When I received our first VEX kits, I was disappointed when I looked at the battery box / tie downs for the 7.2V battery that were included. I know they recently developed newer tie downs, but they are not that great either. Back in the day, I used to do a little RC racing and Associated had something called Battery Cups that allow for super fast changes, but also provide a very secure mount. I have ordered these from Tower Hobbies and we modify them slightly to allow the new batteries to fit and we use them on our classroom robots, but take them off to compete. My students complain because the vex tie-downs are harder to swap batteries and reliability goes down as the batteries occasionally shift and disconnect from the controller. I suggest looking into making these a standard part or redesigning them slightly so the new batteries fit easier and packaging them as a VEX product. The holes match up with VEX and you simply use a button head screws instead of the countersink screws provided. http://pics.towerhobbies.com/image/a/ascc4335.jpg
I’ve broken both of my tie-downs supplied with the rechargable battery kit, because of some weaknessess in the design (battery only supported on one side), so now i use either zip ties or a cut and bent 1x25 bar to hold down the batteries. I refused to buy more because Vex tie-downs because 1.) Vex doesn’t provide shipping through the US postal service, so I have to pay $10 to ship a very small item. Vex, please add the cheap postal service for small orders! 2.) If I buy more, those will probably break too.
So, for the sake of competition use, I would second the notion of adding these battery cups or something similar to the vex line-up.
I prefer to use a pair of battery tie-downs, which prevents damage due to the battery torquing around as the robot turns.
Also, I’ve successfully used these garden-tool holders as a quick-change battery holder.
They work very well (use them in pairs), though they can mark the sides of the battery pack a bit.
The Velcro cinch straps work well for me (plus a short piece of C-Channel or a couple stand-offs to use as a brace/fence).
Some folk have complained that they broke the straps on their robots but mine have held up fine.
If you really want/need more strength than the cinch straps can supply, buy a roll of the 5’ x 1" wide Velcro and cut it into the lengths you need.
What about latex? you can double or triple it up and then just stretch it to get batteries in or out
Personally tightening two of the battery straps down on the blue part so that they are smaller than the black battery ends has always worked for me, even on robots that invert themselves and other fun stuff like that.
I always tried to place batteries firstly where counterbalancing for something was needed and secondly where it was secure and bound by at least one side of the robot from moving. I’ve used the tie downs on every robot ever, putting the battery in very vulnerable places and it’s never come out.
Sounds like a great idea. We’ve tried most of the ideas others have listed and none are completely satisfactory. For those that can’t see it the picture is here:
and the item is here: