First Commute Of The Fall

Today was D-day. I finally decided to put insurance on the car after a week of soggy motorcycling to work.

It was rather uneventful. No breakdowns and not much excitement.

The new motor definitely has more torque than the old one but runs out of steam at a lower RPM. Math would obviously dictate the lower RPM as the HP output is nearly identical because of the limitations of my controller, and HP = (FT-LB)(RPM)/5252. Actually it might now have slightly less power because I am now missing a field controller that was putting another 2500W into the old motor as well. But it sure didn't feel less powerful once I realized that I needed to shift at a lower RPM.

I am still getting used to the new power curve. An example of this is on the way home, going up the mile long hill with the 4-way stop in the middle. Today after the stop (still going up hill), it topped out at 53 km/h in second gear at 4100 RPM. The old motor would top out at 60 km/h in the same spot. But with the new motor all I had to do was shift into third (2700 RPM) and it then accelerated to over 65 in no time.

The throttle response is now much much nicer. Throttle angle seems to be more proportional to torque output, where before it was proportional to motor RPM, almost like a farm tractor throttle. And the oscillation caused by two controllers fighting over who is boss is now gone (because I fired one of them!).

When I got home, where the old motor would be about 150F on the body thanks to the climb up the hill, the new motor wasn't even warm to touch! Either this motor is more efficient or its increased mass is acting like a giant heat sink.

Today I fixed the vacuum pump relay chatter problem. You can hear this chatter in the previous video I posted. All I did was plumb the vacuum switch directly into my new vacuum reservoir instead of into a tee between the reservoir, pump and brake booster. Problem 100% solved. The reservoir dampens any pulses before they get to the switch.

Here is the vacuum reservoir I made out of a piece of ABS pipe and some end caps:

And here you can see how it now resides in a nook in the fender:

Of course with my new vacuum switch fix, it now has another small line running into it that the picture doesn't show.

Wiring Schematics

Battery Monitoring System

Here is a video showing a few of my latest upgrades on the Electric Booger:

Here is the schematic for my battery monitoring system:

The reason I power the system voltmeter with a 9V battery is because it is a very cheap eBay voltmeter that has a low-resistance connection between the power side ground and measured side ground. If powered by the car's accessory battery it makes a connection between the traction side and accessory electrical systems.

I have actually been shocked by the car when I originally powered this voltmeter with the car's accessory power. I was tightening the nut on the power lead at the main contactor and my elbow touched a bolt on the car somewhere. Zzzzt. That is when I started powering the voltmeter with a separate small battery.

Big Update

I have been fairly busy with upgrades on the Electric Booger.

While the motor was out I decided to build a cooling system for the controller. The controller never gets very hot, but I figured since I had a small 12 volt fan kicking around, I may as well. Here is a video showing the new cooling system:

In the meantime I sent the motor drive end cap and old adapter plate to my machinist friend Matt to drill and bolt together. This is one thing that I did not trust myself to get absolutely perfect. Once the adapter plate was mounted to the new motor I was able to take some measurements for Matt to use for the new coupler. The new coupler is made of the same clutch centre as the old one, but this time it is welded to the splined shaft stolen from the hydraulic pump that this motor used to drive. Once again Matt has made me a work of art!

What are the two bolts for? They are pickup teeth for the new tachometer speed sensor. Matt gave me a proximity sensor in order to make the factory tachometer functional. This is basically a digital on/off switch that turns on when there is metal nearby:

All I am doing to make the tach functional is switch 12V on and off to the tach signal wire that used to go the negative side of the ignition coil. Here is how I tested it out:

I spun my cordless drill up with this bit on and held the sensor close to it. I need two pickup teeth because this car had a four cylinder engine so there were four pickup teeth in the distributor running at half engine speed, meaning I need two teeth if they are running at actual motor speed. It says "0-1300 RPM" on the side of my drill and the tach was at 1200 RPM. Close enough for me!

Here is the speed sensor mounted to the adapter plate:

When installing this new motor I had to fabricate a mount point for the right side motor mount. I finally decided to simply weld a 3/8" bolt to the bearing cap. The bearing cap isn't exactly a strong mounting point, but all this mount has to do is locate the motor/transmission at the proper angle, so there is not much weight on it. Anyway, since I would probably weld giant holes into this thin plate, I let Mike at work do it, who could probably weld wood to a mattress if he had to.

After installing the motor and hooking everything back up, I decided to run the motor at 2000 RPM for an hour. Since I rotated the brush holder there is a good chance that I did not get it fully centred to the armature. Running it for a while at no load helps to break the brushes in. Here is a video:

Motor Removal

Today I removed the motor from the Electric Booger. It took a grand total of 50 minutes. It was almost like removing a starter from a Peterbilt.

I inspected the motor coupler because there is unfortunately no way to do so when the motor is installed. I just have to trust that everything it tight (and nothing that is not supposed to move is not moving) and that it will get me to work on time.

The good news is that the coupler looks very good. Thanks to the excellent machining work of my friend Matt VanTol, the set screws holding in place were still tight and there is absolutely no abnormal wear on the splines:

Just a bit of rust. Maybe I will put some grease on it when I assemble it this time.

Motor Direction Reversal And Brush Timing

Now for some technical stuff.

One of the things I had to do was reverse the direction of this motor because it spins the wrong way for my car. The most immediate question is: "Why don't you just reverse the polarity to the motor?" The answer is because a series wound motor will spin the same direction no matter what polarity you give it.

This is because when you reverse the polarity to the motor, it changes the direction of magnetism in the armature. But because it is series wound, it also reverses the direction of magnetism in the field at the same time. The result is a motor that still spins in the same direction. A series wound brushed motor runs fine on AC (alternating current) as well. Many small household appliances and power tools use them. (In case you care).

This means that to change the direction of this motor, we have to change the polarity of either the armature or field, and not the other. What I did to accomplish this was change the wiring inside the motor to reverse the polarity of the armature only.

I had to un-solder and re-solder the cable on one power post:

And bend one field power connector to hook it up to a different brush:

Now for brush timing. Brush timing is very important. As each commutator bar passes under a brush and current starts to flow into the armature at two points opposite each other, this must be timed perfectly so that maximum magnetic force against the nearby field shoes takes place. You would think that brush timing would be the same for every motor, but it is not. This motor has advanced timing, meaning that the brush is advanced when you compare it to the field pole, as you can see in this picture:

The long line is the field pole center line. It lines up with the field pole fasteners that are further down the motor body. You can see that the brush holder lines up with the "F" marks. I measured this timing to be 11-1/2 degrees advanced, which is about the max for brush timing. If I tried to run this motor without changing the timing, it would turn very slowly and the brushes and commutator would destroy themselves quickly. For the motor to have the same timing in the reversed direction, the brush holder will have to line up with the "R" marks:

I drilled new holes in the end plate where the brush holder fastens to and it now looks like this:

You can see the extra holes in the end cap where the brush holder used to bolt to:

Why have advanced brush timing at all? Many DC motors have neutral timing and work fine in either direction. However, for reasons that are far beyond me, as you increase the voltage and speed in a motor (typically beyond what it was designed for), you need to advance the timing. It is sort of like a gasoline engine that needs more ignition timing as RPM increases. If you do not advance the timing in a DC motor, harmful arcing will occur between the brushes and commutator as voltage and speed is increased and quickly destroy the brushes.

After I got it all back together, I hooked up 12 volts to it to test it out:

It spins the right way! And it seems to spin at a good speed when compared to before I modified it, so it looks like I got the brush timing right.

Motor Update

On Friday my new (to me) motor arrived. Right away I was able to start messing around with it. Here it is being powered up on the bench with 12 volts:

It spins much much faster than my sepex motor does unloaded, but series wound motors do that because of built in field weakening (something most DIY EVers take for granted!). And it spins backwards. Since it only has two power studs, this will require rewiring some of the internals to reverse the polarity between the armature and field.

Another concern is the tiny internal splines on the drive end. Check out how tiny they are:

The mating shaft is about 1/2" diameter at its smallest point. According to all my research, 50 ft/lbs of torque requires a shaft diameter of 0.55", so this would be iffy at best. One option here will be to bring the armature to my friend Matt (who is a machinist) so he can add a shaft on the end. This would be stronger and less difficult to adapt to my transmission input shaft.

Today I completely disassembled the motor:

After washing all the guk off the bits, this motor looks like it is in very good condition.

Here are the stator windings and armature:

Here are the stator windings and shoes installed in the case:

Here is the brush holder:

And here is what happened when I found some Cat yellow paint laying around:

I wish I would have done all this with my original motor instead of rushing to get the car on the road. It is making me appreciate what all goes on inside of these motors!