13,000 EV Miles

No doubt the 2 or 3 people that read this blog have long lost interest since I haven't posted anything for 3 1/2 months.  But as they say, no news is good news, and I would say that by and large, that applies here.  I pulled into the garage yesterday after running a quick errand (a Frosty for a sick child), and I took note of the odometer reading.  I delivered the Frosty and then entered the data in my spreadsheet and was surprised to see that the running total of EV miles I've driven added up to exactly 13,000.  Now the 3 year anniversary of the car hitting the road is in a month and 1/2 or so, but this seemed noteworthy enough that I thought I'd post an update of how things are going and include some numbers for those who enjoy statistics.

Keen readers will remember the episode I went through, just about a year ago, with a high voltage leak to the chassis, which I traced back to a frame leak through the motor and ultimately resulted in getting a new motor from Netgain.  George Hamstra was simply sick of repairing it and sending it back to me.  On a side note, George told me he has that motor in his garage and intends to put it in his Bricklin conversion.  I hope it does well for him.  At any rate, in addition to putting the new motor in, George also sent me some new brushes to try out, ones he felt would produce less carbon dust and so were better suited for my application.  He sent me (at his expense mind you) some Helwig Red Top brushes that are made of a harder compound than the standard brushes the Netgain motors come with.

You have to understand, Netgain Motors was born out of the EV drag racing community.  The earlier drag racers kept burning up their GE motors.  George and others saw different opportunities to improve the motors here and there.  They were working with Warfield Electric on building motors that incorporated their changes.  Before long they had a completely new beast on their hands and decided to start selling them.  The brushes they chose were of a softer carbon compound, ideal for pushing high current to the armature   Under drag racing conditions, the motor would generally fail for some other reason long before the brushes did.  But under low current applications, like driving to the store for milk and such, the brushes tended to wear out much faster and give off a lot of carbon dust.  The Helwig brushes have worked out so well for them that they've made them available on new motors.

Understanding that, we get back to my car and the unexpected change I noticed after I installed the new motor with the new Helwig brushes.  Suddenly, the car was more efficient.  About 14% more efficient to be precise.  Jack Rickard of EVTV ran experiments with an old WarP 9 motor he had at his shop, and found the same improvement.  Well, a great deal of time has passed, and I've put many more miles on the car, 4797 to be precise.  I thought I'd take a look at the numbers to see if the increase in efficiency has held true.  The thing is, I realized that I'd been doing the math wrong.  Well, the truth is, I knew I was doing it wrong, but I was too lazy to fix it, thinking the difference would be minimal.  To sum up, I was taking all the trips I made, and averaging the Watt hours per mile used.  The trouble is, the 275 Watt hours per mile used on a 35 mile trip was being averaged equally with the 378 Watt hours per mile on a 4 mile trip.  Anyone can see, those numbers needed to be weighted differently since the distance was different.  The solution is easy: add up all the miles driven and divide it by the sum of kilowatt/hours used.

What did we get?  As I mentioned, I've driven 4797 miles since the brush replacement, and I've used a total of 1526.46 Kilowatt/hours.  That works out to 318 Watt hours per mile.  In comparison, I grabbed a 4804 mile sample of data from before the brush swap and noted that I'd used 1779.72 Kilowatt/hours, which works out to 370 Watt hours per mile.  So does the 14% efficiency gain still hold water?  370 - 14%(51.8) = 318.2.  Apparently so.  I knew the way I was calculating the data before wasn't going to be wildly inaccurate, or even mildly for that matter.  But it's encouraging to see that numbers still hold to be true.

Moving on.  A couple weeks ago I plugged the car in, turned on the charger and heard a familiar "pop" come from the front of the car.  I recognized it immediately as the same "pop" I'd heard before when the motor had become caked with carbon dust and there was a mini flash over in the motor.  What the...?!!!  The only way this would happen was if the carbon dust given off by the brushes wasn't being blown out.  Since the Manzanita charger is grounded to the chassis, when you turn on the charger, if it senses a path from the chassis to the battery pack, it will either throw the circuit breaker in the charger itself, or blow up.  I've had it do both.  For the gory details of each, feel free to look further back in the blog.  Suffice it to say, you don't want to accidentally touch a battery terminal and the chassis with a multi-meter probe at the same time when you're charging.  Anyway, clearly I had a build up of carbon again!  How could this happen?  I've got a fan forcing air into the motor for chrissake! It should be blowing all that dust out.

I checked the fan, and it was running, but the output was very low.  I looked at the filter and found that it was caked with dirt.  Ahhhh.  I'd cleaned it about 6 months earlier, but clearly there's a problem.  Well the problem is really quite simple.  Having no way to locate the fan and the filter higher up in the motor compartment, I mounted it on a tray right next to the motor.  Meaning that the fan and the filter are about 9" off the ground, right were the dirtiest air is.  You may have noticed that every manufacturer locates the air intake for their cars as high up in the engine compartment as possible.  I'm thinking that may be intentional.  I took the filter off and the flow of air was much better, like I expected it to be.

So now I'm left with two problems.  First, the motor is full of dust and I need to blow it out. Second, I need to figure out what to do about this filter location; clearly where it's at is not the best place for it.  Last time I had a dust problem with the motor, I used compressed air to blow it out.  That worked pretty well as a huge plume of dust came out when I aimed the air gun into it.  The problem is, I have to take the motor's shroud off, and to do that I have to take out the batteries over the motor and to do that I have to ...  you get the picture.  Curse the idiot that designed this!!!  But then I had a flash of inspiration.  What If I simply hook up my leaf blower to the inlet hose, the one that runs from the fan to the motor.  Leaf blowers put out a crazy amount of air.  Oh, now this will be good.  Or at least fun.

It wasn't easy, but I was able to get to the inlet hose and basically taped the end of my leaf blower to it using my favorite tape in the world, gaffer's tape.  It's basically black duct tape, but easier to tear.  I had my daughter sit in the car and rev the motor up to about 3500 RPM, and I turned the blower on.  I was very pleased to see a plume of black dust come out the back of the motor (and also a bit disturbed).  I let it run this way for three or four minutes until I was confident it had expelled all the free carbon it could.  The great thing was, I could put my hand at the back of the motor and feel a tremendous volume of air coming out.  I started to wonder, could I some how use this leaf blower as my motor fan?  Apart from it being impractical, it would make the Z3 the noisiest EV on the road, ever.  No, what I really need to do is sort out the filter location problem.

With the fan located low like it was, it's collecting dust at a much faster rate, and ultimately choking the motor.  I looked, thought, measured, looked, thought some more and came up with nothing.  There is simply nowhere else to locate that filter.  Then I had a thought.  what if I eliminated the filter completely?  Stick with me for a moment.  The Netgain motors come with a screen covering the front bell housing, and the brushes.  People run them like this all the time.  The problem is some dirt and sand will inevitably get in and get on the armature and brushes cause them to wear prematurely.  OK, so that's the trade off.  But now, what if the inlet for that air came from a place that was less prone to see dirt and sand in the first place?  After all, the front of the motor sits right where you would expect most of the dust and grime to be, so if I could find a place for the inlet that would provide cleaner air than that, I should be good.  What I found was that there was a way to run a 3" hose from the fan inlet up in front of the firewall and just behind the large battery pack that's over the motor.  It's shielded from the main airflow when the car is moving down the road, yet it's got an open area large enough that it can easily get all the air it needs.  I checked and the output of the fan was terrific.  As far as I'm concerned, problem solved.  It's true that a bit of dirt may be blown into the motor, but I think this is a far better solution than cleaning the filter weekly to ensure good airflow through the motor.

The truth is, I'd love to get a fan that would push more air into the motor.  The one I have pushes 120 CFM.  George even said that's likely too low.  The problem again is one of space.  The fans I've found that push more air won't fit in the space I have.  I keep an open eye out for one, from time to time I comb through the interwebs looking for a suitable candidate.  So far, no luck.

That's all for now, but check back in early March on the car's 3rd anniversary as I'll post some more stats.

More Work on the Tray Under the Motor

More work in the engine bay today.


Here is a shot of the engine bay at it's current state. The tray under the motor is mounted in place (although not permanently just yet). But it does give you an opportunity to see the tray under the motor, the duct work for the motor fan and the final position of the vacuum pump assembly.

Here's a detail of the passenger side. I believe I know what you're thinking. I can nearly hear it. "What on earth is that pink and yellow monstrosity next to the motor?" Well trust me when I say that the picture really doesn't do it justice. It's far, far uglier in person.

I mentioned earlier in the week that I need some way of keeping water from splashing on the motor fan and it's filter. Well, the space is tight and irregular, ruling out a tidy piece of aluminum. And by the way, for anyone who saw the work I did on the housing for the vacuum pump, you know I may not be capable of a tidy piece of aluminum.

Anyway, I constructed the shroud out of two flexible plastic cutting boards. I hot glued them together, and then ran some small screws along the seams just to hold them tight. It's not water tight, but it will keep all flying water off of the assembly. I'd show you a more complete picture of the whole assembly, but my fear of being mocked by all has gotten the better of me. Truthfully though, it works just great. It contains the assembly quite well and flexes around all the little things that stick out here and there.

I don't know that this picture is really all that different from the one I posted last week. But there is one important difference. The vacuum pump is actually in the housing now, and the housing is bolted down into place.

This whole tray assembly has taken a terrific amount of time, but it's all been necessary. It's a small car, with precious little space. Dropping a WarP 11 motor in that engine bay instead of a 9 hasn't helped matters as far as space is concerned. Everything that I need to fit in place I have fractions of an inch to spare at best. It makes for one challenge after another. But it's fun anyway.

Engine Bay Pan and More

What a busy week! I got quite a lot done, and at the end of each day, I was just too tired to post anything about it. So I have some make up work to do.

Over the weekend, I decided that the big battery box in the front could really use some lateral cross bracing. So Tuesday I went about designing, cutting, drilling and painting some cross bracing that will mount to the steel we've welded in place, and the battery tray it's self. Only 1/2 lb of steel added, but it will add a lot of stability to the structure.

Wednesday I went about designing a pan to fit under the motor in the engine bay. It will do a couple things; 1, make the under side of the car a bit more aerodynamic, and 2, give me a place to mount a few of the components that I've yet to fit. I made a cardboard template, cutting, fitting, cutting, fitting, cutting some more... you get the picture. There is a "x" shaped cross brace that mounts to the chassis and the front sub-frame of the car. The idea is to shape the piece to sandwich between the brace and the car. Lots of trial and error and I got the cardboard just right, so I went and bought some aluminum plate.

Thursday was spent cutting the sheet of aluminum, shaping it and bending it to fit in the place I'd envisioned. I'd never given much thought to having a 10 ton press break in the garage, but I can tell you it would have been handy the last couple days. Instead, my work bench, some angle iron, clamps and a rubber mallet had to suffice. It took a while, but I got it to work out real nice!



In the top picture, you can see the passenger side of the motor and the aluminum plate underneath it. This space will hold the blower that will force air into the motor for cooling. In the bottom picture, you can see (although just barely discern) a box on top of the aluminum plate. This is located on the drivers side and that box will hold the vacuum pump. Which brings us to what I did today. I cut and shaped the aluminum for that box this morning. I have to do just a little adjusting to it before the vacuum pump is ready to be mounted into it, and then it to the plate.

Man, I can't wait to finish!

Odds & Ends Part IV

1. Finished the duct work for the forced air cooling on the motor. You can see the gray striped tubing heading toward the firewall. The fan itself will sit back in that area.

2. My first attempt at building a cable with 2/0 copper. It wasn't too bad really, but you can see that it takes a bit of a strange route. Why didn't I go in a straight line from one terminal to the other? Well, to do that, the lug under the rubber boot stuck up from the motor a full 1/4" more than routing it the way I did. Believe it or not, I need that 1/4" to help the batteries that will be sitting on top of that to clear the hood above.


3. On both sides of the motor, you can see the brace I made running down from the motor to the motor mounts. Those are strictly to hold the motor in place when it tries to spin from the torque it generates when accelerating. I still need to drill the hole at the top to allow the 1/2" diameter bolt to go through it, but I don't have a drill bit that size yet.