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I feel your pain with silver solder. I believe in the highest silver content is important, stronger and flows best. Also melts at lowest temperature. This stuff is on Amazon but pricey. Most welding stores have something like it.

Radnor saftey-silv 56
I feel your pain with silver solder. I believe in the highest silver content is important, stronger and flows best. Also melts at lowest temperature. This stuff is on Amazon but pricey. Most welding stores have something like it.

Radnor saftey-silv 56

Vietti, take a closer look at his photo, it doesn't appear there was any flux at all ?
Vietti, take a closer look at his photo, it doesn't appear there was any flux at all ?
Hi Peter,
I used Harris STAY-SILV black high temperature flux, Harris SAFETY-SILV 56 brazing alloy and map gas turbo tip. I had success earlier when brazing small components such as the 5/32 SS valve spindle on this project in an earlier post. Copper and brass seem to be no problem. I brazed the 5/16" brass tube headers on my Demon V8 build along with brass rocker arms for a Panther Pup build. I always clean and wipe with acetone before fluxing.

I am reconsidering purchasing an air/acetylene turbo torch setup for a "B" tank and trying again on some non critical ferrous parts or just practice on scrap. I've used this setup to braze 3" medical gas piping in hospitals in a previous life. The map gas setup can only braze up to 3/4" copper tube. Some of the issue is the relative low thermal conductivity of steel and the flame being swirly and not focused. Once one redirects the flame to a different side, air will oxidize the other side, and you are done. Nothing will stick to the oxide.

I was able to salvage these parts with a new shaft, and had success TIG brazing them nicely. Still working on the contouring and finish. Will post pictures later

Thank you for your tips and suggestions:)
I'm not sure how it works with acetylene/air, but with oxy/acetylene, you can make the flame slightly carburizing and it helps keep the surfaces from oxidizing.
When I first started silver brazing, I read a description of a "long, soft carburizing flame". Don't know where that was from, but it has worked well for me. I use Harris Safety-Silv 56 also, but with the white flux.
I use any or all of paraffin, petrol, butane or propane torches for silver soldering. I think MAPS Gas is as hot as any of tese, but depends on the size of blowlamp. Maybe you just need a bigger nozzle and jet? BUT, the most significant is how you cover the part to keep the head IN. Cover most of the length with a piece of firebrick (or dry sand) so only the joint is exposed - much easier to get it hot then.
FWIW, I used Loctite for the rods while the rockers were aligned on a surface plate. You could pin them afterwards, but really not needed.
not sure what went wrong,
but there's no way mapp-gas didn't have enough heat,
I've silver-brazed much larger pieces with mapp-gas,
sometimes I'll place a fire-brick behind the work to reflect the heat back in,

I'd throw out the black flux (its for brass-brazing, not for silver-brazing)
with white flux it turns transparent after it all melts and you can see
clearly whether the metal is clean or not and where the silver is flowing or not.

also paint the entire work in flux before starting so that parts you aren't yet
working on don't get oxide coated (which sometimes comes off with
additional flux, but if it does it usually takes an inordinate amount of flux),
also have a "scratch rod" (1/16 or so steel rod, pointed at the end and
last 1/2" bent 90-deg) on hand to push the silver around and get it to
wet to the parts if you're having trouble with that.

I always recommend against Oxy/Acet, its too hot for silver-brazing, you
run the risk of melting your pieces and/or burning the zinc out of the silver alloy.
and mapp is so much easier, just one knob to adjust the heat, with Oxy/Acet
you have to choose the right size tip for the amount of heat you want, and
play with the knobs to get a neural flame, you can't play with the knobs
for the amount of heat you want.

HTH, keep up the good work, love your Muncaster !!!


PS, not just writing for you, but also for other folks having issues with silver-brazing.
Thank you for the comments and tips. I will try the white flux next time, seems I was misinformed about the dark flux by the label and other forums. I think my new "hard" fire brick may be robbing some heat input as well. Steamchick suggests the insulated properties have a large effect. Perhaps these flat edged parts are transferring heat at a faster rate than the rounder parts I have had success with. I will experiment with soft insulated fire brick keeping all other parameters equal to see. I'm going to silver braze the valve radius rods after this part.
Harris flux.jpg

Anyway, the TIG brazing was wildly successful and gave me nice bronze bearing nubs at each end.
TIG Brazed.jpg

The part was then center drilled and machined in the lathe to cleanup the shaft. I didn't photo it, but I then squared the edges relative to the shaft and removed the bulk of the material in the vice.
machine journals.jpg

mill sides.jpg

Then I used ideas from other builders, (thank you KVOM and Simon from MEM) to build a set of clamping blocks so the part could be contoured. This is mostly aesthetics as this part is atop the engine, but clearance is also needed to the rods as the trunnion swaps between forward and reverse operation.
fixturing blocks.jpg

table setup.jpg

The radius point was centered on the table by the witness mark in blue dykem. I then re-slotted the keys, and started rotating the part 10 degrees +/- and recording the x-axis final values. Not super scientific table like Simon did, but to make both parts equal. I used "precision" angle block set as it was faster than my digital angle finder.
keyway slot.jpg


Then I filed away with the sorriest set of needle files ever sold by Harbor Freight. These sets are only $5 and the previous set was halfway decent and used for 4 years. This set had suggestions of teeth but were not very sharp or deep. Ordered a set of Nicholson files at 8X the price and will test them today.
after filing and sanding.jpg

new files.jpg
also paint the entire work in flux before starting so that parts you aren't yet
working on don't get oxide coated
Thank you Peter,
Coating more of the part and using insulated brick helped. Have to order some real insulated fire bricks, this stuff is actually calcium silicate pipe insulation and it falls apart above 1000 F. I think I had the torch cranked up too high previously when I did the valve rocker and blew the flux away. The two parts I did today came out much better using significantly less gas.

Here is the finished valve rocker after a few hours using my new needle files and the buffing wheel with black and green sticks.
valve rocker polished.jpg

The little pivot arm was made out of three pieces to practice silver brazing. First one broke the joint in the milling vice. Second attempt was much stronger and was the one I keywayed and put in place.

Here is the engine so far. Probably sort out how to machine the bronze shoes that bolt inside the valve rocker next.
Raveney, your finished rocker looks b.e.a.utiful !!!
I always enjoy rotary-table work, you've given me another excuse to use mine !

another possibly helpful trick --- silver-solder doesn't stick to titanium so you can use it to hold parts together without them becoming part of the piece, the only issue I've had with this is you can't use for example a 1/8" titanium rod in a 1/8" hole, the titanium rod needs to be 10 to 20 thou underside or else it becomes problematic to get it out even though no silver-solder stuck to it, I broke my starrett 1/8" drive pin punch (because I accidentally hit it at an angle) trying to overcome what becomes a press fit when a gap that is too small fills up with oxides and flux residues.
Hello again,
Last weekend I made the valve rocker "shoes" out of a 1/4" piece of scrap brass shim-plate. I sure hope that the estimated radius of 4.050" is correct as several pieces will need to be remade if it isn't. Milled the radius slot on the rotary table on both sides because of the limited width of the scrap piece.
brass shoe radius.jpg

Then sliced up roughly even arc segments on the improvised table top band saw.
shoe slices.jpg

The blanks were then scribed with a tangent line and set in the vice with the line touching a parallel and milled to just above the line.
shoe tangent.jpg

I then raised them and milled sides until there was an even amount of material above the milled arc at the design length (red arrows).
shoe length and deck.jpg

They were then flipped and brought to final width (0.375"). Each shoe was then drilled and tapped 4-40.
shoe tapping.jpg

I fit them into the valve "rockers" and secured with Philips screws, but didn't like the look. I ended up making hex head bolts later to match the other fasteners.
shoes with phillips.jpg
The next parts to make are the little guides that run inside the milled arc on the brass "shoes" and the potentially ignominious upper links. The upper linkages are not dimensioned on the Muncaster plans. Most probably due to numerous dimensional tolerances that affect them working correctly. I researched several sites and articles on steam valve linkages, and drew the valve linkage using CAD. Hopefully it works out, and here are the dimensions I came up with for a 0.6 scale model....
upper link plan.jpg

I chose some crappy A-36 plate that was well seasoned with hematite on the off chance that they worked out. Milled to size using a well worn and resharpened 1/2 endmill because of the hard oxide. Then used a good 1/4 endmill to make the slots, flipped on edge and touched a 3/8 ball end mill to add a rubenesque feel to them. 🤭I didn't fully radius the ends, and have some clearance issues (red arrows) there that should go away once I profile them.
upper link milling.jpg
upper links.jpg

I thimkpf the hex bolts look much nicer (blue arrows) and solve the problem of properly tightening the inner pair of "shoes" down.
shoes with bolts.jpg
Raveney, the radius of those curved trunnion blocks isn't all that critical, it should be roughly equal to the length of the "radius rod" (guess where that name comes from!), being a bit off just means that at the zero setting for the forward/reverse lever there might be a tiny bit of steam let into the cylinders if you turn the crankshaft to just the right spot, but not if there's some "lap" in the valve versus the ports. Looking good !!!
Thank you for the likes and comments

Estimated the radius rod at 4.050 by centering the valve over the steam ports and measuring from the valve spindle eyelet to center of the trunnion, and then followed your lead on the radius in the curved trunnion blocks.

I believe there is a lap of 1/8" the way the valve and steam ports are cut, so we should be within tolerance. 🤞

Interferences were a bit more than initially thought, and had to file most of the day on the rockers so the upper links didn't hit when the assembly was at FWD/REV elevations. I have +/- 0.400" on the vertical adjustment after filing. Mr. Muncaster dimensioned a total of 0.75" scaled (1.25" full size) so we should be good.
Muncaster sketch.png
Raveney, I've never liked the "screw" adjustment for the forward/reverse operation as it would take forever to change it, I'm thinking that on mine it will be more like the Johnson Bar (American terminology, Reversing Lever for Brits) on a locomotive,
I was also thinking of that because I have been researching Case Steam Traction Engines as the next project, and that's what they used. Never knew it was called a Johnson bar. In construction, a Johnson bar is a heavy metal bar used for prying on and digging out rocks. I thought the name was because you risked a hernia by pulling too hard.

The next few parts were silver brazed using my new insulated fire bricks. They seem to help a lot. I made the radius rods out of SS and need some more polishing based on the pictures I just posted. Also started the reversing screw/shaft. Used 10-24 thread so it would change direction faster. I think I should make a speed handle also on the wheel.

Not much left really....
a) piston rings (might try without)
b) exhaust pipe
c) steam inlet valve
d) gaskets and packing
e) paint

I have a PM research horizontal boiler, condenser and feed pump that I will use for the steam trial
Now that all the motion parts are complete you can check the timing and adjust the valve movement. Looks like the hole in the side of the base to anchor the bottom of the reversing mechanism is still TBD.
Now that all the motion parts are complete you can check the timing and adjust the valve movement. Looks like the hole in the side of the base to anchor the bottom of the reversing mechanism is still TBD.
Good eye KVOM
Yes I was holding off on drilling the lower mounting hole until I completed the reversing wheel. It runs on air and reverses direction so I disassembled everything, drilled the exhaust hole and made the exhaust pipes and elbow. I only made a top cover gasket thinking that I would use high temperature gasket maker on the valve plate and cylinder end plates. I also decided to go ahead and paint while it was all tore apart.
Your build log was very beneficial to me so thank you for following along :)
I'll post a video once it's put back together and running.

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