Thanks Tommy!
I have a bit of backlog of updates I have written but haven't posted:
Unposted writeup after clutch failure
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It looks like I'll be pulling the motor this weekend. I took the tow'd out for another test yesterday, and yeah my burnout runs broke the clutch. It holds fine at normal power levels, but it immediately slips/stinks when I stomp on the pedal. The clutch lever only goes about 1/3 down, but does not actually release the clutch. I can't really picture what failures would cause this, maybe some snapped fingers on the pressure plate? Anyhow, if things are breaking under load I know I am doing something right, power wise. A co-worker recommended I look at a Kennedy Engineering Clutch/pressure plate that can handle the torque loads, they did a good job with my flywheel so I will probably go that route. Once the clutch is squared away, I wonder if the tranny or the axles will be the next to go...
I ordered the
Cobalt MJ-1200 submersible pump that Otmar recommends for the cooling system. Once an industry standard, I found many reports of those pumps failing, underperforming, vibrating and being noisy after production was moved to China. Luckily, I found that "Cobalt Aquatics" sources the original version of the MJ-1200 from the original italian manufacturer, I hope it lives up to the glowing reviews. The chinese version is half the price, but you get what you paid for.
The MJ-1200 uses 20 watts to pump 295gph with 69" of head pressure. I was tempted to use the MJ-900 instead, which uses only 8.5w to pump a respectable 230GPH - double the zilla's requirements - with 46" of head pressure. I decided the 135% power consumption penalty was worth the 50% increase in head pressure - better too much than too little.
I used to have an inverter at the dash that powered fans for the kelly. That inverter will be remounted in the trunk next to the (still-to-be-determined) reservoir/overflow tanks, energized by the same switch that powered the fans. No idea what radiator I am going to use, or where it will go, but they will exist.
Unposted writeup of Z2K vs Z1K
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Everything I learned about DC motors came from experience with Brushless/BLDC on ebikes, so one of the challenges has been learning the different parameters around brushed series motors. I am going to spew out an overview of what I think I understand today, a little of it comes from experience but most of is it regurgitating what I have read so there will be flaws.
For example, I thought that Series motors do not have back EMF, because without load they can quickly spin up to bearing-killing speeds. However, back-EMF does exist. BackEMF increases with RPMs and restricts the amps, which decreases torque until it meets current load and cannot increase RPMs any more.
Amps define torque, it will remain constant no matter what the voltage is. Since a portion of amps is converted to heat, increasing amps requires more motor cooling. This is a particular problem at launch, when efficiency is low and amps are generating more heat than power and can quickly saturate the motor. The brush/commutator interface has a limit to how many amps it can handle before a flashover event.
As RPMs increase so does efficiency, so less amps are wasted as heat. However, BackEMF also increases until the motor can't take in enough amps to increase RPMs. There are two ways to decrease BackEMF - increase the voltage, or run a smaller motor. However, overvolting is highly limited by the brush/commutator interface as well as motor timing. Better brushes, better brush surfacing, and better patina on the commutator will let you increase voltage a little, but not double it like I could with a BLDC motor. Changing the timing also helps the motor run more effectively at a higher voltage, but push the volts too hard and a flashover can destroy your motor.
Smaller motors generate less backEMF and less torque/amp, but deliver torque at higher RPMs, but the smaller commutator can handle less voltage. The larger motor will deliver more torque/amp, and can run at a higher voltage, but backEMF restricts amps earlier.
With Brushes limiting volts, and backEMF limiting amps there is an upper limit on how many watts a given series motor can handle, and for how long. Otmar (the creator of the zilla) recommended a street conversion with 8"/9" motor be run 500a-600a and 150-160v. I have read that the 9" Netgain Warp motor will survive 1,000a for 10 seconds, and Netgain rates their Warp 9 at 170v with Helwig brushes, and some drag racers mention running 196v. So with compromises, short runs, well-detailed equipment and good cooling, a bit more power can be had. A larger 11" or 13" motor can also handle more power too.
However, the 1,600a/400v that the Z2K's "EHV" version can supply is way more than typical series motors can handle, so what is the point? I think it is to run dual motors. The Zilla can drive contactors that switch dual motors between Parallel and Serial configurations in 0.3 seconds. In parallel mode, dual motors split the amps, so the 1,600a translates to a manageble 800a each. In series mode, the dual motors split the volts, so 400v translates to a manageble 200v each.
Battery Sag is another reason to run high voltage, especially on the Lead-Acid cells common when the zilla was developed. The zilla is not a boost converter, so Motor Volts will never exceed Battery Volts. If your 150v pack sags to 130v, the motor will see that 130v, not the 150v you programmed. However, the zilla _IS_ a buck converter that can reduce pack voltage, so if you have a 300v pack and program motor volts to 150v, the motor will see 150v. If your battery sags to 200v, the motor will still see 150v.
That said, the Z2K is clearly way more controller than the tow'd will ever be able to use. The smaller Z1K-HV would be more appropriate - capable of the 1,000a that would toast the motor in 10 seconds, and at 300v it has plenty of headroom to accomodate pack sag. Having too much controller means it can tolerate greater abuse, and it provides greater thermal mass so it can run longer without proper cooling. However, the z2k weighs and costs twice as much as the Z1K, so I could reduce weight and sunk cost with a Z1K.