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Thread: Best Gearing for your bike.

              
   
   
  1. #1
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    Best Gearing for your bike.

    I am in the design stage of building a bike. I am trying to figure out what the gear ratio will be, for it will have a big impact on the design. Is it best to run a jackshaft to do a gear reduction before running the chain back to the back wheel. I am looking to using the AC20 with it up to 164 vdc pack. Bike weight is little over 400 lbs. This is a street bike in a hilly area. Emphasis is on acceleration not top speed for we are only going on the highway and not looking to go over 85-90 mph. Usually cruse at 75 mph. I looked at tons of articles and post and found lots of different answers. It seems like if you could use a 6:1 ratio that would be best, but most people don't go over 5:1 just because of front to rear sprocket ratio. Going with a jackshaft adds lots of other issues and cost. The direct drive is easier and cheaper but would it be worth the extra cost and designing to use the jackshaft to be able to get the higher ratio? What are peoples thoughts?

  2. #2
    Senior Member Ted Dillard's Avatar
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    Start here: https://www.compgoparts.com/sprocket-calculator

    The guys I know who've run the AC20s are running as small a sprocket as they can in the front, and about as big as possible/reasonable in the rear, but I can't tell you the exact ratio.
    Power in Flux: The History of Electric Motorcycles
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    Senior Member Stevo's Avatar
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    I just completed my build with the Motenergy ME1616 and only running it at ~100 volts full pack. It's a dirtbike conversion, not a street bike. I ran it at a 4.13 reduction and a 4.42 reduction by dropping one tooth on the drive sprocket. At 4.13 it had ok acceleration with a nice throttle feel down low for technical trail riding and a top speed of 78 mph. At 4.42 it had fun acceleration and a top speed of 84mph and could break the rear tire loose with the twist of the throttle in the dirt, maybe too easily. Lots of torque!
    My bike weighs in at 401 lbs, so similar to yours. It's as close to OEM as possible with direct chain drive. Top speed could be increased with a higher voltage pack... hopefully in a few years with my next battery pack.

    I haven't built one with a jackshaft, so I cant add any info here for that concept. Maybe Electroflyer can help you with that. I think its the best way to go if you plan on switching to belts instead of chain. It also addresses some geometry issues in regards to swingarm pivot and drive sprocket locations.

    Please start a build thread so we can watch your progress! With lots of pics!!
    Last edited by Stevo; 3 Weeks Ago at 0904.
    Current rides: '96 Honda Ohlins VFR, '03 Cannondale C440R, '03 Cannondale Cannibal, '06 Yamaha 450 Wolverine 4x4
    Current builds: WORX.VOR.v3.2

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    Senior Member Ted Dillard's Avatar
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    No sweat, Sarah. We like to keep the bots happy too...
    Power in Flux: The History of Electric Motorcycles
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    Thanks for the advise. I think I will go with the jackshaft to give me the freedom to test different gearing.

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    Senior Member Stevo's Avatar
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    It's a toss up in expense... Designing and welding the jackshaft set-up wont be an easy feat. On the other hand, Using chain means you will need to buy several chains to get the testing done. I used one chain with 2 masterlinks to experiment with different ratios to try and feel what works. Not a great idea as the chain snapped on one test ride (one of the master links failed). But it gave me a real world feel for how the ratio changes make the bike behave. I learned that for street apps, 4.4 ratio and higher will give you fantastic acceleration, 4.3 and lower will reduce the tendency for the rear wheel to break loose in the dirt (at 400 lbs)
    Last edited by Stevo; 3 Weeks Ago at 1050.
    Current rides: '96 Honda Ohlins VFR, '03 Cannondale C440R, '03 Cannondale Cannibal, '06 Yamaha 450 Wolverine 4x4
    Current builds: WORX.VOR.v3.2

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    I looked at your pictures of your bike Stevo. Cool. What is the motor that you are using?

  10. #8
    Senior Member Stevo's Avatar
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    Quote Originally Posted by Ted Dillard View Post
    No sweat, Sarah. We like to keep the bots happy too...
    It's so friggin hilarious when the mod removes a thread and it appears that Crazy Ted is rambling on again about some imaginary woman named Sarah!! LMAO

    Ted, are you talking to Sarah about sexbots??!! That is gonna be the next big craze! I cant wait to order mine!!!
    Last edited by Stevo; 3 Weeks Ago at 1047.
    Current rides: '96 Honda Ohlins VFR, '03 Cannondale C440R, '03 Cannondale Cannibal, '06 Yamaha 450 Wolverine 4x4
    Current builds: WORX.VOR.v3.2

  11. #9
    Senior Member Ted Dillard's Avatar
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    Some day I'll tell you the story of what my wife thought I was building in the basement...
    Power in Flux: The History of Electric Motorcycles
    www.powerinflux.com

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