second engine project: candle steam

[drysdam]

My inspirations:
[ame=http://www.youtube.com/watch?v=ka3wmoI23C4]http://www.youtube.com/watch?v=ka3wmoI23C4[/ame]
and
[ame=http://www.youtube.com/watch?v=focLZTLkcTk]http://www.youtube.com/watch?v=focLZTLkcTk[/ame]

I finally found some plans here: http://www.steamer.cz/par_min.html

But the plans are in metric and Polish. Some English is given, but not well-translated. So I'm redrawing it in pieces, but not converting everything to especially easy numbers (like the burner body is 57/64" rather than simply 1") except where I'm forced to. The plan is for this one to be a prototype of a small production run to give as Xmas presents this year, so I'm just getting the kinks out for now.

No power hacksaw and I barely trust my bandsaw to cut wood, let alone metal. So after about 40 minutes of exercise, we have two blanks:

Here's the bottom of the burner body. Notice I put a small "indent" in there of about 1" diameter (later widened to 1.5"). I'm going to put a etched brass "manufacturer's logo" in there. I'll post pics of that process too when I've done it.

I wouldn't include this boring picture except I completely forgot to take any pics of machining the lid and I need to show SOME work taking place.

Completed burner base. Total time: ~3 hrs. (Hey, I'm a n00b!)

Completed lid. Total time: ~2 hrs. (I'm getting faster!)

Closeup of flaws. In particular, note my terrible attempt at putting a neck on the base shoulder. I should have used a parting tool rather than attempting to jam a threading tool in there.

But they fit together pretty well. The diameters are right on the nose. There's still a tiny gap between, either because I didn't get the linear dimensions quite right or because of the neck problem.

I was going to order some wick online when a thread here alerted me that cotton rope might work. Don't have any of that either, it turns out. But a snippet of cotton rag works beautifully.

This part isn't quite finished as the boiler supports ride on the burner lid. But I'll drill those once I'm sure I'm able to bend the 3/32" brass tubing I have. Otherwise, I may need to go with a different diameter or material.

 

[drysdam]

Oh I forgot to mention the biggest mistake I made: hubris. Riiiight at the end of the burner base I was getting pretty cocky. "I'm, like, one with the machine, maaaaan!" And then I hit the base with the tool bit and put a little groove in it. Too deep to buff out. I could machine a few thous off I guess, but I'd probably end up in a "now take a little of THAT side to even it up" situation. Plus I should leave myself a reminder to remain careful and patient even in the home stretch.

 

[ProdEng]

Looks like a nice project you have going there, I enjoy tiny engines also. Getting them to run is apparently a bit of a challenge so look forward to seeing how you go. By the way, the source of your drawings is Czech rather than Polish though the languages are quite similar.

Jan

 

[rebush]

drysdam: Looks interesting. You're off to a good start. Is there a way to control the RPM's once the boilers heated? Will be along for the ride. Roger

 

[fcheslop]

Hi, a nice project I love building small engines as well.Good luck with the build
kind regards Frazer

 

[drysdam]

No, there'll be no way to control RPMs. This engine is basically identical to the simple wobblers typical of first builds but the air pressure comes from actual steam.

 

[ShedBoy]

That is a small wobbler. I have seen one in an old book which was along the same lines but was called a thimble engine as the boiler was the size of or did use a thimble. Maybe we need a smallest wobbler competition? Nice start on the burner.
Brock

 

[drysdam]

Sorry for the delay in posting more pics. Some of the delay is due to Interference From Life but most of it is that I had to make the following 3 pieces two times each. On the first, I drilled a 5/32" hole instead of a 3/32" and my putting-it-back-on machine is out at the shop right now. On the second, I messed up the threading. (There's a longer explanation of that which I'll post a link to after I write it. I'm putting it on my own site so I can link my local model engineering club to it.)

I've had some good luck and some bad luck using a parting tool, so I thought I'd try to save myself some sawing effort and part (between centers no less!) to get my boiler support collar made. That seemed to work OK.

Even better, it made my drilling setup pretty simple. The 60° bottom side of the screw is self-centering into the center drill mark on the collar. (I probably should have drilled first and then parted off, but I didn't think of it.) The rest of the setup is a v-block to support the collar, an angle plate for verticality and a "riser" under the v to keep the drill chuck clear of the angle plate.

This is the picture of me using the wrong drill because it shows the setup more clearly.

Boring. In the second photo, you can see some masking tape around the part. That's holding some bits of steel can around the part to protect the aluminum from the chuck jaws. I still get dents if I tighten too hard, though. I've had a little better luck with copper shims. I'm thinking I'll bend a couple of those to fit the jaws rather than the work, though, to make them easier to install. Unless there's a better way?

The boiler support collar completed. (This part will make more sense once you see it in "action" in my next post.)

 

[drysdam]

The boiler and boiler cover will again be a combination of photos from my first and second attempts, which explains some incongruities you may notice.

Turning down the boiler body

And threading it. I threaded before I bored to save time in case I screwed up. In fact, I saved no time because I didn't know I'd screwed up until I'd finished BOTH boiler and lid.

Boring the boiler.

Proof that the boiler can boil and proof that the burner is hot enough to boil.

Boring the lid. Which reminds me. Both the lid and boiler and blind holes, which means I'm first drilling them to depth and then boring them out. But I'm not really clear on how to drill a hole to an exact depth. Or even a rough depth. Some sources say to measure from the beginning of the full diameter portion of the drill. But that means I'll have a "dent" at the bottom of my hole. On the other hand, if I measure from the point then the bottom of the hole is much harder to bore than the rest of it, due to not having much space to insert the tool. Maybe I should try drilling (or at least finishing) these holes with an end mill held in my lathe's tailstock drill chuck. (Don't have a mill, but can get some good end mills in a variety of sizes cheaply.)

It's impossible to see here, but I put a thread relief on the inside end of this hole. There's not a lot of space in there...

Threading it. The thread for the boiler/lid combo is 1 1/8" x 12 tpi. The distance I threaded is about 1/8". Which means there's about 1.5 threads on each side. Because of the tiny distance (and in the case of the lid, the need to stand on my head to see the work), I did both of these with the lathe unpowered and rotating the countershaft by hand. (Actually, I could have put it into reverse for the inside threads, but I had enough confusion without having to reverse the normal way of doing everything, not to mention grind a new threading tool.)

And juuuust as I was feeling pretty proud that everything had worked (on the second try) and I'd gotten a fitting thread, I realized my stock was too short to permit room for the parting tool. So after first unplugging the machine and also putting some protection down on the ways, I sawed it off in place.

Lid and boiler, apart and together

And finally, here's how the boiler support collar holds the boiler, as well as an explanation for why those radial holes are in the collar.

 

[danstir]

Thanks for the fun build to watch. I have built a few wobblers, but never a steam powered one. I'll have to give it a try. Thanks for the inspiration.

 

[drysdam]

The lid needs two holes. One to provide an attachment point for the engine and one to provide steam pressure.

Then something I've never done before. Bending tubes. It would probably be simpler if I just used 3/32" wire here rather than tubes, but this is what I had. (Actually, I have wire but it's an ugly blackish steel rather than this nice-looking brass.) First, I cut them using an utility knife to avoid crushing.

Then into a tubing bender and fixture to control length. I would have preferred another style of bender but this is the only thing I could find that went down to 3/32". For my production run, I'll probably bump that up to 1/8" so I can take advantage of a wider range of benders because this system required tweaking. Although honestly, the bender was OK for what it was, it was my fixture that was lacking (hard to get a full 90° bend here, fixture hole depth not well-controlled, etc).

It does work, though. After I bent the first one I immediately wondered how I was going to get the tube out of there. But "screwing" it off worked perfectly.

Here we finally see how some of these pieces fit together.

I lit the fire and waited...and waited....and waited....but no boiling. Then I remembered I hadn't put any water in! (Why am I allowed to use power tools?) After filling it, it boiled in just a couple of minutes. There may be sealing problems betwixt lid and boiler but it was bedtime so I didn't pursue it then.

Next is building the engine itself, but first I have to do more translation and redrawing of the plans. There's quite a bit of Real Life coming up in the next few days, so there may be a pause of about a week before the next part is revealed.

 

[rebush]

drysdam: Coming along nicely. Looks great. No hurry I'll be waiting patiently for the next installment. Roger

 

[drysdam]

I was just writing up the threading post I mentioned above when I discovered a math error. For some reason, I got it into my head that 6/8 = 2/3. Since I've already cut the threads, I wasn't sure if I'd actually done it wrong or not (the difference is only a few thous, so I might not notice it).

I see in one of these pictures that I have written "2/3 * 1/12 = .063". But that's wrong, 3/4 * 1/12 = .063. 6/8 really is 3/4, so I seem to have done the math right and written it down wrong. *phew*

 

[drysdam]

Here's a link to how I threaded the boiler. http://david.rysdam.org/blog/2012/06/21/try-to-follow-the-argument-of-my-thread/

It's probably either old hat or wrong or something, but it worked. (Note that the post is a lot more complicated than the procedure.)

 

[drysdam]

I took a vacation (Niagara Falls! Mammoth Caves!), then came back and finished the engine. Forgot to take pictures of the progress.

THEN I couldn't get it to run. It runs really fast (actually, far TOO fast) on compressed air, but won't go on steam. Re-machined a part or two and it's closer, but still won't go.

The frustration of it is keeping me out of the shop and away from this forum, so I thought I'd just snap some "final" pics and put it away for a while to do something a little easier.

 

[kye]

hi drysdam,

this completely based off of a purely theoretical knowledge, and a liitle bit of not knowing too many of the details.
is it that the steam only being "wet steam" doesnt have enough heat stored in it to to maintain a gaseous form once it reaches the engine itself? theres quite a bit of surface area above the water level where it could be recondensing into water and the aluminium loves to conduct heat, will conduct it away from the boiler quite happily reducing the effectness of the boiler.

does steam visibly gush out of the exaust port when you manually turn it over? as this will eliminate the above theory. if not try heating the cylinder and frame alittle with a blow torch and try again, this will let the steam remain steam in the cylinder.

mackye

 

[drysdam]

hi drysdam,

this completely based off of a purely theoretical knowledge, and a liitle bit of not knowing too many of the details.
is it that the steam only being "wet steam" doesnt have enough heat stored in it to to maintain a gaseous form once it reaches the engine itself? theres quite a bit of surface area above the water level where it could be recondensing into water and the aluminium loves to conduct heat, will conduct it away from the boiler quite happily reducing the effectness of the boiler.

does steam visibly gush out of the exaust port when you manually turn it over? as this will eliminate the above theory. if not try heating the cylinder and frame alittle with a blow torch and try again, this will let the steam remain steam in the cylinder.

mackye

The frame and even the engine gets quite hot. Maybe not hot enough to prevent condensation, though. That's a good thought.

I have had steam (along with water) come out of the exhaust, but I wouldn't say "visibly gush".

And to be fair, I'm now a little scared of it. The pivot wasn't quite straight before, so I fixed that and this time when it got fully up to temp the steam force pushed the cylinder off the body. (I didn't have it screwed on, not having the right die size. More...jammed on.) I need to get a blast chamber to put it in for tests. I know a wobbler should be safe because the whole spring+cylinder will act as a safety valve, but I'm the nervous type.

It's probably working but I'm too much of a wuss to find out...

 

[lee9966]

Nice job on this, and thanks for the write up.

I now will have to build one of these! More on the long todo list!

Lee