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High power fat tire commuter ebike build thread

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    High power fat tire commuter ebike build thread

    I am underway in building two more matching fat tire commuter ebikes for myself. In preparation for this build, I built two prototypes which was a good thing because I found many things that needed to be improved upon:

    (1) I needed more copper in my motor because the 40mm rear hub motor would heat to 108 degrees C after 6 miles,
    (2) my 160mm rotor mechanical disc brakes did not provide enough stopping power for the 340 lb (bike + rider + cargo) load,
    (3) the 46T chain ring (in conjunction with an 11T small cog in freewheel) was useless after 31 mph with 30.5" diameter tires,
    (4) the rear hub motor axle of the Crystalyte 4060 motor was 2mm too short for the 170mm dropout frame,
    (5) the 150mm dropouts in the rear hub motor did not match the 170mm dropouts in the frame (I needed to use 1/2" washers & nuts as spacers),
    (6) the adjustable stem was a major safety hazard,
    (7) the 50A BMS was not able to deliver the current that I needed, and
    (8) I needed to create a thick Kevlar tire liner to avoid flats in these thin walled tires.

    Here is a YouTube video of one of the prototypes.

    My new bikes have Cromotors with custom wide axles (190mm dropout (shoulder), 268mm length) seen here:
    Click image for larger version

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    built into a 36h Surly Rolling Darryl using a 2 cross pattern and 13ga spokes as such:
    Click image for larger version

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    The frame is a 190mm dropout Design Logic Da Phat cargo frame built around a Vee Snowshoe 2XL:
    Click image for larger version

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    I am using Tektro Dorado hydraulic brakes with 203mm rotors, a CA V3, half twist throttle, multifunction switch (power on/off switch, regen, 3 speeds), a Lyen Mark 2 24 FET 4110 controller at 72V and 20Ah LiMn battery with a 100A BMS and 90A circuit breaker (on each 36V battery in series).

    The tires are the 2XLs as mentioned above on a Surly Clownshoe (100mm aluminum, 32h, 14ga spokes) in a Surly Ice Cream Truck fork in front and 36h Rolling Darryl in the rear.

    Drivetrain is a Surly Mr. Whirly crankset (Moonlander spindle) with a 58/110mm Surly spider, 175mm Surly crank arms and a single Vuelta USA 110BCD 58T chainring going back to a Sunrace 5-speed 14-28T freewheel.

    This part about the torque arms has been updated:
    One of the most fun aspects of the project is making the torque arms. I had a machine shop make some 1/4" 303 SS plates with a D-hole that matches the huge Cromotor axle. I will powder coat these torque arms and drill two holes that bolt the TA to the frame. The torque arm will hold the axle (and wheel!) securely in place as well as prevent axle rotation.
    Last edited by commuter ebikes; 04-13-2016, 08:14 PM.

    #2
    I have been collecting parts for six months and I still have a few more parts to buy, but I was happy to see that the rear wheel and motor fit in the frame:
    Click image for larger version

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    The Cromotor axle and its dropout shoulder were the right width and length, but I was horrified when I saw that the Cromotor axle flat was 10.8mm wide and the frame was built for an axle with 10mm flats. So I had to file my freshly powder coated frame a bit. Worse yet, the Cromotor axle is a whopping 15mm thick for my bike frame designed to accept axles no greater than 13mm. So I broke out the round file--tough way to start a project.

    Thank Goodness that my TA acts as a backup for holding the rear wheel on because removing metal from dropouts is a terrible idea. I filed it to a tight fit, but I shudder at the thought of the metal I removed. Scary stuff.

    Here is a picture taken halfway through the filing job from Hell: Click image for larger version

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    Last edited by commuter ebikes; 02-19-2016, 03:33 AM.

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      #3
      I love building bikes, But I Love riding them even more. When I look at these pictures I want to through this bike togather in one hour and ride it. I love a bike you can ride on the Bike Paths the Boardwalk and the Sidewalks along with the streets.

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        #4
        I just received my brake rotors and now I have to order a custom brake rotor spacer. Zelena Vozila offered to make these for free: Click image for larger version

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        I tried to use a 6-speed freewheel, but it was too tall: Click image for larger version

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        I could have put some axle spacers in there, but I will be be building four bikes like this, and I want all of the drivetrains to be identical. My first two bikes have 170mm dropouts--a 6-speed freewheel is never going to fit in that.
        Last edited by commuter ebikes; 04-13-2016, 08:19 PM.

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          #5
          Originally posted by Jack Miller View Post
          I love building bikes, But I Love riding them even more. When I look at these pictures I want to through this bike togather in one hour and ride it. I love a bike you can ride on the Bike Paths the Boardwalk and the Sidewalks along with the streets.
          I purposely don't own a car so that I have to ride my bike. Riding my bike is always the best part of my day. If I have a stressful day at work, I don't even remember the stress after a 15 minute commute. Riding a bike is a blissful combination of freedom and joy.

          With bicycle commuting, if the traffic is any kind of problem you can just get on the sidewalk or cut through a shopping center or park. It is like being immune to congestion!
          Last edited by commuter ebikes; 02-19-2016, 01:32 AM.

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            #6
            Here is a fun recent video of a high side crash: https://www.youtube.com/watch?v=RaoMVw8wVb0

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              #7
              Hope it didn't land on top of you, that's gotta be heavy!

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                #8
                Gee,

                I'd undoubtedly want to get at least one nice stainless steel torque arm at that rear dropout. I mean, the frame looks pretty stout, but its dropouts were probably never intended for a powered hub. Is the raised looking portion actually that much thicker than the rest? Otherwise, there's such a short slot, that the torque force could eventually widen the opening and possibly result in the axle spinning out.
                Last edited by Christian Livingstone; 02-22-2016, 08:28 AM.

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                  #9
                  Here's a pic of nice ones.

                  Click image for larger version

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                    #10
                    Originally posted by Christian Livingstone View Post
                    Gee,

                    I'd undoubtedly want to get at least one nice stainless steel torque arm at that rear dropout. I mean, the frame looks pretty stout, but its dropouts were probably never intended for a powered hub. Is the raised looking portion actually that much thicker than the rest? Otherwise, there's such a short slot, that the torque force could eventually widen the opening and possibly result in the axle spinning out.
                    On my prototype bikes, I used Grin Tech Torque V4 Arms which are 1/4" SS. I welded about 3/8" of hot rolled steel onto the chainstay end for a perfect fit. I then welded the torque arm at the proper angle and provided (redundant) clamping with a fine thread 1/4" Grade 8 bolt. Finally, I secured the TA at the chainstay with about 11 (!) medium cable ties which secured it very tightly. I like the Grin Tech TA (it is very similar to the one you posted a picture of) because it will hold the axle on even if both the axle nuts come off!
                    Click image for larger version

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                    I have been running this setup on my prototypes for about a year, and the only problem is I have to tighten the axle nut (particularly on the freewheel side) periodically because the regen and motor power loosen the axle nut every few hundred miles--this is part of my weekend maintenance.

                    On the bikes I am building now, I am using a custom torque plate.
                    Last edited by commuter ebikes; 04-13-2016, 08:22 PM.

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                      #11
                      Originally posted by paxtana View Post
                      Hope it didn't land on top of you, that's gotta be heavy!
                      The bike weighs 75 lbs. It did not land on top of me, but I landed on a tree and hyperextended my shoulder a little. I am fine just taking ibuprofen. It was fun! I am not sure if Alan B. will ever mount his GoPro on my bike again because I lost his mounting screw in the poison oak. I crashed on each of the last two rides we took together. This is the other (off camera) crash: https://www.youtube.com/watch?v=ml8DdrczxbE.
                      Last edited by commuter ebikes; 02-22-2016, 08:46 PM.

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                        #12
                        Somehow I always seem to have the camera pointed the wrong way when Erik crashes.
                        Alan B

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                          #13
                          Originally posted by Alan B View Post
                          Somehow I always seem to have the camera pointed the wrong way when Erik crashes.
                          Fortunately, you will have many more opportunities as I can't seem to keep the rubber side down.

                          I got a flat tire on the way home tonight so this weekend I will build the 7+ layer Kevlar tire liner--I will make a video.
                          Last edited by commuter ebikes; 02-25-2016, 12:06 AM.

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                            #14
                            I am trying to finish this project, but the spider I want to use is backordered until April. By the time the spider comes, I will have all of the parts and I will have had time to execute my large number of tasks.

                            This project has been punishingly expensive, so I guess it is good that it will have taken 9+ months.

                            Click image for larger version

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                              #15
                              I am finally getting my second frame back from the powder coater (along with both forks) so I have plenty of tasks on my to do list.

                              I scheduled a week of vacation to spend the whole week executing the 7 items on my list.

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