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  #91   Spotlight this post!  
Unread 01-30-2018, 01:31 PM
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Re: Week 3 Explosion

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Originally Posted by JacobD View Post
Is there any specific reason why you didn't just flip the part and run a second op?
We didn't run a second op because it was faster and easier to do in one setup.
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Unread 01-31-2018, 05:02 PM
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Re: FRC 95 2018 Build Thread

What is your center drop? While watching your practice videos 1 and 2, it seemed sometimes that there was alot of scrub:

https://youtu.be/v100-3iuFWw?t=55

https://youtu.be/v100-3iuFWw?t=112
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Last edited by Brian M : 01-31-2018 at 05:04 PM.
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Unread 01-31-2018, 05:12 PM
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Re: FRC 95 2018 Build Thread

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Originally Posted by Brian M View Post
What is your center drop?
From Above:

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Originally Posted by JamesCH95 View Post
Flat 6WD
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Unread 01-31-2018, 05:40 PM
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Re: FRC 95 2018 Build Thread

Yeah, lots of scrub, but also lots of stability. Defensive hits don't push us as far off course, turning is more controlled, and there is no rocking when your CG is way up high.
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Unread 01-31-2018, 07:37 PM
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Re: FRC 95 2018 Build Thread

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Originally Posted by JamesCH95 View Post
Yeah, lots of scrub, but also lots of stability. Defensive hits don't push us as far off course, turning is more controlled, and there is no rocking when your CG is way up high.
Why not add 2 omni's in the front? Keeps stability and gets rid of scrub.
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Unread 01-31-2018, 09:56 PM
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Re: FRC 95 2018 Build Thread

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Originally Posted by Matthew.Mc View Post
Why not add 2 omni's in the front? Keeps stability and gets rid of scrub.
Having 6 points of traction gets us the anti defense stability and super sharp turning that we have come to love from a flat 6wd. Colson wheels are also cheap, extremely durable, and provide great traction.

The scrub hasn't been a problem for us, so there is little incentive to compromise the performance aspects that we like.
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Last edited by JamesCH95 : 01-31-2018 at 09:59 PM.
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Unread 02-01-2018, 05:51 AM
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Re: FRC 95 2018 Build Thread

We stayed late last night and got the elevator on our practice robot working.

https://youtu.be/m6Ki1axxD2M
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Unread 02-01-2018, 07:01 AM
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Re: FRC 95 2018 Build Thread

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Originally Posted by JamesCH95 View Post
We stayed late last night and got the elevator on our practice robot working.

https://youtu.be/m6Ki1axxD2M
What is the weight of your elevator and what is the reduction on those 775pro's?
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Unread 02-01-2018, 07:15 AM
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Re: FRC 95 2018 Build Thread

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Originally Posted by apm4242 View Post
What is the weight of your elevator and what is the reduction on those 775pro's?
The end stage is 11lbs, and the mid stage is around 4 or 5lbs. The two 775Pros that drive the lift have 15:1 reductions driving a 1in diameter spool.

We bought a bunch of 3:1, 4:1, and 5:1 stages to mix and match until we get optimal performance. As it sits 15:1 is in the middle of the range we calculated would work well.
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Unread 02-01-2018, 07:44 AM
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Re: FRC 95 2018 Build Thread

Is your whole elevator attached to the chassis with 4 bolts a few inches apart? Is there a plan to add extra diagonal supports? If not, are you at all worried about the a force at the top of the lift (e.g. hitting the top into the scale plate) bending the whole thing over?

Also, what's making your gripper go down then up when you try to deploy it? Is that intentional or a bug?
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Unread 02-01-2018, 07:57 AM
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Re: FRC 95 2018 Build Thread

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Originally Posted by AriMB View Post
Is your whole elevator attached to the chassis with 4 bolts a few inches apart? Is there a plan to add extra diagonal supports? If not, are you at all worried about the a force at the top of the lift (e.g. hitting the top into the scale plate) bending the whole thing over?

Also, what's making your gripper go down then up when you try to deploy it? Is that intentional or a bug?
We're planning on adding a structure to brace the lift, but it integrates closely with our ramps, which we're still designing. One can grab the top of the tower and tip the whole robot over without any fuss though. The plywood deck does a great job of spreading that load around.

The programming didn't allow both wrist cylinders to depressurize due to a miscommunication. We're going to fix this tonight.
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Unread 02-01-2018, 07:59 AM
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Re: FRC 95 2018 Build Thread

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Originally Posted by JamesCH95 View Post
The end stage is 11lbs, and the mid stage is around 4 or 5lbs. The two 775Pros that drive the lift have 15:1 reductions driving a 1in diameter spool.

We bought a bunch of 3:1, 4:1, and 5:1 stages to mix and match until we get optimal performance. As it sits 15:1 is in the middle of the range we calculated would work well.
I think we'll have to do the mix and match thing, too. We're making a lightweight (~8 lb total) counterbalanced 3-4 stage continuous elevator just to place a hook. We'd like it to raise in less than 1.5 seconds. The JVN design calculator has limited usefulness because it's hard to account for the internal friction losses due to cable routing. And all the guides say to not underestimate the force needed to lift.
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Unread 02-01-2018, 08:00 AM
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Re: FRC 95 2018 Build Thread

How much does this weigh in its current form? It seems like you will be very close to the weight limit if you add two structurally strong ramps to each side of it.
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Unread 02-01-2018, 08:27 AM
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Re: FRC 95 2018 Build Thread

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Originally Posted by apm4242 View Post
I think we'll have to do the mix and match thing, too. We're making a lightweight (~8 lb total) counterbalanced 3-4 stage continuous elevator just to place a hook. We'd like it to raise in less than 1.5 seconds. The JVN design calculator has limited usefulness because it's hard to account for the internal friction losses due to cable routing. And all the guides say to not underestimate the force needed to lift.
Make all of your cable routing and cascading elements ball-bearing or otherwise roller contact and it'll be delightfully low-friction.

Quote:
Originally Posted by TetrisMaster View Post
How much does this weigh in its current form? It seems like you will be very close to the weight limit if you add two structurally strong ramps to each side of it.
Without the spool and motors and wiring/plumbing on the lift we were around 75lbs. As shown it's in the 80-85lb range I would guess. This gives us ~30lbs to play with for ramps, which I think will be plenty.
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Unread 02-03-2018, 09:09 PM
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Re: FRC 95 2018 Build Thread

Good progress this weekend. Found some weaknesses in the lift setup and have plans to fix or avoid them. Got a little bit of driving practice in.

https://youtu.be/PvroUTqvSL8

https://youtu.be/qjuJwLmnzGg

The tower brace is on and helps the lift's stability quite a bit. PID control on the lift helps piloting it too. Still some controls automation to work on, it's a little clunky as is.
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