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.