Why is my DR4B moving like this?

VEX V5 Technical Support
#1

Our team built this DR4B as a test with V5 but the thing is that when we power the motors, it moves in a very awkward manner. If any of you could let us know what’s happening, it will be greatly appreciated. Here is the video of the robot.

Thanks.

#2

Don’t know if it’s just me but video link doesn’t work for me.

#3

Sorry, I put a hyperlink on the text now.

#4

It doesn’t look like the motors are trying that hard to lift it. Does it move freely if the shafts are disengaged from the motors?
Does it have 2 motors? Are they both trying to lift it and not working against each other?

Edit: I see it is just one. Is the motor working ok disconnected from the lift? What internal gear ratio on the motor?

#5

The motor works fine without the DR4B and the lift also runs quite smoothly. The gear ratio is the green one? I think thats 18:1 internal gear.

#6

From the way the metal is moving, it appears to be twisting side to side. Is something binding? Do you have bearings where anything goes through metal? Are all the arms the same dimension? When first lifting, the top bar appears to shift toward the back and to the sides… could there be a bent shaft somewhere? If you provide some assistance by lifting lightly, will it move freely then?

1 Like
#7

Can you supply a video of you moving the dr4b manually without any controller input?

#8

are you trying to lift with no external ratio? I haven’t experienced the power of v5 motors yet, but running a dr4b on one motor with no ratio at all sounds way too optimistic to me.

#9

Yeah, now that I look at it there is no external ratio. That’s your problem @RougeScaless

#10

@Xenon27 Good catch!

#11

If there is no external ratio, the lift is trying to fully extend at 200rpm so go from zero to full in a fraction of a second.

#12

try a 1:5 or maybe even a 1:7 ratio. I’d go 1:5, but if there is some friction and if it wears out try 1:7.

#13

1:5 should work fine. My robot had a similar lift with V5 and 1:5 works fine and dandy.

#14

Ok cool. 1:5 then should do it, its nearly impossible to power a lift of any sort without a gear ratio, definitely impossible with a one motor dr4b.

#15

Ok, I’ll try it with 1:5.

#16

Thanks everyone, after putting on the gear ratio, it worked!

#17

I would strongly suggest never dragging a V5 brain around like that even if it’s a quick test run. It hurt me to watch that poor thing flop around.

#18

Yes I know, it was just that I was alone at that time and didn’t have enough hands or cables.

#19