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Commander Wolf

[MOC] Canadian National X-10-a with Power Functions and 9v

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Well, it's been more than a year since I started work on my last locomotive MOC, the China Railways QJ. Having built most of the practical engines (not too big for R40 curves) that I was visually interested in, I had to wait a bit before my interest was piqued again on the locomotive front. 

My inspiration came from running the QJ at most BayLUG meetings for the past year and change. The QJ isn't necessarily unreliable or difficult to set up, but it's still not very convenient: the model isn't that easy to move around or manipulate due to the size, the tender, and the number of fragile bits. The lengthy drivetrain with its fair amount of friction and torque also prevents the engine from generating smooth low-end torque. Finally, BayLUG still runs 9v at most of our shows, and the QJ can't easily be converted to run on 9v.

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So this is really my second locomotive to be born of functional requirements (the first was my U30B):

1. It should be easy to transport [from here to there] and move around [a layout]
2. It should be designed with robustness as a key feature
3. It should be easily convertible between PF and 9v operation
3b. The PF components should be easily removable (also helps with charging)
3a. It should run smoothly when pushed [by a 9v power car]

Requirements 1 and 3 really insist that this engine be a large tank engine: for 1 I don't need to deal with a tender when transporting or moving and for 3 it needs to be big enough to fit all of the PF stuff. It actually took me quite a bit of time to zero in on the X-10-a as large tank engines are apparently pretty rare in the US and North America: it seems that even most of our branch line and shunting steam engines were tendered. 

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But eventually I found a drawing and the work began!

What I learned from the QJ is that if the weight of the loco is properly distributed, one powered (and tyred) axle is good enough to generate usable torque. From this notion I designed the chassis to have exactly that one powered axle, which I could easily remove to remove tyres and gearing for 9v operation. For the same reason, the driven axle isn't cranked either; in the QJ I would have had to remove all of the cranks and all of the wheels to access the tyres or gears. 

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The lack of cranks on the driven axle also lets me keep the chassis articulated, which should help minimize rolling resistance for 9v operation (say compared to a 6-coupled flange-blind-flange configuration for the drivers). The drive rods are made using the half-pin in rod-track technique, and there's a bit of a hack: the connecting rods have to go around a corner due to the articulation, so the travel is longer than the usual three studs, and the connecting rods are both loosely pinned down and made of flex. As far as I can tell this arrangement doesn't add significant friction, probably because the corner is very small.

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The engine is designed to be powered with two M-motors, but I'm using the E-motor right now for the novelty. Unfortunately it wasn't quite possible to get as much weight as I would have liked over the driven axle: the battery box must go behind the boiler due to its height, and that really limits weight distribution options. The loose 9v motor in the front is simulating the weight of a second M-motor, and it helps bring the net weight over the driven axle to maybe 60 percent?

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Here you can also see how all the bits come out of the engine: almost all of the top surfaces are detachable. Whether this is convenient enough to fulfill requirement 3 remains to be seen. 

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Construction of the body is actually very similar to that of the QJ: structural integrity is mainly provided by studs-out beams and everything else is studs up. Stickers are created at 300DPI and printed on 3M 3200-L mailing label material. 

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This is a small detail, but it is actually one of my favorite parts, inspired by and stolen from 60052:

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And finally a video showing the locomotive running. The first 70 seconds is PF running and the last 20 seconds is 9v running. For PF running I'm using the AAA battery box with AAA Eneloops and the aforementioned E-motor. The E-motor is actually pretty neat: it has a wider dynamic range than the other PF motors and it is quite quiet as well. Sadly it is a little bit underpowered as well; I'm geared down 3:5 and you can still see it struggle a little in the corners during the PF segment. 

The 9v segment is a bit hazy, but we ran out of sunlight because DST. The engine is actually smoother than I would have guessed in the unpowered configuration: you can see how it basically doesn't lose *any* speed in the turns, and the regulator is only turned up to notch 3. 

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Alright, I think that's all the commentary I have on this. There is as usual a full gallery if it ever gets moderated. There's a bunch of build and reference pics there that I didn't show.

Have a nice day.

Edited by Commander Wolf

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What a lovely locomotive! I am still wrapping my head around how unique the rear is compared to other steam locomotives. However, I think the E-Motor is woefully underpowered for this type of application. I think you can probably squeeze an L motor in by using one of these and two 16 tooth bevel gears. Although you would loose some rpm, your torque would be almost five times greater.  

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Wow. Nicely done. I like seeing CN steam. Number 49 is on my to-do list someday. The articulation you've employed is really impressive.

The only thing I'd change is the Elesco feedwater heater on the smokebox right in front of the smokestack. It's a signature feature of most CN locomotives. I have a technique I use on my CN Mikado and Pacific you might like. Cale has a different one that works well on his CNJ Suburban that's very similar to the X-10-a.

Any plans for a rake of CN commuter coaches to go with it?

 

Edited by greenmtvince

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Always great to see a large tank engine! Very well done! :thumbup:
I agree with greenmtvince that you should try to give the feedwater heater a more rounded shape, though.
But that modular design is very clever!
The only thing I don't really understand: Why do you need to convert between PF and 9V configuration? I always thought it was possible to run PF trains on 9V track?
 

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14 hours ago, greenmtvince said:

I have a technique I use on my CN Mikado and Pacific you might like. Cale has a different one that works well on his CNJ Suburban that's very similar to the X-10-a.

Any link to these? There's actually supposed to be another greeble on the feedwater heater to make it look rounder, but it requires the "backpack bracket" in black, which I wasn't able to get at the time. Totally forgot about it 'til now though, but would still like to see other options. These sorts of things are annoying because there still really isn't a good 1.5 stud round element.

8 hours ago, Tenderlok said:

The only thing I don't really understand: Why do you need to convert between PF and 9V configuration? I always thought it was possible to run PF trains on 9V track?

It's not a matter of track compatibility, just a matter of how our club runs trains. In general PF is a more convenient power solution than 9v, but during multi-day club displays people so far haven't shown that much inclination to run PF trains, so I would like the ability to run 9v. In practice it means that it needs to be pushed by an external power car and as such you want it to have as little rolling resistance as possible because the 9v motors don't have much torque at low speeds. 

Regarding the PF motor choice: the E-motor is indeed very fast when the loco is running light, but it's likewise very under powered if you are pulling anything of substance. Whether I do change to double Ms or something else probably depends on how much I end up regularly pulling with the thing, so TBD.

Edited by Commander Wolf
typo

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16 minutes ago, Commander Wolf said:

 These sorts of things are annoying because there still really isn't a good 1.5 stud round element.

Sometimes I use the saucepans for that purpose, e.g. for my steam engines' air compressor pumps. It's not always easy to connect them properly to other parts, though.

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7 hours ago, Commander Wolf said:

Any link to these? There's actually supposed to be another greeble on the feedwater heater to make it look rounder, but it requires the "backpack bracket" in black, which I wasn't able to get at the time. Totally forgot about it 'til now though, but would still like to see other options. These sorts of things are annoying because there still really isn't a good 1.5 stud round element.

Here's a Bluerender of my Mikado that probably shows it best. Some other shots including the finished model including my Pacific are in this album.  I opted to round up to 2 studs since it's a prominent feature and a good 1.5 stud option was nearly impossible.  Cale opted to go down to 1 stud for his Suburban

If you decide to do matching coaches as they were used in service in and around Montreal, I have the printed bricks

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Great train!

Overal I think it is a great piece of work. One always has to compromisse working with scale models and you did a great job! (I didn't really notice the not round feedwater heater at first and had to look twice after the comments)

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