Modifing speedometer turtle

TerryOH

TerryOH

Well-known member
I want to use a 17 tooth turtle gear. As the gears have lower number of teeth the diameter of the gear get slightly smaller. I want to use a 19 tooth turtle housing and cut the arc into the turtle deeper so the new gear meshes with the drive shaft gear properly. Any suggestions as what tools to use to modify the turtle housing?
 
Terry,
Grab/fixture the turtle in your mill then set your boring bar to cut the desired radius to fit the torque tube diameter. If you can borrow a 17 turtle that would be
great to 'swipe' the critical dimensions. You will discover that depending on the 19t
turtle casting you use it is possible to run out of side wall....this happens rarely.
OR
If you have a 17t turtle to get the center line and other dims from send it
to me and I'll do it for the cost of shipping.
Charlie ny
 
Once again an outstanding offer from one of Fordbarn's finest members. Full kudos to Charlie.
 
I am getting ready to undertake this exact task. If anyone who reads this can provide the necessary dimension (center of gear shaft to center of arc, or the distance between bore OD's, if CTC is not available), I would greatly appreciate it! I have a handful of turtles, but no 17 to go by.
 
Brattons sells the 17 tooth gear (Moly. embedded Nylon), the V8 shafts (square hole for cable) and the V8 end shaft retaining caps. They do not sell the housing. If you check the diameter of a 19 gear Vs the 17 you can determine the additional depth of cut necessary to modify a 19 housing. I have the gear on order but has not arrived.
 
This type of thing is what makes the Ford barn so great! I am just going through the same thing and boom! Here is the solution!! Very cool...
 
I would suggest if you modify a turtle with another gear you file the 18 or what ever off and if possible stamp the 17 on the housing so the next guy knows what's going on. G.M.
 
I believe we found out several years ago that the 17 tooth nylon gear from Bratton's Model A Parts will work in an 18 tooth, #18, 11-39, turtle housing, normally used with 3.54 gears, with no modifications necessary to the #18 housing.
 
Bumping this thread with a question: Can an 18 tooth gear be used in a 19 housing without modification?
 
Terry said:
I want to use a 17 tooth turtle gear. As the gears have lower number of teeth the diameter of the gear get slightly smaller. I want to use a 19 tooth turtle housing and cut the arc into the turtle deeper so the new gear meshes with the drive shaft gear properly. Any suggestions as what tools to use to modify the turtle housing?
Click to expand...

Terry, what did you wind up doing to get a 17 tooth gear to work on your application/project?
 
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