ScooterMan - At the moment I am just using standard square taper freewheel cranks from Sick Bike Parts. The freewheel is from them as well. I am working on a lighter weight solution at the moment, but I haven't decided if it will be something I introduce later, after I make the first small batch production run. The NCTE torque sensing BB is by far the most expensive part. They retail for $240. The #25 sprockets are pretty cheap, about $12-$16 each.
I am working on a solution to fit a SRAM direct mount crank. A freewheel is a significant engineering effort, but making the diameter larger should allow me to use hard anodized aluminum instead of hardened steel bits... keeping the torque sensing strategy to myself for now ... I think torque sensing is critical on a mountain bike when riding technical uphills. I want the complete bikes to be street legal, so that rules out throttles (mostly).ScooterMan101 wrote: The solution that I have been thinking about for a while now, to cut down a pound or more off the BB/Crankset , and , to have better quality BB Bearings and better quality Cranksets ,
To Design a inner sprocket/feeewheel, that bolts right onto existing , Modern 2 piece Cranksets. ( BB30 / Shimano Hollowtec II / Sram Mega / )
I do not use torque sensing , I would guess that many here on E.S. do not, we use throttles. so we would not need that extra expense . just throttle hook up to the controller. and perhaps a PAS as a cheaper alternative for those who do not need torque sensing. So 3 different options for your customers . Throttle only, PAS and Throttle , and Torque Sensing. Three different price points .
Paul,PaulD wrote:... The NCTE torque sensing BB is by far the most expensive part. They retail for $240. ...
Thanks Norton! Direction of rotation is needed for torque sensing middrives too, since this type of sensor only measures leftcrank torque. Otherwise you would get a throttle response when standing on the pedals (with your left foot forward) and rotating the cranks backwards a bit... Using it for Regen on hub motor would be hilarious though!Norton wrote: Your build here looks really nice and is now proven! Congrats!
I'll be following this thread!
I agree with you on Torque Sensing with a mtb. Just shifting in general sound goofy with a simple PAS system.
I looked at the NCTE BB. One model had "Direction of Rotation" as one of the sensors. I thought wth is that for?
Progress is slow right now, working out issues with BMS, wiring, motor assembly, etc. The display is TBD. I initially decided I didn't need a display, but I think the ability to change modes is important enough to warrant a display/switch.ScooterMan101 wrote:PaulD,
What is the Progress level ?
What all will you be selling with the kit ? ( Sram Direct Mount Crankset as well ? )
( Any other sources for a Direct Mount Crankset besides Sram at this time ? )
Many of use 12 s packs, or even 14 s packs, so the controller will be adjusted for Voltage, and Amp draw
by which Means ... Bluetooth and a Smart Phone ?
The controller will be Sinewave ?
Smart Phone will be the Display for Speed/Watt Draw/Amp draw ?
Progress is slow right now, working out issues with BMS, wiring, motor assembly, etc. The display is TBD. I initially decided I didn't need a display, but I think the ability to change modes is important enough to warrant a display/switch.
Battery will be 10S. I don't see the need to go higher. Controller is from ASI, so it is FOC sinewave.
As for other direct mount cranks, I think Praxis makes them. Unfortunately most brands have their own "standards" like RaceFace, FSA and Cannondale. SRAM seems the most common though. Making a freewheel thin enough to fit in the space of direct mount crank spider is challenging at best.
I want a pack that will fit where a standard size water bottle fits... and I want it lightweight. Since this is a low power system, I can get away with smaller 30 cell battery. I can't find anyone making a pack like this.ScooterMan101 wrote: Since you are designing a Motor Kit , Just Design around the newer make it your self battery pack , ( VRUZEND , Mlt34 )
Yes, the ASI has bluetooth, but it doesn't have an end-user interface.ScooterMan101 wrote: Does the ASI controller have a Bluetooth Dongle or can communicate with a Smart Phone/Small Tablet via Wi-Fi ?
The intention is for this to be a lightweight 350W max assist. This more than doubles most peoples power output. There are plenty of high power kits out there for those that don't want to pedal hard. My kit is for people that just want electric to augment their efforts, not replace them.ScooterMan101 wrote: You are using only 10s pack ? , if so I hope the controller and motor does at least 25-30 amps continuous, at the least. There are some steep hills I need/want to go up. I already have experience with trying to go them at 25 amps and that is just not good enough 30 amps would be more like it, if going up paved roads then up to 40 amps.
The spider of a non-direct mount crankset gets in the way. There generally is very little room between the chainrings and the crank arm to fit anything in there. If someone wants to use a big chainring, it usually has to go on the outside (big ring) position for chainstay clearance.ScooterMan101 wrote: Since Bicycle Cranksets are not made for having a freewheel, although if you use an older 3 chain-ring Crankset , that is not direct mount, isn't there enough space if you get rid of 2 of the chain-rings , put the freewheel on the outside near the crank arm and chainring on the inside to have a better chain line ?
Hi Paul, very elegant design, I think it'd go great on my Yeti SB5.5. Regarding a freewheel, since you're going PAS only, could you not bypass having a freewheel altogether. A torque sensor could be added to the lower/return side of the #25 chain where it would only be feel the torque from pedalling, not the motor. You'd only need to adapt a #25 sprocket to the crank spider. At 350 watts a motor runaway should be less of a concern, and other safety measures/motor cut off could be built in. Just a thought.PaulD wrote:A freewheel is a significant engineering effort
Thanks Brianv99. I think think riders with nice lightweight mtbs and road bikes will like a kit like this.briangv99 wrote: Hi Paul, very elegant design, I think it'd go great on my Yeti SB5.5. Regarding a freewheel, since you're going PAS only, could you not bypass having a freewheel altogether. A torque sensor could be added to the lower/return side of the #25 chain where it would only be feel the torque from pedalling, not the motor. You'd only need to adapt a #25 sprocket to the crank spider. At 350 watts a motor runaway should be less of a concern, and other safety measures/motor cut off could be built in. Just a thought.