic, but it is the wonderful models/articles/ideas on this site that inspired me to have a go.


----------



## rpbidgood (Feb 12, 2011)

Inspired by the progress on the engine I decided to tackle the boiler. The end plates were screwed to a wooden block and turned in a 4 jaw chuck - the method described by Bob Sorenson in the excellent account of his building of "Nina". The attached photo shows the unsoldered boiler so far - I will have to summon up the sinews before I start silver soldering.
ps. I don't think I'm going to paint this loco, so I'm not sure I can live with that shiny smoke box door.
Attached is the safety valve - it seems to work well on compressed air, but looks a little small to me. I think I'll make a bigger one, but first the funnel/stack. I wanted a tall pipe on a "tailored" base. I found an old piece of brass and milled the curvy bit on the bottom, again pinching Bob"s idea. Popped it on the boiler - it's too big. It looks silly. And since I have bored it out I can't turn it down any smaller. The milling took a long time. Misery. Back to the drawing board.
Question I am thinking ahead, but what sort of flame do we aim for on the burner? The hotter, blue flame or the gentler, but dirtier luminous flame?

Keith.


----------



## compspecial (Feb 12, 2011)

Congratulations RP! and what's wrong with a "cracker anyway?" Welcome RP
               stew


----------



## Groomengineering (Feb 12, 2011)

Looks good Keith! Not sure there can ever be too many Crackers. ;D

Cheers

Jeff


----------



## shred (Feb 13, 2011)

We're nowhere near the Cracker-limit 

Looks great. Running on 2 PSI is very good-- should be relatively easy to get going on steam then.

I think I have a bit on making the stack flanges for mine-- I used a boring head on the mill to cut the curvature on the end which wasn't so bad.

For flames, you want the roaring blue blowtorch one. My burner will only do that inside the flue-- outside it's quite a bit less active.


----------



## Peter. (Feb 14, 2011)

That is an interesting-looking measuring tool in the 'safety valve' pic Keith. Does it have a specific purpose?


----------



## BMyers (Feb 14, 2011)

There is always room for more crackers. I enjoy seeing how everyone's version is different and interesting. Maybe it should be mandatory that all members build a cracker.


----------



## rpbidgood (Feb 18, 2011)

Hi Peter.
It is a sort of neolithic, vernier callipers.The 'front' side is just a simple ruler, but the reverse side, pictured, has a vernier scale and shows the readings given on this instrument and on a digital callipers. The modern instrument is obviously easier to use, but the older one fits nicely in a pocket and its use amazes youngsters who've never heard of a vernier scale. It is a beautifully made instrument, and even though it is probably at least 50 years old, the brass slider has little or no free play but still moves easily.
I also attach a picture of the Mark II funnel.


----------



## Gedeon Spilett (Feb 18, 2011)

Hi,
Nice work with your cracker!
I have just finished three of them, and after unsuccessful attempts to drill holes under 0.2 mm for the burner's jet, I finally choose to install a burner saved from those cheap lighter-style small butane torch with success. Although it takes ages to get the water boiling, once hot, the loco runs for 25 minutes pulling two coaches at a lively pace. If you take the larger burner from a pencil torch, she runs now fiercely with many coaches behind (I have tested up to 8). in the boiler tube, both type of burner are not roaring as usual but whistling at very high pitch while burning, and this is useful to know if everything is going right, contrary to silent types of burner. 
I have to give them a coat of paint, not my favourite task.
There is always room for many more crackers!
Zephyrin


----------



## bearcar1 (Feb 18, 2011)

RP, that is some very clean looking work you have been doing. I too have one of those 'antiquated' brass caliper arrangements and use it some times just for the nostalgic bit of it. It was my Grandfather's and I cherish it, and by putting it to work once in a while, I feel like I am paying him tribute. Anyway, I notice in that last shot, you seem to have a silver colored smoke box door affixed to the front of the boiler in lieu of the usual copper cap arrangement. Can you elaborate a bit on it please. It seems to have a pleasant convex shape to it and I'm curious as to how it will finally be held in place. Keep up the good work and thanks for sharing.

BC1
Jim


----------



## rpbidgood (Feb 20, 2011)

Jim, I've always had problems painting brass - I can't bring myself to do it! I have a Paddle steamer, suitably aged that sports a tall, brass chimney stack. I suppose it looks a bit silly, but I'm the owner, captain, shipbuilder, so I don't take complaints from the crew or passengers.
 The smoke box door is made from a piece of scrap - duralumin, I think. I turned it into a rough convex shape using the compound slide, taking a number of different slices at different angles, and with the lathe turning slowly, I smoothed it out using wet and dry on a rubber , sanding block. I admit this with a certain amount of reluctance, I'm new to this, and I'm not sure whether it is accepted practice to use a file etc. on the work in the lathe, but I couldn't think of any other way to do it.
 If I use the door, it will be screwed to a thin, cross member in the smoke box - the screw will have a few arms on it for effect. I say 'if', because although the chassis is made from some sort of alumin(i)um alloy, it has adopted a subdued, dignified patina, whereas the smoke box door is still gleaming like a mirror and shows no sign of ageing gracefully. I don't know if I can live with it.


----------



## bearcar1 (Feb 20, 2011)

Hello RP, I hope you did not think that I was 'complaining', quite the contrary. I should have been more concise with my statement. I was inferring that I like the shape as well as the visual difference that it makes opposed to a having a plain copper end cap being fixed in that position. I understand completely about not wanting to paint brass etc., the metal just lends itself naturally to a sophisticated appearance. I have some immersion formulas for coloring aluminum either Black or Blue colors if you are so interested or perhaps you could anodize it and then dye it any color you wish (almost). I admire the shape/design of the chimney as well. Keep up the marvelous work. Tally HO! Thm:

BC1
Jim


----------



## rpbidgood (Feb 20, 2011)

Jim, I wasn't offended - I was just rambling. Thanks for the comments. Keith.


----------



## rpbidgood (Apr 16, 2011)

I have managed to get back to the shed and get some work done. I finished the regulator/lubricator - it is based on a design by Tubal Cain which he credits to LBSC (words and music etc.). It was my first attempt at silver soldering, and I struggled to get the temperature up - how on earth am I going to manage a larger chunk of metal like the boiler? 

I fancied having a water gauge, but realised quite quickly that I wouldn't be able to make it small enough to fit on the cracker, but, having started, I felt I might as well carry on. I am now the proud owner of a redundant water gauge - it's been good practice, and I finally got to use my rotary table to make the 'drain cock' hand wheel.

What's next? I've been putting it off, but soon I'll have to bite the bullet and try to solder the boiler.

Gonna need a bigger gun!


----------



## metalmad (Apr 16, 2011)

Please dont use that word :big:


----------



## rpbidgood (Apr 17, 2011)

Poetic licence.


----------



## metalmad (Apr 17, 2011)

one day i gotta make a steam engine 
Pete


----------



## rpbidgood (Apr 18, 2011)

I invested in a larger, professional blowlamp, but still struggled to get the temperature up. In the end I used the new lamp, and, aided by my older, smaller blow torch I finally managed to melt the solder - it's not my neatest job and looks a bit monumental, but I think it's secure. Perhaps I should have made a firebrick hearth to reflect the heat back onto the job. Next time.
ps. The eagle eyed amongst you might notice the flat bit on the front of the boiler - I knocked it over just after I finished soldering the front end. It's amazing how soft hot copper is.


----------



## Tony Bird (Apr 18, 2011)

Hi,
Enjoying this thread very much. I have built several Crackers, they work very well and far more powerful than one would think. I do have a bit of an issue with the gear ratio that you are using it is a bit high. I think the drawings call for a 4:1 reduction with a 20mm wheel. I used 4:1 with 24mm wheels, which were used to give a little more track clearance for use in the garden, this works OK. A friend uses Delrin plastic sprockets and chain (I believe a large range of sizes are available) on his Sentinel steam locomotive the plastic used stands the heat, oil and dirt very wheel. Using these sprockets and chain would give a larger choice of gear ratios. I found that using an insulated material for the false saddle and fire box makes a big difference on how hot the chassis gets. I used a piece of hard wood. Hope you find this helpful.
Regards Tony Bird.


----------



## BMyers (Apr 18, 2011)

Nice work ! Makes me want to build another cracker or similar loco.


----------



## rpbidgood (Apr 19, 2011)

Oh dear. Back to the drawing board.


----------



## dreeves (Apr 19, 2011)

Dont feel bad I have several of those. I hate to machine copper.

Dave


----------



## rpbidgood (Apr 21, 2011)

Back from the drawing board - the mk. 2 smokebox complete with funnel. I am also getting happier with silver soldering.


----------



## rpbidgood (Jun 25, 2011)

I haven't posted for a while, but I haven't been idle. I initially had a simple chain link to the wheels with a gear ratio of 1:1.13 ish. When I connected the loco to my air compressor it lurched across the "wooden" floor in a most undignified manner until it got up to speed (too fast for my liking) - the lurches corresponded to the power stroke of the piston. So I built another chassis to accommodate a more sophisticated gear train. (I introduced idler gears to retain the forward motion). I also made another lubricator/regulator with a larger reservoir and an oil trap. I had intended to make my own gas cylinder,but after reading several articles I decided to plump for a commercial one. I have retained the original gas cylinder on the flywheel side, which looked a bit boring compared to the piston side. I have been experimenting with poker type burners, and have cannibalised from a couple of old blowlamps, but one was obviously underpowered and the other was uncontrollable. I have an acquaintance who owns a precision engineering firm and I'm going to ask him if he can drill a 0.2 mm hole in the jet a la Glaser design. We shall see.
I have included several pictures to illustrate the progress - I have tried to capture a "steampunk" look.


----------



## metalmad (Jun 25, 2011)

Hi Rp
its looking wonderful
I sent some Karma your way as I love trains 
I gotta have a go at one of these one day 
Pete


----------



## shred (Jun 25, 2011)

I like it! Lots of cool details.

If you can't get your friend to make a jet, they can be bought various places-- mine was from a camping stove and approximately 0.2mm


----------



## rpbidgood (Jun 28, 2011)

I found out yesterday that my acquaintance had sold up the business and retired, but I managed to by a 2mm gas nozzle off Ebay for a couple of quid - it's got a BA thread, so more expense (I'm all metric), but my next project will be a 5" gauge loco, Speedy, so the "new" taps will probably come in useful. Actually, the very next project will probably be a Disney Nautilus. I bought the model, and several other projects before I retired in the belief that after retirement I would have little money and lots of time. I was right about the money.
 I have included a rear view of the cracker, showing burner in place and the dummy gas cylinder.


----------



## rpbidgood (Jul 5, 2011)

I fitted the gas nozzle today and fired it up- see picture. It burned nicely enough outside, although given the size of the air holes and comparing these to the single hole on a bunsen burner, I did expect the flame to be less luminous. The flame however went out as soon as I inserted it into the boiler. This suggests to me that I'm suffering from a lack of air? I could increase the size of the "side" holes or drill a secondary air hole or both. Any ideas?
Keith.


----------



## Tony Bird (Jul 5, 2011)

Hi,
The jet is half way across the air hole try moving it back to increase the effective size of the hole before altering anything else.
Regards Tony.


----------



## Rayanth (Jul 5, 2011)

I am by no means familiar with boilers and their operation but there are two aspects to a lack of air to a flame in a generic closed environment:

Not enough air input: caused by insufficient intake, the flame is burning oxygen at a faster rate than it is being introduced to the chamber. A larger intake hole might fix this, however :

Not enough exhaust outgo: if the combustion byproducts from the flame are accumulating in the flame's chamber, even if there is sufficient airflow in, the flame will be starved of oxygen as the exhaust gases prevent it from reaching the flame.

In a generic "enclosed" flame environment, smooth airflow is required. Often this is done by allowing the hotter exhaust gases to escape upwards, causing a convection current to draw fresh air to the flame from an air intake below. If this is the way your boiler design works, then I would also look at the exhaust path possibly being too small or too complex, preventing gases from escaping before they build up and stifle the flame.

- Ryan


----------



## Tony Bird (Jul 6, 2011)

Hi,
Sorry but I'm not too good on theory but have made a burner for a Cracker. Hopefully the following photographs will help. A small air hole was made in the burner tube in front of the jet. This hole was enlarged until the flame looked right and was controllable high/low.
Small hole.





Larger hole high setting.




Larger hole in low setting.




Test in flue tube same size as fitted to boiler









Hope this might help.

Regards Tony.


----------



## shred (Jul 6, 2011)

FWIW, my Cracker burner doesn't burn for beans outside the boiler, but roars away when installed, so be sure and try it installed as well.


----------



## rpbidgood (Jul 7, 2011)

Thanks, I will try all your suggestions.
Keith.


----------

