06-22-2016, 08:07 AM | #1 |
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Wheel Spacers
When fitting wheel spacers do you apply copper slip to the back of the spacer or just put them on dry, in case of any possible unwanted vibration noise?
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06-22-2016, 08:26 AM | #2 |
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Never put any type of "lubricant" on the flat surface of the wheel, hub or spacer. Most people don't understand that the bolts/studs that hold the wheel on, do not experience any rotational torque from wheel during operation. All those bolts/studs do is provide "clamping force" on those flat surfaces and the friction between the flat surfaces prevents any movement between the hub and wheel/spacer. Lubricating those surfaces would allow "slip" and resulting torque on the fasteners that the fasteners are not designed to handle.
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08-10-2016, 04:22 PM | #3 | |
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08-10-2016, 05:32 PM | #4 | |
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Torque specifications are for threads free of dirt, grit, corrosion, etc., so the hardware turns freely. While lubricating hardware THREADS is recommended, it is important NOT to lubricate hardware SEATS. The friction which torque is measured against should come from the hardware seats. Lubricating hardware seats can result in inaccurate torque readings and/or over-torquing the hardware. http://www.tirerack.com/wheels/tech/...jsp?techid=107 |
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08-10-2016, 08:38 PM | #5 |
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I can only speak from 43 years in aircraft maintenance and have seen what can happen when fasteners have been overtorqued as a result of lubricant being applied to screw threads when not particularly specified by the manufacturer. Worst case I knew of was a helicopter pitch control horn detachment from the rotor blade due to attachment bolt failure. Fortunately this happened on a ground-run but it would have been far worse in flight - subsequent investigation identified the cause to be inappropriate use of lubricant on screw threads. Unless a maintenance instruction specifies a 'wet' torque figure, it must be assumed that the parts are assembled in a 'dry' condition.
Certainly your article is correct in stating that lubricant must not be applied to hardware seats (faying surfaces) as this will allow increased slippage, thereby amplifying torque, but you can also think of the entire engagement area of a male and female screw thread as being a continuous 'faying surface' - thread friction will be reduced by a factor of around 25% and the applied torque will be increased accordingly. |
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08-10-2016, 10:50 PM | #6 |
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I think you have to consider the difference between aircraft safety factors on fasteners as in your example and the safety factors applied to automobiles. Aircraft parts are much more concerned about weight than are automobiles so there is considerably less design safety factor. The slight increase in torque due to lubricated threads in an automobile wheel fastener is easily accommodated by the more generous design safety factor. And I think TireRack knows something about this subject as it applies to automobile wheel fasteners.
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08-11-2016, 05:49 AM | #7 | |
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The wet torque increase (at least 25%) is far from 'slight' and whilst I'm quite sure that the Tire Rack guys know what they're talking about, I'd prefer to stick with standard engineering practises regardless of whether it flies or stays on the ground. For interest you might like to look at this: Accepted that it's not verified but I think it's a pretty good practical demonstration. Either way, this is not an issue we're going to agree on and I certainly wouldn't want to fall out over it - you see far too much of that on discussion forums. Regards, Jon D. PS: good luck with your seat cushion. |
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08-11-2016, 08:34 AM | #8 |
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I'd just like to make this observation.
I have a problem with the video. Look at it at 4min11sec where he puts a "small amount" of anti-seize on the treads. It sure doesn't look like a small amount to me and if you look closely he even gets some on the nut face. And with that amount of anti-seize on the threads I'm 100% sure that some of that also transferred to the nut face as he threaded the nut. So according to how I see it he didn't follow the TireRack important caution: it is important NOT to lubricate hardware SEATS. And that's were the majority of friction takes place. So I believe the video overstates the case. |
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