Firstly, Ill talk about the material and method of manufacture.
Im planning on turning it from billet aluminium, 6061 T6, or perhaps, 2024 T3, I haven't decided yet.
The oem fly is approx 280mm in diameter o/a, and approx 24mm thick. This is turned/ramped down in the centre on the clutch face, inside the ground clutch 'circle' to approx 10mm thick to where its bolted to the crank With 6) m10x1.00 metric fine bolts. It weights a ton also, which is why I want rid, more on that later.
The ring gear mounts to its outer edge, closest to block and is approx 11mm wide.
For the clutch surface on the flywheel Im going to use one of Sweden's finest saw blades, the material properties seem to check out and its 4.5mm plate, Im going to spin it on the lathe and grind out the disc size I need, should work pretty great I reckon?
For fixing Im thinking of using maybe 16-20 screws, something of the 10.9 grade and in an m6, I looked at perhaps torq set for the simple fact of ease of removal and a pretty strong head.(No doubt another part of the engine will give out long before I have to replace plate!!) I had thought of heli-coiling the threaded portion in the flywheel to accept these countersunk screws as I feel the heli-coil tap cuts a more rounded cross-section thread profile, than a standard metric tap, leading to a lesser chance of stress risers. But I think Im getting over worried about this. I will have 3 times the diameter of the screws there to tap so Im well inside the limits. But Id like to hear peoples views on this, and wheather Id be better off forgetting about tapping, and just let them through and fit a nut to them at the rear? I have the room.
The same apply's to the pressure plate fixings, there is 6) m8 bolts holding it on in total and they sit pretty near the outer edge, from memory approx 10mm from fly edge to hole centre. There is also 3 location dowels in total equally spaced between the bolts 120 degrees from each other and on the same m8 bolt hole pcd. Will tapping these through be ok without further treatment? Threaded depth will be the full 24mm.
For ring gear security Ill shrink it on there and fix it in maybe 3 points with some allen head m6 bolts, counter-bored into both the ring gear and the flywheel to provide clamping force should things get loose. These drilling's may also break through 1/4 way into the ring gear material to provide a 'key' between the fly and ring.
The original flywheel is 10mm thick where it bolts to the nodular iron crank, Im going to bring this to 14mm on the alloy version, and ramp it out to the plate area in the nicest 'sweep' I can cut, and fit a 'flex ring' under bolt heads to prevent galling when torquing them up. This is the maxium thickness I can go here before I come out and touch clutch disc centre portion. The major stress that I see as being an issue is clutching it at max rpm, and the axial trust loading/unloading/deflection(if any) that may occur at that time.
As for all the other dimensions, they pretty much will be the same, can anyone see a problem with this? The rpm is pretty small, it will NEVER see over 8k, Limiter is 6.5k. I cant see a drastic down-shift happening to bring it over 8 at that.
Will I have issues with heat? Im thinking the alloy will conduct the heat from the steel plate pretty good and Im sitting the disc in there dry, I feel any form of chemical bonding would insulate things further.
Im guessing perhaps that it may see high temperatures on a hard launch or perhaps the odd hill start. This could possibly return the material to its pre heat treat condition? Perhaps not, its a hard one to calculate, but I dont hang around with the clutch.
Im also thinking the disc can be a clearance fit in there(outer only, inner 'step' will be machined away and it will be level there, ramp to crank bolt area starts here)
Does this fit sound ok?
Now for the reason Im fitting a lighter flyweel, real reasons why I need to,
Because of my cam profile, things only start to happen at 3.5k, the power band is fairly short, but a good one. I cannot spin the wheels too easy pulling away so any extra time I can get getting to my 'on cam point' will help.
Im also in favour of removing mass of the rotating assembly, as for 1kg I take off there, Ill be loosing 1kg off my sprung weight also, so its two fold, with the gains in favour of pulling weight of the rotating parts of course when it comes to 2nd and 3rd gear.
Im not too worried about how it will idle after, out of 14 cars one Idled perfectly, it was a straight 6 'German sedan' with a 5 in its name, which, strangely I sold after two months because it bored me a bit as it was too reliable.
As for hills, and lifting your foot and all that, that doesnt bother me either, and I know the effects.
Given the fact that its all going into a right hand drive car, and the gearbox on the left, flywheel entry to cabin wont or 'shouldnt' kill me, nor will it sticking itself in the road, nor will it if it exits bonnet, which it wont, as a dual mass 'just' has the inertia to do so. Considering this will be 4 times(approx) Lighter than a dual mass that then leaves exit through the front grille a possibility, but of course, there will be no-one infront of me, right ;!
Im confident Ill will be fine, I just need one of you guys to read the above, and tell me what you make of my thinkings.
I possibly could buy one, but Id prefer to make, as I seem to have a lot more time on my hands than I once had due to the 'current climate'. I dont really see it as not working or being an issue, do you?
Thanks as always in advance guys, if you see any issues with the above please do shout before I head out and start making a massive pile of swarf!
Ps, if it makes any odds, I still have my torsional damper bolted to the crank nose, and the engine is still running within its factory limiter rev band.