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About Attika

  • Birthday 03/08/1977

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  1. Thanks for the video. It certainly sounds like the buwizzes are overloaded. For a start I'd experiment by changing gear ratios to make it slower. In case it solves the problem, there is your answer. 2 kg is quite a weight for the current gear ratios.
  2. Yes we do. Surely less than in a bad design, and just slightly more than the theoritically best possible. Don't let the perfect be the enemy of the good. On this specimen the suspension travel is limited if the steering is in that extreme position if I'm not mistaken, the link slips under the frame and two will collide . I do understand it is a "mockup", but I find that being a very convenient excuse after such a harsh criticism in your first reply on the topic. Steering only? You really want us to beg to see it running around in your kitchen?
  3. Looks brutal indeed. Would be nice to see in action, that says more than a hundred words. On the subject of steering geometry, I did not see any problem, in fact it was a clever solution on ackerman geometry, but I had the benefit of the doubt as I'm geting rusty. Looked it up and it's almost identical setup as the Greyhound had, made by @Didumos69. Now as much as I remember, when it comes to geometry, he knows his way around that subject, so I respectfully disagree with @romashkaman. (apart from the position of the kingpin, but that is on the choice of the built hubs)
  4. It is plastic only on the end of the day, so you may rightly expect some wear. with safe design, it canbe reduced though. Appears as withe powder around axles rotating in the holes of beams or frames. I go with silicone based lubricant. Namely WD-40 has a silicone spray that used to use. Didn't experience any negative consequence yet, although I'd use the verb "reduce" instead of "eliminate". Got to accept that every magic comes with a price. :-) It is sand you wanna keep those cv's away from. No lubricant can help against that.
  5. Amazing build, hats off, really, regardless of any steering questions. :-) I've never took the challenge to build alternate models due to the limitation on parts. There is enough compromise to make in a building process, could not handle a self inflicted one. :-D Considering that, I feel like the way you've designed the (1st) steering mechanism is ok. Although @Igor1 is making a valid theoretical point on the geometry (and hereby I'm thankful for him, carrying this flag in my absence) I'm more apologetic in this case for a few reasons: - Limited part usage (as mentioned above) -On the video it did not come accross as bad as I've expected. In fact I hardly even noticed the problem. (I've read the topic first, then went for the video) Might be due to the freeplay of the frictionless pins are counteracting and the steering lock is also modest. -Without differentials.... :-) a small anomaly in the geometry doesn't even tickle my nerves (don't get it wrong, I totally agree with the no diff policy, you've applied) - and finally, probably you did something here what is sort of common in similar designs. I've came across some rc rock crawlers explicitly using the same, inverted ackermann setting, yet I can't tell if it is some clever stuff or budget cut on the engineers desk, so I leave it for someone who has a grasp on this question. I'm closing with a few words on the jerkiness of the new cv's in the 2nd design. My bet is on the lack of the differential. In this setup the rotation difference between the two front wheels is high enough to make one of them skid in the corner, this could manifest as a periodic hop of the given wheel. I think that can be confused with the cv's limit, but I doubt the latter. If you can test it by making the 2 wheels independent from each other for an experiment... I didn't have this problem in models with diffs. Anyhow, it is up to personal taste I suppose, when it comes to smooth rollin', but I can assure you, it takes way more to damage the cv or the hub. As a reference, I offer my video, titled "wannabe tatra" to your attention, with the sidenote, that those hubs and cv's are still fully operational. As a rule of tumb, 45 degrees doesn't hurt them. 1200 rpm in the other hand does ;-) if lube not applied Great job again
  6. Confess, you heretic! That tyre of yours has an unnatural belly. It is forced to a slightly bigger rim than it supposed to be. Now I know I'm the last one who should comlain about that (I've got a past ) but that printed rim isn't the same size as the lego counterpart, is it?
  7. The inner diameter of this rim is less than 5 studs, so an offset rim could not take the hub.
  8. Hi, I'm glad you appreciate my brainf4rt. Sorry for not reacting back then when you posted the G-wagon. I had the look, I just didn't react. My bad. It is my pleasure. wow, hold your horses! You're going to regret this question, I promise. Sooo, diff lock on the front is virtually imposible at the given width of the axle. Because of the steering, the hubs need to be held by the ball joints. That is only possible by using the 5L ball socket ended steering arm which is going to collide with the differential if -like at the rear axle- the 7x11 frame is being used to brace the mechanics. Even if this problem would go away, there is not enough room beside the 7x11 frame to connect any steering rod to the hub. My opinion is that by keeping the original dimensions of the axle, it cannot be done (properly, at least). I've scheduled to rebuild the whole chassis, using the bigger tyres and conveniently use the defender rims. That offset rim gives me another 2 studs on width and beside I'll give an additional 2 studs to compensate for the tyre size and make sure it does not rub against the chassis when the steering is at full lock. That seems to be quite manageable (says my Dunning kruger). Up to the news: Today I woke up and made the front axle even shorter by a stud. (If I had a month probably I could make it disappear as a whole ) That's how it looks: Also some hastily made instructions: Some additional changes I made on the front of the chassis: 1. Eliminated the panhard rod, changed the 3L axles with stop to 4L ones and by sticking them from the outside, could connect the two sides with that red connector assembly. It stiffened up the whole structure making the panhard rod redundant in it's function. 2. changes the springs to soft ones (all 4 of them) it lets the axles flex way more than the hard ones. The front end therefore is "floating", siting in a bit more than half on the suspension travel length. I'm happier with it this way, but it is mainly a personal preference. Do as you like. 3. Lifted the panel on the bumper by one stud (by taking out a 9L beam). It meant to compensate for the slightly lower stance caused by the softer springs. That's it. Have a good time with the set guys, I go back to my cave now. Bye Please keep in mind: This is my take on the subject, made in a very limited time window. The design may contain some solutions which satisfy my taste, yet can disturb others. Time and users (preferably @Didumos69) will tell if it is good enough or not.
  9. So, I had a go on this problem and in advance I have to say it is a compound problem, hence it requires some dissection. 1. The designer states in his related video that the steering lock is limited to about 30 degrees to protect the cv joints. I -respectfully- tend to disagree. Personally I've found the best point of these joints at their debut is the max working angle is around 40 (+) degrees. Since then I've built them in many application and never came across any problem in this regard. 2. In the same video the ackermann geometry is mentioned to be used to improve the steering lock. Sadly it does not do the job, here is why: - The angles are not correct. If the wheelbase was the half of what it is, the designed angles would be moreless accurate, but at the current distance between the axles the given angles are too high. Having this kind of excessive ackermann geometry is even worse for the the steering lock as having no ackermann built in the design. Why is it worse? - If the maximum angle for the cv is given, it means -with ackermann steering- that the inner wheel takes that maximum angle. The angle of the outer wheel is going to be lower by defenition. So we've got 30 degrees inside and 26(ish) outside. Due to the reason that these angles don't line up with the wheelbase, it means, one of the front wheels going to skid sideways when cornering. Usually it is the inside wheel with the higher angle that is skidding, so our practical steering angle is down to 26(ish) what is represented by the outside wheel. The rest of the problem is in the code. Using the PU profile (first time I did btw) there is a callibration process to go through. At this the motor takes both endpoints and settles at the middle point. When it comes to playtime however the maximum angle is lower, I assume it is to protect the components. Nevertheless it also decreases the steering angle. And now to the good news: To be honest I forgot to measure the original turning circle but I had two sources to get data. The designer states it is 195cm and @Sariel's gadget displays something over 2 metres (would have been useful if you show us the method instead of playing with the cat) Anyhow, I've rebuilt the front axle taking out the ackermann design from the equasion and connecting the steering rods one stud closer to the hub pivots (basically where it supposed to be by default). This gave me about 20-30 cm decrase on the diameter of the turning circle. A bigger chunk has been chopped of from this number by using the BrickController2 app made by @imurvai (God bless him). This method of control doesn't apply safety measures, it just does what you want. The end result is 90cm diameter between the inside wheels (130cm between the outside ones) A humble demonstration: I'll make a file soon and link it here.
  10. Hello there good people of Eurobricks, haven't been around for a while, as I've moved country and turned my life upside down. Anyhow, thanks to @kbalage I had the pleasure to peek into this upcoming model and share some workshop hours on the forementioned problem. Upon the quick fix I've felt the urge to make a deep fix, just as my noble colleague @efferman did. Here is my take on it: Made some sloppy building instructions too, please find in the link below: I've the pleasure to report that it's been tested IRL and have passed it. (yes, straight against the wall, that's the way it is ) Link for file:
  11. I haven't been around for a while, yet I came back just in time to see something incredible. Such a density of perfection. Kudos
  12. Very interesting concept on every level. Drivetrain, suspension, both quite unique solutions (at least for my eyes) and the bodywork makes it pretty. I'd love to see it on video.
  13. Looks nice, drives nice, solid job again, congrats. I perfectly understand the way of your thinking. My first build with the new hubs was also a tatra with buggy motors. It is mini compare to mine at least. Besides, building a driven tatra suspension in this scale is more of a challenge than using solid axles. (I suppose)