Flywheel fastener design, clamping force and dowel shear strength 2

[yoshimitsuspeed]

The 4AGE engine uses an 8 bolt crank and flywheel because it is the performance engine and in later years came supercharged.
The economy engines use a 6 bolt crank and flywheel. The 7AFE 6 bolt crank however is used as a stroker crank for performance builds.
Many people use 2, 3, or 6 dowels to try to make up for the 2 less bolts. It is my understanding that dowels should only be used to locate a part and ideally should see no significant force. It should be clamping force between the crank and flywheel that prevents one slipping on the other.
I recently designed a flywheel of my own and using the theory that clamping force was more important than shear force I used 6 6mm bolts in between the primary crank bolts. I would have loved to use a bigger bolt but this was the easiest solution that would clear the primary bolts. This gives slightly higher clamping force than the 8 bolt flywheel and should also give a slight improvement in rigidity and I would hope some added resistance to harmonic flexing.
I have had a surprising number of people in the automotive communities question this design. I'm not talking about home builders but people who build race engines and other aftermarket manufacturers who all say they use dowels and believe dowels are better. I believe this most likely is just because that's how it's always been done, not that it's actually better. Today one of my business partners told me pretty much the same thing and suggested I research why dowels would be better. I didn't find anything convincing in a short search. I did find a good discussion here on eng-tips on dowel shear strength and where most the posts seemed to agree that dowels should not be used for strength but other posts suggesting they could. Then I decided instead of researching general theory maybe I should just throw my design up here and get opinions on the design and theory as it applies specifically to this application.
This design uses 6 M6 SHCS counterbored to sit flush below the surface of the flywheel. The main flanged head cap screws come very close to the SHCS so this ensures they clear.
Question 1) Does anyone have any input or constructive criticism on this design in general?
Question 2) is there any way in which an 8mm or even 10mm dowel would be superior to this design?
Thanks

 

[gruntguru]

"BMW use conrods that have been snapped in two at the part line"

As do Ford - Greg!

je suis charlie

 

[tbuelna]

Sometimes anaerobic adhesive is applied to the mating faces of a shear joint that relies on clamped friction. The anaerobic adhesive provides a predictable/consistent static coefficient of friction at the clamped interface, which permits a reduced FoS to be used for the joint analysis.

 

[Hoxton]

I am sure that I saw a report via eng tips b the chief engineer of the Corvair engine, where they had early failures of the rivets holding the flywheel on. I remember the quote that after the investigation he said the guys making rivets did not know how to fasten rivets and neither did the riveters! I seem to remember that there were comments relevant to the above, perhaps I am mistaken, can anyone find it?

 

[Tmoose]

http://www.vv.corvair.org/Library/benzinger.htm

Maybe not so much the rivets themselves, but fatigue breakage of the portion of the flywheel that was bolted to the crank, but out at a larger diameter than the crank flange and bolts.

Factory construction 3 line reamed holes, and cold upset ~ 1/4 inch rivets in 12 holes out at pretty large radius.
But over time even those 12 snugly fitted fasteners were not up to the task of preventing micromotions, and then suffering wear and loosening.
Perhaps the slight slipping was part of the bending vibration reduction

http://www.corvairunderground.com/EDGERUNOUT.gif

here is a picture of the piece that bolts to the crank, and gets 2 hunks of iron riveted to it to form a flywheel.

http://www.corvair.ca/images/P7260035.JPG

Also note, the flywheel-to-crank joint with six 3/8"Ø bolts torqued to 45 lb-ft or so rarely gives any trouble, even when the vehicle is driven by a bone-headed 20 year old.