I have a couple of Hero Hybrids just collecting dust since I converted to bottom feeders. If you are not familiar with them, they are 18350 hybrid mods with a battery tube on one side and a liquid bottle below a coil chamber on the other.
The top has a drip tip recess just above where the chamber screws on.
Inside the top there is a brass bar that holds the switch assembly to the drip tip chamber / coil deck and also is used to pass the positive from the switch to the deck. The whole thing is held together with 1 screw through the top to the bottom plate.
One of the big downfalls of the Hero is the switch. The current goes from the battery through a nickle plated brass screw to a nickle plated post then through a tiny spring to the spring cup and across the brass bar. This creates a large voltage drop. The battery negative spring is also way less than adequate and the negative passes through a maze of parts and connections including the screw that holds the top and bottom plates together.
What's this got to do with bottom feeders? Well just because I though it would be a challenge and I have them sitting around not being used I decided to convert one to bottom feeding and improve the voltage drop at the same time. I only used stuff I had laying around since I didn't want to spend anything on doing this. Found that a Fat Daddy classic 510 fit perfectly in the top cap holes and with the brass nut on the opposite side it was just a smidge proud on the top.
Also, it was way too long so I made probably the shortest Classic 510 around. To hold it in place I ground off the nickle plating on the bottom of the top cap and soldered the round brass nut to the top cap along with a wire to connect to the bottom plate so the current doesn't have to go through the screw that holds the top and bottom plates together.
Here are the parts I used for the 510 interior and post. I ground down an already broken classic insulator, used a female threaded part from a 510 adapter with a piece of silicone tubing under the head and cut the head off an older Reo 510 center pin to sandwich a small metal plate with a wire soldered to it for the positive. I soldered a silver pin to the factory switch along with the wire. (note the switch plunger would be turned 180 degrees from what I had it layed out to take the picture)
I slotted the switch cup so the wire could come out and used a classic insulator which was the same thread as the original along with another silver pin for the battery connection. I enlarged the inside of the insulator just enough on the battery side so the pin would be snug and 1 wire size larger on the other end so the switch pin would slide inside the insulator. It sits just inside the insulator when not pressed about 1/8 inch.
Also needed something to hold the 2 battery tubes I planned on using so I ground the nickle plating off the bottom plate and soldered 2 pieces that the battery tube screws into having removed the plating from them along with the negative wire from the top cap.
Had a little solder seep through onto the threads on one side I had to file down with a jewelers file.
Now for the bottle. I used a "fancy Italian bottle" which fit inside the extra battery tube but the cap wouldn't fit. I used a silicone cup washer from some Kangertech heads which the open end fit nice and snug in the bottle opening but the top end wouldn't quite go through (with silicone tubing that Turbocad set me on to a long time ago) going through the cup washer and the Reo pin in the tubing) I used a piece of #12 silicone wire insulation to hold the cup washer at the proper distance from the 510 to make a good seal.
The hardest part for me was the squonk hole since everything was done with a dremel, a torch, and a soldering iron since I don't have any fancy milling or lathe equipment. I drew it in marker and used a small cut off wheel and small sanding drums. That was some thick metal, just glad it was brass. So here it is along with an unmodified one and a Pinch, 18350, and 18650 for size comparison.
I must have left the hot spring I had in the one I sold so it has the crappy thin battery negative spring but the improvement is drastic anyway. I will see about using a different battery spring when I can and measure voltage drop then. It's an 18350 so I don't expect it to be an all day mod, I did it just because I wanted to. The other one I might get a hankering to see if there is anyway to make that liquid bottle a squonker and keep the hybrid chamber and reduce the voltage drop. The vape is pretty darn good with the hybrid deck and chamber, but the voltage drop sucks and I only squonk after Pdib and Xobeloot converted me.