Our VEX team is working on our Starstruck robot and having trouble getting our six bar to lift all the way, as the motors are straining. We’re on a significant time stretch, so temporary solutions and long-term solutions are appreciated, but short-term more so.
What’s happening is when the button is pressed on our joystick that runs both motors to lift the six bar, it seems to be staggering. The bar lifts quite slowly and jerkily, which is odd. I used the same basic construction as several YouTube instructionals, which also used two 393 motors, but ours seems to not work. I tried adding rubber bands in the pictures, but it doesn’t seem like they’re helping. More rubber bands stop the lift entirely. If i guide the bottom bar with my hands, the lift works great. It also goes down smoothly.
Any and all suggestions are GREATLY appreciated. We have a school “mock tournament” tomorrow and we’re trying to get our robot working by then.
i dont know where or who you heard from, but 2 motors will not lift a 6 bar, especially loaded down with scoring objects, we have 6 motors on our 1:5 6bar, but it struggles to lift cubes, so the reason its struggling is because of lack of torque, not a build issue.
Thank you for the quick response. Where would you recommend adding the additional motors, or how should we change our design to accommodate the extra motors?
No bearing flats seems to be your biggest issue. A square shaft turning in a square hole is never good. As a good rule of thumb, whenever you have a shaft going through metal, use a bearing flat. 2 motors is also underpowered depending on what kind of loads you are trying to lift. However, it looks like that’s all steel; if you want to keep two motors bump up that gear ratio to a 1:7 or higher and add a lot more rubber bands. The placement you have rubber bands right now is also not the best; place them between the bars of the six bar. Here’s a very bad drawing:
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Where the stars are mounting points for rubber bands.
i would recommend essentially adding an idler gear (of any size) below your powered gear, and then have a motor powering a 12 tooth gear, on both sides of the lift, heres a kinda drawing
0
@
0
@
0
@
with the @'s being 12 tooth powered gears, and 0’s being your idler/arm gears
edit:formatting
you could, but the high strength (which i recommend) 12 tooth metal gears do badly on each other, creating tons of friction, if you used smaller idlers, any size you want, you get way less friction
What does your button code look like? All of the above suggestions are good, but that stutter can be your code sending a lift value and a stop value at the same time. Be sure you are giving those motors only one instruction. Something like:
I would also suggest adding rubber bands from the top of your tower to the bottom of the middle vertical bar, and from the top of the middle vertical to the bottom of the outer vertical. This will assist your motors in lifting the linkage.
