Suspension stiffness/compliance generates an additional angular deviation, which adds to the one generated by the chassis stiffness shown in this video.
Thanks a lot. I love going to different prominent spots very early in the morning (at sunrise, without audience) to shoot some footage. Enjoy our hobby!
Hello there, awesome build, I really like it, so much details on there as well! Hard to beat- I was wondering where did you get those small metal parts like those L profiles or those things that goes on the corner to protect it etc.. and how are they called at least. Thanks!
thanks for your interest, and you kind words. I order these little metal pieces at Aliexpress. But I don't remember exactly how they were called. Try to search for terms such as treasure, miniature, metal, furniture, etc..
I appreciate you discussing this subject but your analysis is not correct for crawlers. Torque twist we experience in low speed crawling is not angular acceleration (that your discussion is based on). It would be f we were interested in drag racing however. But when crawling it is just static torque experienced at the rear prop shaft and how that is resolved into the rest of the suspension that affects us. Its as simple as that. You can observe it when climbing up a steep hill at steady state (no acceleration or inertial effect). You can also feel it by holding the front axel off the ground whilst the rear is driving. Also, rotating the motor 90degrees is also incorrect as this does not affect the torque moment at the prop shaft.
You are completely right. However, our community discusses torque twist in different ways. Some mean the dynamic one (like in drag races) which I analysed in this video. Others, like you, mean the static one, which I explained in two other videos. Find them here: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-rm92oxDlU-c.htmlsi=wIdVyfomwUOkV4HF or ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-tlaYVUsg1vw.htmlsi=68gZ-nKng-AQkMOH
@@rcscientific6004Thanks for replying. Yes that second static torque video is really the key for crawlers and problems people have. I noticed Cape Crawlers made a video on the subject but confused it with rotational inertia based twist and even used you hanging string visualisation. As a suggestion, it would be helpful for the community to see how you can reduce the torque twist experienced when climbing by changing spring rates, increasing axel gear reduction (bevels and portals) and reducing wheel diameter. And even using lower rolling resistance tyres will reduce the required prop shaft torque. I was surprised how significant that was when changing over to ultra soft tyres from hard stock items. Keep up the good work.
Your shock absorber calibration calculation is good from a mathematical point of view if and only if the shock absorbers had no friction. Which is not the case, especially on the lightest crawlers (under 3 kg) for which the friction of the joints is important compared to the force of the spring. On mine (2.5 kg), I fitted traxxas GTS 0.22 springs (Ref 8042 - yellow) to have 50% SAG. With your calculation I would have used 0.30 (too stiff)
You are right. My calculations ignore friction, especially static friction (stiction). However, if you get a suspension system with little stiction, and consider slow movements only (to ignore dynamic viscous effects), they should be a good estimation for a good spring rate.
You need to raise the upper links position higher at the axle mount. Raise the upper links 5mm to 8mm with a custom mount & your torque flex will be nearly be 95% all gone. Only going up straight vertical inclines will cause any torque flex that is left that you will not be able to get ride of because every single crawler vehicle has some level of torque flex in all honesty.
