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Luna 42T Aluminum chainring to 52T chainring

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    Luna 42T Aluminum chainring to 52T chainring

    Using the Luna 42T aluminum chainring as an adapter for another size chainring. Any 130MM BCD chainring will work. If the 42T Luna aluminum ​is a good chainline here's the budget version conversion.
    I used an Origin8 52T

    Click image for larger version

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    UPDATE now you can use the LUNA Spyder it's 130 BDC too and looks bada$$, get it here Click image for larger version

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    Last edited by Sebz; 10-12-2016, 05:44 PM.

    Awesome! The off-road guys like smaller chainrings, because they need to keep the motor RPM's up at lower ground-speeds on an uphill grind. The street BBSHD riders (like me) like to have the option of pedaling at higher speeds, so that means a larger chainring. I just looked at this adapter on the Luna sirte, which has images from lots of angles. Its actually thicker material than I at first thought...

    Also, if you have a small chainring on the front, then the sprocket on the back needs to be VERY small, and that means a low tooth-count engagement on the rear sprocket. When using a higher-powered mid drive, you need a lots of teeth engaged. If you take the smallest sprocket on the back up from an 11T to a 14T (5 teeth engaged with the chain, up to 7 teeth), then you have a 40% better chain contact with the sprocket. However, in order to do that, you also have to have a larger chainring to maintain the same ratio. A 44T chainring to an 11T cog is a 4:1 ratio. In order to maintain that, a 14T cog needs a 48T chainring. And...for higher speeds, the 52T shown is great for the street at higher speeds (I am hitting 30-MPH all the time)
    Last edited by spinningmagnets; 06-18-2016, 04:09 PM.


    • Louis
      Louis commented
      Editing a comment
      I guess for giggles I should see what the 52T delivers.


    I've become a big fan of my 11-42 rear cassette. That granny gear gets back much of the low end lost to a larger chainring, yet with more teeth engaged for the same ratios. I never need to use the smallest rear sprockets, but sometimes do at light loads just to drop the cadence.

    For about $40, a wide range cassette can really complement a chainring size increase.
    Fabrication is fun! Build something today. Show someone. Let them help. Inspire and share. Spread the desire.


    • Eric Luna
      Eric Luna commented
      Editing a comment
      really great point......

    Se for sale section for the chainring, Cali eBike adapter, and Ridea chainring bolts.


      If only I had read this sooner! Just ordered a 44T narrow-wide chain ring to use with a 110bcd adaptor. With an 11T my top speed will be 23 mph or so which is useful on local street with 25-30 mph posted speeds. The adaptor isn't dished in like my Leike or the solution noted above. We will see whether the chain stays on consistently. Here's hoping.


        me 2. The 110 bcd with 52 tooth and 38 combo is really bad chain line. Snapped a new chain. The 130 gets past the motor housing. I like the 52 because it gets me out of smalker cogs. Most of my driving is commute so efficiency is enhanced with 52 ring. Better range at higher speeds.
        I am leaving a question here. I am using a bbs02, the taller gears give me a better cadence where i can actually be effective in adding power at higher speeds. The bbshd runs at higher rpms and a cadence that is ineffective? Is this true?


          In other wordd is the torque supplied at. Normal cadence 70 to 90 rpm, much higher with the bbshd compared to the02?


          • Rodney64
            Rodney64 commented
            Editing a comment
            The HD cadence is around 110 to 120 depending on the current voltage that the battery is at.

          Sorry but i am just learning. My real question is at what cadence do these motors put out maximum power. According to information i have now, a perfect pmdc motor puts out its maximum power at half its rated rpm. In order to shift maximizing power that would mean a cadence of 60 would be peak on the bbs02. So shifting to a higher gear at say 70 would be most effective in using maximum power range???? Efficiency is a different story.
          Are my assumptions correct? Or should this be based on no load maximum rpm? My feel in driving says the 70 is correct.


          • calfee20
            calfee20 commented
            Editing a comment
            You are going to get a lot of different answers to your question. Unfortunately what is needed is an individual doing a scientific study on a set course and that has not happened. The answers you get will be based on opinion from multiple people on different bikes in different places and terrains.

          Thank you for response.. I should soon have dual drive finished. Batt man.. Cadence sensor. Flat windless good little traveled road. Then crude testing. Still trying to understand my own question.
          So far charts on bicycle efficiency, cadence to mph and gearing, torque power and efficiency to motor rpm have all proved helpful.

          A lot of variables. Only one missing is power of the bafang motor to cadence. i think at higher end of rpm on the bbs02 the power deteriorates . Just where and how much is question. Thinking a plotting a graph by
          ​​​​​​ putting bafang on dynomometer might be next step in isolation of variables.

          Or just get this gearing right so a strong bicyclist with his 500 wat/s and the bafang peak of 1350 bbs02 pushes 43 to 45 mph. That is my thought on max. Theoretical speed. Normal 26 inch mtb in aero riding position racing tires.
          Sorry but it is raining again. Cant ride....
          Last edited by Gr8fun; 02-06-2017, 03:51 PM. Reason: Clarify


            Easy. Batt man log will show when decay happens.
            ​​​​ should give me all information on each gear.

            Raining hard and to dark to start.