A&O Railroad Forum
Member Railroads => Member Projects => Topic started by: Bob on February 28, 2024, 08:21:49 AM
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The Pittman 8414 and its shorter brother 8313 are two of the most common motors used in O-scale diesels. However, they are physically large and known to be current hogs. The 8414 armature resistance is very low, resulting in a stall current of 7.9A. That gives them a lot of starting torque but that torque can't be sustained without overheating.
When driving an 8414 the back-EMF measurement algorithm of ESU decoders tends to induce a lot of electrical noise at the rails due to large current spikes. This noise can send other decoders run in consist out-to-lunch, particularly when running more than ~20 feet away from a DCC booster. The distance factor is due to bus wire inductance, not resistance. ESU recommended that we install coreless motors if possible. When out-to-lunch the decoder stops responding to DCC commands. This failure has also happened with a pair of dual vertical motor Atlas F3s.
I recently procured some Swiss-made Portescap coreless motors from an auction site. These have a stall current of only 1.2A and that should permit operation with an HO decoder. They are much smaller than a Pittman yet they produce 1.7 times the torque per Amp and they are rated for a slightly higher continuous torque.
Therefore the first reason for a new motor is the hope of eliminating out-to-lunch decoders when run in consist.
Recently one of the forum members, Big Trains James, contacted me and shared his work fitting a large Tang Band 1931 speaker module inside the car body of a Red Caboose GP9. Now that caught my interest! He described milling the sides of the plastic enclosure to make it just narrow enough to fit in the RC shell.
I had already started learning Fusion 360 to make a new fuel tank that could hold a smaller TB 1925S speaker module, so my attention turned to see if there could be enough room above a smaller Portescap motor to fit a 1931 firing up and out of the dynamic brake fan.
In CAD I designed a Portescap mount that lowers the motor shaft by about 1/4 inch relative to the original Pittman. Now it appears that, as Gene Wilder exclaimed in the movie Young Frankenstein, "It might just work!"
This is a work-in-progress CAD drawing of the new mount.
(https://i.postimg.cc/K4CWKgC8/Screenshot-2024-02-27-at-7-20-58-PM.png) (https://postimg.cc/K4CWKgC8)
Here's a side-by-side comparison of the Portescap and Pittman motors. The new mount is 3D printed in ABS. Lock washers will be installed under the 4-40 screw heads.
(https://i.postimg.cc/ygkfxVPR/IMG-2263.jpg) (https://postimg.cc/ygkfxVPR)
This is certainly not the final design. I plan to add features to prevent wires from tangling in the drive train, and add a mounting platform for a small PC board to manage wires to the trucks and decoder.
The second reason for a new motor is to get hear more booming bass.
Bob
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That was quick!
I'm happy to post the speaker mod description to the forum. I can do it here or start a separate thread, which ever you think is best.
I realize that your goal is to re-motor the Red Caboose drive, and also if possible to fit the speaker in the hood. The goal is not to completely redesign the drive. But I think there is an opportunity to lower the motor more than 1/4" if other steps are also implemented. Gear towers would need to be modified, and possibly the truck blocks as well. But with access to 3d cad and printing, those things can be accomplished without too much angst.
I think there are a lot of legacy artifacts left over in the Red Caboose design, but it predated the popularity of both DCC and sound. A redesign could result in quite a few efficiencies.
Jim
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Jim -
Feel free to start another topic. I want you to get full credit for your idea of a 1931 inside the GP9 shell and have breathing room to expound on your thoughts of reworking the drive train should you desire. As you point out the RC design is quite old and harkens back to the days before DCC and sound.
Welcome back to the forums. It has been quite a while.
Bob
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I've been 3D printing more parts for the Red Caboose GP9 builds. When substituting the now unobtanium Des Plaines Hobby brass frames for the OEM plastic ones, new coupler mounting pads need to be formed. Here is a screen snapshot from Fusion 360.
(https://i.postimg.cc/t7WVhCDZ/Screenshot-2024-03-03-at-2-13-24-PM.png) (https://postimg.cc/t7WVhCDZ)
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Here are a couple photos of the 3D printed parts on the brass frame. In the first photo, one of the coupler mounting pads has been pressed over the two white coupler screw bosses. It is a nice, tight fit. It took a couple iterations to get the coupler height to match that of the OEM frame.
(https://i.postimg.cc/56kXc6K8/IMG-2265.jpg) (https://postimg.cc/56kXc6K8)
The second photo shows layout planning for the TB 1931 speaker. There is a faint pencil line on the walkway tread indicating the center of the dynamic brake fan. The speaker will be mounted close to the roof of the shell, with the round driver firing up and out the dynamic brake fan.
In a later modification of the motor mount I added a second pair of prongs that clip to the edge of the walkway. Because these were printed as an overhang, they all need light filing to proper height. What you can't see is the third fuel tank screw hole under the motor, which has been countersunk for a flathead screw. I plan to see if I can heat Cerrobend to just past melting and use it to fill the lower half of the fuel tank without warping the styrene.
(https://i.postimg.cc/6yGX3q5r/IMG-2264.jpg) (https://postimg.cc/6yGX3q5r)
As a reminder to guests, you can click your mouse on any forum photo to enlarge it. Many can be enlarged twice.
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I just couldn't help myself.
Once the GP9 motor mount was done, I turned my focus to P&D F3s. These will be receiving Tang Band T1-2025SC speakers mounted vertically. They have an unusual tripod mount and require space underneath the bottom passive radiator for the bass to get out. The extension to the two tripod mounts near the cab is a bit flimsy. A little bit of Elmer's school rubber cement will keep it from buzzing.
Here's the CAD. I left gaps on either side of the motor to allow heat to escape. That shouldn't be much of a problem since the coreless motor produces 1.7 times the torque per Amp compared to the Pittman 8414.
(https://i.postimg.cc/SXXW1QtF/Screenshot-2024-03-05-at-9-57-08-PM.png) (https://postimg.cc/SXXW1QtF)
The first installation. The 4 holes on the side bars are for mounting an HO Loksound 5 decoder and a small circuit board on a slab of styrene.
(https://i.postimg.cc/JG6xpF4X/IMG-2267.jpg) (https://postimg.cc/JG6xpF4X)
Most of the sound escapes the shell through the dynamic brake intake side grills and roof exhaust grills, along with the radiator fans.
(https://i.postimg.cc/MMzM1WR8/IMG-2268.jpg) (https://postimg.cc/MMzM1WR8)
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I gotta say….i got my Portescap replacement motor in my Overland GP35 (pitman motor died a horrible death…killing it AND my decoder). Bob and I spent many a message talking about mount schemes and noise mitigation.
Anywho….got the motor in…got the new decoder mounted…lights hooked up and speaker hooked up. The new motor work like a DREAM. At speed step 1… I estimate that the engine went 1/2” in 10 seconds. And smoooooooooth to boot!
Can’t wait to get it to the mother ship and try it out.
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Glad to hear that, Craig! It is very encouraging for the Portescap remotors. Did you tune any motor parameters in the decoder or just run with the defaults?
And kudos for spending a few hours to show me around Fusion 360. That helped a LOT. I still find myself staring at the screen with a dumb look on my face thinking "there should be an easy way to do this..." It is a steep learning curve, and my designs are neither elegant nor optimal, but at least they are functional.
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Looks great Craig. The mothership will welcome #405 with open arms.
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Another 3D part, this one simplifies wiring the lighting LEDs. It offers places to glue the class light, number board and walkway LEDs. This work can be done on the work bench instead of trying to set stuff in place inside the shell. The headlight LEDs will be 3mm warm white units and mount to the headlight fixture.
The first prototype part, though needing some refinement, fit snugly in the V of the RC GP9 shell and will be easy to glue in place. Just in case, the first parts may be glued using Elmer's school rubber cement, which would make them removable
(https://i.postimg.cc/4H70RWtN/Screenshot-2024-03-10-at-2-16-28-PM.png) (https://postimg.cc/4H70RWtN)
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Back to the original topic: remotor, and including some benefits.
The effort to install a new, smaller motor in my RC GP9s comes with a benefit to increase headroom inside the shell. This afternoon I milled a TB1935 module to make it narrower, only 1.3." I narrowed it as far as I felt comfortable while holding it in a Sherline vise. It now slips easily in a new RC GP9 shell. So far so good. There are a couple of pinhole leaks in the enclosure, due to voids during injection molding, but not enough to significantly influence bass response. It does, however, now equalize changes in barometric pressure.
Soon a difficulty became apparent. The dynamic brake blister is narrower inside than the shell itself. Rut roh!
Plan A: The DB part has not been assembled, so there are two slots for the exhaust stacks that could be used to hold it in a fixture for milling. That wouldn't be too difficult but the result would be a part that loses the alignment "lip" and reduces the amount of gluing surface. A strong joint is desired because most operators will pick up the finished locomotive by the DB blisters when re-raining after an "oopsie." Stuff happens.
Plan B: After careful measurement I discovered that I had about 0.2" of clearance between the bottom of the speaker and the top of the new motor mount. Originally I planned to center the driver in the DB fan opening, with the passive radiator situated towards the back of the long hood. That wouldn't work since it would interfere with the rear drive tower. However, it can be flipped around 180 and still leave some room for wires.
Either way, I still plan for the primary weight to be Cerrobend poured into the bottom of the OEM fuel tank maybe with the fuel tank taped to the bottom of a pot filled with cold water. The new brass frame also helps.
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Bob,
I'm curious why you are intent on using Cerrobend for the weight. I've got a similar situation with the fuel tank for my switcher, and I'm planning on filling it with lead shot set with epoxy. I suppose the space between the round balls will add up to some incremental weight, but I can't see it being enough to make a difference.
If you want the weight to be removable in the future, could you spray the fuel tank with mold release before filling with the lead shot and epoxy? You could then theoretically have a weight that is fitted perfectly to the tank, but is not bonded to it directly.
I never thought about the dynamic brake blister when figuring the size for milling the speaker enclosure. :o ::) However, to be fair I had always intended to develop a different drive that was much lower profile than the stock version, so I would have room for the speaker anywhere inside the long hood as long as the width worked.
The insert to hold the various lights in hood end is a great example of what 3d cad and printing can do for us. Yes, you could build the equivalent from styrene sheet or other material, but the 3d printed version is probably a much easier solution, yielding better results. And there's no contest short of resin casting when it comes to repeatability if you need multiples. It's a great tool for so many applications.
Jim
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Jim -
Why Cerrobend? Actually, lead shot randomly packed is only 77% as heavy as cast Cerrobend (Wood's metal). The space between round balls must be factored in, although it would be partially filled with epoxy or other less-dense glue.
According to Wikipedia, a random packing of loose balls in a cavity only fills about 63.5% of the volume. The density of lead is greater than Cerrobend, 11.34 g/cm^3 vs 9.4 g/cm^3, but the advantage is lost due to the low packing density.
Grades on the A&O are steep, and we need all the tractive effort we can get.
As for the DB interference, I'm leaning towards making a fixture and milling it out so that the full height above the motor mount is available for electronics. There's a big winter storm heading my way and that might be a good snow day project.
So far I've found FDM 3D printing to be liberating. It lets me imagine new answers to problems that would have been tedious if built-up in styrene or machined on the mill. So far the primary limiters are my imagination and NOOB learning curve with Fusion 360.
The light package mounting block is a variation of an idea I had decades ago for the long hood of an Overland GP30 or 35 (don't remember which.) Back then I got a block of Sculpey modeling clay and packed it in the end of the shell. Then I carved out openings for the various LEDs (all hand-colored blue meanies) and incandescent headlights, also enlarging holes for the various grab irons that poked inside. After sculpting the block was hardened by baking in the kitchen oven.
With the printed blocks I will have to carefully trim the length of brass grab irons so that they don't extend past the inside wall of the shell.
I'm substituting brass detail parts including the handrails, grabs and lift rings since those are delicate and easily broken (the plastic lift rings are far undersize.) The A&O is all about operating sessions, so some innocent but ham-fisted handling of equipment must be anticipated.
All the best,
Bob
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Sometimes when you have a hammer, every problem looks like a nail.
The alternative of milling the inside of the dynamic brake blister seems the most attractive. This morning I designed and printed a fixture to firmly hold the blister upside-down in the Sherline mill. Work holding is accomplished by a pair of 4-40 screws that pass through the oval cutouts for the exhaust stacks.
(https://i.postimg.cc/F7mVM7dk/Screenshot-2024-03-16-at-3-07-09-PM.png) (https://postimg.cc/F7mVM7dk)
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A Red Caboose GP9 dynamic brake got hammered this afternoon. The printed fixture worked fine, although clamping in the vise needed to be gentle because printed ABS is not as rigid as aluminum.
Curiously, the styrene objected to conventional milling, but was fine with climb milling. It required light cuts and there was considerable spring back.
Here it is fresh off the mill, still in the fixture.
(https://i.postimg.cc/t107Ym01/IMG-2278.jpg) (https://postimg.cc/t107Ym01)
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Getting back to motors, we just saw proof of the quality of a Portescap coreless motor on the A&O. Craig's Overland GP35 died with a shorted Pittman 8313 motor, which also destroyed the V4L decoder. Over the past few weeks Craig installed an eBay Portescap in his unit using 3D printed parts he designed and shaft couplers I turned on the lathe. He also plugged a new 5L DCC decoder into the carrier board.
Yesterday Craig ran it on the A&O, both light and with a 14 car train upgrade and downgrade. With default ESU 5L motor parameters it ran perfectly smoothly, better than any other locomotive on the A&O. The minimum speed was so slow it was almost impossible to tell it was moving. We opted to program an increase in the minimum speed because it was impractically slow.
Operation was nearly silent, with only a faint hum from back-EMF sampling. Curiously all this was with the default BEMF motor parameters that came in the sound file. We only changed CVs 2, 5 and 6.
The engine should run a lot cooler. The new motor produces 1.8 times more torque per Ampere than the Pittman 8x13. The stall current is only 1.2 A, so it can be used with an ESU HO decoder.
Everybody agreed that this was a roaringly successful transplant.
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As Bob stated..”Many smiles were had!” Hehehehe
The new motor exceeded my wildest expectations I have to say. The normal operating speed may throw folks for a loop for a while…but the engine is just an amazing puller! And hardly any motor whine.
Even more sad though…I didn’t record anything going UP grade…just down.
DOH! :)
Looking forward to seeing what the operators think next weekend!
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Craig -
When you are not dispatching on Saturday and your brother Mark sits on the "throne" you deserve a chance to run your GP35 on the head of a manifest train.
Here's a comparison between the Pittman 8x14 (Weaver, P&D), 8x13 (Overland) and Portescap. If you click on the chart and it looks funny, click again. PostImage is throwing a hissy fit when initially enlarging the JPG image.
(https://i.postimg.cc/gLvx4kNC/Pittman-comparison.jpg) (https://postimg.cc/gLvx4kNC)
Back to 3D CAD, Big Train James suggested trimming the inside of the Red Caboose walkways so that the speaker can be inserted from the bottom. That would permit the dynamic brake blister to be glued in place. So here's a fixture to hold the walkway assembly in the mill for trimming.
(https://i.postimg.cc/YLpvnBZj/Screenshot-2024-03-23-at-4-09-11-PM.png) (https://postimg.cc/YLpvnBZj)
The 3D print came out great and fits like a glove. Overhangs on the bottoms of the two channels are not beautiful (it was printed upside-down) but that doesn't matter. The two holes are for bolting down flat aluminum strap clamps to hold the walkway firmly against the top of the fixture.
The white hazy deposit on the center of the fixture is stick glue that was applied to the QIDI textured build plate. It can be washed off with soapy water if desired.
(https://i.postimg.cc/bGsHgkb4/IMG-2285.jpg) (https://postimg.cc/bGsHgkb4)
Next I need to design the 2-piece speaker mounting clips. Why all this effort? With a bunch of models to build, time spent now should make the assembly line run a lot faster. That's my story and I'm sticking to it.
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Sometimes 3D printing can be cheaper than subtractive machining alternatives. The fixture in my last post cost about $1 in filament. I priced various plastics and aluminum stock from which the fixture could be milled, and always came up with about $30 in raw material. Of course I have to do a lot more printing to amortize the cost of the printer itself.
Using DesPlaines brass frames means losing some of the under frame details present in the OEM plastic frame. Those details were not accurate, but they are very hard to see. To help fill the void I printed some half-frame details since a nearly 12" long part exceeds my printer's build volume.
(https://i.postimg.cc/Z9MVm5DM/Screenshot-2024-03-25-at-7-44-27-PM.png) (https://postimg.cc/Z9MVm5DM)
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Hey Bob!
I'm pretty excited about Craig's success with the smaller motor. Do we have a full part number for the motor. I've been digging through Portescap's website and catalogue but haven't found the exact motor. It seems the 216E number is a suffix to the part number, but I haven't figured out what it indicates. By matching the specifications you tabled, I might be able to figure it out, but I still have several hundred more individual spec sheets to compare! Is Craig's example a single ended shaft, or double?
3D printing is definitely changing the landscape of model building!
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Rick -
The motor is a custom unit, military surplus. 216E specifies a 12 Volt 10 Ohm winding. It has a double shaft, but curiously one end is 3mm and the other end 2mm diameter. Mounting screws are normally metric but this one was tapped 4-40.
At the moment the listing has disappeared from eBay. The seller was Elimia Industrial. They sold for $37 each in single quantity. I found a stock motor from an industrial supply house in England, but the price was about $200 USD.
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Rick -
I procured the FDM printer to make structural parts, primarily inside models, but also for custom fixturing for my Sherline mill and lathe. Most of my prints are extruded in ABS.
The GP9 under-frame detail rails are hard to see, so I won't try to hide layer lines and printing artifacts. For the most part they just fill a visible gap between the trucks and the frame that may be observed as the locomotives cross over the Ohio River bridge.
As I grow in my Fusion CAD skills, I wonder if a resin printer might be in my future...
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With the printed blocks I will have to carefully trim the length of brass grab irons so that they don't extend past the inside wall of the shell.
I've just been re-reading this thread. Could you not leave some voids in the light blocks to account for grab iron penetration? You could do blind holes, or full depth, and you could do holes for each leg of each grab, or a slot per grab that accounted for both legs. Some precision would be prudent for the top two grabs near the numberboard and class light openings, but the rest could be generously sized to allow plenty of room for penetrating wire and glue blob.
Jim
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That can be done for some grabs and other brass fittings, but not all. The top two end grabs have to be trimmed. There is very little plastic thickness between the cutout for the headlight LEDs and the number board cavity. Light leaks must be avoided.
On the roof some of the lift rings are not critical but others may need to be flush to avoid tearing the speaker during insertion and removal. By the way, the kit plastic lift rings (and some brass ones we received from Bill McClung) are undersize. Attached is a photo of a GP7 being cut up in Loveland. The P&D brass parts (now out of stock) are the correct size, but can be difficult to cut.
(https://i.postimg.cc/w1mN1gRf/WW1-U5405-XL.jpg) (https://postimg.cc/w1mN1gRf)
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Hi Bob,
I have another pair of questions regarding the re-motor project. I hope I don't tire you out tugging on your sleeve all the time. ;D
I notice in your motor comparison matrix that the Portescap motor has a significantly lower no-load speed than either Pittman option. Presuming that gear reduction remains the same without regard to choice of motor, does the lower top end speed present any issues for you? I recognize that we seldom run our models as fast as they could go, so I suspect it's not a problem.
In a different context, where reduction is not predetermined, the no-load or rated speeds do affect a final gear ratio, which in turn affects torque. It's been a bit of a balancing act as I seek a suitable motor for my switcher project. It seems that many of the better quality motors have substantially lower no-load speeds compared to the Pittmans.
The second question is in regard to the use of an HO decoder, in particular one of the ESU Loksound variety. Do the HO decoders have enough power to successfully feed the Tang Band modules? Or to power a TB module and a smaller driver for the bell and horn, as I believe they have two speaker outputs. Also, the large format Loksound decoders have onboard keep-alives now. Are they integral or separate on the HO versions. It would be nice to use an HO decoder for space and cost, although some of that may be offset if a separate keep-alive is required.
Jim
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Coincidentally, I just measured EMD lift rings while at the Illinois Railway Museum during the Chicago meet. The ones I measured were on an sd40-2, but they appear to be the same as the one in your photo. I'm planning on having some brass castings done within the next month or two. I'll share results when I have them.
Jim
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Jim -
I'm glad you are participating on this thread! You have helped me break out of some mental blocks and arrive at better solutions, for which I am appreciative.
I'm in no way concerned about insufficient top speed with the Portescap motor. In fact I still plan to change the P&D 15:1 reduction to 25:1 reduction. That should multipliy the motor torque by about 1.6, although I do not anticipate lack of torque to be an issue. It will, however, reduce the average motor current.
The A&O isn't a racetrack display layout. It is for guys who like to operate. Although it is in a huge basement, running fast on the mainline and getting to the next "town" in a matter of seconds doesn't satisfy and would be an undue stress on the dispatcher. Most trains do switching, and for that smooth low-speed control is preferable.
What top speed is appropriate for your models depends on how you want to run them. The Reading ran a lot of SW "pups" in mainline coal hauling. On the other hand, GCOR limits the top yard speed to 10 MPH, although many modelers run faster than that, seemingly trying to pop a wheelie when accelerating from a stop. When when stopping, they stop on a dime, which sometimes may unfortunately be in the brakeman's pocket.
I anticipate that the larger HO decoders, such as the 58240, should be able to handle the motor current. The thinner height opens a lot of possibilities.
I also don't expect the less powerful amplifier in an HO decoder to be an issue. Our ears respond to increases in SPL in a logarithmic fashion, so a 3W amp isn't 3X as loud as a 1W amp.
The keep-alive is a consideration. ESU sells good 3-wire PowerPacks. The small one has a single 1 Farad capacitor. The 5L decoder has two 1 Farad capacitors. The large PowerPack has two 5 Farad capacitors. But sometimes the longest run time isn't the best. How much trouble can a derailed locomotive get into in only 4 seconds? Can it meet our nemesis gravity?
As for lift rings, glad to hear your SD40-2 measurement matches. Also note that the cast base or washer of the lift ring is of a large diameter. For a while I was concerned that the P&D lift rings were about 30 thou in diameter, but that's about not oversize. If anything it is undersize.
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One thing I've been obsessing over is how to improve and illuminate the Red Caboose GP9 number boards. The OEM polycarbonate inserts are nearly impossible to install and they are far thicker than the shell. They can stick out on both the inside and outside of the shell cutout. That's light leak city. Harrumpf.
One thought was to mill a brass cutting template for a thin clear styrene number board, but that would be likely to leak light around imprecisely cut edges and raised the problem of how to mount it in the shell.
I decided to just go for it and clamped an OEM insert in the Sherline mill. Two parallels and a spacer raised it up in the vise with just the thinnest bit of the edge clamped. Too much grip on the vise could crack the part, but too little might let it fly out and be ruined.
Fortunately, with light 10 thou passes I was able to thin the boards without dislodging them and to a final dimension less than the thickness of the shell. A sharp Niagara end milll wider than the board left a super smooth but nice frosty finish, perfect for diffusing light.
(https://i.postimg.cc/YhgBqKHP/IMG-2349.jpg) (https://postimg.cc/YhgBqKHP)
A couple swipes with a fine file on the outer sharp bevel edge added a very slight bevel that made pressing the insert in place simply and easy to adjust. I think I will install the flat milled side to the outside and sand the inside to be a secondary diffuser.
One thing I noticed is that since plastic shrinks when it cools from a liquid, the centers of the number board castings were not flat but slumped a bit. That suggests that both sides should receive a cut to make sure they are flat.
The lighting block for each end has also been refined a bit. There is a rabbet around the number board LED cavities for installation of a thin 0.010 styrene tertiary light diffuser. Also there is now a tab on the top for a small PCB board to aggregate the various LED wires to a single 5 wire harness going to the decoder. The PCB will be underhung to the tab with double stick tape. The wires are planned to be 30 AWG solid kynar wire wrap wire, which can hold its shape once formed, to a 2.5mm pitch JST XH connector.
(https://i.postimg.cc/LYtxh1RY/Screenshot-2024-05-21-at-12-51-37-PM.png) (https://postimg.cc/LYtxh1RY)
A random thought: At least on some later EMD GPs, each number board had 3 incandescent lamps inside. Particularly on B&O engines I saw as a child, the number boards were translucent and one could see the hot spots of each bulb. What if I drilled 3 shallow holes on the inside of the inserts? Could that effect be effectively emulated?
Thoughts?
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I did a video on 3D printing weight molds for my shay locomotives. I print the molds in PLA, place them in a container of ice water, then pour in the cerrobend metal, then cut away the mold. what I did not show in the video is that I actually pour in a small amount of cerrobend and then drop in lead pieces, then fill in more cerrobend to fill in all the gaps. This lessens the amount of cerrobend I need and I think makes the weight even heavier.
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Great idea to drop lead chunks in the cerrobend. Thanks for the tip, Jeff.
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It has been quite a while since I reported any progress. This is a dry fit of the 3D printed parts and milled Tang Band 1931 speaker inside the shell of a GP9.
(https://i.postimg.cc/hXRmNjXH/IMG-2520.jpg) (https://postimg.cc/hXRmNjXH)
At the far right is a redesigned mounting block for LEDs. This one has a flat back so that a custom PC board can be attached that holds all the surface mount LEDs in alignment. Resistors will be soldered to the bottom layer of the board along with a pair of small JST connectors.
In the middle we see the bottom of the Tang Band speaker. It is held in place with a clip on the right and with two screws that attach a lower clamp. Milling the walkways to be flush with the inside edge of the shell should permit removing the speaker after assembly.
On the left are 4 screws and mounting studs for another PC board. The decoder and PowerPack will be soldered to the top side, with a pair of JST lighting connectors on the bottom. Also on the bottom will be a 4 wire cable and an Adafruit magnetic connector carrying track power and motor wires.
All this is possible thanks to the efficient and tiny Portescap motor.
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After assembling one of the lighting blocks I quickly realized that having so many loose wires coming out of the back was not going to be fun to solder to a small prototyping "relay" board on which the dropping resistors were mounted. For one locomotive that might be OK. But I have a bunch of GP9s to build and David has a small fleet. Hmm... back to the drawing board?
(https://i.postimg.cc/dh799kTd/IMG-2567.jpg) (https://postimg.cc/dh799kTd)
(https://i.postimg.cc/r0TCcfZC/IMG-2568.jpg) (https://postimg.cc/r0TCcfZC)
While feeling frustrated I saw a post by Mike DeBerg on O Gauge Railroading showing the interior of his new 2 Rail SD40-2 from Sunset. That was the cleanest DCC install I've seen.
https://ogrforum.com/topic/sunset-models-3rd-rail-sd40-2-an-inside-look
Sunset designed a new daughter board for the ESU 5L decoder. That custom board uses a bunch of JST XH connectors for wire management. A real incandescent light bulb turned on in my head... Why not have some custom PC boards made that could attach to the back of a lighting block?
From US vendors prototype quantities of PC boards can be quite expensive. Many 3D printing channels on Youtube are sponsored by a Chinese company out of Hong Kong, JLC PCB. I uploaded Gerber files from KiCad and got a quote for only $2 for 30 boards, including a $6 new customer discount. Including shipping the cost per board was less than $1.
I downloaded the current (and free!) KiCad software for schematic capture and PC board layout. It did not take long to arrive at a PC board design. That said, soldering the LEDs to the board would require reflow soldering, something I've never done at home.
(https://i.postimg.cc/62VcGk4m/Screenshot-2024-10-27-at-11-42-47-AM.png) (https://postimg.cc/62VcGk4m)
The lighting block was also modified to have open apertures for PC mounted LEDs. The two central mounting holes are sized for M2 threaded inserts.
(https://i.postimg.cc/z3501G9Z/Screenshot-2024-09-11-at-12-32-38-PM.png) (https://postimg.cc/z3501G9Z)
Soldering tiny wires to the back of many surface mounted LEDs is not all that difficult. But how can one solder the LED to a PC board when the contacts are hidden on the bottom of the package? That requires reflow soldering, in which a paste of solder and flux is applied to the PC board pads and the LEDs are set into the paste. Then the entire assembly either goes into a reflow oven (at a commercial facility) or at home on top of an inexpensive digitally controlled hot plate.
I bought a cheap digital hot plate from Amazon and in an afternoon reflow soldered 5 LEDs to each of the 30 prototype boards.
Here are a sample of the results. On the left, one of the reflow boards with 5 SMT LEDs. Center, a modified lighting block with clear apertures for LEDs mounted to the PC board. Right, the back of the PC board with a pair of JST connectors. The upper one connects back to the decoder board. The lower connector powers ground (truck) lights, if used.
(https://i.postimg.cc/zVYLQyMK/IMG-2566.jpg) (https://postimg.cc/zVYLQyMK)