Pinion P1.18 bicycle gearbox How it works
Well those German engineers have been at it again. Frst they gave us the Rohloff 14 speed gear hub. Now we have something called the Pinion gear box. It’s a bottom bracket mounted 18-speed gear. It’s also available in 12 and 9 speed versions but today we’re going to take a look at the 18 speed version. Geared bottom brackets are not exactly a new idea. This particular one was available back in the thirties. I believe it was a three-speed. I did some reading on it I forgot the details but it also required a specially manufactured frame not retrofit able to a normal bicycle frame. Now unfortunately I don’t happen to have one of these here that I can get my hands on, but I do have pictures that I’ve been able to grab off the net and from that I’ve been able to figure out how the thing works and today I’m going to try and explain it to you. Okay so what we’re looking at here is the left side looking at it from the point of view of looking from the front of the bicycle towards the rear. Here we have the input shaft where the cranks mount and it’s also the main shaft of the transmission. This is the countershaft of the transmission. This planetary system that you see on the left end of it is actually the shift mechanism. The shifting is accomplished by means of rising pawls in the countershaft. All of the countershaft gears are free-floating on the shaft and they are engaged to the shaft by means of the rising pawls actuated by the shifter. The six gears on the left end of the input shaft are splined to the input shaft. In other words as the shaft turns all six of these gears turn dedicated to the shaft. The three gears on the right end of the input shaft are mounted on a hollow tube that the input shaft passes through. These three gears are mounted as a unit that do not turn independently of each other. The six gears on the counter shaft that correspond with the 6 fixed gears on the main shaft as you can see are all of varying sizes so when the largest gear on the counter shaft is engaged to the shaft by means of the rising pawl, it will drive the shaft at the slowest available speed. Why they arranged them in what appears to be such a random order I can’t say I’m sure there’s an engineering reason for it i don’t know what it is but anyway. So we’ve got six selectable ratios here that are engaged to the countershaft one at a time. On the right-hand end of the countershaft we have three gears, again free floating on the shaft and we select those one at a time to give us three distinct ranges so in fact what we have is we have six ratios here which we can multiply three times without any overlap. With these three output gears And now we come to the final output the three gears on the output cluster remember I told you those are mounted on a hollow tube which is free-floating on the input shaft. And the chainring is mounted on the output side of that so that’s where the power flows out of the hub and to the wheel. Ok so just to do a little power flow demonstration here. So we have power input here. The cranks turning the input shaft. Now if we have low gear selected that means that we’ve engaged this largest countershaft gear to the shaft so we have the smallest gear on the input side driving the largest gear on the output side and then over at this end of the hub ah, the hub. I keep calling it a hub this end of the gearbox we engage the smallest gear to the shaft and drive the largest gear on the output so the power flow goes through the through here to here to here and out for the slowest ratio in the transmission . By contrast if we couple the smallest gear on the countershaft. Not even sure which one that is. This one I think alright so if we Lock this gear to the countershaft we have the power flowing from the largest gear on the main shaft the smallest gear so we’re driving the countershaft now at the fastest available ratio. And then at this end if we lock the largest gear to the countershaft now the power is transmitted from that gear to the smallest one on the output and we’re driving the chainring at the fastest available output speed or 18th speed. So that’s it that’s a brief rundown on how it works someday I hope to get my mitts on one and can actually get in there with greasy fingers and show you a little bit more detail but for now that’s the best I can do so hope you enjoyed it. See ya later.