We have some ideas for getting rid of some of the weight and support the second stage when it’t fully extended. We just wanted to see if there were any suggestions on what we could do without rebuilding the intake
This is highly dependent on your axle loads, but also consider swapping hex axles for Churro. At 0.16 lbs/ft, it is appreciably lighter than regular hex shaft (0.27 lbs/ft). (3/8" is 0.15 lbs/ft, which is not zero but is definitely diminishing returns since you’d be swapping a lot of stuff out for the new bore.)
If you can’t run belts, at least consider #25 chain.
If you can’t use rivets (and please, give real thought to using them), at least keep the bolts as short as they can be. Hard to say what you’re using by the pictures, but I like #10s for situations where things may get a little rough.
The outer arms as mounted have the chain running below the compliant wheel. Can the complaint wheel go on the bottom? That would let you shorten up one shaft significantly.
And while you had trouble with lexan rigidity, consider lexan with a bent flange or lexan reinforced in the necessary places to stiffen it up. A thin piece of angle can add quite a bit of rigidity (indeed, that’s how FIRST did it on the hoppers on last year’s field).
What is the whole robot likely to weigh now? It looks incomplete so just pile on the components that are not yet installed and add a few pieces of sheet and tubing to approximate other mechanisms you have yet to build. Reducing the weight of your intake by, say, 3 pounds will take a fair amount of effort but it will be a nasty surprise if your total robot weight happens to be 20 pounds too high. On the other hand, if you are 20 pounds under the limit, you know you can do things like add a stronger structure to hold your intake and/or add motors to lift it.
If you are using 1/8" wall tubing, you might be able to replace it with 1/16" tubing to save a small amount of weight. Test thoroughly before committing to ensure it is still strong enough under all conditions.
Some of this reiterates what’s said above, some of it doesn’t:
You have way more structure there than you need – plate with lots of lightening holes, spaced with standoffs, will be shockingly strong (and will allow you to get rid of the box tubing on the central piece altogether).
Ditch the shaft collars, retaining bolts, and washers in favor of clip rings (you’ll need a lathe*, but once you start doing this you’ll never go back.)
Those other shaft collars can be replaced with nylon or PVC spacers (you can buy them or just cut them to size out of a piece of PVC–the latter is ugly but fast and functional) OR with more grooves and clip rings to hold everything right where you want it. (I prefer spacers for spacing, because it is both faster and more adjustable, especially when you have lots of spacers in lots of sizes to choose from, but clip rings will be lighter.)
Ditch the wide box tube on the arms in favor of 1" box with VexPro end effector gussets.
Ditch the bolts for rivets.
Use belt instead of chain if you can, and if you can’t, use lighter chain.
Use BAG motors–they’re light and plenty strong to do the job on an intake.
All that said, once you’ve lightened that as much as possible, you’re going to be adding the weight of a crate and then driving around/getting hammered by other robots, so if your lift mechanism is straining under the weight right now it may definitely strain under those conditions even with a lighter mechanism, so you might want to consider a redesign to a stronger lift.
*you can cut clip ring grooves with a drill press and a hacksaw, but I wouldn’t recommend it
This style design was really effective for those large totes in recycle rush but I wonder if it may be a bit overkill for these powercubes. In some of our early testing just two wheels on a spring loaded arm was surprisingly effective. Take a look at the many videos available from Ri3D, etc. Just remember any extra weight up high really puts you at risk for tipping over.
swiss cheeseing with a drill could start to get your weight down, I also like the polycarb idea, Polycarb could also add some flex to your intake to make up for the strength lost by swiching from aluminum.