3" Scale Narrow Gauge Combine

Where users can chronicle their builds. Start one thread and continue to add on to it.

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Loco112
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Re: 3" Scale Narrow Gauge Combine

Post by Loco112 »

The varnish is looking great. The MG&W is lucky to have you Mike. Now what that group needs is a locomotive project.
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Harlock
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Re: 3" Scale Narrow Gauge Combine

Post by Harlock »

Hello all. The project moves forward. There were a lot of little things to do to the frame, and it's now basically ready for painting.

In the first photo we see the frame turned upside-down. Trussrods are in and functional. It does not take much rotation of the turnbuckle to curl up the frame. This will come in handy later if it begins to sag from the weight of the body, just like prototype. Although with the steel bar featured a few posts down, this is unlikely to happen.

The main difference between the model and the prototype is that our trussrods end at the truck bolsters whereas on the prototype they carry through to the end sills via a gap in the bolsters.

We have placed pivots so that the bar does not bend and stress the connection to the bolsters.

The bolsters have aluminum-on-rubber pads that meet the truck bearing surfaces.

(continued in next post)
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Last edited by Harlock on Fri Jun 03, 2016 2:15 am, edited 1 time in total.
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Harlock
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Re: 3" Scale Narrow Gauge Combine

Post by Harlock »

The end platform extensions are separate bolt-on pieces that are a modification of the original which also uses separate pieces but attached in a more complicated manner.

These slip in underneath the main sills and mate with the ends. To bolt them together, round head bolts are used inside of counterbored holes which will be hidden beneath decking. A boring tool with a pilot hole guide is used.
Attachments
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16-05-26_combine-update-4616.jpg
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16-05-26_combine-update-4634.jpg
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Harlock
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Re: 3" Scale Narrow Gauge Combine

Post by Harlock »

Another deviation from prototype is the addition of a steel bar down the center of the frame, which will tie in directly to the two draft gear assemblies on either end. On our very steep 9" gauge railroad with big heavy cars, the potential for strong impacts is high if something goes wrong, so we want to protect the wood frame of the car from taking the brunt of the force. The draft gear goes a long way towards that, and this will absorb the rest.

The bar has flanges welded on either end, and is captivated by a notch in the queen post buffers on the bottom and the decking on top so even if there was enough force to cause it to bend significantly (which would be very difficult) it should be prevented from bending by its capturing elements.
Attachments
16-05-26_combine-update-4639.jpg
16-05-26_combine-update-4645.jpg
16-05-26_combine-update-4647.jpg
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Harlock
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Re: 3" Scale Narrow Gauge Combine

Post by Harlock »

Finally, a sneak peak of the combine resting on one of the trucks.
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16-05-26_combine-update-4623.jpg
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makinsmoke
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Re: 3" Scale Narrow Gauge Combine

Post by makinsmoke »

Mike,
Beautiful work you are doing. Ground up prototypical
car construction of wood cars is fun in these scales.
If you take the time like you are you can essentially
build them just like the prototypes.

I do beg to differ with your comment that passenger
cars were built lighter than freight cars. If you look
at the framing of these cars, particularly the Colorado
narrow gauge prototypes, including cabooses
where the sheathing has been removed, the framing
is built exactly like freight cars. The only differences
are where doors and windows, roofing and of course
the finish is concerned.

After all, all of these cars, freight and passenger,
are essentially wood framed bridges with a roof,
and end framing to resist side flexing.

The passenger cars actually had to have more
strength in the long plane due to their longer length,
but they are all just bridge frames on wheels and
have to be built that way, no matter what they carry.

Keep the photos coming!
Brian
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Harlock
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Re: 3" Scale Narrow Gauge Combine

Post by Harlock »

I've been negligent in updating this thread. Progress continues. The frame was painted except for the top surfaces, which we wanted to keep perfectly flat, they are all hidden except the end buffers. The coupler and draft gear are installed and some diagonal bracing to shore everything up. The car is very strong now and should be able to pull any train behind it up the steep grades at the Mesa Grande. (6% in one spot)

We slotted the siding for the spline and groove construction method. The strips were pre-milled sans-slots by a local wood supplier, so we just had to put the slots in. Once again our typical slotting setup on the portable router table, with liberal use of fingers for both horizontal and vertical pressure.

When the siding comes out, it is rotated horizontally around and fed back in, so the same side is still 'up' and any small discrepancy in the centering of the cutter is negated.
Attachments
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Harlock
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Re: 3" Scale Narrow Gauge Combine

Post by Harlock »

The interior floor was laid down, with a gap around the outside where the walls willl attach. All of the walls are individually removable for whatever kind of maintenance might be required down the road. The whole body will dissasemble. Also, a strip in the middle of the floor is removable to access the center beam.

The various doors were started as well. There are two end doors and an interior door to separate the baggage area.
Attachments
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16-11-26_combine-0984.jpg
16-11-26_combine-0985.jpg
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Last edited by Harlock on Fri Mar 31, 2017 1:04 am, edited 1 time in total.
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Harlock
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Re: 3" Scale Narrow Gauge Combine

Post by Harlock »

Here is an interesting technique for making quarter rounds in doorways. A radiused router bit is used to make a donut hole in a piece of wood. It is then placed in a fixture and the outside diameter turned on the lathe.

After that it is quartered, and due to the saw blade width you get to keep two out of four pieces on each donut as a full 90 degree item.
Attachments
16-11-26_combine-0994.jpg
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16-11-26_combine-0996.jpg
16-11-26_combine-0998.jpg
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Harlock
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Re: 3" Scale Narrow Gauge Combine

Post by Harlock »

Another complicated item is the corner radii of the car body. To mill all the features into this, it was temporarily glued to a fixture along the way then removed again. I do not have pictures of this operation unfortunately.

The nearly finished but unpainted end is shown.
Attachments
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16-11-26_combine-1001.jpg
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16-11-26_combine-1004.jpg
16-11-26_combine-1006.jpg
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Harlock
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Re: 3" Scale Narrow Gauge Combine

Post by Harlock »

And here are the finished ends attached to the car. They are bolted from underneath with a threaded insert in each lower end wall.
Attachments
17-03-22_combine-ends-6558.jpg
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17-03-22_combine-ends-6556.jpg
17-03-22_combine-ends-6566.jpg
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Harlock
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Re: 3" Scale Narrow Gauge Combine

Post by Harlock »

Here is the car as it is today, with one more shot of the inside of the passenger end. And a start on one of the freight doors. The next step is mass production of many, many side windows.
Attachments
17-03-22_combine-ends-6575.jpg
17-03-22_combine-ends-6577.jpg
17-03-22_combine-ends-6573.jpg
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