pic: New serve mk.1-2517

[EricH]

Originally Posted by AdamHeard

I'd suggest avoiding purchasing anything at a college bookstore. Much better deals on amazon (especially used), ebay (used/internationl), and smaller companies that have used books.

At least looking to see what they have. If they're changing editions, they might be dumping the older edition as fast as possible--read "discount".

[kk052]

Originally Posted by Chris is me

While this is common and may work, it is not optimal. Screws aren't great in shear due to the stress risers of the threads and the effectively smaller load carrying diameter of the bolt. A better solution is to use 3 bolts for fastening and three shear pins to take the load. Shear pins are better simply because they aren't threaded and thus have a larger effective diameter.

thanks for the advice ill see about replacing half the bolts with shear pins

[kk052]

Originally Posted by Gdeaver

This design effort seams to be focused on mechanical losses experienced in the 2014 swerve module. What specific problems did you have? Have you identified where the losses on the current module are? Have you quantified the total losses? I see some potential problem areas in the current Module. Before I say more, what have you found so far? Know what the 1st iteration problems are before you design the 2nd iteration.

it was designed to be smaller, lighter but stilll be made cheaply (-ish), the lower number of transfers is a result of deciding to remove the chain and first axle of a traditional swerve,(because steel chain is heavy)
im no expert on mechanical efficiency (that's Tyler's job) but the system should be more efficient if we took out an axle and a chain (once again i could be wrong, im not too good with theoretical mechanical efficiency, if it stalls we just throw another moter on it and/or lower the ratio)

[Tyler2517]

Here are the 3D printed prototypes. Super small we made them really dense so we could do performance testing with wheel tuning and gearing on that.
Supper small the whole bottom yoke is smaller then your standard 4 inch wheel.
http://imgur.com/a/spJtM

On a side note you could put this on a ftc robot.... with ease they sell plastic gears identical to the ones we would use and the 3d print with some fine tunning could print something i would put on a robot.

[CENTURION]

Doesn't look like anyone has mentioned this yet, so I will. You're going to have a lot of trouble turning this module.

If I understand correctly, both wheels are locked together? When you try to rotate the module while the robot is stationary, one wheel needs to spin one way, and the other needs to spin the opposite, because the center of rotation is between them. And when the robot is moving, and you attempt to rotate the module, one wheel will have to turn faster than the other.

What you need is some sort of differential, so that when turning, the wheels are able to rotate independently, but you can still apply drive power to both.

Here's a great old video that wonderfully explains how differentials work (at least in the context of cars)

[kk052]

Originally Posted by CENTURION

Doesn't look like anyone has mentioned this yet, so I will. You're going to have a lot of trouble turning this module.

If I understand correctly, both wheels are locked together? When you try to rotate the module while the robot is stationary, one wheel needs to spin one way, and the other needs to spin the opposite, because the center of rotation is between them. And when the robot is moving, and you attempt to rotate the module, one wheel will have to turn faster than the other.

What you need is some sort of differential, so that when turning, the wheels are able to rotate independently, but you can still apply drive power to both.

Here's a great old video that wonderfully explains how differentials work (at least in the context of cars)

it was argued about in the design process about the use of a diff, we decided not to to save space and make the unit simpler, and the less things to go wrong the better, also if there are any ramps in the 2015 game and one side of the wheel gets on it, all the power will be given to the other wheel. we are going to have to use a lower ratio to turn it however

[asid61]

Originally Posted by kk052

it was argued about in the design process about the use of a diff, we decided not to to save space and make the unit simpler, and the less things to go wrong the better, also if there are any ramps in the 2015 game and one side of the wheel gets on it, all the power will be given to the other wheel. we are going to have to use a lower ratio to turn it however

As long as you use a beefy turning motor (not a window motor) you should be fine.

[kk052]

Originally Posted by asid61

As long as you use a beefy turning motor (not a window motor) you should be fine.

a bane bot 775 (i think) on a 132:1 ratio is what we used this year with no problems, and most likely what we will use on the prototype, if we have any issues we may use a different gearbox, or find a way through code that the wheels never pivot in place, only when the wheels move forward/backward will the assembly turn, but this is what we are prototyping to find out.

[Tyler2517]

Originally Posted by kk052

a bane bot 775 (i think) on a 1:4 ratio is what we used this year with no problems, and most likely what we will use on the prototype, if we have any issues we may use a different gearbox, or find a way through code that the wheels never pivot in place, only when the wheels move forward/backward will the assembly turn, but this is what we are prototyping to find out.

We used a 430 on a 132/1

[R.C.]

Originally Posted by Tyler2517

We used a 430 on a 132/1

A 430?

[Bryce Paputa]

Originally Posted by R.C.

A 430?

Nope I was wrong. 430 is probably a typo, there isn't a banebots 400 series as I assumed.

[Andrew Schreiber]

Originally Posted by Bryce Paputa

It's a weak, fan cooled, motor that's smaller and weaker than a rs550

That's, kinda, not on the list of approved motors?

[R.C.]

Originally Posted by Bryce Paputa

Nope I was wrong. 430 is probably a typo, there isn't a banebots 400 series as I assumed.

http://banebots.com/p/M3-RS395-12

Might be this guy, I believe it was legal at some point in time. But with the current motor allocations teams should just use the 550 or the 775.

[Tyler2517]

We used the 540.

We designed initially to use a 400 series moter with a moduler mounting plat to the gear box. Ended up using a 540.