Not with a Pump, but with a Canister

Every time the whole family is getting ready for a vacation, I have the task of checking the condition of our bicycles. As a rule, all the parts are in perfect order, except for the tires: they need to be inflated periodically. That’s when you sometimes have to work up a sweat, and a lot of time is spent on it.

I needed to invent a device that would replace the pump. I borrowed its main parts from… a home soda water siphon. The operating principle of the device is very simple. Carbon dioxide enters the inside, evaporates there, creating excess pressure that the tires need.

The overall appearance of the device is shown in the figure. It consists of a housing 1 into which a CO2 cartridge 2 is inserted, a cover 3 that has a needle 4 for piercing the cartridge plug. A hose 5 from a bicycle pump is screwed onto the housing. The tightness of the joints is achieved by means of rubber gaskets 6 and 7.

The housing and the cover are turned on a lathe from steel. Two holes are drilled in the cover: 2.5 mm in diameter to a depth of 3 mm for an M3 thread — for installing the needle, and 4.2 mm in diameter to a depth of 6 mm for an M5 thread — for installing the hose from the bicycle pump. Two plates 8 and 9 are welded to the housing and the cover — ribs for convenient tightening.

The needle for piercing the CO2 cartridge is made from an M3 screw at least 20 mm long. Its head is filed off, a slot is cut with a metal saw along the length of the screw to a depth of 1.5 mm (for the carbon dioxide to pass through), and then it is sharpened into a needle. After the needle is installed in the cover, it is locked by hammering a construction dowel whose tip deforms the threads of the needle and the cover (item 3, bottom).

A rubber gasket made according to the drawing is glued to the outside of the cover with Moment adhesive.

The hose also needs to be modified. The part that is screwed onto the pump is removed from it. A similar fitting is made, but with an M5 metric thread. The hose is connected to the housing through a rubber gasket.

Tire inflation is done as follows. The CO2 cartridge is placed in the housing, the cover is put on it and lightly screwed on. The bicycle hose is connected to the cover and then to the tire valve. By rotating the housing and the cover, the CO2 cartridge is pierced. A slight hissing will indicate this. After the contents of the cartridge have been released, the bicycle hose must be unscrewed from the tire. If the pressure in the tire is insufficient for normal riding, the tire will need to be refilled with carbon dioxide. If the pressure is higher than necessary, the excess carbon dioxide should be released from the tire.

This device can also be successfully used for inflating balls. It will also be useful for water tourism enthusiasts, anglers, and hunters: it will instantly inflate a mattress or a rubber life ring, inflatable pillows, and seats. With this device you can also refill an aerosol can that has been appropriately modified.

“Modelist-Konstruktor” No. 10’2009, S. SEMYONOV