Hartman timer

[Will_Vanderburg]

A.C. Hartman patented a contact for timers in 1923.

I have one, and have never seen another. Anyone else on here have one? Do you or have you ran it?

[Les Schubert]

Looks like a nice unit, I think you are lucky to have it!! If it was mine, I would install 4 capacitors (one at each connection to ground) and carefully lubricate the rotor contact areas to extend its service life.
If you would like to sell it, please contact me!!

[MKossor]

Les, The contacts probably open too slowly for a typical 0.47uF capacitor to afford much protection against contact arcing. The capacitor value would have to be MUCH larger to be effective in suppressing contact arcing. You can't use a large capacitor across coil points because you need the field to collapse rapidly shortly after the contacts break but you can use a larger value on timer terminals since the cylinder has already fired and the timer contact break is not responsible for ignition spark. There is an upper limit on capacitor value however, because the capacitor connected across all timer terminals effectively conducts Magneto current from EVERY coil timer terminal to engine ground. The risk with too large a capacitor value is ALL coils firing spark for EVERY magneto pulse regardless of timer roller/brush/flapper position at high engine speed due to the increased voltage and frequency of the magneto output. There may not be a optimal value of capacitance that effectively suppresses contact arc but does not cause simultaneous firing of all coils at every magneto pulse at higher engine speed.