Your clutch lining material will be Organic, Ceramic, Kevlar or Feramalloy.
Organic is the choice of most OEMs. Organic offers durability, smooth engagement and are gentle on matting surfaces. The downside is they do not like heat and require a fairly high clamping force to maintain grip as the co-efficient of friction is only around 0.32. Organic friction discs will almost always be a full face discs with the organic material made from phenolic resins, metallic powder or metal oxides and moulded or woven in construction.
The heavy duty options will have more metallic material in the mixture and also have a pressure plate of higher clamping value.
Kevlar like organic needs a fairly high clamping force due to it having a similar co-efficient of friction to organic. Its advantage is its ability to withstand heat. Often Kevlar is able to withstand 40-50% more heat than organics. Just like organic Kevlar offers smooth engagement and minimal wear of matting surfaces. This friction material will often last two to three times longer than the organic option. These are a good option for slightly modified vehicles and off road use.
Ceramic offers the highest co-efficient of friction of all the materials coming in at 0.48-0.55. This means that they can be used with a lower clamping force pressure plate and or high output applications. Ceramic clutches are known to wear mating surfaces heavily. This wear also makes them shudder on engagement. They can take more heat but slipping will cause heavy wear and result in a burnt up pressure plate and flywheel. The material is a mix of sintered bronze, ceramic material, copper, tin, iron, silicon dioxide and carbon. These are the competition clutches.
Feramalloy is a newer material and will possibly replace ceramic facings. It offers similar levels of wear and temperature resistance to ceramics. The advantage is it has a better static to dynamic ratio. What this means is smoother engagement and less shudder or chatter than ceramics.
I just have to add carbon carbon. In this setup both the friction material and the matting surfaces are amorphous carbon. This material grips more as it gets hotter and is extremely light. Cost of production is very high and these tend to be only a top level motorsport item. A good compromise is to use a carbon clutch disc, steel flywheel and pressure plate.
Single and twin plate clutch set ups is a story for another day.
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Clutch Pressure Plate Material
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(Materials)
(OP)
14 Jun 10 09:49Anyone know what materials are used for automotive clutch pressure plates? Are they mostly cast iron, or are some steel alloys used?
(Materials)
14 Jun 10 10:52Passenger cars, light trucks, and even larger trucks use gray cast iron for the clutch pressure plates. A typical alloy is a lamellar pearlitic gray iron like G11H20b according to SAE J431a. Here is an excerpt from SAE J431:
G11H20b (formerly G3500b)
Brake drums and clutch plates for heavy-duty service where high carbon and high hardness are both required to minimize heat checking and provide higher strength.
(Materials)
(OP)
14 Jun 10 11:40Yes, I was aware of SAE J431, which is why the words "cast iron" figured prominently in my question.
(Materials)
14 Jun 10 12:21Steve,
Sorry about that, I was just trying to be precise with the specific grade of gray cast iron typically used. I realize you are extremely knowledgeable on automotive materials, etc. It is my understanding that essentially all high volume automotive applications use cast iron pressure plates, but I am not completely familiar with what our competitors do.
(Materials)
(OP)
14 Jun 10 12:55Thanks.
I should have been more specific in my question,referenced the SAE spec and should have asked about other potential materials.
(Materials)
14 Jun 10 13:18Glad, that this thread has been resurrected. I wanted to add CG irons and also that in some military vehicles, I have seen alloy steel plates being used. Though gray iron was always considered as candidate material for this application.
(Materials)
(OP)
14 Jun 10 18:59Yes, Arunmrao, steel plate is where I seem to be heading, as my client (gratis) does not have the wherewithal for even a small production run of castings. Based on availability, 4140 and 1144 seem to be the main candidates. Another possibility might be some sort of flame spray coating on a 50ksi HSLA steel ring or even a T-1 ring.
(Materials)
14 Jun 10 19:46swall;
I think your idea of using T-1 material has merit.
(Aerospace)
16 Jun 10 01:20swall,
Is the clutch assy for an automatic or manual transmission? AT clutch plates are usually wrought steel, not cast iron.
Since clutches are usually sized based on heat loads, your particular pressure plate material selection will need to take into account the surface temperatures that the pressure plate will experience during operation. The material and heat treatment should have adequate margins for safe operation at those temps combined with any mechanical loads.
Before you select a material, I'd suggest a quick thermal analysis. Estimating the input heat loads at the friction interface is fairly straightforward. The more difficult part is the heat transfer rate away from that surface, through the pressure plate structure, and into whatever local atmosphere it's operating in.
Good luck.
Terry
(Materials)
(OP)
16 Jun 10 09:06Thanks, Terry. Application is manual transmission and this is basically a reverse engineering job. Original piece (which the OEM has discontinued)is a steel forging, and I plan to mimic it as much as possible using a part fab'ed from steel plate. As the production quantities will be small, my client does not have the deep pockets to procure forgings or castings.
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