EMD F7 in SCALE

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Racie35
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Re: EMD F7 in SCALE

Post by Racie35 »

Thankyou
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Steggy
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Re: EMD F7 in SCALE

Post by Steggy »

BigDumbDinosaur wrote: Thu Dec 03, 2020 12:53 pm
rkcarguy wrote: Thu Dec 03, 2020 12:03 pm The pattern I saw on an F7 with mars light on Youtube, appeared to be an oval pattern about as tall as the train and maybe 2-3x the width.
I'm thinking you just make a ball bearing follower connected to an oval shape "cam" with a spring on it, and then use a slotted arm on a motor to turn it about 30rpm?

https://www.youtube.com/watch?v=mB0_yt-mIE4
That is a Pyle-National Gyralight on that locomotive. The Chicago & Northwestern (the road I'm modeling) used Mars lights, which produced the Lissajous pattern.
I stand corrected. It turns out there were some C&NW F-units that were equipped with Gyralights.

Unlike the Lissajous beam pattern produced by the Mars light, the elliptical beam pattern of the Gyralight could be developed with a less-complicated mechanism, which would simplify maintenance. I'm sure knowing that delighted the C&NW mechanical department to no end.

Due to space constraints, I may end up modeling the Gyralight. I've already got the light source. All I gotta do is design the mechanism. :D
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Re: EMD F7 in SCALE

Post by Steggy »

EMD F7 in SCALE
————————————————
THE F-UNIT GETS NEW TRUCKS: Part I

Many of the more recent past posts have been about body construction. I thought I'd digress a bit and return to the body later on.

Quite a few posts back, I kvetched about the Bob Snippe-built trucks and how I had to substantially rework them to achieve satisfactory operation. Although the trucks handled marginal track quite well following their rework and replacement of the wheelsets, their appearance left something to be desired for several reasons.
  1. Length-wise, the trucks are scaled to slightly less than 1.5 inches per foot, however the loco is built to 1.6 inch scale. Hence the trucks look too short for the locomotive, especially the one at the number one (cab) end, since it is right behind the pilot to give the casual observer some perspective.
  2. Width-wise, the trucks are grossly out of scale, being much too wide. In fact, if I had used cab ladders that were exactly to scale, they would have interfered with the truck side frames when negotiating anything more than a gentle curve. I ended up shortening the ladders enough to assure clearance no matter how much the truck swiveled.
  3. Details, such as the bolster spring packs and brake rigging, are sparse and crude. The bolster "springs" are cast into the side frames and no attempt was made to make the "springs" look like springs. The brake rigging parts I did get with the trucks were the shoes and cylinders—no linkage whatsoever. The shoes and cylinders are aluminum castings and prone to breakage.
  4. Snippe didn't incorporate brake shoe hanger beams into the finished product. I had to fabricate and add those so there would be a place to mount the outer brake shoes.
I know: more kvetching. :D However, see exhibit A below and you will (I hope) understand my whining and complaining.

Snippe Truck After Rework
Snippe Truck After Rework

Anyhow, I was willing to live with what I had when I got the unit on its wheels, since it didn't seem there was any alternative available. That thinking changed when I was at one of the big annual meets we have at our railroad. A visitor had brought an F-unit built by Dave Newell and in examining it, I saw how in-scale and well-detailed the trucks were, and wondered if I could adapt them to my F-unit. Below is an example of Dave's rendition of the Blomberg truck.

Pike River Blomberg Truck
Pike River Blomberg Truck

Adaptation to my F-unit would not be trivial—Dave's trucks are meant for use with axle-hung, geared, electric traction motors, not the bolster-hung, hydraulic motors with roller chain drive I was using in the old trucks. Also, my method of interfacing the truck bolster with the F-unit's frame is quite different. Then there is the matter of brakes...I was using pneumatic disc brakes on my trucks, but Dave's trucks had realistic brake rigging that could be made functional, a feature I decided to forego.

So I let the idea simmer for about a year as I concentrated other things. When it appeared I'd have some time to work on the project and flesh out details, I contacted Dave to get things rolling (no pun intended). In order to adapt the trucks, I would need accurately-scaled drawings of the frames, bearing boxes and spatial relationships between the wheelsets and everything else so I could "build up" the assembly in cyberspace before doing so in reality. As I would be purchasing castings and assorted loose pieces instead of an assembled truck, I would also need to determine how I was going to put the mess together with reasonable precision. Succinctly, I had to work out all aspects of the project and be satisfied I could complete it before committing to anything, since more than a little money would be involved.

Dave was willing to help me out with drawings and I worked on the adaptation for several months until I was confident I had addressed all foreseeable issues. Key design matters were the spatial relationship between the traction motor and the truck frame, the bolster topside arrangement, compatible wheelsets, and adapting my disc brake design. I'll start with the traction motors, since that was where most of the complication existed.

The traction motor is suspended from the bolster and power is transferred to the wheelsets with ANSI 40 roller chain, using two end-to-end sprockets on the motor, one chain per wheelset and one sprocket on each axle. This arrangement causes the tensile forces generated by the two chains to approximately cancel, resulting in very little overhung load being applied to the motor shaft. Not having to carry heavy overhung loading minimizes bearing wear that would otherwise eventually lead to shaft seal leakage.

In doing the initial layout of the motor mount, it quickly became apparent that the Dynamic BMPH motors I was using in the old trucks were not going to fit into the new ones, as they were about 5/8 inch too long. Due to the location of the brake rigging, I had to place the motor sprockets inboard enough to keep one of the roller chains from tangling with the inboard rigging trunnion (the long bar that links the bottoms of the brake shoe hangers together). Unfortunately, the BMPH motor would not have cleared the truck frame on the other side—a real show-stopper if I couldn't devise a solution.

The solution, of course, was to find a motor of the correct displacement, but approximately 5/8 inch shorter than the Dynamic motors. It turned out that a Chief BDH motor with slightly higher displacement would fit—barely. I purchased a pair of them and made an accurate drawing so I could "install" it into the truck frame drawing. During that process, I could see I was going to have to rework a part of the truck frame to clear the bottom of the motor, but it would be a relatively simple process.

Once the traction motor problem had been resolved the rest of the process was working out power transmission details, designing a compatible bolster and figuring out how to mount it to the truck frame. The truck was designed to have its bolster welded in place, but I needed it to be removable, otherwise installing or removing the traction motor would not be possible. The solution was rework yet another truck part to accept bolts to retain the bolster. The bolster is also a little strange-looking in order for it to clear welds critical to the structure.

A factor affecting traction motor mounting and power transmission to the wheelsets is truck wheelbase. There is a significant difference between the new truck's wheelbase, approximately 14.4 inches (within a tiny fraction of a percent of 1.6 inch scale—prototype wheelbase is 108 inches) and the old truck's wheelbase, which is approximately 13.2 inches—but should be 13.5 inches to be in 1.5-inch scale. The result is the motor centerline to axle centerline nominal distance is approximately 0.6 inches greater with the new trucks. ANSI 40 chain is 1/2 inch pitch, which cannot evenly accommodate the span, necessitating that the motor be slightly off-center fore-and-aft, and one chain equipped with a half-link (aka offset link). Some adjustment is provided in the motor mount to set chain slack to approximately equal amounts for both sides.

In order to spread out wear-and-tear on the chains and sprocket teeth, I use a "hunting" drive ratio, which simply means there is no common prime between the number of teeth on the axle sprocket and the number of teeth on the motor sprocket. In the old trucks, I used 15:14 (factoring 15 gives you 5 and 3, whereas factoring 14 gives you 7 and 2, ergo it's a hunting ratio). Doing some math suggested that larger sprockets might be necessary due to the longer wheelbase affecting the number of chain pitches required. I couldn't go smaller than 14 teeth on the motor due to available bore sizes. However, clearance between the motor and the underside of the bolster limited the motor sprockets to 17 teeth—a larger sprocket would make assembly difficult. Mounting the motor lower to give the sprocket more room was not an option, since I also had to be mindful of clearance over the railhead. I juggled these relationships in CAD for a while before I finally determined that I could achieve acceptable chain slack with the existing 15:14 ratio and a half-link in one of the chains.

With all of that malarkey worked out, it was time to cogitate a bit on how I was going to jig the truck frames for welding. Just so you know what I was working with, below is a photo of the parts needed to build one truck. Not seen are wheelsets or fasteners for assembling the brake rigging.

Blomberg Truck Pieces
Blomberg Truck Pieces

Basically, the truck frame is a weldment of six pieces: two side frames, two brake shoe hanger beams and two upper bolster spring suppports (visible immediately above and to the right of one of the side frames). The latter items would also serve as the attachment point for the removable bolster.

Note the brake shoe hanger beam with the drop in it. As the project moved along, I determined that the drop was a liability—it complicated jigging, and I didn't need the extra clearance it offered, so I exchanged the drop beams for straight ones like the other one in the photo.

BTW, everything except the brake shoes and some spacers that are part of the brake rigging is iron (more correctly, C1030 cast steel). Needless to say, these things would not be light once fully assembled. The nice thing about cast steel, though. is its strength and good welding properties. Plus the material's general texture looks somewhat like the full-sized truck's castings.

The first step was to work out how to jig the frame pieces for welding. I needed to have the side frames spaced the correct distance from each other and accurately aligned fore-and-aft. Also, they need to be vertically plumb, otherwise, things might bind up as the wheelsets moved over uneven track. Here's are drawings of the fixture I designed. This was a project in itself.

Truck Frame Welding Fixture Design
Truck Frame Welding Fixture Design
Truck Frame Welding Fixture Design
Truck Frame Welding Fixture Design

Here's is the fixture ready for use.

Truck Frame Welding Fixture
Truck Frame Welding Fixture

My buddy Carl did the milling for me, as I don't have a mill in my shop (and no place to put one as well). Fixture in hand, I was ready to weld up the truck frames. I'll continue in the next post.
Last edited by Steggy on Mon Dec 13, 2021 1:29 am, edited 1 time in total.
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Re: EMD F7 in SCALE

Post by Steggy »

EMD F7 in SCALE
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THE F-UNIT GETS NEW TRUCKS: Part II

During the design phase of the truck project, I determined I would have to modify some parts to get things to fit. The first item that underwent "butchering" was the upper spring support.

In the full-sized Blomberg truck (below photo), this support is actually the truck's bolster, which means it is the point of attachment between the truck assembly and the carbody. The bolster also acts as a reaction point for the traction motors.

blomberg05_reduced.jpg

The bolster's ends rest on leaf spring packs which, in turn, rest on "planks" that are attached to the truck frame via swing links. This is the means by which the weight of the locomotive is supported by the truck frame. The bolster "floats" in the truck frame, both laterally and vertically. Bumpers on the inside of the truck frame limit the amount of lateral float.

The floating bolster and swing link arrangement helps to reduce lateral shock loads caused by the locomotive's polar moment of inertia as the unit enters a curve at high speed, or when negotiating horizontally uneven track. The link geometry is such that the weight of the locomotive produces a natural tendency for the unit to stay centered on the truck on tangent track, while at the same time causing the locomotive to slightly "lean into" a curve. This design has proved to be very sound—passenger F-units could safely run at 100+ MPH on the bolted mainline track of the 1940s and 1950s. The EMD E-unit's truck was basically the same design with a third axle.

In the model truck, the bolster is solidly attached to the truck frame and a separate spring support takes up the space occupied by the bolster's ends. This support is meant to be purely cosmetic and not intended to have anything attached to it, other than the top of the leaf spring pack. I changed that configuration to attach the bolster, since it has to be removable. Hence a little rework to the support was needed.

First step was to set up the support in the mill and take a light cut from the top surface to get it flat and square. That done, three precisely-located holes were drilled for tapping to accept 1/4"-20 capscrews. Due to the size of the spring support and the amount of "meat" available, these holes are limited in diameter. I should note that during operation, the capscrews anchoring the bolster to the supports only resist driving, braking and lateral forces, and play no role in supporting the weight of the locomotive. Therefore the screw diameter isn't critical—the single-shear strength of six grade-eight quarter-inch capscrews is some 20 times the maximum forces that could ever be expected, even in the event of a derailment.

Following the milling and drilling, the pieces were transferred to the drill press to tap the holes.

upper_spring_support.jpg
tapping_spring_support.jpg

The first photo is of the spring support prior to rework. The second pic was taken with the freshly-milled part ready for tapping. Incidentally, I got double-duty out of those drilled-and-tapped holes, as will be seen in the photos of the truck frame jigged for welding.

With the upper spring support handled, attention was turned to the lower spring "plank" (next photo).

spring_plank.jpg

You are viewing the underside of the plank before rework.

As with the upper spring support, the plank is a cosmetic feature, albeit an important one. During the design phase, I determined that the inboard end of the plank would have to be shortened, as it would otherwise interfere with the traction motor. There is a step cut into the plank that locates the inboard spring hanger, that step being important to achieving correct assembly. Ergo the step's position set the limit on how much I could shorten the piece, and was an area in which I had to carefully lay out things during the design phase.

I made a small holding fixture to support the plank in the horizontal band saw and sawed it just inboard of the step. Some dressing in the belt sander cleaned up everything. Here are photos of the plank after rework.

spring_plank_rework_tv.jpg
spring_plank_rework_sv.jpg

With parts rework completed, things were in a state where I could commence the actual build. Stay tuned...
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Music isn’t at all difficult.  All you gotta do is play the right notes at the right time!  :D
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EMD F7 in SCALE

Post by Steggy »

EMD F7 in SCALE
————————————————
THE F-UNIT GETS NEW TRUCKS: Part III

In the previous post, I described the reworking that had to be done to some parts to accommodate my modification of the trucks. With that phase of the work completed, I was ready to build up the truck frames.

As noted in the first post of this series, the truck frame is a weldment of six pieces: side frames, brake shoe hanger beams and upper spring supports. Concerned that things might move around during welding and cause intractable misalignment, it was clear a fixture was needed to positively locate everything, as well as to prevent stupid assembly errors. Designing and building this fixture was a project in-and-of itself.

Assembly went in steps.
  • I started off by attaching the upper spring supports to a locating bar that is part of the fixture. This bar was then set down onto jacking studs projecting from the fixture's baseplate (below photo). This is where I got double-duty from the holes that had been drilled and tapped into the supports—they became the attachment point for the locating bar. I should mention this locating bar was carefully milled so its length is very slightly less than the theoretical span (9.700") between the inside faces of the side frames. Note the reliefs in the ends of the locating bar to facilitate welding.

    fixture_spring_hanger02.jpg
  • Next, the side frames were set into place. These items are located in both directions in the fixture by some thick aluminum blocks whose ends are milled to engage the bearing box (aka journal box) pedestals (below photo). In passing, I should mention some of the fixture's parts were intentionally made massive to keep a lid on expansion during welding.

    Here's where I ran into a bit of trouble. During the design of the fixture, I had consulted drawings that had been supplied by Dave Newell to dimension parts and their locations. I discovered the truck's wheelbase, and thus the relative pedestal locations, was about 0.030" longer than called out in the print—that discovery, of course, being made after the fixture had been built. :twisted: Fortunately, it was a correctable error.

    fixture_sideframe01.jpg
  • With the side frames mounted in the fixture, the next step was to secure two tie rods in between the side frames' inside faces to keep the frames parallel in the vertical, as well as perpendicular to the fixture baseplate. I used two holes that were cored through the side frame castings as bolt holes (below photo).

    fixture_tie_rod02.jpg
  • Next, a clamp bar was set onto the jacking studs to bear down on the tops of the side frames and firmly hold them against the fixture's base plate (below photo). I successively tightened the clamp bar, then the tie rods, to assure everything was squared up.

    fixture_clamp_bar03.jpg
  • With the side frames secured in place, the locator bar to which the upper spring supports were attached in step 1 (above) was jacked up to bring the supports in contact with the side frames (below photos). The goal was to make firm contact, but not put undue pressure on the supports and/or side frames and mess up alignment.

    fixture_sideframe02.jpg
    fixture_spring_hanger04.jpg
Continued in next post...
Last edited by Steggy on Fri Jun 11, 2021 10:46 pm, edited 1 time in total.
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Music isn’t at all difficult.  All you gotta do is play the right notes at the right time!  :D
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Steggy
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EMD F7 in SCALE

Post by Steggy »

EMD F7 in SCALE
————————————————
THE F-UNIT GETS NEW TRUCKS: Part III, cont'd

Continuing from the previous post:
  • With the side frames and upper spring supports secured in the fixture, the brake shoe hanger beams were next. The beams are made so they are slightly shorter than the inside span between the side frames to facilitate assembly. Also, the gap between the beam ends and the side frames means it is possible to achieve a flat penetrating weld without having to crank up the welder real high and risk distortion and/or cracking. A flat weld, in turn, means less grinding is needed to blend and beautify the joint. :D

    Two "troughs" bolted to the ends of the fixture baseplate hold the beams in place (below photos). Short bolts keep the beams from moving around during welding, as well as locating them fore-and-aft in the fixture.

    fixture_brake_shoe_hanger_beam01.jpg
    fixture_brake_shoe_hanger_beam02.jpg
  • With the six pieces that make up the weldment in place, I double- and triple-checked my work and prepared to do some welding.

    fixture_truck_ready01.jpg
    truck_fixture_ready.jpg
  • The last step in the truck frame build-up was to spray everything with anti-spatter compound and make some sparks. The frame was MIG-welded at approximately 130 amps, using Airgas P/3 0.035" wire and 75/25 shielding gas. The less-aggressive arc produced with 75/25 tends to reduce spatter and makes for smoother welds than when using CO2. Penetration is not as great for any given voltage and feed setting, but in this application, that was not an issue.

    Here are some photos of the frames after welding, but before any cleanup.

    truck_frame_welded01.jpg
    truck_frame_welded02.jpg
Stay tuned for more...
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Music isn’t at all difficult.  All you gotta do is play the right notes at the right time!  :D
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EMD F7 in SCALE

Post by Steggy »

EMD F7 in SCALE
————————————————
THE F-UNIT GETS NEW TRUCKS: Part IV

After the truck frames had been welded, I blended the welds securing the brake shoe hanger beams to the side frames and then attached the spring planks and leaf spring packs. As the springs are merely cosmetic they are welded to the upper spring supports and planks. As part of the process, the hanger links were installed, which are also welded. Below is are photos of one of the spring packs.

spring_pack01.jpg
spring_pack02.jpg

Other pieces that are part of the spring assembly are in the next photo. Note the links—the ones on the right are those exposed on the exterior of the truck.

spring_hanger_parts_cropped.jpg
Installing these parts were straightforward welding—I didn't photograph any of the intermediate steps. I used 10-24 machine screws to temporarily secure the spring packs to the planks before welding. The below photo is of one of the truck frames after being cleaned up and primered.

truck_frame01.jpg
The next photo is a closeup of the finished spring assembly. Here I added a small detail to the assembly.

The full-sized truck has a retention rod that keeps the hanger link pins from drifting out of the side frame ears. That was not part of the model. I added that feature by axially drilling the hanger link pins and then cutting up an 1/8 inch welding electrode into "retention rods" of the correct length. Small tack welds secure the "retention rods" to the hanger link pins, with a little careful grinding of the pin ends to blend the tacks. The result is a reasonable facsimile of the original's retention rod (below photo).

truck_frame02.jpg
In the next post, I'll describe the design and fabrication of the truck bolster. Don't touch that dial!
Last edited by Steggy on Mon Dec 13, 2021 1:34 am, edited 2 times in total.
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Music isn’t at all difficult.  All you gotta do is play the right notes at the right time!  :D
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Re: EMD F7 in SCALE

Post by Steggy »

EMD F7 in SCALE
————————————————
THE F-UNIT GETS NEW TRUCKS: Part V

Having built the truck frames, I turned my attention to bolsters. Next to the building of the truck frames, fabricating and assembling the bolsters was the most complicated procedure in the truck build.

First, here's is a drawing of an assembled bolster. Seeing it will make it easier to understand how the pieces went together.

bolster_assy_in_cad.jpg

As can be seen, the traction motor is supported on a formed bracket, which is made so the motor can be moved fore or aft to correctly set roller chain slack. On top of the bolster can be seen the anti-roll bearings that keep the unit plumb to the track. These are small ball bearings that make contact with wear pads on the frame. They carry most of the unit's weight—the center bearing's primary purpose is to attach the truck to the frame.

In the center of the bolster is a tapping plug that is used to secure the center bearing to the bolster (below photo).

bolster_tapping_plug01.jpg

A socket capscrew passes through the bearing's hub and threads into this plug. In order to reduce the clearance between the anti-roll bearings and the wear pads they contact, the tapping plug's shoulder is slightly shorter than needed and standard shaft shims are placed between the center bearing hub and tapping plug to get the right fit.

Midway through this project, I made a detail change to the center bearing mounting to eliminate the spacer seen in the above drawing on the top of the bolster. The above tapping plug replaces that spacer, so it still works the same; there's just one less part to assemble.

Incidentally, the triangular-shaped bracket projecting from the side of the motor mount acts as the reaction point for the disc brake caliper.

To make the bolsters, I started with two pieces of 1/2 inch thick, 4 inches wide cold-finished steel, which would become the bolster beams. These pieces were sawed slightly oversized, and then milled to get the ends square and to establish the finished length. The ends were stepped so the bolster will sit at the correct height relative to the rest of the truck. The depth of the step is such that one or more shims must be used between the bolster beam and the top of the upper spring support, which is the anchorage for the bolster and hence the main load-bearing joint in the truck. By using shims, I can correct for minor height differences on each side of the truck so lateral loading is even.

Reliefs were cut into the bolster beams' ends to clear the welds securing the upper spring mounts to the trucks' side frames. While in the mill, holes were spotted for later finishing in the drill press. Due to the need for the center bearing tapping plug to closely fit the beam, the center hole was finished to size with a piloted counterbore (below photo).

boring_center_hole.jpg

Below is a photo of a machined bolster beam ready for further assembly. The two holes to the immediate right of center are tooling holes that will be put to use later on.

bolster_beam_machined.jpg

Meanwhile, a local fabricating company equipped with high-powered laser cutters, big brake presses and other machines whose cost would bring tears to the eyes of a multi-millionaire, was tasked with making the traction motor mounts, anti-roll bearing brackets and disc brake reaction brackets. What's handy about dealing with them is I can E-mail drawings in .DWG or .DXF format and they can extract the required data from them to program the laser cutter. Any errors that creep into the finished part will be of my doing. :oops:

In the distant past when I was much healthier and had access to a variety of machines (including a big brake press and an NC-controlled turret punch) at my place of employment, I would have fabricated these pieces. These days, I don't have access to that sort of machinery, and my stamina in the shop isn't what it used to be (probably because I'm an old stick in the mud with a malfunctioning heart :D). That being the case, the work required to whittle all that steel to the desired shapes and sizes is more than I can easily handle. So that means paying someone to do some of the work for me. The upside to this is the fabrication shop is very good at what they do.

With the motor mounts in hand, I attached the disc brake reaction brackets and on one mount, a pulse generator mounting bracket. The usual cleanup and primer followed.

traction_motor_bkts01.jpg

At this point, I attached the bolster beams to the truck frames, which had been set on their wheelsets, placed a motor mount with motor attached under the bolster beam, and did a dimensional check (below photo). Despite my best efforts to the contrary, everything fit according to the drawings.

bolster_fit_check01.jpg

Continued in the next post...
Last edited by Steggy on Sun Jun 13, 2021 7:49 pm, edited 2 times in total.
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Music isn’t at all difficult.  All you gotta do is play the right notes at the right time!  :D
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Re: EMD F7 in SCALE

Post by Steggy »

EMD F7 in SCALE
————————————————
THE F-UNIT GETS NEW TRUCKS: Part V, cont'd

Having determine that things would fit as designed, I continued with the bolster fabrication. The anti-roll bearing brackets were welded in place. A precision-machined spacer was used to get the brackets in the correct locations and keep them square during welding.

bolster_welded01.jpg

Next, the traction motor mounts were jigged. A spacer block was bolted into the tooling holes mentioned in the previous post and the motor mount clamped to the spacer.

mm_jigged02.jpg

After carefully checking the fit, I fired up the welder and made some sparks.

bolster_welded02.jpg
bolster_welded03.jpg

Once the weldments had cooled, I pressed the tapping plugs into the bolster beams and welded them as well. Following more cool-down, I assembled all parts and carefully checked fit.

bolster_assy01.jpg
bolster_assy02.jpg

No hammers were harmed during the assembly process.

Continued in next post...
———————————————————————————————————————————————————————
Music isn’t at all difficult.  All you gotta do is play the right notes at the right time!  :D
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Re: EMD F7 in SCALE

Post by Steggy »

EMD F7 in SCALE
————————————————
THE F-UNIT GETS NEW TRUCKS: Part VI

Here are some more photos of the bolster assembly as I checked that everything was copacetic.

bolster_assy04.jpg
bolster_assy06.jpg
bolster_assy07.jpg

In the previous post, I mentioned in passing the wheelsets.

Dave Newell provided the wheels with a modification that I requested. I also needed axles made, which Buxton Machine (forum user LIALLEGHENY) took care of for me. The axles are made from C1144 TGP, which is my "go-to" material for axles and other kinds of shafting. The below photo is of the axles when I received them.

axles_new01.jpg

With wheels, axles and other parts in hand, I built up the wheelsets. The wheels are a press fit on the axles—about 3-4 tons was required. As a belt-and-suspenders measure, the wheels are keyed to the axles. :D What follows is a series of photos as I assembled the wheelsets.

wheelset_assy01.jpg
wheelset_assy02a.jpg
Continued in the next post...
———————————————————————————————————————————————————————
Music isn’t at all difficult.  All you gotta do is play the right notes at the right time!  :D
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Re: EMD F7 in SCALE

Post by Steggy »

EMD F7 in SCALE
————————————————
THE F-UNIT GETS NEW TRUCKS: Part VI, cont'd

More photos of wheelset assembly.

wheelset_assy04a.jpg
wheelset_assy04b.jpg

Above, one wheel has been pressed to the axle, and the sprocket, disc brake caliper bracket and rotor have been fitted.

wheelset_assy06a.jpg

Above, the other wheel has been pressed on, along with the wheel bearings.

wheelset_assy08a.jpg

Above, the brake caliper has been attached. The wheelset is assembled.

wheelset_assy09.jpg
wheelset_assy10.jpg

Above are the finished wheelsets, ready for installation into the trucks.

Stay tuned for more...
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rkcarguy
Posts: 1730
Joined: Tue Aug 22, 2017 10:33 am
Location: Wa State

Re: EMD F7 in SCALE

Post by rkcarguy »

Very Nice BDD.
Food for thought. I put valve springs on my bolster pins (3/4" bolts), such that they keep a constant pressure on the "anti-roll bearings" so no shims are needed and there will be no click-clack if they are left a bit loose. I run the spring about 1 turn on the nut/bolt from coil bind, so that if the locomotive is picked up and the trucks left to hang they won't flop all over the place.
I built mine upside down compared to your design, so the spring would go on top in your build between the spherical bearing and the head of the bolster bolt.
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