Hey all, I’ll be giving a workshop on elevator design at the mentor conference and would love to get any input or questions here for things I should cover.
I will be publishing the slides after the workshops as well.
Thanks!
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Here are some of mine:
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What measures do we need to take for rigidity. Especially considering the new SDS bearing blocks that are only mounted by one hole depth on each side.
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Punched vs lightened box tube?
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What type of rigging? Is continuous rigging important for robot performance?
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Are constant force springs something worth the time and weight investment for robot performance and motor efficiency in the days of powerful brushless motors? (This is more targeted at when using cascade rigging)
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I’d love to hear about ways to improve elevator stability, both overall and in between individual stages.
Additionally, the pros and cons and use cases for different types of rigging materials (string vs belt vs chain).
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I was curious to what extent teams do dynamic drive tuning and control as they raise and lower tall elevators while on the move. In other words, to maximize traction and lower tipping risk what do teams do in their drive control as the robot’s cg is rapidly changing?
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Design patterns for getting stiffness between the ground stage and drive base without excessive weight, and for stiffness everywhere else without excessive weight.
Design priority of simplicity vs weight… We ended up reverting to a chain driven ThriftyBot architecture and the absolute chunkiest ground stage for reliability after losing a week and a half of schedule continuously rebuilding a 6328-style string design on the beta bot that just would not stay together… And then ran out of weight for algae handling.
What can I simulate or do math on to find “sufficient” stiffness?
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Really up to you but maybe some more advanced elevators. Such as capstone or in tube rigging
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A couple questions I’ve had to work through with students in the past:
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Why design something when I can buy this COTS kit from [vendor of choice]?
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How do I pick which system to buy, besides looking at which high ranking teams or RI3D bots are sponsored by or using the kit from said vendor?
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I’ll be attending your talk for sure
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Gearbox design for Elevators
With how powerful FRC motors are getting, you can run some crazy ratios for superfast elevators
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Adam, very much looking forward to seeing your presentation slides after the conference.
Is there a library somewhere of past FMC presentations - slides, recordings, or otherwise?
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I don’t know, I’m not that guy.
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I would be interested in the following topics:
What sort of transit times do the top teams aim for, top to bottom and bottom to top?
Compare and contrast wide vs narrow elevators.
Different ways of bracing the elevator structure.
Rigging and drive methods compared and contrasted; single-sided winch with CF springs, double-sided winch, belt drive, chain drive.
Methods for managing the wires going to the mechanisms on the carriage.
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How would you describe these elevators you are teaching about?
Lean, not mean?
Thrifty, not shifty?
Crude, not rude?
Gritty, not pity?
This is the most important question.
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For continuous belt drive:
Any tips on reducing belt sliding friction?
What are realistic effective belt radii guidance
General:
discussion on wear and maintenance.
discussion on “spare” strategies for competition
What types of failures have you seen? What spares mitigation strategies have you seen being effective or ineffective.
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Doing some real numbers for the relationship between the key stress parameters:
- Roller diameter
- Beam material (normally Aluminum)
- Beam corner geometry (Rev vs simple box)
- Minimum overlap (L/D ratio)
- Bending load
I don’t know that anyone has actually run numbers on this…
Beam corners will require some tricky FEA to really nail down. Decent approximations would be valuable anyway.
There isn’t a wide range of roller diameters. Plastic shod rollers would have a lower point load on the aluminum, but much more likely to throw a shoe/blow out. THOUGH, flat face 80/20 type rollers could be used!
Helping people understand what the relationship between overlap and contact stresses would be valuable. Also useful would be some info on the maximum coefficient of friction for motion to happen. That relationship is why almost all elevators use ball bearings to make the effective coefficient of friction approximately zero.
80/20 V-groove beams are kind of a special case, having radial and moment loads on the same rollers.
Bonus points for running contact force/fatigue numbers for the most common roller diameter on Aluminum!
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Can you please go into more detail on this design
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+1 to this
The biggest problem we ran into this season related to our elevator was managing our cable chain. It caused us problems from week 0 all the way to the off-season. For us this year it steamed from having an open top elevator that had crossbars on both the 1st stage and stage 0. And then being on opposite sides.
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There are some interesting design options covered in this thread:
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Should you care a bunch (or at all) about natural frequency/stiffness and such?
Are people who excessively care about this stuff weird? (I think I already know the answer to that one though)
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Yes (within reason) and maybe
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