Wheels and Weight Savings

[DannytheRadomski]

So I feel like wheels are a big source of weight. My first question is about mag alloy wheels. Does anyone use them? What are typical FSAE wheels made of? Lastly, why aren't there any carbon fiber wheels?

Wheels might currently be as light as they possibly can, but I was brainstorming this. My pipe dream car is adding up to be pretty heavy, so I'm thinking of ways to shave weight. Any help is appreciated.

[Owen Thomas]

This thread (http://fsae.com/eve/forums/a/tpc/f/125607348/m/84210891641/p/1) goes quite into detail about the benefits and drawbacks of CFRP rims/wheels. Some things you may not have considered are also brought up, which are of relevance to lightweighting anything in the wheel assembly. Most notably the fact that as something gets lighter it (usually) has less stiffness, and thus more compliance (bad news).

To answer your questions, it seems as though most FSAE rims are aluminum alloy, which does not exclude "mag" rims (significant magnesium content, but still an Al alloy). I believe ours are machined 7000 series aluminum centers with 6000 series aluminum barrels (from Jongebloed). Spin forged mag rims would be ultra sweet, but 10/13" rims aren't usually made in large production runs, so I would guess they could be tough to find.

I personally think there are more grams to be shed from the stuff your rims are attached to. As mentioned in the thread I linked, there are usually not significant gains from lightweighting a rim anyways.

[Drew Price]

BBS makes forged magnesium centers for some of their 13" wheel lines, they pop up for sale here and on eBay periodically.

They can also be bought new, but they are $$$$$

[kcapitano]

Keizer makes a nice set of magnesium centered rims that my team has been running for the past three years. They wont beat CF rim, but they are the lightest metal alloy rims I've come across. They are also a touch on the expensive side.

There are some teams with CF rims out there, but the only name that comes to mind is TU Graz.

If you're just interested in weight savings I find you can make the most gains at the conceptual stage. ie,

Why use 4 cylinders when you need only one?
Get rid of the turbo
find 8" rims
use a spool, manual shifter, hydraulic bicycle brakes, and other devices that many would consider absurd...

But before you do any of that, maybe you should put some more thought into your initial statement. I mean, figure out what is the single biggest source of weight for the car. Time spent there will be more rewarding than elsewhere.

[Peter7307]

"Lastly, why aren't there any carbon fiber wheels?"

One problem with c/f wheels is not the manufacturing aspects or even the costs but relates to the potential damage suffered when mounting and demounting tyres .

C/f wheels were built and tested by Michelin in the 1970's and the benefits simply did not warrant the costs at the time.
They were never a commercial proposition even for racing or limited volume production (aircraft wheels etc).

The idea still gets an outing from time to time and , usually , the same result as Michelin found way back when is also rediscovered.

Peter.

[jlangholzj]

SDSM&T ran a set last year. If i recall it took them a bit to get the formula right but i believe that they finally did...and they're pretty bitchin. Correct me if I'm wrong that tu-graz is running a CF one-piece wheel (or at least the whole thing is carbon?) SDSM&T has an alloy center with carbon rims (outers).

We have a set of the keizer mag centered rims and I think our last 70xx series wheels we made this last year were just as light?? I'd have to check that one to be sure

[PatClarke]

Danny,

Whilst I respect your enthusiasm, I think you should do some research before posting some of the stuff you do.

The vast majority of FSAE/FS cars use light alloy wheels of some kind and a very significant number use Carbon Fibre or CF/alloy hybrid wheels.

Most teams know and have been told time and time about the importance of reducing mass, unsprung mass and rotating mass. That's why so many teams use 10" wheels despite the constraints they put on design.

By the way, I agree with earlier statements about CF wheels.

Pat

[Jon Burford]

Nice to see a proper new thread!
Forged mag centers tend to save weight over plain alloy and are well versed in motorsport. A great company for 13 inch at least is MB racing, they are good value and good quality and have almost an infinite choice of rim sizes. He also offers cleaning, x-raying and re coating for a very reasonable cost.

Yes there are many different takes on the CF wheel. Many people do it. I think both the Graz car's have/have had complete carbon, I'm sure many others have had too.
for me I remember OBR having nice hybrid CF wheels this year, they actually used them too so I assume they work!!!!
With companies now popping up manufacturing CF rims for your own centers, (See a post on this forum), it's very tempting to just go out and buy some and save a load of weight on the rim, I won't claim to be an expert on Carbonic matters, so I will not try and say how good they are, or how long they will last or how many potholes they will take!

Since most wheels that you can buy are designed to be used on anything up to a road car I would say the way to make a lightweight FSAE wheel is to make a custom center from a lump of 7075-T6, and bolt it to some standard Ally rims (or Carbon ones if you have the money)
Then it comes to the Center-lock or multi stud question, what tires size and finally how to design a wheel center. I won't dig that up!

[jordan.k]

Originally posted by jlangholzj:
SDSM&T ran a set last year. If i recall it took them a bit to get the formula right but i believe that they finally did...and they're pretty bitchin. Correct me if I'm wrong that tu-graz is running a CF one-piece wheel (or at least the whole thing is carbon?) SDSM&T has an alloy center with carbon rims (outers).

SDSM&T ran CF outers with a 7075 wheel center and center-locking nut (+ Ti uprights). At SDSM&T it took 1.5 years to get the CF wheel shell design correct. The switch from Al to CF shells was a loss of 12lbs if I remember correctly (this is just the shells and does not include redesigned centers,centerlock and stubshaft). There is definitely more weight to be lost within the design and fasteners but everything was designed to be backwards compatible with the Keizer Al shells.

Kansas and UTA have been utilizing carbon wheel shells for many years, so they are definitely not new to FSAE. I believe that Akron has cast magnesium wheels and Michigan has 1 piece cast Aluminum wheels?

[Zac]

A couple years ago Akron U was running custom 1 piece mag wheels. They were really nice and a huge upgrade over the 3 piece wheels they had run previously.

I've seen quite a few teams screw up their wheel design/manufacturing though. I can remember one team running a pretty lightweight alloy rim that screwed up their wheel flange geometry to the point that they had to run a pretty thick bead of caulk to get the tire to seal. I also remember another team being forced to run inner-tubes with their carbon wheels.

[Markus]

Yes Akron runs a very neat 1 piece mag wheel.

We are also currently working on a 1 piece CF wheel.

[Bemo]

I can also remember Pat getting hit by a broken wheel http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

To be more serious. There are quite a lot of teams who made their own wheels during the last years. There were quite a lot of different concepts realized. I can remember one and multipiece CFRP rims, centers made of various materials bolted to CFRP or metal beds.

But there was quite a number of DNFs because of broken wheels, too. It's quite attractive to scrap of as much weight off the wheels as possible as it is unsprung, rotating mass far away from the center of gravity. Therefor it is no surprise that teams try to push it to the edge.
But even if the wheels don't brake there are example of unstiff rims resulting in extreme compliance making all suspension design obsolete.

I think Pat Clark already wrote an articel for Pat's Column about that topic some time ago. As I said, definitely an interesting topic.

[RAMR]

Hello everyone,

Just wanted to have an idea of how much it takes in average for a team to develop and produce a set of carbon fiber wheels (not with spokes or anything fancy, but using the simpler two-piece design). I've read in other posts that it takes years, but can it be done in a few months instead? Is a press required during the curing process? Thanks in advance.

[MCoach]

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