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Everything posted by Hrafn
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Thoughts on the new wheels/tires in the UCS Batman Tumbler
Hrafn replied to Paul Boratko's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
Unreal. I had no idea people were that crazy for minifigs. 2kg of black bricks + 2 new (but very wide) tires + 2 3x11 black panels + 4 Unimog tires + no functionality does not equal $200 of value for me, not by a long shot. Even selling the figures off for $50 each wouldn't make it worthwhile, IMO. I'm very puzzled why Lego didn't at least add steering. AFOLs have shown it can be done well at smaller scales than this. -
7-Wide axle with centre-point and Ackermann steering
Hrafn replied to Junpei's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
Thank you for sharing this, it's quite ingenious. -
[HELP] Large scale suspension
Hrafn replied to z3_2drive's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
Do you mean the 10.2mm diameter ball joints ()? I've used those in some suspension experiments and found two things. First, the standalone ball joints are no good because they pull off the axle when subjected to any tensile load; it's better to use 50923 or 64276 . Second, the ball joint sockets (like this one ) have too much friction to be used in suspensions (except maybe for very large, very heavy vehicles); fortunately the balls also fit nicely between two liftarms spaced 8mm (1 stud) apart, and in that configuration the ball joint can move smoothly.- 9 replies
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[HELP] Large scale suspension
Hrafn replied to z3_2drive's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
What scale, and what wheel size, are you looking at using? Vehicles under about 1:10 scale (or with wheels smaller than the 62.4x20 ones) tend to be too small for advanced suspension geometries, custom kingpins, etc.- 9 replies
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Sisu SA-150 aka "Masi"
Hrafn replied to Zantza's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
Welcome to Eurobricks, and this is a great truck. The ground clearance is impressive - I'd love to see it in action.- 9 replies
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- Finland
- Army Truck
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Axle Collection Thread
Hrafn replied to efferman's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
I like it! Nice and compact. I assume you get some bump steer since the steering links aren't the same length as the suspension arms, but it's probably not much of an issue. How did you connect the steering axle to the sliding steering "rack"? -
[WIP] Lancia Stratos
Hrafn replied to piterx's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
That back is gorgeous! I was excited that you were tackling this project but worried that it wouldn't work out since the Stratos has such a complex shape, but this is outstanding. -
When building trucks (pickups, trial trucks, etc.) that have motorized winches, do you use a dedicated motor for the winch, or use a distribution transmission from the main drive motors? A dedicated motor would be simpler, but then you'd need a separate channel for it and the motor would be dead weight when you weren't using the winch. Using the drive motors would allow re-use of the (presumably powerful) drive motors, and with a differential you could have the motors drive the vehicle forward as they also pulled the winch in - which seems useful when using the winch to self-extract the truck. On the other hand, a distribution transmission would add additional complexity. Specifically, I was thinking of (at some point) building a part-time 4x4 pickup with a winch on the front, which would have the following modes of operation: FWD high 4x4 low winch retraction (with the drive wheels in forward or neutral, for self-extraction; or the wheels locked by a brake, in order to use the winch to pull another vehicle) winch extension (by hand, using a ratchet or something similar to avoid having to back-drive the winch motor) I would probably use 2 XL motors and would lean towards using a distribution transmission for the winch. What do you think?
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[WIP] Lancia Stratos
Hrafn replied to piterx's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
This thing is a beast! I'm impressed with how well you've packed the motors, batteries, and steering in there. Looking forward to seeing your continued progress! How are you going to do all the curves in the bodywork? Flex axles, or liftarms, or brick-built? -
Help me choosing
Hrafn replied to piterx's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
I know you already decided, but as Benny might say, Stratos, STRATOS, STRATOS!!!! The bodywork will be very, very hard though. When I did my 037 I originally thought about doing the Stratos instead and concluded the bodywork was beyond my abilities - but I think you could do it! White with the Alitalia colors would be awesome, but probably a bridge too far - you'd need green and white parts, and all the diagonal lines would be very hard. -
Tile, Modified 1x2 with Ball - usable with A-arms?
Hrafn replied to Hrafn's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
I didn't even think to check the ball's radius, thank you! Yeah, it appears to be larger than the towball that fits with the suspension arms. Oh well. -
Lego motors, speed and physics question
Hrafn replied to aol000xw's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
In principle, there are two factors to consider initially, both of which relate to getting maximum power out of your creation. First, the Lego batteries have thermal protection circuits that kick in at a given point, so there's a certain current level you don't want to exceed if you want to have your motors run for more than a few seconds. According to Philo, the 5292 motor can reach its maximum power at 1.4 Amps, if I recall correctly - but (for example) the rechargeable battery pack will shut off if you draw more than 1 A. 2 5292s powered by 3 LiPo batteries would probably give the best power to weight ratio while using about all of the available current, though you'd have to do some funny things with the wiring (PF to 9V, then use a small (PF-M or mini-motor) to control a switch that fed the 9V to the motors.) Second, any electric motor reaches maximum power at 1/2 of maximum torque and 1/2 of maximum speed. The main equations to keep in mind - which you may already know - are these. For motors: P = ω * T (ω is rotational rate, in rotations per second; T is torque, in Newton-meters; P is power, in Watts) ω = ω_max - (ω_max/T_max)*T for electric motors - in other words, there's a linear tradeoff between speed and torque P_max = ω_max/2 * T_max/2 (restating point 2, above; this might not be obvious but is derived from the first two equations) For wheels: v = ω * r (v is velocity in meters per second, r is wheel radius in meters) For batteries: P = V * I (V is voltage in Volts, I is current in Amps; fresh non-rechargeable batteries give 9V, rechargeable ones give ~7.2V, and the LiPo gives ~7.4V) As DrJB said, though, friction is important, tough to calculate in practice, and even harder to predict ahead of time. Probably the best thing to do is just observe best practices - keep your structure light and very rigid, keep axles short (and use axle joiners for longer ones, since they're more rigid), limit the number of gears you use, and use firm tires on flat, smooth, hard ground. Build a vehicle with no gearing, measure its speed, and calculate what the motor's rotational speed must be. If it's not close to half the theoretical maximum rotational speed for the motor, adjust the gearing and try again. -
[MINI] Stratosphere Fair Ride
Hrafn replied to W3ird_N3rd's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
That's a nice little MOC! It's nice to see things other than cars and construction machinery (though I love those too). No matter how many parts I have, I always find myself thinking I don't have enough - but this model points out how having to operate on a lean "parts budget" can really be a spur to creativity. -
[MOC] Galloping Horse
Hrafn replied to touthomme's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
This is really amazing! What is the part that you used for the hooves? Would there be any way (a linkage or a couple of rubber bands, maybe) of making the hooves move a bit, or do they have to be fixed relative to the end of the legs? -
[MINI] D3K's WIP topic
Hrafn replied to D3K's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
Beautiful! This is better than most official sets, especially considering how few parts it uses. I like the new tailgate, too. -
[MINI] Electric mining shovel
Hrafn replied to Tommy Styrvoky's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
This is a great idea and I like the execution! A bit more color would make it pop more visually, though. What about the bright red cab design of the steam shovel in the classic children's book "Mike Mulligan and his Steam Shovel"? -
Transfer Case: 2 Hi to 4 low.
Hrafn replied to sdotcarter's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
Yeah, I realized that right after posting it. There are ways of dealing with that issue (ratchet clutch, second driving ring disengaging the front prop shaft, etc.) but then the design is no longer more compact than the original. -
Transfer Case: 2 Hi to 4 low.
Hrafn replied to sdotcarter's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
I just realized one way to make aeh5040's design more compact while also adding the ability to lock the differential while in 4x4 mode. The differential case should be driven. When the driving ring is to the left, it's 2WD high mode; in the center, 4WD low with an open diff; and to the right, 4WD with a locked diff. -
Uses for "useless" Technic parts?
Hrafn posted a topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
I'm curious if anyone has found good uses for any of these parts. They're listed as being Technic parts in BrickLink, but most of them seem to me to be marginally useful at best. Are there other Technic parts that you find useless? -
Uses for "useless" Technic parts?
Hrafn replied to Hrafn's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
I saw them used once as landing gear for a Millennium Falcon-like spaceship. But yeah, a Technic use (other than the intended one of storing rubber bands, which they work decently for) is hard to imagine. -
Uses for "useless" Technic parts?
Hrafn replied to Hrafn's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
It's a pity they're so large. The one on the right would be great for using with a 40t gear, but the partial 24t gear attached to it is awkward. Aha! That's very good to know, thank you. That could be a useful combination. Also good to know! I'd noticed the groove on the back of that part before but never realized it would interface with a rail. Indeed! This part seems pretty hopeless though. -
Pin, axel, - color - retoric question
Hrafn replied to AOW's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
Also, while the blue 3L pin has friction, the tan 3L pin does not. -
Small front independent suspension with drive
Hrafn replied to gsia17's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
One question - have you considered using instead of , and using a 20t single-bevel gear to drive the axle? That way you could get the center of the U-joint lined up with prop shaft axle, and both half-shafts would be of equal length. EDIT: it wouldn't quite line up, but it would get you 1/2 a stud closer to lining up.- 22 replies
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- suspension
- small size
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Changing Color of Technic Parts
Hrafn replied to __________________________'s topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
People have used vinyl dye (here and here). Some people have apparently also used RIT dye, though others swear it doesn't work. That said, vinyl is highly toxic (carcinogenic, among other things) and RIT isn't exactly good for you either.
