TheMindGarage

Wow - that looks great with the panelling! Not a fan of linear, unsynchronised gearboxes, but I guess they're fine for manual shifting.

Don't have any converter cables :/. I think I'll try 1x Large and 1x Medium motor with an adder - that's all the power I can get.

What? Then I'm doomed. I was hoping that I'd be allowed to use MINDSTORMS solely for the motors powering the pump, but if that isn't the case, then I can't enter :(.

Good start - any close-ups of the suspension? Not sure if two springs will be needed. I tend to build cars slightly smaller than that (56x25x15 studs is typical), but my cars are built very densely and stuffed with MINDSTORMS. And I only use one spring.

Upload them to an image-hosting site and embed them. Sounds cool. Lack of suspension is a little disappointing though. How does the gearbox work - I'm guessing a transmission driving ring.

I hope so! Currently my setup of a single Large motor powering a single pump (from 42043 set) geared 1:5 up stalls the motor under load, and gearing it less makes it unbearably slow. But 3xEV3 Large motors will definitely do the job.

A quick question. In the rules, it says that electronics such as MINDSTORMS aren't allowed. But elsewhere in the rules it says I can use any type of motor, as long as it's operating a pump. Would it be ok for me to use EV3 Large motors to power my pump since I have very few PF motors. The EV3 motors wouldn't be used to do anything other than run at full power to power the pump.

True - it take about 1/2 a stud of steering rack movement to make the differential unlock (I did say that this may be an issue in wide turns). But the rack's maximum movement is 2 studs each way, so the differential will be unlocked with anything more than 1/4 of the steering lock applied, assuming that the rack is the limiting factor in steering and not the steering linkage.

Haven't tested that fully. Seems like it'll work OK - bevel gears are much better for this kind of thing than regular spur gears (like 8t and 16t). I was considering using a transmission driving ring, but that proved to be much more difficult.

I've made a new gearbox for my next car. This gearbox can either be set to a gear ratio (driving the wheels) or to a function, allowing the drive motors to power something else. In total, there are 4 forward gears, 2 reverse gears and 6 function "ports". The reverse gears weren't intentional - they happened to exist when I added the gearing for the forward gears. The gearbox consists of a turntable with an off-center gear positioned on it. This design uses two off-center gears on the same axle - an 8t and a 12t. This allows more meshing combinations. The off-center gears are driven by a 24t gear in the middle of the turntable, which is powered by the drive motors. Around the turnable, there are many axles with gears on them (12 in this design). When the turntable is rotated correctly, one of the off-center gears meshes with one of the gears on the outside, turning that axle. Some of the axles are connected with extra gears to form a transmission with different speeds; the unconnected ones will be used for functions. Here you can see the internal workings of the gearbox. These are the gear ratios (including the 3:5 gearing before the transmission): Gear 1: 1:2.5 Gear 2: 1:3 Gear 3: 1:4.167 Gear 4: 1:5 Reverse 1: 1:3 Reverse 2: 1:5 Functions 1, 3, 4 and 6: 1:7.5 Functions 2 and 5: 1:5 The gear ratios are rather close, and the reverse ratios are too high, but there is little choice in choosing gears since all of them have to mesh properly with the off-center gears on the turntable. I made all the gear ratios quite high since I'm planning to drive the vehicle with 2 EV3 Large motors, which have tons of torque. There are two inputs - this is purely because I plan to use 2 EV3 Large motors - one on each side of the gearbox. The shifting input drives the turntable with a 28:8 gear reduction - this could be increased, possibly with a worm gear. Note that it is ESSENTIAL to use a MINDSTORMS motor for shifting, since the shift positions are in strange places and not in order. This gearbox can handle plenty of torque - the gearing up before it does help. However, when under high load, the turntable can move out of place and make gears grind. This gearbox works best with minimal backlash on the shifting input. Also, some clever programming can make the turntable adjust its position a little bit depending on the amount and direction of the load, countering the forces pushing the gears apart. The gearbox is very compact for its functionality - comparable in size to a 4-speed sequential gearbox. However, it can only be used with a MINDSTORMS motor for shifting, which will make it useless for most of you guys (unless of course someone develops a version that can be controlled by a PF servo...)

I use the exact same scale and wheel combination for my cars, so I can give a few tips: Unfortunately, the width of the 250 GTO is 1600mm. That's only 20 studs, and a full independent suspension with a differential and those wheels is a minimum of 25 studs (the limiting factor is the length of the joints). When I make models, if the width should be 23 or 24 studs then I'm willing to fudge it and build the car a tiny bit larger than 1:10 in order to get the suspension, but 20 is too narrow. Since the real car is 2WD, independent front suspension is fine, but you'll have to do something different on the rear (either swing-arm, live axle or some highly unconventional independent variant without joints). I suggest that you start with the front and rear axles, then make a chassis with the correct wheelbase. Then add the piston engine and gearbox (if you're using one). While doing this, make SURE you don't use any red (or whatever colour the body will be) beams in the structure. You'll need to save red parts for the body. I usually build the internal workings in black.

After a little tinkering, I managed to create this self-locking differential. It locks when the car goes straight and unlocks when turning: A set of 12t gears are connected to the steering rack. When the rack is in the middle (and the car going straight), the two halfshafts are coupled together, locking the differential. When the rack moves to the left or right to steer the car, the 12t gears disengage with the 20t gears and let the differential act like an open diff: The main downsides I see with this setup are that the differential may stay locked during wide turns with small rack movement and the width of the axle is increased. A standard independent suspension with a differential and 68.8x36 ZR wheels (the combination I usually use) is 25 studs wide; with this feature it increases to 27.

What's the top speed on that thing? That person looks about 1:10 scale, so your wheelchair should be doing 0.8mph to make it scaled.

Looks great, and has plenty of performance in such a small scale!

Not worth it. 42000 is a nice set with good looks, but that's REALLY expensive.

I'm new here and haven't experienced a contest before. Can anyone explain how the voting works?

If you basically want a paddle-shifter, I've found that making a large (5-stud diameter) "+" shaped part out of 1/2-stud beams works better than using knob gears or a 2x2 System brick. I built a very reliable system on my Porsche 914.5 SpyTarg (200 shifts each way and no jamming, missed shifts or double-shifts), but it isn't the smallest.

A quick question - what is the definition of "model"? Does it have to be a scale-model or can it be a generic MOC (of course with pneumatics)?

I'm looking forward to the RC tracked vehicle - I'm hoping for something akin to the old RC motor.

I have made a stair-climbing robot, but it was very difficult. I had three axles fitted with independent torsion-bar suspension. Each axle was able to slide up or down (central differential and all) up to 8 studs using the 42043's outrigger parts and worm gears (that setup is extremely strong and has survived a load of about 18kg per slider in a different creation). I managed to develop a compact, high-torque Schmidt coupling to link the axles' driveshafts to each other and to the gearbox. Gearbox had 7 positions - four were forward speeds and the other three controlled the sliders. So to climb a step, the gearbox goes into neutral and engages the first slider, then the drive motor raises the first axle. Then the vehicle drives forwards a little and repeats this for the other two axles. The suspension and gearbox were really pushed to their limits.

Away from my LEGO, but here are all the planar meshing combinations possible: Mesh with 12-tooth gear at a distance of (4, 2) - that's 4 studs in one direction and 2 in a perpendicular direction. Mesh with 20-tooth gear at a distance of (5, 0) or (4, 3). Mesh with 36-tooth gear at a distance of (6, 0). (6, 1) may work, but probably won't hold much torque. Mesh with 40-tooth gear at a distance of (6, 2) - probably won't hold much torque. Mesh with 56-tooth turntable at a distance of (6, 4) or (7, 2). I don't think any others work (apart from perpendicular meshing, which my formula doesn't cover).

It was just an idea. The competition would become a question of "who has the most time to align gears properly". Lights and body shape. And if it's a 911, the slits on the rear. Although in the words of some car magazines "No Porsche is perfect, but one of them will be perfect for you". Maybe that could have come into it somehow? At least Porsche has something that makes it easy to recognise. What would we do if we were asked to build, say, a VW? Link a smoke machine to the rear wheels :P?

LEGO shop has given me a better experience than Bricklink, but maybe that's just me. Mistakes are always going to happen. I rebuild parts of every gearbox and suspension system at least 30 times before settling on the final design. Once, before I joined here, I made a truck with a gearbox where the MINDSTORMS shifting control needed tuning (working on an upgraded version of that gearbox for a future model) since the shift positions were non-definite and had to be found through trial and error. To make things worse, parts were flexing under load and I had to make the shift position change slightly depending on load handled. That took many sweaty, expletive-filled hours, but it was worth it. I haven't been to many LEGO shops in the UK, but the LEGO store's prices seem on-par with LEGO.com, at least for sets. Bricklink will probably give you the best deal if you want a specific part, since few individual TECHNIC parts are available on LEGO.com.

Perhaps they should do a digital-only contest where you have to submit the original LDD file and the judges actually BUILD everyone's entry... But that would be very wishful thinking.

Impressive, and incredibly fast!