Down-n-Dirty DIY Foam Injector
I've made 4 batches with this rig and it works fine. This is a universal injector compatible with most paddle mixers, probably even double-paddle mixers. The PVC pipe that is floating around the drive shaft is only there as an anchor. At the bottom it connects to the actual injector tube via bailing wire. I drilled two holes about 1/4" apart into the anchor pipe and did the same with the injector tube so I could "sew" them together with the bailing wire. The injector is 1/2" pipe which plugs directly into my Little Dragon wand. This design may perform even better with the point of injection brought down a couple inches closer to the paddle, but this works pretty well as is.
Concept design credit: @hajjargibran
Construction time: 5 minutes
Min age required: 5 yrs
Here's my updated version. After using the previous Down-n-Dirty I found that A) it worked quite well, but B) It was noticeably slower than the standard injector, and C) the wand popped off several times at critical moments of foam injection. In this edition I brought the end of the injector right down to the blades with only a 1/4" to spare, and I used 1 1/4" pipe instead of 1/2" pipe to reduce back pressure and increase flow rate. I expect this to work even better than the first try.