Bog's Paddleduck Engine

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kvom:
I had a full afternoon in the shop making the front and back plates for the steam control. It took a lot longer than I expected as I had to turn both pieces down from 2" brass round, and I wanted to keep the waste of material to a minimum. In addition, the boss on both is a close fit to the block, so some attention and repeated measurements took time. I had located a 1/4" ID by 3/8" byt 1/16" O-ring at the local hardware store this morning, so I had what I needed.

Here's the assembly:

I didn't have any 6-32 SHCS so had to use these for the trial fitting. I had been thinking of using stud and nuts here, but standard 6-32 nuts are too large and inerfere with the shaft.

The rear cap turned out to be a press fit to the block, so after screwing it in tio align the holes I pressed it in with the arbor press. I don't see it coming out again. I realized at that point that this part is unnecessary if you have the ability to bore a blind hole in the block for the spool.

Once I could measure the depth of the hole and the size of the boss on the front cap I could mill the spool to length. I probably cut it too close as once the 4 pieces are fastened tightly together there's a lot of friction; I can turn the spool holding it with pliers, but not with finger pressure alone. I imagine there is friction between the end of the spool and the bottom cap as well as the sides and the o-ring pressing against the front cap. Once I make a handle I'll be able to assess if it's too tight.

Here's the parts disassembled. I still need to mill the slots, pending some thoughts on other dimensions.

On the soldering front I located local sources for both firebrick and citric acid, so tomorrow I should have everything needed to get started. The first joints to be attempted will likely be the eccentric straps to the linkage blocks.

kvom:
Following the recipe in Chapter 5, I made an attempt to SS two scrap pieces of brass together. The good news is that they are in fact together. However the fillet is not as pretty as could be wished:

In fact it seems that most of the solder remained outside of the joint. The rod is 1/8", and I created a chamfer on the hole with a deburring pen. I'm wondering if either the chamfer was too small or I used too much wire, or the wire wasn't tight enough to the joint. I found that getting a loop or the wire around the rod to be awkward.

I took the piece out of the pickle after 1 hour to take the pic. Can I assume that it will be easier to clean up if I leave it in longer?

bogstandard:
Kirk,

Looking at that, too much flux and maybe a bit too much wire, but because it hasn't penetrated the joint, it might be the correct quantity.

Silver solder requires a gap of approx 0.002" to penetrate down to join the parts together.

With tubing make it a slight slack fit, and very gently flatten the end of the tube into a slight oval. This will make it tight in the hole, but allow the solder to penetrate.

Do the same with solid rod or whatever, but tap the rod with a hammer or centre pop to deform it slightly (only on the area inside the hole, so it will not be seen). Again this will hold the rod tight, but allow the gap.

I normally paint a tiny amount of liquid flux down the hole, and only on the very end of the rod or tube and assemble them all together. You should only see a tiny amount of flux on the surface.

Wrap the wire around the rod or tube like a spring, and cut along it's edge. This will give a series of rings that will easily slide down the tube or rod, flatten them straight before use, you should be able to do it with your fingers, locate it down against the hole. Just use one ring for normal, two rings for a deep hole.

Do not play heat directly onto the flux or solder, only onto the main part, in your case the big bit of brass, somewhere around the other hole, or the end of the metal hearest where you want the joint, and watch the heat travel towards the required joint. As it heats up, the flux and solder will melt and flow into the gap around the two parts. As soon as you see the nice fillet form, take the heat away, wait for a few seconds and then drop it into a quench tank or your pickle bath. Half an hour in the pickle should leave the job completely free of flux and maybe a bit of copper plating over the job, this should easily be polished off.
If the part gets to bright red heat, you've cooked it. Usually a dullish red is sufficient for the main component.

These instructions are for the special flux and wire I have sent to you, other fluxes and solders might react in a totally different way. Especially plain borax, it is not worth even trying, you will never get a perfect joint with it. OK for the 1950's, but not modern day materials and solders.

The main problem with silver soldering is usually too much heat, too much flux and too much solder. Use the minimum you can get away with. If it is not enough, you can always put another drop of flux and a ring of solder and reheat. Just always watch for when the solder flows.

Hope this helps, if not, maybe a change in technique for your style of soldering. You will get it eventually, and once you do, it should be with you for life.

John

kvom:
Thanks. I definitely had a lot of flux, and also had the flame too close to the joint. I'll try again tomorrow.

rleete:
Kvom,

I've never silver soldered, so take this with a grain of salt. However, having read Bogs post above, and having done more than my share of "regular" soldering (mostly sweating pipe joints), I think it sounds very similar. It's one of those things that takes a bit of practice to get a nice looking and solid joint. It takes time to learn how the heat flows, and where is best to apply it, and how much solder/flux to use.

When my dad first taught me, the pipes stayed together, but they looked terrible. Scorch marks all over, dripping solder, and the possibility of burn marks on the surrounding materials. It also took twice as long as he did it. Nowdays, after 30 years of doing it, I can put most 'professional' plumbers to shame.

The one tip that I took out of Bogs post that struck me the most was the use of flux. Apply it only where you need it, and use it sparingly. That, too, will become more apparent with time and practice.

All that said, I thing you're doing a helluva job on this engine, and a very professional writeup.

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