development time for carbon wheels

[Diablo_niterider]

hello ,

I am building a team for 2010 and would like to know from teams with experiences with carbon fibre wheels and driveshafts ,the no. of people they had developing the wheel and the overall development time they spent on it , no one in our team or university has any knowlegde on it,
so they will be starting from scratch.

we have people who are studying but i need to now its feasibility with four people working on it.

my plan is to let them get experience by making floor panels ,bodywork for this year to get used to working with it and then move on to developing the wheel , so will 8 months of development and 3 months of testing be good enough to have a fairly good wheel.

do also mention development time for your driveshafts.

Any Help would be greatly appreciated.

regards

[Diablo_niterider]

hello ,

I am building a team for 2010 and would like to know from teams with experiences with carbon fibre wheels and driveshafts ,the no. of people they had developing the wheel and the overall development time they spent on it , no one in our team or university has any knowlegde on it,
so they will be starting from scratch.

we have people who are studying but i need to now its feasibility with four people working on it.

my plan is to let them get experience by making floor panels ,bodywork for this year to get used to working with it and then move on to developing the wheel , so will 8 months of development and 3 months of testing be good enough to have a fairly good wheel.

do also mention development time for your driveshafts.

Any Help would be greatly appreciated.

regards

[PSUAlum06]

Carbon fiber rims are a lot of time, money, and trouble for something of marginal performance benefit. I'd worry more about how to build a car that easily makes it through tech inspection and completes all the dynamic events than trying to shave another 15 pounds off the car.

Trick parts are great, but you really don't need them in order to be competitive. A well tuned car goes a lot further in my opinion.

I'm also a little weary of student designed or fabricated wheels in general. There's a lot you can easily mess up with rim geometry. You can make your wheel as light as you want but when they don't seat the tire you won't win anything.

[Wesley]

Say what you will about lightness, but I did see TUGraz switching to their aluminum shells for the autocross and endurance event.

Lots of teams are having stiffness issues with them. Though compared to our Keizers, I doubt there is much difference.

[Tech Guy]

If a team switches wheels, e.g. from carbon to aluminum, at any time after tech inspection OR their first event, whichever comes first, they are breaking the Rules and should be called on it. The only exception is when going to rain tires.

[Mike Macie]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Wesley:
Say what you will about lightness, but I did see TUGraz switching to their aluminum shells for the autocross and endurance event.

Lots of teams are having stiffness issues with them. Though compared to our Keizers, I doubt there is much difference. </div></BLOCKQUOTE>

TUGraz was using the carbon wheels during endurance. I saw them with the other wheels on too but i think it was just for moving around the paddock.

[Big Bird]

Our team has had carbon fibre rims for two years now, and I would say that the development time was around 4 years. For driveshafts, over 6 years (still investigating). Justification as follows:
2003 - first experience with CF - bodywork on spaceframe car
2004 - first structural CF - front chassis of vehicle (rear spaceframe)
2005 - complete CF chassis (to rear bulkhead)
2006 - CF wheel outers and a-arms.

I couldn't isolate the wheel development 12 months, since the lessons learnt in the previous 3 years work had all contributed to the necessary team knowledge required to complete the wheel project. This is in a uni with a strong composites background, specialist composites labs, specialist composites technicians, autoclave, etc etc.

Effectively the rims can save around 0g-1000g on your wheel package (depending on what you are replacing and your manufacturing expertise). In our situation we have some justification, as we have put the processes in place to regularly complete this project, and are now primarily refining a working package. The design problem that we have aimed to solve is reduction in unsprung mass to address specific handling problems.

With due respect, in Orion Racing's case I would say your design problem is not reduction in unsprung mass. The design problem you face is successful completion of the project, and this requires specific set of skills that takes precedence over any fancy finishing touches. (Most prominently, it requires a decision making process that limits risk, and usually this means being wise enough to choose paths that use up less of your time, people and money). There are plenty of products on the market that address the functional requirement of "wheel", so use them and move on.

There is nothing smart about spending 4 years developing a product that replaces something you can buy off the shelf. Know your design problem, and don't go complicating it by trying to solve other peoples problems as well.

Carbon fibre ain't god. It is an engineering material. Having carbon fibre no more makes you a great engineer as having a tin of North Sea anchovies makes you a great chef.

Cheers,

[Grant Mahler]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Tech Guy:
If a team switches wheels, e.g. from carbon to aluminum, at any time after tech inspection OR their first event, whichever comes first, they are breaking the Rules and should be called on it. The only exception is when going to rain tires. </div></BLOCKQUOTE>

Except that Tires are included in the wear items category and teams have (previously) made the argument that the tires are kaput after one event. Different tires of the same compound (Goodyear drys for example) are allowed to be mounted on different rims as long as all of them are present at tech inspection.

Or so goes my understanding...

[Wesley]

Yes, they were told of this and had to switch back to the carbon wheels.

Or am I misunderstanding? Maybe someone from Graz could give some input, since I don't want to accuse without all the info.

[Diablo_niterider]

@ bigbird -
i completely agree with you , that we guys have tech inspection and competing in the dynamics is a prority and i would not like to give an excuses for that.
this year we cleared all the needful to run dynamics but had i would say a bit of bad luck (we burnt our clutch ) or we would surely completed all dynamics.
i have been here for 2 years (and have dropped 2 years that means i am gonna do this for the next 2 years too.)and have now finaly been able to set up almost all the required equipment (we are building our own dyno and also trying to get the univ. to buy it for us)and team to make a decent fast car. so watchout for us in the coming years http://fsae.com/groupee_common/emoticons/icon_wink.gif

i did my research on teams using carbon fibre in different ways and i calculated the places we can loose weigth ROUGHLY by using just carbon fibre bodywork and firewall and floor panels etc.. and a weigth reduction on certain parts , we would save approx. 35 kg just roughly. and as of our calculations we will loose 85 kgs in all.

i would like more input from you guys on
1.cf a-arms
2.cf-uprigths
3.cf- airbox
4.cf-steering wheel

we will take these steps gradually for sure. .
wheels and driveshafts are a little far fetched rigth now. but we have to start .

[Diablo_niterider]

and by the way besides tu graz

tu stuttgart
elephant racing

ran on cf wheels during endurance.

does anyone know what times tugraz was clocking during endurance .

[blister]

Weight savings are not only achieved with carbon fiber only.

There are other concepts, like running smaller engines or/and tires.

Look also at the cars from stralsund or helsinki. Both very fast cars with big engines and big wheels but not too much carbon fiber used.

I would start with simpler parts. Maybe the Steering Wheel?

[PSUAlum06]

Carbon fiber bodywork and a steering wheel are probably a good place to start, and A-arms would be a good second step. Wheels and uprights might be more trouble then they're worth. Just be warned, carbon fiber isn't a cure-all material.

The other thing to keep in mind is that low weight is secondary to just having a well setup car with good handling. I know of one 250 kg car for example that will beat about 85% of the field at any comp.

[flavorPacket]

There is no need to do carbon anything in FSAE. Look at wisconsin and stuttgart.

Michigan weighed in at 397 (180 kg) with a turbo F4i, 2 huge radiators, and dry sump with no carbon components aside from the steering wheel, seat, and bodywork. You can do the same.

And to my knowledge nobody has done a carbon upright, though I'm sure many F1 teams are trying.

[blister]

I must say, that just looking at numbers like weight, stiffness or inertias, carbon fiber rims can definitely improve the lap time. We are developing cfrp rims with 5 spokes. The guys spent nearly 9 months till now. At the moment we have negative forms. Maybe we can show a presentation model at FS Italy. We had support from two small companies (one is kringlan.ch, which is pretty interesting in terms of manufacturing processes) for the engineering and can use an autoclave at our university which is a great help anyway!.

It`s definetely more critical than a monocoque...

And Clenn: It`s only 5 kilometres to swim to the swiss border from Immenstaad. We should arrange something next year! Did you also make your really, really fantastic monocoque there?

[JR @ CFS]

Chalmers has been working on theirs since 2003, getting progressively lighter and stiffer, but still suffering flexing problems. I seem to remember that Pats Corner on www.formulastudent.de (http://www.formulastudent.de) has a piece about flexing wheels.

[J.R.]

Darmstadt,

Did you have any problem with loss of tyre pressure due to the way you mounted the valve? Carol Smith warns against mounting the valve pointing directly to the center of the wheel, stating that the centripetal force will open the valve during operation, and I was wondering how this actually plays out a FS velocities?

Car looks great, glad to see you got to use the rims at Hockenheim!

[PSUAlum06]

the other issue I've heard of with student designed or fabricated wheels is out of spec rim flanges. You don't have to be too far outside of the ETRTO or TR&A guidelines to be at the point where it either takes 90 psi to get your tires to seat or your tires just don't stay attached to the wheel.

[exFSAE]

CF wheels.. sketchy at best.

[murpia]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by J.R.:
Darmstadt,

Did you have any problem with loss of tyre pressure due to the way you mounted the valve? Carol Smith warns against mounting the valve pointing directly to the center of the wheel, stating that the centripetal force will open the valve during operation, and I was wondering how this actually plays out a FS velocities? </div></BLOCKQUOTE>
This is one of the reasons to always fit a valve cap. The good ones are o-ring sealed.

Regards, Ian

[RacingManiac]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by PSUAlum06:
the other issue I've heard of with student designed or fabricated wheels is out of spec rim flanges. You don't have to be too far outside of the ETRTO or TR&A guidelines to be at the point where it either takes 90 psi to get your tires to seat or your tires just don't stay attached to the wheel. </div></BLOCKQUOTE>

Or you can get Kodiaks and they'll take 120psi to seat....fun time to be had by all concerned....

Joannum(sp?)Graz also sport the identical Carbon wheels that TU Graz uses, which leads to to wonder if such items are available commercially...I had a poke around with TU Fast Munich's carbon wheel in 2006, they are ridiculously light and seems very well made. IMO if your team is on a diet and everything else was as light as you can get it this will be worth investigating since each carbon wheel weighs 1-2lb, where as a conventional 13 inch CNC 3 piece will be in 7-8lb minimum commercially, so in effect 1 CNC wheel = 4 carbon ones...

[TMichaels]

I heard directly from team members of cf-rim-teams that they switched back to aluminium as the lack of stiffness totally destroyed their setups including teams running cf-rims at FSG.

[DART-CG]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by murpia:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by J.R.:
Darmstadt,

Did you have any problem with loss of tyre pressure due to the way you mounted the valve? Carol Smith warns against mounting the valve pointing directly to the center of the wheel, stating that the centripetal force will open the valve during operation, and I was wondering how this actually plays out a FS velocities? </div></BLOCKQUOTE>
This is one of the reasons to always fit a valve cap. The good ones are o-ring sealed.

Regards, Ian </div></BLOCKQUOTE>

We never had any problems with the valve, but with the loss of tire pressure, yes.
But that was a housemade problem because we use a sandwich bed to increase stiffness with very thin layers. But we solved it, (hours of work that ended in the night before Saturday at FSG). It wouldn't have been that big to drive with the pressure loss, it was only 0.1 bars/h.

Concerning the flanges we have a special solution. Our tire "jumps" at sometimes 5-6 bars ans would easily destroy the flanges. Thats why we bolt the rim during tire mounting with an ultra-stiff 10mm thick cfrp corset to bear those huge "jump-forces". Then we remove it again.

As I said, lateral stiffness is the key to a good cfrp-rim. You can design a light rim with a good durability but the hard thing is to increase stiffness.
This needs extensive prototype testing. We developed a prototype, tested it on the Fraunhofer Institute concerning stiffness and durability (and to verify the anisotropic ansys model) and then optimized the lay up for the next protoype.
You could also indentify the critical areas and overdimension them. With this method you can still manage very light rims with ~2kg.

Look at Stuttgart, they managed incredible times with their cfrp-rim. Our car was also able to clock the fastest time in autoX on the cfrp rims (except one cone http://fsae.com/groupee_common/emoticons/icon_frown.gif )

[oz_olly]

One thing I am curious about is how you mount and dismount tyres from carbon fibre rims. At the moment we have our own tyre machine and use 3 piece aluminium wheels. When we mount the wheel on the machine the four feet that slide out radially to lock the wheel in place damage the wheels. The face of the feet that grips the inside of the wheel have a very course pointed knurl type of pattern. The only real thing I can think of for CF wheel would be to mount rubber to the feet or something similar.

Cheers

Olly

[smb96]

We do it like you said. We mount plastic covers to the feet. You need to use a maschine which is in very good condition. Somtimes on older maschines the arm scratchs the rim. That would be a problem for the carbon wheel.

[murpia]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by smb96:
Sometimes on older machines the arm scratches the rim. That would be a problem for the carbon wheel. </div></BLOCKQUOTE>
That sounds like a problem for any material, not just carbon...

Either tyre fitting damage is accounted for in the safety factors of the rim design, or it isn't. If it is, it adds weight, whatever the material involved.

Regards, Ian

[J.R.]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by murpia:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by smb96:
Sometimes on older machines the arm scratches the rim. That would be a problem for the carbon wheel. </div></BLOCKQUOTE>
That sounds like a problem for any material, not just carbon...

Either tyre fitting damage is accounted for in the safety factors of the rim design, or it isn't. If it is, it adds weight, whatever the material involved.

Regards, Ian </div></BLOCKQUOTE>

I'm no expert with carbon, but after working with the Darmstadt team I got the impression that carbon is a whole lot more sensitive to scratches than Aluminum.... We had new tyres mounted yesterday by a sponsor, and they managed to damage our Kiezers, so I can't imaging having anyone other than the team mount tyres on the carbon rims.

[DART-CG]

If you want to realize very thin rim flanges the main problem beneath scratching the rim is bending due to the mounting arm. Consider that in a design. We measured these forces with strain gauges, they can become quite high depending on the mounting machine you use.

[Fred G]

These machines you talk of, are they pneumatic?

If so, most, if not all are regulated by a regulator. Reduce the regulating pressure enough that the clamps only begin to work - this will reduce clamping force.

Clamp your wheel.

Then increase the pressure to perform the tyre mounting.

Fred