I'm struggling with the measurements. The flange diameter I've measured at 109mm.
I can measure the distance inbetween the flanges easily enough but how do you measure where the hub centre is? Is it the other measurement I've marked on the pic below? I haven't got a vernier caliper so I think I need to get one.
You only need to worry about the hub if it is not symmetrical as shown on the wheel pro help. So as your flanges are symmetrical between the axle nut faces distances on both sides C & D are 37mm/2
i.e. 18.5mm though measuring with my calipers I get 37.5mm so use 18.75mm. Also i measure 108mm between flange hole centers which are the same both sides A & B.
You then need the actual rim diameter which you can get by following the instructions
here
I have measured the stock Brompton 28/36h rim several times and constantly get 338mm. Note this shows you how you can't rely on and use the manufacturers published ERD specs i.e. in this case 349!
So we have
A = 108
B = 108
C = 18.75
D = 18.75
Rim Diam = 338mm
Spokes 28
Putting that into the wheel pro calc I get spoke lengths as
R = 115mm
1x = 122.6 (one cross)
Using your measurement I get R = 114.5 so there really is nothing in it plus I always find the wheelpro calculates a little short for smaller wheels, so I would add at least 1mm longer anyway
So we have
Radial = 116mm
1X = 124mm
I have only built your hub into a Brompton stock 36h rim (I got blank ones drilled for 36h as I only had 36h Tongxins) but the calculation works out the same for radial in both cases. Suggest you double check yourself for your own peace of mind
Finally depending on how deep the counter sinks on the flange holes are you may need to use washers alternate holes or you will see daylight through them, though looking at the original wheel I think they did not use them you you will probably get away with doing it without. Radial on small wheels is by far my favorite but I am not sure I would have been confident using it for my first build. My first few builds were all x1 (1 cross).
Re the washers I had to do it on the smaller Goldant motor I fitted into a 20" rim as the countersinks were really deep alternate holes.
Regards
Jerry