Author Topic: Stuart Beam Restoration  (Read 16862 times)

Offline smfr

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Stuart Beam Restoration
« on: July 21, 2012, 07:49:20 PM »
[Copied from *cough* another site. Apologies if you've seen this before.]

Hi folks

I've been working on restoring a Stuart Beam, and thought that I should put up some photos. I bought this engine along with a 501 boiler on eBay in 2010, before I even had a lathe, and fixing it up was a good excuse to get one ;D

The engine had its share of problems, a really ugly paint job, and some odd modifications. It had obviously seen quite a bit of use, with some notable wear on the conrod big end, a fairly loud knocking when running, and a lot of looseness in the parallel linkage.

My goal is to get it back to a nice quality, smooth-running engine. This is my first real steam project with the lathe.

Here's the engine in its original state:

Stuart Beam by smfr123, on Flickr

Offline smfr

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Re: Stuart Beam Restoration
« Reply #1 on: July 21, 2012, 07:49:40 PM »
Some more pre-restoration pics:

No fish-bellying on the linkage:


The previous owner loved brass! So much so that they put thin brass strips over the entablature arms:


They did something awful to the steam chest: drilled a hole in the side for the displacement lubricator, which forced them to set the valve mechanism at a weird angle:


Oil cups soldered onto the main bearings:


Another bit of brass covering the flywheel, and aluminum disc press-fitted onto the pulley:

Offline smfr

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Re: Stuart Beam Restoration
« Reply #2 on: July 21, 2012, 07:49:56 PM »
Step 1: paint stripping.

I don't have any pics of the stripping process. Basically I smeared the painted parts in Citristrip http://www.citristrip.com/, put them in a ziplock bag overnight, then cleaned everything off the next day.

After stripping, I put it back together. Looks better already!



Only then did I noticed how loose it was, so it got pushed to the back of the workbench, pending lathe availability.

Offline smfr

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Re: Stuart Beam Restoration
« Reply #3 on: July 21, 2012, 07:50:12 PM »
Steps 2-N

Lots of work represented in this picture:



I decided to machine new parts for the parallel linkage, since the existing ones were rather sloppy, and not very pretty.

There are eight parallel links, machined from CRS bar. I first drilled and reamed the holes, then turned between centers, using the crosslide to get the fish belly taper. Then the ends were rounded off using a rounding fixture. They still need final filing and trimming to thickness, and I think I'll remake a couple of them; you can see a few boo-boos if you look carefully.

On the right are the various linkage spindles, make from 3/16 drill rod, and the linkage spacers. In the lower right is the new crankpin. This needs a slot cut in the head to allow it to be tightened up.

On the left is the original connecting rod, but I added bronze bushings to both ends to tighten things up. The hole in the big end was actually oval from wear. I've also made bushings for the beam, but have not yet drilled and reamed out the holes in the beam to fit them yet in the photo.

Offline smfr

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Re: Stuart Beam Restoration
« Reply #4 on: July 21, 2012, 07:50:28 PM »
Now for some work on the column. I noticed that the arms weren't parallel with the base, so had to correct that in two ways. First, I enlarged the bolt holes in the bottom of the column to allow for some adjustment. Second, I re-machined the top of the column. I also skimmed the top and bottom of the column between centers (via the original punch marks!) to correct the fact that it was too tall.

Here I'm tidying up the base of the column (it wasn't machined square by the original builder).



Now it's time to clean up where the arms attach. Note the 1-2-3 block used as an angle plate.



This leaves the arms about 10 thou closer together than they should be, but I can take that up in the linkage spacers.

Offline smfr

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Re: Stuart Beam Restoration
« Reply #5 on: July 21, 2012, 07:50:43 PM »
Now for some new radius link bearings. The hole was off on the originals. I cut up some bronze bar stock using a slitting saw, and discovered that bronze sure does like to squirm around in the vise when being cut! See the messy cuts on the upper right piece. Some paper between the bronze and the jaws fixed that though.



The originals are the two on the left; my new ones on the right. They started out oddly shaped because I got two out of one slice by placing them diagonally. The lower right one shows another boo-boo; I was a bit eager with the rough milling. Oh well, time to use the extra piece of bronze!

Getting closer now, just need some filing:



I turned some filing buttons, and used them to shape the radius:



My first use of filing buttons!

Offline smfr

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Re: Stuart Beam Restoration
« Reply #6 on: July 21, 2012, 07:50:59 PM »
The next adventure was to make a new crankshaft. I had some 7/16 drill rod, reduced one end to fit the crank (actually this took two tries :) ), and then wondered how to fit the pin (which was used on the old crank). I knew there was no way I could drill the pin hold with the crank in place; the drill would just wander toward the crank. So I turned a sacrificial collar, lower left.



With the collar in place, fitting tightly, I started to drill:



Darn, broken bit >:( The collar rotated while being drilled, catching the drill. Let's try again:



Much better! Another option would have been to Loctite the collar on, I guess.

Now with the crank in place, I drilled a slightly larger hole to clean up the mess from the broken drill:



Turned a pin to fit the hole, and knocked it in:



After some cleanup, not too bad!


Offline smfr

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Re: Stuart Beam Restoration
« Reply #7 on: July 21, 2012, 07:51:20 PM »
I got the radial link bearings done today (other than the final polishing). Here I'm taking them down to the final 3/8" thickness:



For drilling the attachment holes, I taped them to the arms:



The tape both kept them in the right place, and took up any difference between the bearing and arm thicknesses so that they'd both be secure in the vise.

Some careful hole drilling:



and after a bit of clearance drilling, and tapping the arms, we're done. I did make one minor error, which was to choose too large a drill for the clearance holes in one bearing. I was reading the drill size table upside-down :D



I'm not sure if those are the right screws, but it's what was in place before.

Offline smfr

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Re: Stuart Beam Restoration
« Reply #8 on: July 21, 2012, 07:51:44 PM »
Now it's time for the piston rod. I debated whether to make a new one, but the old crosshead had an ugly hole in the top:



and there was no way I was going to be able to unscrew that crosshead from the piston rod without damaging it. The old rod is also slightly undersize, and is not stainless steel. Here's what the whole rod, piston and cylinder cover look like:



So, I started with some 3/16" drill rod, and made a collet out of aluminum so that I could hold it in the chuck without marking the rod.. I turned the piston end, and threaded. Here's my handy home-made tailstock die holder:



The top end gets a 2BA thread, to fit into the crosshead:



I decided to attach the crosshead to the piston rod before drilling the other hole and bringing it to size so that I could ensure that things were square to the piston rod. The chunk of CRS for the crosshead was drilled and tapped, with a bit of messing around with the depths, since it felt loose even when screwed in. However, once I screwed it on tight it was fine, and Loctite helped ;D

I made a little fixture to keep the piston rod horizontal in the vice while I machined the sides of the crosshead:



then drilled and reamed for the linkage hole:



You can see that I'm too lazy to remove the layout dye from my vise clamps :)

Here's my ghetto DRI when I need to move the carriage accurately:



It's a micrometer that I knocked on to the floor, and bent the tips. It's still good for this purpose though 8)

OK, now we're here:



Time to chuck it up again (in the collet, centered in the 4-jaw) to turn the shoulder, and bring to length:



And this is when disaster struck. I had done the shoulder with a nice bevel, and then thought that it would be smart to use the parting tool to cut off the top. Big mistake! As the tool broke through, it bent the top of the piston rod; not a huge amount, but enough to write off the part
 :'(



Oh well, now I have an excuse to re-make it using precision-ground SS rod, which is what I should have used for the piston rod in the first place :)

Offline smfr

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Re: Stuart Beam Restoration
« Reply #9 on: July 21, 2012, 07:52:00 PM »
I had a couple of hours this evening, and after yesterday's piston rod disaster, decided to do a dry run fitting the new parts together. Here's the parallel linkage, with newly machined parts:





It's a real jigsaw puzzle to put together. But once assembled, I was very pleased to find very little play in the mechanism: it's a bit stiff, but I think that's good. It should run in nicely. There's a bit of play in the piston rod, but I'm pretty sure that's play from the piston rings moving in their groove (I plan to make a new piston).

There are more serious problems at the crank end. As the crank rotates around it's forcing the crankshaft to wiggle, and I can't insert the spindle through the little end of the connection rod and the beam because of misalignment. I'm guessing that something is out of whack with the crank or the connecting rod. I can make a new conrod, and maybe drill out the crank pin hole in the crank, fit a bushing, and drill it straight.

Offline smfr

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Re: Stuart Beam Restoration
« Reply #10 on: July 21, 2012, 07:52:34 PM »
I managed a bit more work on the crank/conrod to try and relieve some of the stiffness there. After messing around with squares and such:



I decided that the big end was not drilled square originally, so I made a new bronze bushing (with a dimple for centering) and pushed it in:



so that I could then drill and ream it in-place.

That required making a fixture that would hold the conrod in the correct alignment: what's important is that the holes in each end are aligned. A couple of bits of Al were pressed into service. I milled a slot in one:



then superglued them together, and drilled and reamed a 3/16 hole for a pin that would go through the little end of the conrod, thus ensuring that the rod is aligned.



I placed some packing under the big end to make sure the rod was horizontal. Then I drilled and reamed the bushing on the mill (I don't have any pictures of that, because I'm embarrassed about my crappy clamping job ;D). I also found that bronze loves to grab drill bits if you do step drilling, but with some careful drilling, and a 1/4" "over" reamer, managed to get a nice hole.

After all this, things are much better aligned when I hook up the conrod, so progress has been made!

Offline smfr

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Re: Stuart Beam Restoration
« Reply #11 on: July 21, 2012, 07:52:55 PM »
I made quite a bit of progress today. I started with a new cylinder base. I chose to make a new one because I want to adjust the position of the cylinder relative to the column, and because the holes for the countersunk screws that go into the cylinder are not aligned correctly, causing those screws to stand proud, which in turn means that the cylinder base doesn't sit well on the main casting. I also wanted something that looked a bit prettier :)



Guess which is which! I used some 1/4" steel plate (not sure what kind; I got it at the Aluminum Rem Center in Santa Clara, CA), milled to a fairly accurate 2" x 2". I then started to fix this in the 4-jaw, thus marring the nice clean sides :( before realizing that I needed to turn in from the edge.

I moved it back to the mill, centered it up, and used a 5/16" end mill to cut the central depression (that allows room for the nut on the end of the piston rod at bottom dead center). That provides a footing for a stub mandrel; I turned the end of of a bit of scrap drill rod to 5/16", center-drilled into the other end, and used it in the tailstock to push the plate against the chuck (using a handy chuck spider that I made a while back):



Since the mandrel is a snug fit, I used it to indicate for accurate centering.

Because it's just pushed against the chuck, you have to take light cuts (ask me how I know). Maybe some paper behind it would have helped. It's also a pain to turn down to size to fit the cylinder, since you have to remove it for test fitting, and then re-center it every time, so I went by the calipers most of the time.

I left the problem of locating all the holes to another day...

Offline smfr

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Re: Stuart Beam Restoration
« Reply #12 on: July 21, 2012, 07:53:09 PM »
]I also smartened up the cylinder head today; the sides and top were not machined at all before. Here's the result:



It's an improvement in that it gives the bolts a flat surface to bear down on, but feels perhaps slightly too blingy for this model. We'll see once everything is together.

Offline smfr

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Re: Stuart Beam Restoration
« Reply #13 on: July 21, 2012, 07:53:24 PM »
OK, it was time for a second try making the piston (see earlier messages for the fate of the first one ;D).

I bought a 6ft length of precision-ground 3/16" stainless steel from McMaster-Carr for this, but the entire rod came with a gentle curve >:( so I went back using drill rod. Machining this part was uneventful, though I was careful to not make the 1/4" threaded portion on the top end too long.

I attempted to re-use the top piece I made before:



but when screwed onto the new rod, it was obviously misaligned. This vindicates my technique of machining this piece after attaching it to the rod. So I started with a new chunk of CRS (on the right in the picture).

It was faced, center-drilled, then drilled and tapped 2BA. I was careful to not drill and tap too deep, because the piston rod has to tighten up to the right length. I then screwed in the rod with Loctite:



I'm wondering now if I messed up here. I recall reading that this needs to remain adjustable to tweak the piston travel :'(

Anyhoo, here I am turning down the neck of the piston rod:



where I went a wee bit over, but this isn't a critical dimension. And here we are after two sides of the head have been milled down:



After milling the head to size, it's time to locate, drill and ream the 3/16" hole. I used my trusty vernier height gauge, with the piston standing upright on a spacer on the surface plate, and measure from the top of the piston to where the hole should be. I'm gradually learning what the height gauge is good for (and how to read the vernier scale!). Now into the vise again (with a fixture to keep the rod horizontal), for drilling and reaming:



This time I took the head down to size by holding it in the 4-jaw (with some Coke can packing to avoid marring). No parting off this time!

Now we can have some fun making the piston! I started with a length of bronze (that's the old piston in front):



and here we are after some machining:



The central depression was made with a 5/16" end mill in a chuck the tailstock, and I've drilled and reamed the center 1/8". Unlike the old piston, the groove for the piston rings is a snug 1/8". I'm leaving it oversize for now, to do the final tweaking when it's fixed to the rod.

That leaves me with the new piston parts:



(old above, new below).

Here the rod is protected with tape while I cleaned up the head with a file.. I'm also test-fitting a 3/16" spindle with a spacer. I was pondering rounding off the top to match the radius, but left it square for now.



So, almost done with the piston (new above, old below):



I just hope that the length is right 8)

Offline smfr

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Re: Stuart Beam Restoration
« Reply #14 on: July 21, 2012, 07:53:39 PM »
One final picture for today. This shows the old valve chest and parts at the top:



There are a couple of interesting (i.e. bad!) things to note. First, the valve rod is really worn and corroded, so I'll be replacing that. Second, some fool drilled a hole in the side of the valve chest to fit a displacement lubricator, which is crazy because it interferes with the valve linkage. I temporarily plugged it with a brass bolt, but wanted a better long term fix. So I ordered a new valve chest and cover from Stuart Models (lower in the picture), and will be machining those later.