Team Eventorizon: Build Diary

[overkill]

I would, except I have the attention span of a goldfish

[Eventorizon]

I decided to start on the electronics of my new spinner beetle. I knew everything needed to be tight and compact and given that I am running on 4S to get the most out of the weapon motor, this presented a few problems.

The first is that the 10A Botbitz don’t take more than 3S so that put them out for drive ESC’s. Second the battery was going to be quite a bit bigger than the 3S in Anvil and the other beetles which would make the chassis larger and thus heavier. Finally running full power on the weapon motor meant I needed to get the larger ESC, a 70A Red Brick, taking up more room and weight.

I was going to use the 12A-RC Sabertooth I had lying around from an old feather design but then I remembered… my Antweight. I had got a 5A-RC Sabertooth for an antweight that never made it beyond CAD.

Looking up the stats I was pleased to see that it took 4S and was far smaller than the 12A. 2 hours of staring at the parts later I ended up with this…

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After removing the Red heat shrink and the pressed Alu heat sink on the Sabertooth, I put some thermal compound on the 5A’s Fets and with a glue gun secured it to the top of the secondary heat sink on the Red Brick.

From that I ran wires from the Red Bricks power terminals up to the 5A to get power to it and simplify the wiring. After pre-attaching wires for the drive motors and grouping together the signal wires neatly I shrunk the two ESC's together into one compact unit.

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Sabertooths are known for not being too reliable in combat if they are not protected or reinforced. Here the heat shrink keeps the capacitor in place and I also added some extra glue to the base. All the internal wires are heat shrined together in pairs and clusters so any stress is spread across all the connection points and now rather than being over 35mm high the whole unit is now 27mm, just enough height left for some Velcro to go in the 30mm tall chassis.

There are some down sides to this design. Sharing heat sinks is one issue and possible overheating. Also if anything breaks it means the whole unit has to come apart which might take two long at an event. However this should be a good first version which I can improve on over time.

[harry hills]

Nice package (oo er) You might get some overheating issues with sharing a heatsink. That would be a worry for me.

I had more or less the same setup in eggbeater until the sabertooth died and I shoved the 10a botbitz back in, they were cooler than the sabertooth on 4s for me.

Looking forward to seeing some more beetle stuff

[maddox10]

After rereading.

Titanium bolts are comparable to 10.9 steel bolts. The weightdifference is only 3 grams on an M6x30 bolt.

Radii on machined pieces are a must. Even if previous experience gives the idea radii are overrated.

[Eventorizon]

The beetle arena build is drawing to a close so now I can actually start to think about other things, the first of which is our first non spinner robots.

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Going for small but strong. Dual GR01's driven by a Dual 25A Sabertooth, 6S 400mAh lipo as power and a 30V, 4500N, 100mm stroke actuator. I am torn at the moment between a 4 bar lifter and a crabber/crusher but that will mainly depend on what materials I can get my hands on. Unlike C3 and Binky this build will be more C1 and C2 style with HDPE and Polycarbonate making up most of the robot.

Will work on some CAD models but I think I will spend more time building prototypes in MDF this time as we now have an actual workshop space!

[Revsmin]

That Sabertooth's gonna blow. Seriously, get a Scorpion XXL or something, so much better.

[Eventorizon]

Provided you take care of them them are fine. MMM has run one for years with no issues. That and I am not forking out any more money. I got it for basically nothing so if it does blow then no hard done.

[Gabe01]

So I have in my stock x2 gr01's a 100mm actuator and the sabretooth only used for testing! Make me an offer

[Gabe01]

You might have them yourself already of course

[Eventorizon]

Got 2 of those actuators and enough TZ85A's if anything breaks.

[Gabe01]

Sweet

[Eventorizon]

Managed to get a long way in one day now I have started to work on building my first non-spinner featherweight.

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Had some odd things thrown at me that I didn't expect, but are all down to me not paying attention.

The 10mm HDPE base is 8mm thick, not a big issue. The side armour is 0.9 inches or 22.8mm, not the 20 like I ordered/assumed it would be.

The main issue is that what I thought was a block of HDPE for the side armour is actually Nylon 66. Given its not going against spinners it shouldn't shatter but its a bit of a pain and it has me slightly worried. It was originally intended as the base of a pneumatic machine that ended up being abandoned.

I can't decide if I should mill everything down to the 20mm its supposed to be or just leave the pieces as they are. Given the machine weighs just 9Kg in CAD, without the claw, I have loads to play with but at some point it needs a Srimec so pocketing out each piece will probably happen eventually anyway.

The claw will be fun to make. Initially just 2 sheets of 3mm mild steel welded into a tapered point, I hope that eventually I can make one out of a solid piece of steel so its stupidly strong and it will get me to practice my milling turn table skills.

[harry hills]

Plastic is nearly always oversize when you buy it.

[Eventorizon]

Yes, it does say that on the Direct Plastics website. I just remember it being 5% over sized not 15%, but hey, at least I have options.

[PJ-27]

Plastics can always retain water, try drying it out, might help a bit.