New and Improved Lift Design!!!

[snowpenguin]

A quadruple four bar built like this but with the arms mounted at the top of towers would be able to reach about 12 feet. Show me your math. 18"x4 arms should be about 6 feet, max. Add in the thickness of your joints and maybe you’re at 7 feet…

[vex5757]

@Inspector Gadget

Here is a pic. I am 6’4"(76"), so the lift is about 6’(72") tall.
https://vexforum.com/attachment.php?attachmentid=8358&stc=1&d=1398880698

when collapsed, it is at 12", so the extended height is 6 times the collapsed height

The motors at the joints are going to be controlled independently, right? If so, the arm is going to have at least 2 more degrees of freedom than, say, a scissor lift. Wouldn’t this make the positioning of the arm a bit of a challenging? I see a very nice inverse kinematics problem…

Modeling Inverse Kinematics in a Robotic Arm - MATLAB & Simulink

[J.Brown_team4768]

Getting a intake system that will have work after rotating 90 degrees seems like it might be a problem (without extra motors devoted to turning it back of corse).

[hapee]

@vex5757

The motors at the joints are going to be controlled independently, right? If so, the arm is going to have at least 2 more degrees of freedom than, say, a scissor lift. Wouldn’t this make the positioning of the arm a bit of a challenging? I see a very nice inverse kinematics problem…

Modeling Inverse Kinematics in a Robotic Arm - MATLAB & Simulink

The final design that inspector gadget is thinking of will have all the pivot points linked unlike in the photo, he was just demonstrating the height of it if you were to put two sections together. Sorry for any confusion.

[hapee]

@snowpenguin

A quadruple four bar built like this but with the arms mounted at the top of towers would be able to reach about 12 feet. Show me your math. 18"x4 arms should be about 6 feet, max. Add in the thickness of your joints and maybe you’re at 7 feet…

Your right that around 18x4 is around 6 feet. The total design inspector gadget want to go with fully loaded will be eleven feet(ish?) with the number of cubes inspector gadget wants to hold. Sorry for any confusion about the height of the lift itself.

[snowpenguin]

Especially with how vertical that quadruple four bar goes in order to reach, you are going to see massive tipping issues if you plan on lifting more than a couple of cubes at a time to that height… Let alone 5 feet above the lift

[Inspector_Gadget]

@Team80_Giraffes

I was skeptical about this at first but now I am thinking it may be pretty good. It’s definitely something to play around with and see if it gets you better results. Thanks for sharing.

Thanks!!

@Team80_Giraffes

1. The double revers bar has a longer bar since you are along the diagonal of the triangle, but you don’t normally get full extended height like this does. Does the extra length of the hypotenuse outweigh the extra extension angle? We had a two double reverse four bars this past season and the lift height (from the ground to bottom of element) was not nearly as high as you might think, but that may be due to being under 12". Also you had the connection points a wee bit different that might help too. (Sorry don’t have a close up at hand…)

The etended height is actually longer than a normal bar here, because in both situations a bar is at max 17.5 in, the max height of the Danny lift, doing some basic math, is 17.5 in per section, where as for the regular double reverse four bar is only 16.94 in see This post for an explanation of some funny trig

@Team80_Giraffes

2. This looks like it could use a ton of motors. Do you want to allocate 4 motors to a double set of lifts like this? We’ve had two motors geared for speed on a 64" scissor in gateway.

It will use a ton of motors if you configure it exactly this way, however, you should be able to decrease it to 4 motor total lift for a height of ~70 in, leaving 4 for drive and 2 for intake.

@Team80_Giraffes

3. How are the sides held together? I don’t see any cross bracing in the CAD/you tube video. The 60 tooth gears and the 1x5x1 c-channel only leaves a few spots for connections that might torque a bit in ways you don’t want it to.

The sides are braced together with standoffs seen in the left of the picture from post 41. they can also be seen in the other two YouTubes I posted.

@Team80_Giraffes

4. How can you get good rubber band/elastic band assist on this? The spacing between the bars is typically best versus over the shoulder where they tend to get chewed up by gears and the like. That space can also be valuable for staying in the 18" box.

Here is a place to mount them. I can fit at least 60 rubber bands on, using both sides of the c bar and both the top and bottom sections
https://vexforum.com/attachment.php?attachmentid=8385&stc=1&d=1399399107

https://vexforum.com/attachment.php?attachmentid=8386&stc=1&d=1399399648

@snowpenguin

Especially with how vertical that quadruple four bar goes in order to reach, you are going to see massive tipping issues if you plan on lifting more than a couple of cubes at a time to that height… Let alone 5 feet above the lift

Yes, this is a very big problem, but we are working(almost done) on ways to prevent tipping. 8 cubes 11 feet high provides more force tipping than a single motor or pneumatic can overcome, so this will be interesting…

[Jinduckey]

@snowpenguin

Especially with how vertical that quadruple four bar goes in order to reach, you are going to see massive tipping issues if you plan on lifting more than a couple of cubes at a time to that height… Let alone 5 feet above the lift

Hm, explain why it matters that it goes vertical? Any lift that goes that high will have tipping issues. I would say that his lift would have less tipping issues than the elevator lift you were planning on building, because at least his centre of gravity shifts backwards as the lift raises to lessen forward tipping, while backward tipping can be solved with anti-tips.

[snowpenguin]

Better be very careful. If your robot really was that tall, you are starting to look at possible s1 violations when something (almost inevitably) goes wrong. Even the 6.5 foot tall elevator bots are going to be very VERY tippy. At twice that height… You’re going to have to have tipping bars on all sides and even them might still be very tippy.

[snowpenguin]

@Jinduckey

Hm, explain why it matters that it goes vertical? Any lift that goes that high will have tipping issues. I would say that his lift would have less tipping issues than the elevator lift you were planning on building, because at least his centre of gravity shifts backwards as the lift raises to lessen forward tipping, while backward tipping can be solved with anti-tips.

His robot is supposedly 11 feet tall. Any elevator will be more stable.

Elevators are more stable for tipping because the cog does NOT shift forward or back. When his lift goes vertical, it will be shifting a LOT of weight very height and towards the back of the robot (or the front) which will make it have upping issues that an elevator will have far less of because elevators keep the cog on top of the robots center all the way up.

Edit: thinking about it, I guess the only weight that will ACTUALLY shift forward or back in this quadruple four bar is the weight of the lift itself. The weight mounted at the end will go straight up and down. Still, it’s going to be very tall and with how kuch metal is in this lift, it’s weight will matter for cog.

[Jinduckey]

@snowpenguin

His robot is supposedly 11 feet tall. Any elevator will be more stable.

Elevators are more stable for tipping because the cog does NOT shift forward or back. When his lift goes vertical, it will be shifting a LOT of weight very height and towards the back of the robot (or the front) which will make it have upping issues that an elevator will have far less of because elevators keep the cog on top of the robots center all the way up.

I don’t think the weight of his lift moving a few inches back very slowly qualifies as a lot of weight very height and towards the back of the robot. The thing is, robots aren’t at risk of tipping while only lifting. It’s when moving that they actually tip, and as I said, elevator lifts are more at risk for forward tipping.

[Vultec]

Sorry if I’m overlooking something really obvious, but why does the top of your robot reach 11 feet? Why does it need to? A standard door is 6 foot 8-and the top of your robot will be four and a third feet higher than that. Is it just to include this lift in your design?

[hapee]

@Vultec

Sorry if I’m overlooking something really obvious, but why does the top of your robot reach 11 feet? Why does it need to? A standard door is 6 foot 8-and the top of your robot will be four and a third feet higher than that. Is it just to include this lift in your design?

So what inspector gadget would like to do is be able to hold something like 8 cubes (crazy right haha), it would be more efficient than going back and forth tho (provided it works decently) so if the skyrise was built to 60 in. or whatever its max is, and he would have the 8 cubes stacked up to 64 in. high that stack would have to go up another 60ish in. to get over the top of the post.

[hapee]

@snowpenguin

Better be very careful. If your robot really was that tall, you are starting to look at possible s1 violations when something (almost inevitably) goes wrong. Even the 6.5 foot tall elevator bots are going to be very VERY tippy. At twice that height… You’re going to have to have tipping bars on all sides and even them might still be very tippy.

Of course there is some danger with having a robot that high and if it tips it could fall out of the field and seriously injure someone so we will be testing it a lot for safety but for now its just a goal that is set for us if we can do it safely.

Thanks for your concern.

[snowpenguin]

@Jinduckey

elevator lifts are more at risk for forward tipping.

This is just not true. There is no evidence to support this claim… Elevators keep their weight i the center and it doesn’t move forward or back.

[Jinduckey]

Wait I believe I already said my reasoning. If your centre of gravity is in the back, there is less forward tipping compared to when your COG is in the centre. His lift moves COG to back as it raises. Thus it is less prone to fwd tipping, and theoretically would be slightly, slightly better about tipping.

[Vultec]

@Jinduckey

Wait I believe I already said my reasoning. If your centre of gravity is in the back, there is less forward tipping compared to when your COG is in the centre. His lift moves COG to back as it raises. Thus it is less prone to fwd tipping, and theoretically would be slightly, slightly better about tipping.

If it shifts the COG back, even though it is less prone to forward tipping, during an acceleration from the drive, it is more prone to backwards tipping.

[snowpenguin]

That isn’t an answer to why an elevator lift is a tipping issue when it doesn’t shift the cog forward or back AT ALL…his lift honestly only shifts the cog a tiny bit too. If it really shifted the cog back much more the whole thing would fall over often. If it shifted it forward it would fall over often too. Linear lifts are necessary this year to keep from tipping… Hence why all three of the lifts being talked about lift linearly. The double four bar is just the one that shifts cog the most.

[Jinduckey]

@snowpenguin

it will be shifting a LOT of weight

@snowpenguin

his lift honestly only shifts the cog a tiny bit

Hmm…

Anyway I never said elevator lifts had tipping issues. I just said that they would slightly, slightly more prone to tipping than his lift (almost comparable in fact). This was only to rebutt your point that his lift is “very prone to tipping”.

[snowpenguin]

Well I obviously went back on your first quote in my edit, but thanks for taking it out of context

No, elevator lifts are NOT more prone to tipping than double four bars.