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Originally posted by SharkBite
we desperately need to cut down some weight, does anyone know any tricks to do so (besides drilling speed holes)
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The trick is to do some math.
We had to lose a lot of weight last year. We tried to do it as systematically as possible and it worked very well. You really need to find the densities of the materials you are using and do some calculations.
An easy way to get started isto determine the weight of a 1" long piece of the most common materials on your robot. For instance, you can say that each inch of aluminum tube is X lb, each inch of steel bar is Y lb, and each inch of 1x1 8020 is Z lb, etc. This will give you an immediate idea of what you're up against and allows you to determine roughly how much material you need to remove to lose the necessary weight. It also gives you an idea of how much "bang for the buck" you get by removing one thing vs. another.
Usually, you won't be able to get rid of an aluminum bar because it is supporting something. Then you need to think to yourself, what if we cut it in half lengthwise and make it an aluminum channel? Will it still work? If so, calculate how much weight you save. We were able to turn enough square tubes into channels last year to save about 5 lb. We didn't turn the entire tube into a channel (we left the ends square for mounting reasons), but we made the middle section a channel.
Also, holes are very inefficient for removing weight. You can do much better in terms of weight loss with little reduction in strength by making slots or pockets instead of holes. For instance, if you are planning on doing holes, run a mill between every other hole to make a slot or pocket. If the member doesn't carry a lot of load, connect three or four holes in a row. You'll be amazed at how much more weight you remove by doing this rather than by simply doing holes.
Another HUGE saving comes from sprockets, pulleys, and gears. You can usually remove about 1/2 to 3/4 of the material in a sprocket, gear, or pulley if you do it properly. If we left the gears and pulleys on our robot for this year the way the came off-the-shelf, our robot would be about 5 lbs heavier.
There's no reason to use a solid steel gear like they come. Take off a good portion of the hub. Mill spokes from the hub to the gear face instead of leaving it solid. Also, if the face of the gear is 1/2 inch, there is no reason that the material from the hub to the face has to be 1/2 inch - usually you can thin this out significantly (just remember to leave the face at the necessary thickness).
I hope this helps. The most important thing is to do some calculations and have a plan before you start to reduce weight. We lost a total of 15 lb last year without losting any functionality or robustness. We made sure we had a good plan and did some math first. It worked really well.