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+--- Thread: Flexplate to be used behind custom flywheel - problem with fretting? (/showthread.php?tid=5918)
Flexplate to be used behind custom flywheel - problem with fretting? - fcp - 10-13-2014
I'm putting this in a new thread as it might be an interesting discussion in general for people around mounting of flywheels, though the question relates specifically to the GS6-53DZ tramsmission project I'm working on here http://www.superturbodiesel.com/std/Thread-GS6-53-ZF-Gearbox-OM606-Adapter
So the question relates to my decision to use the MB flexplate (usually found in auto trans setup) to provide the starter ring clamped in between the crank mounting flange and the new custom flywheel I've been working on.
![[Image: 9895741904_08f5808f93_b.jpg]](http://farm4.staticflickr.com/3737/9895741904_08f5808f93_b.jpg)
Using the flexplate in this way was essential because the design of the flywheel (which needs to project a long way past the face of the crankcase to account for 1. the adapter plate depth and 2. the unusual recessed drive shaft on the BMW gearbox) required it.
My plan was the locate the flywheel on the centre flange, using the dowel to locate and then clamp them with 12.9 capscrews (and then balance the entire assembly).
Talking to an experienced engineer this morning though, he expressed concern that this arrangement might not be satisfactory and that there could be movement (fretting) of the flywheel vs flexplate vs crank.
I see his logic. If the flywheel was bolted directly to the crank then fine, but the flexplate is two pieces of sprung steel and it might be sufficient to prevent enough clamping force to resist rotational sheer.
What does anyone here think? Fabricating a 1 piece flywheel to include the starter ring will be very difficult so this arrangement is preferable!
RE: Flexplate to be used behind custom flywheel - problem with fretting? - Graminal95 - 10-17-2014
I'm not sure I fully understand. If you torque the bolts to MB spec. then the clamping force will be the same with the sandwiched flex plate and without. The only thing that may change is the flatness/parallelism of the flex plate which may cause the fw to wobble and the coefficient of friction between the parts. If there is concern why not bead blast all contacting surfaces and check the runout of the fw once installed. If it's within spec. You should be good to go. If not you may have to grind the center of the flex plate or take out the center of the flex plate and just weld it to the back of your fw.
But maybe I'm missing something.
RE: Flexplate to be used behind custom flywheel - problem with fretting? - Simpler=Better - 10-17-2014
(10-17-2014, 07:34 AM)Graminal95 I'm not sure I fully understand. If you torque the bolts to MB spec. then the clamping force will be the same with the sandwiched flex plate and without. The only thing that may change is the flatness/parallelism of the flex plate which may cause the fw to wobble and the coefficient of friction between the parts. If there is concern why not bead blast all contacting surfaces and check the runout of the fw once installed. If it's within spec. You should be good to go. If not you may have to grind the center of the flex plate or take out the center of the flex plate and just weld it to the back of your fw.
But maybe I'm missing something.
You should be fine, if you're worried run red loctite and safety wire.
The stock 617s went FW->flex->spacer and I've never heard of one coming loose.