howitzer

Yeah, vibrant yellow is the TLG's official name for neon yellow...

Are those rims neon yellow or normal yellow? Can't tell due to the neon green tyres...

Too bad you didn't finish your entry, it would've been really interesting to do a comparison!

I cast my vote but it was reallly hard thing to do, considering the huge differences between the various entries, all of them so unique and wonderful. I'd have hoped more entries but on the other hand, having even more of them would've made voting even more difficult.

Looks very Polished with Stellar execution. I'll get my coat ->

I'll have to see about it. The lead screw transmission is something of a bummer for me as I couldn't get it to work but I have an idea for alternate solution which I wasn't able to attempt as time ran out for the contest. Tailstock would also be an interesting challenge considering it's requires stuff that can't be easily made with Lego (such as drill chuck) so I'll see about it. Building a casing would also be nice. You probably could reverse engineer my bearing design from the photos but I'm not sure if you should, considering that it is probably much too large for the project you describe and there's no way it could withstand the forces present when running several thousand RPM so I believe you'll have to think of something else. Unless Lego purism is an absolute must, you could try a third party liftarm with integrated ball bearing.

Yeah, that's true, what the video shows is clearly well out of design range of the motors and I wouldn't be surprised if the maker burned out several motors in the making of that video.

I do! Thank you so much, the entry post is now there!

Metal lathe Unfortunately my entry was far more complex and difficult thing to build than I had anticipated, so my entry is barebones and missing some of the features I originally planned. The implemented features include: Spindle on ball bearings Motorized with 9V train controller for multiple speeds in both directions Thread cutting gearbox with 4 speeds and direction switch Motorized longnitudal feed Manual traverse feed Self-centering chuck with three jaws

I was just about to make my post to the entry topic and it's locked :(

I hope these two photos help to explain it: In the first photo you see the "key" for adjusting the jaws, which drives both, the worm gear that connects to the jaws and the 20T->12T->20T->banana gear which rotates around the whole chuck, driving each of the jaws.

So when's the contest going to close @Jim ? I'd love to have a month or even a week more of building time to polish my entry but we're already way over the original closing date so...

Since the last update I've been building with all the time I could spare and as the competition draws close I have attempted to get something presentable done. Here's a photo of my entry as it is now: As you can see there's a lot missing, most importantly toolholder, tailstock and casing. But the things I was able to build do work to such an extent that I consider this project a success, even if there's much room for improvement. The final list of features is: Spindle on ball bearings Motor control with 9V train controller for multiple speeds in both directions Gearbox with 4 speeds and direction switch Motorized longnitudal feed Manual traverse feed Self-centering chuck with three jaws When beginning I thought that the ball bearings might be the most difficult thing to design and I was totally wrong - those ended to be among the easiest parts of the build. The chuck demanded some serious creativity and while it works in principle I'm not satisfied with it, as it has very high resistance and is hard to open or close. Some lubricant would probably help but at this point I don't want to stain my Lego. Another serious hurdle to my progress was the lead screw connection to the tooldholder sled. I made numerous attempts to connect it so that the lead screw can turn constantly and is locked for feed from a switch in the sled, but I couldn't get it to work at all so I had to settle for this less realistic version where the lead screw and the sled can't be disconnected and the switch between manual and automatic feed happens at the gearbox. The lack of casing also makes the whole thing wobblier than it should be, which doesn't prevent it from functioning but is apparent when you try to run it. This whole project feels like I've been exploring the limits of what can be done with Lego and it has for sure been a great learning experience even if I'm not fully satisfied with the result. Anyway, I hope you like it! Here you can find some more photos of the progress, also on the failed lead screw transmission thing: https://imgur.com/a/P548tFF Here's more photos of the finished thing: https://imgur.com/a/kMXrnVE Here's a video:

It's not even about the motors but getting enough power to drive them. Lego motors driving 89509 blades with enough power can make for an actually flying machine, but it requires a custom power source and controls. Brick Experiment Channel made a drone like this few years ago: Check this out:

That frankenstein connector looks really cool, I hope it's 60° and I hope they release other connectors with 60° or 120° angles as structures with three- or sixfold symmetry are currently quite difficult to make in Technic.

The problem here was the connection of 28T <-> 16T gear which is slightly too tight and thus has high resistance so lubricant wouldn't be of any use there. Eliminating it helped tremendously. --- Today I've been tinkering with the lead screw connection to the feed and while the 27266 makes for a nice sprocket for the screw to drive, the distance needed requires some annoying connections. Any distance achievable with whole- or half-stud or plate-height connections doesn't seem to work as the distance needed involves half-plate thickness. So I guess there's going to be some strange connections in the feed mechanism. Here's a photo of the test connection I made:

Same here. My entry is still well in progress but I really hope to get it into at least mostly functional and presentable form, though the time is running short...

Swappable attachments for an excavator would be a very welcome function upgrade, as practically every real construction excavator has this feature and no Lego excavator has yet demonstrated it.

Haven't updated for a while but there's been some progress nevertheless. I've tinkered with the transmission line from motors to the gearbox and from there to the lead screw. I built a mockup of the downgearing needed to drive the gearbox, which I simplified by ditching half of the speeds and added a direction switch. The previous design had a high friction connection which is bad because there's a lots of gears and thus lots of friction already. Beside tinkering with the gears I've been attempting to build the chuck. This has been quite a challenge with the requirements of having three jaws and self-centering clamping. My solution is to drive the jaws with a worm gear+rack gear combo which in turn is driven by a ring of banana gears (yellow) sandwiched between more banana gears (black). There's quite a bit of friction but at least in principle it works. There's also some slack which requires idler gears to keep the ring gear in place so it connects properly with the gears which drive the jaws. I also built a stand to raise the thing higher, though it's not yet connected in any way and just sits on the stand. Here's a photo: (Sorry about the mess, I couldn't be arsed to clean the table for photos as I'm going to continue building anyway.)

I missed this when originally posted, but it's obviously quite an ambitious project. I hope you'll get something out of it even if it doesn't work out for the contest. In the meantime, this might give some inspiration:

Wow, there's a dark mode! I didn't even notice before you pointed it out, this is great! Other than that, I guess it'll take a while to adjust to the new theme but there doesn't seem to be any serious problems with it for me at least. The forum appears to be much faster than before the update which is also good.

Another update: I realised that having the spindle driven by both, variable speed motor (using 9V train controller) and multi-speed gearbox is a bit unrealistic, so I decided to drive the spindle straight from the motors with appropriate downgearing. On the other hand, the thread cutting feed requires a gearbox with several speeds so I decided to reuse the gearbox I had already built. The lead screw would also require a significant downgearing relative to the spindle and for friction reasons I decided that the downgearing must happen before power is fed to the gearbox (and from there to the lead screw) so I built a distribution gearbox on top of the spindle. There's also a half-stud offset with the ring gear that's coupled to the spindle and that require some half-stud magic to get everything properly aligned with the distribution gearbox. The bearing frame and various gears also impose some serious restrictions on building so the frame of the distribution gearbox is a dense mess of connectors but it feels strong and secure. Here's a couple of photos: Here's also a computer render of the distribution gearbox design to show the gearing (note that the 16T gear that drives the 40T gear is missing from the photos above):

A quick video to see if there's any obvious problem with the drivetrain. Apparently it works at least with slow speeds even with the current quite wobbly support structure. I'm powering it with the 9V train power supply which I intend to integrate into the build.

A little bit of progress. I built the gearbox (8 speeds for now, I'm thinking of adding a hi/low selector to double the speeds but we'll see) and positioned it so that it can connect to the spindle. The black banana gears are where the connection happens and they're driven by a pair of 20T gears. I wanted to use 32T gears as that would be more efficient but there's no space between the banana gears and the spindle shaft. The gear shifters are the two DBG 24T gears at the top left, which I'll eventually route to proper shifting knobs somewhere in the front of the machine. The whole thing is still very wobbly due to the lack of supporting structure and I don't dare to try running it motorized but turning by hand it works fine. Next I'll get the support up and attach the motors and then we'll see how it works.

The limit of 32L axle indeed is the reason why I opted not to even try it with the old worm gears. It's true also that you could have the worm gear in the carriage and pair it with stationary rack gears but not being realistic I didn't consider it either. Yeah, the spacing is 2L. I haven't yet built a solid support structure for the bearings so I haven't tested them properly but we'll see when the project goes forward.