Farfle's electromotard. Mk. 4

That bike sounds awesome.

I found out why the motor stopped working in santa cruz. The axle twisted in the center aluminum stator support. It was only stopped by the hall sensor being pulled out of its slot.

Nevermind the two broken shear pin pin pieces flying around messing up the end lam stacks (thankfully left the windings untouched).

Should be fixable by mac track on friday. Hopefully.

The screen enclosure for the liquid cooling system is almost finished, just need to mill the lexan faceplate and paint it.The top line is for the infared temperature sensor that is pointed at the outside of the motor, and the second line is for the thermistor that is inside the motor (not connected in photo). When the temperature gets above a certain level a pump gets activated and sends water inside the motor, where the heat from the motor will turn it into steam, which will escape through the side vent holes. The membrance switches on the top will eventually be for changing the settings like the emissivity coefficient used for the IR sensor and the trigger temperature for the pump. Also have some LEDS that will turn on when the pump is on, tank is empty, etc.

Main enclosure is almost finished!

Bartimaeus said:

The screen enclosure for the liquid cooling system is almost finished, just need to mill the lexan faceplate and paint it.The top line is for the infared temperature sensor that is pointed at the outside of the motor, and the second line is for the thermistor that is inside the motor (not connected in photo). When the temperature gets above a certain level a pump gets activated and sends water inside the motor, where the heat from the motor will turn it into steam, which will escape through the side vent holes. The membrance switches on the top will eventually be for changing the settings like the emissivity coefficient used for the IR sensor and the trigger temperature for the pump. Also have some LEDS that will turn on when the pump is on, tank is empty, etc.

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None of the holes I see on your motor are at the perimeter, so any water that doesn't evaporate will be stuck with no way out of the motor. Unless I just haven't seen them next time you guys have the motor open you should make at least some small holes at the extreme perimeter of the magnet backing ring.

Evaporating 1 liter of water will take over 2 million joules of heat out with it, so over a 10 minute run that's an average of over 3.7kw, which sounds about right. My only question is the temp, because 100C is pretty hot to me, not failure type hot, but a few points loss of efficiency hot.

It's a neat rig, but let's compare to air cooling with heat capacity of air of 1 joule per gram per degree C and a density of 1.29 grams per liter, a 65° delta T (ambient to stator), and again a 10 minute run. You'd have to get almost 2700 liters of air through the motor per minute for similar cooling as the water evaporation. That seems like a lot, but it's only 95 cubic feet per minute and little 120mm computer fans can move that much air with just 4 watts, so a well designed centrifugal fan approach on a 30hp several krpm outrunner motor should easily get double or triple that through the motor. Plus the benefits of cooling are 100% of the time. There's also the active fan approach like Toolman2 took. He uses an 80W leaf blower to blast air through the motor...sure a lot more noise but nice and easy and you get 300-400 cfm without being dependent upon motor rpm. He calculated his 80W blower was reducing copper losses by 1000W.

The heat capacity and latent heat of water are always attractive for cooling, but with our electrics we have neither the delta T's nor the overall heat to dissipate to make it worthwhile IMHO. Look at my near silent unoptimized approach which keeping stator temps below 85°C on a 22km ride of mixed riding, and with some changes I expect to get that in the 70's with no sensors or switches or electronics of any kind to fail. That's with a hubmotor, so much lower rpm than your mid-drive, and pushing a much heavier load too, so imagine your higher rpm motor. I prefer to keep liquids away from electronics anyway.

John

Heya john, thanks for your input, the reason I went with the liquid spray cooling is because I had hard data on its excellent effect on agni motors, which are aggressively fan cooled spinning at a much higher rpm. Is it more effective? I have no idea, but we can displace the entire motors air volume with water in only a few seconds, which is an impressive sight spinning at 3k. As far as letting the water out, I want the only way it can exit the motor to be as steam, but we do have some 1/8" holes around the magnet ring perimeter that can be plugged/unplugged to drain the water when stationary. Most motors can take 150C continuous, and short excursions to 180-200C are ok as long as the magnets and sensors stay cool. This motors temp should be hard capped to 100ish C.

Yeah if you're running hot like that then a water dump, which sounds pretty impressive, makes sense, and you already have the drain holes handled. I guess I need to get past being so averse to water in the motor, because at this point I'd rather pour a glass of water on my batteries which I know are pretty well sealed than in a hot motor. I've seen the after effects of water in hubbies. It ain't pretty, and even with good coatings, none seem hard enough to protect the end lams during reassembly. I think I need to see an open brushless motor running in salt water to change my mind.

When's the next race?

Really long two days. Both Farfle and I were running on four hours or less of sleep to get the bike ready for the track day. I can't even begin to cover all of the stuff that went wrong, got fixed, built, re-built, etc. right now, I'm going to bed. But here's the pictures from the event:
https://drive.google.com/folderview?id=0B3Y-BPL3nguXNm9kUWdzQlN6dlU&usp=sharing

Farfle has the onboard video with him and is still driving home.

So Farfle decided to re-wind the motor this week before REFUEL. Apparently one of the phases was partially shorted to the frame... He's got the Nomex paper set up already:

Looking fast, Team Farfle

So, water cooling = closed loop, total loss or puke tank?

Just trying to figure out which side to pass you on :wink:

I wish I could be racing with you guys at ReFuel on my home track. I leaving for China tomorrow and not going to be back from China until next Monday. ;-(

Farfle got the motor rewound in record time! He worked from 5:30-1:30 last night and power blasted through! Here's the photos:
https://www.facebook.com/media/set/?set=a.523877414328611.1073741834.508018925914460&type=1

Congrats!!!

More copper this time?

h0tr0d said:

Congrats!!!

More copper this time?

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Sadly no, even though I would love to cram in a few extra strands, the Sevcon is tuned for a 15x3 wind, and I can't change it without risking a re-tune. Which isn't going to happen in three days.

liveforphysics said:

I wish I could be racing with you guys at ReFuel on my home track. I leaving for China tomorrow and not going to be back from China until next Monday. ;-(

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Dang, That sucks man.. Will probably see you at am M1GP race sometime in the future though.

A quick teaser of the practice trackday we just did.

I hope there's some footage from that GoPro (looks like it is an empty shell?)
Looks awesome - is traction an issue?

Woo! On the road to laguna seca. With T-shirts!

Refuel was AWESOME. the bike got BEAT, and its going to need some work to get it back up and running. We had multiple failures of both the main and redundant liquid cooling systems, one of which sprayed water all over the rear tire causing us to crash once. For the record, the best plastic for sliders is UHMW. Even having to turn the power down, the fastest recorded lap we had was a 2:20, and the fastest un-recorded lap was around 2:13. Here's some shots for you guys, we have some great gopro footage too, but It is stil dumping.

There's some pics posted to the Facebook page that you guys can check out: https://www.facebook.com/media/set/?set=a.527466713969681.1073741836.508018925914460&type=3

Here are a few pictures from the event: *edit* looks like bart beat me to it.

Just did a short practice day at pats acres, and got a surprise visit by a local forum member and his family (Thepronghorn). Sadly we ended the day with a pretty bad crash that thankfully bartimeaus walked away from, but the bike is going to need some work. Not sure how, but we managed to break the master cylinder, and bend the bars pretty good. .

Farfle said:

Not sure how, but we managed to break the master cylinder, and bend the bars pretty good. .

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There's always something....

Looking good!

are you using the rubber mounts for the bar clamps into the tripple clamp? Amount of times I have seen people buy new bars because the bars come out of shape in the clamps..... . Looking forward to some footage

rodgah said:

are you using the rubber mounts for the bar clamps into the tripple clamp? Amount of times I have seen people buy new bars because the bars come out of shape in the clamps..... . Looking forward to some footage

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Need to get some, I removed the old cracked gnarly ones thinking they were for vibration. Didn't really think about the bars lol.

In other news, we have been doing more weekend trackdays with the local gas supermoto crowd, and recently had a ton of fun at horn rapids MX park in the tri-city area. We made a last minute suspension change, as I had misread the race tech book for setting up sag. I read 25-35mm, it was actually 25-35% with that change made, the bike rode better, but the biggest improvement was that we kept the bike shiny side up the entire day. (Breaking a 5 trackday crash streak). Barty was able to flog the bike hard enough to make the motor clear 270 C (that double insulated winding wire is awesome