Slightly Loco

[shred]

Here's the Slightly Loco running on live steam. Without a burner and gas tank built, I'm using a creme brulee torch somebody gave us years ago that got seconded to general shop duty and silver-soldering of small parts.

In the video the engine is running on about 10 PSI steam. That's all this torch can get out of the boiler with the engine going. Hopefully a real burner will improve that.

[youtube=425,350]7EkiiEZTk2A[/youtube]

[ame]http://www.youtube.com/watch?v=7EkiiEZTk2A[/ame]

 

[Macca]

Looks good Shred, I can't wait to see it move itself along.
I started playing with some bits for mine tonight, I grabbed some 1/2" pipe for the flue, but it looks too small to me. It has an internal diameter of just over 10mm (about 0.4" ???). In your pictures the flue looks larger than that, do you know what the I.D. is?
I think maybe yours is 1/2" I.D. whereas mine is 1/2" O.D.

 

[shred]

Looks good Shred, I can't wait to see it move itself along.
I started playing with some bits for mine tonight, I grabbed some 1/2" pipe for the flue, but it looks too small to me. It has an internal diameter of just over 10mm (about 0.4" ???). In your pictures the flue looks larger than that, do you know what the I.D. is?
I think maybe yours is 1/2" I.D. whereas mine is 1/2" O.D.

The ID on mine is a little over 1/2". It's sold as '1/2"' pipe, but the OD is closer to 5/8" (add 1/8"th to the sold-as size of copper pipe to get the real OD). You're probably looking at a piece of "3/8" pipe, which has an OD around 0.5".

The ID can vary by what thickness the walls are-- K,L or M. I think my flue is the L type.

http://www.sizes.com/materls/pipeCopper.htm has a handy chart.
http://Copper.org has a ton of info, but their site loads very slowly for me.

 

[J. Tranter]

What gears are you using? I'm having problems finding some.
Thank you
John T.

 

[Macca]

O.K. I think I have this copper pipe sorted out.
The Australian standard (1432:2000 for those keeping score at home) is some weird half-breed of metric and imperial. For example DN15 pipe (commonly sold as 15mm) has an outer diameter of 12.7mm (which is apparently equivalent to 1/2" pipe). DN80 has an outer diameter of 76.2mm (which is 3"). They have converted imperial pipe sizes directly to metric, and then rounded the result to get the new metric pipe size. There seems to be no rhyme or reason to the rounding off, some go up and some go down.
What I need is DN18, which has an O.D. of 15.9 mm, Unfortunately the hardware stores here only seem to stock DN15(1/2") and DN20(3/4"). I will try to get to a plumbing shop on the way home from work tommorrow, and see if they have any in stock. I hope I don't have to buy a 6m length though.

 

[jack404]

Australian standards.. bloody nightmare..

good luck

 

[shred]

What gears are you using? I'm having problems finding some.
Thank you
John T.

I used metal R/C car gears from a hobby store that caters to the high-end gas & electric parking-lot racer crowd. I just looked for the combination of smallest gear and biggest gear I could get within the same DP.

[Update: I found a packet from one of them-- they're from Robinson Racing and a 48P pitch- http://www.robinsonracing.com/catalog/48pitchpinion.html]

 

[shred]

O.K. I think I have this copper pipe sorted out.
The Australian standard (1432:2000 for those keeping score at home) is some weird half-breed of metric and imperial. For example DN15 pipe (commonly sold as 15mm) has an outer diameter of 12.7mm (which is apparently equivalent to 1/2" pipe). DN80 has an outer diameter of 76.2mm (which is 3"). They have converted imperial pipe sizes directly to metric, and then rounded the result to get the new metric pipe size. There seems to be no rhyme or reason to the rounding off, some go up and some go down.
What I need is DN18, which has an O.D. of 15.9 mm, Unfortunately the hardware stores here only seem to stock DN15(1/2") and DN20(3/4"). I will try to get to a plumbing shop on the way home from work tommorrow, and see if they have any in stock. I hope I don't have to buy a 6m length though.

As long as you can get a burner down the pipe, a smaller flue will allow for more water in the boiler. IIRC the original plans had a 15mm OD flue, but as long as the holes in the ends match up, there's not much need to stick exactly to spec. One thing to look for is what's called a 'repair coupling'-- those are sized to telescope over the next-size down pipe and are available in short lengths at even the so-called hardware stores here, so one sized for DN15 might be just the ticket.

If all else fails, try a plumbing supply store. They don't much like DIY types in many of them but if you say you're making some toys and that's what the plan calls for, they'll probably be happy.

 

[shred]

Got the Goodall valve done. Strictly speaking, it's a 'Goodall-type' quick-fill water valve since Mr. Goodall didn't make it, but as info is a tad difficult to dig up on them unless you are in-the-know, I'm going to leave it there like that for the search engines to pick up.

Here it is with the Crap-o-Cadtm drawing. Note to self: Make more use of the color upgrade

Anyway, the key to these clever things is the little silicone rubber sleeve; the black part on the thin end at left in the picture. It covers a port hole (actually two) which connect to a blind hole coming from the big end (the 'top' of the valve once installed). The idea is once this is screwed into the boiler, you stick a source of pressurized water in the hole at the top (I'm using a 25ml syringe, so I drilled the top to fit that; traditionally, converted garden spray bottles are used) and the incoming water under pressure squeezes out past the rubber sleeve, refilling the boiler. The pesky steam and associated stuff you want to keep in the boiler stays there because as soon as you release pressure the rubber pulls back down over the holes and seals them.

This one is somewhat smaller than most-- most use the 1/4" silicone tubing, but that wouldn't fit in the steam banjo. I spent a while looking for thinner silicone tube, checked the hobby shops, fishing stores and eventually found it masquerading in the archery supplies as peep-sight parts.

The way I machined it was to chuck some 1/2" brass bar in the lathe and turn 0.5" down to the 5/16" thread major pitch, then turn the end down to 0.2" dia for a length of 0.3", switch to a parting tool and cut the o-ring groove and make the .125" dia neck. Then I threaded with a die, un-chucked and carried the bar over to the mill to drill the #55 cross-hole. (Much easier to hang onto for drilling before parting off). Part off back on the lathe. I had a little length of 1" bar already drilled and tapped to match, so I put that in the lathe, screwed the partially-done valve in and finished the top, drilled the 5/32" filler hole and then the 1/16" blind hole with some careful peck drilling. Unscrew, wrestle some tubing over the end, trim with an X-acto knife, pop on an O-ring and it's done.

 

[shred]

Got a couple more things built this weekend;

First, after a trip by a train-specializing hobby store I got the idea to make some wheel rollers. The idea being you can put a set under each driving axle of a locomotive and it can run in place. Handy for debugging and steaming up and so on. They're a pretty simple design-- bolt some skate bearings to the sides of 1.25" thick blocks. I slotted mine down the center so they'll clear the third-rail common to almost all O-gauge track (the bearings do not touch the track even though it looks like it in the picture)

The slot is 1/4" wide, so they'll also clamp onto a piece of 1/4" stock for non-track usage.

You'll notice that one of mine only has 1 set of bearings. Those of you playing along at home will realize the wheel spacing on the Slightly Loco isn't enough to run two pairs of skate bearings between them. I had thought I could just run one on the front wheel set and the back two would keep it in place, but unfortunately the vibration set up by the wobbler is enough to render them not very useful. Ah well, I can use them if I do a longer wheelbase O-gauge loco and they make cool indestructible toy cars for the kids

 

[shred]

The other thing I got done this weekend was the butane gas tank and valve, which are assembled into one unit. The tank is a pressure vessel like the boiler, so the same cautions and testing should take place with it too. I'm planning to mount it on the left side with the gas valve control coming in from the left side window as long as the burner cooperates. The Ronson-type filler valve will be accessed via lifting off the roof.

You can also see the Goodall-style filler valve is installed, and the very sharp-eyed will notice a new hole in the smokebox support that was added to act as a condensate drain and provide some fresh air flow to the smokebox (reportedly small-scale gas burners prefer that, but I don't know why)

 

[J. Tranter]

Can you give more info and pics of your butane tank? I'm getting all my parts together so I can have a go at making this engine so I can use all the help I can get.
Thank you
John T.

 

[shred]

The butane tank is mostly to the plans, except for using the closest-size-imperial copper pipe (I forgot which but it's very close-- 3/4" maybe?), imperial tooling for the valve body hole (1/4" so I could use an end mill to drill the offset hole) and innards (#4-40 threaded needle & #10-32 o-ring seat threads, #59 outlet, 1/16" inlet) and I put in a bushing for the Ronson valve (swiped from a $1.79 Harbor Freight Pencil Torch; needs fine-thread metric tap) in the top instead of cutting it all from one piece of solid. That let me fix the un-drilled bushing in the hole for a quick pressure leak-test. I'm not sure I like the end-cap construction with silver-solder however-- it seems easy to make a poor joint. The way I did it (setting a ring of 1/32" SS between the parts & heating) left quite a gap that had to be filled. Were I to do it again, I'd think hard about flanged copper ends or using pipe caps.

In Tony's writeup, he talks about using the burner from a pencil torch as a burner. That would work, but the way the cheap HF torches are made, the orifice is only a tiny punched piece of foil trapped in the burner head which clogs easily and can't be un-stuck. The Ronson-style gas filler valve does seem to be adequate quality and easily removable with a 'security' screwdriver bit set.

For the jet, I plan to use some camp-stove spare-parts. Jetboil has a maintenance kit with a jet that I think is .021mm in a kit with some O-rings and piezo sparker for $10 (that jet also uses an odd metric thread). Other stove spare-parts that might be usable include MSR-- their 'Kerosene' jet orifice is listed as 'smaller than #80', but I've not found any actual measurements (it seems to be threaded 1/16"-NPT). I also found an article including info on swaging larger (as-in #70-ish) holes down to jet sizes, but had already obtained the Jetboil parts, so I've not tried it.

Also, if you haven't started cutting yet, Tony has built some newer versions with slightly lengthened frames (~10mm) and the gas tank moved to under the rear frame rails. That's a neat tidy solution I would have gone with if I'd thought of it, Ford Pinto flashbacks notwithstanding

 

[shred]

The burner is made. That completes the Loco parts!

[Note: I neglected to insert this here earlier, so I'm sneaking back in to do it for the sake of continuity]

The burner is very different from the plans. Reportedly the one in the plans doesn't work that well and the authors switched to a 'poker' style burner. I got some details from Tony directly and modified them in the usual Slightly Loco style.

Here's the Crap-o-CADTM drawing with what passes for the key measurements (drawn, as usual, after the part is made-- notice it doesn't actually match the picture; I discovered that making the last two slots the same depth as the others made the burner much easier to light and keep lit.)


(click the image for a larger version)

The jet is from the JetBoil camping stove spare parts kit. The thread was so oddball metric that instead of waiting for a tap, I drilled a close-fitting hole and loctited it in place [edit: this isn't a very good idea.. silver-soldering it to a threaded sleeve would be better]. If you make the brass parts push-fits, it makes tuning and tweaking easier, even wholesale replacement of the burner if you want to try more slots or different configurations. You can anchor them in place later with some high-temp glue or solder.

[end of insert]

[double-extra insert]
With a loupe, I did my best to estimate the size of the JetBoil jet orifice. Near as I can tell, it's about .008" or about... .21mm.. I wonder if that's why it has "21" stamped on it

Also note later on I made a right-angle input jet-holder to make the plumbing neater.
[end 2X Insert]


All it needs now is some tuning and a lot of polishing and detailing. That won't happen for another week or more as I'm off to see the family... if I can ever get out of the Phoenix airport... been stuck here for 6 hours already and another 2 to go

Anyway...

 

[shred]

It moves! I got the burner tweaked and running with the JetBoil jet (the burner works very poorly outside the boiler flue, but well enough inside) and the butane tank valve mostly sealed up, so here's video of the very first run at my extensive R&D Test Facility (ok, it's a loop of snap-track on the garage floor ):

​

;D ;D ;D

Lighting the burner is fun. Turn on the gas and hold a lighter over the smokestack. A tall blue flame shoots out of it for a bit, then sucks back into the boiler.

Next items are to attach the roof, shorten the gas valve handle and improve the gas tank mounting. And go buy more gas. I ran out playing with it

 

[ksouers]

That's awesome, Shred!

Congratulations! It looks and runs great! :bow:

Love that high-falutin', super secret test facility. Where is it? Area 56 1/2? ;D


Kevin

 

[Maryak]

Oh what a wonderous machine

Best Regards
Bob

 

[joe d]

Shred

That's super! sounds good too. (I've got some of that test track in my secret storage facility behind the furnace....)

Cheers, Joe

 

[stevehuckss396]

Just saw the video. SWEET!!

 

[shred]

Thanks all. I'm getting dizzy watching this run in circles, it's so much fun.

For those having trouble viewing it, there's a murkier version of the video on YouTube now

[youtube=425,350]3hcLNzA0x2E[/youtube]
[ame=http://www.youtube.com/watch?v=3hcLNzA0x2E]http://www.youtube.com/watch?v=3hcLNzA0x2E[/ame]

And I sneaked back in to my pre-Xmas post and put up some details on the burner.