I purchased a 9C cover from ebikes.ca to retro fit a disc brake on a 20" 9C ebikekit.com front motor I have. When any moutain bikers would ride my e-chopper the main gripe they had was that the bike did not have a front brake. The only way to get one on this particular bike was to either machine my own coverter-too much trouble, or to try one of these next generation 9C covers from ebikes.ca.
I machined the bearing recess so that it was 0.740" deep from the bearing cup edge on a lathe. You can see in the photos that gets down into the casting where there are voids. After I installed the cover back on the rotor something was rubbing which left the black/grey marks on the inside of the cover after a couple of days of riding. It looked to me like it was the threads on one of the tie downs for the windings, but it was obvious that trouble was brewing, so I took the motor apart again and machined a 0.500" wide recess 0.020" deep to try and eliminate the rubbing on a mill with a rotary table. This didn't work so I installed the original cover back on the bike and rode it that way for a week. After all the effort, money, and time I put into trying to make this work I decided to create a larger groove to give the internal components more clearance. I put the cover back in the rotary table and machined a 1.000" groove 0.035" deep. It works just fine now but the cover is only about 0.070" thick where the recess is (the cover is about 0.105" thick).
My take on the situation is that if you need a motor with a disk brake, and do not have a mill and a lathe at your disposal (you'll never mill the 1.000" groove in a lathe since the cover will start to chatter unless you make a dampening device), it is probably not worth the effort and money. You'll be well into 50% of the cost of just buying a new motor already setup to accept a disc brake.
I machined the bearing recess so that it was 0.740" deep from the bearing cup edge on a lathe. You can see in the photos that gets down into the casting where there are voids. After I installed the cover back on the rotor something was rubbing which left the black/grey marks on the inside of the cover after a couple of days of riding. It looked to me like it was the threads on one of the tie downs for the windings, but it was obvious that trouble was brewing, so I took the motor apart again and machined a 0.500" wide recess 0.020" deep to try and eliminate the rubbing on a mill with a rotary table. This didn't work so I installed the original cover back on the bike and rode it that way for a week. After all the effort, money, and time I put into trying to make this work I decided to create a larger groove to give the internal components more clearance. I put the cover back in the rotary table and machined a 1.000" groove 0.035" deep. It works just fine now but the cover is only about 0.070" thick where the recess is (the cover is about 0.105" thick).
My take on the situation is that if you need a motor with a disk brake, and do not have a mill and a lathe at your disposal (you'll never mill the 1.000" groove in a lathe since the cover will start to chatter unless you make a dampening device), it is probably not worth the effort and money. You'll be well into 50% of the cost of just buying a new motor already setup to accept a disc brake.
