Voldemort87

Just tried a quick swap of the 1.66:1 motor drive to 1:1. Seemed to work as well as before. just faster! Now the final gear ratios are 20.97:1 in the low gear and 2.52:1 in high gear. I will probably decrease the high gear speed for more usability. At present high gear can be used to cruise fast only on a flat surface.

Another general question, how much torque is ideal for a trial truck? If there is an approximate value, then it will be easier to optimize the gearing. I think 34.8:1 in low gear with 1 XL motor might be an overkill. Probably I can keep the reduction at around 24:1 for 1 XL motor considering that TLC Zetros is around 12.6:1 with 2 X L motors. Any thoughts on this?

lol, I actually shot it close to a forest area! Thank you. Actually, I had increased the playback speed of the outdoor video to make it bearable to watch without falling asleep :D It is fast in the high gear but not much torque to overcome stones. Maybe i need to optimize that. good observation of the periodic motion, that is correct. I think it is because of the transmission and axle twisting. Unfortunately, I don't have Buwizz at the moment, not available here, but definitely will give it a try sometime if I can get it. Thank you! I will try bigger bumps next time. Speed is slow in the low gear. I increased the playback speed in the video. movement jerkiness as mentioned above might be because of the transmission/axle twisting. Steering is fine as per my obeservation. It might looks a bit jerky because of the faster playback speed. I am using control+ motors. Suspension is not stiff but I think it is limited by the amount of travel a 6.5L spring can accommodate. chassis flex also helps a lot. If I replace the springs with a 9.5L spring then it might work better, which I don't have with me at present. a single soft spring is too soft and the model sinks in its weight.

Love the model and the presentation. especially the cut section view. :)

Any thoughts on the video?

Beautiful MOC, both the bodywork and the technical layout! I got into Lego technic last year with the 42108 crane. so really happy to see a much bigger and more functional MOC.

Very nice chassis layout. Looks tight. Body work proportion can be improved, I think. Looks a bit flattened.

Swapped already. Will use black rims for the outdoor trial. Thank you for the insights that helped in improving it. I also learning for me in terms of stiffness - Lego Hard spring > 2x Soft springs > Soft spring

Finally managed to compile a short video. Hope you like it.

Yes, in the virtual model for now :) Black rims do look better I feel.

yes I do!

Final photoshoot made after making refinements mostly in the frame and suspension. The harder springs were too hard. instead going ahead with 2X soft springs. Suits the weight of the model well with the right amount of compression. Added stickers as well!

The drivetrain looks well packed. Liking the layout. would like to see the video pls :)

Thanks, added that. Hope this is what you meant.

Strengthened the steering motor mounting to minimize the movement of the motor while steering; Strengthened the link from the ball join to other differential and move the springs right above the axle to reduce friction. Thanks @gyenesvi for pointing that out! In addition to that I have extended the axle out into the wheels to minimize the movement of the wheels laterally because of the play in portal axles. Thanks to @MangaNOID for the idea!

I made some minor tweaks in the body work to make it look meaner. More suggestions welcome!

Even I wanted to hide it below the loading bay in the rear at first, but then the cable was unable to reach the hub from the front steering motor. Also, this position gave me better weight distribution and flexibility below the bodywork. Thanks to your observation, I fiddled around and changed the spring position right above the axle. I think this definitely works better. I did a few trial runs and noticed that the wheel is having lateral movement when facing the obstacles. I think I need to strengthen the axle a bit more.

Thank you :) haha!

Thank you. I can totally relate to what you are saying :D

I think XL motor with sufficient gear reduction seems to handle the load. I don't have experience in rock crawling, but in the indoor tests it seemed ok. Unfortunately I don't have videos yet. Keen observations! Yes, It is not ideal to have rack connecting outside the pivot. But considering the limitation of the portal axles with a minimum width, this is the best I could manage. For the maximum steering angle of 20 degrees, wheels remain parallel. You can observe in the image below. The U-frame and O-frame connection is also supported on the inside with the connector in the front axle and from the top with a beam in the rear axle. Yes, there is space below the motor. As I mentioned earlier the spring travel is not much. Instead the frame twists and compensates for the springs. I can try it out when I modify the chassis for tractor tires. In the current package it seems a bit tight without raising the chassis. I can already start fixing these points you mentioned in the next iteration :) I also want to do an alternative body work for the mog, maybe an expedition unimog!

Hope this is clear from the images now. Added! The digital model is almost complete. I am new to the Bricklink studio as well. So any feedback/tips on that is also welcome!

....and the body work.

Nice explanation, thanks for sharing!