BBSHD and Rohloff - shift sensor?

[kiltedcelt]

So, I've got a BBSHD and in the past I've used it on a cargo bike along with an Alfine 8 speed hub, and NO shift sensor. I learned early on with Alfine hubs that you pause when shifting and I found that the momentary pause before shifting was enough to cut off the BBSHD anyway, so no shift sensor necessary. I might've been playing with fire as there is always the possibility that some instance might occur where I shifted while the motor was powered. However, in the year or so that I ran that cargo bike, I never did that. Now I riding tadpole trikes exclusively and I'm building up a trike to be my daily commuter/cargo hauler/all-rounder and this trike has my Rohloff hub in the rear and will get the BBSHD. Since the Rohloff utilizes brake cable housing for it's shifter, that kind of precludes using a traditional shift sensor since the housing won't fit into the ends of the sensor anyway. I've read in the past about folks using a brake cable sensor instead and using a momentary button that you press to manually kill the motor output before you shift. Probably not quite as seamless as the sensor which registers the cable movement, but probably adequate.

Let me add one other bit of information first though. The Rohloff I bought was just a basic unit, and at some point when I was ordering the Rohloff-specific spokes to lace it into a new wheel. I got the spokes from Peter White Cycles, one of only two Rohloff service dealers in the US, and when we were talking about my use of the hub Peter pointed out that since I was using in a tandem at the time, and intended to use it with e-assist, I needed to upgrade the internal sheer pins. Turns out I'd not purchased a tandem/e-bike specific Rohloff, but just a regular one. I sent the hub to Peter and his Rohloff tech upgraded the sheer pins to the steel (aluminum?), ones that are standard in the tandem/e-bike specific Rohloff hubs. These pins apparently resist greater torque forces imparted by tandem riders as well as the input from a mid-drive motor, or both.

Anyway, so my Rohloff is basically e-bike specific, but I've not found good solid information on exactly how I SHOULD handle the shifts with BBSHD+Rohloff. Is my practice of ceasing pedaling while shifting adequate enough, or should I be installing an actual cutoff that uses a momentary button? I guess the latter would be installed on one side and I would press it as I stopped pedaling and shift then release. Seems like it would work, but again - just not as well as a shift sensor, and part of me wonders if just stopping pedaling is effective enough. The only issue is when you stop pedaling on a regular chainring/crankset, you're effectively arresting the motion of the chain right then. If you stop pedaling a BBSHD, the chainring/chain can still move a few revolutions from inertia before stopping altogether. I don't know if the shift was occurring while the chain was spinning down if that would cause any issues or not. I suspect even a shift sensor works the same way, and in that regard all you're really concerned about is not dumping power from a motor into an internally geared hub while shifting.

I suspect the spinning-down chain imparts only negligible force into the hub if you're shifting at the same time. Worst case scenario, if shifted under load, I believe the Rohloff defaults into gear 7 as a protection measure then as soon as you left off the pressure on the chain/pedals then the hub will go into the gear it was being shifted into at the time. Worst, WORST case scenario is somehow you engage the sheer pins and those SHEER as their name says, preventing damage to the gears but necessitating sending the hub off for servicing. So, am I just overthinking this entire thing? I mean the Rohloff is a pricey hub and I don't want to trash it. Should I just buy a momentary switch with HIGO connector and utilize that in place of, or with a Y-splitter on the same line coming off the brake lever? For the record, the brake system is two hydraulic calipers controlled by one brake lever so I've got the basic brake cutoff that consists of a sensor and magnet that I have to rig up on the brake lever anyway. Only problem there would be a LONG extension/splitter since I'd want to run the button cutoff on the left handlebar and the Rohloff shifter/brake on the right. I have several extension cables but not sure if I have enough. Might need to buy more.

 

[Mongo]

On my Rohloff & BBSHD equipped bike with a 3KW high-power controller, I use a shift sensor on the upshift cable (as insurance), along with compressionless derailleur inner cables & 4mm housing, with the Rohloff barrel shifter and 90-degree cable noodles up at the bar. Compressionless housing is recommended for use with some of the aftermarket shifters, such as the Rohbox (maybe too the Cinq).

The "gearsensor.com" shift sensor will accommodate either 4mm or 5mm housing (including the ferrule) - some of the Chinese sensors will only work with 4mm housing.

Unlike the Shimano Nexus/Alfine 8, the Rohloff will impede shifting while under load - so a definite pause is needed, especially when crossing over gears 7 & 8 (the two-stage shift point).

My Rohloff hub still has the nylon sheer pins - as you wrote, "all you're really concerned about is not dumping power from a motor into an internally geared hub while shifting." I have configured the controller to gently ramp up power when using the throttle.

 

[kiltedcelt]

I've had a couple rides now on the electrified trike, and have found that just the usual pause before shifting is adequate enough, however I find that I must wait a half second longer for the chainring to stop spinning, since unlike pedaling without the mid-drive, *with* the mid-drive the chainring spins down a few revolutions after you stop pedaling. Motor cuts out almost instantaneously I believe, but clearly the chainring/chain still moving does seem to affect how smooth the shift is. I suspect it'd be the same whether there was a shift sensor or not. As mentioned - the Rohloff impedes shifting under load anyway. The only thing I think I might want to see about changing is using a programming cable to perhaps make the power curve a bit more smooth with the cadence PAS. It seems like it kind of "torques" on the chain at lower speeds when the pedaling kicks the assist on. Starting from a dead stop doesn't seem to be an issue so much as how the PAS kicks on when coasting at a low speed then pedal a couple revolutions and it kicks on in an obvious boost, even at a setting as low as Level 3. I'll start a separate thread regarding that. For now though, I'd say that the shift sensor with a bone-stock BBSHD and Rohloff hub is probably unnecessary, especially given how one has to shift a Rohloff to begin with.

 

[Grautuefel]

I'll chime in too, I've a BBSHD and rohloff, the standard shift sensor that comes with the BBSHD works perfectly well with the rohloffs shift cables. You can put it on either of them as they both move when shifting. To be honest, I don't even notice the shift sensor as coming off throttle or pausing pedalling is always more than sufficient to unload the gears for shifting.

https://www.amazon.com.au/BAFANG-Sensor-Shift-Cable-Gearsensor/dp/B07LFBPQZM

 

[ccihon]

I have no Rohloff experience, but do have a heavy trike with BBSHD and switched this summer from standard to IGH - an Alfine. Since I had the shift sensor already, I have left it on. I think for any hub it offers a bit of "insurance" - the main thing I have been doing is training myself to shift at "off-power" points, different than with a cassette. I have also come to realize that with something as powerful as the BBSHD, one needs to shift less overall.

I had considered Rohloff, as the online reputation they have is that they are "bomb-proof" - maybe part of that is due to the nondestructive shear pin thing. I didn't ultimately want a two-cable shift or a twist-shift setup, and my budget was lower.

One irritation I have with shift- and brake-sensors is that often rough roads will induce an unintended power cut - it's not clear to me if this is the brake levers (more likely) or is a bit of cable movement on the shift cable. The trike has a rather long cable path, and the frame is unsuspended and a bit flexy.

 

[Mongo]

...
One irritation I have with shift- and brake-sensors is that often rough roads will induce an unintended power cut - it's not clear to me if this is the brake levers (more likely) or is a bit of cable movement on the shift cable. The trike has a rather long cable path, and the frame is unsuspended and a bit flexy.

In my case (first build) it was the shift sensor, or rather, the location I believe. I initially located the shift sensor down near the end of the cable, roughly halfway between the BB and the Nexus 8 hub. Over sharp bumps like root heaves, the power would cut out briefly. I relocated the sensors up farther, in line and secured to the down tube, and the problem has not re-occurred.