Here is a note by Joseph Galamb on changes made to the steering gears in September 1919. The changes are not documented in most Model T repair publications, so I am posting it here for general reference.
On 9-17-19 Joseph Galamb wrote:
Change the pitch diameter of gear teeth on the following parts (T-916) from 14 to 14-18 with 20 degree pressure angle. This change is made to reduce friction between gears and is to take effect as soon as the change can be made without holding up production.The parts on hand to be balanced and used up. Note: owing to the wear on these parts when in used (sic) it will not be necessary to hold the present design, that is, parts having straight 14 pitch teeth for repairs.”
Interpretation: the steering gears used on cars made before October 1919 had teeth machined with a straight 14 pitch. After that the steering gears had teeth that were made with a slightly different shape, 14-28 with a 20 degree pressure angle. Technically, mixing up the gears with different shapes is not a good idea, but Galamb thought that because of naturally occurring wear there wouldn’t be a problem.
With the introduction of 5 to 1 steering the gears were stamped with the number 4 or 5 depending on the gear ratio. All gears were made after October 1919 were made with the later 14-18 and a 20 degree pressure angle.
Source: Record of Changes for T-916AR Card #1
Respectfully submitted,
Trent Boggess
Note on Steering Gears
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Dan McEachern
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Re: Note on Steering Gears
Trent- do you have the specs for the pre '19 gear pressure angle? Is there any mention of changes to the gear case teeth or did those stay 14DP? Were the pre '19 gears 14.5 deg PA ? Thank you for posting this information.
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TrentB
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Re: Note on Steering Gears
Dan,
The Record of Changes for the steering gears (the sun, the planet and the gear case itself) do not list a pressure angle for the teeth before the change in 1919. The Record of Changes simply describe them as having “straight 14 pitch teeth”. I do not have the part drawing for any of the gears made before October 1919, so I cannot say if a pressure angle was specified for them or not.
Sorry I cannot be of more help on this.
Respectfully Submitted,
Trent Boggess
The Record of Changes for the steering gears (the sun, the planet and the gear case itself) do not list a pressure angle for the teeth before the change in 1919. The Record of Changes simply describe them as having “straight 14 pitch teeth”. I do not have the part drawing for any of the gears made before October 1919, so I cannot say if a pressure angle was specified for them or not.
Sorry I cannot be of more help on this.
Respectfully Submitted,
Trent Boggess