Building Rudy's Steam Tractor

[Deanofid]

Boy, some sanitary looking work there, Dennis. All my fears of warped brass sheet have been allayed!
Good tips on wiring up the piece. I've just used a plain single wire strand, and always have to fight it to get it to stay put.

Thanks for the pardon, too..

Dean

 

[cobra428]

4156df,
Looks great, I used some rolled up alum screen door material in my stirling for a wick. Works good but needs cleaning/replacement after awhile. But what doesn't

Tony

 

[arnoldb]

Very well done indeed Dennis Thm:

Regards, Arnold

 

[JimN]

Really nice work Dennis.
I am still working on sheet metal parts, again thanks for making this,,,,how to for the tractor, I refer to this more than I do the plans.

JimN

 

[4156df]

Thanks again for your encouraging comments.

Tony...I'll give the screen a try.

Post #37.

Fuel Tank & Burners (Contd.)

As I said in my last post, there are a lot of different ideas out there on type, packing and placement of wicking. I played with a few variations and thought I’d share them.

By the way, I assume the bluer the flame the better (more complete combustion). If this is wrong, please set me straight.

The first test was to just use alcohol with no wicking at all. The fuel burned with a nice blue flame, but not very high, especially as the tank emptied. Also, it’s not practical because it’ll spill as the tractor is handled.

Next I tried vermiculite (you can get it at the garden store as a soil conditioner) as a wick. It burned with a very nice flame, but it’s also loose and will spill when the tractor is handled.

The third test was with cotton yarn snugly packed and extending about 1/8” above the top of the burner. If sheer flame volume is the answer this one wins, but I think the yellow flame means most of the fuel isn’t burning completely.

The last variation was to use cotton yarn, loosely packed and cut off flush to slightly below the top of the burner.

It gave a nice flame with lots of blue. Almost as good as the vermiculite but has the advantage that it won’t spill.

Here’s a short video showing the four tests.

[ame]http://www.youtube.com/watch?v=f8ZMeT2zmK8[/ame]

I had decided to go with the flush cotton yarn, but the more I looked at the video, the more I liked the vermiculite flame, so I tried containing the vermiculite with a screen. I cut a square of #30 mesh brass screen, formed it over a dowel, trimmed it and pressed it into the burner.

The screen works good for holding the vermiculite and, if anything, it enhanced the vermiculite flame.

[ame]http://www.youtube.com/watch?v=icnK8icS_ms[/ame]

This is the set up I’m going with (until I change my mind).

While I was at it I checked burn time. The tank holds 3 fluid ounces. With a full tank it burned an hour and 45 minutes. That’s much longer than I expected and much longer than I’d run the tractor. It’ll be interesting to see how long it takes to get the boiler up to pressure. If it takes too long, the first thing I would do would be to add another burner to each feed pipe for a total of four. There’s room for them in the fire box and it seems like more fire would be better. I’d also add a way to shut off the fuel. For now though, I’m sticking with the Rudy’s plans, otherwise I’ll never get this thing running.

I’m interested in hearing other builder’s comments on how their burners worked.

Regards,
Dennis

 

[DougLanum]

Dennis,

Everything looks great!

My tractor has some wicking material that was available years ago that my contain asbestos. It was put in and run for hours and I've not had to disturb it any at all. The wicking sticks about 1/8" above the burners. I don't recall the size of the flame but I'm guessing it is similar to your wicking material.
I don't think you would need to have 4 burners as two seem to be enough flame and heat to produce adequate steam pressure.

More thoughts, the fuel tank seems to hold much more fuel than you will need to use for the amount of water in the boiler. You will need to determine the correct amount of alcohol to put into the fuel tank to have it run out about the time you are out of water. Often I need to pick up the tractor, with rags or gloves and hold it above me so I can blow out the last of the flames so the engine does not keep "cooking". I have a small plastic squeeze bottle marked with the correct fill amount that I use each time to fill the fuel tank.

I think I had mentioned in the past that I made a small fan that I place on top of the stack when starting the engine. This keeps the flames and fire going the right direction until the engine has enough steam pressure to run the engine and the exhaust draft takes over. The fan draft also seems to speed up the fire up process greatly.


Keep up the great work.

Doug

 

[4156df]

Doug,

This will be useful information for me and for the other guys building this tractor. There is no operating advice what so ever in the plan set.

Your post has triggered a memory that somewhere on this board there's a post about running tests to time the fuel running out before the water does. I'll have to search for it and see if there were any numbers given.

Thanks for giving me comfort about the two burners. Also, the draft fan is on my list.

Regards,
Dennis

 

[Deanofid]

It sure works well, Dennis. That really is a long run time on the burner. You could roast a pig!

Dean

 

[JimN]

Nice work Dennis. In regards to wick material, I know someone on here gave a place where you could buy ceramic material to be used in burners. For the life of me, can't find that again, now that I want to check it out.

Considering your burn time Dennis, if you could put a water tank behind the tractor, might get as good a mileage as most new cars per gallon.....

JimN
Abbotsford, BC

 

[4156df]

Post #38

Boiler

The time has come to build the boiler. I’ve been putting the boiler off because I wanted to get more silver soldering/brazing experience but I’ve reached the point where it has to be in place in order to continue with the build. So here goes.

First off, I’m going to follow Rudy’s plans exactly. I figure there have been lots and lots of these boilers built and operated successfully, so if it’s built in a craftsmanlike way it should be a safe boiler. According to other builders, their tractors operate at 15-20 psi and with a 30psi safety valve this is a relatively low pressure boiler.

Quoting Rudy: “Before starting the boiler, it must be pointed out once again that the boiler must be built entirely of copper with all its joints either threaded or silver soldered.” Mine will be.

The boiler is fabricated from an 8” piece of 1 1/2” ID copper water pipe. The end caps are made from 3/32” copper sheet. The safety valve comes from Coles Power Models (www.colespowermodels.com) and is their part number 29M3-2. It has a 5/16-27 MTP thread and pops off at 30 psi.

The 5/16-27 MTP is an unusual thread (at least in the US) and the tap is expensive, however, it turns out that, for this size only, a 1/16 NPT pipe thread is the same. The 1/16 NPT is somewhat standard and considerably cheaper. If you’re not as anal as me and don’t feel like you have to make every piece yourself, an even less expensive answer is to just buy pre-threaded bushings from Coles Power Models. They’re about a $1.50 a piece.

I started by cutting the pipe to length and facing the edges.

The boiler heads, or end caps, are made from 3/32” copper plate. I drilled the bushing holes before cutting the round because it was easier to hold. Copper is a bear to drill. After rough sawing the round, I took it to the lathe and faced the edges.

The live center applies enough pressure to the disk to hold it against the chuck jaws for turning. (A tip of the hat to Bogs for showing this in his flywheel post.) I forgot to mention earlier that there’s an 1/8” longitudinal stay running through the boiler. That’s the stay hole the live center is in in the above photo. Also, it’s hard to see, but there’s a slight chamfer on the edge of the cap. That’s to aid silver solder penetration. Silver solder doesn’t like to flow over sharp edges. The cap is turned to a light press fit in the pipe.

The bushings are turned from copper rod. I left them un-threaded because I couldn’t come up with an easy way to hold them.

The above bushings are for the test valve and the pressure gauge. Bushings are also required for the safety valve and for the throttle valve.

The end bushings were soldered with “Medium” solder.

I used medium because I didn’t want to have to worry about the bushings unsoldering while I was soldering the cap in.

I should mention that I’m doing the soldering in multiple heats. An experienced solderer could probably do multiple connections per heat, but I wanted to be able to check things out as I went.

Anyway, the bushing joints turned out great and I was feeling pretty good.

However as we go along, you’ll see “pride goeth before a fall”.

Next the bushings were tapped 1/8-27 NPT. That’s the head, held in a clamp, held in the vise.

I’d never tapped tapered pipe threads before, so I had no idea how far in to run the tap. From looking on the web, it sounded like accepted practice is to run the tap in 12 threads or about three fourth’s of the tap length. If any of you can shed more light on this, please do. As it turns out, I could only get the tap in a little over half way anyway, but the fitting seems to go in okay.

The boiler has three water tubes on the underside. These are formed from 3/16 copper tube. I formed them using a piece of aluminum with a 3/16” x 3/16” groove in it.

The aluminum is 1” OD, so the groove bottom is 5/8” OD. The groove keeps the tube from collapsing.

Make three tubes, all shaped the same. They'll be cut to final length when they're fitted to the boiler.

The six holes for the water tubes were drilled on the mill using a 3/16” end mill

I chose to do it on the mill, because the water tubes extend parallel to each other rather than radially. That requires drilling off the center line of the boiler which is almost impossible with a drill bit. The end mill holds its position better. (With this set-up, I also drilled the holes for the two bushings that go on the other of the boiler.)

The water tubes enter the boiler at about a six degree angle, so the vertical holes had to be deformed to allow for this. First I annealed the boiler pipe. Then I inserted three pieces of 3/16” drill rod into the holes. The rods are vertical at this point (sorry, no photo). Then I pushed all three rods down at the same time to the required angle. You’ll want to over bend slightly because the drill rods bend a little.

These are the resulting holes.

I need to stop here for now…more later.

Regards,
Dennis

 

[vlmarshall]

What an interesting-looking boiler... this is great. ;D

...the bushing joints turned out great and I was feeling pretty good.
However as we go along, you’ll see “pride goeth before a fall”.
I need to stop here for now…more later.

AAAHH! The suspense! No fair, man.

 

[Deanofid]

Oh.. Dennis, I wish you didn't have to stop. I really enjoy boiler builds.
Arnold has his about done for "Fred", so, yours is my only boiler "fix" for the day.

Dean

 

[Powder keg]

Top shelf work so far ;D Thanks for posting!!!

 

[arnoldb]

Good going Dennis

“pride goeth before a fall”

Are you referencing the bit where the solder didn't completely form a fillet in the photo where you are tapping the bushing ?

Kind regards, Arnold

 

[zeeprogrammer]

Great post. Glad to see the stuff about the burners. Very nice.
Good tips from Doug too. Thanks.

 

[bearcar1]

Denny, you're knockin' me out here man! Great work and I have truly been enjoying this ride, I'm sure there have been some bumps encountered along the way that we may never know about but so far this has been fantastic to follow. I am GREEN with envy here. And once again thanks for sharing your adventure with us. :bow:

Cheers
BC1
Jim

 

[phlegmatic]

First class job! And you get many bonus points for using Sherline machinery!

 

[4156df]

Thanks for the comments. I didn't really mean to build any suspense, or imply that there's a major disaster upcoming (although there probably is). Just the normal run-of-the-mill screw-ups. I'll get off my duff shortly and get another post going but I wanted to answer Arnold regarding the void he spotted.

When I made the bushings, my tool had a slight radius on it so the bushing flange doesn't seat tightly against the boiler head. However, there is a good, snug fit between the head and the part of the bushing that runs through the head. The solder joint around that part has a complete fillet on both the top and the bottom. I was actually surprised that the solder filled as much of the gap as it did, because it's ususally not very good at gap filling.

Arnold, thanks for mentioning this. I should have commented on it in my post.

Regards,
Dennis

 

[arnoldb]

Thanks for the clarification Dennis No worries then; the little "run-of-the-mill" oopses happen.

Kind regards, Arnold

 

[4156df]

Post #39

Boiler (Contd.)

At this point all of the boiler pieces are fabricated, so all that’s left is silver soldering and testing.

Up until now I have been using a propane torch for silver soldering, but recently found a used Prestolite air/acetylene torch similar to those used by air conditioning and refrigeration people. It burns hotter than the propane and has a much softer flame so it doesn’t seem to move the solder bits around as much. So far I like it and it’s what I used to silver solder my boiler. I’d say it’s nice to have, but the propane torch would have done the job too.

I did the boiler in multiple heats with a pickle step between each heat.

For the first heat I soldered the throttle valve and safety valve bushings to the top of the boiler. They were done just like the bushings on the end cap, so no photos.

The second heat was to solder the exit end of the water tubes.

The tubes are held in position for soldering with stainless steel binding wires (the wires are shown in a later photo). The boiler is nestled in the hearth and insulated with heat reflective bricks and tiles. The joints are fluxed and bits of solder are in place.

I fooled around quite a bit trying to decide how much of the boiler to cover and how much to leave exposed to the flame. I ended up as shown above. I left the top tiles off and pre-heated the boiler, then put them back as shown, and concentrated on the exposed area. It worked okay and the boiler got up to solder temp reasonably quickly.

You can see that the flux really did its job. The binding wire (one per tube) that holds the tubes in position for soldering is visible on the left side of the above photo.

The joints after pickle (citric acid).

I probably erred on the “too much solder” side, but the joints look good on both the inside and outside so I’m happy.

The entrance end of the tubes are soldered in pretty much the same way except I used a silver solder pre-form around each tube.

Notice the binding wires are still in place. They’re stainless, so there’s no problem with putting them in the pickle.

The joints came out nice, with a good fillet on the inside.

Still some problems with solder control. Is it because I’m fluxing too wide an area??

The next heat was to do the end cap. For some dumb reason, I decided to try applying the solder in wire form after the boiler was up to temp. Not a good idea. Between being up tight about soldering in the first place and worrying about the cap dropping down into the tube I was shaking so badly I ended up with solder everywhere. I’m not proud of this one.

Fortunately there’s a nice fillet all the way around on the outside and the inside so mechanically the joint is good even if it’s not pretty. If the price of silver keeps going up, I may have to melt this down for the silver content!

On the other end cap I went back to pre-placed solder bits.

And ended up with a neater joint.

This joint can’t be examined from both sides but the fillet on the top looks good all the way around so I should be okay.

The last part is to add the longitudinal stay. It’s an 1/8” copper rod, threaded 5-40 on each end with a brass nut bearing on the end caps. The threads extend about 1/4” beyond the nut and are used to hold the boiler in place in the boiler housing. This is the one place soft solder is used and it’s done at Rudy’s instruction: “…run a brass nut up on each end. The threads will do all the holding so you can run soft solder all over the ends of the stay to seal it in. In this case, the soft solder is used only as a caulking compound.”

After getting the stays in place and sealed, things turned a little sour. I had forgotten to tap the bushing that holds the safety valve. It should have been done before the end cap so the swarf could fall out, but worse than that, when I went to tap it, I managed to mangle the threads. The upshot is that the bushing had to be unsoldered and replaced. I didn’t have any more copper rod, so I ordered a tapped bushing from Coles. Luckily, the old bushing came out fairly easily and after a re-pickle, the new one soldered in nicely. The only snag was that in the pickle the soft solder used to seal the stay turned an ugly black. It cleaned up fairly well, but you can still see some discoloration.

Anyway, here’s the boiler ready for testing.

Thanks for following along.
Regards,
Dennis