Has anybody ever placed a linear potentiometer on both the left and right fork leg to see if they always had equal travel - no weirdness from chatter, front end saves, etc... ? More of an R&D/theory question than tuning...
Before this exercise it would be necessary to know if both linear pots were accurate to each other. I’m not sure what their resolution is
I believe you're going to want matched pots to do this. Thinking along the lines of electrical component tolerances, you may see differing results on each side if they aren't matched
I mean, wheel out, bike on a head lift stand, the range of misalignment that you can still put the axle in and out with is not 0...
I'll bite. Everything is a spring, right? So the fork tubes and axle will have SOME flex in them and possibly allow some minor difference in stroke between the two. I'm sure you COULD measure that distance, it's just a matter of how many 0's you'll need after the decimal. Now, could you measure it with commercially available suspension pots? IDK, what's the resolution on a typical linear pot, 0.01mm?
The axle and triples square the forks. Mostly. If you're trying to measure deflection, linear pots aren't how you do it.
The current plan, as of dinner this evening, is to get a set of cheap used forks, machine a very long axle and some dimensionally correct double clamps (?) that'll bolt the forks horizontally to the top of the weld table (Legos for the vaguely grown-up), and do some load testing. Dial indicators and spring scales will reveal all, I think. Later this winter, I hope. Why? Research. Trying to understand what front ends do as loads change at the limit - and if some of that behavior is the result of strain and misalignment - and if that effect can be reproduced another/better way. Recently, I'm told that adding flexy triple clamps somehow improves feel, traction, and cures premature lowsides. Does the lower fork assembly deflect sideways out of parallel with the upper forks, with the axle and lower tubes remaining square? Or do the lower fork castings flex a little where newer ones are narrow (As seen from the front) between the axle journal and the lower fork tube socket? Or both? What does that really do to the suspension? Do front ends that are supposedly too stiff and "Let go without warning" do so because the forks extend too easily and wash out the front, rather than binding a little and holding the line? I don't know - and I'd like to find out.
The tire is doing a lot of the heavy lifting your theoretical test can't account for. Fork deflection is a known, if not entirely quantifiable, entity. I see it regularly on fork bushings on the forks I service. It (almost) never presents on the lateral and (almost) exclusively presents on the medial plane, because braking is where most of the deflection takes place. What you're talking about is taking the tire (and even the brand and compound of tire will make a significant difference) out of the equation. It's a fun project, but this dog won't hunt. That said, please post up your results.
I have seen scallop cuts in the side of Ohlins forks that are said to be there to add lateral flex to the fork upper stanchions. subbed for data.
That's one of the reasons why I want to test with '07-'08 ZX-6R forks. Besides being dirt cheap, they have a rib on the side of the lower fork tube casting where the latest/greatest are fashionably slender. Testing again after the rib is removed might reveal something. No, I don't care yet about what tires generate which loads (Magnitude is variable - direction is constant) - that sort of test would require a very sophisticated/expensive dynamic test rig. Right now, I'm more interested in "What does it do that nobody seems to coherently comprehend" rather than "How much for every possible application variable". Testing the theory is the first step to getting applicable data.
Push sideways on a modern 150mm potentiometer at full extension and tell me if you think this device could tell you definitively what you looking to analyze. There’s too much slop in your measuring device. You need to look into strain gauges mounted creatively. Prepare to spend a lot.
This. The only time you'd see redundant sensors on any real race bike is for control strategy redundancy. I don't recall 2 pots on any bike but you'd commonly see 2 front/rear wheel speed sensors, and even 2 IMU's stacked on top of each other on some bikes, namely on Marelli Superbikes. If you're at the point of measuring something like this, you need to know that you have the understanding of what the data you're gathering means, otherwise it's just an expensive exercise in squiggly lines.
Many of today's "sportbikes" have a fork and triples bolted to something alot more likely to flex than a fork leg (or fork leg and triple assembly). I'm still curious what you find. But I think as Metric Mike says above, the tire is the ultimate variable.
