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

[rpbidgood]

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]

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]

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

 

[rpbidgood]

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 ****' 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]

Please dont use that word :big:

 

[rpbidgood]

Poetic licence.

 

[metalmad]

one day i gotta make a steam engine
Pete

 

[rpbidgood]

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]

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]

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

 

[rpbidgood]

Oh dear. Back to the drawing board.

 

[dreeves]

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

Dave

 

[rpbidgood]

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

 

[rpbidgood]

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]

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]

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]

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]

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]

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]

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