pic: New serve mk.1-2517

[Tyler2517]

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[Tyler2517]

http://imgur.com/a/H6Qcm

[magnets]

That's a really neat swerve drive. I don't think anyone's done something like this before.

A few questions/comments-

I'm assuming the really big green thing that goes in the middle of the wheels is a bearings. If not, what is it? If so, why is it so big?

Those bevel gears- where are they from? Are they strong enough? They're at the end of the reduction so they're going to try really hard to get away from each other. The little one is going to push up so you'll probably want a thrust bearing/washer there too.

The green angle to support the sides has the mounting holes too close to the edge. Making it a little bit wider around the bolt holes is cheap strength.

How is torque transferred between the bevel gear and the wheel?

What type of wheels are those?

Overall, a pretty cool iteration on swerve.

It's pretty neat to see these offseason swerve designs come back. There's usually some pretty cool ones like this!

[Tyler2517]

Originally Posted by magnets

That's a really neat swerve drive. I don't think anyone's done something like this before.

A few questions/comments-

I'm assuming the really big green thing that goes in the middle of the wheels is a bearings. If not, what is it? If so, why is it so big?

Those bevel gears- where are they from? Are they strong enough? They're at the end of the reduction so they're going to try really hard to get away from each other. The little one is going to push up so you'll probably want a thrust bearing/washer there too.

The green angle to support the sides has the mounting holes too close to the edge. Making it a little bit wider around the bolt holes is cheap strength.

How is torque transferred between the bevel gear and the wheel?

What type of wheels are those?

Overall, a pretty cool iteration on swerve.

It's pretty neat to see these offseason swerve designs come back. There's usually some pretty cool ones like this!

The green thing is a spacer that lets us translate the power from the wheel with the bevel to the wheel with out. It has 12 threaded holes in it so that we can offset the bolts so the load from each one of the wheels so there is a lot less shear force(each wheel has 6 holes.)

6 holes on the gear.

The bevels are from sdtp. We are not using the stock materials and will custom make them our selves if the ones are not strongthat we can buy.
We are looking at making the bigger of the gears out of a titanium alloy most likely Ti-6Al-4V Trading a week of my summer to clean there shop in trade for the machine time and resources to make 20ish on there 5 axis cnc. We do not want 2 of the same material gears so we don't have to grease them so carpet cant get stuck in the grease.

Custom wheel 2.78 in diameter if i remember.
https://drive.google.com/folderview?...sp=dri ve_web

[cadandcookies]

Originally Posted by Tyler2517

Trading a week of my summer to clean there shop in trade for the machine time and resources to make 20ish on there 5 axis cnc.

That is a very nice deal.

[Chris is me]

Originally Posted by Tyler2517

The green thing is a spacer that lets us translate the power from the wheel with the bevel to the wheel with out. It has 12 threaded holes in it so that we can offset the bolts so the load from each one of the wheels so there is a lot less shear force(each wheel has 6 holes.)

I'm having trouble picturing this so I can't be sure, but doesn't this just mean each bolt is loaded in single shear instead of double shear? I think 12 bolts going through both wheels would be stronger since the bolts are in double shear. Both are probably overkill.

We do not want 2 of the same material gears so we don't have to grease them so carpet cant get stuck in the grease.

Why does having two different materials negate the need for grease? Why does having two of the same material necessitate it?

[Tyler2517]

I suck at explaining.

The spacer in the middle will have 12 holes threaded in to it. each wheel will have 6 bolt holes they will be threaded in to the middle spacer every other hole so that we don't have large amount of shear force going through the green spacer.
The wheel is really small and trying to get room for 12 bolts is both supper heavy and over kill for a 2.78 inch wheel. We were trying to have no nuts/bolt heads on the out side of the wheel so that we can get the walls of the moduler as close as possible.

Having the 2 different materials will cause much less wear. Just like running 2 steel gears on each other will cause rapid wear. Having the titanium gears running on a brass alloy gears will let us put very little grease on it with very little wear. That way the carpet fibbers will not get cough in the gear grease causing us not to bind our gears like last season.

[T^2]

Are you sure you want to be loading screws in shear at all? Why not replace half of them with spring pins?

[nathannfm]

Originally Posted by T^2

Are you sure you want to be loading screws in shear at all? Why not replace half of them with spring pins?

Aren't all of the extremely common dead axle (sprocket/pulley bolted directly to the wheel) drives in FRC putting 6 bolts in shear on each wheel? (we found out what happens when you accidently forget 3 of the bolts...ignore the EI metal )

[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.

[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.

[Chris is me]

Originally Posted by nathannfm

Aren't all of the extremely common dead axle (sprocket/pulley bolted directly to the wheel) drives in FRC putting 6 bolts in shear on each wheel? (we found out what happens when you accidently forget 3 of the bolts...ignore the EI metal )

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.

[Lil' Lavery]

Why transmit torque through the screws at all? Do something similar to what Vex does with their versahubs.

[autox_vette]

Not all of the force is transmitted through the bolts (in an ideal world, none of it would be).

Think about the wheels on a car. They are held on with 4-6 studs in single sheer. Some are taking 500+ HP. The bolts/studs only hold the wheel onto the hub and create a HUGE clamping load between the wheel and the hub. All of the power is transmitted through the friction between the wheel and hub.

So, it depends upon what your wheel and spacer materials are. If you use metal, then less sheer force is transmitted to the bolts because you can get enough clamping force to transmit the power. If you use plastic/nylon, you probably can't get enough clamping force, so some power will be transferred as sheer force on the bolts.

Kenton