Instructables
Problem: The small nozzles which came with a foot-powered bellows pump did not fit the large inlet holes of my air mattresses. The largest nozzle was about 0.5" diameter (12mm). The inlet in my air mattresses is 1.25" (31mm).

Solution: I fabricated an adapter from junk parts (a plastic funnel, bicycle inner tube, and some copper wire). Adapter works great. It stays well inserted while foot-pumping. Inflates mattresses fast. Project consumed 45 minutes.

Parts and Procedure: See subsequent pages.

Side comments:
- My original plan was to slide the inner tube over the large end of the funnel. Too difficult with the size tube on hand. So I routed it inside as shown.
- Even then, sliding the tube over the small end of the funnel was difficult. Dipping in water helped. Next time, I would use a larger tube.
- Shrink-wrap tubing over the copper wire ends would be nice. Remember to slide it on the hose beforehand. (I forgot, as usual.)

Enjoy easy pumping with 'yer foot.
 
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Step 1: Parts

Find the following parts in your scrap heap:
- A section of long-neck plastic funnel. Mine was intended for changing auto motor oil.
- A bicycle inner tube. Use a section without patches.
- Some small solid copper wire. I used insulated telephone wire, about 24awg.

Optional:
- Large diameter shrink wrap tubing. (I did not think of this soon enough.)

Step 2: Procedure 1 - Funnel Section

1) Insert the funnel snugly into your air mattress inlet hole. Mark the funnel where it contacts the mattress inlet hole. Remove the funnel.
2) Cut out a section of funnel about 1" (25cm) on either side of the mark. Wear safety glasses.
3) Carefully remove any fuzz and deburr sharp edges. Use utility knife, file, or sandpaper.
4) Optionally, cut a short narrow groove near the large end of funnel section. This will help retain the copper wire used in a later step.
pcooper2 made it!20 days ago

I encountered a similar problem several years ago. The air bed came with a rechargeable battery-powered electric blower to inflate and deflate it, but I couldn't rely on it when camping for a week or more, because the charge would drain away and over time the batteries got weak, so I always carried a bellows style pump, just like the one shown above. The problem with the bellows pump was that none of the included nozzles fit the air bed valve. My first attempt at solving the problem consisted of a simple PVC ring, turned on a lathe to slip onto the end of the hose and allow it to plug into the valve with a reasonably snug fit. It worked, but was not entirely satisfactory, especially when I used the pump in reverse to deflate the air bed.

The one shown in the photo here is one of two new air bed valve adapters I fabricated on 2014-08-26. It is made from a 3/4-inch NIBCO PVC slip pipe cap, a short piece of 3/4-inch Schedule 40 PVC pipe, a short piece of 1/2-inch Schedule 40 PVC pipe and a 1/2-inch PVC slip coupler.

The outside of the PVC cap was turned on my Sherline lathe to a diameter of 30.85 mm to provide an interference fit in the air bed valve. The 3/4-inch PVC pipe was bored out to provide an interference fit on the end of the pump hose. Due to PVC readily expanding due to heat generated by the turning operation, this was done carefully, cutting the diameters a few hundredths millimeter shy of the target value, then using the edge of a 3-edge deburring tool as a scraper, the parts were scraped on the lathe until the desired fit was achieved. The 3/4-inch pipe was then cemented into the PVC cap, reducing its inside diameter.

Next, a hole was bored into the end of the cap to accept a piece of 1/2-inch PVC pipe. The hole was slightly looser than normal male and female PVC fittings, allowing the pipe to slip into the hole without resistance. A small ring was turned and cut from the 1/2-inch PVC coupler, its outside diameter sized to fit into the sleeved 3/4-inch PVC cap. Two transverse holes were drilled into the 1/2-inch pipe and brought to final size of 3/8 inch with a Unibit step drill. The PVC ring was cemented onto the end of the 1/2-inch PVC pipe. After 10 minutes the ring and pipe subassembly was cemented into the PVC cap, producing the finished part shown in the photo. This had to be done carefully, to prevent cement from contaminating the inside of the PVC cap where the pump hose plugs in.


The purpose of the projecting 1/2-inch pipe with transverse holes is to push the inner flapper check valve out of the way. The multitude of holes assures that the end of the pipe cannot get obstructed by the flapper valve or air bed wall material. This is not essential during inflation, but is very helpful in deflating the mattress. The adapter can be plugged into the valve to allow the air bed to deflate on its own, and then the pump can be connected at the end to suck air out until it is completely evacuated. The 1/2-inch pipe inside diameter is slightly smaller than the inside diameter of the pump hose, but since air is compressible, it doesn't cause excessive throttling of the flow. The four transverse holes in the pipe actually have a larger combined cross-section area than a piece of 1/2-inch Schedule 40 PVC pipe.

air_bed_valve_adapter.jpg

During a camping trip over the weekend I discovered a drawback to my design: Even though the 1/2-inch extension does a great job of keeping the flapper valve open during deflation, it also deflects the flapper to such a large degree that it often doesn't close properly during inflation when the pump hose is withdrawn, causing a significant amount of air loss before one can get a finger into the valve hole and tease the flapper into place. I'm planning to try again, perhaps making a version without the 1/2-inch extension that is used only for inflation, or not gluing the extension into place, so it can be removed for inflation. In the alternative, one can over-inflate the air bed a bit to allow for air loss while the flapper is closed and the valve is capped. To get the bed properly inflated this time, I settled for partially inserting the adapter into the valve after I got the flapper closed to give it a few strokes of the pump, making up for the air lost during initial withdrawal of the hose. It's not ideal, but it works.

Bobblob5 years ago
Two major design goals are keeping things simple and effect. Looks like you have done both. Unlike many Instructables, your pictures are clear and informative. Well done, thank you.