I am rebuilding the engine of my 1914 touring.
The crank shaft has been grounded with new babitt, the face of the flange of crank shaft has been machined as well as the two faces of the flange of the transmission shaft.
Alignment pins holes and flange circumferences have not been modified.
When the transmission shaft and fly wheel are bolted to the crankshaft, the shaft end is out of round for less than 0,001 which is not so bad.
But the circumference of the flywheel is out of round for 0,02 inche and lateral run out is 0,008 inche.
But the tripple gear pins are only out of round for 0,002 or 0,003 (I mean there are aligned on a circle which is not concentrical for 0,002 with the crankshaft).
Where the flywheel is the more out of round, there are two big holes in the flywheels for balancing I suppose.
Is it possible that the flywheel has left the factory so badly machined ? Can I use it after balancing with the crankshaft ?
Dial gauge is in mm
I'll stick my neck out and say It probably was
machined that way. They cared about volume. This is cause I machined my block for valve seat inserts. In doing this, your reference -0- is the
valve guide. I cleaned up the valve "chamber" bores
that could be measured with a yard stick. I polished
in there with a die grinder. No wonder they dont
breath good. They just didnt bother. Milling these
are a long "boring" operation. Mill boring heads do not like interupted cuts. Like 3 days worth cause my back cant stand, standing too long...
If Henry would have taken the time to build his T's like Swiss watches and Rolls Royce's he couldn't have gotten the cost down to market them to the 'common man' which was his goal.
Today when we restore our T's we try to build them with today's standards to make them more reliable which is better than Henry's.
Years ago when I started working on T engines and bodies I began to notice that tolerances weren't that close and finally realized that they came from the factory that way.
I love working on these cars and anything we can do to them to make them better is fine to build a better T to enjoy.
BUT a Model T is a T and a precision Rolls Royce is a Rolls Royce. We just have to keep everything in perspective.
It's a good idea to have the flange on the back of the crankshaft trued, as well as the main transmission shaft. Neither one is usually true.
You've done very well. Its a devils choice. If you change the position of the crankshaft, flywheel or transmission shaft to get less run out on the flywheel, you change run out somewhere else. I think you are in very good shape right now. If you dynamically balance the crank, flywheel and transmission shaft as a unit, you will be happy with the results. The fellow I use to balance has me mark each of the three in the position where there is the smallest run out on the transmission shaft. He first balances the crankshaft by itself within 2 grams, then attaches the flywheel and transmission shaft according to my marks and balances the entire assembly by removing stock from the flywheel. It makes quite a difference in the smoothness of and longevity of the engine.
When redoing my brother's engine, the trans main shaft was found to be out .009. Upon further inspection it was found that the dowel holes for the flywheel were non-concentric by .0045. As the crank is of stock dimensions and every other check for run-out came out good, I can only assume that it came that way from the factory.
The most likely reason for this is when setting the crank up between centers to finish the journals, the operator did not make sure the center were perfectly clean and dirt pushed the setup off-center.
The big question was, what do we do now? The solution will be to remachine the dowel hole 90 degrees from the originals in the open space between the clearance holes for the flywheel fasteners. To do this, the crank will be rechecked and machined if necessary to insure the OD of the crank flange runs concentric with the rear main journal. Once that is found good, a jig with the correct dowel hole location will be made to fit snugly over the crank flange and secure by the 4 flywheel cap screws. Next the crank will be clamped vertically to the edge of the milling machine table and the dowel holes machined using the jig to locate and guide the tooling.
Short of going to another crank, this was our best solution.
The point Philippe is worried about is the index for the starter ring gear on the outer circumference of the flywheel. It is well within acceptable tolerance for the starter to engage properly. No problem there.
I agree with Richard that all is well if the assembly is balanced.
The big question was, what do we do now? The solution will be to remachine the dowel hole 90 degrees from the originals in the open space between the clearance holes for the flywheel fasteners. To do this, the crank will be rechecked and machined if necessary to insure the OD of the crank flange runs concentric with the rear main journal. Once that is found good, a jig with the correct dowel hole location will be made to fit snugly over the crank flange and secure by the 4 flywheel cap screws. Next the crank will be clamped vertically to the edge of the milling machine table and the dowel holes machined using the jig to locate and guide the tooling."END QUOTE"
The Solution Would be rather then start butchering every thing from the crank flange back is to fix the center line of the crank, because that is where the problem lies.
The rear of the crank flange O.D. is what centers the crank in the flywheel. The dowel pins makes sure it returns to the same spot every time.
If you butcher the rear flange to center the flywheel dowel pins, then you have to butcher the O.D. of the flange to get it to fit in the I.D. of the Flywheel. If you do that, the Flywheel is off .004-50 for starter and ring gear. The tail shaft would also be out .004-50.
Some times the center hole is off, and that can be fixed in a lathe before grinding, but also many times the grinder man will line up on the front and rear main, and that will throw the center line way off.
Also if you butcher the rear, chances are the front crank gear will be out, for center, and gear mesh.
Then throw in a align bore that is not centered in the block up, and down.
What's that going to do for balance, Not Much Good!
I am not sure I follow your line of thinking. Your suggestion I believe is to grind the crank undersize. Grinding a perfectly good crank is not an option at this time as it will not fix anything if the existing dowel pins are not concentric to the crank flange OD.
By locating our work off the rear main, the crank centerline will be maintained along its length along with the concentricity of the flywheel to the crankshaft. As for locating the flywheel to the crank flange, the dowel pins along with properly torquing the flywheel cap screws will do just fine keeping everything in place should the flange end up not being a perfect slip fit.
Grinding a perfectly good crank is not an option at this time as it will not fix anything if the existing dowel pins are not concentric to the crank flange OD."END QUOTE"
Fact, your perfectly good crank is NOT a perfectly good crank, some body screwed it up, you don't have a center line, it is off .004-50 thousandths.
The flange will not go into the flywheel recess with out removing metal from the O.D. of the flange.
You are moving the flywheel off the true center line of the crank.
The best way is fix the center hole in a lathe, and move the O.D. of the flange that is .004-50 to one side, back .002-25 to get your true center line. you may have to take all off 3 to 4 thousandths at best.
That is better then butchering everything else.
The problem with locating the crank off the rear main is that because of the imbalance in a T engine, the third main does not wear concentric with the original center line. Consequently if the third main is the index, the new center line of the ground crank will not be centered with the OD of the flange and flywheel. Everything rearward of the third main will be out. Its been pretty well documented and discussed that you should grind a crank by reference to either the dowel pins or the OD of the flange. Steve Coniff, for one, wrote an article on this.
The crank shaft has been correctly grounded and the OD of the flange is perfectly centered and the transmission shaft since all the faces of the flanges have been trued is also correctly centered. The triple gears pins are also running in a concentric circle with the crank shaft. Only think out of round for 0,02 is the circumference of the flywheel; I have no problem with the starter gear since it is a 1913 engine. I suppose that all the holes in the flywheel including the housing (?) for the crankshaft flange have been machined together but separately from the OD of the fly wheel. I think it is better to leave like this or just machine the face of the housing (?) of the fly wheel where the flywheel is bolted to the shaft in order to eliminate the lateral run out of the fly wheel.
What I fear is that also the magnets will be out of round and I will have to balance the crank shaft and fly wheel with the magnets on.
What's to fear about balancing the flywheel and crankshaft with the magnets attached? You must do that. Not only the weight, but the dimensions of the magnets vary, so you cannot simply attach magnets to a balanced flywheel and expect the assembly to be balanced as well. While its true the magnets collect the metal dust from drilling balancing holes, its easy to clean up. When you drill holes in the flywheel, either drill in the circumference or the triple gear side on the outside edge. I see no pressing need to machine the flywheel so the circumference has zero run out. Balancing will suffice.
I agree with Richard and Royce. All should be well if the assembly is balanced.