The online milieu offers enormous opportunities for learning and information about topics of interest. In the early dreams of a global internet, this ability to pool the expertise of many individuals around very narrow topics of interest was one of the greatest boons foreseen. Unfortunately, in many ways it has turned into a cesspool.
There are a number of people out there successfully converting electric cars. I am disheartened to observe that the majority of them view anything they learn along the way to be a “proprietary secret” they can somehow leverage into untold riches from their little shop in what they see as a viciously competitive world.
Well, if you see it that way, it is that way – for you.
That mostlly leaves the online forums as a source of info about electric vehicles where roving bands of clueless people copy/paste what the last guy said into the next conversation – with a few typos and often some expert opinion on what it really means. This leads to comically large bodies of total disinformation misleading anyone who reads it into believing it is real. The pool of knowledge becomes a cesspool.
We attempt to counter that in two ways. First, we actually DO build electric cars, and we share all of it with our viewers. The good, and too often the embarrassing bad. To get the most from it, you have to watch over time unfortunately. The neat device and grand theory as to why that’s just the tits in this week’s episode may be followed in six months and a few thousand miles by an examination of the charred pieces and a rebuild using something else. Real world. I should apologize for it.?
The second prong of our attack on disinformation is to actually DO testing, not just talk about theories we’ve heard. And better yet, to demonstrate how to DEVISE tests you can do to learn first hand yourself. We encourage others to also perform our tests and report their results = either confirming or contradicting our findings.
Part of this goes again to the 12 blind men around an elephant. Corresponding about IDENTICAL cars, for example with Eric Kriss who basically built Speedster Duh, can be quite frustrating. Different results from two identical cars? Or maybe not so identical. And maybe not exactly the same test conditions… you see the problem.
Part of it is contrast and comparison. Most people don’t HAVE two vehicles to compare. Indeed, often you have NO other frame of reference at all. You build your first electric car, and often take your first electric drive in it. Does it feel like it’s supposed to? How IS it supposed to feel?
Our first car was the red speedster of course. It ran flawlessly. Oh, I guess I was a little disappointed in the performance. But it certainly kept up with traffic and was pleasant to drive.
Six WEEKS later, I was playing with the Kelly Controller software and noticed the minimum battery voltage setting. I see that voltage a lot so I must be at minimum voltage a lot. I wonder why?
I changed the setting to a lower value. Instead of 100v for my 108v pack, I lowered it to 90. Reset the car and hopped in for a drive. Backing out of the driveway in REVERSE I very nearly shot through the fence around the property in an almost uncontrolled acceleration. I immediately stopped the car and checked everything again. I reset the voltage to 100v and the car behaved quite normally. I changed it back to 90v and VERY carefully applied the accelerator. The car shot ahead like a rocket (comparatively speaking).
When the controller notes the battery voltage approaching the “minimum voltage” it cuts back current to the motor to prevent the pack from going below that voltage. Of course it does this several hundred times per second. As a result, when I applied throttle, it put out power to the motor until the voltage dropped to 100v. At that point it limited current to precisely the value necessary to hold 100v. If the voltage crept up, it increased current. If it began to sag below 100v, it would decrease current. And it did this so well, it felt quite smooth. The car operated flawlessly, at about 1/4 power.
The batteries DO sag in voltage when you put them under load. So by decreasing this “minimum voltage” all of a sudden I could get full power out of the device.
While this is almost comical, it illustrates the problem. No frame of reference. I might have gone two years before discovering this. Never really gotten excited about electric cars, which felt pretty tame up to that point. And so never shot our first episode – no EVTV. For want of a nail….
So I’m very sympathetic to the guy trying to build an electric car with no “go-by.” No frame of reference or model to build too. It is ALL a discovery process.
We did this comparison between the Speedster and the Spyder largely as an exercise to demonstrate some of the components of range and specifically the impact of aerodynamics on range. Whey you get one range at 45 mph and a very different one at 75 mph.
But real world testing, as opposed to staged scripted test demonstrations, always have outliers and anomalies. In this case a huge one. A very marked difference between two cars with ostensibly identical drive trains.
The problem was that the aerodynamically slightly pudgy looking 356, which was also 200 lbs heavier, got DRAMATICALLY more range than the sleeker and lighter Spyder 550. And everything we tried made the disparity more pronounced.
We spent $3100 on running gear upgrades using really kind of extreme aluminum rotors and calipers, low rolling resistance tires, lightweight wheels, and indeed shaved some 60 lbs from the car, dropping the curb weight from 1905 to 1844 lbs.
Of cousre, we also learned that the Michelin Energy Saver A/S low rolling resistance tires on the Speedster weren’t set to 42 lbs pressure as we thought, but a more squishy 33-34 lbs. When we aired the tires up, the Speedster got dramatically better, as good as 1.000 AH per mile at 40 mph steady speed. That’s a 180 mile range.
Meanwhile, all that work on the Spyder produced improvements, but improvements so meager they are almost in the noise level of the test.
ENter by far our most popular test technique. The Soap Box Derby. We’ve received so many comments on this test that we are thinking of incorporating it into our race day at the Electric Vehicle Conversion Convention (EVCCON 2011) I’m searching for some kind of incline or ramp we can use. In addition to the electric AUTOCROSS RACE and the electric DRAG RACE we have scheduled for Friday afternoon, I would like to have a SOAP BOX DERBY where we can see who’s car rolls the furthest at 2 mph.
The Speedster will pretty much roll down the street pretty nearly to the house in neutral. The Spyder almost goes into reverse and backs up the hill. It barely moves at all.
We received a lot of input from viewers on this. My favorites suggestion came from John Hardy of the UK. This involves some residual pressure valves in the brake lines. In cars where the master cylinder is below the calipers, the brake fluid of course has a tendency to drain back down into the master cylinder and you have to pump the brakes to get the fluid back up into the brake calipers. On drum brakes, the wheel cylinder holds much more fluid than disk brakes. And these cars were all originally equipped with drum brakes on the rear, disk brakes typically as an upgrade.
So to keep the fluid from flowing back, they use a little check valve that maintains just a bit of pressure on the line to keep the fluid from flowing down by gravity. On drum brakes, this residual pressure valve typically provides 10 ps, while for the lest voluminous disk brake calipers, a more modest 2 psi. John’s suggestion was that they had upgraded the rear brakes to disk but kept the 10 psi residual pressure valve from the drum brakes. This causing the rear pads to drag.
I loved it. Our master cylinder IS below the calipers and we don’t have to pump the brakes so we must have that.
We went through the car and can’t find one of these residual pressure valves anywhere, front or back – or of any value. But it was a GREAT theory.
We had the car aligned this week. I haven’t’ retested yet but I would be astounded if that made that much difference. Perhaps. But we did reroll the Soap Box Derby and no joy.
Several viewers have commented on the negative camber on the Spyder. I think it is slightly more visible on the Spyder. But all these cars have negative camber – the book is 2 to 5 degrees. The Spyder is more on the 2 degree side actually.
About all that is left that is obvious is the difference in the Ring and Pinion gears – essentially the “differential” on this car. The Spyder has a 3.88:1 and the Speedster has a 3.44 to 1. Eric Kriss spoke to a racing transmission expert who claims that could indeed do it. So it’s our main culprit at this point.
It is unlikely that I would swap out the transmission to find out. The car runs nicely and has a 100 mile range now. But we will certainly stick to the 3.44:1 for future builds.
You always get a result from testing. But in the real world, often it can be weeks or months before you really know what it all means. Aerodymics still has the predicted impact on range. But why these two cars are so very different is so far beyond me.
We have a new Canon AHX1 camera we’re trying out. It has built in XLR microphone inputs but we apparently did not adjust our audio very well because it is truly awful in this episode. My apologies. Testing, testing. …one…two….three.