Quote:
Originally Posted by KSagal
I don't mean to be difficult, but I cannot understand how you snapped it with only 50 pounds of force. That bolt, if not damaged, should easily withstand that pressure.
Many times, a nut may be stripped, or cross threaded, and then the effort to get it tight is not a function of torque at the tightened point, but trying too hard to get the nut to clamp down on the wheel surface.
In other words, you should be able to make the nuts snug to the wheel with your fingers, and then tighten them down with a wrench (to 25 or whatever poundage torque you want).
If you cannot tighten them down with your fingers, but must use a wrench to just get the nut in contact with the wheel, then there is some other impediment to the threads working as they should. That bind can cause a bolt to break.
In this case, I see from some on line segway manuals that the wheel bolts on an i2 should be at 30 N-m, which is 30 newtons at a meter. That converts to about 22 foot pounds of torque, and even the Gen 1 that were at (I think 50 N-m were only at 36 foot pounds.
I found no reference from segway to either 50 pounds of force, or 25 foot pounds of torque for any wheel bolts.
I work with similar hardware all the time. 25 inch pounds is not much at all, and 50 is not either. Even 50 foot pounds is not too much for this bolt, I believe, but I am not here to debate the factory specs, but to say that there may be some other factor involved in the breaking of this bolt.
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The reason you don't find a reference to 50ft-lbs is that there is none; it was in my head. Page 107 of the PT manual specifies '35N-m (26ft-lbf)'. If Segway now specifies 30N-m online (just checked - they
do for the SE), then they've reduced it by ~14% since my 2006 manual was printed. I wonder why.
I've always hand-tightened the nuts against the wheel before using the wrench, so there was no cross-threading or stripping involved.
I clearly remember that trying to reach 50ft-lb resulted in what I thought at the time must be the bolt heads slipping in the plate (not just one). The pointer hovered just below that mark as the wrench continued to move. It's obvious now that I was twisting/stretching the bolts. I should at least have been suspicious and double-checked the spec before continuing.