aj_bricks

MOC - KiwiRail DXC Locomotive (1:48 Scale)

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This is my newest locomotive, and my first attempt at building in 1:48 scale. KiwiRail DXC locomotive from New Zealand. Measuring 44 studs long and 7 studs wide, it can handle standard Lego R40 curves and is powered by 2 PF L motors (one on each truck) controlled by an SBrick. The custom stickers were made by OKBrickworks and I think they turned out perfectly!

DXC class locomotives originally started as General Electric U26Cs, built in the 1970s. Similar engines were also produced for Brazil, Kenya, South Africa, Tanzania, and Zambia. DXC locomotives are used by KiwiRail on the South Island of New Zealand to haul heavy freight and the famous TranzAlpine excursion train (considered by many to be among the world's most scenic train rides). They differ from other DX variants in the addition of "chutes", special air intakes that are needed for better air flow in the 5+ mile-long Otira tunnel under the Southern Alps. Prior to the DXC upgrade the tunnel stretch had to be electrified.

I'm not from New Zealand, but I was inspired to build this loco after I had the opportunity to spend a few weeks there in March 2019. It's a beautiful country with some amazing scenery to see by road or by rail. If you haven't been, you should go!

Previously, the only custom train builds had been in 6-wide and were based on the old 9v trucks and motors. So this was a big change for me. I had never used PF motors before, never had done much with technic even, so building the trucks and drivetrain took the most time for me. I started by looking at blueprints of DX locomotives online and dragging a scaled version over a Lego graph paper template in MS Publisher to get a 1:48 scale view. (http://studs.sariel.pl/ was really helpful for this as well!) I then did most of the build in Stud.IO, building a couple test trucks along the way to test out the length on R40 curves (which are all I have right now). After ordering parts I still made plenty of tweaks as I built - probably 25% of the loco is different in some way from the digital model I built. I realized I should have 2 L motors for traction, but I haven't ordered the second one. There's just enough room for the 2nd motor with an SBrick and a 9V battery (maybe 2 - space is tight!). 

Edited-5724Edited-5731Edited-5732Edited-5721

 

 

 

Edited by aj_bricks
Failed at adding flickr pictures.

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On 1/12/2020 at 4:59 PM, aj_bricks said:

Previously, the only custom train builds had been in 6-wide and were based on the old 9v trucks and motors. So this was a big change for me.

I refuse to believe that given the fantastic build (grin), seriously though, it looks like a fantastic build

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On 1/14/2020 at 12:04 AM, zephyr1934 said:

I refuse to believe that given the fantastic build (grin), seriously though, it looks like a fantastic build

Haha, thank you! That means a lot, especially coming from someone like yourself!

Thanks to all for the comments, I apologize for the delay in adding more details here. I've been busy and had time to do more work and testing on the loco until recently. 

As this is my first time working with power functions motors, batteries, and the like, I seriously underestimated the difficulty in fitting everything inside the 5-wide main body. Wires can take up a lot of space!

I budgeted space for 1 9V battery, 1 SBrick, and 2 PF L motors. I had seen the 9V battery-to-PF adapters offered by BrickTrainDepot, and figured I could make my own. I hadn't soldered in 4+ years, so it wasn't pretty, but it's functional so it works for me. I already had an arduino 9V power supply with a 2.1mm plug, so I acquired another 2.1mm socket and attached the PF plug to that. This gives me an extra way to disconnect the SBrick without having to fiddle with the battery connection itself.

20200119_16002120200119_172959

Once all the wiring was in the loco I realized I would have to compromise something to make room - so I knocked out the back wall of the cab and used that space for the PF connections. (Note: I think it's great that you can power the SBrick from any of the connections, top or bottom, because in my case using the bottom plug would make it too big to fit. For this reason I also had to connect both motors to the same SBrick port using a jumper cable.)

20200123_19555220200123_200841

 

I then ran it on my small temporary test track, since I don't have a permanent layout right now. The results were mixed - I was relieved to finally have it running as expected with all the electronics inside and pulling cars, but the 1:1 gear ratio makes for a slow drive (no surprise there) and the trucks seemed to get bogged down on the R40 curves more than I expected. Before building I had tested the truck configuration using 6 regular trainsets at the same spacing, but that didn't seem to have the same issue. I plan to do further tinkering for both - some small changes to the middle axle of each truck and the addition of 20-tooth gears to change the gear ratio. Below is the video of the test.

https://flic.kr/p/2inWSxg

 

 

 

Edited by aj_bricks

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Can a 9v battery deliver enough power for two L motors? (that is a serious question, I'm not trying to be a rhetorical goofball)

Also, are your 3 axle trucks rigid? If so, that would certainly cause binding in the curves, but your engine doesn't seem to slow down much in the curves... but that might just be the fact that it doesn't go too fast in the straights either. If you are doing a rigid truck I've had luck replacing the bands on the 1st and 3rd axle with thicker o-rings, that seems to lift the middle pair of wheels (with no bands) off the track enough that the middle axle does not cause problems in the curves.

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What zephyr said. I used shupp's truck design for my E7's. Using normal #35 O-rings on the other wheels and omitting o-rings on the middle wheel in each truck allows for good R40 maneuverability. 1:1 is definitely slow!

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On 2/2/2020 at 9:09 PM, zephyr1934 said:

Can a 9v battery deliver enough power for two L motors? (that is a serious question, I'm not trying to be a rhetorical goofball)

The answer to this is no. A dual L-motor setup like this can easily pull close to 1000mA which will chomp thru a 9V battery quickly. 

@aj_bricks

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Lovely! Great details. Fascinated to discover that the originals are meter-gauge locos.

I, too, wonder how this performs on a 9V alkaline battery. What kind of run-time do you get, as is? I would think that a generic 6-AAA holder (like this) would probably just squeeze into where the 9V battery sits and give you 750mAh of rechargeable capacity (9V batteries are nominally 200 mAh).

Edited by izx

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Yes, a 9v battery will deliver enough power for 2L motors. But as @supertruper1988 and @izx pointed out, it won't last as long as what you would be used to with a standard Lego battery box. That being said, I ran it for about 15 minutes or so during the above test with no noticeable drop in performance. I used a duracell 9v that runs about 300mah. And more powerful 9v batteries are out there, like this set of 800mah rechargeables: 9v Lithium Batteries, Li-ion Rechargeable 800mAh 3 Packs with Quick Charger https://www.amazon.com/dp/B07BT4D99D/ref=cm_sw_r_cp_apa_i_UkwoEbBA9HA5M. I plan to use those if I ever take this to a show, though I might try the battery box izx mentioned if the dimensions check out. I'll run a longer test next time to see how much more the duracell has left (I'm guessing not much).

As for the trucks, thanks @zephyr1934 and @jrathfon for the suggestions. I wondered about removing the rubber o-ring on the non-powered middle axles or even just replacing them with standard Lego metal axles, thinking the extra room in the technic hole might allow the axle to float up high enough to limit resistance.

Once I get the parts for the change in gearing I'll test these other changes too.

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41 minutes ago, aj_bricks said:

And more powerful 9v batteries are out there, like this set of 800mah rechargeables: 9v Lithium Batteries, Li-ion Rechargeable 800mAh 3 Packs with Quick Charger https://www.amazon.com/dp/B07BT4D99D/ref=cm_sw_r_cp_apa_i_UkwoEbBA9HA5M

True, those are a decent option. Beware that their true usable capacity is usually closer to 550-600 mAh (review of similar batteries by a very well-known reviewer in the flashlight world).

I'm thinking the ultimate power source, if you can fit it, would be one of these holders with 2x 18650 Li-ion batteries. High-quality Panasonic/Sanyo 18650s rated at 3500 mAh are $5 a pop and would last you for hours. All you need is 75mm of length to make sure the  holder fits.

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1 hour ago, izx said:

True, those are a decent option. Beware that their true usable capacity is usually closer to 550-600 mAh (review of similar batteries by a very well-known reviewer in the flashlight world).

I'm thinking the ultimate power source, if you can fit it, would be one of these holders with 2x 18650 Li-ion batteries. High-quality Panasonic/Sanyo 18650s rated at 3500 mAh are $5 a pop and would last you for hours. All you need is 75mm of length to make sure the  holder fits.

According to the data sheet, those need 3 studs wide by 9 studs long and 13 plates tall. That is a decent size. I would be sure you have 10 studs of length to account for the wire connections. 

I may have to order a couple of those. Thanks for the tip!

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On 2/4/2020 at 8:09 AM, izx said:

True, those are a decent option. Beware that their true usable capacity is usually closer to 550-600 mAh (review of similar batteries by a very well-known reviewer in the flashlight world).

I'm thinking the ultimate power source, if you can fit it, would be one of these holders with 2x 18650 Li-ion batteries. High-quality Panasonic/Sanyo 18650s rated at 3500 mAh are $5 a pop and would last you for hours. All you need is 75mm of length to make sure the  holder fits.

Those look neat, I hadn't seen them before. Thanks! I don't have room for those in this design right now (thanks, @supertruper1988 for the measurements) but I'll keep it in mind for the future.

I re-worked the gearing on the drivetrain to 20:12 instead of 1:1, and man did it make a difference! I'm very happy with the speed now, and even without making changes to the middle axles (yet) there doesn't seem to be any trouble on R40 curves. I also used the rechargeable 9V batteries I mentioned earlier (https://www.amazon.com/dp/B07BT4D99D/ref=cm_sw_r_cp_apa_i_UkwoEbBA9HA5M), and I was impressed with them. The below videos show the locomotive running with and without a load of a couple container cars. I let it run at full speed pulling the cars and it was just over an hour before the battery dropped to 7V (even then there was not a noticeable drop in performance). 

https://www.flickr.com/photos/185494316@N03/49547931527/in/dateposted-public/

https://www.flickr.com/photos/185494316@N03/49547702601/in/dateposted-public/

KiwiRail DXC with Containers

 

Edited by aj_bricks

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@aj_bricks: I absolutely love the Kiwitrain you have build! I have also send you a private message on Flickr because I'm desperate to build this train myself as well. Could you be so kind to share the lego designer files with me? I'm looking forward hearing from you!

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2 hours ago, Rubenhof said:

@aj_bricks: I absolutely love the Kiwitrain you have build! I have also send you a private message on Flickr because I'm desperate to build this train myself as well. Could you be so kind to share the lego designer files with me? I'm looking forward hearing from you!

Thanks, @Rubenhof! I don't have a complete file to share, but I'm happy to offer advice if you're building your own. I'll respond to your Flickr message and we can chat.

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I am thinking about building this, but changing the body to an EF class loco, do you have a parts list or render that I could use?

 

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