Flywheel modification - would you be worried??

[MWP]

Hi all,

This is for my 5S-GTE build.

The 5S crank has a smaller PCD and M10 bolts compared to the 3S-GTE which has a larger PCD and M12 bolts.

I need to use a 3S flywheel, so i left it up to the engine builder to come up with a solution.
This is what they have done... install 8 dowels.







The dowels are VERY tight fitting, and the bolts are M10 which loosely fit the holes in the flywheel.

Itll be running a fairly harsh clutch (7 puck, 1200kg) and I want to be able to give it some abuse (ie, 2 step launches).

Should i be worried about this setup??
Cracking between the holes is my main worry.

[Youngy]

That is a good solution. Hot rod guys do it all the time since early Vs can now be encouraged to put out so much power above what the flywheels and how they were mounted originally were set up for.

I think (not sure) early Rotaries were modded in a similar manner.

Although I'd sleeve the holes for the bolts - I like overkill though

[AE112R]

I've seen people put dowel pins on the crank but never till such extend! Jeez 8 pins..
Refer on the 2nd photo, are you going to put 4 more bolts in the empty holes?

[Shakotan_Aaron]

could of also sold the flywheel and brought another, im sure you could of got one made with the correct PCD and hole bore sizes.

[allencr]

No, looks nice enough. Crankside nice & smooth & flat?
Use the higher ARP torque spec, not the factory's & their install recommendation to burnish/polish threads by torquing 3-4 times.

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Also, please give us a pic of the flywheel after it's been balanced. I'd like to see how well it was centered, guessing that even if it was spot on it would still have to have a bit metal drilled off.
Thanks

[Shakotan_Aaron]

No, looks nice enough. Crankside nice & smooth & flat?
Use the higher ARP torque spec, not the factory's & their install recommendation to burnish/polish threads by torquing 3-4 times.

are you sure about that? because your then streching and re-streching bolts that are only surposed to be used once.

i used a semi permanant locktight thread sealant on mine and toqued to arp specs.

[banana_socks]

If that's their recommendations then follow them. Also most bolts should only be at about 90% of their yield strength when fully torqued, so there's no real issue with using them again.

[thechuckster]

I would have been more comfortable with them either milling all or some of the dowels down to the surface of the crank face or milling the non-threaded section of the dowels down to a smaller OD before fitting into the crank so you required smaller holes into your mint flywheel.

Then again, you now have a larger surface area of contact between crank & fly (courtesy of the sides of the dowels) - without increasing the OD of the crank face. That has to be a good thing?

Biggest concern would be the bolts backing out and the flywheel free-rotating and smashing the dowels (which would then pivot and crack thro into the unoccupied bolt holes - munting both crank & fly).

[MWP]

are you sure about that? because your then streching and re-streching bolts that are only surposed to be used once.

ARP bolts are not normally tighten to yield, so they can be re-used if not overtightened and in good condition.
Watch: Special Presentation: How ARP Fasteners Are Made Video Series Part 1/3 V8TV - YouTube

Then again, you now have a larger surface area of contact between crank & fly (courtesy of the sides of the dowels) - without increasing the OD of the crank face. That has to be a good thing?
Biggest concern would be the bolts backing out and the flywheel free-rotating and smashing the dowels (which would then pivot and crack thro into the unoccupied bolt holes - munting both crank & fly).

All the bolt holes will have bolt in them... the above photo with only 4 bolts was just a test fitting.
The problem is that with all the bolts in, there is still room around those M10 bolts due to the flywheel holes being for M12 bolts.

So besides the clamping force, there is only 1-2mm of flywheel metal next to each dowel thats trying to stop the shearing forces.
That doesnt seem to be much :/

One option im considering is having steel dowles pressed into the M12 holes in the flywheel, then redrilling for the M10 bolts.
That should strengthen it up against shearing forces a decent amount.... i think.

[thechuckster]

I was just thinking about how it might fail when several bolts came undone - i fully expected you to use all 8 bolts to attach the flywheel.

Can you get bolts with larger shoulders (e.g. M12 shoulder with M10 thread)? I had expected you to be filling up the holes in the fly with the bolt - otherwise it would crack (as takai suggests in your build thread).

[Xauterus]

The bolt hole size is not a probelm due to the fitment of the dowels. The bolts are there solely to clamp the flywheel on. The dowels do the driving/ locating. Its good engineering principle to have the bolts with clearance.

A very good solution.

[MWP]

The factory Toyota 5S flywheel bolts i believe are M10 with 12mm shoulders.
The problem here though is the 5S has a smaller PCD. So to fit those i would need to slot the bolt holes ~1mm towards the center.
So i would end up with even less flywheel metal, and still have a gap on the outside of the bolt holes.

[codez]

i think either sleeves in the flywheel or custom made bolts to the correct length with M10 thread and M12 shoulder as thechuckster suggested

[Xauterus]

Get over the fact there is clearance around the bolt holes. Bolts are not designed to drive things. They sould only be used for clamping. Look at a race cars quick release wheel. It drives on pins and then just has one nut holding the wheel on.

[thechuckster]

codez: after reading MWPs reply I now realise that the bolt holes are not centred on the flywheel thru-hole (i thought his workshop had doweled the misaligned holes and drilled new holes for the flywheel). I think he'd need a pretty funky/unique bolt (M10 thread, M11 shoulder, M20? head-face to suit M17 socket).


no idea if sensible, but how about wide washers under the bolts? e.g. thick washers as found/used by head bolts et al. With a 10mm ID and 3-4mm wider than the existing ARP bolt?

Or are washers not a good way to spread out a clamping force like is need here?