4-bar problems (?)

Hello I’m a new vrc competitor and my 4bar lift is not working. I have rubber bands and have tried various positioning of it by it still stutters on it’s way up. When going up with a motor but not on, it has high resistance. The battery has been swapped, motor been added and still it does not work. With 1-motor, it does not have enough force to lift a cap. With 2 motors, it seems to preform worse.

How hard is it to move with no motor?

well there must be a problem in either your gearbox’s build, or your motor, or your code, as a 7:1 with one motor should be able to lift a cap fairly well.
can you post your code, and maybe a video of it trying to lift?

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Are you sure the two towers are parallel and are remaining parallel? I think I see only one screw holding each of the 1x2x1 c-channels to the 1x5x1 c-channels below. That leaves them very vulnerable to twisting, and if they twist you can get a ton of friction on the axles.

Also, if you can put the tower closer together, then there will be less room for the axles to bend. If the lower two axles bend, you might get some skipping between the small metal pinion and the large green gear. You didn’t explicitly mention skipping, but that would cause stuttering.

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Thank you for your suggestions…

How do I go about posting a video?

hmm looks like .zip files can’t be attached with this new forum, you would have to link to the video somehow. maybe put in on your google drive and post a share link

The easiest is probably to stick it on youtube and imbed a link from there.

Xenon is probably right on this one. Friction seems to be the issue.

To tack onto what was said above, are the spacers too tight? (Can you spin each freely?)

If moving the towers closer together can’t be done for some unforseeable reason, I would duplicate the gear setup onto both sides of the active arm. That is, screw another gear into the other side of the arm and mesh that to another 12 tooth pinion on the motorized shaft.