Wheel Center Finishing

[Big Mo]

I've heard a lot about Type II and Type III anodizing methods hurting fatigue life substantially, so anodizing our wheel centers like we did last year has gone out the window.

Instead, I am looking to paint them. I remember reading that Carroll Smith preferred brittle paint like Krylon that would show cracks rather than hide them. But a google search for any other product that might be considered "wheel paint" leads me to cosmetic paint that is "chip and crack resistant", obviously what we don't want.

Anybody have a preferred paint/coating for wheel centers, or aluminum parts in general?

[Big Mo]

I've heard a lot about Type II and Type III anodizing methods hurting fatigue life substantially, so anodizing our wheel centers like we did last year has gone out the window.

Instead, I am looking to paint them. I remember reading that Carroll Smith preferred brittle paint like Krylon that would show cracks rather than hide them. But a google search for any other product that might be considered "wheel paint" leads me to cosmetic paint that is "chip and crack resistant", obviously what we don't want.

Anybody have a preferred paint/coating for wheel centers, or aluminum parts in general?

[Dsenechal]

We will polishing the machined surface this year, and leaving them bare. Polihsing will give them the smoothest finish, therefore being optimum for fatigue and the sort. I have been told in design classes that the machine marks can lead to crack propagation, but if the wheels are properly designed, that should not be a huge concern. our 2010 wheels kept the finish right off the Mill.

[billywight]

Look into Chem-Film coatings. Protects against mild corrosive environments while giving a gold color and no material build up or hardness increase.

Have a look at MIL-C-5541E CLASS 1A specs.

[exFSAE]

I've never seen a fsae wheel fatigue or crack.

Electroless nickel plating is a great look for aluminum.

[Dsenechal]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by exFSAE:
I've never seen a fsae wheel fatigue or crack.

Electroless nickel plating is a great look for aluminum. </div></BLOCKQUOTE>

Haha havent seen one fatigue or crack yet! Parts are getting tinnier and tinnier these days

[MegaDeath]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by exFSAE:
I've never seen a fsae wheel fatigue or crack. </div></BLOCKQUOTE>

At Michigan in 2009 there was a team that DNF'ed endurance because they cracked one of their wheels. I can't remember what school it was, but I remember that it was a 3-piece Keizer 4-spoke wheel.

[Big Mo]

I have a feeling if we all magnaflux'd last year's wheels we'd find something at the spoke bases...its the stuff you can't see that gets you.

Thanks to Bill Wright for pointing me in the right direction. Do you know how common the Alodine/Iridite treatment is? Will the average ano shop be able to do this?

[PatClarke]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">I've never seen a fsae wheel fatigue or crack. </div></BLOCKQUOTE>

In 2008 at FSG I was hit by a loose wheel wheel. The centre had fatigued and failed.
I swear I could hear the driver sing "You picked a fine time to leave me Loose Wheel" =]

There have been several wheel failures at events I have attended. Usually, the cause is poor design or using tapered wheel nuts on alloy wheels.

Pat

[Big Mo]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by PatClarke:
using tapered wheel nuts on alloy wheels. </div></BLOCKQUOTE>

If you don't mind me asking, Pat, why is this? Steve Fox mentioned it when he presented his seminar to us, but it was one of the few things that confused us. Are not tapered nuts needed to center the wheel? Are you referring to a centerlock wheel nut, or a pattern of nuts?

[Drew Price]

A tapered lug nut seating straight on the aluminum can gall up the conical receiving surface, and in addition to clamping the wheel to the hub face, the conical nut 'spreads' the material, which is often very thin, and cracks may start there since you're pre-stressing the material around the nut by the act of tightening.

The wheels should be centered via a receiving bore on the hub - take a look at just about any OEM road car wheel-hub interface. This kind of centering in the aftermarket is called 'hub-centric.'

You should have some kind of insert to receive the nut rather than the nut seating on an aluminum hub. Our BBS wheels came with steel tapered inserts that sat in straight-bored holes in the center, so the 'wedging' was taken by the steel insert, which then did the 'clamping' of the wheel to the hub.

That is my understanding at least, particularly with how thin some teams are making their wheel centers.

A lot of race wheels I have seen use locating dowels in addition to lub bolts/nuts to locate the wheel and for torque transfer, like you see on a wheel with a centrelock hub.

See these photos:

h t t p://www.applemotors.com/images/inserts.jpg

I have also seen nuts like this, that have a piloted section that could do some of the locating, and a flat seat that clamps the wheel, tolerancing would be tricky though, you don't want a close fit and risk galling up the interface either.

h t t p://images.esellerpro.com/2133/I/292/0/lrgscalerannge%20rover%20sport%20wheel%20nut.jpg



Drew

[Drew Price]

Wrote a post, but apparently I used too many 'trigger words,' so it has to be moderated.

My answer has to do with fatigue around the conical seat cut directly into an aluminum center. You remove more material than should be removed around the nut seat if that's the only place that you've got retention of the wheel, and cracks will start there, especially if the steel nut galls up the aluminum seating surface.

Drew

[PatClarke]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Are not tapered nuts needed to center the wheel? Are you referring to a centerlock wheel nut, or a pattern of nuts? </div></BLOCKQUOTE>

Nope, I am talking about ordinary wheelnuts.

Firstly, all wheels shoyld be spigoted to the hub. This centres the wheel (not the nuts) and also carries the weight of the vehicle. The nuts simply hold the wheel on.

Tapered nuts on steel wheels or alloy wheels with steel inserts help with locking the nut at reasonable tension by increasing the bearing area. Excessive tension may cause hub and brake distortion.

Tapered wheel nuts on aluminium wheels slowly but surely bury themselves in the wheel. The this can cause stress concentrations and can generate cracks that can eventually cause the wheels to fail.

On the FSG website in one of the Pat's Corner columns, my "Design Error of the Month" shows a typical failure. I warned the team they were flirting with danger with their design (tapered wheelnuts in close proximity to wheel slots) and after the event they came to tell me how wrong I was, that their wheels stood up fine. A month or two later I got an email from their Faculty Advisor with a picture of a wheel that failed in testing after the competition.

I would post a link but that will cause delays. You all know where to finf 'Pats Corner' =]

I always recommend flanged nuts on alloy wheels with a steel spacer cut to permit the correct amount of crush to hold the wheels.

While I am on the subject, don't have the wheel stud thread below the hub face. The shear forces there might just decapitate the studs!

Pat

PS, even on centrelocks, the wheels should be spigoted!

[JasperC]

In 2009 we had a wheel flying off during testing twice. We were using relatively old aluminium centres (made in 2006) which were not coated in any way.

The problem was not the wheels themselves failing, but the tapered nuts getting loose causing the studs to shear under braking. We attributed this to surface wear on the centres (steel nuts on aluminium centres, yeah...).

In 2010 we had new centres made and we did have them anodized, but I don't know what type of anodizing was applied. We had no issues at all with fatigue or loosening nuts during this year (with lots of testing). No-one knows what will happen if these wheels are used for 3 or 4 years though... http://fsae.com/groupee_common/emoticons/icon_smile.gif

Best regards,

Jasper Coosemans
DUT Racing Team 2008-2010
Delft University of Technology

[Pennyman]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Big Mo:
I have a feeling if we all magnaflux'd last year's wheels we'd find something at the spoke bases...its the stuff you can't see that gets you.

Thanks to Bill Wright for pointing me in the right direction. Do you know how common the Alodine/Iridite treatment is? Will the average ano shop be able to do this? </div></BLOCKQUOTE>

Great thread!

Alodine is a trade name for a conversion coating used when electrical conductivity is important in corrosive environments. It's a pretty common coating in the biomed industry http://fsae.com/groupee_common/emoticons/icon_wink.gif

In terms of corrosion inhibitors, paint would probably be good enough because few teams need to maintain electrical conductivity to their wheels, but if you really wanted a surface treatment like Alodine, most shops should be able to do it.

[Charlie]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by PatClarke:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Are not tapered nuts needed to center the wheel? Are you referring to a centerlock wheel nut, or a pattern of nuts? </div></BLOCKQUOTE>

Nope, I am talking about ordinary wheelnuts.


Tapered wheel nuts on aluminium wheels slowly but surely bury themselves in the wheel. The this can cause stress concentrations and can generate cracks that can eventually cause the wheels to fail. </div></BLOCKQUOTE>

Isn't this an issue of the surface area, and not simply a 'tapered wheel nuts cannot be used on aluminum wheels' issue?

The Auburn cars all used aluminum wheels with tapered lug nuts, still use the same system; some of these wheels are going on 7 years of use and abuse. Of course, they aren't as tiny as some of the designs out there either.

The vast majority of production vehicles use tapered nuts on aluminum wheels. Surely they aren't all a safety issue?

I do agree that the nust should not be used to center the wheel, and only to hold it in place...

[sbrenaman]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Charlie:
The vast majority of production vehicles use tapered nuts on aluminum wheels. Surely they aren't all a safety issue?
</div></BLOCKQUOTE>

I heard this at a Steve Fox seminar and this is a typical FSAE discussion similar to the "rod ends in bending" discussion.

Yeah it's not best-practice to use tapered lug nuts as a method of both holding the car's weight and holding the wheels on. Just because you have tapered lugnuts on alloy wheels doesn't mean you're guaranteed a failure or you won't win competition. It just means that you should justify why you used that method of wheel-attachment over other (superior?) methods.

Rod ends in bending are fine, so long as they're large enough to handle the loads seen off-axis. But... if you're large enough to handle off-axis loads, are you too heavy?

This sort of weighted engineering compromise is exactly why FSAE is the most awesome thing on the planet.

[Big Mo]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by sbrenaman:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Charlie:
The vast majority of production vehicles use tapered nuts on aluminum wheels. Surely they aren't all a safety issue?
</div></BLOCKQUOTE>

I heard this at a Steve Fox seminar and this is a typical FSAE discussion similar to the "rod ends in bending" discussion.

Yeah it's not best-practice to use tapered lug nuts as a method of both holding the car's weight and holding the wheels on. Just because you have tapered lugnuts on alloy wheels doesn't mean you're guaranteed a failure or you won't win competition. It just means that you should justify why you used that method of wheel-attachment over other (superior?) methods.

Rod ends in bending are fine, so long as they're large enough to handle the loads seen off-axis. But... if you're large enough to handle off-axis loads, are you too heavy?

This sort of weighted engineering compromise is exactly why FSAE is the most awesome thing on the planet. </div></BLOCKQUOTE>

If anything rates as a design error of the month, avoiding it like the plague is a good starting point, understanding it and finding a solution is the final point. There are some design aspects on an FS/FSAE car that require compromise, and rod ends in bending and tapered lug nuts are not in that category. Even if it wont save you weight, good design practice isn't just points, it's pride and fit/finish. That is why we aren't anodizing the wheel centers this year: its something that is inherently bad for fatigue life, even if it can't be quantified.

And FWIW, you probably won't win a competition with rod ends in bending.

[sbrenaman]

I think the intent of my post was lost. I'm not advocating using rod ends in bending or tapered lug nuts on alloy wheels, I'm saying they can be used with compromise (like nearly everything on our cars). Whether or not the compromise is worth it, is up to each individual team. http://fsae.com/groupee_common/emoticons/icon_wink.gif

[EHog]

Careful... FSAE wheel centers break for like... no reason at all.



And so, you blame it on anodizing?????!?!?!?!?!

[flavorPacket]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Charlie:
I do agree that the nust should not be used to center the wheel, and only to hold it in place... </div></BLOCKQUOTE>

While we're on the subject of substandard but likely functional solutions, let's not forget aluminum nuts. Over the years I've seen many top teams (dynamic and in design) use these without issue. Just do your fastener calcs right and throw them out frequently.

[thewoundedsoldier]

The sad thing is that soooo many people (including me from two years ago) read this forum and take everything said in its confines as gospel. I am sure we are actually going to see a significant decrease in anodized wheel centers because of this thread. It's silly.

"Don't ask for guarantees. And don't look to be saved in any one thing, person, machine, or library. Do your own bit of saving, and if you drown, at least die knowing you were headed for shore."

[flavorPacket]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by thewoundedsoldier:
I am sure we are actually going to see a significant decrease in anodized wheel centers because of this thread. It's silly.
</div></BLOCKQUOTE>

It's silly to increase the fatigue life of a cyclically loaded part?

[Big Mo]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by flavorPacket:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by thewoundedsoldier:
I am sure we are actually going to see a significant decrease in anodized wheel centers because of this thread. It's silly.
</div></BLOCKQUOTE>

It's silly to increase the fatigue life of a cyclically loaded part? </div></BLOCKQUOTE>

This is my thinking. Just because our anodized (and over-built) wheel centers from last year haven't failed yet, it doesn't mean that a new design won't.

Any increase in fatigue life allows either
A) A lighter part with the same fatigue life.
B) The same part with more peace of mind.


I would say that very little on this forum is taken as "gospel", and that if anything it raises more questions than it answers much of the time. The ideas that are taken for granted around here are ones that are obviously bad design, not things that are interpreted as "thinking outside the box". I would also say that surprisingly few people in the FSAE class regularly read this forum.



Also, flavorpacket, in regards to your previous post, the rules (new for this year) say that centerlock-style wheel nuts need to be hard anodized and in pristine condition, seeming to indicate that the majority of teams use aluminium over steel. Whatever the case, we are having 4 or 5 sets made (2 for testing, one for each of the two comps we are attending, 1 for retirement age).

[exFSAE]

I'd argue that much of this is moot. Majority of FSAE parts I see (or worked on) were either way overbuilt and lasted forever, or were designed poorly and failed quickly.

I'm sure we could go on and on about microcracks in hard anodize and its effect on fatigue life.. or hydrogen embrittlement and electroless nickel plating, blah blah blah.

It's FSAE - let's keep levels of significance in mind. I'd argue there's probably a much higher chance of failure from just poor design, analysis, fabrication, or maintenance and shop abuse than true high cycle fatigue. This is beside the point that with some of these components, stiffness may trump stress as a design criteria.

Just one man's opinion here.. but when I was designing wheel centers (and aluminum uprights, etc) and choosing surface treatments I was primarily interested in something that would be hard enough to resist the nicks, scratches, dings, and gouges of bare aluminum in the hands of a bunch of inexperienced undergrad monkeys. Galling as well now that I think of it. Aesthetics were a 2nd priority.

There are a variety of surface treatments that meet the 1st goal. I really think nickel wins the second. Nickel plated centers on a semigloss black rim... oh my!

[thewoundedsoldier]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Majority of FSAE parts I see (or worked on) were either way overbuilt and lasted forever, or were designed poorly and failed quickly. </div></BLOCKQUOTE>

There is always that third class of parts which have just enough mettle to make it through testing, then let go of themselves as soon as comp starts =(

[sbrenaman]

I'd say you didn't do enough testing http://fsae.com/groupee_common/emoticons/icon_wink.gif

[RobbyObby]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by thewoundedsoldier:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Majority of FSAE parts I see (or worked on) were either way overbuilt and lasted forever, or were designed poorly and failed quickly. </div></BLOCKQUOTE>

There is always that third class of parts which have just enough mettle to make it through testing, then let go of themselves as soon as comp starts =( </div></BLOCKQUOTE>

You just had to bring that up, didn't you? http://fsae.com/groupee_common/emoticons/icon_wink.gif

[thewoundedsoldier]

Haha both teams suffered that one together! Different mistakes, same effect. Plus we had our batteries die the day after. -1.

[Thrainer]

The rule about aluminium center-lock wheel nuts has been in the FS rules for a couple years, though. We've never needed more than two sets of aluminium center-lock wheel nuts in one season.

We have become aware of fatigue life of 7075 aluminium when two of our wheel centers failed last year, in their fourth season. Crack initiation by small scratches is a probable scenario, and the spokes broke exactly at the spot with the highest shear and von Mises stresses. 7075 has a much faster crack propagation than e.g. 2024. They were not anodized, but painted after using them naked for one season.

Regards,
Thomas

[Gruntguru]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by PatClarke:
In 2008 at FSG I was hit by a loose wheel wheel.

Pat </div></BLOCKQUOTE>
. . and you've suffered from Palilalia ever since?

[jd74914]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Gruntguru:
. . and you've suffered from Palilalia ever since? </div></BLOCKQUOTE>

Wow. That was rough.

[PatClarke]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Palilalia </div></BLOCKQUOTE>
No I no I no I don't don't don't !!

Pat Pat

[Thrainer]

How do you like those wheels?
Assembled centers and shells: http://twitpic.com/51n91b
Wheels on the car
http://www.amzracing.ch/amz/files/28.jpg

The centers weigh under 0.5 kg, the assembled wheel (13x7.5") is 2.7 kg. Concerning the finishing, I left the centers bare and the entire wheel will be painted.

Some designs that inspired me in one way or another were UWA, RMIT, UTA, DUT and Oxford Brookes.

Regards
Thomas

[Adambomb]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by sbrenaman:
I'd say you didn't do enough testing http://fsae.com/groupee_common/emoticons/icon_wink.gif </div></BLOCKQUOTE>

And yet again, back to the classic FSAE balance...if you just bought a set of Keizers and installed them with tapered lug nuts, could you justify that by having X more hours of testing? My typical experience with FSAE still points me to believe that you could get a lot more dynamic points by doubling your testing time than by shaving even 1 kg off the wheels. Especially if your starting point is the amount of testing most FSAE cars get...

[Zac]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Adambomb:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by sbrenaman:
I'd say you didn't do enough testing http://fsae.com/groupee_common/emoticons/icon_wink.gif </div></BLOCKQUOTE>

And yet again, back to the classic FSAE balance...if you just bought a set of Keizers and installed them with tapered lug nuts, could you justify that by having X more hours of testing? My typical experience with FSAE still points me to believe that you could get a lot more dynamic points by doubling your testing time than by shaving even 1 kg off the wheels. Especially if your starting point is the amount of testing most FSAE cars get... </div></BLOCKQUOTE>

Careful, 2 x 0 is still 0.

[Thrainer]

You're right, Adambomb. We have these aluminium rims for early testing now, so we don't have to wait until we have enough carbon rims (which are 1 kg lighter).

However, you should let each team find their own balance. There are plenty of teams with self-made rims that get the car done in time. Do you have data that shows a correlation between using off-the-shelf rims and doing well at competition?

Regards
Thomas

[Adambomb]

I don't have any data, but I think that's part of my point...it's not right for everyone, so you can't make a blanket statement. But before we start talking about things like "tapered lug nuts being a show-stopper" in design, we must remember that there is always a compromise between having a "closer to ideal" car and a well-developed car.

[pheyden]

I have been lurking around the edges of this thread for a while. While I am not involved in FSAE at the competitive level, I have raced my own car for over 30 years on who know how many continents at places like Riverside Raceway (gone now) Ontario Motor Speedway (gone now) Eastern Creek, Amaroo, Nurburgring, Laguna Seca and others.

In all that time I have never seen a wheel center that has failed under "normal" competition. Sure run into another car or a wall and all bets are off.


I make my own wheels. I cast the centers in 356 aluminum, and have used Keizer and other manufacturer's spun halves. All my wheels have metal inserts and they register on a locating spud on the hub.

www.scuedriatopolino.com/public_html/images/wheel1.jpg

One of my co-drivers at an enduro broke a rear wheel on my car, when the brake caliper fractured and in essence ripped everything off with it.

www.scuderiatopolino.com/public_html/images/Broken wheel.jpg

Sure maybe they are not the lightest (but they are light), however I know that they are strong.

Why not use a cast, machined center? If I were going to use a totally machined center I would make sure it had ribs and steel inserts for the nuts. I would NOT make it from 7075-T6. This material, while strong under some conditions, does not have enough ductility for a wheel operating in a cyclical environment. I would use 2024 T-3, then machine it to the required configuration and then have it re-heat treated to T-5 specification. This would result in a center with almost the same strength of 7075 but with much greater ductility. (Note: this material/heat treat also works well for aluminum rocker arms as well).

Hope this is of some interest.

Paul Vanderheijden
Scuderia Topolino
www.scuderiatopolino.com (http://www.scuderiatopolino.com)

[PatClarke]

Thanks Paul for your contribution.

The students generally here rotate on a two or three year basis, so often the fundamentals have to be reinforced.

All help is gratefully taken =]

Cheers

Pat