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About allanp

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    Lego (obviously), writing/recording/performing music, computer graphics/3D modeling, amature movie making (more FX the better!), precious few aspects of my job as as a mechanical/electrical engineer.


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  1. allanp

    42113 Bell Boeing V-22 Osprey

    I like that the rotors appear to spin quite fast.
  2. The "dumb" hub reminds me of how the battery box and switches were set up in the space shuttle 8480.
  3. allanp

    Technic Model Comparison

    You missed out the best Volvo
  4. allanp

    Technic 2020 Set Discussion

    I think a lot of that is that studfull just seems a lot easier to work with than studless, at least there is less of a learning curve at the cost of being somewhat limited compared to more advanced studless, and a skeletal studfull design can look great whilst a skeletal studless design looks kinda crap! Of course, studded Technic bricks and plates are still in production. So really, is there anything stopping them releasing brand new, studded universal sets? These would be sets that are designed to bridge the gap between regular Lego and Technic sets, have mechanical interest (not necessarily realism) as the main focus, have instructions for multiple models (there's no real A-model as such) and being studded easy to make MOCs from for children. It could even be its own sub-theme, with one set per year, called Technic Universal or Technic Multi-model.
  5. allanp

    Technic 2020 Set Discussion

    The best B-models are where they are of something completely different from the A-model, like a marble machine/GBC. Speaking of which, does anyone know if objects can be fed into the other end of the drum?
  6. allanp

    Technic 2020 Set Discussion

    I think universal sets were even better at doing that. 8064 had instructions for 4 models plus more models and ideas on the back of the box for inspiration. I remember building all of them and some extra MOCs from that set. The old ungeared motor was a lot of fun to play around with.
  7. The practical gearbox could be much smaller, as in shorter, but we can't make it anyway because the parts don't exist. That was a non functional mock up to show the idea. As for your Sian, it would be a shame if it didn't work the way you want it. If you don't fancy rebuilding the whole thing again while checking all the axles for straightness (which may or may not work) why not try a drop of lubrication? Just remember to clean your parts once you disassemble it before putting the parts away as a tiny amount of lube will cover everything! And use a plastic/rubber tyre safe lubricant like silicone (NOT WD40!)
  8. Without having the gearbox in my possession it's hard to be sure but I think you are right, and @Filthy Fox it makes sense now for 7th (which I think is actually second gear) to be the gear in which it locks up. In (what I assume is) 2nd gear the upper blue 20t gear is engaged with the drive ring. This tries to turn its mated 16t grey gear slightly faster which then sends it's torque through a winding path down through the idler gear arrowed by @Didumos69, which is a gear that is also transmitting torque. In 4th gear (which also follows a similar torque path through that gear) the ratio is slower, requiring less torque to turn, so it doesn't quite lock up. In 1st and 3rd the power is not being transmitted by that gear and in gear 5-8 the torque requirement is less due to the lower ratio of the second 2 speed/4 position gearbox. A good way to check would be to turn the car on it's side and lock the gearbox in the trouble gear by turning the wheels. Then while locked try to fiddle with that one gear side to side and see in it moves a little. Many people might not have this problem, but we are so close to the edge of being barely functional due to these over-complex designs that any barely noticeable manufacturing flaw can cause this to happen. I noticed when a lot of people were having problems with the 42009 outriggers barely moving that some axles straight out of the box were ever so slightly bent. So I built an axle tester by placing a bunch of 1x2 Technic bricks next to each other on a 2x8 brick. Half the axles fell straight through but many of then fell slowly and many didn't fall through at all. After building 42009 using my tester on every axle the outriggers worked as well as I've seen in any video (not great, but they worked). Tiny imperfections like this caused some people to have the issue, and some people not to. @Filthy Fox As for gears only locking up in one direction of rotation, I'm pretty sure it's to do with the way gears react to each other when torque is transmitted through them. Remember every action has an equal and opposite reaction? Well take another look at the example gearbox: On gear 2, which is the problem gear, there are 2 forces that we need to consider (there are other forces n other directions but fully drawing up the vector diagrams is not important to this). The first force is the force that tries to push gears 2 and 3 apart whenever two gears are transmitting power. It's the force that requires us to brace gears to prevent them coming apart under high loads. In this example this force between gear 2 and 3 is always pushing gear 2 to the upper right of the screen, and this never changes. The second force being applied to gear 2 that is relevant to this issue is that which is applied by gear 1. Not only is gear 1 trying to push gear 2 upwards, but it will also be exerting an even greater force left or right (this is what causes gear 2 to turn after all), and the direction in which that happens will depend on which way gear one is turning. So in one direction of rotation the two forces somewhat work against each other, so gear 2 doesn't want to move anywhere. In fact, if you was to remove the axle on which gear 2 is riding on it probably would stay there transmitting power for a second or two. However, if you then turn gear one in the opposite direction the two forces are now acting in the same direction and are therefore added together, in this example trying to push gear 2 to the upper right of the screen. This increases the friction on the axle on which it rotates. This is why lockups are often dependant on direction of rotation, because in one direction the forces kinda cancel out, when in the other direction the forces add together. Without owning the Sian I can't say for sure but I highly suspect the same is happening in there.
  9. This is a tricky issue that I have come across in many gearbox designs. I too couldn't find any literature on it and it took a while to figure out. The problem really is too many idler gears transmitting torque on too many axles, which is a problem that is inherent to the appalling design of Lego gearboxes. I understand the problem but it's kinda hard to fully explain. Lets say we are using the gearbox in the above image in a manual model. When in 1st gear the torque generated by the wheels when you push the model forwards comes in to gear 1, is transferred up to gear 2 and so on till we get to gear 7 which drives the engine. Because Technic has no proper bearings friction can be a real issue in their inefficiently designed gearboxes. Even though this is a fairly simple example of a 6 speed gearbox by Technic standards, the path of torque still has to pass through 6 gears rotating on 4 axles, where as a real life gearbox would only have 2 gears on 2 axles. This is the main issue however, in many cases the gearbox doesn't lock up completely and can still be forced to rotate and most people won't notice how hideously inefficient TLGs gearboxes are, until the Sian breaks an 8t gear of course! However, in many cases where people want to design their own gearboxes they run into the problem of the gearbox locking up completely. In the case of this gearbox example it locks up in first because of gear 2 (that's the gear with the number 2 on it, not second gear), which is transmitting torque to gear 3, and is also spinning on an axle that is geared to spin faster, and it is also not meshed with a gear to it's right side when looking up at it from this angle. This is significant because when gear one rotates in a direction that pushes gear 2 towards gear 3, the equal and opposite reaction generated from gear 2 trying to drive gear 3 pushes them back apart, so those two forces somewhat cancel out and gear 2 will rotate on it's axle (though with a lot of friction). However if you rotate gear 1 in the other direction, such that gear 2 is being forced away from gear 3, now the two forces add up and create even more friction between gear 2 and it's axle. Now you have multiple points of friction adding up and in this case this gearbox will lock up. The friction has become so great that it is enough to stop it turning, and the more torque you apply to try to force the gears to turn, the more the friction increases, like a Chinese finger trap I suppose, or more accurately like trying to reverse drive a Technic worm gear. In real life you can indeed back drive worm gears, but with Lego you cannot simply because the slope angle of the worm is too shallow to overcome the friction of the sliding plastic. So this is why Technic gearboxes lock up. Too many shafts, too many gears and too much needless complication when they could just do it like a real car gearbox. These gearboxes ALL have way too much friction to the point where small oversights as described above cause it to lock up entirely. There are work arounds, like redesigning your gearbox to re-route the torque paths so that they avoid these problem areas in all gears in both directions, but this usually leads to even larger and even more convoluted gearboxes, and how a child is supposed to problem solve all that and then redesign it to come up with a solution I don't really know.
  10. Yeah, especially some of the old 5x4 9v ungeared motors as it's fun to build and watch all the gearing down needed for them.
  11. This really deserves to be on the EB front page
  12. The look and performance of this thing is incredible. Very well done
  13. allanp

    42107 - Ducati Panigale V4R

    As the back part is the part that eventually limits the travel then yes, in theory if you banged it hard enough the back could pop out. The way it's built into this model the top is enclosed by more Technic pieces so it can't pop out, but I might update my original comment to mention this.