Perhaps not so strangely, I don't see any efficiency figures anywhere.
You'll also notice that this is a smooth steel-on-steel friction drive that requires a huge preload to not slip under even moderate input torque. That preload will also take its toll on efficiency. This is not a new mechanism. It is one of those commonly used in machine tools where the V-belt Variomatic is not desired.
Perhaps not so strangely, I don't see any efficiency figures anywhere.>
You'll also notice that this is a smooth steel-on-steel friction drive>that requires a huge preload to not slip under even moderate input>torque. That preload will also take its toll on efficiency. This is>not a new mechanism. It is one of those commonly used in machine tools>where the V-belt Variomatic is not desired.
Ah, yes, a mechanism that one machine shop foreman of my acquaintance liked to call "the expensive fuckup waiting to happen", due to the rather precise and extremely finicky lubrication requirements of the one they had. Apparently, theirs had been trashed once by somebody who topped up the lube level with the wrong stuff. Some versions may be more tolerant, but it's a design that's just fraught with possibilities for failure in my estimation. ISTR that GM very briefly tested such a CVT for automotive use. *Very* briefly. The phrase "absolutely intolerant of contaminants in the lubricant" sticks in my mind for some reason. -- Typoes are a feature, not a bug. Some gardening required to reply via email. Words processed in a facility that contains nuts.
In article <1114145638.076625.222110@g14g2000cwa.googlegroups.com>, JeffWills <jwills@pacifier.com> wrote:>Hmmm... if I were still living in San Diego, I'd check them out. I>wonder if it's related to the Nupace hub: http://www.nupace.com/
They're related only in that both have fundamental follies. Fallbrook is a friction drive and is stuck between losses and slippage.
The Nupace is a ratchet-type "CVT". Carl Fogel dug up the patent filing last year:
This is pretty much exactly something I'd sketched up 10 years before the patent, after seeing pictures of Bridgestone's so-called CVT hub around '86. It expands on the range of ratios availble from Bridgestone's design by essentially ganging several of them in series, but otherwise inherits all the same shortcomings.
The input/output transfer is not smooth, though this isn't necessarily a problem for pedal drive (comparable to having a somewhat lumpy chainring shape). Also, as with all ratchet-type mechanisms, it does not actually provide a continuum of ratios. Each pawl of the drive must slip past an integer number of teeth per rotation, and the discrete steps in number of teeth passed means discrete steps in overall gear ratio. I don't know how many teeth the ring gear uses, but if we gratuitously call it 80 teeth, for the 1:1.25 range of each stage, there's actually only 20 distinct gear ratios. Worse, the eccentric cam design doesn't isolate cam positioning from drive torque.
