Build - Steamless "Boiler"

A Steamless "Boiler"

What the heck is a steamless boiler!? Well, it's not really a boiler at all, of course. Rather, it's a small compressed air tank which can be used to run model steam engines. Unfortunately it doesn't hold much air, so run times are pretty short, but it does have these advantages:
  • small and light
  • very portable
  • fits easily on a bookshelf or tabletop
  • easily rechargeable

The picture to the left shows the "boiler" connected to a wobbler engine I built. Fully charged, it can run the engine for about two minutes - not very long, but long enough for a quick demo, and much more convenient than using the compressor in my garage, or a large portable air tank.

This was a fun cheap project, but it was cheap only because I picked up the "boiler" for next to nothing (a new one would have cost around $60 - $70).

The heart of the system is a "Sure Shot" sprayer I picked up at a garage sale. A quick web search shows that the Sure Shot is still manufactured and sold by Milwaukee Sprayer. As you can see from the photo below left, the unit came with a brass spay nozzle, a pressure gauge (probably a later add-on replacement for a relief valve), handle with thumb trigger, and a bicycle type valve for pressurizing (the valve assembly also unscrews so you can fill the container). I had no idea if the unit still worked, or would hold pressure, so I was pleasantly surprised when I got home to find that it was in perfect working order, although a bit scratched up and dirty.

 The "Sure Shot" sprayer as purchased.
 Close-up of label.
 Close-up of label on reverse side.

I removed the labels with some solvent, cleaned the outside thoroughly with some "soft-scrub" kitchen cleaner, and gave it a nice polish. The plastic cover on the pressure gauge was a bit yellowed, so I removed and cleaned it also. I unscrewed the spray nozzle and replaced it with a pressure regulator, using a custom machined adapter (and another adapter on the exit side to fit plastic tubing). 

A hardwood stand was constructed to hold the unit (red oak coated with clear wipe-on polyurethane). The stand includes a levered cam to activate the thumb trigger and quickly turn the air supply on or off.

A pressure regulator (top) replaces the spray nozzle.
 A levered wooden cam acts as an on-off switch.

Using my small pancake compressor, I am able to pressurize the unit to about 100 psi; this is sufficient to run a small wobbler engine for about two minutes. Here is a short video of the unit in action (click photo to see video):