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Unread 07-30-2012, 10:08 AM
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pic: My Rendition of Emperor Swerve

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Unread 07-30-2012, 10:09 AM
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Re: pic: My Rendition of Emperor Swerve

Pretty nutty design using all those motors but other than that it looks like a beauitful detailed model. Would be interesting to see some more details like the pods. The frame looks potentially very flexy which might or might not be an issue
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Unread 07-30-2012, 10:44 AM
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Re: pic: My Rendition of Emperor Swerve

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Originally Posted by Joyride_67_1902 View Post
What are you using for wheel speed and steering angle sensors?


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Unread 07-30-2012, 10:45 AM
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Re: pic: My Rendition of Emperor Swerve

There are some tiny details that are missing, And I wanted to do something different, something that wasn't for competition use, but easily could be converted to something that would compete. So the 550 Gearbox can be taken off and a new belt put in place and it would power the drive train at an FRC legal drive.

Pod renders should be posted later tonight hopefully.

- Andrew
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Unread 07-30-2012, 10:49 AM
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Re: pic: My Rendition of Emperor Swerve

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Originally Posted by Ether View Post
What are you using for wheel speed and steering angle sensors?


Encoders are on the underside of the pod, along with the shifting mechanisms and all motors.

I've never designed a crab so I assumed an encoder would be the kind of sensor to use in predicting the rotation of the pods.

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Unread 07-30-2012, 11:05 AM
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Re: pic: My Rendition of Emperor Swerve

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Originally Posted by Joyride_67_1902 View Post
Encoders are on the underside of the pod, along with the shifting mechanisms and all motors.
Did you have specific part numbers in mind for the wheel speed sensors, and the steering angle sensors?


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Unread 07-30-2012, 11:06 AM
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Re: pic: My Rendition of Emperor Swerve

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Originally Posted by Ether View Post
Did you have specific part numbers in mind for the wheel speed sensors, and the steering angle sensors?



http://usdigital.com/products/encode...otary/shaft/S4

This is the encoder I have picked out.
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Unread 07-30-2012, 02:48 PM
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Re: pic: My Rendition of Emperor Swerve

Render Album attached, I didn't want to Spam CD media.


https://plus.google.com/u/0/photos/1...50412732351601

Enjoy

-Andrew
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Unread 07-30-2012, 02:57 PM
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Re: pic: My Rendition of Emperor Swerve

There is a lot to talk about on this, I like the thoroughness in your design.

Probably the largest thing to comment on is the steering setup; Although I am an engineering student, it was pretty simple analysis to show that relatively small bearings (regular roller ones at that) which are very inexpensive are more than robust for the steering setup. If you have an engineering mentor with a mechanical background (or for a rougher analysis, anyone who has done statics or could do a halfway decent Free Body Diagram) they could thoroughly show this concept to you. OR, you could just take my word on it.

We initially looked into large bearing rings and similar setups, and they're just a lot of parts/complexity for all the ways we had tried to implement it.
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Unread 07-30-2012, 05:06 PM
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Re: pic: My Rendition of Emperor Swerve

I would have to disagree with Adam.

Using larger bearing for the steering in the wheels is not very complex.
Adam's math may be right and you may be able to get away with regular bearings just fine (973 used swerve this year and if they used them it probably is). But I would say that it is not complex at all to design a swerve using larger bearings. There are several ways to decrease the amount of components it takes in the design.

I would say the dynamic load of thrust bearings is a lot greater, than normal bearings, and I usually fall on the side of it is better safe than sorry, which is why I prefer the larger OD thrust bearings. McMaster-carr sells them for a good price, and even have some neutral file formats available for CAD purposes.
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Unread 07-30-2012, 05:56 PM
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Re: pic: My Rendition of Emperor Swerve

Well what I did for bearings of the steering is a large AL disk that would go inside of a delrin bearing machined for the profile of the AL disk. I've seen people do this before with great success. At least I think I have. The pod first started with one bearing on the top and then once I realized the side load would be bad on it I added the bottom circular bearing as well.

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Unread 07-30-2012, 06:50 PM
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Re: pic: My Rendition of Emperor Swerve

I agree with Adam that using a combination of regular roller bearings would be far simpler for this. If you want a cheap thrust bearing we use the $4 Lazy Susan style turntables (6031K31) from mcmaster. We use these in tandem with needle bearings that handle the radial loads.
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Unread 07-30-2012, 08:42 PM
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Re: pic: My Rendition of Emperor Swerve

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Originally Posted by steelerborn View Post
I would have to disagree with Adam.

Using larger bearing for the steering in the wheels is not very complex.
Adam's math may be right and you may be able to get away with regular bearings just fine (973 used swerve this year and if they used them it probably is). But I would say that it is not complex at all to design a swerve using larger bearings. There are several ways to decrease the amount of components it takes in the design.

I would say the dynamic load of thrust bearings is a lot greater, than normal bearings, and I usually fall on the side of it is better safe than sorry, which is why I prefer the larger OD thrust bearings. McMaster-carr sells them for a good price, and even have some neutral file formats available for CAD purposes.
We are probably saying the same thing and you aren't realizing it. When I said small bearings, I meant not a large custom disk bearing. Our steering bearings were still relatively large compared to "standard" FRC bearings as we used a pair of 6805-2RS for radial load and a 1.375" Needle Thrust bearing off mcmaster for the axial load (5909K39). Using Metric bearings for radial was the key to keeping the sum weight of the bearings low and still inexpensive.

Our math is definitely correct (couple hundred hours of runtime in abusive conditions), with quite a bit of factor of safety as well. What we did is well on the safe side.
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Unread 07-30-2012, 09:49 PM
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Re: pic: My Rendition of Emperor Swerve

I knew that your math was correct 973 has used the design successfully (and quite fun to watch IMHO).

When you said "standard" FRC I thought that was the normal size, the larger size makes a lot more sense.

However, I still disagree that doing so can make things less complex it all comes down to your ability as a designer, what I find simple others can view as complex.
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