lmdesigner42

Brilliant MOC, like always! You continue to be an inspiration to everyone else with the level of functionality and elegance in your builds. The suspension travel is very impressive for the scale too, a lot of truck trials don't have that much.

@Bartybum I implemented your suggestion, reinforcing the lower boom with 3x11 panels. The twisting and bending is greatly reduced now, but the motor still struggles to lift the upper boom. Maybe I can fit some gear reduction into the superstructure. I don't think increasing the shaft speed along the length of the boom would help, since the full torque of the actuator would still need to be resisted by the lower boom at the end.

Thanks for the kind comments, all. @Bartybum It might. I thought about replacing the liftarms with studded technic bricks since they are stiffer, but I don't have very many in yellow. The main issue is that the boom's cross-section (-----) is terrible for resisting the torque of the driveshaft running through it. A circular or box cross-section like real bucket trucks have is much better.

Finished just in time! It's not the prettiest, but all 7 motorized functions I wanted are included. The colour scheme ended up being like Liebherr, with dark grey, yellow, and white. And yes, the railings are all made with DBG axle joiners. The most important, and also the weakest feature, was the second joint in the arm. As seen in the video below, the L-Motor is barely strong enough to lift it. This is due to a combination of factors. 1) the L-Motor is only geared down 5:3 before the actuator, 2) there is extra friction from the long gear train and shafts, 3) the 4-bar linkage at the second joint increases the mechanical effort, 4) the arm tends to twist and bend under torque and load (see below picture), and 5) the length of the arm greatly increases the effective load from the bucket. The last factor is the most significant. The first version of the bucket was made from stacked beams, and proved way too heavy to lift, so it was replaced with a more lightweight version. It may be possible to increase the stiffness of the arm and the gear reduction from the L-Motor, but that is difficult without increasing the weight and bulk too much. On the plus side, the total reach is pretty high. The 7 motorized features work as follows. There are 3 L-Motors coupled to a distribution gearbox à la 8043, shifted by an M-Motor. One side of the gearbox controls the left and right tracks and the outriggers, the other side controls the arm joints and rotation. The 7th function is a motorized winch at the front, operated by the M-Motor that shifts the gearbox. A white clutch gear allows the motor output to slip when the gearbox shifter locks, while continuing to rotate and operate the winch. Thus, 7 RC functions are accomplished with only 4 motors. The battery box is easily removable from the underside with 2 red pins. There is quite a bit of empty space under the grey 'engine cover,' more functions probably could have been added with a more compact battery box/control setup. A few small details were also added, such as a cabin with seat, lights, control sticks, opening door; as well as railings and supports for the arm and bucket. Finally, a little video showing all of the features: More pictures are on Bricksafe: https://www.bricksafe.com/pages/lmdesigner42/tracked-bucket-truck

Entry name: Tracked Bucket Truck Functions: Left track drive Right track drive Raise/lower outriggers Rotate boom Raise/lower first arm section Raise/lower second arm section Extend/retract winch Cabin details Bogie suspension Note: All 7 main functions are motorized and remote-control with 1 PF M- and 3 PF L-motors. Video: Link to discussion topic:

The outriggers are all done. They're not strong enough to actually lift the vehicle due to the linkage geometry, but the folding/unfolding range is pretty good. I also added a few more parts to finish the bucket arm and start on the bucket itself. If I hurry, I think I can get the rest finished in time.

I finally have a bit more progress to report. I added a bit more structure to support the turntable, and a rotation mechanism using a worm/8z gear combo. More reinforcement is needed, though, the tracks are only attached by pins. There's very little space to add a proper chassis around the gearbox, but on the plus side, the narrow width means that the bending stresses are already lower. The arm has also been lengthened and updated with a more efficient actuator placement and a 4-bar linkage for a wider range of movement. It reaches pretty high, even without the bucket. Finally, a simple video to demonstrate the motorized functions. I'm happy to report that everything spins the right way!

That's an impressively designed MOC, and a great attempt to replicate a cool and functional RC crawler in Lego form. It's disappointing that the plastic gears can't handle the stress in the end, even with lubrication and metal support. I know it gives a better look, but the fully paneled bodywork at this scale adds a surprising amount of weight. Would it be a possibility to shrink it to 70-80 mm tires, have fewer diff locks, and thus reduce the weight and drivetrain stress?

That's a shame to have your performance let down by the power supply, after all the effort you put into the chassis geometry. Would it be of any benefit to put a lower current limit on just one of the buggy motors? That way, both could still run fully for high speed/low torque driving, while for high torque crawling the current output would favor one motor and allow it to produce more torque before the BuWizz cuts out.

It's great to see some more progress on your rock crawler. Based on the amount of effort you're putting into the chassis design, it should perform very well! With regards to the negative caster angle on the rear axle, I don't believe the caster angle really exists unless the axle is steered. That being said, possible effects are: Increasing the angle on the axle-side CV joint (usually not good) Adding a toe angle and tire drag, IF there is any camber on the rear axles. I think your design is close enough to vertical though that there shouldn't be an issue.

It's always fun to push the boundaries of Lego performance. Your math is correct, longitudinal speed is directly proportional to tire radius. However, you may want to consider some additional gearing down, since heavier or softer tires have additional power loss from higher inertia and rolling resistance.

Great model! Using green for the cab was a bold choice. The hooklift mechanism is very impressive too, and educational for how the real-life version works. Is there a reason you chose an IR remote for control rather than an onboard switch?

I made some more progress on my entry, the distribution gearbox is now finished. The left and right outputs on the motor side (LBG 16t gears) drive the left and right tracks through the bevel gears and brackets at the other end of the assembly. The central output on the motor side will drive the outriggers via the red axle connectors. On the non-motor side of the gearbox, the central and right outputs are transferred concentrically up through the turntable to operate the boom. Finally, the last output, the isolated red clutch gear on the left, will drive the turntable. This setup allows the turntable and boom bending to be operated together when all three driving rings are on one side of the gearbox, with the tracks and outriggers on the other side. Now the next step is to put a sturdy frame around all of this to mount the tracks and turntable. I also have a rough draft of the boom done. It would be nice to give it a boxy cross-section like the real machine, but it's hard to do at this scale due to the size of the large linear actuators. At least the range of motion is pretty good.

Hi everyone, my idea for the TC29 contest is a tracked bucket truck similar to the one below. The plan is to have six motorized functions (2x driven tracks, outriggers, 3x boom movements) using a distribution gearbox à la 8043. White would be fine for a colour scheme, but it's a tad boring, maybe purple and yellow will work? So far, I have a rudimentary tracked chassis with 3-bogie suspension. The 3x19 frames are placeholders, but the width is correct. I have a good start on the distribution gearbox, the orange shaft drives a worm gear to move the changeover catches back and forth. It's going to be fun routing the coaxial driveshafts to go under the turntable :).

Nice little SUV! At first glance, it seems almost as realistic as the much larger 42177. And two more types of fenders/mudguards in a unique colour to add to your collection :). I wonder if that off-road tire pattern will come in any more sizes? This is the third size, and I believe there were only three for the tractor tire pattern.