Rear main thrust to block measurment

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Model T Ford Forum: Forum 2011: Rear main thrust to block measurment
Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Shirley on Sunday, December 18, 2011 - 02:46 pm:

What should the distance be between the rear main rear thrust surface and the block surface that the mag ring bolts to be? I come up with 2.009. The mag ring measures 1.450 from face of the coils to bolt face. Add .844 for the coil ring to outside of the crank flange, .020 for coil ring shims and then take off .305 for the crank flange. Dose this sound about right?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kohnke Rebabbitting on Sunday, December 18, 2011 - 03:50 pm:

Short answer, there isn't any. The Model T cranks center with about 1/8 inch difference between cranks. Herm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Shirley on Sunday, December 18, 2011 - 08:24 pm:

Before, when I've cut the faces Ive just guessed at a starting point. But, it sure would be easer if we could come up with an approximate measurement to cut the rear flange to and then just measure between the flanges and cut the inside thrust. I understand that Ford shops didn't need this measurement because they replaced the cap and shaft if nessary, but here in our world, where the coil rings have been trued, cranks flanges undersized, it sure would be nice to have that measurment so only two set up and are nessary. Thanks for any help, Bob


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kerry van Ekeren. (Australia) on Sunday, December 18, 2011 - 08:46 pm:

I have a 3rd cap I keep that I know is right, bolt it to the repoured one around a length of wood stock that has been centred in the lathe, turn each end to as close as I'm happy to work with then finish the last few thou with the tooling in the line borer (Gene French borer) or even just a touch on the squared linisher.


Top of pagePrevious messageNext messageBottom of page Link to this message  By joe bell on Sunday, December 18, 2011 - 09:01 pm:

I try to cut the thrust on the back of block till your just touching the block then measure inside your crank to find how wide it is, then cut the front of the rear main to that distance of the crank. If the block has been cut to make a full thrust like A's have then this is all worthless. I try to use the least amount of shims behind the field coil this way and it has worked for me. This way your crank can not go forward any more and you never have to worry about hitting the magnets when letting off the throttle. Every crank that has been ground will have a different measurement between the journal.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Sunday, December 18, 2011 - 09:47 pm:

I have always been curious about this and have a question.
What did the KRW gap gauge expect? If you understand how it works it clearly expected some standard place for the thrust surface otherwise it would not work as explained. But where and how was setting the thrust surfaces measured and faced???
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Bender Tulsa Oklahoma on Sunday, December 18, 2011 - 10:03 pm:

After the block has been lined bored, using a depth Mic you read the distance from the Babbitt thrust to the block and record that dimension.
All of the re-ground cranks will have a different width between the radius flanges and is measured with a snap gauge and recorded.
With the caps removed the crank is set in place and centered using a feeler gauge between the front and back of the block to the crankshaft flanges. Depends on the block but it runs from .010 or so, to what ever it is. Subtracting clearance (feeler gauge dimension) between the crank flange from the thickness of the Babbitt to the block gives me the amount to remove from the rear thrust surface plus .002 for clearance.
The front thrust is cut to the measurement of the crank, less .004. I cut the thrust surfaces on a mandrel in the lathe, which I found works best for the equipment I use.
That's how I skin the cat, your mileage may very.

Respectfully submitted
Mike


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kerry van Ekeren. (Australia) on Sunday, December 18, 2011 - 11:35 pm:

I like your set-up Mike, I run mine off a 18v cordless drill!!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Shirley on Monday, December 19, 2011 - 08:44 pm:

I know a framing square is not perfect, but this is what I came up with. The square is held in place with a bolt and lined up over two mag coils and the thrust. When set up on the block the final measurment from the thrust face to the coil ring mounting face on the block is 2.314 this accounts for coil ring shims of .040 and .035 magnet clearance. Both the crank flange and the coil ring have been cut on this motor.


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