Love and Love

Dear friends and followers.

A lot has happened since the last post. I am now a married to the most wonderful, and understanding, woman in the world, Lisa Wildare. I Love you!

The car is back on the road after changing brushes, brush holder, installing a fan and limiting the current to the Agni.

After restoring the commutator I installed the brushes and set the timing. The default timing marks cannot be used and in order to find the new "zero" I used the following procedure.

Brush holder with brushes fitted by Joztek.
The cardboard helps during installation.

1. Attach the brush holder and tighten the screws just so you can move the brush holder with your hand.

Brushholder from Jozztek, fitted with screws to aid set timing.

2. Apply a low and stable voltage, I used 13.8V from a charger with supply mode.
3. Attach an amp meter to monitor the amps used by the motor.
4. While the motor is spinning, read the amp value and carefully turn the brush holder in either direction. Find the position were the amp reading is the lowest, this is our new "zero". Make a mark on the motor and on the brush holder.
5. Turn the brush holder against the direction in which the motor i spinning. I turned the holder 1.5mm. See the Agni workshop manual for more info.
6.Tighten the screws on the brush holder CAREFULLY!

Let the motor run for 20 minutes or so before steping on the gas.

After the timing was set and the brushes were run-in it was time for a test run. I made a configuration change to the Kelly before the first run. Max amp's was set to 360A. During hard acceleration I could feel the smell of hot brushes so I backed it down to 300A.

I haven’t had time to work on my water cooling of the Agni but I have a lot off fans laying around so I decided to make a cooling fan to the motor. There is not a lot of space left between the Agni and my batteries so I have to put the fan on top.

A (D1238B12B9) 12V fan capabel of pushing 5.25m3 of air per minute.

The fan sounds like an airplane when it's running. The plan is to use a thermal switch that will control the on/off of the fan. For now it's hi jacked into the circuit for the lights. I can't hear the fan when driving.
Air is pushed down in parallel to the Agni's rear plate. As you all know the Agni sucks air through the backplane and out through the stainless ring. In order for the air to get into the Agni I put a small piece Plexiglas in the bottom of the Agni.

The fan on top and the plexiglas in the bottom.

When the fan is running and the motor is still air is coming out under the car. When the Agni starts to spin you can feel that the air flow under the car gets weaker, the more RPM's on the Agni the more air is used for cooling. At max RPM almost all of the air from the fan goes through the Agni.

With the fan installed I hooked up my Ohm-meter to the thermistor in the Agni and went for a ride. The fan, in combination with lower the amps, is working fine. The Ohm-meter never goes below 10KOhm when the Agni is spinning.

Restoration

As you all know I got a bit too cocky chasing Porsches on the highway and the Agni had a brush meltdown. The first thing I needed to do was to get a new brush holder and new brushes. As it turns out one of my friends from the diyelectriccar.com forum is the distributor of Agni in Europe, www.jozztek.com, Jozztek has a deep knowledge of the Agnis and a lot of racing experience as well. I could not reuse any of the old parts so I got the brush holder fitted with brushes. Jozztek matches all brushes so that the voltage drop/resistance is the same between brushes.

Meltdown brush holder

New brush holder from Jozztek with matched brushes

Next thing on the list was to restore the commutator. When the brushes melted there was a lot of arching going on and the surface of the commutator, where the brushes connect, had to be refurbished. In order to refurbish the commutator surface I needed a "grindstone". Luckily I found a company just outside of Stockholm that specializes in DC-motors. www.karma.se has a wide range of brushes and tools for restoring electrical motors.



Commutator before resurfacing

You need to spin the motor in order to resurface the commutator. The RPM of the motor should be around 500 when using the stone from www.karma.se. Jozztek shared his bright idea to use the old brush holder and two old brushes to drive the motor during grinding. Split the brush holder in half and attached two brushes, one negative and one positive.

The Agni gives you 71 rpm/V so if you connect is to a 12V battery it will spin at about 800 rpm. Cut the grind stone so that you can fit it to the commutator. Use a vacuum cleaner during the grinding to collect the dust. You don’t have to apply a lot of pressure to the stone and you will feel when is working. Change position of the stone often and keep it steady.

Stop the motor every now and then and inspect the result. Don’t overdo it!

The picture above shows the commutator after it's been resurfaced. Next on the list is too fit the new brush holder and adjust the timing of the brushes.