Problem with arm lift losing power

my team built a double bar lift that works great when they first power up bot and lift first 2 cubes. when they go to lift a third cube the arm doesn’t have enough power and cant lift the cube at all. Then they get a red blinking light on the brain. The lift has a motor on each side. Anyone ever heard of this before?

Do the motors feel hot? What are the motors geared to? What error does the brain get?From this it’s either A the motors can’t handle the load or B the brain is messed up.

The motors do feel hot. And we hear that long beeping sound as if motors are working too hard. There is no error code on the brain, it just blinks red until we turn it off and back on again.the gear ratio is 12:36:36

That sounds like your motors are working too hard and overheating. A few ways to fix this is to reduce their load, rubber band it, or gear it slower. I am not for certain since I have never been in iq, but you could burn out your motors and make them worthless.

Your ratio, 1:3, isn’t strong enough to lift in iq. I’d try to move to 1:5 minimum but 1:7 is probably better.


Are you certain the motors are not working against each other? My team built a single 4 bar lift with 1:3 Gear Ratio and 1 motor and it works the entire match.

Their bot is very small. I don’t know which gears to use to make it 1:5 or 1:7. Is there a diagram out there we could look at?

You could look up “gearing ratio vex” and some things would pop up, but smallest to biggest gear you have is optimal.


A 12 tooth gear driving a 60 tooth gear gets you 1:5 . EDR has 84 tooth gear, so you could get 1:7 there, but I’m struggling to come up with a compound gear box that gets to 1:7 in IQ

Can you post a picture that gets to the details of the gear box?


Ok. we figured out a way to gear it 1:5 but it took away the last inch they needed to lift to the high green platform. we havent tested it on the field yet.


That high platform is THE challenge. :wink:


My team built a 4bar lift geared 1:5. It only lifts the cube about the same height as the motor placement, nothing higher and there is a noise coming from the motor that makes it sound like the load is too great. It worked the very first time but not after that. This is the highest gear ratio we can work with. The structure seems find because it can lift all the way up without a cube.
Does motor orientation matter?

the gears are meshed horizontally. Does that matter? should it be meshed vertically?

I’m not quite sure what you mean by this; could you post some pictures?


The motors are using too much battery. I would suggest replacing the motors with other ones.

Try using some rubber bands to help lift the load. Also check that the bars are parallel.


Do you have a picture of the lift? That may help us understand better. 1:5 is plenty of torque and shouldn’t require rubber bands at all.


might not be that…
how long have you been using that motor for the arm?
if more than 2-3 months, it might be burned out.

I used a double bar lift as well and it worked fine with only one motor. It could be the gear ratios.

Sorry about the late post

The red light means that your robot battery is dying / dead. It’s quite possible that it’s not charged enough to lift. You should do the charge cycle, let it sit for 10 mins and put it in the robot. Then check out the voltage on the VEXIQ brain to see what the actual charge is like. It should be well over 7.2 volts. If not, put it back in the charger.

I’ve seen lots of designs that fail due to low battery voltages.

Second, try pulling one motor off the side and see if one motor can move the arm. Then try the other motor by itself. I’ve seen cases where one motor is running at a different speed, creating drag on the arm.

Since this thread is from November, I’d like to assume that you’ve solved this. If so, can you post what your solution was?