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Bichronous Motor Hum


Registered User
Dec 12, 2010
Picked up a Hammond Postal Telegraph (military) Bichronous clock. When plugged in it ran fine for an hour or so and then started running slow and humming loudly.

I suspect it needs oiling. These are bugger bears to get to. The knobs are usually epoxyed on because the threads went bye bye a long time ago. (I think this is my 1st and last Bichron).

Anybody had a hummer before?


Registered User
Oct 26, 2011
Maybe someone with more experience will drop in, but here's my thoughts and observations on the one bichronous non telegraph model that I acquired that may apply. The two knobs on mine were not threaded but both split type and just pressed on and also pulled straight back to remove. If on your clock they are epoxied on then you have a problem on your hands. Don't know if heat from a small torch would break down epoxy enough to remove them. But on my movement once it was out I found was extremely stiff from old lubricant. And what with the numbers of gears being driven in these it most definitely would need a thorough and complete dis-assembly and cleaning to run properly again. The hum can be created by a loose coil over the laminations. Or if it's been worked on before maybe even loose mounting screws for that matter. Check to see if you can easily move the coil form they can shrink slightly over time. You would have to use a slim shim to reduce the vibration that causes hum. I've read this on another threads here. But never had this problem or needed to do this yet myself. Will be interested to hear others experiences with the hum problem and their fixes.


NAWCC Fellow
NAWCC Member
Aug 24, 2000
64Mustang writes in part: "When plugged in it ran fine for an hour or so and then started running slow and humming loudly."

This would be (in my opinion) an indication that the reserve spring is gummed up so badly that the outside coil of the spring is not able to slip in the barrel when the spring is fully wound. The unsuspected load is taxing the electric motor and it is hurting....hence the growling sound.

I don't have a Bichronous clock but I do have a badly worn and damaged movement that I have studied in the past and I believe that's the way they work.



Registered User
Oct 26, 2011
Didn't think of that aspect, but makes sense to me Eck. It does take some time to wind up that spring initially. The bichronous is an interesting design and certainly the most complex Hammond clock I've run across. Would be sweet if there was more info available on them. The only book I've seen on Hammond's doesn't cover it. I guess it's the red headed step child of his clock line ( or maybe the Rodney Dangerfield ). But knowing what I know now, I doubt I'd try to make one of these old soldiers run until I did an overhaul beforehand.


Registered User
Mar 18, 2011
Dallas, TX
Hammond clocks with the open rotor are easy to work with. Getting the knobs off can be a problem, before you attemp to remove the knobs, remove the hands first. For the time set knob use a butter knife pen and a paper towel. Put the paper towel down first then the pen, you use the pen as a lever and place the butter knife over the pen get the knife blade next to the stem and use an upward prying motion to get the knob off. Removing the priming knob it is easier with the movement attached use the same set up as with the time set knob. You may experience a little more of a problem with this one. If you have a clock hand removal tool use it to remove the knobs.

You can open the movement with the priming gear still attached, but it makes it hard to get any of the four other gears back in if they fall out. If you have never worked on one of these, get your digital camera out and take pictures of the gears intact in the clock. The center gear comes apart into two pieces, it controls the hands.

These are easy clocks to work on.


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