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Pneumatic Bell Ringer

The solenoid solution (previous page) wasn't loud enough and didn't want to revisit that solution.  A pneumatic bell ringer would be much nicer.  Several attempts were made over the past few years to make a good working pneumatic bell ringer.  Below is what persistence is about.  Actually, the picture below shows only a portion of the failed attempts as parts were reused to fit other designs.  Need I say a ton of time was spent making this scrap. 

Finally, after more tinkering, I settled on a design that worked very nicely.  It only required a few parts but the machining was the key. The piston/cylinder was made small enough to fit in the bell cavity (about 5/8"W X 1"L).  To regulate the ringing speed, an air chamber was needed. This air chamber ended up being over twice the size of the piston/cylinder.  The overall size of the entire unit just about filled the upper portion of the bell.  Everything needed to be machined precisely.  Passages had to be made using tiny drills (#78 .014").  All the o-ring grooves had to be made so when the o-rings were installed on the piston, they were loose enough to easily slide with minimal friction but tight enough to seal the air cavities.

This bell ringer works on the same principle as the full scale ones.  If you need details, get one and take it apart.






One of the issues was the small scale bell clapper which is too light to reset the ringer once it extended to strike the bell.  Adding weight to the clapper would work but that made the clapper too large and looked like crap.  After playing around with it, a spring with just the right amount of tension was used to pull the clapper back. 











The air supply is regulated down to 50psi for the brakes, therefore it was important that the bell ringer operates at that pressure.  The bell actually works at a range of pressures from 30-120+ psi.  The only difference is the force the clapper strikes the bell and a slight variation in timing. 

Here it is.  I hope this works well over time as I really don't want to revisit this again.



Bell Ringer on YouTube








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Last modified: 02/02/2018.