All,
So as I understand it the last of our components necessary to make a working racer are about in place. There will definitely be pieces that we didn’t think about getting as we build, but that’s OK. (By the way, if anyone else wants to get involved please speak up, it’s definitely not too late to help and learn something!) I realize this weekend is maker faire, so most of this will be happening throughout next week. I will be out of town on Friday but I would still like to have the official meeting on Wednesday and if someone will set up a Google hangout I’ll join in that way.
First- on the list is to finish the chassis modeling. Franklin started the model, but now we can finish it by modeling the wheels and the casters to hold the front wheels. The bearings for the front casters should be in by this weekend. With that said, once the frame model is completed there’s no reason we can’t actually start cutting metal!
What to do:
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Model wheels
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Model casters for holding front wheels
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Model mounts for rear wheels (essentially it should be an assembly that can be screwed on and off for tire changes)
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Finish frame model
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Check model over
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Measure and cut tubing
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Weld
Second- Batteries. We have lots of batteries. We need to exercise the batteries as they’ve been sitting for a while, This will require some creativity because we need to figure out what their capacity is AND balance the batteries for assembling in to packs. We cannot safely do all packs at the same time so we’re going to have to get creative. The charger I have cannot manage high discharge rates as the cooling required to dissipate the heat can become absurd. We should instead build a simple arduino circuit that discharges the batteries (and stops!) by using a set of the 6V floodlights Will brought in as a load.
We need help keeping this going as this process will take a long time. I would love assistance in making sure the batteries keep cycling so that this process won’t take weeks
What to do:
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Build a relay circuit triggered by the arduino (there are plenty of examples online)
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Build a voltage divider to scale each stick’s voltage below 5v for measurement by the arduino. (Also plenty of examples online)
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Have the relay power a bank of the 6v floodlights in parallel equal to the number of charged battery sticks in parallel.
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Make code to turn the floodlights on if the stick(s) actual (not divided) voltage is above 5v, and turn off if below. (we don’t want any of the individual cells in the sticks to go below 1v)
For charging the batteries we need to:
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Pick out 3 unmarked sticks from the bucket, measure with Voltmeter and ensure all are within .01v (should all be at 5v). If it is below 5V significantly, set aside and mark “BAD”
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Charge 3 sticks in series (15 cells) at 5A Note that one end of the stick has a plus shaped tab and the other has a negative shaped tab. use screw plates and screws in the bag next to batteries to attach the leads together.
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Mark each cell with the mAh displayed when finished charging in sharpie We should be seeing about 7500mAh when charging from empty.
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stick the newly marked, charged batteries in parallel and discharge. If the stick set showed lower than 7000mAh when charging, rewire into a series pack and charge, repeat 3x if necessary, if still out of range set the 3 battery sticks aside in a box for “BAD cells”
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Repeat, it takes about 1.5-2hr to charge a pack and should take about as long to discharge, we have 50 sticks to go through…
I’ll try and make space and instructions for this so anyone that wants to stop by and change batteries can.
Third Races are OCT 4-5th, We need to start planning who is going! If you’d like to go please post and let me know! We’re going to start talking logistics and hotels here shortly!
If you would like to help with something specific please let me know!
