Quote:
Originally Posted by thefro526
In my experience, the big secret to keeping weight in check is to start losing it in the design phase. After an experience in 2011, where the team I was with at the time needed to 'find' 3lbs or so before our second event, I've been actively trying to design everything I'm involved in to be as light and efficient as possible from the beginning.
Some of my favorite techniques are:
- Use 10-32 SHCS/BHCS and 1/8" Rivets as standard hardware instead of 1/4-20. Most of the time, especially in FRC, 1/4-20 is used in situations where it's way overkill. Swapping out a 1/4-20 Bolt for a 10-32 nets ~20% weight savings per fastener, which adds up over time.
- Use 1/16" Wall Extrusions when possible instead of the standard 1/8". There are numerous instances where I see 1/8" Wall Extrusions used because they're common and 'easy to find' - but aren't really needed. Swapping this out to the equivalent extrusion in 1/16" Wall thickness nets a ~50% savings. (* try to avoid thin 6063 extrusions though, sometimes they end up being a nightmare)
- Use .060 (nominal) Wall 6061 Tubing instead of PVC/ABS/Etc for rollers. This can really add up on a system with a lot of rollers.
- Swap out larger gears in COTS transmissions for their aluminum equivalent. West Coast Products makes 7075 versions of many of the AM gears, swapping out two or three gears can add up to a pound of weight savings really, really quickly.
- Avoid thick polycarbonate and other plastics. Many people think that because plastics are relatively light, they can get away with using thicker sheets which often leads to 'hidden weight'.
The list goes on and on from here, but I hope you get the idea. Also, sometimes, it's worth trying the 'lighter' version of something first. If it fails, you'll know that you can easily replace it with something stronger/heavier. If you do the opposite, sometimes it's hard to replace that part because it's been on the machine for too long and/or is too well integrated to make it easy.
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All of this x2.
We use these techniques and am critical of every component's weight as we make them. We ask questions like: does this sheet really need to be 0.125in or can it be 0.100in? Can we use smaller or shorter bolts? Can this part perform multiple functions? Can we weld it instead of using fasteners? I.e. welding a kit frame drops 3+lbs of brackets and fasteners.
Material selection, even subtle differentiation, can be very important. For example, instead of going to HomeDepot and getting 1/8x1x1 6063 aluminum angle, order 1/16x1x1 6061 angle from McMaster. It's just as strong and half the weight. Where stiffness is important we use *gasp* steel!
Using these sorts of practices since 2010 we've been underweight by 5-15lbs without a weight budget, serious CAD'ing, or removing any mechanisms.
Edit:
FWIW we also up-size motor wire, i.e. instead of 12awg we use 10awg.
Don't forget that pounds are made of ounces, when you start dropping ounces whenever possible good things happen. To paraphrase Talladega Nights: "If you're not reducing weight, you're adding it."