They made a wrench just for that, HCW 3: http://www.ebay.com/itm/Park-tools-s...item4169d2fa14

Non-box end 36mm, you need room to slip the wrench in there, but on a track crank that shouldn't be a problem.

Edit: Available cheap on nashbar, and it's probably the better laser cut version made right before it was discontinued: http://www.nashbar.com/bikes/Product...97_-1___203633