Ngoc Nguyen Posted September 3, 2024 Author Posted September 3, 2024 Another nice thing about the steering shift that I forgot to mention is that it locks itself. You can't switch mode if the HOG is turning or the wheels are steering. The reason is very simple. Since the HOG shaft (which controls the grey knob gear) and the rear steer shaft (which controls the yellow knob gear) are always parallel, once you turn then when the steering shift is in the back position, the arm/tooth of the knob gears will slightly overlap, and the yellow gear will block the steering shift from moving completely into the front position and subsequently meshing with the yellow knob. Quote
Ngoc Nguyen Posted November 23, 2024 Author Posted November 23, 2024 Even though I want to be done with this MOC, I'm still not quite satisfied with one thing, so I want to go back to fix it. This is the part where I need help from fellow crane operators, crane engineers, or structural engineer. The problem is that the superstructure tilts noticeably towards the front. The photo below is just a render so there's no tilt but it helps visualizing the problem. In the real model the superstructure tilts towards the right side. I'm not sure if a tilt like that is actually a problem, but I don't see the same thing in the crane 42108 and 42082, so I think something is wrong. I thought the problem was the counterweight, so I designed a new one that is twice as tall as the old one. However, the tilt still appears. I tried extending it further to the back, but it was not until I put something 6 studs further from the current counterweight that the superstructure appears balanced. I don't want a counterweight that extends far behind the rear of the chassis as it looks ugly. The boom isn't very heavy, and although I haven't weighed it, it's shorter and not much thicker than the boom in 42108, but the superstructure in 42108 doesn't suffer from tilting. Therefore I think it's a structural problem, and since I'm not well versed in structural engineering I don't know how to fix this. Any idea? Quote
Timewhatistime Posted November 23, 2024 Posted November 23, 2024 Maybe there is too much play in the turntable, i.e. both turntable-parts are not connected as firmly as they do when they are new and not worn down? A certain amount of play is immanent; that's the reason why e.g. 8043 has supports on the load side. Quote
Ngoc Nguyen Posted November 23, 2024 Author Posted November 23, 2024 12 minutes ago, Timewhatistime said: Maybe there is too much play in the turntable, i.e. both turntable-parts are not connected as firmly as they do when they are new and not worn down? A certain amount of play is immanent; that's the reason why e.g. 8043 has supports on the load side. I don't think it's because of the turntable, because when I remove the boom, the remaining chunk (gearbox and cabin) becomes horizontal. I don't get what you mean by 8043 having supports on the load side, can you show photo? Quote
Timewhatistime Posted November 23, 2024 Posted November 23, 2024 (edited) The supports are two 9L beams in dbg which are mounted vertically. See building instruction steps 57 and 58. These supports transfer pressure from the upper structure onto the lower structure; so they take some stress from the turntable and prevent tilting of the upper structure. 16 hours ago, Ngoc Nguyen said: I don't think it's because of the turntable, because when I remove the boom, the remaining chunk (gearbox and cabin) becomes horizontal. This observation fits very well with my hypothesis: By removing the boom, you take away the stress on the turntable. So the whole system gets back in horizontal position (more or less, depending on the turntable's play) Edited November 24, 2024 by Timewhatistime Quote
Ngoc Nguyen Posted January 14 Author Posted January 14 How the two mode steering and the steering shift works: Quote
Ngoc Nguyen Posted January 16 Author Posted January 16 As explained above, this MOC is considered done, but the quest for perfection makes me feel restless when the superstructure tilt exists. Thanks to the consultation of Milan, who has extensive experience with cranes, I had to redesign the turntable. The main reason is that the supercarriage only rests on a turntable which has a lot of slack. The superstructure design is also not optimized in two ways: the connection point with the boom is not placed far enough to the back, and the counterweight can be made bigger. As you can see be low, the connection point, which is where the yellow axle is, is rather close to the center. This creates another problem, which is that it takes a lot of force to lift the boom. Therefore, for the superstructure, I made the counterweight thicker, and moved the connection point 4 studs back. That's the furthest that it can be moved. Since the new position decreases the maximum angle of the boom, I replace the medium LA with the large LA. I also fortifed the area at the front of the superstructure, under the large LA (the black 3L connector). That is where the superstructure will lean on. A slight downside is that the boom can't rest in a position parallel with the body anymore, but that hardly matters. The fact that the boom is at a slight angle can be explained to allow the operator to see the mirror on the other side, even. For the undercarriage, I used the gear rack quarter from the set 42160 to form a ring that the superstructure can rest on. This means I had to replace the big turntable with the small turntable, and rework the gearing that drives it. The result is that the model looks better now, and doesn't show as much tilt as before. It also requires less force to raise it. I had to redo all the renders and the function sheets, and that's a huge chore, but I have to do it since the design has changed considerably. At least I can find comfort in the fact that this model has reached the best form that it can be, and I can finally feel at ease. Quote
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