Double Tangye Steam Engine

[Stuart]

mount it flange up on your rotary table using a angle plate ,clock up to outside of flange and face,  then run round wit a small say 404 woodruff cutter under the flange.

not cosha but it works done it myself in similar situations with lumpy castings


Stuart

[steamer]

That would do it Stuart.....two methods!

Dave

[Jasonb]

Stick it on a mandrel, mount to a vertical rotary tabel and use a ball ended cutter to take most off then the woodruff type cutter to get at teh bit hidden by the base.

I would also say it needs to come off the outer face based on your earlier photo but you did not show iff teh beraings were in line the.

J

[Jo]

Thanks guys I think I will try the hockey stick approach first. In the meantime castings you either   them  or  them . Time to look at the bearing caps, so at first glance it looks ok:



They actually need to be shortened and squared up so off to the mill. Take to width, then length and lastly cut the shoulders.



Now that they are both the same width and length we can using a wobbler find the centre:



There is no point in risking getting things nearly right using a wobbler only takes a minute or two and you can then drill knowing you are exactly where you should be. Having got the holes we now use an end mill to cut a clearance for the nuts.



So time to start playing with the stand castings, in theory the spaced correctly from the end the caps would go here:



But that would leave the centre line of the crank 2mm low. The maximum I could acquire was 1.2mm by moving the centre line of the crank forward on these castings. But the two stands are not made to match so if you line up the bearing surface (and the front cylinder mounts) the rear of the castings are out:



A bit of fettling and I can live with that... Now it is time to look at the bearing stands. Which surprise surprise  were also not the same height (the studs had also rusted solid and sheared as I tried to take them out but such is life  : stainless studs  are the business)  . Thankfully that does not matter as I had to take them down a bit so that they matched the crank height on the two main stands.



Off to the mill and both were taken to the new centre line height:



So we are now ready to bore the four bearings. For those of you who are not aware of the size of this engine I have added a 6” rule in the back of this shot:



Time for a little… 

Jo

[Tennessee Whiskey]

I think you could set the RT vertical and come from each side of it with an end mill..

Whiskey

[Jo]

You got me thinking Eric... I would get the inside curve, a longer milling cutter would cut the flats.... 

  I have some more S&P to do before I am allowed to do any more DT

Jo

[Maryak]

I also did not get any ideas for machining the back of the cylinder mounting flange. So another view of the problem, my red paint stick is pointing at the flange that needs the back edge machining.

Jo

Usually the bolts are so arranged that the back face is spot machined to allow for the seating of each nut and washer.

Dare I say studs and no machining as an alternative. 

Best Regards
Bob

[Jo]

Bob,

The rear face on one is very uneven so still needs cleaning up. I will have to make a small reverse spot face cutter to cut the pads for the nuts but after my success with the S&P mouldings I have a bit more confidence with these things.

As for my studs  Just when you think you are allowed time off to do more useful things with your time another 28 cylinder head studs get in line for their turn.. then there is the 24 for the steam chest.. 14 for the base..  There is a lot to be said for beam engines one of them is they don't need many studs

Jo

[tel]

Is the gloss wearing off stud making? Tell me it isn't so! 

[Jo]

I try to make the best of them pace myself, you don't want to do too many at the same time, otherwise the little pleasures are lost.

Maybe its a case of I have been focusing on the wrong sort of studs and I should spend some time on another type

Maybe I have just got my technique wrong

Jo

[Stuart]

the other type may lead you astray 


stick with the one you know


Stuart

[tel]

Yeah, press studs wouldn't work and I don't think collar studs would either.

[Jo]

the other type may lead you astray 

  I remain hopefull

Jo

[Jo]

The engine stands and the bearing supports all must be identically the same height and bore at the bearing centres. To do this I used the mill, so first up set up an angle plate to act as the reference plane and zero on the top surface:



Now we can swop over to a sticky point and use that to find the crossing point of the correct centre height to give us the centre lines of where to bore. Then starting with a drill and then moving up to a slot drill that is still under size:



We then have only 1mm to go which is taken out using a boring head:



Having set the boring head using the bore gauge to check the measurement the boring tool must not now be adjusted, this means that we can use it on all four bores and know that they will all be the same size.

The one bearing support that had already been bored 12.7mm had nothing to line up on so I used this piece of 12mm bar to measure off to find the centre:



I thought that this one was a bit tight on the casting:



But the other one is even closer so I need to take another look at the design of the bearings to go in these.

So four stands sitting on the surface plate and a 5/8” bar slides nicely across all four:



The sun is still out it must be workshop time…..

Jo

[Jo]

I always try to reuse everything I can with a second hand set of castings. That includes for today this pair of pieces of split Bronze which had been soft soldered together for the crankshaft bearings:



The first problem is to try to centralise the split using a four jaw chuck and then turn the material round:



This was the point I discovered that this bronze was not too fond of being soft soldered together as one pair fell a part when I started to try to bore them:



You may have noticed that were someone started off with a piece of tube the entrance is “broken” and bronze is snachy. To overcome this I drilled using an end mill:



Then reamed. This material is only 2.4mm over length so to get both bearings I had to go against normal practise and part them. I would normally turn them on an over length piece but this material is just too short. So parting off had to be done carefully and finishing with a saw to prevent the out bearing breaking apart:



Then it can be faced to length:



Next I needed a mandrel to turn the bearing on, so one was quickly turned up, drilled and then tapped. I have not shown my tapping arrangement for use in the lathe some time, this is it:



The tap is held in a ratchet tap holder and is kept square using a spring loaded plunger in the tailstock.

One concern I had when mounting the work on the mandrel was it splitting as I tightened the bolt/clamp on the end so I resorted to making use of a g clamp whilst I tightened it up.



The outside can then be turned to size using a parting off tool to give the correct depth of groove and before we take it off the lathe check the fit on the bearing surface:



So both of the outer bearings done, after lunch I have the second pair to make.



You can see in the photo two cranks came with this engine the one at the top has the two outer spigots too short , the turner missed that there is a flange on the back of the cranks,  but the correct outer dimensions, including the central part on which the flywheel mounts. The lower one has the two outer spigots too small and the central flywheel area undersize  .

Jo