[Issue] Problem with our arm

Hey! I’m from Team 2554, The Warhawks. We’re getting ready for comp, however we’ve encountered an issue.

Our arm is a 2 stage climber-in-a-box we bought this year, with our claw attached. We have added some paracord for extra strength. The issue we have is as follows:

Our arm is facing upward at a slight angle. As our robot extends the arm, the arm will extend until there is some bending on the arm. This arm is preventing us to extend fully. Basically, the bending is too weak for the springs to handle when it bends, and the rope really doesn’t do anything.

How can we make it so that the arm doesn’t curve downwards when extending outward? Our robot arm is posted below.


[dont mind the rope or the thing hanging, it isnt final]

There is a slight bend, shown by the demsos below:

We were wondering how to stop this bend, either by reducing weight, getting stronger springs (any recommendations??), or other solutions. We were thinking of rotating the arm 90 degrees, where the springs are on the top and bottom, not sides. We would love feedback!

Thanks!

Best Regards,
ratvioli

The “bend” will become more pronounced of an issue the less stage overlap you have, when the distance between the upper bearings of an outer tube and the bottom bearings of an inner tube get close together.

Unfortunately, the Climber-in-a-Box design is not really meant for horizontal arms, it’s designed for vertical climbing. Significant side loads, which are being applied by gravity here, is not a happy place for the nylon sliders.

Given that you have a climber in a box, there are some things you can do to improve this in order of easy to hard. I think you’re on the right track with your proposed ideas.

  • Rotate your arm 90* so the bearings are on the top and bottom. Bearings are much less affected by side loads compared to sliders, and this may help the sag too.
  • Find some stronger springs (McMaster has constant force springs) or double-up the ones you have so there’s more extension force
  • Ideally, convert it to a powered extension rather than relying on springs. This will let you put a lot more force to overcome the friction
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Alright, thank you so much! I’ll bring this up with my team’s mentor.

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