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La fiera
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FEB 22, 02:30 PM
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| quote | Originally posted by pmbrunelle:
Before I ordered these hubs from Brian, I had this discussion with him.
My question:
Since the hub is aluminium, but the spindle is steel, have you heard of problems from the hub expanding with heat, making the bearings run too tight?
Brian's answer:
I haven't nore have any of my customers experienced any problems with dis-similar materials. 3 of my customers use my hubs on all out race cars including one that does 12-24 hour endurance races. No problems to report in the past 5 years.
I was satisfied with his answer (especially the part about the 12-24 hour endurance races), so I decided to try his hubs. |
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Ok. I'm curious because I saw a video on YouTube of a Fiero at an endurance race loosing a front wheel with the hub attatched to it.
What's the weight difference between the aluminum vs steel counterpart?[This message has been edited by La fiera (edited 02-22-2021).]
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pmbrunelle
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FEB 22, 07:44 PM
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On the car with the hub that fell off, was it a stock (or modified stock) hub, or a Brian Sanburn hub?
According to this thread, the weight saved is 4 lbs per hub:
http://www.fiero.nl/forum/Forum4/HTML/078405.html
It would be a good idea to jack up the front of the car after running it hard, and then verify that the wheel bearings still have a small amount of play.
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Will
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FEB 22, 07:49 PM
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| quote | Originally posted by pmbrunelle:
On the car with the hub that fell off, was it a stock (or modified stock) hub, or a Brian Sanburn hub?
According to this thread, the weight saved is 4 lbs per hub:
http://www.fiero.nl/forum/Forum4/HTML/078405.html
It would be a good idea to jack up the front of the car after running it hard, and then verify that the wheel bearings still have a small amount of play. |
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Or, to observe indirectly... instrument spindle temperature?
Gun drill the spindle and epoxy a TC or other temp sensor into the hole out at the tip...[This message has been edited by Will (edited 02-27-2021).]
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La fiera
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FEB 22, 10:51 PM
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| quote | Originally posted by pmbrunelle:
On the car with the hub that fell off, was it a stock (or modified stock) hub, or a Brian Sanburn hub?
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If it is was stock hub, it was neglected. I can't seem to trust those aluminum hubs for racing. (Drag racing yes, road racing; hell no).
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La fiera
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FEB 22, 10:55 PM
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. [This message has been edited by La fiera (edited 02-22-2021).]
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ericjon262
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FEB 22, 11:14 PM
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| quote | Originally posted by La fiera:
If it is was stock hub, it was neglected. I can't seem to trust those aluminum hubs for racing. (Drag racing yes, road racing; hell no). |
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how about aluminum wheels?------------------
"I am not what you so glibly call to be a civilized man. I have broken with society for reasons which I alone am able to appreciate. I am therefore not subject to it's stupid laws, and I ask you to never allude to them in my presence again."
cognita semper
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La fiera
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FEB 23, 09:21 PM
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| quote | Originally posted by ericjon262:
how about aluminum wheels?
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That's a different story. Just the size difference between the hubs and the wheels should answer that question for you. The aluminum wheel due to its size can disipate heat very fast compared to a diminutive aluminum hub.
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ericjon262
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FEB 23, 10:26 PM
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Since you brought up heat we'll do some math, the coefficient of thermal expansion of 6061 aluminum is about
13.1 μin./in. ·°F.
1μin =0.000001 in
we'll say the hub is 6" long we'll get extreme and say the hub gets 400F hotter than ambient, the drop point of typical bearing grease is about 500F, so this would put the grease close to turning liquid.
The formula for linear expansion is
L=L0⋅(1+α⋅ΔT)
L=length final
L0=initial length
α=coefficient of expansion
ΔT=difference in temperature
L=6"(1+0.0000131*(400)
our final length works out to be 6.03144"
but, we can't discount the expansion of the spindle too, we'll say it's also 6" for simplicity. the expansion coeffcient for steel is about 1/2 that of 6061, at 6.8 μin./in. ·°F
using the same equations as above, we come up with 6.01632" for the final length of the spindle a difference of about 0.0152"
A note about the math, coefficients of expansion aren't necessarily linear over large transients, so for the calculations to be 100%, they would need to be calculated at different ranges and added together, not just as one equation as performed here. it's also worth noting that the thermal conductivity of aluminum is much higher than iron or steel, so it will likely dissipate heat better than the steel piece, and remain cooler.
Corvettes and numerous other vehicles use aluminum knuckles, with probably only slightly more mass than a hub like this, and still have to absorb the heat generated in the hub, as the cartridge style bearing is inside the hub.
tl;dr
I don't think heat will be a problem unless you have another problem causing insane temperatures in the hub.------------------
"I am not what you so glibly call to be a civilized man. I have broken with society for reasons which I alone am able to appreciate. I am therefore not subject to it's stupid laws, and I ask you to never allude to them in my presence again."
cognita semper
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pmbrunelle
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FEB 23, 11:27 PM
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| quote | Originally posted by ericjon262:
our final length works out to be 6.03144"
but, we can't discount the expansion of the spindle too, we'll say it's also 6" for simplicity. the expansion coeffcient for steel is about 1/2 that of 6061, at 6.8 μin./in. ·°F
using the same equations as above, we come up with 6.01632" for the final length of the spindle a difference of about 0.0152"
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The length of the aluminium hub that is sandwiched between the steel bearing cups is about 1-15/16" (I just measured it), so it's about three times less than the 6" figure you used in your example.
So adjusting your 0.0152" figure for the length I measured, that gives 0.0049" of growth (keeping your same assumptions).
It's not insignificant, considering that the bearing endplay is probably around 0.005" at room temp. It's hard to give an exact number; I usually use my feel-o-meter to adjust this type of bearing.
I've never broken out the dial indicator for adjusting wheel bearings. Maybe I should, this time.
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ericjon262
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FEB 23, 11:44 PM
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| quote | Originally posted by pmbrunelle:
The length of the aluminium hub that is sandwiched between the steel bearing cups is about 1-15/16" (I just measured it), so it's about three times less than the 6" figure you used in your example.
So adjusting your 0.0152" figure for the length I measured, that gives 0.0049" of growth (keeping your same assumptions).
It's not insignificant, considering that the bearing endplay is probably around 0.005" at room temp. It's hard to give an exact number; I usually use my feel-o-meter to adjust this type of bearing.
I've never broken out the dial indicator for adjusting wheel bearings. Maybe I should, this time. |
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I don't think I've ever seen someone use a dial indicator on a wheel bearing.
The other aspect to consider is the ACTUAL temperature of the components, I doubt they're running at 400F+ like my assumption states. Maybe I'll take the Suburban down the interstate for a bit and try and put some heat in the front hubs and see what they look like with my FLIR. ------------------
"I am not what you so glibly call to be a civilized man. I have broken with society for reasons which I alone am able to appreciate. I am therefore not subject to it's stupid laws, and I ask you to never allude to them in my presence again."
cognita semper
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