donn wrote: ↑
May 13 2020 10:07am
HK12K wrote: ↑
May 13 2020 8:10am
Pas: must not start until 3kmh (less than one pedal rotation, 3 comes quickly) and must stop when you stop pedaling.
Is that how all PAS works? I've never used PAS, but that sounds like a "cadence" based system. I would be very
disappointed if a system with a torque sensor worked like that. For me, the "or" conjunction gets manufacturers off the hook because whether they have PAS or not, they can provide something that will serve as on/off switch.
It all depends on the system. There's a lot of posts and threads discussing various PAS systems, if you poke around, to see details on specific systems.
For instance, some of them simply require that the cadence sensor reports a minimum RPM. You can achieve that with more magnets or different gearing, etc.
But if the local legal requirement is that it work that way, then it has to work that way or it's not legal to use.
So there are a lot of systems that are crippled in this or similar ways, simply so they comply with laws (but there's no physical reason they have to do that).
For my CA v3-controlled PAS, I have it setup so that on my lower gears it only takes a 1/4 rotation of the cranks to engage and start powering the system. But at that gearing, the torque sensor is fairly useless once it actually *is* started, so I just use pure-cadence control of the system. What I would prefer is that the CA allowed pure torque to startup, and control via pure torque or torque/cadence after that, and I wouldn't need such super low gearing to get started. But it doesn't, so this is how it works for me, until I build electronics to get around this, someday (maybe).
For the on/off PAS systems like my Fusin kit, and a few others I've tried out while helping others with their bikes, it just kicks on once you've reached a certain cadence (in a couple cases a certain speed, one of them not until almost 5mph, so at really low speed, and trying to startup from a stop with a heavy load, etc., you don't get any help at all, which makes them useless for me). When they do kick on, you get the full power of whatever PAS level you've picked, which may be more than you want for the speed you want to go, so you stop pedalling, and then a couple seconds later it gets around to stopping assistance, then you drop in speed enough and start pedalling, and then a couple seconds later it gets around to starting assistance, and you go thru this vrooom-putt-putt-vrooom cycle over and over. For those systems, disabling the PAS (where possible) and just using a throttle is the only simple way to get good control over them.
For proportional-PAS-cadence systems, like the CAv3 system I'm using now, control is usually pretty good, though they may also have a lower limit to where assist will start, which you may be able to work around, or you may not.
Some systems may even go by pure torque, but I don't know which (if any) those might be, other than perhaps BionX (sensor inside the motor/axle), which is extinct. Maybe Stromer (sensor in the rear dropout).
So...you'd have to look at the specific system you want to use and see how it's PAS behaves, according to people that use it. If no one has reported details like that, then you might want to just skip it and go to one that does have such details available (because the sellers / manufacturers probably won't be able to tell you the actual operation mode, based on what I've seen when I've looked for this info in the past).