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just want to know if 100 NM (74 ft pound force) is enough for the centre castor nut... i know it is dependent on various factors (eg wheel bearings and such) but was wondering what is the usual range for such things. i am refering to the rear wheels. Thanks in advance
just want to know if 100 NM (74 ft pound force) is enough for the centre castor nut... i know it is dependent on various factors (eg wheel bearings and such) but was wondering what is the usual range for such things. i am refering to the rear wheels. Thanks in advance
Thats way too much, if you are using opposed tapered rollerbearings. With tapered roller bearings, you want to tighten the nut and spin the wheel at the same time, tightening until the friction on the wheel notcieably increases. At that point, spin the bearing some more to make the bearings seat. Then back off one notch on your castle nut. That should leave you with adequate preload. If the wheel seems loose, then tighten to the next notch in the castle nut and replace your cotter pin. If you were referring to a center lock wheel nut, then disregard the above information entirely. I would think 74ftlbs may be a little low for a center lock wheel nut.
If you are referring to a Centerlock Wheel nut, then 74lbs is quite low. 7/8" sports racer axles with the norm mag/alum 13x8 wheel take 125lbs.
The proper way to preload a pair of tapered roller bearings is to use a precision ground shim to space the two bearings apart. This will allow you to "overtighten" your spindle nut past your desired preload. It will also help keep your bearings from becoming too loose or too tight under dynamic loading.
Buckingham
[QUOTE]Originally posted by fsae racer:
Thats way too much, if you are using opposed tapered rollerbearings. [QUOTE]
What's the main problem you guys had had in your fsae due to this over-tighten?
I've heard that in sedans the main issue is the tapered roller bearing short life.
75 ftlb is fine. We ran that much on our wheels with a .5" thread. I think its overkill actually.
Think about how much damn force that is. 75 ftlb, .5" bolt.. 7500lbf! (33.6 kN)
Likewise 125 on a 7/8 is about 7000.
I would say 5000lbf preload on a wheel for an SAE car (that at best is going to generate say 900lbf cornering at a single wheel) is more than enough, especially if you run LH thread on one side of your car and RH on the other. 4000 might even work. For the 1-1/4 threaded hub I'm designing, with some moly lube, 75 ftlb would work. I might go to 100 though.
Some of the bearing problems this year I attribute to overtorque-ing wheel assemblies. Drasyically can cut down your service life.
Atlantic cars run 250 to 500ft-lb on their wheel assembly parts, but they run probably 2" threads and weigh 3x as much and generate probably twice the cornering g-load.
Colorado FSAE | '05 - '07
Goodyear Tire & Rubber | '07 - '11
NASCAR Engineer | '11 - ??
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
Some of the bearing problems this year I attribute to overtorque-ing wheel assemblies. Drasyically can cut down your service life.
</div></BLOCKQUOTE>
Likely story. I wouldn't call one Brad on a 1 foot long wrench "overtorque-ing"
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