I spent an absurd amount of time developing a suspension on the EMC 40. Remember, I'm working with Kato parts, so the basic 11-105 trucks are designed with floating end-axle pickup cups pushed down by pickup strips just like the bigger diesels. In a tiny 8-wheel chassis it is complete genius and works better than good, you can step through some absolutely horrid track and literally watch wheels bouncing all over staying in complete contact. When you go down to 4 wheels everything changes. On the EMC40, the wheelbase was spread out to 13', one axle powered. I 'locked down' the powered drive axle with wire so it was fixed, tried to leave the other end idler axle float with pickup strips. Didn't really work. I then locked down one side leaving only one side left to float, and have a LOT of vertical play. That idea worked well, the 3-legged stool with the fourth leg on a spring so that wheel could go up and down and still pick up. But one axle drive.... doesn't stall, doesn't pull much either. On the trackmobile (11-103) it's inside wipers and NO vertical bearing movement at all. If it hit a spot and decided to teeter on two wheels, and one of those teeter spots was over a switch...dead stop. No fix possible. I had to add the pickup car. Same problem with the Modemo 4-wheeler, too stiff, add the flatcar. On the 25 tonner - using the 11-105 power truck - the worm end is 'locked down' with the end cups "stapled" to the inside of the truck with .010 wire. Pickup strips push down on the center of the end-cup pickups, and the nose end is left to float a bit. It sorta equalizes, but if you watch the video you'll see the cab move up and down about .030 as it changes direction. It deflects the worm down, the cab up, and the nose down in reverse. In forward it flattens out. Tighten it up so it doesn't do that and it won't equalize, either. If you didn't have the vertical motor drive you wouldn't have that problem. You can also see the nose-end wheels dropping in frogs independently and recovering nicely, that's the pickup springs at work. Pull the wheels apart to clean it and you get to adjust and reset that entire deal, very delicate balance. (the funny part is that when I ran the actual 25-tonner at the museum, it did that same exact move - put a heavy load behind it, open the throttle, and the cab went UP. So as a feature, it's prototypical) But the trick is that something still has to push down vertically on the axles so there is some springing, or like Nigel did, only do it to one side of one axle leaving the other three points fixed. Fourth point has to move vertically quite a bit with that method, but it works. Worked well on the EMC40. That's the real trick, harder than L to make it work right, particularly when you're also trying to power that axle. It wouldn't have to be super complicated. One side of the frame has a vertical slot for the axle hole. The wheel bearing on that spot is on a phosphor bronze spring wire, anchored toward the center of the wheelbase on the frame, deflecting the axle to the bottom of the slot, pushing down. With enough vertical play, you may have it rocking a bit but all 4 wheels will stay planted. If I wanted to make it complicated I'd figure out how to adjust it from the bottom with a 00-90 screw so that you could set the ideal balance weight on that fourth leg. I can't do that stunt retrofitting Kato 11-105 parts, but in all seriousness a little redesign on this concept and it would work just fine. I, for one, will pay for that. As far as I can see, that's the ONLY feature here I could improve on. If you have powered frogs the short wheelbase 4-wheelers WILL WORK with this springing and suspension concept. The more weight you can pile on the better, but pounds of weight won't solve the problem of a stiff 4-wheel suspension.
The "secret" ingredient is the high torque driven pair of worms. They always want to throw the wheel gears out of engagement, in this case they're generating a flexible downward pressure. Obviously some precision is getting involved too. :0)
Update. The N-scale powered chassis by L.G.Thek Brasswork will be available sooner than originally planned. The chassis main frame components are already here, production assembly is nicely progressing. I've picked three units from the first batch to complete and test run them on my freshly made test layout built on the top of a blue foam sheet, using Atlas code 55 flex track and #7 turnouts with powered frogs. (The industrial sidings are not done yet.) All three chassis are excellent performers, indicating the design works well For production tests I'm using a "Lambda" pure DC power supply, constantly monitoring the current drawn by the chassis tested. A few results of the first test runs: Starting voltage is around 1V DC. All three chassis were able to crawl through a clean Atlas turnout with 1V power without stalling. The no load current drawn by all of the chassis is around 10mA. Testing will continue with added weight in the form of a scale test shell and various assemblies of freight cars. Video clips to follow.
Another update. I've quickly made a shell (about the size of a GE25 tonner) that comfortably fits over the chassis. The complete little industrial switcher weights 21.4 grams, and with the added weight the chassis performs even better. It pulls six Kato hoppers with ease at any speed. The six car train starts to move at 0.8V pure DC, and crawls through the Atlas turnout without any hesitation. Tests will continue with various controllers, and video clips are coming soon. An additional note, we're working on the R&D of a similar size 25t Plymouth industrial switcher shell. It will be available as a brass kit, assembled, unpainted shell and ready to run locomotives.
The first video clip of the world's most powerful small N-scale powered locomotive chassis is here. http://youtu.be/zvFnlvGqYG8
That is completely amazing! Look at how slow it crawls, and right through a switch, with not a single stutter! Lajos, you DA MAN! If I had money to spare, that would be an investment I'd be making. :thumbs_up::thumbs_up:
Nice! However, I think the front wheel in the video is not concentric on the axle. There is a speck in the center, but if you look at the outer tread area it appears to wobble.
There are lots of actions due the irregularities of track work. The axles have plenty of free play, so the face of wheel is out of plumb frequently. Lajos
Impressive!!! Now if we can get a set of cylinders and side rods on that baby there is a lot of small steam both standard and narrow gauge that have suddenly become a possibility. Not to mention a whole slew of Davenport and Porter gasoline and small diesel switchers.
OK, you've got me convinced. My 25-tonner is eligible for upgrade like an old phone. The only thing left that I don't quite understand is how to get one of the chassis!
The chassis will be available mid-week at L.G.Thek Brasswork, then shortly after at Stonebridge Models too. My question is, what do you think, which locomotive body should be the first to fit over this small chassis, a 25 ton Plymouth, or the GE23t boxcab?
I'm rather partial to the inside-frame JDT if it will fit: http://www.rr-fallenflags.org/misc-m/mors0abp.jpg
Wow, I was leaning heavily towards a boxcab (not too late to join the challenge, Lajos!), but that JDT is awesome!
"If" you put Kato 11-105 27" wheels on an 11-103 chassis (which has about a 13' wheelbase), hack the %%$# out of it, and pick the biggest Trackmobile made, you can do a model right now. Another trainboarder developed the concept, I just finished it off a few years ago. (Another one that I need to put up a video on) Here's the shot of the modified 11-103 chassis (severely cut down), and the original 25-tonner mechanism beside it with the vertical motor on the 11-105 pickup truck for comparison, beside that a 'stock' 11-105 chassis. The 11-103 chassis works fine, but it is very stiff, necessitating the scale test car add-on as a pickup car. This baby is why I keep picking on the stiff four-wheeler issue - I couldn't beat it. Which is also why I never did a kit based on that chassis. I think the videos show, however, that his mech has enough flexibility to pull it off where this one didn't. Lajos videos have mde a believer out of me, and I'm pretty skeptical as I've been messing with this stuff now for six years. You need tiny wheels and a long wheelbase for a trackmobile. His basic design concept could be adapted, me thinks, other than the gearing might have to go inboard rather than outboard of the axles. The Trackmobile, however, is another ideal application of photoetched brass if somebody wants to take it on.
I'll put this up too.... this is my attempt to 'fix' a Nigel mechanism. He had a rubber grommett system on the end of the motor instead of a gear, I put on a zip-zaps gear and spur, and put in a replacement zip-zaps 3v. low RPM motor. Like most pager motors with a resistor in series, it lacks torque (converts it into instant heat!) under full-slip load. You can overcome that with a gearing system that minimizes the motor load variance. I only put this up in salute to what Lajos is working on. This 'sorta' worked but not well enough to finish it. Oh, and did I mention it made enough racket to wake the dead? (imprecise plastic gears = horrific racket) Another lesson here is you don't put wipers on wheel treads. Bad design concept #106. I'll also put up another failed concept - using a Tomytec power truck with an on-boad 9V Motorola pager motor (about $2) to beat the resistor problem. This SHOULD have worked well, it was wonderfully equalized. Truth is that it did work, but had absolutely no torque. You could couple up, hit it with about 6v, and then after it got moving it was a rocket. The motor was simply too small. Another abandoned idea. So I went back to the Kato 11-105 motor mechanism, vertical motor mount in the cab. 12v motor with enough torque, fair equalization. That's what's in the 25-ton video. Close, good but not great, again, no potential for repeatability by other modelers. Which is why, people, after six years of messing with this stuff myself, and seeing what he's done, I say it's time to recognize what's been developed by him and simply buy one and quit complaining!
I had seen the development of this chassis in the Z scale section. Its a cool idea and I would love to see some smaller industrial switcher hit the market (even on a cottage industry level), but the all up price for one including the chassis and shell kit just doesnt make sense to me. If the price was more around $75-$85 I think it would really open up the market. Still it is a step in the right direction and proves that critters are possible to produce.
To avoid torque losses of pager motors, the only solution I've found is to connect two or three identical motors in line. The number of motors depends on the voltage rating. I've used this concept for powering the engine of my Z-scale 60ton Shay locomotive. A 4 x 5mm Motorola motor is powering the crankshaft through a double worm reduction gear box, and another motor in line is running without load. The charm of this system, in case of high current caused by the lock up of the drive motor, the load free motor takes the heat and works as a fuse (not the cheapest fuse, but still better than rebuilding the crank gearbox :0).
