pic: VR-001: A Jersey Voltage Simple Hex Frame

[Cash4587]

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[Lil' Lavery]

Love the simplicity. Elegant in that execution.

How are you attaching the bumpers? Have you done any structural analysis on those supporting members behind the bumpers? Or do you even particularly care if they deform?

[Cash4587]

Originally Posted by Lil' Lavery

Love the simplicity. Elegant in that execution.

How are you attaching the bumpers? Have you done any structural analysis on those supporting members behind the bumpers? Or do you even particularly care if they deform?

I'm not too worried on the deformation of them. Really the only reason they are there is to fulfill the bumper rules.. the wood is strong enough in terms of getting beat up. As for attachment, I plan to use some sort of clever method that requires little, to no thought and follows the simple method. Probably will end up being one attachment point on each corner of the frame including the hex points. Most likely will bolt them down to the tubes by using alum angle iron and 1/4-20 bolts.

[Oblarg]

Do you have enough space to pull those wheels without removing the outer hex frame if you need to do maintenance?

I'm not quite so sure I'd be comfortable with that little substance behind the bumpers on the side. I've seen some crazy deformations of fairly significant framing members through an FRC bumper (I've got a piece of last year's AM14U chassis sitting right next to me that fits the bill). The frame rules are there for a reason - if you take a hefty impact at the least-supported part of your bumper, are you certain it won't fail?

Cool solution for getting the motors out of the way. You lose the benefit of a direct-driven center wheel in the case of chain/belt failure, but that's probably a worthy tradeoff.

[Cash4587]

Originally Posted by Oblarg

Do you have enough space to pull those wheels without removing the outer hex frame if you need to do maintenance?

I'm not quite so sure I'd be comfortable with that little substance behind the bumpers on the side. I've seen some crazy deformations of fairly significant framing members through an FRC bumper (I've got a piece of last year's AM14U chassis sitting right next to me that fits the bill). The frame rules are there for a reason - if you take a hefty impact at the least-supported part of your bumper, are you certain it won't fail?

Cool solution for getting the motors out of the way. You lose the benefit of a direct-driven center wheel in the case of chain/belt failure, but that's probably a worthy tradeoff.

There is plenty of room in a sense to where in order to get the wheel off all you would need to do is remove the axle? And I can easily add some more support where I think its needed and repost a picture. Just give me a bit. The only purpose of that out framing member, yet again is for the bumper rules and to give the bot a Hex shape. 118 ran a setup similar to this in a sense to where they had zero "frame" touching their bumpers and they were fine. I am not too worried here and if it becomes a problem it is just as easy to replace them with some thicker alum or some steel.

[Oblarg]

Originally Posted by Cash4587

There is plenty of room in a sense to where in order to get the wheel off all you would need to do is remove the axle?

In my experience, the center of a robot can get crowded to the point where it's nice to be able to pull the wheels with the axles in place, which is why I asked. Also, you can't pull the axle on the direct-driven wheel without pulling the gearbox.

Just something to think about.

[Cash4587]

Originally Posted by Oblarg

In my experience, the center of a robot can get crowded to the point where it's nice to be able to pull the wheels with the axles in place, which is why I asked. Also, you can't pull the axle on the direct-driven wheel without pulling the gearbox.

Just something to think about.

No, you can pull the axles out, like out of the robot, like not into the robot, like out of the frame side, where the wheels are. As for the one on the gearbox, that is a different story. However, the only reason my team pulled off our wheels this year was to change the belts on the DT, which was because of ratcheting due to machining error. If we would have used tensioners on the system, we would have never needed to pull the wheels off. Yeah it's a "nice to have" but if this system ends up working, it will be far more effective than what we used in 2014.

[Cash4587]

http://prntscr.com/506kjk

Here is the DT with added support to the bump outs.

[Oblarg]

Originally Posted by Cash4587

No, you can pull the axles out, like out of the robot, like not into the robot, like out of the frame side, where the wheels are.

You can do that, but then they come all the way out of the bearing blocks (and ostensibly any sprockets you have on the other side are then loose, too).

Not saying you should change your design; it's a minor concern. It's just that I've spent a lot of time servicing drives, and little details like this are worth thinking about, if nothing else.

Originally Posted by Cash4587

http://prntscr.com/506kjk

Here is the DT with added support to the bump outs.

Cool, that certainly would be harder to break.

[Cash4587]

Originally Posted by Oblarg

You can do that, but then they come all the way out of the bearing blocks (and ostensibly any sprockets you have on the other side are then loose, too).

Not saying you should change your design; it's a minor concern. It's just that I've spent a lot of time servicing drives, and little details like this are worth thinking about, if nothing else.



Cool, that certainly would be harder to break.

Correct, Service of drives are definitely a pain. We got to the point this year where we could have our entire drive train dismantled (gearboxes off, axles off, bearing blocks out, belts off, sprockets off, motors unplugged) and back together again in less than the time it takes for us to be back to the field for our next elimination match, so about 12 or so minutes. We train our pit crew well and teach them that there are definitely trade-offs to running the type of setups we run. We do however consider all options prior to final design.

[Cash4587]

One thing I just noticed is that, there is no way to actually run this setup pictured. The gearboxes will need to be on opposite ends of the robot due to the axle length of the gearbox. This is not a problem, just will need to be re-worked.

[JesseK]

This is pretty nifty, but I would worry about the chain runs affecting the match-to-match reliability of 'drive straight' in autonomous.

Eventually the four wheels in the middle will make a trapezoid (or some other such non-square 4-sided shape) rather than a rectangle since the chains will stretch at different rates. This can be mitigated by directly running the chains from the gearbox to both sets of middle wheels. The typical WCD 6WD experiences this with nominal effects since the middle wheel locations are always constant.

The gearboxes will need to be on opposite ends of the robot due to the axle length of the gearbox.

If you have a lathe, could you cut the gearbox output shaft and re-tap the hole in the end?