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Finite Element Analysis

Finite Element Analysis

Finite Element Analysis

(OP)
I've got a clutch assembly for a performance motorcycle. The goal is to reduce the mass but retain strength and durability. My question is if FEA is the best approach to determine the best compromise for the design of the assembly or if there's a different type of analysis that can answer the question of best design and material use.

RE: Finite Element Analysis

That's like asking, "Should I use a hammer to build a house?"  You need many tools, the first of which should be a good plan.

RE: Finite Element Analysis

(OP)
Thank you for the response. That's the answer I was looking for. I needed to confirm that I wasn't asking "should a house need walls?"

There is a high level plan. I just want to make sure I'm recruiting someone with the appropriate skills. I don't know much about FEA.

RE: Finite Element Analysis

Yeah, that's a tough one for an FEA outsider.  It would be best if you could find someone to consult with to flesh out job requirements. I recommend <http://www.impactengsol.com>

FEA skills are almost secondary next to good engineering skills.

RE: Finite Element Analysis

Motorcycle engineers have done a fantastic job with late-model sportbike engines.  I think you'll have a hard time making a better overall clutch package than the bike is equipped with from the factory.  What you lose in weight you'll probably also lose in feel/driveability and reliability.

This sounds like a FSAE question.

RE: Finite Element Analysis

You definitely want a guy with good thermo skills for clutch design.

RE: Finite Element Analysis

i reckon you need a guy with proven clutch design experience, it sounds like a very tricky piece of equipment.  but then someone like that may not be open to really innovative approaches, ie they'd know what works with today's technology.

RE: Finite Element Analysis

Philosophically, I would vote for specifically clutch design experience, rather than straight FEA experience.  It sounds like you need someone who started as a carpenter, but is currently a general contractor, to carry the house analogy a bit further.  

You definitely do no want someone who's never designed or worked on a clutch design before, as he will most likely wind up revisiting previously reject designs.

TTFN

FAQ731-376: Eng-Tips.com Forum Policies

RE: Finite Element Analysis

(OP)
These are all great responses and I really appreciate the input.
I'll look at the website that's been provided. This may help to get things organized.  
I agree that motorcycle engineering have done exceptional work in sportbike engines. Of course with OE products there are additional constraints such as costs which result in products/assemblies that require a great deal of compromise. This is strictly a racing designed product so yes, it does need durability but not to the extent of an OE product.  
I've been over to the FSAE board and will also to gather some information from there as well. All though it seems the boards activities has declined over the last year or so.
We already have a prototype that works but I'm sure someone could improve upon the product.  The focus is to make it as lite as possible while still retaining a good level of strength and durability. There are a lot of little parts that I'm sure can be improved, such as the clutch springs are very heavy and replacement titanium springs could be made with the same spring rate but less mass. Granted the durability would be reduced but if that's only after say 1k hours of use it would be more than acceptable.  Another example is the assemblies housing is aluminum. Perhaps an aluminum alloy / metal matrix or something along the lines of magnesium could reduce the mass and still retain the same level of strength. I'm sure there are more than a few improvements that can be made but accurate analysis work is needed.
Again, thank you for all of the responses.
 

RE: Finite Element Analysis

From an old structural guy - use the factory one - its proven...

And motorcycle clutches just don't weigh that much.  Advanced designs might only save ounces - not pounds - and still might blow.  Is it that critical??

RE: Finite Element Analysis

(OP)
TheTick - that second site contains liturature and event information. Yes, I would like to understand things in more detail but I'm relying on the "other person" to already have the knowledge / ecperience / expertise.

The budget for all of this is prioritized as material costs and manufacturing costs as the principal. The design and analysis is of course very sritical but budget wise it's a lower priority. It would be nice if I could find a freelance resource with clutch experience.

RE: Finite Element Analysis

(OP)
Mike, yes it's critical to reduce the mass. Every reduction in grams is an improvement. The so to say "best clutch" wins.

RE: Finite Element Analysis

Nafems.org has a list of experts.  If you need an expert to help evaluate potential hires, they could be a good resource.

RE: Finite Element Analysis

(OP)
The Tick - thanks again. I'm looking at the web site in more detail and found what you're talking about. I'll try them as well.
cheers

RE: Finite Element Analysis

Another Consideration:  How much more weight do you need to remove?  You can perform an absolute perfect FEA analysis and then have your part break because the load input estimation was wrong.  If you're trying to save 5% on material costs but you have a factor of safety of 2 on your load estimates then you might be better served getting better load estimates.  All it takes is one severe overload to break a part designed to its limit or ruin a fatigue life estimate.

RE: Finite Element Analysis

(OP)
BobM3 - That's a very good point. I hope alot of these scenarios can be fleshed out during the analysis. The load estimates will have a certain margin included in the calculations. The initial shock during launch and then the shock during each shift will all have to be considered. It would be great to discover all of this during the analysis phase but I suspect that one or two assemblies will suffer catastrophic failure. There isn't a set goal as far as the total mass reduction. It'll need to be determined if the reduction is cost effective. I don't want the final costs of the product to triple and only result in a very small increase to the performance aspect.

RE: Finite Element Analysis

kwklein,

   Let's really abuse that house analogy.  

  1. You have determined that you need a hammer to assemble your house, so you hire a hammer operator and point him at stuff that needs hammering.
  2. Your nails have been installed.  You have installed fence posts around the yard and you have persuaded the electrical inspector to pass your wiring.
  3. Now it is time to install windows, and you need the hammer operator off site.
   I hate analogies.  Operating a tool is a good job for a stupid person that you continuously supervise.  This does not sound like what you are after.

   The key to drastically improving performance of something, with a small increase in cost, is to re-design something that does not work properly.  People here seem to think that motorcycle clutches are well designed.  The bar could be sitting a little high.

   Another possibility is that you have a different set of working assumptions, and you can make different design compromises.  A drag racing cycle may only need the clutch to survive a half hour between replacements, for example.  

                          JHG

RE: Finite Element Analysis

All analogies fall apart when extended ad absurdum.

RE: Finite Element Analysis

(OP)
Drawoh – I'm not big on analogies either. Maybe that's why I seemed to lose sight in your analogy. You did summarize  what's being done. It's a redesign of the current already modified clutch assembly. I do admit that the OE clutch assemblies are well designed for their purpose and the parameters that are established for them.  A lot of additional compromise needs to be made with the proposed redesign. The assembly should have some durability and not require constant replacement but it doesn't need to live nearly as long, uninspected for thousands of miles, in any and all conditions. The design that's being tailored can be categorized as a top shelf performance modification. In the tiny area of no sponsorship motorcycle racing the clutch is a very important part of the complete formula and consumers will practically throw money at you for the so called "best one".

TheTick provided some good sites to get me pointed in the right direction. It's obvious that I'll need assistance to recruit the correct individual for my needs.

A jackhammer could be considered a hammer but that's not the experienced guy or tool that I want to use to construct a house.
 

RE: Finite Element Analysis

To do this properly and if you're keeping it at as a wet clutch you're getting into the tribology, slip-stick friction, heat generation, centrifugal stress...  See if anyone makes a proven replacement clutch.

Coming from a 5-year FSAE vet, there are much better avenues to pursue to improve your car.  The stock clutches on any late model 4-cyl are adequate and messing with the engine internals is almost guaranteed to cause engine failure.

RE: Finite Element Analysis

(OP)
Bribyk – The focus is more around the housing than anything. The actual clutch fibers and disks will remain as off the shelf items. We already have a new redesigned clutch assembly with only changes to the primary gear assembly (outer hub), hub clutch sleeve (inner hub), clutch cam set, and the clutch pressure disk. I understand that the OE clutch assembly is adequate but the focus is on the improvement. I think you may have missed my last post that explains the application a bit more.  

RE: Finite Element Analysis

My apologies I did miss that particular line in your previous post.  

Here's something to think about though, Suzuki superbike teams add rotating mass their engines (crankshaft) to improve the bike's drivability by providing a more predictable throttle response.  This shouldn't be as much of an issue on an FSAE car s you have added drivetrain components that a bike doesn't but making the clutch lighter is going to change its engagement characteristics.

As far as materials, if OEMs are using magnesium and such for engine covers, they've probably though about it for a clutch basket (potential fire issue maybe?).

RE: Finite Element Analysis

I would bet that current housings have been optimized, so you'd need a totally different material.  Unfortunately, there really aren't that many choices.  AlBeMet is one option, but it's expensive, and requires hazardous material handling.  Nonetheless, it would significantly lighten the housing.  Ti might be another choice.  The end result would likely be something that's maybe 20% lighter, but 2 times more expensive.

TTFN

FAQ731-376: Eng-Tips.com Forum Policies

RE: Finite Element Analysis

Bear in mind that the machining cost for parts like this often exceed the material costs (it certainly was when I used Ti) so the choice of material is not really a cost based decision. Beryllium alloys are banned by the FIA, at least for some series.

Cheers

Greg Locock

SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

RE: Finite Element Analysis

(OP)
Thank you all for the feedback. These are all good conversations and I appreciate the input. The application is strictly focused on drag and land speed racing which means smooth throttle response isn't necessary. It's always full throttle/wide open. I do understand magnesium is very much a fire hazard. I was only using that material as an example of the weight difference between the OE material and the final material. My thoughts are more along the lines of aluminum alloy, metal matrix, Inconel, or just using titanium. The machining costs aren't an issue but material bulk costs can be.
I'm sure we can agree that if the engineers who design the motors were given less constraints some parts may have been designed differently and / or alternate materials would be an option.  The hazmat materials may be an issue so I am trying to steer clear of Beryllium alloys but not because of FIA restrictions. They're not off the radar completely just not a primary option.
 

RE: Finite Element Analysis

I think you could design a lighter better part with FEA. The analysis will only be as good as the input data. Contrary to many beliefs, machined and heat treated E4340 can be lighter and stronger than many materials in high load or impact applications. One method is to use a CAD and FEA software that allow many "what if" iterations in a short time. Once you have explored these different designs then hand them to a FEA specialist to confirm the better design.

Several years ago we had to design a heavy duty low speed brake and found the number of design variables small and straight forward. Total torque transmitted is a function of pressure and coefficient of friction of the mating materials, removing the energy (heat) produced can be a challenge.
Rather than use several small springs you might consider a machined spring like these: http://www.taylordevices.com/machined-springs.html Combining the spring shape into the parts could provide a stiffer, stronger, yet lighter part.

Ed Danzer
www.danzcoinc.com
www.dehyds.com

RE: Finite Element Analysis

If you really know the loads then consider using an optimising FEA such as Optistruct (there are others).  

Cheers

Greg Locock

SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

RE: Finite Element Analysis


"The application is strictly focused on drag and land speed racing "

Those strike me as wildly disparate forms of racing, aside from needing big HP numbers.

If the stock part is bullet proof I'd spend the money on a suitcase full of carb jets and needles (or a laptop with cables and software for mapping), some dyno time (5800 ft altitude to simulate Bonneville's air density), and a heap of final drive sprockets, and tell my race buddies the clutch is machined from titanium billet with "chrome-moly" inserts to resist denting from the clutch disk tabs
 

RE: Finite Element Analysis

(OP)
Tmoose - I almost fell over in my chair with the Ti billet and chrome-moly comment. There are several areas that need improvements one being the clutch. There was a focus on intake/exhaust but the application level was to granular. The other thought was a quickshift  trans design but it's been done already and costs a bundle more. Anything to reduce parasitic losses is open territory. Cuurently I only have buy-in for the clutch assembly re-design.
btw, what's a carb? lol.  

RE: Finite Element Analysis

Orient  Express sells a NINJA 1400 "kit" ( contents unknown) for $543.
ttp://www.orientexpress.com/images//OERProducts/OER-2000-ZX10-SAC.jpg

Muzzy's is 630- $760 and includes a fuel shut off feature for smoother shifting.  http://www.muzzys.com/MZAS-K12/  Still need a compressed gas bottle, etc.

A 6 inch long 8 diameter hunk of garden variety 6061 could cost over $200 before the machine shop even turns on the coffee machine.
(McMaster CArr 1610T75 Multipurpose Aluminum (Alloy 6061) 8" Diameter, 6" Long - In stock at $232.09 Each )
 
 

RE: Finite Element Analysis

(OP)
Tmoose - yes 6061 is a common aloy used but normaly of the aged variety. We're leaning tward a 8090 alloy though.

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