Hrafn

If you attach the wheel to both the axle (going through the clutch gear) AND the turntable, what's the point of the clutch? In the setup you showed, I don't think you really have a LSD - if the wheels get stuck, the axles going through the clutch gears will just spin fruitlessly, with the torque going to each wheel limited to the slip torque of the clutch gear. That won't happen with Thirdwigg's design - most of the motor's torque will go to at least one wheel in his design no matter what happens, minus the slip torque of the clutch gear which will be transferred to the stuck wheel. If both wheels are stuck, they should both get half the motor's torque.

But then he'd no longer have a portal axle, if I'm understanding your idea correctly.

Looks like 44135. Along with 44136 it's one of the few Bionicle pieces that's reasonably useful for Technic.

Wow! You should open a new business: Zblj's Lego Towing Service.

It helps me understand what you did and why, yes, thank you. I had misunderstood what you meant by a 'floating' diff.

Ah, now I see what you did, that makes sense. The diff there isn't really floating, it has support on each side. I was trying to have a diff supported only by the u-joints on each side, which didn't work.

When I tried a floating 3L diff (leading to a u-joint and then a CV, and using 6L wishbones pivoting so they act like 5L ones) I had two problems. First, the diff would move away from the driving gear when the wheels were stuck. Second, that situation led to the diff teeth getting mashed. How did you avoid those issues, or are they not a problem with the 4L diff?

+1 for parts for narrow driven suspensions. The hangup here, besides there not being steering links shorter than 5L, is the length of the CV and u-joints. I'd like to see a 3L or 4L CV part with two 'male' ends. Then you could use one of those and two of per axle, have independent suspension, steering, AND fit in a differential in a narrow vehicle. Right now if you want to do an AWD car with diffs, the width of the components pushes you to 1:10 or larger.

With the hubless wheel post in the back of my mind and some 56x28 ZR Street tires on my table next to some old-style track links, something clicked in my head. 22 of the track links fit perfectly in the 56x28 tires. More interestingly, if you put 4L tiles or plates on alternating links, they also fit the inside of the Unimog tire. Of course you'll need more than 22 - probably between 40 and 50 - to fill the Unimog tire. The tracks can be driven by spur gears, so you could make a planetary reduction hub which could also be a portal hub. I don't plan to make any large trucks any time soon, but figured I'd post this in case it's useful to those who build trial trucks and other large vehicles.

Please do! There may be other tires it works on as well, with or without plates of various lengths. I tried all the tires I have and these were the two that worked, but there are many tires I don't have - like the green ones you used on your recent monster.

That's going to be huge! What scale are you working at?

I'd love to see this. Do you have a picture or something? I can't seem to find it on past forum posts Thanks!

Very nice! Are you going to take it outside? I'd love to see what it can do on uneven dirt and rocks.

Do the valves have to be in a particular orientation or spatial relationship to one another?

Very elegant! The module is quite compact when the legs are withdrawn. Will you be controlling the horizontal and vertical motions separately or will they be linked?

Yup. Something insect- or dinosaur-based might sell, though, especially in the smaller sets aimed at younger kids. Bugs and dinosaurs have eternal appeal, though maybe mostly to a younger age bracket than Technic is targeted towards now.

I'm with nicjasno on the wheels in particular. It's frustrating being unable to have wheels pivot around their center axis, or do other suspension systems (even MacPherson, let alone more complex things). I'd love to see a walking robot or dinosaur done with motors and PF, with the option to outfit it with Mindstorms. This could have a number of B-models to it continuing the theme (different kinds of dinosaurs, biped/quadriped/multiped robots) or even multiple sets. Maybe they could do a crossover with Town such as a harbor or railroad crane.

As a newbie, I've been somewhat disappointed by the performance of my half-finished MOC (a small 4x4 jeep-like vehicle, my first foray into studless building) and hoped to learn from more seasoned members' experiences. For those of you who've built motorized, 4-wheel vehicles, what factors do you find most affect the performance (probably meaning mostly acceleration, hill-climbing, and handling) of your MOCs? I'm specifically asking about the MOCs themselves, not the vehicles they're based on. Obviously, what factors are most important may vary between different vehicle types - from crawlers to race cars - so please note what kind(s) of vehicles you're writing about. In general, I would think that the power-to-weight ratio would be very important for acceleration and climbing, and center of gravity (meaning mostly the location of the battery boxes and motors) would be important for handling. To what extent do the details of suspension design matter for performance for each type of vehicle? How important is steering lock? Differentials? Ackerman steering? Suspension travel? Suspension hardness? Frame stiffness? Tire stiffness? Tire tread? And so on. Thanks!

Good to know, thanks!

I managed to break two 12t single-bevel gears in 3L differentials before concluding that trying to use them with an ungeared XL motor really was a bad idea. My question is, how much torque can those gears take (in the 3L differential) before breaking? It's clearly somewhat less than the maximum torque produced by the XL motor, since my gears broke when I was powering the motor with the 7V rechargeable battery and the dial on the battery was (I think) turned to just below the maximum setting. Will two L motors break the bevel gears? Both the official stats and Philo's site show the L motors as having just under half the torque of the XL (though they list different absolute values). On a related note, will the gears survive more torque in an old-style 4L differential when two half-bushes and a fourth bevel gear are added to reinforce them? Thanks!

Yes, that's one of the reasons I've been avoiding doing this. I was hoping someone would have a clearcut answer from their own experiences, so I wouldn't have to go the route of breaking more gears in the name of science. Very interesting! I'm surprised you say the 14t gears are strong, I thought they were phased out partly because they were weak. Or was it just because they didn't mesh well with anything else? I currently plan to use 56x28 wheels. The issue is speed and the lack of a straightaway in our apartment. It's a decent size (~1000 sq ft = 93 m^2) but broken up into a number of small rooms and strangely shaped hallways. I suspect a vehicle moving at any decent speed will quickly get out of IR range. Outdoors is not really an option right now - we live in New England and it's 12 F (-11 C) (in the middle of the day) and snowy! I haven't used the buggy motors yet, so I was making a very rough guess based on the published specs of their RPMs.

Thanks! All my remaining ones fit tightly on axles so they should be fine. And I should have two buggy motors arriving soon, so I can try those out - though they'll likely need to be geared down significantly for an indoor rally car.

Thanks, that's good to hear. Are there any visible tell-tale signs of a weak gear? Examining the rest of my 12t gears I don't see any obvious cracks or chips or anything. Are certain colors weaker? Both of the broken ones were light bluish gray.

This is why I shouldn't post on the net before having my morning coffee. I should have said geared 1:2 - geared so the axle spins faster but carries less torque to the differentials. I totally understand that you can gear up after motors, then down before the wheels, to spare the gear train (including diffs) from enduring too much torque. What I'm trying to figure out is *how much* I have to gear down to avoid fatal levels of torque; and right now I don't know what the fatal level of torque is for 12t single bevels. Hm, maybe some of my gears are older and weaker. It's hard to know since some came off of BrickLink. The drive train was very simple: motor to 20t to 3L differential, with the 20t and diff held in a 5x7 frame. The diff outputs went directly to wheels, with no suspension.

Yes, I did - it was a small vehicle with no room for gearing after the diff. More generally, though, I'm trying to figure out how much force the 12t gears can take; if they can survive 2 L motors ungeared then they can survive 4 L motors geared 2:1, and so on, right?