About Prototype Couplers


Investment cast Double Shelf compatible shanks machined and cleaned ready for packaging.

Prototype Couplers has been providing the world's most accurate model railroad couplers since 2023. Sergent Engineering was the first company to manufacture and sell a "true" scale size HO coupler. Sergent Engineering has since closed its doors but the dream lives on with us. We have worked with Frank Sergent to get these couplers back into hands of modellers. Frank has authorized us to use his tooling. This means our die-cast couplers are still original Sergent Couplers! Infact, our investment cast couplers all use original Sergent Engineering die-cast knuckles. We source our balls and springs from the same suppliers Sergent Engineering used. Our uncoupling wands are also sourced from the same suppliers. All our products(couplers, springs, balls, wands) are 100% made in the USA!

The quality and depth of our product line will change considerably over time. Initial offerings are in the form of investment cast shanks and bottoms with a die-cast knuckle. The investment castings are all made in house on a small scale. This production method is not without its drawbacks, and hopefully soon we can start utilizing the tooling Sergent Engineering has authorized us to use as it is better suited to higher volume production.

We start by 3D printing our parts using specialized resin. The parts are then cleaned and allowed to dry.We then sprue them into a tree with wax. Then prepare them for burnout. A 24 hour long process where the resin is burned out of the mold leaving a negative space for metal to fill. After burnout is complete we pour our molds using a zinc alloy. After the pour is complete parts are cleaned and allowed to dry. We then meticulously hand machine the parts so that a ball can freely drop in the hole and so that the shank will fit in a coupler box. After the machining process we break the parts off the sprues, reject bad parts and clean them once more. After the final clean we allow the parts to dry overnight. If blackening is requested we soak the parts in a 99% iso bath then we let them dry before soaking them in a zinc blackening agent. The agent is then quickly neutralized and parts are cleaned and left to dry. This is a multi-day process that requires a large amount of time and attention to detail.

In time we hope to expand our product line to match Sergent Engineering's old product line. This will take time but we are making progress everyday. Some items take months to fully develop. Keep your eyes on the news section of this website for any updates.

Prototype Couplers is a family business. It is run by solely by Alexander Woychosky. Prototype Couplers uses the same manufacturing processes that Frank Sergent at Sergent Engineering devised many years ago. For all intents and purposes Prototype Couplers is a spiritual successor to Sergent Engineering. We look forward to serving the model railroading community for many years to come!