PLEASE READ THIS ENTIRE POST VERY CAREFULLY
so i now have proof of concept on these brackets. after a few trials i have a final design that allows the spal 5.2 inch fans to fit on the 51 as simply as possible. these will fit both sides without scoops, and the LEFT SIDE ONLY with scoops. the scoop for the right side is simply too small for the 5.2" spal fan.
before i go any further, i need to make a few disclaimers. these are non-negotiable and are absolutely take it or leave it.
1. these brackets are designed for the geometry of the SPAL 30103011 and 30103013 fans. i will not be making any brackets to suit the fan you have. if you don't have one of these two, i will not ensure that whatever it is you have will fit.
2. these brackets are sp2 only. i'm not going to do a run of sp1 brackets because for one i don't have an sp1, and for two the fan i have won't fit in a right side scoop, and three it would require a much more complicated bracket or the manufacture of additional parts
3. if you think you can design or build it better and want to tell me what i did wrong, your cries will fall on deaf ears. this is the design i have, the drawing is done, it is what it is.
so now that we've gone over that part, here's the proof of concept and pics of how it all goes together. i understand that the fan overlaps the front of the rad slightly, it's a very tight fit in this stupid bike, and to clear the frame spar on the right and the scoop on the left, this is just how it worked out. it should have minimal effect on cooling.
here are the two brackets.
this shows the orientation of the bracket on the right side rad
here it is with the fan attached. note that the bracket sits on top of the tabs on the bottom of the rad, and underneath the tab on the top of the rad. this helps the fan sit flatter.
here is a view from the top. the fan sits reasonably far off the rad, which i suspect will help with airflow when the fan isn't running, and also mitigates risk of rad damage from the fan itself
a view from the front. fits nicely in there