Pontiacguy1 wrote:Just a curious question: Why do you call it 'swarf'? In my industry, swarf is defined as the leftover materials from grinding operations, which are mostly filtered out of the coolant. It consists of steel from the grind, abrasive from the wheels, and some amount of coolant. It also looks like grey foam rubber, but wet. We always called metal turnings just that: Turnings or quite possibly just chips.
I am just curious, as I see you are from Canada I thought maybe the word was used differently up there.
I think you will find that "swarf" is the common term in the United Kingdom for what we call chips here in the U.S.
In regards to the term "swarf", I agree, it's terminology that has an origin out of the US, at least as it applies to large particles as are removed in the machining process. Here, they are recognized as chips. Take note that one is not offered a "swarf remover" for CNC machines, but a chip remover is offered. Swarf is recognized as suggested, the waste material generated in grinding.
Want something else to ponder? How about the word tram, for dialing in the head of a machine, or a vise. I've been in the commercial shop arena since '57, and NEVER encountered that term until I got online. One never "trammed" the head of a mill---it was dialed in.
I expect the term tram was stolen from the days of steam, when tramming an engine implied it was being properly timed, via the use of trammel points.
Harold
Wise people talk because they have something to say. Fools talk because they have to say something.
Next up was to attach the top cross channels to the tender truck side frames in order to join the individual side frames together.
The Martin Lewis prints show two channels which seem to indicate rivets but there are no details given. As the cross channels themselves are structural members, their attachment has to give the truck its strength and stability as well as the ability to withstand all sorts of twists and bumps, the full tender weight itself and probably some abuse during its working life.
How to do it?
More research finding out how others did it seemed to be the answer.
After a lot of investigation I found three separate models with the same or similar trucks.
Photo No.1 shows the extended top cross channels placed on top of the tender truck side frames and bolted down into each side of the double sided side frame. Practical but not as per the Lewis drawings.
Photo No.2 shows an all bronze (or bronze/brass) assembly where the two top channels have been brazed directly to the side frames. I can't braze so...
Photo No.3 shows someone made up an all steel truck instead of using the Lewis side frame bronze castings and as a result could have an all welded assembly. Very strong however, I have bronze side frames and HR steel top channels.
Of course, I could re-invent the wheel and I think I did!
Since I can silver solder, I asked an authority no less than Bill Huxhold if this could be done. Bill said that if the bronze will silver solder by itself and the HR steel will silver solder by itself, then the bronze and the HR steel will silver solder together. That was the good news.
Then I got the bad news.
Another very respected TSME member who also builds locomotives looked at the side frames and asked if they were made from 660 bronze. I said likely yes as this was the widely used alloy of years gone by.
The member said you will get a beautiful looking joint which has little structural strength and is good for decorative soldering purposes only. For his locomotive, he had conducted a series of tests on various bronzes which indicated that for structural silver soldering of bronze, one has to employ a phosphor bronze alloy having less then 2% lead and preferably 0% lead. Such material is available in the UK but when he called suppliers all over North America and got into the technical details of what he wanted to do, nobody would commit to their bronze stock.
His series of tests were pretty severe as he whacked many bronze bars into a pretzel with a hammer and if the bronze itself broke before the silver soldered joint did, it was deemed to be structurally sound.
This set me back but after a long period of pondering (Richard says that the thinking part of how to do something is the most important first step), I came up with method 4 for this hybrid bronze/steel truck frame.
Stay tuned.
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Last edited by Carrdo on Mon Aug 10, 2015 4:19 pm, edited 3 times in total.
This criticism of SAE 660 (aka CDA93200) is mistaken. This type of bronze has been used sucessfully in the model engineering field for many years as boiler bushings, which are silver-soldered into copper boilers. Why it wouldn't work for a frame is beyond me.
What might be a point of confusion (and be the cause of low-strength joints) is the use of this material with "silver-bearing" solders, which have a much lower melting point and strength than high-silver content solders.
Personally, I only use phosphor bronze in any fitting(s) which are to be directly silver soldered into the copper sheets and wrappers of a copper boiler but then I am very conservative.
My experience with silver soldering has also taught me not to try and silver solder any alloy with a high lead content.
The spec. sheet which I have for SAE 660 Bearing Bronze gives a lead content of 6-8%.
Knowing the person who did the tests, this person has had a lifetime of machining experience working in and for industry as well as locomotive model making. He knows the correct silver solders to use (the high silver content ones).
I/he am not saying that a 660 joint has no strength, it has low strength and the strength which it has comes from the fillet only and not from the entire chemically "wetted" contact area. It is possible that for round bushings, the fillet alone will give sufficient strength but I wouldn't want to rely on it alone. I am trying to bond flat surface areas as I will shortly describe.
Sometimes the proof of the pudding is in the eating. Just take a couple of small pieces of 1/4" dia. 660 rod, silver solder the ends together, put the sample in a vise and bash one end with a hammer and see what happens. It is not a scientific test but it is an extreme test for bending and impact.
[*]To re-invent the wheel, I came to the conclusion that if I silver soldered solid steel HR end plates onto each end of the cross channels, I could then drill and tap through the inner frame wall of the double walled side frame and through the cross channel end plates with high strength cap screws to make a solid high strength assembled unit. In addition, the cap screws would never bee seen as they would be buried in the space between the inner and the outer frame. I could do this as the side frames themselves are built up units which can be assembled and disassembled at will.
This approach would result in a finished frame which looks as per the Lewis drawing.
The first photo shows the silver soldering setup.
I did run into some problems entirely of my own making as my major silver soldering equipment is still at McJannetts (MPP) where we are silver soldering the 1" scale Yankee Shop Atlantic copper boiler. This left me with some small hand held propane bottles and torches to work with. Ignoring my own experience, to sock all the heat you can to the parts getting the entire area a bright orange heat before attempting to add any silver solder to the joint, the solder did not flash into the joint at first. Also, the boiling flux had pushed the parts apart. I know better but...
The silver soldered joints came out fine in the end but I had to push the hand held bottle torches to their limit. Not recommended. Use properly sized commercial/industrial grade equipment.
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Last edited by Carrdo on Mon Aug 10, 2015 4:19 pm, edited 1 time in total.
The first photo shows the setup and all of the tools used to locate and mark the position of the top channels on the side frames. It is a bit awkward to do and involves a bit of fiddling.
The second photo shows the machining of the cutout on the ends of the cross channel end plates needed to have the top channels clear the side frames peripheral flanges. I don't like using any cutters smaller than this as I should run them faster than my mill's spindle will permit and sooner or later (usually sooner) they break.
The third photo shows the frame assemblies with the top cross channels temporarily fixed in place and the wheels and axles ready for pressing. I always use a high pressure lube when pressing and I also put a tiny chamfer on the wheel axle bore which will be pressed against the shoulder of the axle using the large countersink turned by hand as shown in the photo. I use all mechanical press fits whenever I can as I have the equipment to do it this way.
The fourth photo shows the actual pressing operation. I have a large, well known American made ratchet arbor press and it makes jobs like this SOOO nice but be careful with the pressing pressure. Ensure that everything is square and is centered under the ram first and then press very gently until the wheels just bed against the axle shoulders.
Things are finally starting to come together.
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Last edited by Carrdo on Mon Aug 10, 2015 4:20 pm, edited 1 time in total.
The photo shows the setup for profiling the wheel flanges between centers, the third and final stage in turning the wheels. I did make a form tool for this but it proved to be futile. The setup was just not rigid enough to prevent serious chatter from occurring the moment the cutting tool engaged the wheel. In the end I just filed the wheel flange rounded end checking it against the radius gauge shown in the photo.
Initially, the compound was slewed 10 degrees to each side as seen in the photo to machine the 10 degree taper lead in. I could do this at the headstock end when the lathe was in the lowest back gear but serious chatter was encountered at the tailstock end so the axle was reversed end for end to do each wheel in turn.
Coarse file, fine file and then finish/polish the flange rounded end with a bit of 220 grit emery paper.
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Last edited by Carrdo on Mon Aug 10, 2015 4:20 pm, edited 1 time in total.
