I apologize for how long it's been since I've done a status update on the bots. I've been really busy planning the trip logistics....Anyways, the shell for the 15 pounder is done. it weighs 4.15 lbs (down from 4.55). We drilled well over a hundred
holes in it. The shell itself is slightly concerning because it is really soft. We're gonna go for broke, and if it breaks in miami, then we look for a plan B. The weapon motor assemblies are being difficult. First problem was the bearing supports... The barstock was undersized 3/8" but we didn't know it was so undersized - we drew a "center" line at 3/16" for the two mounting holes and put each piece in the vice with a stop - drilled one hole, took it out, flipped it around, and drilled the second hole. The barstock was actually .362 or somewhere around there so the holes make a diagonal across the part instead of a straight, perpendicular line. This is really bad because these are the supports that hold the bearings parallel with the motor shafts! If these aren't square, the motors will constantly be fighting to spin up. With this problem finally solved by enlarging one of the two countersunk holes in the baseplates, we starting putting the assemblies together, only to find that the tolerances had stacked up so much that things didn't line up. The motor shaft would stub the end of the adapter, and wouldn't go in right. We had to modify each assembly individually to get everything to line up, and even then, we ruined several bearings, and only produced six that spin really well. We got two that were okay, and left two in pieces because we didn't have time last night to perfect them. That's why we're gonna be out there ALL DAY saturday...
So if you want to swing by and help, or your parents want to come by and see what we're doing, feel free. It's kind of like an open house type day. One of our wheels is done, it looks really good, and since it's made of 7075 aluminum, it'll be very strong. (This photo is an unfinished wheel blank - sorry I don't have a photo of one finished).Last week when we weighed everything, the total (without baseplate, fasteners, and electronics) was 18.4 pounds. This is a very intimidating figure because there really isn't much we can lighten, but I think we'll be okay if we use 8 motors instead of 10. We've already dropped almost 2 pounds, so things are looking good. We need to get this thing put together and running ASAP so that we can do the necessary testing to see if there are any changes that need to be made.
As far as Copperhead goes, we cut out the back corners - saving almost a pound. It took a long time, but it looks good. SMT agreed to machine our wheels for us for free, so we sent them the material to use - I just need to finish my solidworks drawing of the wheels (normally I use AutoCAD 2000 so this is an awkward, unfamiliar software for me, so it's taking FOREVER). We also decided to thin out the wheel design. The tires machine fairly well, so we are thinning them out from 1.75" to 1.5" to save some more weight...
I bought a new IMX1 mixer from RobotMarketplace to replace the old one that we burnt out - now everything works as it should. If we can raise enough money, I would like to use either stainless or titanium for armor this year instead of lexan, because there are kill saws in the arena, and we need to survive ANYTHING. This is televised! We are the ones to beat! Copperhead needs to be indestructable.
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