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Didumos69
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Everything posted by Didumos69
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I don't like the pinned topics at all. The list of pinned topics is simply too long. I browse this site on my phone and always need to scroll down several pages before I see what's going on. We could do with one or two pinned topics, with one of them providing a list of important other topics. And when there is a contest, just add one pinned topic, not three. As for hot topics, no need to pin them, because they'll be at the top of the normal topics anyway. -
Here's a little more info on the differential locks. The idea is to have a single lever for controlling two differential locks, one for each drive train. The whole setup works around the shifter-servo, which moved backwards by two studs to incorporate some down-gearing. Here are two cutaways showing the entire differential locking setup. Inbetween the two driving-rings you see the cam-pieces and half pin that together serve as a helper to keep the driving rings engaged. Btw, inside the differentials you also see the 1L beams that secure the bevel gears inside the differentials, as was suggested by @zux. So far they do an excellent job.
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I redesigned the structure and was also able to hold on to the differential locks. However, in the first make, the differential locks slipped under higher torque. The driving rings are pushed out of the clutch gears, even though I use the white connectors with ridges. The problem is that these ridges allow too much movement of the driving rings. So in the refactoring I also had to address that problem, and I found a solution. I built the idea in a separate assembly to check if it works, and it does. Here are two videos showing how I made sure the driving rings remain engaged better with less play. The biggest challenge was to make it such that it does not squeeze the driving rings against the clutch gears, which would cause friction. In other words, the auxiliary security - with two half pins and two cam-pieces as key players - should only reduce play, not eliminate play completely. The first video shows the difference with and without the extra security.
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And ?
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You can do that, but the thing is that when you would want to shift from 1st gear to R, you would need to shift the 4-speed back from 1st to 4th gear. So the gear ratio of R in the 2+R gearbox would have to compensate for that 4th gear to get close to the 1st gear ratio, while the third clutch gear you are suggesting, would be on the 5th to 8th output axle, which is the fast one used for 2nd gear in that gearbox. I also don't see a way to add a gear block preventing shifting further back from 4th to 3rd to 2nd to 1st gear in the 4-speed gearbox while the 2+R gearbox is in R. Hope this makes sense.
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We'll see, I have no clue where this is going to end. At least not when it comes to bodywork. At this stage I'm mostly focused on it's driving characteristics. And to that end I'm actually quite content already, but there is one thing that bothers me a little. When it rides at full power in 4th gear, it sometimes has a hard time shifting back to 3rd gear. Shifting gears actually requires quite some power from the servo motor in general. The fact that shifting is most reliable in ludicrous mode subscribes that fact. So I will try to gear down the servo, and see if that makes shifting 100% reliable. The idea is to drop the differential locks and move the servo 2 studs backwards. Two studs space should be enough to gear down the servo with two 12:20 gear meshes, which makes a 9:25 ratio altogether. I only need about 28 degrees rotation for a shift, the servo gives me 90 degree and by gearing it down I will have about 32 degrees. That leaves some space for play. I made a test setup, which works fine, see video below. Next step will be to redesign and rebuild the structure around the servo.
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I shot one more (bad quality, sorry for that) video to show the gear shifts. This also shows it's top-speed in ludicrous mode. I might try to gear it up a little by changing the gear ratio in the toggle joints close to the wheels to 1:1 (this now is 5:3). Btw, I think I will rename it from RC Off-roader to RC Allrounder.
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Thanks for the suggestion, I will take a look at those doors. I didn't lubricate anything this time. Maybe I will eventually. Btw, I had this kind of AWD diagonal test in mind when I started: And this seems to work out fine too. This has nothing to do with the differential lock (which is not engaged in the video below), it is simply because of the dual diagonal drive as explained in the OP.
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Thanks guys! A little more info. It currently ways 1600+gr and consists of 1400+ parts. The track width and wheelbase are exactly the same as my rugged supercar. I think it will be more like a Subaru XV/Crosstrek, however it will probably be a beam-based open body. I also think I will skip all interior details, just like with real RC models. I think the trick to avoid slipping gears in the differentials is 1) to have two separate drivetrains, so not all power flows through one differential and 2) to gear up instead of gear down , i.e. to have high spin / low torque in the gearboxes which include the differentials. I did skip the bad offset turn-table based wheelhubs. It also gives a better trackwidth. Here's a short video in daylight showing some details:
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Very interesting and some great achievements already. I like the symmetry between front and real axles. One question about the gearbox: What are the ratios of the 4-speed gearbox?
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During the holidays I finally had time to build. First results are actually quite pleasing. I had to make a few tweaks to make it buildable and I skipped the turn-table-based wheel hubs for now (I used normal LEGO hubs), but so far I didn't need to change anything to the gearing. Here you see it accelerating from 1st to 4th gear. No slipping gears sofar. EDIT: I did have to make one change: I changed the differential lock to lock the differentials individually, without linking them together. The drive trains are spinning in opposite direction to give correct input for the V8-differential. This doesn't allow them to be linked the way I had in mind. I don't see this as a big concession though. The differential lock still needs tweaking, because the driving rings easily slip when the lock is engaged. Apart from the differential lock everything works as expected. This is what it looks like right now:
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From what I've built myself and from what I've seen from others, the two most important aspects are lines and consistency. At least that's my personal believe. No matter how close you get to the original, there will be gaps, but more importantly, there will be visual lines implied by your panelling, lines that will define the flow and character of your overall design. So I would generally pay more attention to these lines than to gaps. With consistency I mean the whole body should be equally dense, otherwise you will get the effect that the less dense areas look unfinished.  Source: http://www.scottdesi...-im-working-on/
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This is what I mean (hope you don't mind me photoshopping your image):
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It looks a lot better already, but I still have the feeling there is a 'crack' between the front-section and the mid-section, which is emphasized by the front fenders being straight and the doors being inclined. Also, imo the drop in the hood towards the windscreen is overdone and causes the windscreen to stick out too much. As for the 'crack', can't you incline the front fenders with the same angle as the doors (so the fender and the doors make parellel lines) and make a small drop with the panel in-between the fender and the door, so they don't make a single straight line. And maybe also incline the rear fender with the same angle.
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Or move them back by 2 studs and make them 2 studs longer and combine this with moving the curved panels in the roof to the back.
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Nice work already! I agree the roof seems too high, but maybe part of the issue is that the flanks near the hinge of the doors are too low. The dashboard rises higher than those parts of the body. I think it will give a more sporty look when the cabin sinks a little more into the body, if you know what I mean. EDIT if you could move the 3x7 panels directly too the sides of the dashboard 1 stud upwards and 2 studs forward, so they overlap the 3x11 curved panels, you might get a higher flank without losing the flow of the fenders. EDIT2: I think it would also be better when the hood would arrive at the bottom of the windscreen a bit higher. In real cars there is always space for windscreen wipers underneath that part of the hood. This would also help sinking the cabin a bit more.
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Excellent. @jb70, will you add this to the pimped up version?
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Can't you attach it to one of your fast buggies and see if you can make it float like a kite? Perhaps in a sports hall?
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Here you go. It might need tweaking when I build it in real life, but I'm confident it will work out fine. I'm going to try that. I will have to insert the race tires the way I do with the CLAAS tires though.
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I ordered all the parts I need. I opted for black, because it looks less messy. I also found a way to firmly connect Porsche rims to the turn-tables (secured with 6L steering links sticking out the rims). So I'm a bit on a cross-road as to what kind of car this is going to be. Perhaps I should let the performance decide...
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This is one of my favorite tc-15 projects. Very original and maybe it can actually float / fly eventually. Keep up the good work ?.
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Grum's Shed
Didumos69 replied to grum64's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
I am so sorry ?. I hope the end result compensates a little for this demoralization. I enjoy your writings ?. Thanks! -
Later on in the build, the outer ends of these 7L axles are fixed by the main structure and will straighten out as your build evolves. The 7L axles are used as torsion bars, which is not uncommon in suspension setups. It has nothing to do with caster or anti-roll bar (the anti-roll bar is added in step 47). The 7L axles are used this way because the shockabsorbers are too soft to carry the weight of the final build. In this case I think it would have been better to use 2 shockabsorbers, it might still require a torsion bar, but not with this much bending.
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See this is an old post, but this should work with the frame oriented the way shown in the screenshot, with the open ridges turned upwards that is, but the beam can surely give problems.
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Great reviews, thanks!