Centering a Model A Crank, in a Block !

[Smitty]

Herm,
I have Kwikway fiktures like these; http://www.fordgarage.com/pages/kwboringbarfixtures.htm
Will they center a bar in the correct location?
Steve

[BRENT in 10-uh-C]

Originally Posted by Smitty

Brent, What/why would cause a crank be set off center?

Good question. I would think the most logical response would be 'machine operator error' however with that said, Ford's approved method back in the day was with the KR Wilson machine that used a boring plate that aligned against a bar that was inserted into the cam bores. Depending on the pressure placed against the false cam, in my mind it is feasible to see a few thou. variance each way off of centerline. The KRW set-up is not the most rigid set-up nor is the portable Kwik-Way unit however those units produced very nice engine bearings that went many miles, so maybe accuracy (-while desired) is not all that crucial.


Some food for thought in that while it is desirable to have the crankshaft in perfect alignment with the center-line of the cylinder case (block) however if a crankshaft is off by a few thou., does it not seem plausible that this was/is corrected when the flywheel housing was/is aligned and shimmed? By doing this, it allows the transmission and its' input shaft to be parallel in alignment with the crankshaft.

Originally Posted by Smitty

Herm had mentioned in another post that some shops do not know how to properly grind a Model A crankshaft. This could potentially put the crank off center leading to oil leaks and cam gear mesh issues?
Steve

Steve allow me to add to what Herm said above. In my opinion, ummmmm, Yes, - and No about putting the crank off-center. I will preface this by saying that I have only ground crankshafts on one type of machine, and I am sure Herm has way more experience with grinding cranks on multiple machines than what I do, ….however theoretically, the grind of the crankshaft would have nothing to do with the Cam gear to Crank gear backlash UNLESS the operator did not index or indicate the crankshaft into the chucks correctly. In this scenario, the front main journal would be ground non-concentric and the lash measurement would vary during rotation of the crankshaft. So he is correct in that regard and I will yield to his expertise over mine.


So that everyone else understands the process of crankshaft restoration/rebuilding/refurbishing, the crankshaft is usually soaked in a tank to rid the oils & grease followed by a hot jet wash. Some shops use an oven to bake the crankshaft to turn the oil into an ash in lieu of soaking. From the wash cabinet, I leave the crank gear on the snout and run it thru a rotoblast cabinet with shot about the size of pepper to clean it. Then the crank is crack-check with an electromagnetic machine. If it passes the crack check, I set the crank on a pair of Vee blocks and use an indicator on the center main to check for run-out. If there is run-out, it generally means the crankshaft is bent, and at that time it is straightened in a press. Once that is complete, the crankshaft is installed in the grinder. Mine uses centers to hold it. I use an indicator that measures in tenths that I indicate from the surface under the crank gear and on the rear flange. Once I have both ends running true, I have a Last Word indicator that I check the face of the flywheel mating flange with for run-out.


Where I believe the difficulty probably lies for many grinders is in the wheel. Ford specified an 1/8th radius on the cheeks of each journal pin. Since the majority of the cranks I do are Model-A, grinding my stone wheels to match this radius is not that big of a deal however for grinders that do multiple styles of cranks, they do not like the waste of material that comes with dressing their stone in this manner for Model-A cranks. The other issue that is difficult is that my grinder (-as is most others) are plunge grinders meaning we do not grind the journal in a lateral motion (like a typical metal lathe with a traversing carriage) but we come into the journal in a perpendicular motion and grind away material. Since my wheel is just over 1.250" wide, I must make 2 plunge cuts completing the first operation and then move out and over to the other side of the journal and repeat the process. Where this gets tricky is the tolerance across the entire 1.625 rod journal or 2.175 main journal width is 2½ ten thousandths of an inch! Not saying this is the right way, but the facts are that crankshaft grinding is about the least profitable operation in the shop, and there are likely shops that look for ways to trim the time necessary to do the job correctly as a way to cut costs.




Herm, that is a cool babbitt boring machine. It should be a great asset to someone wanting to pour their own rods inhouse. I have a Storm Vulcan #24 Rod Machine that uses a boring bar spun between centers that has 3 cutters on it plus the chamfering cutters on both ends. After set-up and after the poured rod is placed onto the mandrel, it actually cuts a poured rod to finished size in about 55 seconds from end to end. From there I cut the X grooves with the same cutter as you have.

[Kohnke Rebabbitting]

Originally Posted by Smitty

Herm,
I have Kwikway fiktures like these; http://www.fordgarage.com/pages/kwboringbarfixtures.htm
Will they center a bar in the correct location?
Steve

Mine didn't on some, you will just have to check yours ?


Herm.

[Kohnke Rebabbitting]

so maybe accuracy (-while desired) is not all that crucial. ' END QUOTE "


Then the job should also be 1/2 price !


Some food for thought in that while it is desirable to have the crankshaft in perfect alignment with the center-line of the cylinder case (block) however if a crankshaft is off by a few thou., does it not seem plausible that this was/is corrected when the flywheel housing was/is aligned and shimmed? By doing this, it allows the transmission and its' input shaft to be parallel in alignment with the crankshaft. " END QUOTE "


The only way you can grind a crank straight, is indicate off the time gear area, and O.D. of the flange. The gear should be pulled any way, as they will never match a new cam gear. Also when the mains are ground, then the rear flange should be trued, before the center is lost, or you can have some extra flywheel sticking off one side of the crank. That doesn't do much for Balance.


There is absolutely no way in this world that you can shim a flywheel housing to redirect the pilot shaft to a pilot bearing, where the crank is not centered. All that will happen is the Pilot will be on a bind all the time.


The only reason you shim the flywheel housing is to get the transmission bell at a right angle to the crank. You can't do that if the crank is not on center for any reason, and it sure doesn't do the rear main Babbitt any good, as it would be doomed from the start.


After set-up and after the poured rod is placed onto the mandrel, it actually cuts a poured rod to finished size in about 55 seconds from end to end. From there I cut the X grooves with the same cutter as you have. " END QUOTE "


All Grooves of any kind should be cut Before the finish cut.


I have a Vulcan machine, same as a Storm, as Storm bought them out, and made the same machine, only they put free standing belt shields on the ends. I sold a National, and an AMCO.


Herm.