DrJB

Eurobricks Dukes
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About DrJB

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  1. What! (Mods remove after)

    87 emails here ... darn. Need to c*str*t* the S*B!
  2. I guess it was novel to me ... I'm aware of the one using the large hailfire wheels with soccer balls (Sariel uses it in many of his videos) or wheels (below), but it's the first time I see the BWE's curved racks used that way.
  3. Impressive!!! This IS worthy to be front-paged. I like your 'novel' large turntable idea (with the small roller-bearings) and I'm sure once we see the assembly 'moving' we'll get even more appreciation to the inner workings and intricate mechanisms, and even more questions about how you accomplished specific functions. Excellent Job! Question 1: In real life, the up/down motion of the arms is accomplished by hydraulic cylinders. Did you use LA, pneumatics, or something else? IMHO, some pneumatics with 'sequencing' would be a neat add-on, though maybe a bit difficult to house. Question 2: From the kinematics (your 1st video), it seems each rider-seat has 4 degrees of freedom: rotation of the arm about vertical axis, lifting of the arm up/down, rotation of the 4x2 seats, and then rotation of the seats about their center. I'm sure somehow all seat are connected in 'parallel' and there are a total of 4 motors (or DOFs) for the whole assembly. Now, how many motors are you using and how many independent controls over the 4 DOFs ?
  4. While I agree with many of the OP's points, this is bound to be a bit of a 'sensitive' discussion as we might get some forum members a bit offended. Yes, I've gotten to a point where I simply 'ignore' many posts (I get an email with every new thread) as after a while, one gets numb to all the 'basic' questions and sub-par MOCs. My approach here is: well, I started there myself sometime back as well and there should be a way to encourage new-comers. If you list all the threads that have 'Ferrari' or 'Lamborghini' in their title, some are worthy of a frontpage, others are, well, ... no need to offend anyone :). Maybe the way to address this is to split the forum further into sub-levels but then it becomes tricky to navigate, and we might miss important/interesting threads/discussions. My 0.02 worth
  5. While it appears (on the outside) that there is no room for gearing ... it does in fact have have a planetary single-stage gear reduction.
  6. I remember this discussion ... it was about the time where most of us were getting 'tired' of vehicles with wheels, and wanted to see something different. Yes, would definitely appreciate seeing the progress you've made and how you solved the mechanical 'challenges'. For rotating the seats, maybe flex axles like those used in the ZNAP line could be helpful, as they bend 'easily' and can go through the arms.
  7. A while back I was into salt-water fish-tanks and yes, finding someone who can feed your fish 'reliably' was always a pain. I like what you've done, but am no longer into that hobby as it does require a lot of time. Feeding is only part of the story, then you need to do regular water changes and add chemicals to 'regulate' the tank's chemistry. In that regards, any bit of 'automation' (as you've done) is a very welcome initiative.
  8. Nicely done. The main issue with these (I think) is the excessive slack from all the links. Conceptually though, this is nice and as you've shown requires a wheel with enough clearance to house all the parts. Have you calculated what the 'scrub radius' is? It is the distance between the center of the tire's footprint and where the pivot axis intersects the ground. In real life, such scrub radius affects many performances of the vehicle, primarily handling and tire wear.
  9. Up until few years back, every technic set had a large collection of 'colored' parts (connectors, flex axles, liftarms, ...). Recently however, most of the vehicles' interior/chassis is typically made up of only monochromatic (black/grey/white) parts and then, a minimum of parts (primarily for styling) are truly 'colored'. There was a time where I 'lamented' as to the lack of colors in Technic as all the SuperCars were issued either in red or black. Back then, the overwhelming answer was the lack of available 'other' colors. Now it seems we're migrating back to 'rare' colors and small number of colored parts for styling ... and yet purely monochromatic parts for the Chassis. This is somewhat the case for many StarWars set as the grey is meant to 'mimic' steel and metallic structures. What are your thoughts on this and how has this affected your 'MOCing' options ? Oh Yes, miss seeing an official Technic Car in RED ... the last we've seen is 8070, and then 'smaller' attempts since then, as in the customizable truck and the fire truck. The latter though has more grey than red.
  10. What would happen to all the FLL programs (worldwide) that use MindStorms as an introductory 'Robotics' course? As many might recall, Mindstorms started out from a robotics course at MIT 6.270 (late 80's) and then the first brick (RCX) was developed jointly by MIT and TLG. Many schools (Highschools and Universities) have then adopted the format and started offering introductory courses. If MindStorms is to go away ... many schools would need to 'scramble' for new content.
  11. There are multiple good sources on 17 groups on the web. The one I thought was most 'enjoyable' to read/study is an app (iOS/Android) called iOrnament. I got the screenshot below from it. It explains in a very compact form what the 17 groups are ... For example, the first square is a pure translation along 2 axes. The second is a translation plus a rotation. The third is a mirror reflection ...
  12. Agree, need a bit more clarity here ... You're right. Intuitively it makes sense. I was thinking of it initially from a mathematical standpoint, and was not sure a rotation matrix can 'always' be written as the product of two reflections matrices. It might very well be that the solution could at times be not unique. When I mentioned 'commutativity', I has in mind full rotation in 3D space, and there, for sure the rotations do NOT commute i.e., rotation about x then y axes is NOT the same as rotation about y then x. Thinking of rotation matrices again, if we change the order of matrix multiplication, we get a totally different result. Now, all of this is true in 3D space (and beyond if we're comfortable with that). In 2D space, there is only one axis of rotation (Z, normal to the 2D plane). There, when a rigid body is subjected to two rotations, they are both about the same axis, and as such, they do ADD. In 'my' terminology, one cannot speak about commuting rotations in 2D ... again, pure terminology. PS. Thanks for a trip back in time ... This reminds me of a graduate course in Dynamics many years ago, and of all the subjects, 3D dynamics is often NOT intuitive ... especially when you include gyroscopic effects. That's not fair ... what am I going to do with all the parts I ordered from BrickLink? :(
  13. The other option, which I find rather slick, is to use a gimbal-stabilized camera. I got the DJI osmo recently and rather pleased with the 'stability' of movies it produces. Careful though, as the 4k videos it produces won't run on just any PC/laptop. Now, if you're into building your own little camera (forget zoom and other features), you can try a Raspberry PI with a Camera Module. Be prepared to invest some serious time programming, to get it to do exactly what you're after. Again, both options (Raspberry Pi and Osmo) have no mechanical zoom/Tele capability.
  14. now you lost me ... '77 ?? ah ... the year the first Technic models came out? My dad bought me the red tractor and yellow forklift.
  15. lol ... no objection there :) I was merely referring to the build style.