2GodBDGlory

Perhaps it had something to do with the fact that I was running nine motors off of it at once--A Servo, four Ls, and four XLs!

I just bought two of those Chinese buggy motors for $20 CAD, including shipping, and so far they are impressive. I think they have performance similar to the original Lego ones, but for a tenth or so of the price! Yes, they may be worse quality than the Lego ones were originally, but I feel fairly confident that they are better than 15-year old, used Lego ones, at any rate. One thing I tried to unlock more performance was buying a near-hobby grade electronics system. The whole setup (Remote, circuitboard, battery ,motor, and servo) cost me about $50, and has great power, but it is difficult to hook up to Lego, and even when you do, it is almost impossible to make a high-performance car, for the simple reason that the RPMs on the output axle are so high that a load will twist the axle in half. Not pretty.

Do you think the higher voltage would eventually cause problems in the circuitry? I once hooked up a hobby 9.6V cell to a PF receiver, and the receiver didn't last long. Lego motors are supposed to take up to 12V (I have heard), but I don't know about control systems. If the PU hub can take it, though, that could be a very interesting high-performance solution! Good ingenuity!

Great looking model!

I got a 42069 in a damaged box for $115 CAD--the original CAD price was $240, by the way.

Wonderful job! The appearance is remarkable, and the functions are impressive, too! I especially like the motorized windows. I had wondered if it was possible, but thought it would be too difficult. Good job proving that wrong!

I can't say whether or not it is possible for this gearbox to slip entirely, but I once built Nico71's similar CVT transmission and tested it in a 4x4. I found that in extremely difficult terrain it could slip, but it sure took a lot to get it to that point. Still, though, I am not sure how that happened. It looks like an interesting and original gearbox!

I have found with many of my motors that the insulation on the wires at the points where they enter either the motor or the plug can wear down, causing servos to malfunction, and normal motors to stop operating. If this is the problem, trying different wire positions, and pressing the wire into the motor will likely make a difference. When this happens to me, I will open up the motor, remove the wire, cut out the bad portion of the wire, and re-solder it. However, when I try this on servos, I usually fail because of the four leads in a small space on the circuit board; perhaps a more skilled solderer would have better luck. Of course, you may have a completely different problem...

I saw some YouTube video once that suggested opening up the motor and cleaning off the semicircular contacts with a pencil eraser (and then blowing off the eraser dust). I have not tried this personally, but you could give it a shot!

The first suggestion could be worth trying, but I am unsure abho The first suggestion could be worth trying, but as for the second one, I actually started out with that part (albeit with normal tiles on top), but I found the diameter too small to get enough ratio spread, and it seemed less controllable. I am now starting to think about testing this gearbox in a large car model, so any help I can get will be appreciated! I will test with textured bricks soon. My design is a similar one to that bike setup, but mine adds friction to obtain a continuosly variable ratio spread, while the other design appears to have a number of fixed speeds. It is a similar principle though, and one that is interesting to see used practically. Thanks for the feedback! Cool to see the history of that design, as I had no idea it had been used before. I guess no ideas that simple are original these days!

I agree, the ratio spread over the tire is a bit of a problem, but I could not achieve enough friction with the other tires I tried, and there is at least more surface area with this tire, hence more grip. I suppose its width also contributes to the rubber streaks that showed up on the disc. Another possible explanation for the slippage there is simply that there is more torque available to put towards slipping in that gear.

After seeing quite a bit of activity on the CVT front from Sariel lately, I got inspired to try my hand at some designs again. I started trying to make something similar to Sheepo did years ago, but stalled there. In the meantime, I did some research, and saw something that inspired me. It was in the [GBC] Let's build ball mechanical flowmeters post, but the post was very in-depth, and I quickly got lost. Thus, I am unsure what the original use of this mechanism (posted second from the bottom at that thread) was, but it inspired me. After a bit of experimentation, I came up with this design, which has a large spinning dish meshing with a tire. The tire slides along an axle to "mesh" with the dish at various diameters. I did some fine-tuning to get the friction to the right point, and where it is, with drive from an XL motor, there is no slippage in the fast gears, and some slippage in low gears, but only with lots of resistance on the output. This could be avoided by gearing for less torque on the input, but considerable torque is needed to work the transmission (pointing to low efficiency). One of the nice features of the design is that if the wheel is slid far enough to the low side, it will pass over the center of the disc and create a range of reverse gears. It is also important to note that the gearbox cannot be inverted, that is, you cannot put a motor on the output and treat the former input as the output, because the tire will quickly pull itself off of its wheel if this is done. Shifting of the tire can be done in multiple ways, but I used a large linear actuator. An XL one would take up a lot more space, but would allow for some faster reverse gears. It is also recommended to find an older, worn-down wheel, because worn ones will slide along axles readily, while still transmitting drive. P.S. If you are trying to build this design, you should know that I used Technic bricks with the studs facing up to raise the disc slightly, increasing friction. This is sadly not visible in my images.

I would say the 42043 Mercedes-Benz Arocs 3245. It was my first Technic set, and it was great! Great value for the money, and a little of everything. Pneumatics, a linear actuator, transmission driving rings, shocks, turntables, gears, lots of panels, a multi-purpose motor, lots of multi-purpose tires, etc. The main downside is that it is not available new, and has increased in price a little on Bricklink.

Yes, I think it does. This could be solved by essentially putting a gear ring around the planetary gearset for the ratchet to mesh with, but I think it would be fairly hard to do in Lego. A large turntable might work, but that would just be... large.

Thanks! That is a good point. It could sometimes be a packaging problem, but it is probably the best way to adjust shift points. Here is V2! It uses the rubber-band ratchet idea, and has an updated friction mechanism using rubber track inserts. It, like the previous design, will wear down the rubber friction elements eventually. https://youtu.be/DY6t_UeW71U

Last night/this morning I took some of these suggestions and built a compact, reversible gearbox, using the rubber band idea. I should get it posted here soon. I am pleased with it!

Good idea. It would be a bit less energy-efficient (always slipping the rubber band), but a whole lot more space-efficient.

I can see that working, perhaps with an auxiliary Servo motor hooked up to the driving channel. It could be hooked up to the ratchet using a rubber axle joiner, allowing it to rotate the ratchet 180 degrees while adding a spring-loaded effect. Maybe when I get some time I can build that...

That sounds like it is probably the best solution for models that require lots of torque in reversing. It is able to reverse on flat ground (with a light enough model), but when the going gets tough, it will give up, so a reverse gear like your suggestion would be good for heavy models or off-roaders.

Yeah, I'm sure that could be done. It would make it larger, less reliable, and less efficient, but it might be worth it.

Here is a new automatic gearbox design I developed last winter, after I got my first planetary hubs. It is a very unusual gearbox for Technic, without any traditional gears, but offers high strength and efficiency, and can shift for itself. Its operating principle is as follows: The input shaft goes to the input side of the planetary hub, and the output is hooked up to the output of the hub. However, with only this setup, any load will cause the hub assembly itself to turn, rather than the output, so a small tire is added to create friction between the hub body and the input. With this setup, the gearbox will tend to stay at a locked 1:1 ratio, but it is still capable of slipping and sending all its power into rotating the hub body against the friction. To prevent this, a pair of ratchet-type things are added, which only allow the hub body to rotate one direction. Thus, under light load, the gearbox will again spin at 1:1, but at higher loads, the hub body will slip against the rubber in the opposite direction UNTIL it strikes the ratchet. At this point, the body is stopped, so the gearbox works at the standard planetary hub reduction of 1:5.5. The main disadvantages of this gearbox are that it is difficult to adjust the friction, and that it only really works going forwards. If the motors are reversed, it causes the gearbox to automatically shift down into first (good), but it also is able to slip indefinitely, so it is not good for off-roaders that will need to reverse in challenging terrain. Additionally, multiple copies of this gearbox can be attached in series to add more speeds, with one speed being added for each additional assembly. However, this increases in volume rapidly, and the only possible gears are one to powers of five, so 1:1, 1:5.5, 1:30.25, 1:166.375, 1:915.0625, and so on. As you can see, the ratios quickly become far too low for any practical use. I tested this gearbox in my Toyota Land Cruiser 70 model, and it met durability requirements. I used two gearboxes side-by side, essentially doubling the resistance needed for a downshift. Unfortunately, it would very rarely get into the high gear, due to the high weight of the model. Also, the rubber tires I was using got somewhat worn down. I feel that it could be valuable for fast, lightweight off-road buggies that need a little extra torque once in a while to get over obstacles. Let me know what you think!

Fascinating! CVTs are one of the "frontiers" of Technic, I suppose, and that is a very unique solution. I am still waiting for a heavy-duty manually-controlled one, though. Good work!

Sweet! LBG is my go-to-color for almost everything! (Not that it has the best part variety, it is just the only color I have enough of for big cars)

True, but the Control+ system doesn't have an option for a smaller battery like the PF rechargeable or AAA boxes.

I did use a large actuator for steering in an off-road crawler I recently built. It was quite strong, and allowed huge gear reduction, but was very slow. It worked well in a crawler that would sometimes need to lift its weight when steering, but would be a poor choice for something needing responsive steering.