Author Topic: Stuart Beam Restoration  (Read 16212 times)

Offline smfr

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Re: Stuart Beam Restoration
« Reply #15 on: July 21, 2012, 07:54:07 PM »
After being away for a few days, I got some time in the garage yesterday, and decided to clean up the cylinder bore a little. It's pretty corroded at one end:



probably from sitting with moisture after being used with steam. To take off the pitting, I think I'd have to bore it out another few thou or so (after setting it up absolutely straight), and that sounded tricky. So I decided just to lap it to smooth out the rest of the bore. I think most of the pitting it outside the piston travel anyway.

So I made a lap from some Al rod (another estate sale find!). I cut off a length of rod on the chop saw:



and turned to just under 1", drilled and tapped for M8 1.25, then used the slitting saw on it:



(if you look carefully you can see I'm not quite on the centerline, despite measuring and using dials to get there :( )

Now I can adjust the lap by screwing in an M8 bolt. Here's the cylinder in place:



You can see the three grades of lapping paste. The lathe was run at low speed, and the cylinder is held by hand (carefully!) and moved up and down the lap, reversing it every so often.

I was trying to figure out how to make the lap so that it expands in the center, rather than at the end; I wasn't able to drill deep enough to have the end of the screw thread further in. Having the lap expand in the middle means that the cylinder is less likely to be misaligned as you move it back and forth (which would result in a bell-mouthed bore).

Anyway, I lapped off about a thou or so, which smoothed out some of the roughness. No after pics, alas.

I then mounted the piston on the piston rod, and carefully turned it down to size. Not carefully enough, apparently, as it ended up a sloppy fit  :(

So I made another piston from bronze, and brought that one down to size with emery paper. Apparently I was too aggressive there as well, because that one ended up a bit sloppy too, but close enough for now. With the piston rings fitted, it feels quite snug. I seem to recall reading that you needed some room for piston expansion if it's going to be run on steam anyway.

Offline smfr

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Re: Stuart Beam Restoration
« Reply #16 on: July 21, 2012, 07:54:38 PM »
I've been trying to find the source of some tightness at the crank end, and spent much of today chasing a couple of theories.

My first theory was that the holes in the crank were misaligned, causing binding as the crankshaft rotates. To test this, I made a new crank, starting with a chunk cut from an old toolholder, milled to size and marked out:



I located the first hole, drilled and reamed, and then used the dials to move over exactly an inch for the second hole:



I've learned that it's best to take care of the precision aspects of a part early on, while it's easy to hold; the shaping can come later.

After some rough milling, it looked like this:



and here we are in the 4-jaw after turning the larger boss.



It was tricky to get between the bosses; if I had a rotary table, I think I'd use it for this. I just wanted to get far enough to do a test fit, so turned down some spare 7/16" drill rod to act as a crankshaft and did a press-fit. Here are test and original cranks next to each other:



You can see my attempts at turning out the space between the bosses. It's hard to get tools in there, without dinging the bosses (which I managed to do).

Anyway, after putting everything back together, this new crank didn't seem to make things any better, so I guess the problem isn't in the crank!

Offline smfr

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Re: Stuart Beam Restoration
« Reply #17 on: July 21, 2012, 07:54:52 PM »
So, next theory. The holes in the beam are misaligned. Certainly the spindle hole at the crank end seems a bit off:



so I spent a bit of time on the surface plate, trying to figure out if there really was a problem:



and decided that there was. I suspect what happened is that the beam is slightly twisted, and doesn't lie flat. The beam was clamped down for drilling, but when released, it sprung back, resulting in non-parallel holes.

So I pushed out the bronze bushings that I'd made earlier, and turned new, solid bushings, which I plan to drill in situ. Since I was doing one, I decided to do the other two spindle bushings too, and re-locate the holes as well as straightening them. With the bushes fixed in place with Loctite, I then tried to figure out how to mark things up:



The important thing is that the spindle holes are aligned with the center of the main spindle, so here the beam rests on V-blocks while I try to find a centerline through the center of the main spindle, to mark on the bushings. I'll use this to align the part on the mill.

Likewise, I want to ensure that the spindle holes are drilled parallel to the main spindle, so I think I'll use a setup something like this:



where the main spindle is held in a V-block on its side. That's not my final setup; way too much overhang on the ends ;D

It's interesting how far off the centerline is from the original holes:



so the original builder didn't seem to be very accurate with the beam. I just hope none of my holes hit the edge of the bushing!

So tomorrow I'll have a go and fixing this down (without twisting!) and drilling. Hey, at least I can push out the bushings and make new ones if I mess up!

Offline smfr

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Re: Stuart Beam Restoration
« Reply #18 on: July 21, 2012, 07:55:09 PM »
Got a little bit more done today. I turned a mandrel to hold the beam during machining, since I wanted a longer length to hold in the V-block, and the original spindle is a sloppy fit (which is OK while running, because it's held in with a lock screw).



With that secure in a V-block, which was held in turn in a 2" vise, I aligned the beam so that the centerline was parallel to the plate (and thus the base of the vise):



and marked out a line on the bronze bushings. I had to take care to not knock this out of alignment for the rest of the operation. Now onto the milling table on my Emco Maximat. I had to go front-to-back because the table is deeper than wide, which required moving the part for each end. Here I'm indicating on the base of the vise to ensure that's it's parallel with the direction of travel:



and found that just aligning the vise to the edge of the table was good. Then I centered on the mandrel:



I'm using a ball-end wiggler; with the mill running, I move the quill wiggler lightly into the center drill hole, and can see when the wiggler gets pushed aside when misaligned. I took care to pack under the beam with shims to avoid torsion when clamping.

Now I can use the dials (double-checked with calipers) to move over the required 3.5" to drill and ream:



Then I flipped the whole fixture around and repeated the operation for the other two holes. A quick fitting suggests that this solved most of the binding at the crank end, but I had to dash off to a social obligation, so the real test will have to wait! ;D

Offline smfr

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Re: Stuart Beam Restoration
« Reply #19 on: July 21, 2012, 07:55:30 PM »
Time to fix the cylinder to the new cylinder base that I machined earlier! This meant spotting the holes through somehow (since I had to match the existing holes in the cylinder).

I initially started with annoying little bits of paper:



but then had a better idea. I fixed the cylinder up in the vise with a kind of jig that would let me place the base on top repeatably. Then I could just line up on a hole using a drill that was smaller than threaded hole



by carefully lowering the drill and looking/listening for interference. Then I just put the cylinder base in place, bottom side up, and, without moving the table, spot-drilled with a center drill:



Then I could transfer just the base to the vise, and drill and countersink each hole. Presto, nice fit:



Next will be spotting the holes through from the main casting to the cylinder base, which might be a bit trickier.

Offline smfr

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Re: Stuart Beam Restoration
« Reply #20 on: July 21, 2012, 07:55:48 PM »
OK, now that I have a turning table (http://www.homemodelenginemachinist.com/index.php?topic=16765), I can show you how I went about making the linkage links. We start with some bar stock:



Actually the top two pieces there are the old entablature arms, which I thought it would be neat to re-use. However, after cutting them to size, I realized that they have screw holes :o

I'm making two links here. The bar stock is cut to length accurately for repeatability, and center drilled at the ends, for turning between centers. The length was calculated so that the center drill holes don't hit the metal we want to keep. That's one of the old links on the right.



Now the two holes are center drilled, drilled in steps, and reamed 3/16":



As usual, since the distance between these holes has to be accurate, I do them early in the steps.

I've also learned not to worry about under/over reamers; I just use the exact size. This seems to give a nice snug fit with the drill rod that I'm using for the spindles, but maybe that's because the reamer is pretty new, and is cutting oversize?

Now to turn the fishbellies. We set up between centers, driving via the faceplate. I'm using a bit of thick copper wire as a dog, through one of the holes. Works great!



Now I did a bit of math to work out the correct angle to set the compound rest at; it's around 1.2 degrees (from what I recall), but we'll end up adjusting this a bit. I also made myself a little cardboard template to show me where the middle is, and where I should stop turning:



Once I had a cut that covered half of the turned section, I measured the larger and smaller diameter to see if the difference between them matches what the plans calls for; getting it right required adjusting the angle of the compound rest several times, by small amounts. I'm moving the tool right to left via the compound rest to get the taper, then adjusting the cross-slide to control the final diameter.

Once one half is done, I flipped the part around and do the other half (this is where it's useful to have the bar stock length be accurate). Then came some filing to smooth out the middle, and several grades of emery paper to remove the tool marks (easier to do this now while turning between centers than later!).

Here's one link turned, though it could still use some smoothing:



Now I made use of the rounding table to round the ends:



and we end up with:



The ends still need reducing in thickness, and there's quite a bit of filing to do. I'll clean up all 8 links at the same time (at least until I get bored of filing ;D). 8 links, 16 ends, 32 faces ... that's quite a bit of work :-\

Offline smfr

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Re: Stuart Beam Restoration
« Reply #21 on: July 21, 2012, 07:56:04 PM »
Lots of rather tedious stuff today. Got all 8 links rounded down on the rounding table (some a bit undersize until I realized that I could use a carriage stop to make sure I didn't go too far!), and the 2 new links milled to the right thickness.



(Yeah, I can't count. That's 9. I'm making one extra ;D)

I made myself a fixture to help with filing, and some filing buttons:



The bit of drink can is to prevent the round file from digging into the end of the turned portion, and tape protected the rest. I'm using needle files to do rough cleanup, then various grits of emery paper (220 to 2000) to finish, with a final polish with the Dremel.

2 down, 7 to go, ugh!


Offline lazylathe

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Re: Stuart Beam Restoration
« Reply #22 on: July 21, 2012, 07:56:17 PM »
I really love following along with rebuilds!
Taking an old engine and breathing new life into it.
An amazing talent!

Great work Simon!

Andrew
A new place to hide my swarf!

Offline smfr

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Re: Stuart Beam Restoration
« Reply #23 on: July 21, 2012, 07:57:12 PM »
Thanks Andrew! A few more posts to copy...

I spent a couple of evening filing the links, and got bored so decided to start on the new valve chest. I bought a new casting from Stuart because the existing one has a hole drilled in the side :-\

The casting was cleaned up with a file, and faced in the 4-jaw chuck on both sides. I started on the valve cover as well, which still needs taking down a little:



I think the corners of the valve cover look different because I don't have enough support behind them in the chuck, and they are flexing under the tool. There also look to be some hard spots in that casting, or maybe the unevenness of the turning is because of something I'm doing?

The valve chest after some lapping on the plate glass:



That's the easy part! I have to transfer the holes from the cylinder itself on this one, and drill for the valve rod etc.

Offline smfr

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Re: Stuart Beam Restoration
« Reply #24 on: July 21, 2012, 07:57:34 PM »
I've been thinking that I need to clean up the valve surface on the cylinder, since it's pretty messy:



It has some bad pitting. I also noticed that the valve surface wasn't perpendicular to the cylinder base:



so decided to take a pass over it in the lathe. That sounds like a good job for the faceplate! I don't have an angle plate, but figured that a couple of 1-2-3 blocks would hold it quite nicely:



I used a square with the blocks on the edge of the surface plate to true up the valve surface:



and took off maybe 0.01" on the lathe. After some cleanup, it looks like this. I took the Dremel with a wire wheel to the rusty bits, and that cleaned out a ton of rust, leaving a bit of a crater :o



I was a bit worried about taking more off. I hope that massive rusty hole isn't going to be an issue, since the valve just about clears it:



That's the valve face of the cylinder taken care of!

Offline smfr

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Re: Stuart Beam Restoration
« Reply #25 on: July 21, 2012, 07:57:50 PM »
Now back to the valve chest. After lapping the faces, I trued it up in the vise, and drilled for the valve rod:



Ideally it would have been rotated 90deg in the vise for better clamping, but I need to see when the drill hit the bottom. The top hole gets drilled and reamed for 1/8", and the valve rod requires a 3/32" locating hole in the bottom. I used the larger drill to make a small face in the bottom surface so that the thinner drill didn't wander. Luckily I had a 3/32" jobber drill lying around, since my stubbies wouldn't reach that far!

Here's the bottom of the valve chest after making the counterbore for stuffing and the gland, with two 7BA holes drilled and tapped for the gland cover. New on the left, old on the right.



I have to clean up those messy file marks. I'm not sure whether to smooth off the entire valve chest surface, or leave it looking like a casting.

Now I have to transfer the holes from the cylinder. I did this like before; set up the cylinder in the vise, here truing it up with the trusty 1-2-3 blocks:



then adding various bits of packing so that I can repeatably position the valve chest:



I then locate a hole in the cylinder valve face using a drill slightly smaller than the hole size (without the valve chest in place), switch to a small center drill, put the valve chest in place then spot-drill the valve chest. After spotting all 6 holes, I remove the cylinder from the vise, put the valve chest in, and drill those holes through.

Here we are, with studs in place, showing that the hole transfer was a success! I even used a slightly smaller clearance drill than the original builder ;D



Now I can transfer the holes to the valve cover in the conventional way.

Offline smfr

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Re: Stuart Beam Restoration
« Reply #26 on: July 21, 2012, 07:58:05 PM »
Got most of the valve rod done today. I used 303 stainless, so hopefully it won't rot like the old one ;D



Not sure what the original builder was thinking; his rod is about 1/8" too short!

I made the little valve thingy out of SS too; just need to make it slightly looser in the valve so that the valve floats nicely.

Offline smfr

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Re: Stuart Beam Restoration
« Reply #27 on: July 21, 2012, 07:58:26 PM »
I've made a start on new parts for the valve linkage. They are pretty simple, but there are two more fish-bellied links, longer and skinnier than the parallel motion ones (old at the top, new and in-progress at the bottom):



Those go to 3/32" at the ends. The top one is a little non-concentric, but since these parts don't rotate I don't think anyone will notice ;D Obviously I have to finish the ends.

Offline smfr

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Re: Stuart Beam Restoration
« Reply #28 on: July 21, 2012, 07:58:51 PM »
More progress has been made!

Of course I managed to mess up one of the valve links on the rounding table:



Note to self: add end stops to rounding table! Second note to self: when using larger end mill, don't rotate table as far! I'm too keen to get things running, so I'll come back to making another one.

It was bugging me that the sides of the valve chest, the cylinder casting and the valve cover didn't line up, so set up things in the vise to give them a once-over with an end mill. Here's my setup to get things parallel to the cylinder bore:



I trimmed the top and bottom of the valve face on the cylinder casting with a small spherical burr (that came with a dremel; I don't have a ball-end mill of the right size):



I then also put the valve chest in the 4-jaw, and cleaned up the valve guide for some bling:



Finally I polished the valve itself, and the valve face with three grades of diamond lapping paste, and found a great way to leave frosted sections on my glass plate ;D



Here's what she looks like back together now:


Excuse the blueing on the cylinder cover and elsewhere. I still have to attack that hard spot once the carbide drills arrive (hence the only 5 bolts).

The cylinder head bolts also need work. I'm thinking about going for a slightly more authentic look with studs on these and the main bearing bolts, but that could be a lot of fiddly work.

Offline smfr

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Re: Stuart Beam Restoration
« Reply #29 on: July 21, 2012, 07:59:17 PM »
It runs!

« Last Edit: January 18, 2016, 02:55:58 AM by smfr »