Berkshire tender Brake cyclinders

[gcarsen]

I got the little task of machining up 3 brake cylinder kits a couple years ago, but life , having a little boy, got in the way, then a little issue cropped up in the work that put a little damper on the project, will be a little long winded but fell some of you might like this one!
ok, got 3 sets of castings from Jim, and as usual very nice castings!! nice detail, no flash, or dingle berries. the smallest hint of mismatch from the foundry( minimal a few thousandths!!) the way Jim does his patterns follow a machinist intuition to machine them, stock where there should be, finish surfaces where its appropriate, so you end up with parts that follow prototype looks and finishes pretty well!
ok, start with the cylinder body, went down to the engine house, the 700 has one very close and you can see where they are machined, and where the cast surface is left.
looked the casting over very well, figuring the best way to machine it,, checked with calipers here and there, compare to prints, looking at the bore core in the casting, it was very clean, and pretty true to round, and true. dug out my set of adjustable mandrels, slid it in, tightened it up, set it in the lathe and spun the part around. looked very true! checked a few things with the indicator and liked what I found, all 3 where this way! by the way, this style of mandrel are very handy!! will basically fit any size, and hold very well for machining!
took a cut one each end with out removing the casting, use a right , and left hand tool on each appropriate end, we want these 2 surfaces to be parallel to each other for next steps. measure end webs, balance the stock and cuts till the ends are clean. they finished a few under, nothing important! face as close to the mandrel as you can with out touching, remove, debure the last little bit off. rub across a stone, or sheet of sandpaper to be sure ends are completely flat, double check that they are parallel to each other as this sets up all further machining!

[gcarsen]

now to the mill, to mill the mount pads, and drill the mounting holes,
put the body in the vise with our 2 turned surfaces front and back, I use some 1-2-3 block, or parallels and some shims or something up under the top of the mounting pads, so that they are held level in the vise. we want that as you will want to mill the 2 pads at the same height, and end up with the webs being the same thickness.
using indicator, check that all is square and well. use edge finder and split between the 2 outer ears, this sets the center, then mill the pad surfaces, and the width between them, don't touch the outer vertical surfaces, they where cast on the prototype!
then while set up, drill the mount holes.

[gcarsen]

next, I always make quick little fixtures to work with, makes things usually go faster, especially if multiple parts. took a block of aluminum, made a nest to hold the cylinder castings by the mounting pad surface, use a series of screws, with washers acting as the clamp, doing light work so we don't need a ton of pressure. plus mounting the cylinder like this puts no tension, or stress on the bore to cause roundness or size issues. place a suitable parallel under the casting, that sets a working height, and establishes that the face is true to the table. tighten the screws,
the outer round portion is left cast on the full-size, I wanted these surfaces to match up nicely when finished, yet still have the cast surface! use indicator to pick up the outer portion, from the pads it was off a few thousandths from the "print" well with in railroad tolerances!! using this new center, I bored out the cylinder bore to size.

[gcarsen]

OOPS!
bored the cylinder's out to size, 2 of the 3 have porosity holes in the bores!!! not good!! and not just little pin marks, but some pretty good holes.
talked with Jim, he sad that the first batches had this problem, he has since then changed to a different foundry and has had zero problems since then,,,,,
but now,,,, how to deal with this little snag,,,,,,

[FLtenwheeler]

It looks like it is time for a sleeve.

Tim

[GS14403]

Like that expanding mandrel, may have to try my hand at making one next time the need arises.

Wonder if JB weld will work on the porosity. Fixed quite a few aluminum engine blocks and cylinder heads with the JB weld. Filled the porosity, let it sit overnight, sanded smooth and away we go. Just a thought.

Donald

[FLSTEAM]

Wonder if JB weld will work on the porosity. Fixed quite a few aluminum engine blocks and cylinder heads with the JB weld. Filled the porosity, let it sit overnight, sanded smooth and away we go. Just a thought.

My thoughts exactly. Maybe even just epoxy if the cylinder is not used with steam.

John B.

[gcarsen]

JB weld would probably work for this application, I know of one old car, it broke a set of rings in one bore, and tore up the cylinder bore really bad to where it lost all compression in that hole. the guy had no funds to fix it, he opened the scratches a bit more, roughed them up, and filled it with JB, dressed it down, new rings, ran for another 70k till he parted with the car with no problems.
but since 2 of these are for Jim, and Bill's Berkshire builds, and as my customers hold me to high standards, and its how I want to be treated and do things,,,
yes, do it right and sleeve it.
no for some issues, the bore is 2.000 diameter, 1.938 long. and its very thin wall! looking everything over I felt the thickest wall section I could use was .030 a side. and use 316 stainless for the sleeve. makes for some thinking on pulling this of. with the cross section of the casting, diameter, and depth. a standard press fit would not work, bust or crack the casting, or half way in gall and get stuck and just go down hill from there! or the sleeve would collapse or kink, but a perfect application choice for a heat shrinked sleeve,,
material, buying stainless tubing has always been problem in my experience. the label might say one flavor, but from one end to the other its all over the place. one section might machine nice, the next? but in my material pile I had some 316 stainless shafting, 2.25 diameter , cut 2 pieces to 2.75 long! perfect for the job.
so set the 2 cylinders back into the fixture, bore out to 2.060 diameter on the button!! with perfect finish.
next

[gcarsen]

Ok, put the stainless shaft in the lathe, drill about a 1 inch hole clean through. face the end, bore the end till it cleans up over 1, about 1 inch deep. rough turn the od down to 2.100 .040 over for finish. reverse in chuck, hold on to about .5 of the length. the chuck I was working with worked out fine with the jaws reversed. held tight to the oh, the faced end tight to the jaw face's. nor face the end, rough turn the od to match the 2.100, then bore that end to 1.780 diameter, roughly 2.15 deep. let it cool spinning in the chuck. some method to my madness here,,, later. once the part is cooled down. finish face the end, now bore the id to 1.800 by 2.100 deep. take a few spring passes as we want a pretty accurate bore, finish , and trueness! now finish turn the od to 2.063 for a length of 2.1. get a good finish, and cylindrical. the little Feeler lathe hit the numbers right on the button, and no tapers! file a small smooth chamfer on the end. that's the lead in, but only about 15/20 thousands. hit the od with the scotch brite pad. pull it out of the chuck. clean it all up good, remove all oils, burs. finish cleaning with acetone. blow dry of and put in the freezer! using acetone makes sure there is no moisture on the surfaces that will turn to frost or ice in the freezer.
that funny counter bore end that I did??? that was to leave a fair amount of material under the chuck jaws to remove any chances of the sleeve collapsing or going egg shape in the chuck, plus it makes it so you can hang on to it pretty good in the chuck while turning. the .130 wall section leaves enough strength and rigidity to easily and accurately machine the id, and od and get good results. had no chatter or other issues. uses carbide insert of the od, brazed carbide on steel boring bar.
clarify an important issue, casting bore 2.0600, turned the od of the sleeve to 2.063, giving an interference dimension of .0030

[gcarsen]

more pics for above post

[gcarsen]

ok, for the hot part of this job,
found a clean steal disk, and 2 pieces of .030 shim stock, got out the rose bud, striker,,,,, and the deadblow rubber hammer incase something needed some persuasion!

got everything set up, the casting on the plate with the sides supported with the shim stock, space .030 up in the air above the plate. shims recessed to clear the sleave. get the sleeve, place close by at hand. light the torch, slowly, and evenly heat the casting up, when its good and warm, kill the torch, grab the sleeve, and drop it in! rotate it making sure its all the way through and sitting on the plate. after a few seconds it tight!!!
let it air cool, don't through it in the cold water till its cooled way down!!

[gcarsen]

Don,
while the parts are cooling,,
here is a pic of the expanding mandrels I have. made by K.O.Lee. set comes in 3 sets of mandrels as I recall. very handy and covers a huge range of sizes. got this set 20 years ago used, still works good!