pic: Team 449 Hex Drive

[AdamHeard]

I think Andrew's point is best summarized as this drivetrain has two complete, independent frames that are likely strong enough on their own. If they were better integrated, a lot of framing could be eliminated.

The support for the angles also doesn't even need to be a separate frame. For a very minimal (and very strong support), see what we did here.

[nuclearnerd]

I wonder if anyone has thought about anti-anti-tpinning frames It seems to me that if your opponents front bumper were split in two (as shown on the top side of the diagram below), they might easily "straddle" the side points of your hexagon making it just as hard (maybe harder?) to get out of a T-pin as a straight side would be.


This isn't a critique of your design directly - lots of teams have been experimenting with hexagonal bases recently

[hzheng_449]

We considered integrating the angle supports into the base frame, but we didn't like how much real estate the supports we considered would take on the 2x1.

Although having a raised secondary frame is heavier, we like the fact that it gives us more vertical space to place pneumatics and electronics. (Our robot for last season was a bit of a mess in terms of packing and that experience heavily influenced this drive's design process).

Additionally, we're at least trying to mitigate the weight gain from the hex superstructure by fabricating the base and inner rails on the superstructure with 2"x1"x1/16" and 1"x1"x1/16" (we normally use 1/8").

Also we're using versawheels mostly to experiment with how well they perform compared to colsons. It's an experimental offseason project, and we figured we may as well try out as many new features as possible.

[Cash4587]

Originally Posted by nuclearnerd

I wonder if anyone has thought about anti-anti-tpinning frames It seems to me that if your opponents front bumper were split in two (as shown on the top side of the diagram below), they might easily "straddle" the side points of your hexagon making it just as hard (maybe harder?) to get out of a T-pin as a straight side would be.


This isn't a critique of your design directly - lots of teams have been experimenting with hexagonal bases recently

My team this year had a cutout in the front bumper like you drew. It seemed to be somewhat effective to reduce the effects of teams hex drives. (our bumper cutout gap was 11" to make room for our arm when in the down position) However we really only had the chance to use it against 148 whose hex sides weren't as large as some other teams. In order to prove that the cutout really was effective in this aspect we would have liked to try it out on some different angled hex chassis. I don't know if any other teams can attest to this being an effective way to reduce the usefulness of a hex chassis, but please chime in if you have any other ideas on this.

[Oblarg]

Originally Posted by Cash4587

My team this year had a cutout in the front bumper like you drew. It seemed to be somewhat effective to reduce the effects of teams hex drives. (our bumper cutout gap was 11" to make room for our arm when in the down position) However we really only had the chance to use it against 148 whose hex sides weren't as large as some other teams. In order to prove that the cutout really was effective in this aspect we would have liked to try it out on some different angled hex chassis. I don't know if any other teams can attest to this being an effective way to reduce the usefulness of a hex chassis, but please chime in if you have any other ideas on this.

I think a hex chassis would still see some benefit in situations up against a wall, since they still have a point to pivot around where the frame contacts the wall (where a rectangular chassis would not).

Obviously, I have no way to test this at the moment. It'd be nice to play around with a few actual bots and see how the different situations pan out.

[Oblarg]

Originally Posted by AdamHeard

I think Andrew's point is best summarized as this drivetrain has two complete, independent frames that are likely strong enough on their own. If they were better integrated, a lot of framing could be eliminated.

The support for the angles also doesn't even need to be a separate frame. For a very minimal (and very strong support), see what we did here.

These are good points, and we considered them while designing this.

Mainly, we decided that while a single frame is simpler, it makes it harder to really make use of the extra area provided by a hex frame (the picture you've linked shows this pretty well, as pretty much everything is contained in the inner rectangular frame. It also complicates wheel access, which is one of the primary selling points of a WCD.

[AdamHeard]

Originally Posted by Oblarg

These are good points, and we considered them while designing this.

Mainly, we decided that while a single frame is simpler, it makes it harder to really make use of the extra area provided by a hex frame (the picture you've linked shows this pretty well, as pretty much everything is contained in the inner rectangular frame. It also complicates wheel access, which is one of the primary selling points of a WCD.

You wouldn't have to put the wheels internal like we did to do the simpler bumper support.

[Oblarg]

Originally Posted by AdamHeard

You wouldn't have to put the wheels internal like we did to do the simpler bumper support.

No, but you would have to make the inner rectangular frame smaller, shorten the wheelbase slightly, and complicate access.

[aldaeron]

Great post - thanks for sharing. Also thanks to all those sharing CAD archives that show off hex/oct chassis.

I asked Vex if they would add a 22.5 gusset offering to their VersaChassis line. It would allow those of us without a sheet metal sponsor to build something like this with minimal tools.

-matto-

Originally Posted by aldaeron

Great post - thanks for sharing. Also thanks to all those sharing CAD archives that show off hex/oct chassis.

I asked Vex if they would add a 22.5 gusset offering to their VersaChassis line. It would allow those of us without a sheet metal sponsor to build something like this with minimal tools.

-matto-

Could you clarify what a 22.5 gusset is?

[aldaeron]

Originally Posted by Andrew Lawrence

Could you clarify what a 22.5 gusset is?

Apologies - can't post a pic on a Pic thread apparently =P

http://imgur.com/dkk6jLg

I meant a 22.5 degree gusset. Put one on either end and the existing 135 degree gusset in the center, add some 2x1 VersaFrame and you have a quick hex chassis like the OP showed.

-matto-

[Oblarg]

Originally Posted by aldaeron

Great post - thanks for sharing. Also thanks to all those sharing CAD archives that show off hex/oct chassis.

I asked Vex if they would add a 22.5 gusset offering to their VersaChassis line. It would allow those of us without a sheet metal sponsor to build something like this with minimal tools.

-matto-

449 doesn't have a sheet metal sponsor or access to a CNC mill, actually. We do all our machining by hand with a drill press, miter saw, and band saw.

However, we do have access to a laser cutter that can do delrin, which allows us to make precise templates for our gussets that we can then use to match-drill.