My team has a dual 4-bar arm setup that uses two motors. I have seen multiple teams on youtube that manage to only use 1 motor for 2 four bar arms. How does that not make one arm lag behind the other? My team and I really need to figure this out so that we can use a 4 motor drivetrain instead of 2 motor.
You can use c-channel (or standoffs) to put bracing between the two sides (either normal or X bracing)
Gear ratios, rubberbanding, and/or proper bracing
This may be helpful:
DR4B Tutorial by 333A
I would also recommend using high-strength axels if you have them and if they will fit on your bot.
My team built a 4 bar with one motor. We have virtually no cross bracing whatsoever. (we probably should add some) The drive motor is connected to a high-strength axle which is connected to gears on both sides of the lift. The axle does not twist very much so the drive power is put into both sides evenly enough.