The Swift Locomotive Works Bell Crank connects the Throttle Quadrant to the Air Seal, and is mounted roughly halfway down the length of the boiler. The Bell Crank compensates for the thermal expansion of the boiler. When the Engineer fires up his engine and takes the boiler from ambient temperature up to operating temperature, the boiler expands. With an old fashioned through-boiler throttle, this expansion tends to open the throttle valve without the Engineers knowledge. The Bell Crank will automatically counter-act the thermal boiler expansion; thus the steam throttle valve will not be unintentionally opened.

Bell Crank picture showing components of the Bell Ctank Assembly
  • Three Lost Wax Castings in 316 Stainless Steel
  • Mounting plate fabricated of mild steel for ease of welding to your boiler
  • 8-32 (Left Hand) Threads on Clevises

The clevises are tapped with a left hand tap so that the rods which connect the Bell Crank to the Air Seal and the Throttle Quadrant can act like a turnbuckle, making adjustments to their length extremely simple.

Bell Crank ------------ $153.98

Please contact us to check on the availability of parts.

Contact Info

  • E-Mail:

    SwiftLocomotiveWorks at gmail dot com

  • Mailing Address:

    1501 Kestrel Ct
    Norman, OK.

  • Phone:

    (405) 990-1323


Below is a video of the Bell Crank which will further explain its features

Clicking in the lower right corner to expand to full screen