Best simple lifting mechanism: rotating joint or elevator?

Hi! I was hoping to get some advice on the lifting mechanism (if that’s the preferred term, please correct me if it is not) for a Vex robot my team is designing for a class project.

My experience with Vex is limited to just these past few weeks, and I unfortunately don’t have the ability to personally test out different designs from this point due to limited access to Vex materials.

In order to maximize the building opportunities I have left, I’ve tried to find relevant insight on the forum and other sites. However, the latter results only have general information, while the former seems to involve designs that go higher (than my group needs to) with scissor lifts. I may have also just searched poorly due to not knowing the precise terminology, so if that’s the case, I would appreciate any redirection there too.

Regardless, I was hoping to get advice as to which of the simple lifting mechanism is best based on other builders’ experiences, and perhaps which particular type as well (rack + pinion, chain, string, etc)?

Out of the numerous videos I’ve watched to get an idea about the Vex design needed for our class project, it seemed like a chain elevator was the best combination of being fast and stable, but a rotating joint + arm could help lift up the robot if it were to fall forward (and in our case, could work around our robot’s current design + slightly too high base by letting the claw be closer to the ground).

Can anyone provide insight into the accuracy of this observation as well as other advice? Thank you tons in advance!

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Elevator lifts are pretty hard to get working well. The simplest is just a rotating joint, but is also quite limited. You may want to attempt a 4 bar.

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Agreed. Elevators can have tricky friction issues.

A 4 bar is quite simple to build and if you need more height you can make it a 6 bar.

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First of all, thank you for responding!

Is there a reason the elevators lifts are hard to get working well? The designs I observed, like these two https://i.imgur.com/rRYyd8O.png, seemed to work fine, but differed in speed + stability.

Also, if a 4 bar lift is what it appears to be based on YouTube videos, it’s unfortunately not ideal for our group due to “cost”- and weight-related reasons. We plan on likely having just a maximum of 3 more metal frames with whatever design we choose, and the 4 bar seems to involve a decent amount more (as well as an extra motor that we cannot have).

It seems we may have over-estimated what kind of height you need. So, how high do you need the lift to go?

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I would recommend a elevator / Cascade lift, with black spacers as rollers.

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Hi, thank you for your replies as well!

Our maximum height is basically 17 inches or so, though that’s wishful thinking on my part since very few groups in the past have stacked that high in our class. A reasonable estimate would at least be 8 inches.

you could easily get 17 inches from a 4 bar, they are one of the easiest lifts to build

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So I searched a bit more, does this 4 bar design https://www.vexforum.com/uploads/default/original/2X/0/0cf75d14a5ba60daaca1b942ae8ec00099113efb.png resemble the one you’re suggesting?

yes, that would be a 4 bar linkage.
very simple, but also quite useful.

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what exactly are your design constraints?

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This seems like a 4 bar might even be overkill. But, hey, it works. It’s one of the easiest things to build, once you understand it.

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@grlygrl28, to continue on the line of questions that @sazrocks started to ask, could you tell us other constraints that you have?

How many motors could you use?
How many structural pieces could you put on your robot?
Do you have any limit on the gears or sprockets at your disposal?

What type of objects do you need to lift and how high?
Do they have to stay parallel to the ground (like stacking cubes on top of each other) or they could rotate (i.e. dropping balls into buckets)?

Is there a limit on the initial height of your robot?
For example, does it have to be under 18" tall or you could build whatever you want as long as you have enough materials?

Does it have to be mobile to accomplish the task or you could do a static base like a mobile crane with rotating boom?

Finally, is it going to compete with other robots and what is the criteria for the winning? For example, is it tallest stack or the fastest build time?

Depending on the task we could figure out a bunch of suggestions, that could both save you time and building materials.

For example, if you are short on metal pieces, you could still build a four bar with string or chain replacing the top bars of your robot.

Or, if you don’t need to move around the field, then tower crane might be an option if you are allowed to use string…

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Hi, thanks for your reply! If the 4 bar is an overkill, do you mind clarifying what design would be more appropriate? I’m totally all ears to anything that may save money or weight.

Honestly if you want to go even lighter a chain bar is a reasonable option, provided you don’t need to lift anything particularly heavy.

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Anything you’d get from us might be a bit overkill. We’re all a little confused on the project constraints, I think.

A 4-bar would be amazing. You could get way over 17" very easily with one.
(I assume this is EDR-based, and not a misplaced IQ thread, in which case a 6-bar might be needed)

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I can PM the constraints if that may help; I’m avoiding posting the full specifics in the thread due to privacy-related reasons when it comes to Google Search results. And yep, it’s definitely EDR-based - all metal frames.

Would it be okay if I screenshotted that pm and posted that here for the greater community benefit? (Or you could just do it on a blank Doc or Note or other word-processing software) (Search terms obviously can’t read the contents of an image.)

The only concern there would be us all referencing specific parts of the project, bypassing the whole point of using the image as a filter.

I’m definitely not the greatest mind online, but, if you want to start a pm conversation with the parties responding here, that would serve you the same purpose.

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The image is a good idea, thanks for suggesting it! Here’s the info: http://i.imgur.com/5QrmBCe.jpg

Most efficient lifting mechanism would be an (overly complicated) DR4B like the game “In The Zone,” but that is insanely overkill.

Especially for stacking, you’d want a 4-bar. Cascade lifts(forklifts) can be efficient, but usually they are slower than 4-Bars. (Albeit they do lift linearly, unlike the 4-bar)

This sounds like Skyrise, and, if this was a game for the general community, you would see a lot of those designs. (Which are way too complicated for such a small project)

I would definitely Spring for the 4-bar with a small clamping claw to grab the cubes. I would also fear it down for torque to keep it as accurate as possible, at the expense of some speed. (Or just have 2 buttons to control it; one full speed one and a slower speed used for fine tuning)

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