Swerve Concept

[AdamHeard]

Originally Posted by Greg Woelki

It would be advisable to go further on the speed side of the motor curve than one would be with the reduction that I used in my calculation, hence a minimum of a quarter of a second. I suppose that half a second would be more reasonable in this set up.

I'm not sure where you're getting your numbers at all.

The two wheels spaced far apart will take substantially more torque to turn, there is no way they will get BETTER performance than current optimized narrow centered wheel swerves.

[jimbo493]

The original idea was to put holes in the 1in flanges pointing up/ down and bolting that into the frame with a sorta of square of 1x1, (ill post a pic later)

I do see how it could twist and bend, I have some ideas...

Im thinking we may stick with 2 wheels for now, I don't think its worth a total redesign of the bottom GB ATM, What id like to do is just get a prototype made to see how it it all goes together and see what has to change.

I might play around with a 1 wheel version if I get the time to. This is actually my first major CAD project, so I am pretty proud of it, but I see a lot of valid points that ill try to implement. I really appreciate the feedback.

PS:

This is the large tapered bearing I was talking about http://www.mcmaster.com/#5709k31/=smy6cy

[Tyler2517]

Try 3D printing it out to insure that everything works as expected. It is always easier to re design then spend a couple hundred hours of frustration trying to get a bad concept to work.

[jimbo493]

Originally Posted by Tyler2517

Try 3D printing it out to insure that everything works as expected. It is always easier to re design then spend a couple hundred hours of frustration trying to get a bad concept to work.

The biggest thing is seeing what our vendor's tolerances are and their accuracy, but I do want to 3D print it as well

[Greg Woelki]

Originally Posted by AdamHeard

I'm not sure where you're getting your numbers at all.

The two wheels spaced far apart will take substantially more torque to turn, there is no way they will get BETTER performance than current optimized narrow centered wheel swerves.

In this post, OP said a BAG is used for pivoting

I estimated that around 80in*lbs would be needed to turn that two-wheel module. A BAG motor has a stall torque of 3.5in*lbs, so, while more reduction would be better, I went with 100:1 in my calculation. Free speed of a BAG motor is 14000 rpm, so 140rpm with the reduction and 108rpm under the load. That works out to 0.56 seconds per rotation, or a bit over 0.25 seconds for 180 degrees.

So, while it may take more torque to pivot and while one may want to run the motor further on the speed side of its curve, that is where I got my numbers.

[jimbo493]

Originally Posted by Greg Woelki

In this post, OP said a BAG is used for pivoting

I estimated that around 80in*lbs would be needed to turn that two-wheel module. A BAG motor has a stall torque of 3.5in*lbs, so, while more reduction would be better, I went with 100:1 in my calculation. Free speed of a BAG motor is 14000 rpm, so 140rpm with the reduction and 108rpm under the load. That works out to 0.56 seconds per rotation, or a bit over 0.25 seconds for 180 degrees.

We will most likely be using a 100:1 ration on a versa planetary gearbox, then that turns a 34t gear which tuns the 60t turning gear, I'm not to good with these gear calculations so yeah.

[Greg Woelki]

Originally Posted by jimbo493

We will most likely be using a 100:1 ration on a versa planetary gearbox, then that turns a 34t gear which tuns the 60t turning gear, I'm not to good with these gear calculations so yeah.

Okay, so about half a second or so.

[AdamHeard]

Originally Posted by Greg Woelki

Okay, so about half a second or so.

Based on assumptions you've made of the loading without evidence.

Time to rotate must also factor in the control loop. It can't operate at full speed the entire time.

I'm not trying to pick on you, just pointing out it's dangerous to publicly state something that can be perceived as fact when it's not a proven fact.

[Greg Woelki]

Originally Posted by AdamHeard

Based on assumptions you've made of the loading without evidence.

Time to rotate must also factor in the control loop. It can't operate at full speed the entire time.

I'm not trying to pick on you, just pointing out it's dangerous to publicly state something that can be perceived as fact when it's not a proven fact.

Don't worry, I appreciate your responses. I'll make my assumptions and thought process more clear in the future when I make an estimation.

[Jefferson]

Originally Posted by Greg Woelki

[url="http://content.vexrobotics.com/vexpro/pdf/217-3197-Drawing-20140115.PDF"]Having a wheel on each side will significantly increase the torque required for pivoting and it will probably take a minimum of a quarter of a second or so to rotate a module 180 degrees.

Why would you ever rotate a wheel more than 90 degrees at once?

[Tyler2517]

Originally Posted by Jefferson

Why would you ever rotate a wheel more than 90 degrees at once?

I was about to ask this.

[Greg Woelki]

Originally Posted by Jefferson

Why would you ever rotate a wheel more than 90 degrees at once?

You wouldn't, that was just my picturing of the module rotating, not really applicable.

[jimbo493]

Originally Posted by Greg Woelki

You wouldn't.

We will to calibrate the steering, but only then

[RyanShoff]

For reference, last year we used Bag motors with 90:1 versa planetary gearboxes (10x3x3) for steering with no issues. We had no further reduction after the Versas.

[magnets]

Originally Posted by Jefferson

Why would you ever rotate a wheel more than 90 degrees at once?

If you don't want to switch the direction of your drive motor, like team 118 did in 2008.