andysworld!

Over a week ago, the socket ring main tripped, and shortly afterwards my vintage Hy-Flo Model C Air Pump stopped working, I don’t think this was the reason for it stopping, just coincidence.

Hy-Flo vintage reciprocating piston aquarium air pumps were manufactured by Medcalf Bros. Ltd. of Potters Bar, England. They ceased trading many years ago.

I think they were manufactured in the 50/60s for the laboratory and research establishments, universities and polytechnics some were used in the ornamental aquatics industries, but as they were expensive, many fish keepers, used Rena, Whisper or Hoffman pumps of that time. Most aquarium air pumps of this generation were manufactured from bakelite or plastic, and used a rubber diaphragm, which needed regular replacement due to wear, and were of the vibrator design. Most of the pumps on the market today use this design.

The Hy-flo pump is made out of a solid cast iron block, the Model C weighs approx 5kg, a metal flywheel moves between an alternating current electromagnetic coil (motor), causing the flywheel to start and rotate, the flywheel gets a little hot due to eddy currents induced in the flywheel, even if the flywheel gets jammed the flywheel can get very hot, if it does important to turn off, otherwise damage to the coils (motor) could occur. The flywheel spins on an axel/rod, at the end of the axel, cams connect to a piston and valve chamber which generates air.

My Hy-flo air pump, had stopped spinning. Using a electrical power meter from JLB Electronics, the Hy-flo pump was still drawing 50 watts of electricity, and the flywheel got very hot (see above eddy currents).

flywheel, pistons and cams removed

I removed the two piston assemblies and valve chambers but the flywheel still didn’t spin freely when power was applied.

just a block of iron

piston and valve chamber

cam from Hy-flo Model C

piston and valbe chamber

So I sent an email to Sonik Systems for guidance, they re-sale, service and repair Hy-flo pumps (Medcalf Bros. ceased trading many years ago). They advised me that because the flywheel was getting hot, but not spinning, the motor (electric coils) were still working, and it was either an alignment or dirt on the axel that was causing the issue. The axel could be moved, and was not rubbing against the motor (coil). Sonik Systems confirmed that the flywheel should spin freely for approx 30 seconds when pushed with power off. My flywheel was not free spinning.

back together after oiling

close-up of flywheel

The axel would not move freely by hand, so a small tap with a rubber mallet freed the axel. The moment that this was freed, the flywheel span for 40 seconds un-aided. I suspect due to build up of dirt, and the possible dry/humidity in the fish house, had dried out the oil, and the remaining hard residue had caused it to cease.

Hy-Flo Model C

All oiled and working