Hardened expansion links?

[87gn@tahoe]

CNC would also allow for the suspension points to be machined into the part rather than needing to attach them later. The York engine has pretty good geometry in the link and there isn't very much movement. Also with the piston valve there isn't any pressure holding the valve to the face and causing a bunch of drag like on a conventional non-balanced slide valve, reducing the "hammering" of the die blocks and/links.

See video for link movement detail:

[87gn@tahoe]

I forgot to mention though that the links on my engine are worn enough from running at 700RPM for who knows how many hours in low lubrication conditions. I now have to run her linked-up one notch so the dieblocks ride in the less-worn area of the links, reducing chatter. I will get around to taking a shim out eventually...

[marinesteam]

The links are on the CNC as I type this. Our in-house CNC machinist wanted to do them. I'm having the profile done without the slot. I'll complete the brazing of the drag link pivot before the slot gets put in to reduce the risk of the slot closing up. I'll post pics of the profiled parts when they are done

Ken

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[marinesteam]

Here is the profiled expansion links and the pivot ready for brazing.

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Probably will not have a chance to get to the brazing until July due to an upcoming trip to the UK.

Looking forward to getting to meet some fellow steamboaters on the trip.

Ken

[fredrosse]

It appears that there is a close fitting groove milled into the pivot part where it mates with the expansion link. That close fitting joint would be an ideal application for silver soldering, as opposed to brazing. The silver solder would flow well into the joint, and has a strength beyond 40,000 PSI, far beyond brazing materials.

Brazing allows producing a well rounded fillet (perhaps 1/8 to 1/4 inch radius of fillet), but that very character usually results in a joint that does not have good penetration throughout. With a close fitting joint and silver solder, you will have a rounded fillet ranging from almost no radius to a little less than 1/16 maximum radius at the joint with a generous amount of solder. The rounded joint here will be very uniform all around the perimeter, and require no clean-up finishing to look perfect.

Be sure to use genuine silver solder, 45%, 50% or 56% (I would use 56%). There are "silver brazing" rods also sold, usually with a much smaller percentage of silver in the alloy, but this stuff is often appropriate only for brazing copper, not steel.

[marinesteam]

Fred, I think you have your definitions mixed up.

Brazing - The American Welding Society (AWS ), defines brazing as a group of joining processes that produce coalescence of materials by heating them to the brazing temperature and by using a filler metal having a liquidus above 840°F (450°C), and below the solidus of the base metals.

I was using braze correctly as the type of joint isn't determined by the type of filler metal but by the temperature at which the joint is made up.

I will be silver-brazing the assembly using All State 155 filler (56% silver) and All State 110 flux. I find this is a great combination for use on both ferrous and non-ferrous materials with excellent capillary flow. The listed tensile strength is up to 50 ksi and the working temperature is 1150-1200 °F.

The joint is close fitting to be self aligning and still leaves a .001-.002 gap per side.

Ken

[fredrosse]

Sorry about my error here, but it looks like we both selected the same 56% silver stuff.

I was thinking of "brazing" as a torch process which is worked with soldius material, usually a brass alloy rod. With that material you can make fairly good fillets, but bringing the material (and mating parts) to the fully liquid state often results in burning out the zinc component of the alloy. The 56% silver alloy goes from solid to liquid with very little temperature difference, and then penetrates the joint very well.

[marinesteam]

The popular nomenclature doesn't help matters either. Bronze rod is usually referred to as brazing rod but the sheet or coil used for silver brazing is still referred to as solder but the process is defined by the temp. Don't get me started with how brass and bronze are defined. You'd think that the zinc or tin would be the defining factor but that's not always the case.

The yellow filler materials do tend to leave a nice fillet and can be used to fill as well. Used to do a lot of bicycle frame repair where you repair stripped bottom bracket threads by building up bronze then retapping. That was way back when bicycles were all made using steel.

Cheers

Ken