Hadley Fanny Pack Mod V1 (metric)

This little drop-in mod is intended to help equilibrate the temperature of your primary mirror to the surrounding ambient temperature.  In doing so, the fan turbulence will also help discourage condensation from forming on the reflective side of the mirror so you can view longer in humid environments (like here in Indiana).  the mod is supposed to be extremely simple to operate and maintain.  you can even charge it as-is, just plug your Hadley into the wall.   The battery is completely overkill for the tiny little fan so you don't have to recharge it very often.

Many of the parts in this mod are thin, so warping and layer adhesion may prove troublesome for PLA and almost certainly for ABS.  I printed these parts in PETG.  3 walls, 20% rectilinear infill at 0.2mm layer height.  None of these parts require supports to print.  Recommended printing orientation photo is in the highlight gallery above.

Disclaimer: This is my first multi-part CAD project using Fusion 360, so the parts are kinda messy on the design side and janky as hell on the assembly side.  Not all the parts in the CAD are needed for printing and there are some unused prototype parts left in the STEP files that do not have corresponding STLs on this printables page.  You only need to print the parts that I have uploaded to this page.

Designed for a metric Hadley with 12mm rods.

BOM

Electronics

• 12v 1200 mAh Li-on Battery Pack (with bare leads)
• 12v 4020 Fan
• DC 5V-35V 5A PWM Speed Controller

Hardware

• 1/8" Elastic Shock Cord or equivalent
• 5x M4 screws 10mm-14mm with or without thumb screws
• 7x M4 4mm long heat sets
• 4x M3 4mm long heat sets
• 2x M4x8mm socket head screws
• 2x M3x25mm socket head screws
• 4x M3x8mm socket head screws
• 2x M2.5x6mm screws

General Assembly Guide

proceed at your own discretion, I built this thing in a cave with a box of scraps.  I pulled this idea out of my imagination and the idea now competes with reality.  I am not an expert in anything.

anyway,

This image below shows the general locations of where heat sets are added to the printed parts.  to specify:

1. The fan ring has 3x M4 heat sets for the thumb screws.  this is just like marci's M4 heat set hadley remix.
2. The electronics box has 4x M4 heat sets.  two for the thumb screws and two for holding down the electronics cover.  
3. The fan suspender has 2x M3 heat sets inserted on the buildplate side of the print
   • note these heat sets are there to hold the fan case to the fan suspender, they are located on the edges of the fan
4. The fan case has 2x M3 heat sets on the buildplate side of the print.
   • note these M3 heat sets are there to hold the corners of the fan, not the edges.
5. Three short cuts of elastic shock cord are used to attach the fan suspender to the fan ring and dissipate the vibrations of the operating fan.  
   1. The shock cord is knotted on one end, fed through one hole of the fan ring, through the fan suspender, then through the closest next hole in the fan ring.  A second small knot holds it in place.  This is repeated three times.
      • these elastic bands only have to be pulled a little bit taught, and tension should be made so that the fan is suspended as centrally as possible. 
      • The main thing to consider is where the fan sits inside the LTA when mounted.  If it is not suspended close enough to the center, the fan unit will rattle against the inside of the LTA where the collimating screws run through to the mirror module

Disclaimer: I apologize in advance for how janky this entire process is.  Any feedback regarding CAD advice or future assembly considerations are greatly appreciated.

Here we go.

First, if you get the recommended fans, you can cut off the yellow wire like I did, as it is not needed.

Place the fan into the fan suspender.  

• Please note the orientation of the fan and its wires in the image below.  There is only one way this dumb thing fits together correctly but it's more ambiguous in hindsight than I intended.  That's right, I forced the round peg into the square hole.

Once you have the fan placed into the fan suspender, flip the fan case over and set it on top, make sure that you don't pinch the fan wires.  They have a channel to run through in the fan case print.  Use the M3x8mm screws to attach the fan case to the fan suspender and use the M3x25mm screws to hold down the fan and the fan case to the fan suspender.  I needed the redundant screw tension to eliminate fan vibration/noise.

The following image is for reference for the wiring only.  
Bear with me.  It's about to get really stupid.

…because the actual correct way to assemble this involves threading the fan wires through the smallest hole in the bottom of the electronics box, then threading those same fan wires through the smallest hole in the bottom of the electronics drawer, all before getting plugged into the controller!  I warned you about the stupid assembly.  Luckily for us, the fan wires are quite long in the fan set that I recommended, so this is really just a minor inconvenience. picture below for reference.

Once you've endured the super janky wire threading, use your two M2.5 screws to attach your PWM controller to the electric part mount.  Plug the open leads of the battery into the terminals on the PWM controller as shown, then screw the battery wires down in said terminals.

Next, unpin the wires from the JST connector.  

• To unpin them, I use a razor blade or a very small or flat screwdriver to poke the exposed metal parts on the one side of the plug and pull the wires while holding pressure on the metal tabs exposed on the plug.  

Once unpinned, embrace the jank and shove the free crimps from the fan wires directly into the PWM controller as shown in the image.  Screw them down into the terminal once they're in.  This is their new life now.

Finally, use two M3x8mm screws to entomb the battery charge port in its final resting place with the printed charge port cover.  make sure that the battery side of the charge port has the smaller wire cutout so that you can charge the battery without disassembling anything. 

You thought you could escape the jank so easily?  Wrong again.  
Bust out a hot glue gun and fiddle the PWM control knob through the largest hole of the electronics drawer while ensuring that you're not smashing the fan wire you threaded earlier. Once you wiggle that mess in place, carefully lift up the electronics mount and hot glue it to the inside of the electronics drawer, as seen in the picture below.  Press down the hot glue blob nice and flat.

Once you've finished committing all those building sins, slide the electronics drawer into the electronics box.  Make sure that the PWM controller knob fits into the hole in the bottom of the electronics box.  Then shove all the wires, and pain into the box with the battery, cable management be damned.  Slap the cover on, and bolt it down with two M4x8 screws.

…Some things are meant to be forgotten…

Believe it or not, that is the module completed.  Grab your Hadley and remove the LTA (assuming you already assembled it) and slide the electronics box on however is most convenient for you. Follow that up with putting the LTA back on.  The fan ring will be dangling from the fan wire at this point. (very classy)

The fan ring assembly should be able to fit in right up behind the LTA mirror cell.  It all goes in there, nothing should stick out.  The sticker side of the fan should be pointing inwards towards the mirror.  Don't worry if it isn't, since you only need to remove two screws to get to the fan.  

…The puzzle comes from putting the thing back together and getting everything lined up correctly.  Make sure that you're not pinching your fan wires between the fan ring and the LTA module.  I run the fan wires outside the fan ring, as pictured below.

The fan ring should slip over the collimation knobs.  It's a pretty tight squeeze and the knobs have to be oriented correctly for it to fit over them.  Once you have that fiddled together, the suffering is over for this project. Congrations, you done it.  

If you still want to use a primary mirror cover, you can, it just needs a little bit of modification and there needs to be some space between the LTA and the electronics box, as pictured below.  I'm using Gyoenastaader's Hadley mirror and lens covers.  To modify the cover, I literally just snipped off one of the three hooks with a pair of flush cuts.  you can also use the cut function in Prusa Slicer or orcaslicer (or equivalent tool in other slicers) in order to just make it print nicely without that third hook.