Sparton Horns were fitted on many American makes. The ones pictures are Hupmobile and an internet search revealed that Ford Model A used a Sparton unit and the images on Snyders antique auto site were sufficiently accurate and very reasonably priced for taking a gamble and ordering the needed parts. When these arrived, all but the main diaphram and the motor cover were identical. The diaphram was slightly smaller but was made to fit by slotting the bolt holes, the cover was a mere 1/4 inch too shallow but identical in every other respect.
The rusted out original diaphram and the replacement A Ford item. It was made to fit this application with very little effort.
The trumpet needed some love and attention as it too had suffered from the rust problem. The 2 small offset holes at the bottom center position are a drain and a for a location pin.
The actual motor was treated to new brushes and brush springs straight from the replacement Ford parts. The windings were given an insulation test and the main leads were sleeved in heat shrink tubing since the original cotton had begun to fray. New insulators were made whre the electrical studs pass through the metalwork and it was successfully test ran. Polarity seemed to have no effect on rotation direction.
Snyders have on thier site most parts to suit this brand of horn and for the whisker over five dollars for the diaphram and eight for the motor cover I was prepared to take a risk on them fitting. Delivery to Australia was less than a fortnight and they were a treat to deal with, Promptly answereing emails and adding the requested identification plates (all of a dollar each) to the order. Other non horn parts were also put on the same order to make it worth the postage cost - the site is well worth a visit.
The picture at left shows the parts cleaned up for 2 horns and waiting reassembly. The rusted horn cover got the fiberglass treatment after neutralising the rust issues and since the pinholes were on the underside it presents well fitted up on the car.