"Catherine", a USA "Sweet Pea" engine build

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Benjamin Maggi
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Re: "Catherine", a USA "Sweet Pea" engine build

Post by Benjamin Maggi » Sat Dec 12, 2015 3:49 pm

The next step was the steam chest covers. These started off as more blanks of Durabar cast iron that I had purchased when I visited them in York. The blanks were put in the mill and slowly machined until one surface was smooth. The final thickness is 5/16”. Then, taking a visual cue from the cylinder covers, I scribed lines on the tops of the covers and decorative grooves were milled using a ball mill. First, the outlines of the grooves were machined and then the middles of the grooves were carved out. The process was slow to prevent damage to the ball mill, and the cutter did eventually break but it did so during the “middle” phase so it didn’t impact us significantly. It was impossible to get the bottoms of the grooves perfectly smooth but they are pretty good as is and I imagine paint will fill in the small voids.

The steam chests and their covers had their ten holes already drilled #21 holes opened up to 3/16” as clearance for the bolts. Finally, everything was assembled together. I used WD40 to clean out the holes in the cylinders, which worked great because it was slippery and because it contained compressed air. There were a ton of chips trapped in the holes, and it seems an ultrasonic cleaner might be a good investment in the future. I also ran a 10-24 tap in and out of the holes multiple times, cleaning off the chips over and over.

Then, once everything looked good together we actually took it all apart again.
Attachments
Steam chest covers in place.jpg
"One cannot learn to swim without getting his feet wet." - Benjamin Maggi
- Building: 7.25" gauge "Sweet Pea" named "Catherine"

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Benjamin Maggi
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Re: "Catherine", a USA "Sweet Pea" engine build

Post by Benjamin Maggi » Sat Dec 12, 2015 3:50 pm

We machined the steam passageways in the steam chests next. The inside of the steam chest was center-punched and then it was clamped in the milling machine at an angle, held with pieces of wood to keep it at the odd angle. Then, using a 7/16” bit (later opened up to 29/64”), the angled passageway was drilled out. The steam chest was then laid horizontal in the mill and the connecting top passageway was drilled.

The plans called for a simple union to be bolted to the top of the steam chest to match it up with piping coming from the smokebox. Instead, we tapped the top of the steam chests 1/4-18NPT and I purchased some brass compression fittings which will screw right in. Looking back, I wish I had just drilled a horizontal hole through the back of the steam chest into the chest area itself and then tapped the hole on the outside for a 90-degree compression fitting. Instead, the fitting I have comes out the top. It will still work, but the other way would have been simpler.
Attachments
Milling passages in steam chest.jpg
"One cannot learn to swim without getting his feet wet." - Benjamin Maggi
- Building: 7.25" gauge "Sweet Pea" named "Catherine"

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Benjamin Maggi
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Re: "Catherine", a USA "Sweet Pea" engine build

Post by Benjamin Maggi » Sat Dec 12, 2015 3:51 pm

Then, it was time to remount everything onto the frame and make sure it was okay. In the process, we changed the way that the slide bars are supported on their rear-most ends. Per the plans, the tops of the slide bars were to be drilled and a small block bolted to the end sticking up. This block would then be drilled horizontally and screwed to the motion plate which extended out from the frame. Since we had the ability to do so, instead we just drilled the end of the slide bar horizontally and bolted it to the end of the motion plate.
Attachments
Cylinders bolted to frame.jpg
Cylinders bolted to frame 2.jpg
"One cannot learn to swim without getting his feet wet." - Benjamin Maggi
- Building: 7.25" gauge "Sweet Pea" named "Catherine"

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Benjamin Maggi
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Re: "Catherine", a USA "Sweet Pea" engine build

Post by Benjamin Maggi » Sat Dec 12, 2015 4:03 pm

The two slide bars (which up to this point were oversize in length) were bolted together by their existing bolt holes and then we used the belt sander to make them the same length. Then, we mounted each one in a square collet in the lathe and first center drilled, then drilled with a #7 bit, and then tapped them 1/4-20. The holes were drilled in about 3/4" long.

The motion plates were laser cut for me by a local company and were my first attempt and using such a company. I am really impressed with how they came out.

The pictures show the valve stem, which is much longer than required. It will be shortened later on.

Finally, everything is attached to the frame and it all lines up well.
Attachments
Slide bar mounting.jpg
Last edited by Benjamin Maggi on Thu Dec 17, 2015 5:00 pm, edited 1 time in total.
"One cannot learn to swim without getting his feet wet." - Benjamin Maggi
- Building: 7.25" gauge "Sweet Pea" named "Catherine"

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ironhorseriley
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Re: "Catherine", a USA "Sweet Pea" engine build

Post by ironhorseriley » Sun Dec 13, 2015 2:39 pm

The results are very impressive!
Jim, Former railroader, fascinated by wood working & “all things engineered”.

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Benjamin Maggi
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Re: "Catherine", a USA "Sweet Pea" engine build

Post by Benjamin Maggi » Fri Feb 19, 2016 6:34 pm

The next parts that I worked on were the crossheads. I was looking forward to these as they seemed to be a fun milling exercise, and it would involve a bit of simple layout work. The crossheads on the engine consist of two parts- (1) a “base” that has a slot milled in it to slide along the slide bars, a corner milled away to accept the drive rod, and a hole on the opposite end to which the piston rod is threaded into, and (2) a cover which keeps the crosshead from falling off the rod.

Side track alert! While I am a big fan of the Great Western Railway’s steam engines, I think that their “Castle” and “King” class locomotives have really large and somewhat ugly looking crossheads. (The picture below was found at this link: http://www.docbrown.info/docspics/Archi ... o04003.htm) Then again, several different people have told me that the Sweet William engine looks really ugly so who knows? Regardless, I think the design on my contractor’s engine looks nice and utilitarian.
Attachments
GWR valve gear.jpg
"One cannot learn to swim without getting his feet wet." - Benjamin Maggi
- Building: 7.25" gauge "Sweet Pea" named "Catherine"

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Benjamin Maggi
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Re: "Catherine", a USA "Sweet Pea" engine build

Post by Benjamin Maggi » Fri Feb 19, 2016 6:36 pm

Some 5/32” thick steel was already on hand so that was squared up on the belt sander and then cut down into the two pieces, one for each. It was at this stage that I realized that even though I was making similar parts they were mirror images of each other and I was likely to confuse them if I wasn’t careful. So, I used a marker to draw the areas that would be milled from the crosshead base below to help me keep track of them.

For the crosshead base, I went to the metal store and purchased a slice of hot rolled A36 steel that was ¾” thick and 10” wide. I had them cut me off a piece 2.25” wide, which would allow me to get 4 crossheads out of it should I mess up. I made sure to get hot rolled because I didn’t want the bases warping from all of the milling. The ¾” thick was slightly larger than the 11/16” dimension called for, but it will work fine without any clearance issues. I just need to adjust my dimensions slightly so that the excess overhangs in the back. I doubt it will cause any balance issues but if it does, I can always mill away the 1/16” from the back later.

The plans here were not crystal clear from Blackgates Engineering. They called for the bolts along the top row to be unequally spaced and I cannot figure out why. I wasn’t sure if I was reading the plans incorrectly as one dimension is missing, but they failed to respond to several of my emails. So, I went with my gut and assume it will be fine.

I drilled the covers first with a #36 bit, which is what is necessary for tapping 6-32 hardware. Then, I clamped each cover to the crosshead and drilled through the covers into the bases. Then, I removed the covers and opened up those holes with a #28 bit which will allow the 6-32 hardware to clear.

Along the way, I learned a lesson in how to repair a drill press when the pulley’s set-screw comes loose and allows the pulley to spin freely on the motor shaft. I thought perhaps my drill press was ruined but my friend quickly diagnosed the problem. Phew!
Attachments
Crossheads - laid out.jpg
"One cannot learn to swim without getting his feet wet." - Benjamin Maggi
- Building: 7.25" gauge "Sweet Pea" named "Catherine"

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Benjamin Maggi
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Re: "Catherine", a USA "Sweet Pea" engine build

Post by Benjamin Maggi » Fri Feb 19, 2016 6:37 pm

The crosshead bases were then machined to remove the slot where the slide bars will run. I started the slots by using a bandsaw to cut gaps along the edges, and then a mill removed the necessary material. Cleaning up the inside corners so that they were a proper 90-degrees took some finesse with a file but after a bit of time they were okay. We aimed for a nice sliding fit of the crossheads on the slidebars (including the bronze slippers), but until it is run on air I won’t know if it is too loose or too tight.
Attachments
Milling the slots.jpg
Finished slots.jpg
"One cannot learn to swim without getting his feet wet." - Benjamin Maggi
- Building: 7.25" gauge "Sweet Pea" named "Catherine"

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Benjamin Maggi
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Re: "Catherine", a USA "Sweet Pea" engine build

Post by Benjamin Maggi » Fri Feb 19, 2016 7:19 pm

Tapping the holes in the crosshead bases was another matter. We used the power tapper for the first one but it cracked the tap on the very first hole! Apparently, it doesn’t like the smaller tap sizes as the 10-24 and ¼-20 taps worked fine. So, all eight holes on each crosshead base were tapped by hand. It actually was pretty easy to do, though flooding the holes with lubricant helped. While tapping the second crosshead base, I broke a tap while backing the tap out (not the other way around) which was strange. The A36 steel just wasn’t as nice to machine as other types.

For each crosshead, since we had a broken tap we removed what we could and then drilled a replacement hole in the covers and bases. As it currently stands, the two crosshead assemblies are not identical anymore because each has a misplaced bolt. However, they work fine and it is unlikely anyone would ever notice if I didn’t point it out.

To fix the visual cue of incorrect holes, I used JB Weld two part epoxy to fill in the unnecessary holes. It mixed up stiff but flowed down into the lower portions and I used blue painters tape on the backside to prevent it from running all over. Once the parts are painted, it will be fine.

Finally, the bronze “Slippers” as they are known in the UK (perhaps in the USA too?) were fabricated from some 3/32” thick bronze. Once it was milled to the correct width of 0.500” thick, it was bent up on a brake to the correct length. As it is seen in the pictures, the upwards portions are too long but I will cut them down in time. I used a file to smooth any burrs on the bronze and also to make sure it fit into the crossheads fine.
Attachments
Bronze slippers.jpg
"One cannot learn to swim without getting his feet wet." - Benjamin Maggi
- Building: 7.25" gauge "Sweet Pea" named "Catherine"

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ironhorseriley
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Re: "Catherine", a USA "Sweet Pea" engine build

Post by ironhorseriley » Sat Feb 20, 2016 5:46 pm

I guess the slipper is only needed on top & not on all four sides with gravity being the biggest influence on wear?
Jim, Former railroader, fascinated by wood working & “all things engineered”.

Harold_V
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Re: "Catherine", a USA "Sweet Pea" engine build

Post by Harold_V » Sun Feb 21, 2016 2:49 am

ironhorseriley wrote:I guess the slipper is only needed on top & not on all four sides with gravity being the biggest influence on wear?
Gravity is virtually without issue. The wear comes from thrust, created by the crank angle and the power stroke. That's why the cross head exists, and why there should be a bearing both top and bottom. Side load shouldn't be much of an issue, so as long as there's lubrication and respectable clearance, although, in a perfect world, all sides would have a bearing that is compatible.

Harold
Wise people talk because they have something to say. Fools talk because they have to say something.

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Benjamin Maggi
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Re: "Catherine", a USA "Sweet Pea" engine build

Post by Benjamin Maggi » Fri Apr 08, 2016 8:38 am

Nothing positive to report. Since the last post, I have been sick for the last 6 weeks with a virus/flu/cold bug which has left me tired and not really in the proper mindset to work on the engine.

Which is sad, because I was getting ready to start working on the drive rods which should be an exciting time for a locomotive builder. Several years ago I began work on the crankpins, and I decided then to deviate from the plans. Instead of building marine-style rods which have a round profile and are essentially three pieces with two ends that bolt around the crankpin to the middle part, I wanted to make regular engine rods that are one piece which slide over the crankpins and are retained from coming off some how. I drew up plans based on the Little Engine's 0-6-0 crank pins and went away. I never finished because we started working on other parts, and they sat for two years. Now, I am thinking I will stick with the marine style rods.

However, several clearance issues with the valve gear I have built so far have presented themselves.

First, because I made my crossheads 1/16" thicker than the plans called for to allow for the metal I had, they stick out too far in the back and the crankpins won't clear them. If I mill the crossheads to the proper thickness I still may have clearance issues. Part of that is because the wheels have some side-to-side play even though we installed some thrust bearings. I may need to revise the crankpins to make them extend out less, and also spread the motion plates out further from the frame to give more clearance.

Second, because the motion plates were installed lower in the frame than called for (to avoid a stupid looking method for attaching the slide bar to them), the rods hit the motion plate which going through their rotation. I could mount the motion plates higher which should help, but I will need to mill the clearance cutaway deeper to completely fix this.

Finally, measuring the rod length has proved somewhat challenging to this newbie. I made up a cheap set of experimental rods from some aluminum stock I had but even with them mounted the wheels bind. Obviously, they are either too long or short and I will likely turn them into some sliding/adjustable rods to fully obtain the proper length.

None of these problems cannot be overcome, though I do wish there were others who had built this exact engine that I could call. I only know of one or two in existence, and even Blackgates Engineering doesn't always respond to my technical issues. How I envy Allen Mogul builders who are at every club.

Also, the three problems along with my illness have put me in a bad mood, which is never the right mindset when working on a project like this. I may take a break from it for a while, just to think things over.

turned up a couple of crankpins, which

In asking here for advice on measuring the distance for the crankpins (http://www.chaski.org/homemachinist/vie ... 8&t=103255) I received a lot of wonderful ideas.
"One cannot learn to swim without getting his feet wet." - Benjamin Maggi
- Building: 7.25" gauge "Sweet Pea" named "Catherine"

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