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

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NP317
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Re: "Catherine", a USA "Sweet Pea" engine build

Post by NP317 » Fri Apr 08, 2016 9:51 am

Sorry to hear you were ill. That takes the wind out of anyone's sails. 'Hope you are feeling better by now.
I'm recovering from a total right knee replacement just 16 days ago, and "suffering" from ZERO time in my shop. I feel for you.

To help you get mentally "off center" and back on track, try solving the wheel bind issue first. That's a nice job of limited size, with a definite solution that will "feel good." The other issues will flow from that.
This is the approach I've used when in similar situations building my projects.
Pick the right size piece and ignore the others for now.

'Hope you don't mind my suggestion.
'Looking forward to hearing about your success.
~Russ

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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 9:59 am

Thanks Russ!
"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 » Tue Apr 12, 2016 12:14 pm

Hang in there Ben. The bugs that have been going around even into the early spring this year have proven to be tough to beat. My wife & I both had to finally give in and go to the doctor to finally get the brakes put on being under the weather.

Jim
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 » Tue Apr 26, 2016 1:51 pm

Benjamin Maggi wrote: 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.
I have been working on building a set of adjustable length rods, which has actually been enjoyable. I will post progress on that at a later time.

However, right as we were packing up last night in my friend's shop we started discussing the lack of clearance between the crank pins and the crosshead. Last week, I actually milled the crosshead thinner to equal the dimensions on the plans (I bought slightly thicker stock then called for, not realizing that it would make a difference) but it still wasn't enough clearance.

As we were talking, he said something along the lines of "maybe we made the frames narrower than called for." I quickly responded "Of course we did, to leave extra room for the thrust washers and to prevent the backs of the wheels from rubbing against the frame. In fact, I designed these 3/16" thick shims to do that." I pointed them out to him and then stopped dead.

That, most likely, was why the crossheads were fouling the crank pins. We narrowed the frames, which pulled the cylinders (and the center bore of the cylinders) in by at least 3/16" per side, but I never had accounted for this when building anything else. Could it be that simple? Do I only need to machine some shim plates to bolt between the cylinders and frame to extend them out to their proper dimensions? I hope so! I will work on that next week.
"One cannot learn to swim without getting his feet wet." - Benjamin Maggi
- Building: 7.25" gauge "Sweet Pea" named "Catherine"

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NP317
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Re: "Catherine", a USA "Sweet Pea" engine build

Post by NP317 » Wed Apr 27, 2016 9:39 am

An "AH HA!" moment!
Keep us informed.
~RN

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

Post by Benjamin Maggi » Tue May 03, 2016 5:31 pm

Unfortunately, the more I think about it, the frame were never narrowed at all. They are just as wide as the plans call for. However, we did decide to purchase some cold rolled steel and shim out the cylinders from the frame by 1/4," which should provide plenty of clearance. Other things in the value gear may need to be adjusted for this, but that won't be so tough.
"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 » Wed Jun 08, 2016 4:00 pm

The wife and I just bought our first house. While the basement is suitable for at least a small shop (thank goodness for Bilco doors!), the Sweet Pea project is temporarily on hold during the transition period.
"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 » Wed Jun 08, 2016 5:39 pm

Congratulations! When you can one day soon get your Catherine going again, you will have a new focus!
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 » Tue Mar 28, 2017 6:07 pm

When I left this project last summer, I was pretty dejected because the cylinders and valve gear were fouling each other and I really didn’t know what was going on. I was building the engine per the prints, but unlike the Sweet Pea (5” gauge loco) there were very few Sweet Williams running in the world. So, the plans haven’t been confirmed by multiple builders and it is possible some things are wrong. However, since it is a British plan drawn for 7.25” gauge and that is what I am building it to (as opposed to someone building a 7.5” gauge engine) I am at a loss.

Finally, I started tackling the projects one piece at a time. For some reason, the cylinder bores were about 1/4" closer to the frame than the plans called for and as a result, there just wasn’t enough clearance with the valve gear. So, I purchased some ¼” thick steel plate and made some shims for the cylinders to extend them further out from the frame. Even though all of the holes that had to be drilled were essentially just clearance holes for the mounting bolts, I still used care in trying to get them perfectly aligned. Even still, not every hole lined up perfectly and some filing was required. I didn’t want to do any filing, so I let the project sit for months while my wife and I moved into our new house.

Finally, after months of putting it off I did the necessary filing and finished the first shim. I was really annoyed at how badly I had made it and how much filing was required, so I took much more care in making the second shim using paper templates. This time, it came out perfect. I was so encouraged by this that I threw away the first shim and remade it. Thus, in about an evening’s worth of work I had done what I had dreaded for months. But, at least my project was back on track (so to speak).
Cylinder shim.jpg
Cylinder shim.jpg (39.04 KiB) Viewed 2974 times
"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 » Tue Mar 28, 2017 6:09 pm

With the cylinders shimmed out, I again assembled the slide bar and crossheads and then realized the motion plate which secured the end of the slide bar to the frame was now ¼” off, and the valve spindle coming from the cylinders would never line up with the crosshead. So, I also had to shim the motion plate out by ¼.” Frankly, this should have been a simple thing to do. However, before I had the proper set I had made eleven different brackets. And I managed to mess them up in a multitude of ways. Some I cut too short in length so I didn’t have enough room to drill all the required holes. A couple were made with the slide bar not in its correct position, so that once the brackets were installed the slide bar was not parallel to the cylinder bores. Some were rushed and the holes weren’t properly laid out. All in all, I was pretty embarrassed by my efforts.
Motion Plate bracket.jpg
Motion Plate bracket.jpg (37.51 KiB) Viewed 2974 times
So, I bought an 18” length of angle and cleared everything off my work desk. Without any distractions like music or my dog, I carefully transferred all of the dimensions and hole locations to the steel and allowed plenty of extra length on either end so I wouldn’t have to remake them because of that.

Thankfully, this time my patience was rewarded and they not only fit the frame perfectly but the crosshead was exactly parallel and in alignment with the cylinder bore. It looks a little clunky, and the motion plates would look nicer if they were wide enough to fully meet the frame, but for now I will live with it. I can always have them water-jet again if I want. Once it is all painted black, it will likely disappear in the shadows anyway.
11 motion plate brackets.jpg
11 motion plate brackets.jpg (29.73 KiB) Viewed 2974 times
"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 » Tue Mar 28, 2017 6:09 pm

Since I had the wheel/axle assemblies out of the frame, I decided to address another problem that was bugging me. The dual axle pump that we had designed was about 3/16” too far from the eccentrics, and instead of remaking the rods we had shimmed the pump out with two thin pieces of metal that the mounting bolts passed through. It worked fine, but anytime you had to remove and reinstall the pump you had to carefully line the shims up without really being able to see them. It worked okay when the chassis was vertical, but in real life it would be horizontal and nearly impossible to do. So, I purchased some 1/8” thick aluminum plate that was the same size as the pump and drilled all the clearance holes in it. It was much easier to hold and align when working on the pump.
"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 » Tue Mar 28, 2017 6:10 pm

As I was making the crank pins I became very concerned with the side-to-side play of the wheels in their axle box assemblies. I had added horn “shims” made from 3/16” steel to the inside of the frame, which had the effect of moving the axle boxes inward on the chassis. This was done to provide some extra clearance between the backs of the wheels and the frame. (See page 5 of this thread) However, there was currently about ¼” of sideways travel. This not only could cause the rods to bind if the wheels shifted in different directions or prematurely wear out the crank pins, but at the same time if the wheels were equally shifted to one side or the other the crank pins fouled the cross heads. It was time to fix that slop.
Crank pin hitting crosshead.jpg
Crank pin hitting crosshead.jpg (35.62 KiB) Viewed 2975 times
So, I removed the horns one by one and replaced them with 1/8” steel. Once installed, the back-and-forth was significantly reduced to just a little. At the same time, the clearance issues between the crank pins and the crossheads looked to be fixed.
"One cannot learn to swim without getting his feet wet." - Benjamin Maggi
- Building: 7.25" gauge "Sweet Pea" named "Catherine"

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