[hpv] Steering head bearing loads in front-drive bike

[Garrie Hill]

One of the things I've pondered over the years is, "Why do we use ball or roller bearings in head sets?"  Nothing is rotating more than a couple degrees ( more than 90% of the time) plus or minus, and a good shock through the wheel into the fork can cause indentation of the balls into the races.  Use a bushing and you spread forces over infinitely larger bearing surfaces than the contact area of balls/races.  In the case of MBB FWD, bushings have the added advantage of extra drag dampening some pedal induced oscillation.

 
Garrie "carbon based lifeform" Hill
HPRA Co-Dictator of the East
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On Aug 12, 2013, at 10:55 AM, Ben Brown <hbb at cs.cmu.edu> wrote:

I'm working on a front-drive bike, similar to Tom Traylor's design (http://traylor_fwd.home.mindspring.com/) or Cruzbike (http://cruzbike.com/). I was considering the loads on the headset bearings, since the pedaling loads will be transmitted to the front fork assembly through these, along with the usual load from the weight on the fork. With strong pedaling thrust (I assumed 200# to be possible), I estimate the side load on the lower headset bearing to be around 400#-500#, depending on the headset bearing separation. This seems like a lot for typical steering bearings, certainly more than would be encountered in a conventional diamond-frame bike. Has anyone else considered or had experience with this?

I'm attaching a copy of my analysis, in case anyone is interested in the details.

	Thanks, Ben

_____________________________________________

H. Ben Brown
Carnegie Mellon University
Pittsburgh, PA
hbb at cs.cmu.edu

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