Step 1: Supplies
- An old inner tube. Only valve needs to be working.
- A tube that a lego pneumatic hose will fit snugly on.
- Glue. I used hot glue.
Step 2: Assemble
1. Cut the innertube valve out.
2. Insert the tube into the end of the valve.
Step 3: Done.
I found this to work extremely well. Filling my small air tanks took 30 pumps with my lego pump and 2 with a SMALL bike pump.