Bar lift still not lifting

Please, All i want to know is how do I get this 1 bar lift to lift up. Are there any tutorials? People have shown me how to make the bar lift, but I cant figure out how to make it lift. I can’t believe I build the Clawbot from the VEX Guide for Builing the Clawbot booklet, but can’t get this bar to lift. Any suggestions?

Is everything else working as expected? Why can’t it lift? Does the motor turn on but not have enough torque to lift it? Or does the motor not turn on at all? Is the motor on and the lift is not moving at all? There are many, many reasons why this could not be working - anything from a bad motor, bad wiring, bad programming, unengaged axle, reversed motor. The symptoms and the “why” of why it’s not working should give you some troubleshooting hints.

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What do you mean by torque? The motor turns on, the lift moves a little. The motors are brand new. I even open a new box a replaced it but it just won’t lift. I don’t get it. The wiring are all brand knew out of the box. I was told that it’s not the programming. Don’t know what unengaged axle mean, I will google it. Thanks for responding back. Below is the video link and some pictures.


capture1%5B1%5D capture2%5B1%5D capture3%5B1%5D

Are their any Guide for building a bar lift like their is for the clawbot?
Are their any bar lift tutorials that show you from scratch how to build one. All I see are 30 second videos that show you something already built and not able to see real well. I will not bother you again with this. I just can’t seem to get this bar to lift.

Take out the axle from the motor and try to move the arm. If you struggle to do so, then there’s friction somewhere that needs to be removed. Take spacing into account when building the lift. I’d also look into using aluminum; steel is heavy and hard to move. Finally, check gear ratio, both in the motor and in your arm. Try changing the motors to be geared for torque, and change the gear ratio from 5:3 to 7:1 on the arm.

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Unengaged axle just means that the axle is not fully seated in the motor.

Like the PP said, it sounds like you have too much friction and that is causing the motor to stall. If you reduce friction and still have trouble, you may need to increase your gear ratio.

Are you a student or an adult? If you are a student, your coach or robotics teacher can help.

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Firstly, don’t create a new topic if you are expanding on something, I becomes inconvenient when trying to reference something earlier in the thread. Also, take the chain off. It is only necessary for a chain bar (this is not a chain bar). Increase the gear ratio to a 7:1 which might be able to lift the steel.

Move the lift by hand and see if it’s going up. If it isn’t, the lift is catching on something.

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Either the arm or the large gear isn’t engaged with the axle (I couldn’t tell if the top axle was spinning from the video). If they were, the motor would not be able to spin without the arm moving. Make sure the arm is actually connected to the output of the motor in some way. Usually people bolt an arm to the driven gear through the screw holes in it.

I might be wrong, but it looks to me like you may have bolted the top gear to the arm and the steel tower. Is that the case?

Battlesquid, thanks for responding back. I took out the axle from the motor and was able to move the arm without a problem. I have sent a video of it. I also sent a capture of using black spacers on the sprocket but not the thick 60 tooth gear. I’m not to familiar with gear ratio checking and will have to google to learn that. Will get back to you on that. I’ve also sent a video on a summer camp I had the pleasure of running showing my students picking up boxes and stacapture1%5B2%5D cking them using the clawbot I show them how to build.

Hope this help.

Gear_Geeks: The axle was fully seated into the 393 2- Wire Motor. Will have to google on how to reduce friction and gear ratio. Will get back to you on this. I’m an adult, but I teach an elective Robotics class(Newbian) at iTech Miami’s Mega Technology Magnet High School. They blind folded me into this position. I’m learning as i go. Just so you know what I do, I sent you a link of the summer camp i did this pass summer. These are just a few of my students who i taught how to build a clawbot and this was the outcome. I made use of the boxes.
https://www.youtube.com/watch?v=pJMmn02RD8Y.

My supervisor and my students want me to show them how to build this:



I believe your issue is that your single motor just doesn’t have enough power to move the arm.
I infer this because you stated how there is a bit of movement, then everything stops. Your motor is probably not able to move so much weight.
I would advise a second motor, possibly geared to the arm as well.
You could also try using a HS 84 tooth gear if you have any. You appear to be using the 60 tooth HS gear.
(HS is high strength. They are thicker and stronger than normal gears.)
I can scrap up a quick prototype if you need extra help, since this appears to be for a school lesson, and I do understand that robotics takes a while to master.

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I can’t remove the chain because of my students.

I showed them how to do this over the summer at iTech summer camp:,

Now my students want me to show them how to do this

then this

and then this

Is this something your higher-ups (for lack of a better term) want you to do, or your students?
Because to be honest, I think your students are better off learning the clawbot arm(they have I’m guessing), then progressing to 4 bar linkages. They are most likely not ready to make a 6 bar given how they haven’t even made a 4 bar yet (I assume).
For reference, this is a 4 bar. fourbarup
I’m not trying to push you or your students away from trying, but what you’re doing seems to be too advanced for students who have only made a clawbot. (Again, I’m assuming, correct me if I’m wrong)
What level are they at? What have they recently done?
You can personal message me if you still need help :slight_smile:

That lift in the second video is a chain bar. Its purpose is to keep the object at the end of the bar at the same orientation at all times. The sprocket and the bigger gear both have circular inserts. The sprocket is screwed into the side of the tower. The bigger gear is attached to the channel that is being lifted. You need a gear ratio to get the lift to move.

Also, please be clear as to what your intentions are. The vex forum is here to help, however, earlier you said that you were building the clawbot and now your saying there is a set curriculum. Details like these can help us help you.

To repeat myself, based on the “bar lift31” video:

motor --> axle --> gear --> gear --> axle --> arm
                                  ^        ^
                                  |        |
                           One of these connections
                           isn't connected.
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Yes, I see it. The motor axle is spinning freely. YouTube should have lots of videos on chain bars. Perhaps look some up.

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Gear ratio refers to the size of your output gear over your input gear. Currently, your arm has a 5:3 gear ratio, because your 36 tooth gear is spinning a 60 tooth gear. This means that your arm will have 5/3 the torque output of the motor. When @64540A suggested you change your gear ratio to 7:1, he meant replacing the 60 tooth gear with an 84 tooth gear, and the 36 tooth gear with a 12 tooth gear. This would change the torque output to 7 times that of the motor.

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If the build hasn’t changed since the last post, I think you may have built the lift incorrectly.

The top gear should have square inserts.
The top gear should be bolted to the arm.
The sprocket on the motor axle should be drilled out so the axle can freely spin inside it.
The sprocket on the motor axle also needs to be bolted to the tower.

I would make a quick CAD model, except the computer I have access to can barely run Solidworks.
I highly doubt it’s a motor or friction issue as I used a single 393 motor, 18" arm with a 5:1 gearing during a past competition, and that was with a load.