jtlan

Not sure I'm understanding you correctly? Are you suggesting something like sekiyama's design here? If so, I doubt it will work with the last driver being the flanged one, as the pivot arm would be too long.

Due to the tight curve of the Lego track there's not really much of a choice when it comes to large locomotives -- overhang is inevitable. You can reduce the amount of overhang at the ends by not fixing the boiler rigidly to the drivers (so that the drivers slide under the boiler), instead fixing the body to different pivot points on the frame. However, this is much harder, and you will have to experiment with real bricks to see what arrangements work. Also, you'll probably want to switch to Big Ben Bricks XL drivers -- the current ones you're using look a bit small.

Boxcabs don't have the flowing curves or prominent angles of other locomotives, but they have their own type of charm. Re: power draw: The model puts out ~0.2W of pulling power, but it's not clear how much electrical power is being consumed along the way. While chain drives are less efficient than other transmissions (and I have some other iffy business such as axles not being as well supported as they should), I am also using the most efficient Lego 9V motor. I wonder if I can rig up some sort of current-measuring device as a follow-up to the power-testing measurements.

I ordered some new links for this project, since I didn't have any sets with chains. I borrowed some older links from a friend and they looked the same to me though. Maybe they get worn down a bit from use? Regardless, I don't find the sound to be a huge problem.

Shot some video last weekend, and finished editing it now. If you listen carefully you can hear the clicking-rumbling sound the chain makes as it drives. Some of Commander Wolf's locomotives and rolling stock can be seen as well.

Is that just two pivots? With articulation like that the car will just spin and fall off the tracks, unless there's some sort of spring force trying to force the wheels straight. Better to articulate it 2-and-1 (2-axle truck + 1-axle truck), or use a sliding center axle (might be a lot of friction with something this long though).

I like the shape of this, particularly the steps. However, this is going to have a lot of friction going around curves, due to the large separation between the axles (it actually might not go around the curves at all). For 2-axle rolling stock I've found that the axle-to-axle spacing (distance between the centers of the axles) should be no more than 10 studs to avoid extra friction.

Normally having three wheelsets side by side rigidly will cause more friction. For steam locomotives usually the center pair of wheels is "blind" (no flanges), which prevents this problem. To counter the problem, you can either use a "blind" center wheel (like this, as seen in dr_spock's post), or build a three-axle bogie with a sliding center axle, which probably requires the use of the design shown in Railbricks #6. ME models makes wider radius curves, but I don't know if they're in general production yet.

I've seen a number of designs using the curved rail, none of which I am really happy with because they all involve stressing the track. There are some brick-build solutions but they are much larger. Previous thread with stressed switch: http://www.eurobricks.com/forum/index.php?showtopic=79312 Brick-built: http://www.brickshelf.com/cgi-bin/gallery.cgi?f=537641 Another brick-built: (Space2310 has a lot of these)

I've got 5 2-axles tankers (basically the tank section from 60016), and basically just keeping an eye out for spare parts for more (also have an alternate 4-axle design that looks more 'Murrican). The axles and buffers (and bogie plates, for the longer ones) are the most expensive parts. You should build as many as you're happy with, although I'd argue that after about 5 or so repeating the same car doesn't add much visual interest. I also think there's probably not that much point to having a train longer than the longest straight section on your layout.

How come you need to transfer it to MLCad? Are there parts you're missing that aren't available in LDD?

Probably not necessary to use two motors; If Dutchiedoghnut is intending to haul at low speeds, the limiting factor is likely to be friction rather than the available torque, a problem that can be addressed by adding weight to the locomotive. If more torque is required it might actaully be easier to hide a L motor instead of two Ms.

Thanks for the comments, everyone! Commander Wolf and I shot some video over the weekend, but we haven't finished editing it yet. I'll post it once we're done. I actually really like the old gearmotors, since the studs sometimes make them easier to integrate. Their shape is inconvenient in a different way than PF M-motors, so sometimes they'll fit in places that that motor cannot (like this model). My biggest complaint (aside from the fact that the internal magnets are fragile -- don't drop them!) is that it has a short potruding shaft rather than the socket that the Power Functions motors have. I've been asked by some LUG members if I want to build one. Thus far the main blocker has been coming up with a good idea for a module. I thought about what color those should be, and they seem to have come in a variety of colors. The "squat pot" stacks, for example, may have blackened with age on some of the units; on others, they are copper-colored. The radiators are usually the same sort of grungy grey-black that train wheels usually wind up as. I eventually chose to make them grey to add some visual interest and contrast.

Somewhere between talking to CommanderWolf about boxcabs, seeing his HH1000, and reading up on old diesel-electric locomotives on the internet, I somehow got the idea to build a model of the very first production diesel-electric locomotives in the United States. These locomotives were produced by a consortium of three companies: ALCo, General Electric, and Ingersoll-Rand. Diminutive as they were (this model represents a 60-ton, 300hp locomotive), they are the direct ancestors of the diesel-electric locomotives powering the US rail system today. As far as I can tell, only three locomotives were actually built with this specific layout: CNJ #1000, B&O #1, and Lehigh Valley 100. Later models featured doors at both ends in addition to the sides; in addition, larger 100-ton versions were built. They could run in either direction, although there are distinct ends and sides: the above image shows the "B" side and "2" end (which I consider the "rear" of the locomotive). I went into construction pretty set on equipping this locomotive with Power Functions while still building an accurate model (at the same scale as the rest of my locomotives). While there are examples of very small Power-Functions-equipped locomotives, I was pretty much dead-set against using the Power Functions train motor -- the locomotive would be too fast, and I wouldn't be able to accurately model the trucks. So, I had to fit motor(s), battery box, and receiver into the shell of the locomotive: As usual, the Power Functions receiver turned out to be the biggest bugbear in this whole adventure. Its shape is extremely inconvenient. While there is just barely enough room to fit Power Functions M motors vertically inside the locomotive above the trucks, placing them would imply that the battery box would have to go between them ... leaving no room for the receiver. I was not going to accept powering only one of the trucks (for a model this light, you need all the traction you can get). The locomotive is not long enough to orient the M motors any other way, so I turned to the trusty 9V gearmotor instead. However, I determined that, even using that motor, there wasn't enough room inside the model for both two motors and the receiver. It was around this point that I decided that 7-wide was the correct width for the model, to avoid it looking too big (it also resulted in better proportions for the windows at the end of the locomotive). At 7-wide, there are only 5 studs of width inside the locomotive, of which 4 studs are taken up by the battery box. The transmission would have to either be 1 stud wide, or I would have to integrate panels into the side of the locomotive in the hopes of hiding the gearing. So what did I do? Restrictions breed creativity: (chain doesn't connect correctly due to LDD difficulties) Turns out, the entire drivetrain can be made to fit into the space available using a chain. The grey idler wheel attaches to a 1x2 brick with pin in the wall of the locomotive. Other parts of the drivetrain are similarly integrated with the body, and the motor and battery box form integral parts of the model's frame. The Power Functions receiver just barely fits in this awkward position above the gears on the non-motor end, and receives signals through a trans-black 1x2 brick on the roof: It is actually a pretty decent puller despite its small size (it is the "AGEIR" listed in this thread; the power rating has since risen to ~0.2W after I carefully lubricated and reassembled the entire drive system). Oddly for a PF-equipped locomotive, it is possible to back-drive the motor by pushing the locomotive, due to the low mechanical resistance of the 9V gearmotor. An additional side "benefit" of the drive system is that the chain makes a pleasant diesel-like clicking/rumbling sound when the locomotive is in motion. As troublesome as all these restrictions (that I placed on myself...) were, I really enjoyed figuring out how to fit all the mechanical components into such a small space, while still maintaining an accurate depiction of the prototype. It just goes to show what's possible using Power Functions. Brickshelf gallery here. If you're curious about the history of these locomotives, you can read about them here.

The point of having forum topics at all is so that things that are logically distinct are different threads... For guidelines, you'd be best off asking the convention organizers what the rules at that particular convention are. (for Brickfair, the FAQ is here.)

The PF motors use screws? That's much more convenient for maintenance...

I've never heard that about the de-fused motors. I think a lot of our LUG members have taken out the fuse, and their motors run for many hours continuously at shows. I suspect the failure point of the fuse is far below that of the motor itself, so you shouldn't have anything to worry about unless you really overstressed it (say, by jamming the wheels and running it at full power).

Looking good! I didn't notice that the walkway was already light grey in the photos. I'd probably consider adding a bit more detail to the side of the truck (where you have the 1x4 plate right now). Somehow I only just noticed that the tank itself is 8-wide. Do you have an appropriately massive locomotive to go with this?

I feel like I've never seen a model of a tank car in this color before. Quite striking. The trucks feel a little small to me. Maybe because they're more covered on the "prototype"? Try stretching them by 1 stud and see how that looks. The white walkway and black lids also feel a bit out of place. Maybe switch them to grey, and use a tile or this piece for the walkway itself instead of a plate.

That would be the 2nd-best thing; the first would be two motors, but you'd need to find someplace to hide a polarity switch if you did that. I'm surprised moving the weight back a bit helps, but I don't know the specifics of your setup. It also makes sense that having the motor as the first truck performs better.

Srbandrews, you might consider replacing the dkgrey pin at the end of the 5L liftarm with a half-pin, with the long side of the pin plugged into the liftarm and the "lip" of the pin behind the dkgrey rods. The lip will keep the liftarm from sliding outwards.

Something like this?

Picking wheel size is tricky. The flange on Lego train wheels is a significantly larger proportion of the wheel's diameter than is the case for their real-world counterparts. In addition, the range of available sizes is limited. Generally, I consider a wheel suitable for use if the scaled diameter is between the hub and flange diameters of the model wheel. Alternatively, you can adjust your scale until the wheel size feels "right". Chassis testing basically has to be done with physical parts. The collision-detection algorithms of CAD programs are either suspect (LDD) or nonexistent (everyone else). In addition, some problems will only manifest on real models -- sagging beams, wheels slightly smaller than their quoted size, etc. You'll be using the wheels eventually, so no real harm in ordering them early, right?

I'll address your questions in reverse order. The official Lego drive wheels are the same size as the BBB "L" drivers, with a few differences: - BBB wheels come in more colors - Official Lego wheels have a counterweight and more spokes - Official Lego wheels have a groove for a tire (rubber band) However, you might not want to use these wheels; see below. I'll describe what I usually do: In most cases, I start by finding an engineering drawing of the locomotive. Here's one for the P36: Full size at Wikipedia. The engineering drawing helps show what the locomotive really looks like, which can often be distorted by photos. You might also want to pick a scale to model at. This is actually more detailed than just saying "6/7/8-wide"; In my case, I usually model at 15 inches / stud (~155 mm / plate). If you pick a scale, you can put a scaled version of the drawing in front of Lego graph paper to help you figure out how large various parts of the locomotive should be. In this case, at the scale I use, the P36 is ~8 studs wide. This isn't too surprising -- Russia has a gigantic loading gauge and its locomotives are often huge. However, at this scale the 1850mm-diameter drivers should be about 38mm in diameter -- closer to the size of the BBB "XL" drivers! After figuring out roughly how far apart everything should be, I make a skeleton of the chassis. This allows me to test the running characteristics of the locomotive before starting work on anything else -- if the chassis doesn't work, there's not much point to anything else. Usually, all the drivers will be mounted to a single rigid frame, and the front and rear trucks will pivot off of this frame. The pistons and running gear are also usually attached to this rigid frame if you have working driving rods (rather than just connecting rods). It's also important to consider how the locomotive's body will attach to the chassis. On shorter locomotives, you can simply attach the body to the rigid frame containing the drivers. However, on longer locomotives, doing this will result in gigantic amounts of overhang on curves. Instead, you often have to attach the body with rotating (and sometimes sliding) joints to various positions on the chassis. What's best in this case strongly depends on the actual locomotive you're modelling, and finding the correct pivot points requires trial, error, and practice.

The official Lego wheels probably have more rolling resistance because I tested them with the tire on. I suspect if you remove the traction tire they will have similar rolling resistance to BBB wheels. We didn't test any Technic axle pins, but I expect the rolling resistance of those will be higher than a Technic axle. This is because the pin is not as well supported as an axle, and the resulting cantilever forces will increase the resistance.