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  #16   Spotlight this post!  
Unread 21-12-2011, 09:40
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Re: pic: I was bored... so I designed this.

Just to add a quick point onto Evan's post: A 6WD swerve, in theory should also handle climbing objects a little better, depending on the object and the implementation of the swerve. A 4WD swerve would require quite a bit of ground clearance at the center, which may or may not be advantageous. A 6WD swerve would need ground clearance similar to a conventional 6WD. (For more clarification, look at some of the 4WD robots from 2010 vs the 6WD robots and you'll see what I mean.)
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Unread 21-12-2011, 13:43
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Re: pic: I was bored... so I designed this.

Also, the other solution is to drive each side independently, and then turn corners together.
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Unread 21-12-2011, 15:22
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Re: pic: I was bored... so I designed this.

The title of this thread is "I was bored... so I designed this."

How much time did you spend on the design? I see a number of these every year and figure that there are hours and hours spent.

Thanks!
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Unread 24-12-2011, 17:29
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Re: pic: I was bored... so I designed this.

Sorry for the late response I have been busy the past few days. I spent about 4 nights working on this design. I designed this in 4 stages, I started with the module design, then I designed the mounting set-up, then the frame, and then finishing the assembly. Each stage was about a day of design.
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Unread 27-12-2011, 04:57
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Re: pic: I was bored... so I designed this.

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Unread 27-12-2011, 09:06
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Re: pic: I was bored... so I designed this.

That design will eat bevels for breakfast. Nom Nom Nom teeth.

Since it's non-coaxial, when the module turns the drive will turn against it.

That said, VERY nice work, and just a gorgeous design.

The cantilever is not so much of a design problem - you're not going to be facing massive forces on the bushings. I don't see the bushings taking that much of a beating. You may want to consider beefing up the module itself though. It looks thin.
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Unread 27-12-2011, 10:01
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Re: pic: I was bored... so I designed this.

It's good to see some exploration of bearing options but the application of the thrust/needle rollers on the wheel drive shaft is problematic.

1) The keyway would not be compatible with the needle bearings.
2) The counter thrust for the thrust bearing at the wheel would be by the needle bearing housing or the frame member, which is not good. A preloaded pair of angular contact bearings would be better. There is no particular side thrust to keep the thrust bearing loaded.
3) The gear separating force from the tooth meshing + the torque from the robot weight will be bending the vertical plate. It may be better to continue the removable vertical plate down the the lower shaft, so that the wheel shaft is not cantilevered.
4) Why is the wheel contact patch offset from the pivot axis? My understanding is that you want to avoid the turning force from a wheel drag moment seen at the pivot. This moment could cause twisting, scuffing, excessive drive resistance and problems with rigging to drive straight.
5) Note that I am not itemizing the many things I like about the module design.
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Unread 27-12-2011, 16:20
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Re: pic: I was bored... so I designed this.

Quote:
1) The keyway would not be compatible with the needle bearings.
2)The counter thrust for the thrust bearing at the wheel would be by the needle bearing housing or the frame member, which is not good. A preloaded pair of angular contact bearings would be better. There is no particular side thrust to keep the thrust bearing loaded.
I did not realize that, but now that I think about that it makes sense. I will change that, I was working on a version that used an angular contact bearing. I have not worked with them before so I wasn't sure how to approach them.

Quote:
3) The gear separating force from the tooth meshing + the torque from the robot weight will be bending the vertical plate. It may be better to continue the removable vertical plate down the the lower shaft, so that the wheel shaft is not cantilevered.
I had a version of this that has that plate extended down to the wheel shaft. On the newest version I have completely removed the cantilever (replaced the modules with our current modules)

Quote:
4) Why is the wheel contact patch offset from the pivot axis? My understanding is that you want to avoid the turning force from a wheel drag moment seen at the pivot. This moment could cause twisting, scuffing, excessive drive resistance and problems with rigging to drive straight.
That is a problem I have fixed that in the newest version.

Thanks for the comments, they have been very helpful.

Here is the newest version so far.
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