Posted December 22, 2024Dec 22 In the past week or so, I've been working on a car for the 1:12 racers competition of next years Buwizz gathering. The rules state that each participants vehicle must have at least two of the following features: opening doors, working steering wheel, suspension, working fake engine. For a long time I struggled to pick what to build, I thought about a warthog from halo, because all wheel steering would give it good maneuverability. I also thought about an LMP1 car, but some tests found that neither of those were good options for me. Then, I was inspired by a rally version of a porsche 911 3.3. The building process started with the front axle, I wanted to have at least 2 studs of ground clearance so I could comfortably drive on grass or gravel. To do this, I decided to use part 2393 rather than part 48989. This allowed me an extra stud of ground clearance compared to the solution I used in my mini racer this year. Spoiler The 9 module flip flop beam is still unreleased, and not added to LDD new parts yet, so I made my own one with this handy tool, then used LDD brick editor to add it to LDD. I have uploaded this file here, along with the 3d model I was working off in LDD. The steering rack is in front of the center of the front axle to keep the model as compact as possible, but unfortunately meant that the steering axle rotated in the opposite way to how the working steering wheel should. Luckily, the spacing between the axle for the steering wheel and the actual steering wheel was perfect for 4x 8t gears, meaning the steering wheel rotates the correct way. Next was the rear drive. I knew from my previous mini racer that 2 Buwizz motors would have plenty of torque, I previously geared up 2x from the slow output and had no issues. For this model, I chose a less extreme gear ratio because I wanted to have enough torque for light offroading, and with the higher weight and larger wheels I needed a lower rpm. I settled on a 20:16 ratio from the fast output. This gives me, theoretically, over 3000rpm at the wheels. I positioned the motors so that the rear part where you can see the actual motor is in roughly the same spot as the engine in the real car. This is also good for the weight distribution, as in my previous mini racer, I suffered from a lack of grip at the rear wheels for the huge amount of power I was putting down. Spoiler Then, chronologically, I added the working steering wheel, and seats. Because of the 3d model I imported, I was able to place the seats and steering wheel almost exactly where they should go in the real car. Spoiler Some simple chassis reinforcement followed, and then I assembled it in real life and did a test drive: At that point, I was happy with the performance, so I kept building the bodywork. I struggled for some time with the hood; the real car has a tapered hood but a straight hood was easier to make with lego and looked better. I would like to thank @N1K0L4, @Alex Ilea and @Zerobricks for helping me with that decision. Spoiler The next interesting thing I designed for this model was the front bumper. It is mounted to two rubber parts so that it actually functions to absorb some impact. Spoiler After the bumper the next interesting part of the build was the doors, which have a bi-stable mechanism to keep them closed while driving. This also fulfills the requirement of at least two of the listed functions. Spoiler And so, after making the trunk openable, it was all done, and time for a test drive. And that went pretty bad. So I've decoupled the rear wheels, they now run independent of each other. This will probably kill the performance on grass, but fix the performance on other surfaces... right? Anyway, I wrote all of this before finding out it drove poorly, and I'm not just going to delete it all. I'd be glad to receive any suggestions, I clearly need some help... More photos + files download: https://bricksafe.com/pages/Aurorasaurus/rally-porsche-1224
December 22, 2024Dec 22 Awsome model, full of functions. I like this more than the official sets. Also that front bumper was a nice thing to add :). 4 hours ago, Aurorasaurus said: I'd be glad to receive any suggestions, I clearly need some help... It depends on how bad the driving really is and what are the "symptoms". From what I can see, COM is quite high for a car this scale and quite far back too. That would suggest you have chronic understeer while driving on the road. Decoupling the motors should help with that and maybe add e-differential. You can also try cleaning and preheating the tires, these 49.5 x 20 mm usually have less grip than 43.2 x 20 mm ones. Edited December 22, 2024Dec 22 by N1K0L4
December 22, 2024Dec 22 Well done, Aurora. I can't wait to see it in real life. Only thing I would recommend is switching the drive gears to gain more torque at expense of top speed.
December 22, 2024Dec 22 Looks very cool! I do love the style of those rally Porsches. Hopefully you get the performance figured out! Also, are you flying all the way to Europe from NZ for that event? That's dedication!
December 22, 2024Dec 22 Author 1 hour ago, N1K0L4 said: It depends on how bad the driving really is and what are the "symptoms". From what I can see, COM is quite high for a car this scale and quite far back too. That would suggest you have chronic understeer while driving on the road. Decoupling the motors should help with that and maybe add e-differential. You can also try cleaning and preheating the tires, these 49.5 x 20 mm usually have less grip than 43.2 x 20 mm ones. Tomorrow I will try film again, surprisingly the performance on the road isn't bad. But the model does flip over easily. About the tires, how would I pre-heat them? 1 hour ago, Zerobricks said: Well done, Aurora. I can't wait to see it in real life. Only thing I would recommend is switching the drive gears to gain more torque at expense of top speed. Thank you :) I switched the gears around in my mini racer this year, so yes, I will do that again to gain more control. 20 minutes ago, 2GodBDGlory said: Looks very cool! I do love the style of those rally Porsches. Hopefully you get the performance figured out! Also, are you flying all the way to Europe from NZ for that event? That's dedication! Thank you! And yes, the flights are... unpleasant. But it was worth it this year. If I can afford to go again, I will. Edited December 22, 2024Dec 22 by Aurorasaurus last year -> this year. 2024 is still the current year.
December 22, 2024Dec 22 1 hour ago, Aurorasaurus said: About the tires, how would I pre-heat them? Like this or you could try with a hairdryer or leave it on the sun for a bit (since you got summer now). Edited December 22, 2024Dec 22 by N1K0L4
December 22, 2024Dec 22 Wow, really nice MOC! I love the look, and the many functions in it. Can't wait to see the final version.
December 22, 2024Dec 22 Author 2 hours ago, bruh said: Wow, really nice MOC! I love the look, and the many functions in it. Can't wait to see the final version. Thank you very much! 4 hours ago, N1K0L4 said: since you got summer now Not that you'd believe it if you looked outside today... 58 minutes ago, NV Lego technic said: Where did you get the rules? I absolutely love off road supercars! I have a draft version from the gathering group chat, so they are subject to change.
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