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  1. #1
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    Careby's Big Dummy Build

    I've been wanting a Big Dummy since the first time I saw one, and now the time has come for me to build one. I chose an 18" frame, which is one size smaller than I normally would ride, but since this will be a utility bike, there is a chance someone else may need to ride it.

    For drivetrain, I chose an Alfine 8-speed IGH with 18-tooth sprocket, and a 22/36 SLX double crankset. This will give me a high range of 28 to 85 gear inches, and a low range of 17 to 52. The low end should be plenty low, and I think I'll be okay with the top end. Front hub is an Alfine dynamo, and rims are 36-hole Salsa Gordos.

    I am still waiting on a few parts, but I have the wheels installed and it's starting to look like a bike. Next up will be the crankset and brakes. I chose Avid BB7 calipers and Shimano centerlock rotors, 203mm in rear and 180mm in front. (The picture shows a 160mm front rotor. but I have since decided to change it.)

    Seat will be a Brooks B67, and I'm still struggling with handlebar selection. Maybe Nitto Albatross, maybe Surly Open Bar, or maybe an H-bar. I'll have to see what feels right. I have Jtek bar end shifters and Shimano trigger shifters, but will have to pick the handlebar first.
    Attached Thumbnails Attached Thumbnails Careby's Big Dummy Build-careby-bd01.jpg  


  2. #2
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    Cant wait to see the rest

  3. #3
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    very cool

  4. #4
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    Drivetrain Installed - First Ride

    The drivetrain is in, and I took her for a short ride. Short, because with no shifters or cables the Alfine hub is in low gear, and it doesn't take long to get tired of low gear on flat ground. I have a front brake with temporary cable and lever, and used a short piece of cable to shift the front derailleur to the bigger ring. The results were as good as I hoped - definitely enough to keep me interested.

    I had some choices to make regarding the chainline. The Alfine hub is intended to have about a 42mm chainline. SInce most MTB cranksets have 50mm chainlines, most people flip the 3mm dished rear cog over to get about 48mm. There were three reasons why I didn't want to do that. The main one is that I wanted to use the Alfine tensioner, and it won't work with the cog flipped. It takes the maximum 5mm of spacers to get it to 42mm on a steel derailleur hanger. Second, the Alfine cogs have a plastic chain guard attached to the outside, so to flip it you have to tear that off, or use a Nexus cog which doesn't have a guard. And third, Shimano recommends using an Alfine cog with chainguard when using the hub with a front derailleur. So I decided to see if I could run it at 42mm, as designed. My main worries were the Big Dummy's long chain and wide tires. Would there be enough clearance between the chain and tire to prevent chain rub? On the plus side, the long chain means that a given offset between front and rear sprockets results in a relatively straighter chainline.

    The SLX M665 double crankset has a standard MTB chainline. Shimano specs say 46.8mm, but only because of the convention of measuring to halfway in between the chainrings. The 36t ring is at 50mm, just like the middle ring in a triple crankset. I decided to move one of the 2.5mm BB spacers from the right side to the left to slightly offset the crankset. That left me with a pretty near perfect chainline on the 22t ring and about 47.5mm on the 36t. If you compare that to the difference between inner and outer cogs on a 9-speed cassette - about 35mm - I think it's just fine. Time will tell if I have problems with the chain rubbing the tire. If so, I can always flip the cog and find a different tensioner. The photos show what the chainline looks like currently.
    Attached Thumbnails Attached Thumbnails Careby's Big Dummy Build-careby_bd_alfine.jpg  

    Careby's Big Dummy Build-careby_bd_chainlinerear.jpg  

    Careby's Big Dummy Build-careby_bd_chainlinefront.jpg  

    Careby's Big Dummy Build-careby_bd_rightchain.jpg  

    Careby's Big Dummy Build-careby_bd_leftside.jpg  


  5. #5
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    Looking forward to this build! So far you are approaching it almost exactly the way I am planning it in my head (while I save up).

    Great pics and wonderful detail in the posts - keep it up!

    Kook

  6. #6
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    The handlebar I ended up choosing is the Surly Open Bar, 40mm rise version. I've liked it on every bike I've put it on, especially with Ergon grips. I toyed with the idea of using bar end shifters but decided to go with standard Alfine trigger shifters instead. Cabled it all up and went for a ride. What a windy day!

    Edit: The reason the seat is so low in the pics is that the seatpost slipped in the clamp. When I stopped to fix it, I decided to snap a few iPhone pictures.
    Attached Thumbnails Attached Thumbnails Careby's Big Dummy Build-careby_bd11.jpg  

    Careby's Big Dummy Build-careby_bd12.jpg  

    Last edited by Careby; 04-11-2012 at 06:16 AM.

  7. #7
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    Congrats on the Dummy!

    That is one sweet build! Nice. I am definitely curious about how the Alfine plays out for you. I am currently running a 3x8 drive train on my Dummy and it works fine, but there is something about the simplicity of the IGH that has really gotten my attention, as of late.

    Looking forward to updates!

  8. #8
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    Xtracycle Parts Arrived

    I kind of liked it naked, but now the Xtracycle dues have been paid.
    Attached Thumbnails Attached Thumbnails Careby's Big Dummy Build-careby_bd13.jpg  

    Careby's Big Dummy Build-careby_bd14.jpg  

    Careby's Big Dummy Build-careby_bd15.jpg  

    Careby's Big Dummy Build-careby_bd16.jpg  


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