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 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.
Terrific idea -- have you had the chance to try this setup yet?
I tried it out at the recent workshop. Unfortunately the bottom of the injector was a little too low and it was banging on the top of mixer blades. We were pressed for time and so we continued to use it like that until the constant banging finally broke it. It's important to get the bottom of the injector close as possible to the blades, but if it touches that's definitely too close. The other problem I had was getting the dang chuck tight enough. The mixer paddle fell out a few times while mixing and the key just didn't seem to fit right, even though I'm pretty sure it was the original key.
Overall I think this setup could be very practical and could be an excellent solution if done properly.