Back to basics.

[DAMIEN1307]

shots of the caliper bracket for the 203mm disc brake and the 48-tooth sprocket.

I am really, really, hoping that your not thinking that just the axle nut is gonna hold that caliper adapter all by itself.
The force of braking with the wheel turning, under power, etc will tear that back end of yours all apart with much damage and possible injury resulting, especially with a panic stop...The basic Laws of Physics apply here.

Take a look how I did it below, it hasn't budged in 5 years of constant riding and has never loosened up on me either.

shots of the caliper bracket for the 203mm disc brake and the 48-tooth sprocket.

This was how I did my caliper to frame adapter on mine 5 years ago for my 203mm rear disk brake.
There is a two pronged fork going over the end of the axle and bolted in place with everything else with the axle nut, you will also see that small bolt closest to the axle nut where there was already existing holes in the drop down fork as well as the allen head bolt.

I drilled 2 holes through the caliper adapter to match the holes already in the frame as 2 extra points of hold down coupled with letting it rest against the heal of the drop down frame as a brace as you can see in these twoo pics.

This was home made from 7075 T-6 military aircraft quality aluminum at the same time the homemade front motor mount was made 5 years ago.

 

[wrenchin 4 fun]

I agree, Damien. Don't know if you can see in this photo, but I bolted a steel brace to the caliper and clamped it to the frame. A welded mounting point would be stronger, but I don't want to alter the vintage frame. Will probably look for a more robust clamp later.

 

[DAMIEN1307]

I agree, Damien. Don't know if you can see in this photo, but I bolted a steel brace to the caliper and clamped it to the frame. A welded mounting point would be stronger, but I don't want to alter the vintage frame. Will probably look for a more robust clamp later.
View attachment 231247

It is also not advisable to have such a high heat source like that muffler so close to the brake pads, caliper, and disk rotor either, not to mention the axel and bearings are going to overheat as well.

 

[Johnny_]

It is also not advisable to have such a high heat source like that muffler so close to the brake pads, caliper, and disk rotor either, not to mention the axel and bearings are going to overheat as well.

I will venture to disagree here lol. On my bike I have the expansion chamber and then the muffler. Even on long rides I can keep my leg against the expansion chamber, and the muffler is scarcely warm. Of course it will vary case by case, but I think he should be perfectly fine here.

 

[DAMIEN1307]

I will venture to disagree here lol. On my bike I have the expansion chamber and then the muffler. Even on long rides I can keep my leg against the expansion chamber, and the muffler is scarcely warm. Of course it will vary case by case, but I think he should be perfectly fine here.

Time will always tell Johnny, there are times in my life that I have been wrong, but not too many...lol...lol...lol.

 

[wrenchin 4 fun]

Moved the muffler forward quite a bit to get it away from the rear wheel, more for ease of access than concern about heat. The muffler does get hot, but it was too far away to fry components.

After moving the muffler I went for a ride with wifey on her electric bike. The new setup is spot on. The gearing is very rideable, and the drive train is smooth and quiet. The way it rides reminds me of my old Whizzer that Hurricane Irene ruined. The main difference is the advantage the hub gives me on takeoff. It's fairly quick off the line for a 50cc water pump engine. I cruise in 2nd gear when riding with wifey, but slide into 3rd for flat out cruising. Haven't checked yet for max speed, but that's coming as soon as I swap out my 8" long jackshaft for a 5 incher from the parts bin.