Worm Gear Steering for the Model T
WORM GEAR STEERING FOR THE MODEL T
Side cutaway view of the worm steering gear assembly. The steering arm is at the bottom; the arm moves horizontally. The standard drag link is used but with the ball socket turned upward.
The assembly was factory number T-983, T-4128, or T-5010, depending on the year used.
Top View of the worm steering gear. Note the position of the steering arm which moves in a near horizontal plane instead of the normal near vertical plane.
The teeth on the sector gear are not shown. The sector gear cover was held with three screws which were locked with a retaining wire as shown.
The top of the steering column for the worm steering gear. The illustration shows the early style gear case and steering wheel. Note that there are no gears in the top case; the steering shaft (T-500B) is solid from the steering wheel to the worm gear assembly on the frame. The steering column and gear case under the steering wheel are the same as the standard units.
Over the years in our research at the Ford Archives, and in literature we have collected, we have found many references to “worm steering gear.” The factory numbers were, for the most part, in the T-900’s but we could find no reference to part numbers, nor to what or when this type of steering gear might have been used. We presumed these were just “experimental.” Worm-gear steering on the Model T? It really happened, and not for an experiment either.
The first design of this system appeared in 1910, and specified for 1911 cars. Modifications were made at least until 1920, according to the original blueprints from which these illustrations are copied. The initial design had a ratio of 5:1 but within the first year this was changed to 7:1, perhaps to reduce the tendency for the wheels to effect the steering wheel when some obstruction was met on the road. Factory shipping records indicate that a Town Car, serial number 48,955, which had “worm steering gear” noted on the record, was shipped to Germany on April 21, 1911. Perhaps this type of steering gear was required in Germany.
Cars shipped to Germany apparently also had to be supplied with rear wheel brakes which could be operated by the foot pedal. Ford made a cable setup which connected the pedal to the rear brakes just for the German market.
Following are a few notes found at the Ford Archives regarding the worm steering gear. These are not necessarily all the notes on file; just the ones we noted.
DEC 15, 1910Acc. 575
T-972 worm, and T-973 sector steering parts. Blueprints indicate that these parts were never used but the worm gear assembly apparently was used until at least the early 1920’s. Probably the part numbers were changed; we do know that the original sector gear was just a sector but that it was replaced with a full round gear 1911. The left-hand engine pan (T-2367) was also designed for this type steering.
FEB 20, 1911(Factory Letter 277)
T-5015 Steering gear case (for worm steering gears). New drawing.
T-904 Steering gear case specified to be used with regular steering gear.
T-983, T4128 and T5010 Worm steering gear assemblies.
MAR 16, 1911(Factory Letter 284)
T-991 “Changed name from steering worm sector to steering worm wheel. Have also specified this piece to be a complete wheel instead of only a sector, thereby allowing the wheel to be turned around from one side to the other as the teeth become worn out. This will allow one piece to be used twice as long as before.”
As with the worm steering gear, numerous references were found to brake cables. It seems that those cars shipped to Germany were equipped with cables to the rear brakes instead of the usual brake rods. The rear brake arm clevis was designed to accept and clamp to the cable. It was designed to fit the standard brake arm and was angled so that the cable had a direct pull to the front brake lever arm. The clevis at the front brake arms had pulleys. Since the records show only one cable per car, we presume the cable passed over this pulley and across the frame to the other pulley and then back to the opposite rear wheel. Such an arrangement would tend to equalize the brake action. On the other hand, the records indicate there were four cable clamps required per car. Did they use two clamps at each end, or was the cable arranged so that instead of crossing the chassis, as above, it went through the front pulley and then back to some point on the chassis where it was anchored? This would give a mechanical advantage of two-to-one. (We presume the cable, listed as fourteen feet long, would have been cut into two pieces.) Perhaps the Germans required a more effective rear brake than the standard arrangement provided.
Following are some of the notes regarding the cable brake system.
JAN 5, 1912(Factory Letter 261)
T-4322 Hub brake cable. Changed from 12 feet to 14 feet.
T-4335 hub brake cable clamp. Changed number required from 8 to 4.
T-4333 Hub brake cable assembly. Removed the cable clamps from one end and showed the cable to be fastened by being wound with fine brass wire (#20 B&S=.032) and soldered in place.
JAN 15, 1912(Factory Letter 265)
T-4334 Hub brake cable pulley. “Change radius at bottom of groove from 1/32 to 1/16″.”
JAN 18, 1912(Factory Letter 267)
T-4322 Hub brake cable. Changed diameter from 1/8 to 5/32.
T-4334 Hub brake cable pulley. Changed radius at bottom of groove for cable from 1/16 to 5/64.
JAN 24, 1912(Factory Letter 268)
T-4333 Hub brake cable assembly. Changed size of cable from 1/8 to 5/32. Also changed size oef cable clamps.
FEB 8, 1912 (Factory Letter 398)
T-4332 Hub Brake Cable. “We have changed the diameter from 1/4″ to 15/64″.” Had also changed the size of the wires and the number of wires that made up this cable.
© Bruce W. McCalley. Rev. February 11, 2007