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BBSHD AWD Fat Commuter/Cargo/Auto Replacement Bike

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    BBSHD AWD Fat Commuter/Cargo/Auto Replacement Bike

    This is my second-generation AWD bike, Where this bike, and the gen1 I still ride, are both automobile-replacement type commuting/cargo ebikes and not oriented towards recreation. The gen1 bike was/is a dual-geared-hub bike with 52v batteries, 35a controllers, Bafang 750w fat hubs and about 4.4kw peak power. It has dual throttles, brake cutoffs split to both motors and PAS split from one sensor to both controllers. 5 levels of PAS on each wheel makes for a 10-level PAS system on that bike.

    The above is all great, but that bike uses geared hubs. While a 4Kw system can still handle steep hills - and my permanent home is in an area with steep hills - that gen1 AWD is used at my temporary-due-to-work residence in California's Central Valley. The land is all table flat (which is why I can get away with single speed and a 60T front chainring). I want to take what has proven to be a very successful AWD bike and adapt it to one that can handle hills and not break down over the long term. That means mid-drive for a rear motor. Since I am a pedaling kind of guy and must have PAS, and I want as much power as I can get, the logical choice is a 1500w hot rod BBSHD.

    A pic of the finished product, and some component details (right click on any image and open in a new window to see it in colossal size):
    • I scored a relatively cheap titanium frame from a guy who bought the wrong size and tried unloading it right when the frame manufacturer was dumping overstock on ebay. Good timing for me, not so much for him. This frame is made in USA by Lynskey for Chumba, who sells it as the Ursa Major. Thru axle 12x197 in back
    • The racks are Axiom Fatliners. Front rack uses the Axiom axle kit, plus I bent and re-drilled rack center post mount to fit the front geometry. Rear rack uses doubled mount arms - one on the inside, one on the outside of the tubing, so the 50kg capacity reported by the mfr is actually possible.
    • The BBSHD kit is from Luna, as well as another of their bare Bafang fat front motors. As far as I know only Luna sells these fat front motors.
    • I used Weinmann 100mm double wall rims rather than the 80mm double wall rims I used last time. On those,despite thousands of miles of rough roads, heavy loads and Class III Ebike speeds, they remain perfectly true. Also 100mm rims are 20% cooler than 80mm so we’ll go with that.
    • Just 1 big battery this time for daily charging convenience. My battery is actually a refugee from my mini cyclone bike... that was destroyed when an inattentive driver t-boned me in December of 2017. The padding-encased battery was pretty much the only thing that survived undamaged and you see it on the back rack. The 60a/90a BMS and 25R cells on this 52v bad boy, coupled to the 20ah size, is ALMOST enough. If I were to make a battery solution for this bike I would do 2 identical 25R batteries in parallel so I could split the weight to two locations and work in a BMS capable of handling a bit more juice. Maybe 70a continuous for WOT uphill on both motors.
    • The Luna triangle bag holds only patch kit, tools, Lezyne fat bike pump and a spare inner tube. The power cable running forward through the bag from the rack mounted battery has an XT90 break in it so I can at my option add another 17.5ah Luna Storm battery (52v, 25R cells, 50a BMS) to power the front motor exclusively and give me 37.5 ah of 25R, 52v power.
    • DT 350 Big Ride hub in the back. I scored a couple of steel freehub bodies cheap on eBay so when the stock aluminum body goes - and it will sooner not later - I will have a long-term mid-drive durable replacement in hand.
    • Shimano HG-400-9 rear cluster, 11-32. I like the cheaper Shimano clusters for ebikes because they are steel and welded together for the most part, to distribute the force applied to them.
    • I went 9 speed to keep some more meat on the chain.
    • KMC X9e mid drive chain. Because ebike.
    • Lekkie v3 50a-capable, 42-tooth bling ring. I got this barely used from a member of Fast Electric Bike who was beta testing them.
    • 35a peak KT controller for the front motor is in the black bag under the handlebars. That bag has been holed with brass grommets for cable ingress and exit on both sides. The KT controllers have a matching display and support PAS, throttle, brake cutoffs. Very civilized. They also have some customizability and for this bike I used the slow start option that gives me full amps, but rolls the power on slow when you mash the throttle.
    • The BBSHD in the back was originally given the Luna factory hot rod program, but I acquired an ‘economy tune’ from a member of FEB that is much better tailored to a PAS-ridden bike; particularly in how it limits power delivery if more amps don’t end up resulting in more acceleration (i.e. the motor is just lugging).
    • The panniers in the pic are mid-sized 45L models. I also have a pair of 55L bags, plus a set of 65L bags and 20L bags... good enough for just a small increase or a full on Costco run using both racks and 4 bags.
    • Brakes are Magura MT5e new take-offs I got on EBay for about half what they retail for. I am using the E-Bike-Technologies.de HIGO adapter to convert the Magura red HIGO to BBSHD yellow. The KT front motor controller has a red connector already. I have custom cabling that splits the brake signals (from the same source) but the dissimilar controllers don't like being tied together by the brake circuit and both shut down as if the brakes are engaged. So the front motor gets the front cutoff and the rear motor gets the rear cutoff. Not ideal but better than no cutoffs and in practice is ... acceptable.
    The throttles in the pic below are on the left side, together. Inside throttle is the front. Its cocked a little higher so its easy to engage alone, as in from a stoplight. It works reasonably well but is still a work in progress. Down the road I will probably cut the right grip down a little and move it to the right, which is how my gen1 bike is set up.



    All hardware is Grade 8. I like the thick oversized 9/16" washers as just a bit of extra fail-safe to hold the rack mount in place. Thread engagement on the narrower non-shouldered bolt is precisely 100% - no room for anything more. There is a serrated ring washer hiding under that bolt and its clocked so if I see any movement I can address it. the torque arm - there's one on each side - is a 5mm CycleEzee/Grin arm. Since this pic was taken I have added a further support that attaches to the fork blade.



    The frame came with ISCG tabs which I ended up having to cut off with a dremel, a respirator (titanium dust in your lungs can’t be good) and a few cutoff wheels.



    Once cut off, 8.3 mm worth of spacers gave me the closest clearance to the chainstay possible. 8mm came from two Luna spacers and the last 0.3mm came from a Wheelsmith 0.3mm cassette/BB spacer.



    More quality time with a dremel to modify the PAS sensor for the front motor. On the right is a stock piece. On the left is what you need to end up with, as a Lekkie Buzz Bar on a BBSHD gives zero clearance to mount the disc on the spindle. You have to put it on the buzz bar itself.



    Backing the PAS disc is some strips of gorilla tape to provide a somewhat soft backing. Later I added a zip tie to ensure the tape stayed down. Note this pic also shows the right side spacers necessary to mount the motor. I used a 120mm BBSHD when I discovered the 100mm motor I bought wouldn’t clear these 5”-tire-compatible chainstays. Luna exchanged it for me. On this side I used a 10mm steel spacer I found on AliExpress that turned out to be a very precisely-measured piece. I had planned on paying McMaster-Carr for some custom-cut sleeve bearings at $40 a pop but these worked perfectly for $10. I needed another 2mm Wheelsmith cassette spacer on this side. I also needed to use two inner lockrings instead of the usual inner/outer so the second outer could clamp down on the PAS sensor unit. The 12mm of spacers I used plus the two lockrings gave me full thread engagement on the axle, and were measured out to hold the PAS disc and sensor at a precise position. You can see there’s no wiggle room.






    Doing the spacers like this had the secondary benefit of - after the offset Buzz Bar was in the picture - of putting the pedals just about 2.5mm off dead center from the chainstays. I got the pedals to 1.6mm from centered by using two pedal washers on one side and just one on the other to back the pedals.

    The KMC X9e chain has something like 136 links. Couple that to a long cage derailleur (I used a Shimano RD-M591) and you can wrap all that chain so you can get a proper length at any gear. I sized this chain in my usual way: Do the highest gear (smallest cog) so it just clears without touching the derailleur or itself, and the largest cog is what it is and will take care of itself … Its a fail if you do it wrong on the little cog and just inefficient if you stretch the cage a little on the big one. In this case, the high gear wraps just enough and the low gear is perfect… the top pulley is just forward of the bottom one.

    EDIT: This chain was sized for a 12T high gear but I subbed in one with an 11T to try out. As such the chain is just a bit too long on the high gear. I took out two links later on after I rode the bike in the rain and it skipped a bit in the wet under load. Removing the two links solved the problem.







    The resulting chain line from the spacing didn’t need any messing with. Going as close to the stay as I did with the Bling Ring worked out perfectly. Chain is pretty much dead on straight on the middle cog. On both the biggest and smallest cog, I can pedal as fast or as slowly as I want without issues. So… 9 usable gears. I actually wind up using the 11-tooth cog as my go-to on flat ground and its something like a 110-inch gear. Huge but perfect for ebike speeds.

    I have found that with use, AWD greatly reduces drivetrain punishment. Unlike my gen1 that can power slide the front wheel at will, I am looking for the front motor here to engage more gently and help stop a lot of the abuse a mid drive heaps upon that drive train. For example I blip the front throttle for a full second when starting from a stop. That will pump a slow-roll of power to the front wheel that peaks at 1600 watts about 20 feet along. As soon as I start rolling I start pedaling, and the BBSHD engages its PAS, which is also on a gentle start. Net result is a take-off much faster than a BBSHD alone, but with no shock to the drivetrain. If at an intersection, I am off the front throttle before I get to the other side of the street and am pedaling at maybe 15 mph and accelerating, with dual PAS and no throttle providing all of my power. Doing this, on flat land I have no need to downshift when coming to a stop. The front motor gives enough boost that I don’t have any issue staying in high gear, just like when I was riding a rear hub motor.

    So, given the above, an 11T cog is not just useful, so far after about 300 miles of riding this bike its become the preferred gear. That wouldn’t be possible without a front motor.
    Last edited by MoneyPit; 04-02-2018, 02:25 PM.

    #2
    Wow! That is an awesome and well thought out build. I love the detail you put into the write up. It seems you’ve overcome many of the downfalls of each particular drive type by using them in tandem-very smart! I bet that’s a killer bike to ride. (Isn’t Calfee20 trying to do something similar with a hub bmotor and BBSHD?)

    Comment


      #3
      Calfee20 will have to speak for himself but last I saw he was working on a Luna Rhino cargo frame. I didn't catch that he was going AWD with it.

      It is a killer bike to ride. The Ursa Major frame is advertised as having extremely short chainstays to put the rider square over the pedals for honking on them in snow. Not much of a benefit on an ebike but it puts the rear tire REAL close to the seat tube if you let it (sliding dropouts) and I did...

      The short wheelbase makes for an amazing change in cornering ability. I'm used to a powered fat bike being a freight train. First 90-degree street corner I tried to take aggressively at speed, I did my normal thing and found myself heading straight for the curb *before* the corner, it turned so sharply. Means I can turn thru intersections and can more easily stay full right rather than needing to briefly merge into the lane. Much safer. The downside of this wonderfulness is if I hit a pothole or similar the bike is a real handful to control. No free lunches in this world. The Jones SG bars make for a lot of options on handholds and they and the extra chunky ESI silicone grips are a definite asset. For $70 I may grab another set for my other fast fat bike.

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        #4
        That is the most amazing bike I may have ever seen. Thanks for sharing. I learned a lot just reading the paragraph above about how it handles. Beautiful bike!

        Comment


          #5
          Now about 550 miles into the bike - its not getting a lot of use as I have my 2-hub AWD for my main commuter. I am still leaving the bike mostly in the high 11T gear and using the front motor to get me off the line.

          Holding a magnifying glass and laying down next to the rear cluster, I can't see any wear on the 11T cog yet. I've heard stories of others who say their 11T cogs don't last for more than 500 miles and I'm past that and looking new still.

          I am trying to train myself to downshift at intersections. the last two cogs are press-ons and you have to get 3 in to get to one welded together with the rest. Trying to get on that cog for a stop. But the bike just doesn't need it. All I *need* to do is hit the front throttle and start pedaling.

          As much as I like riding the 2-hub AWD bike (its a rocket off the line) this is too nice of a bike not to pour miles onto so I'm trying to work it into my daily routine.

          Comment


            #6
            Originally posted by MoneyPit View Post
            Now about 550 miles into the bike - its not getting a lot of use as I have my 2-hub AWD for my main commuter. I am still leaving the bike mostly in the high 11T gear and using the front motor to get me off the line.

            Holding a magnifying glass and laying down next to the rear cluster, I can't see any wear on the 11T cog yet. I've heard stories of others who say their 11T cogs don't last for more than 500 miles and I'm past that and looking new still.

            I am trying to train myself to downshift at intersections. the last two cogs are press-ons and you have to get 3 in to get to one welded together with the rest. Trying to get on that cog for a stop. But the bike just doesn't need it. All I *need* to do is hit the front throttle and start pedaling.

            As much as I like riding the 2-hub AWD bike (its a rocket off the line) this is too nice of a bike not to pour miles onto so I'm trying to work it into my daily routine.
            My first bike has a S-A CS-RF3 hybrid drive with a close ratio 12-25 rear cassette and a 42 tooth Luna Eclipse. The 15 tooth rear sprocket gets 90% of the use. I just leave it there and use the 3 speed.

            I switched from an 11-34 freewheel to a 13-28 with a 52 tooth chain wheel on my hub bike to get away from that 11 tooth sprocket. I have also found myself leaving the bike in high and taking off with the throttle on this hub bike. When I finally get my Luna Cargo going it will start life as a single speed and I will use it this way.

            Great bike BTW!! I did see this thread but I must have planned to come back and read it and then forgot...........sucks getting old

            Comment


              #7
              On throttle, BBSHD only, I get the same top speed on the 11T as I do the 13T cog... but the 13T gets to top speed a little faster. The 15T is only about 2 mph slower. these BBSHD's really do prefer to just spin fast vs. lugging. However, riding on pedal assist, I need that 11T to keep up and be able to push on the pedals and mean it. Riding home on it today I was able to move at a pretty consistent 27 mph with a decent headwind.

              By contrast my hub bike, when it had a 60Tx16T single speed, let me cruise at a good cadence up to around 32 mph. I had to drop down to a 55 though when I cracked the frame and its replacement didn't give me the same chainring clearance/alignment to pull off the 60T in front again.

              Haven't had a chance to play with any IGH's... yet :D. I am actually building a fairly simple BBSHD 'lightweight fattie' with an unloved Motobecane Lurch frame I scored for a song and had stripped/powdercoated to look like new. So far planning on doing the identical 9-spd rear as I did on this one. Except 12-36 cluster. This bike is expected to live in hills so no need for any 11T or even 12 or 14T.

              Comment


                #8
                I see a Roholf in your future.

                Comment


                  #9
                  Following. PAS

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