Going Down in Flames – It’s Just an Expression

Interesting week last week and growing interestingier as we start this one.

Last Monday, we were doing some range testing at 60 mph in the eCobra when the Netgain Warp 11HV let out all its smoke and ceased operation somewhat noisily.

This led to a crusade to swap the motor that I’m more than a bit pleased with as it was pretty much completed in three days. Netgain had a new motor to us in less than 48 hours and our penchant for installing and reinstalling things several times had of course led us to a pretty straight forward replacement from beneath without having to move too many other parts – transmission and drive shaft of course. But no batteries or major rewiring.

Unfortunately, we had no video camera operating at the time. So no cool video of the tower of smoke next to the Interstate. Oh well….

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The other interesting thing to happen early THIS week is that we put the hood on the car. This is normally a not particularly exciting evolution and always toward the end of the build, when we are doing more driving that building.

In this case, it had a very strong effect. Recall I had been grousing about the rolling resistance, the brakes, and so forth on this car because it was taking between 1.65 and 2.25 Ah of energy at 215 volts to make a mile of distance. This is just horrendous. At the upper end this is like 475 wH per mile or more. And it had shot all my range calculations completely out of the saddle.

Actually, things get better with the hood on. This should be obvious to all, but I didn’t think it would account for this much difference. It makes THIS much difference. As soon as the hood was on, we dropped to 1.409 Ah per mile – right in the 300 wH per mile range where this 2961 lb car should be.

I may have mentioned some efforts to develop something more consistent than our soap box derby for a coast down test.

We took the car up to 75 mph on a flat road section and put it into neutral. Time mark 0 was called at 70mph and the time noted at each 10 mph until stopped. We ran this three times in each direction, east and west, and then averaged the results.

The coast down test is conventionally used to determine aerodynamic drag and rolling resistance. But it is difficult to do that with accuracy and requires humidity, temperature, and other factors to be truly accurate. But we think we can do a quick average procedure and have the curve and times as a baseline. This should let us compare to this baseline after changes for example. We’ll put on the original tires and rerun it for example to see what the effect is.

This is a bit more trouble than rolling it down the street in front of the shop. But accounts for aerodynamics in addition to rolling resistance and drive train efficiencies.

Jack Rickard


31 thoughts on “Going Down in Flames – It’s Just an Expression”

  1. You may remember Jack, that I had a similar experience to yours with my WarP11 motor. The difference was when the balancing putty came off of my motor, it simply started to vibrate the drive line; no plumes of smoke or drama. I guess you can chalk that up to difference between the standard versus the HV versions. But I also found that George and Netgain were simply spectacular with their customer support. They arranged all the shipping and repairs, and I had the motor back in just over two weeks. George had personally driven down to Warfield Electric to discuss what was causing the putty to come off my motor.

    As I’d explained to him, the motor has never seen higher than 5000 RPM (in all likelihood, it’s never been over 4250) so that was ruled out as a possible cause. He suspected heat might be the cause, but as I have a fan forcing air into the motor, and it happened in January when the air was nice and cool, that was summarily dismissed as well. I had the motor mounted to the chassis in such a way that it had little in the way of isolating shock absorption, but he didn’t think that should have been factor. As it was, they’d only ever seen ONE other putty failure and that was with someone who spun their motor to 9000 RPM! It was just a big mystery.

    Warfield and George began to suspect the putty itself, But reasoned that if it was the putty, they’d be seeing more failures. Even so, they asked that when I ship the motor back to them if I would include some of the putty I found inside the motor case so they could analyze it. Hearing that they’ve switched to a different kind of putty makes me think they found something they didn’t like. Or, perhaps they were simply able to source a putty they think is better. In either case, it’s clear they took this extremely rare failure very seriously. Taking this kind of action speaks highly of Netgain’s commitment to quality control.

    In the mean time, I’ve altered my motor mount to provide more isolating rubber cushion between the chassis and the motor, just to be safe. The motor is spinning beautifully with absolutely no vibration in the drive line. Balancing the flywheel and pressure plate combo was well worth the time and $90.

  2. Mass, air resistance and rolling resistance are the only reasons beyond the motor why humongous mileages evade us.

    Someone will say it. The original spoiler (me). Your air intake looks like a bit of a wall too.
    Considered a front grill and internal nose cone against the battery box and maybe the radiator angled?
    Oh, and your blower on a thermostat.
    Now for a change of subject that piqued my attention.
    I was reading a local rag and for no reason they had a write-up on an ev… Thought a minute… But they used a puht-puht engine right? Not any more!
    The Progressive X-Prize contender “Edison2” have now moved over to electric. A 10.8KwH pack which now takes the little car 245 miles on a run. It’s a bit of a Dan Fredrikson copy but works!
    I’m sure Jack will dislike the shiny silvered aluminium body work too.


    Their cool blog with informative consumption data is here: http://www.edison2.com/blog/

    It has too many wheels, yet I’m impressed.

  3. Wow, What a difference. So that open hood is the killer and not the front grill. Nice. What I like about the coast down test is that anyone can find a place and do their own testing. If someone is doing more than one car or doing more than one thing to the car they can see on the graph what differences the changes make. Now I can’t totally compare mine to yours but it might be close. I am going to search out a nice spot that I can do this sort of test. I was pleased that the motor problem was addressed so quickly and that the catastrophic disaster was very short lived. Nice to see you on the road again.

    Pete 🙂

  4. Jack,
    In the video you talked about having the flywheel, pressure plate and clutch disc balanced as a unit. Why did you include the clutch disc? Every time you change gears it will change its relationship to the flywheel and pressure plate, and if it was even a tiny bit off-center when the balancing was done, it will throw off the balancing of the flywheel and pressure plate.

    Jim Bready

  5. Andyj:

    Now why wouldn’t I like a shiny aluminum car. I have two shiny aluminum airplanes and am actually a bit of a sucker for polished aluminum. I’d love to do a car in that but I’m not much of a hand at an English wheel I’m afraid.

    Jack Rickard

  6. Jim:

    It’s kind of a stock thing. I didn’t invent this. You normally have your clutch, pressure plate and flywheel dynamically balanced together. They have a little plastic device that centers the clutch.

    This is a NORMAL operation that should be performed anytime you install a flywheel or pressure plate basically. We’ve skipped it a few times, and there is ALWAYS a little buzz when we short cut this procedure.

    It’s done very commonly by very modest parts shops. It’s $50 or so around here. $80 in the big city.

    Jack Rickard

  7. GreenEV.

    Didn’t say the open scoop in front wouldn’t help also. Just reporting the hood.

    MOre impact at lower speeds than higher it turns out. Im’ thinking downforce is needed to even out weight distribution for good rolling effect.

    Just typing myself smart there. I’ll stop it.


  8. Does anyone know what happened to Daniel’s motor (warp 11″HV) on the Porsche Cayenne that was at EVCCON. I thought I had heard that he had fried his motor and was wondering if it was a similar putty issue.

  9. Daniel’s car is over 6000lbs. It also had no cooling other than the internal fan. I don’t think there was even any room for additional cooling as it was never designed into the install.

    He just came off of I74 and it died on him before he could turn onto the access road to the airport. After Seb and I towed it into the hangar you could smell the motor from six feet away. He doesn’t have a clutch so it couldn’t be that 😉

    Daniel around to enlighten us further?


  10. Jack, I know you love shiny things and subtleties can be lost with the written word.. Has anybody nicknamed you “Daw”?
    Apologies. Note my avatar. If you call me that “Cooking Fat”, I’ll understand 😉

    English wheel, me? (1974). A highly admirable art. Imagine the results after employing a couple of skilled guys for a few months to copy that Cobra in a polished dural skinned alloy….. I should shut up, lol

    Hey Pete,
    Did you know at the leading edge of any nose or wing there is a high pressure zone? Cars are actually more slippery because they leech this air into the engine bay. How big? That’s a Goldilocks thing.
    A nose cone from the inside of the intake could look great on the Cobra. It’s so me! A big tongue sticking out.

    Good point Nickkkk,
    I’d do it.

  11. Jack Rickard said…”MOre impact at lower speeds than higher it turns out. Im’ thinking downforce is needed to even out weight distribution for good rolling effect.”

    Had a change of mind, Jack? Downforce? MORE impact and LOWER speed? I seem to remember quite a bit of derision about just such stuff only a few weeks ago, case closed, dead horse, and all [see Sept 5, 2011 comments this blog]. By the way, andyj, I was one of two in the comments section to suggest the Soliton could be a concern [Speedster Redux and the Dynomometer Puzzle comments]:

    pb [<--Perin du Bulu] "I wonder why the manufacturer doesn't just send you another Soliton? Also, how about dissecting the Soliton as a white board lecture? Could the failure of a single part allow for what you are experiencing--it functions perfectly until the critical 1000 amp piece is activated?"

  12. The most interesting thing about the roll-down test is that it allows you to assess any potential donor vehicle before even starting a conversion. The essence of science is hypothesis-testing, so, Jack, how about borrowing an Escalade, putting a ton of something in the back, doing a coast-down and see how close you can get on estimating the watt-hrs per mile for your Escalade EV?

  13. Perin I don’t recall getting something correct once makes someone correct all the time. I should know 😉

    Jack, aeroplanes have very little rolling friction when they are flying. How about wings?

  14. Nothing’s every “closed” around here. We kind of ran out of stuff to try on the Spyder. Yes, we get lots of suggestions for unlikely solutions with HEROIC setup efforts. We just can’t do them all. But the Spyder and the Cobra testing have kind of opened us up that all cars are not created equal and that some factors matter more than others.

    We will test the cobra with the old wider wheels and tires next. And compare. At this point, I don’t see that much form low rolling resistance tires. But we’ll continue to test.

    I don’t KNOW why the hood made so much difference. As I said, it might be downforce or I might be typing myself smart here. It DID make a difference though.

    Jack Rickard

  15. The coast down test will measure rolling resistance and wind resistance.

    A reasonably simple test to perform to determine drive efficiency would be to lift the drive wheels off the ground and then measure the unloaded power at different indicated speeds. This eliminates rolling resistance due to the tires and undriven wheels and wind resistance. Any energy used to spin the unloaded wheels is wasted power. Knowing how much waste there is at different speeds could be used to determine the losses when moving due to wind resistance. It would also allow a comparison between vehicles with nearly identical drive systems like the Speedster and Spyder.

    I am looking forward to seeing how the Cobra does on the Dyno.

  16. Look, creative thinking and research beyond surface scratching was required. I supplied this, and, typical for heterodox ideas, was derided, dismissed, etc. A great mind wrote, “If the wind were always southwest by west, said the skipper, “women might take ships to sea.” It follows if Progress were a breeze, wheels would be a footnote like the Age of Stone.

    Andyj, your syntax and mean illogic suggest a possible organic prodrome. It’s not that you were a right once lad, it’s that you are multiply wrong gaffer now.

    Sept 20 Andyj said

    …You remind me with the issues with Redux. Battery’s that can easily give 1000Amps; a motor that can not help but accept 1000Amps but only receives 700Amps at max throttle. Almost nobody would blame the man in the middle…
    The controller.
    It was set wrongly.
    We were hearing theories that were one step beyond recharging UFO’s on here! And you seem to share this mindset.

    Sept 20 2011 Jack Rickard said

    …So subsequent tests with or without the weight don’t either.

    Go back to the beginning in the videos and go through this again. It is ABUNDANTLY clear aerodynamics is not the issue. Being an “expert” and typing a lot doesn’t get you very far in this venue. “Show me.” Which generally means suggest a PERFORMABLE test we can do to eliminate something. ANd if it’s something we’ve already eliminated NO INTEREST.

    Sept 13 Sept 4 Perin du Bulu said
    …Several of the constants in the equations used in recent EVTV episodes to describe motion and resistance are not really constant, e.g., total aerodynamic drag and rolling resistance are non-lineal subject to speed and other forces such as lift. The derby test needs to be performed using different hills with the cars evenly weighted [total and possibly front and rear distribution]: a heavier [within reason] car has more potential energy to convert to kinetic/forward motion and eventual range. Coast downs [from motor powered runs of 30mph, 20mph, etc.] need to be conducted in addition to the free fall derby runs. Energy use tests need to be conducted at 20 mph and 80 mph to rule out peculiar aerodynamic interactions such as negative lift given that the Spyder was engineered to be a race car while the Speedster was developed as a roadster…

    Sept 4 Perin du Bulu said…
    The Speedster looks to have a considerably larger frontal area than the Spyder (links below). Since the Spyder was a race car, it might have been designed to display best performance at higher speeds, while the sports car Speedster might have been optimized for mid-range speeds. I’m suggesting the graphed efficiency lines might narrow, converge, or even cross at 80, 90, 100 mph. Negative lift forces and or perhaps some sort of drag crisis could allow for unexpected results…

  17. Yes, indeed, the eCayenne did experience WarP 11HV motor flame-out on the Sunday after the Conference (and what a Conference it was…thanks Jack/Brain). As I was cruising along on I55 in the rain doing about 70 mph (late for my flight) and approaching the Airport exit, I heard a loud and sudden unnatural rumbling sound and some knocking from under the hood, along with a complete loss of motor power. Devastated, I pulled off the ramp and coasted to a stop on Nash road, and called Sebastien. He rushed me to the airport after which he and Chris towed the Cayenne the final couple of hundred feet to Jack’s hangar (many thanks to you both again. I must say, I’ve found the vast majority of EVC people to be really good folks).

    When Paul pulled it out, it did appear to be a balancing putty issue. The motor should be at NetGain by now and George will be evaluating it to confirm the diagnosis. It looked torn up and black inside, and it did smell badly after the event. I believe the Soliton controller EPM limit settings were at 5500 or 6000, so that’s not the likely cause. And overheating should not be the issue either (see below about the forced air cooling of the motor).

    The Cayenne is in fact 6162 lbs, and Im fairly sure the 11HV motor is the only motor that could move that car as briskly as it did in a single motor configuration. [One can argue about whether a two-motor design would have been better (and that’s what I’d favor too in a next build for a heavy SUV…Jack and Brian are half-way there with the elEscalade, we saw).] I was not unhappy with that motor’s performance in my car. So to cool that motor on that heavy a frame, there is an oversized blower directed at the motor (you can hear it turn on when you turn the key on, and its quite loud actually), and the protective off-road underpan below the motor has not been replaced after the ICE was removed (it would have further reduced cooling airflow to the motor). Should the 11 HV be cooled differently than other brushed DC motors (most don’t have liquid cooling, right?). Have others experienced 11HV motor failures? If so, were they balancing putty issues, or something else? I guess I can take comfort in the superb NetGain customer service and Jack’s bliss with the replacement 11HV in the Cobra.

    – Daniel

  18. Perin, Why are you confusing controller theories with your theories on air/rolling resistance?

    Jacks just proved once again the /100 rule of weight over lbs and WH/miles.

    What is found on here is having a direct influence what I’m clogging together back in the pit.


  19. Hey Andyj!

    Uh, I must be tuned in to a different channel. I saw/heard/read that Jack found the energy consumption per pound*mile rate of the eCobra to be significantly (~50%) different (higher) than that of his other cars. And Illuminati’s Seven has a rate that is significantly lower.

    Another puzzling thing is that the newer, cooler motor consumes about as much energy as the older, hotter motor.

    I would guess that some vehicle dynamicists would attach a lot of caveats to Jack’s rule in order to follow it, like a heavy percentage of stop-and-go driving.

    Here’s something that was proven centuries ago: A flaming chariot will travel across the sky from east to west, almost every day (Observed during real tests). Proove to me its not a real flaming chariot! 😉

    Hey Jack!

    Temperatures are falling and the eEsclade’s seat warmers are calling… When does the eCobra go for paint and packing?

    Mike Kaindl

  20. “I don’t KNOW why the hood made so much difference. As I said, it might be downforce or I might be typing myself smart here. It DID make a difference though.”

    I’d take a wild guess that eliminating a giant hole in the front that caused turbulence and replacing it with a smooth surface that helped preserve laminar flow would explain it pretty well.

  21. The two at the shop are mine. He tested them for me. They are the old Hi-Power 100 AH cells. One sent was under 1 volt and the other was nearly full and from a running vehicle. The one under 1 volt had been sitting for nearly two years in that condition and maybe even longer. The other was a good cell that had been abused in my vehicle and before I got it. He tested at I believe at 1 or 1.5 C for both the charge and discharge of the cells. At those ratings the cell was being charged and discharged at more than twice the factory rating of these cells. It should have been tested at like .5C. They are not the best for hi power pulls but they have been put through many many 7C discharges. The ones pulled from the MG. I believe Jack said the good one at 1.5C discharge had like 85% capacity but at that rate 85% is still very good. The one that was near empty came in around 92%. Jack may be able to remember. I’d have to dig into my emails to find out what he told me. He thinks if they are tested at .5 C like the factory states that they should still be OK considering the life they have had. We will continue to use and abuse these cells to see how well they fair over time.

    Pete 🙂

  22. Below are the results Jack sent. They were tested at double the factory rate. If done at the factory rate they would show better results.

    The cells were built in 08.

    Pete 🙂

    Battery number 4 was received at a voltage of 0,6v. You had claimed this had been in storage for a long time. It was very low. I charged it to a charge voltage of 3.650 and it took 103.32 Ah to get there. I let it set over night and it was a little down I was thinking at 3.34v but this is pretty normal. I discharged at 1C and retrieved 90AH from the cell.

    Cell #8 was not so good. It was almost fully charged on receipt and I added 2.02Ah. Static overnight it came in at 3.336volts. But discharge at 1C was but 82A.

    Discharges were done until the cell showed a static voltage under no load of 2.75v.

  23. Perin,
    You are embarrassing yourself. All because your theories were hurt. There is no variance of CdA on any vehicle at a different speeds. One car has a slightly higher rolling resistance, thats all. You cannot re-invent the wheel and call it progress.

    Go Figure,
    You ARE on a different channel. I suggest you read Jacks blog.

  24. Thank you for sharing the Helwig brush presentation, Jack. Mr. Brunka’s Japanese (sword) smith-precise practices are an inspirational exemplar. A few questions came to mind as I was watching this week’s episode. The putty balancing bothers me. I don’t like lead weights used to spin balance wheels, either. Both seem primitive, like design/execution flaws. What challenges prevent the construction of an electric motor which is balanced to the point putty is unnecessary? Is there an EVTV episode which discusses advantages/disadvantages of brushed motors [vs brushless]? How many brushes on the Warp 11 motor? Two? Four? 9 psi per brush (ideally instead of factory brush _?_ psi) on the commutator…what sort of drag would that produce in terms of extra energy used to overcome mechanical resistance?

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