Steel flywheel design issue

ICI · Post by **ICI** » December 13th, 2006, 7:24 pm

Hi to everyone.
I will be very appreciated about you opinion and advises about flywheel design.
The flywheel will belong to 2.0 16V Tipo engine - turbo converted with expected power of 320cv and torque may be somewhere 400 Nm.
The drive plate is cerametallic 5 pads 228mm with lightweight 3750g pressure plate made in Italy, no brand on them.
Here is some tryout of the flywheel profile - section.
The material is steel, according to B.S. appears as 530A40 or SAE 5140.
Is it good enough for this purpose?
I am concerned about the thickness in the friction face area.
Should I make it thicker because of the heat and bend loads of the pressure plate diaphragm spring?
Thanks in advance :)

Regards,
Iliyan

ICI · Post by **ICI** » December 14th, 2006, 11:39 am

Shame on me, but in the first drawing I didn't take the measurement of the above central bolt area diameter.This 90mm central surface changed the view a lot.Now it seems to be better?
I will look forward for you opinion.

Regards,
Iliyan

Post by **Guy Croft** » December 14th, 2006, 12:47 pm

Iliyan, hi

that looks OK to me.

The picture's a bit blurred but I figure it's maybe 8mm-10mm thick with radii in the right places?

BS970 Pt1 1983 530A40 (old En18D) is a 1% chrome manganese alloy steel, plenty strong enough and certainly stronger than the En8A I have used (with no problems) in the past.

Even the best spheroidal graphite cast iron, used for many production flywheels, only has a tensile strength of 420MPa, whereas even basic mild steel plate eg: En8 is about 600. Moreover steel has nearly twice the shear strength of cast iron in any form and is ductile so not prone to fracture - unlike CI ones which need to be kept fairly bulky to retain strength. It also has a higher Youngs Modulus so distorts less under high load.

Essentially you can make a steel fw half as thick as an equivalent lightened cast iron one and stil be plenty strong, and drill holes in it as well to reduce the weight on the outer periphery. make sure it's nicely radiused if you do that though.

It is important to tack weld the ring gear to the fw or better - put maybe 3 or four grubscrews in the joing between the ring gear and fw. The fw stops and starts in predominently two positions and on a light steel fw you don't want the gear climbing off.

Make sure it gets balanced with crank, and the clutch cover too. I'd always recommend clutch balance as well with a non-standard fw.

GC

ICI · Post by **ICI** » December 14th, 2006, 5:05 pm

Hi Guy,

and thank you very much for your advices and information.

Sorry about the previous picture visual quality .Here is drawing with better visibility.
The periphery will be milled off on three places between surfaces where pressure plate lays.
I will post 3D image, when is ready.

Regards,
Iliyan

Post by **Guy Croft** » December 15th, 2006, 6:45 am

OK, good picture now, don't forget radii in the four places shown.

GC

ICI · Post by **ICI** » December 15th, 2006, 1:53 pm

Hi Guy

Yes, there will be radii and smooth transitions between surfaces.
I have question about heat treatment procedures. Is there some need of heat treatment process before machining of the raw shape material and after, when flywheel is ready?

Regards,
Iliyan

Post by **Guy Croft** » December 15th, 2006, 1:58 pm

No, HT is definitely not needed, but make sure the friction face is ground not machined.

GC

ICI · Post by **ICI** » December 16th, 2006, 7:23 pm

Guy, hi

A friend of mine did this 3D modeling on SolidWorks, according to my drawing.
Here are few views of it.
We worked out the peripheral lightening also. Is it seems to be proper shaped?
The center holes will be drilled afterwards.
The weight calculated by SolidWorks is 4,370 kg.
Would you tell me what finishing quality, achieved by grounding(Ra or Rz) the friction face should be?

Regards,
Iliyan

pastaroni34 · Post by **pastaroni34** » December 19th, 2006, 4:49 am

very nice work! I am always happy to see people here with new machining projects.

I remember your first drawing had the lip over in the inside of the friction surface. I was going to recommend getting rid of that as machining would be quite difficult and you'd also be adding more stress risers to the part. Good for you!

As Guy said, this material should be more than strong enough for a flywheel. If I am correct this is an equivalent to a stainless steel? Personally I would not make a flywheel from stainless as heat flows very slowly in the material. This also means it holds alot of heat because of its dissipation characteristics. I don't quite know how much heat will be introduced into the part, I suppose this will depend on clutch choice etc..

If you need more details on the bolt pattern and such, I can provide. Its a pretty tricky pattern but good practise!

Also, for lightening, I would recommend holes rather than long slots. Holes are much much easier to machine, plus they will hold the hoop stresses of the ring gear better.

Post by **Guy Croft** » December 19th, 2006, 6:38 am

Hi Jason,

Some helpful observations as usual, thanks, but no it's not a 'stainless' steel, it's only around 1% chromium.
As for slots she'll be fine, see att. The hoop stress is very modest (too much and the gear will fracture in fitting) and the thicker outer periphery will support the gear no problem at all provided the gear is fixed as described earlier.

Regards,

GC

ICI · Post by **ICI** » December 19th, 2006, 12:21 pm

Thank you very much for your comments.

Guy, what is the real meaning the friction face to be grounded, instead of machined.
Is there a need of smoother face to avoid excessive wear of the clutch cerametallic puddles, or opposite - the friction face needs to be little bit rough with non concentric grounding marks, for proper bead in during break in period ?

pastaroni34 wrote:If you need more details on the bolt pattern and such, I can provide. Its a pretty tricky pattern but good practise!

Please, this will be very helpful.

Regards,
Iliyan

Post by **Guy Croft** » December 19th, 2006, 12:35 pm

The surface texture ('finish') should be 0.75 micro-meters Ra (30 CLA); that's a spec from AP Racing for example.
You won't get this with turning in a lathe, it needs to be ground on a grinding machine.

GC

pastaroni34 · Post by **pastaroni34** » December 19th, 2006, 6:14 pm

Ah, thanks for the correction about the material. I thought it was SAE 5140x series, when what we meant was AISI 5140. Sorry about the confusion.

As for the slots, I was only concerned by their length, whereas the slots on Guy's flywheel are 55 degrees each or so, yours are more like 80. Upon thinking about it some more, its not such a big deal especially since the ring gear will be tac welded onto the flywheel.

Guy, on steel flywheels do you do an interference fit in addition to the weld and/or screws? Also would it be okay to post the dimensions on here or is that a problem? Thanks!

ICI · Post by **ICI** » March 2nd, 2007, 9:56 pm

Here it is, the flywheel ready for build in.
The gear ring is tack welded. The crank, pressure plate and flywheel was precisely balanced with deviation of 0,004mm weight axis to geometric axis.
The weight is aprox. 5,700 kg

Post by **Guy Croft** » March 5th, 2007, 5:02 pm

MODEL POST!

Well done Iliyan!

Proposal - drawings - relevant questions - manufacture.

And all on view for others to learn from.

GC

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Steel flywheel design issue

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