3-Piece wheels & Bolts

[BMH]

Hello, I have a quick question, for people that run Keizers or similar. If I recall correctly, there are like 16 bolts holding the wheel together. Does anyone run aluminum bolts instead of the grade 8 bolts to reduce rotational mass?

[BMH]

Hello, I have a quick question, for people that run Keizers or similar. If I recall correctly, there are like 16 bolts holding the wheel together. Does anyone run aluminum bolts instead of the grade 8 bolts to reduce rotational mass?

[Nick Renold]

Judging by the recent threads on aluminum wheel nuts, you're going to have to work pretty hard to get those aluminum bolts past the scrutineers (if they notice).

[Tech Guy]

They will!

[EHog]

15 bolt hole pattern. Replacing all steel OEM fasteners with aluminum of appropriate length saves 1.5lbs over all 4 corners. We did it last year at WEST and we were not asked about it. However, we did have some calculations to present to them if needed, AND we had the OEM steel ones ready to go.

[BMH]

EHog: For your calculations, what did you do about forces? Did you just use your braking torque as you highest force acting on the wheel, and from there just determining your shear stress, and such?

Also, what is the exact size of the said bolts? I had measured them a while back but can't remember them off the top of my head.

Thanks!

[EHog]

They are 5/16-18 fasteners. The primary concern was shear, which I believe was calculated using braking forces. We also looked at (in our case) tension on the bolt for the outside wheel in cornering.

[BMH]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by EHog:
They are 5/16-18 fasteners. The primary concern was shear, which I believe was calculated using braking forces. We also looked at (in our case) tension on the bolt for the outside wheel in cornering. </div></BLOCKQUOTE>

Thanks for the info http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Pete Marsh]

You might want to consider the effects of the air pressure when seating the tyre bead. Some rims and tyres might need 50 PSI or more to pop.

Also watch the practice of changing the bolts on mounted wheels. If you forget to let the air out a serious injury is very likley.

Pete

[Maxlaval]

I could be wrong on this having not made any calculs. The bolt should not take any shear loads in this condition because it will be preloaded to a certain value. By doing so, the entire force will be takin by friction between the wheel center and the outside rim.

Max

[JasperC]

Yes, that's how I would design ALL bolted connections... You apply a preload of about 80-90% of the bolt's yield strength and calculate the shear force you can handle through friction between the surfaces. And mind the fact that you might get some grease on the contact surface, which will dramatically reduce your friction coefficient.

That said, my gut feeling says that using aluminium bolts should work OK because these off-the-shelf rims are probably designed for much greater loads than what you see in FSAE. But you need to know what you are doing...

Best regards,

Jasper Cooosemans
DUT Racing Team 2008-2010

[Gruntguru]

Using braking torque to calculate the maximum shear would be way short. IMO the load in a high speed bump situation would be of the same order at least. Rememeber that a bump loading at the contact patch will have three components - static force via the spring, dynamic load proportional to vertical velocity via the damper, plus a component proportional to vertical acceleration acting on all the unsprung mass except the wheel outer and tyre.

The forces due to torque must be added (for the most highly loaded sector) and don't forget the dynamic torque loading also. A sudden brake lock (or launch) creates a torque proportional to contact patch normal force times coefficient of friction PLUS - angular acceleration of the wheel times inertia of the tyre and outer rim.

[EHog]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Gruntguru:
Using braking torque to calculate the maximum shear would be way short. IMO the load in a high speed bump situation would be of the same order at least. Rememeber that a bump loading at the contact patch will have three components - static force via the spring, dynamic load proportional to vertical velocity via the damper, plus a component proportional to vertical acceleration acting on all the unsprung mass except the wheel outer and tyre.

The forces due to torque must be added (for the most highly loaded sector) and don't forget the dynamic torque loading also. A sudden brake lock (or launch) creates a torque proportional to contact patch normal force times coefficient of friction PLUS - angular acceleration of the wheel times inertia of the tyre and outer rim. </div></BLOCKQUOTE>

Noted. With that said, our aluminum bolts worked just fine.

[Drew Price]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Tech Guy:
They will! </div></BLOCKQUOTE>


I'm not sure I would have noticed, esp. on a clean looking, thoughfully built car.

And I KNOW that some of the inspectors I was working with at West last year would not have even though it possible teams would show up with something like that.

As always, it's in your best interest to look like you know what's going on, and to have the car clean, prepped, and ready to go through.

That being said, 5/16ths"-18 bolts for wheel centers are HUUUUUGGGEEE.

I think the bolts for the BBS wheels I bought 2 years ago were something like M6x1.5mm, or maybe even M5, I don't recall, but they were very small, although there were about 22 of them.

Maybe a better option would be to keep the steel bolts, but go to thin ground machine washers and half-height all metal nuts rather than hardware store washers and Nylocs? You also might be able to go crazy and do drilled hollow steel bolts as well and still keep the preload of steel threads.

[BMH]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Drew Price:

Maybe a better option would be to keep the steel bolts, but go to thin ground machine washers and half-height all metal nuts rather than hardware store washers and Nylocs? You also might be able to go crazy and do drilled hollow steel bolts as well and still keep the preload of steel threads. </div></BLOCKQUOTE>

Yeah, you could drill out the bolts to make them hollow, however, when you have 15 per wheel for a total of 60 bolts...plus a few more for extras, that takes A LOT of time!

[Gruntguru]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by BMH:
Yeah, you could drill out the bolts to make them hollow, however, when you have 15 per wheel for a total of 60 bolts...plus a few more for extras, that takes A LOT of time! </div></BLOCKQUOTE>Or you could buy hollow race bolts or Titanium. Don't forget to include them in your cost report. http://fsae.com/groupee_common/emoticons/icon_wink.gif

[BMH]

Just out of curiosity, where do you all get your aluminum bolts, hollow race bolts, and/or titanium bolts from?

[Drew Price]

I think Aircraft Spruce has or could get most of it, you'll pay a pretty penny though.

[BrendonD]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Drew Price:
I'm not sure I would have noticed, esp. on a clean looking, thoughfully built car.

And I KNOW that some of the inspectors I was working with at West last year would not have even though it possible teams would show up with something like that.

As always, it's in your best interest to look like you know what's going on, and to have the car clean, prepped, and ready to go through.

That being said, 5/16ths"-18 bolts for wheel centers are HUUUUUGGGEEE.

I think the bolts for the BBS wheels I bought 2 years ago were something like M6x1.5mm, or maybe even M5, I don't recall, but they were very small, although there were about 22 of them.

Maybe a better option would be to keep the steel bolts, but go to thin ground machine washers and half-height all metal nuts rather than hardware store washers and Nylocs? You also might be able to go crazy and do drilled hollow steel bolts as well and still keep the preload of steel threads. </div></BLOCKQUOTE>

I concur on the 5/16-18 bolts being overkill. Also the BBS wheels only have 12 bolts in them, not 22, and you're probably right on the money with the M6x1.5 The old Keiser's had way more than that if I remember correctly. (I don't feel like digging those out of the pile of crap in the garage)

Last year at comp I was talking to UTA about titanium fasteners. They used them quite a bit throughout their car, I held 5 regular vs 5 titanium in my hands and I could definitely see the advantage in weight savings, though I think that wouldn't be first on the list of things I would "add lightness" to from a cost vs benefit standpoint.

[Wesley]

Don't forget the reduction rotational moment of inertia!

Ti bolts are nice, but they can be a real pain if you ever need to remove them. Even with liberal amounts of anti-sieze, we've had stripping problems with Ti bolts.

[Big Mo]

Mmmm, tasty, tasty galling.

I believe the late, great Mr. Smith had something to say about Ti fasteners in Engineer to Win.

Although wheel centers fit the profile for being the ideal application of Ti bolts (one insertion per use, ability to turn NUT to tighten, etc), would you really want to use something super notch sensitive in a use that is seeing a figurative ton of axial fatigue?

Factor in a student workshop environment and 48 chances (if you are on 10" Kaizers) to scratch a bolt, and it starts to seem like not a great idea.

[Drew Price]

IIRC our BBS's had little nutserts on the rear rim shell so that you actually did turn the bolt, they didn't use standard nuts on the back side.

Drew

[Thrainer]

Drew, how did you secure the screws which went into the nutserts? They're considered critical fasteners, I guess?

Regards,
Thomas