Shortbow

Discussion in 'BUILT FROM SCRATCH' started by tjwilson, Oct 15, 2019.

  1. tjwilson

    tjwilson Pro Member

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    01_shortbow_side.jpg

    02_shortbow_rearFrnt3qtr.jpg

    03_shortbowDIM.jpg

    This will be a scratch built frame and seat with handlebars pieced together from odds and ends of other bars.
     
  2. tjwilson

    tjwilson Pro Member

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    Tires and Rims

    I've wanted to use the 20x4 Vee Apache since I found out they made one. I have the tire and a polished 20x67mm rim on their way. Also in the mail is a 20x1.35 tire and polished rim for the front.

    04_frntRearTireRim.jpg
     
  3. tjwilson

    tjwilson Pro Member

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    Hubs and Drivetrain

    @Chad T , I hope you consider imitation as the sincerest form of flattery. I'm a huge fan of the way you've used modern components on your vintage muscle bike builds. They look like absolute screamers and a blast to ride. I'm hoping to heavily "borrow" some of your component selections. Problem is my drivetrain experience pretty much tops out somewhere around the mid nineteen seventies, at best.

    Here's what I think I need to get started. For context this bike will be used mostly as a city bike. Lots of stopping, quick starts across intersections, relatively short rides.

    - Origin8 FB-2000 Fat Bike Rear Hub (170mm OLD)
    - Shimano HB-M525A Deore Front Disc Hub (100mm OLD)
    - Origin8 100mm BBx164mm Spindle XLT Square Taper Bottom Bracket
    - Origin8 Alloy Crank Arm Set (110 BCD) 140mm crank arm length
    - J&L Narrow Wide Road/CX 1x ChainRing-110mm, 38t, 158mm DIA
    - Shimano Deore M6000 Series 10s Cassette, 11-25t
    - SRAM GX 10 Speed Trigger Shifter - Exact Actuation
    - SRAM GX 10 Speed Rear Derailleur - Exact Actuation (Short Cage?)

    I think I've done my homework and everything will work together and, makes sense. Hoping to put together smart choices that aren't going to break the bank. Any input would be greatly appreciated. @OddJob, anyone else?
     
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  4. tjwilson

    tjwilson Pro Member

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    Some Pretty Potential Parts Pics

    05_hubs.jpg

    06_bb.jpg

    07_gearing.jpg

    08_shifting.jpg
     
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  5. MattiThundrrr

    MattiThundrrr

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    Wooot! With a wheel that fat combined with a 10x cartridge, your chainline is gonna be waaay out there! I'm liking your ambition.
     
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  6. OddJob

    OddJob

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    The critical thing will be your chain line. The 170 hub width combined with your 164 BB axle width should do it. Not familiar with the rear tire, so I don't have much to compare with, but if it's less than 4.5" or so wide, you should be able to make it work.

    The short cage rear der will handle your reasonably tight 11-25 cog spacing, and make for snappier shifting.

    ** Edit** I just saw the 20 x 4 Vee Apache that should work fine for a good chain line.
    And, WOW is that CooL! :inlove:

    You might want to consider a larger chain ring, like maybe a 42 t, to get the benefit of that gear range. Otherwise it is going to be geared pretty low. And remember, you can always stand up and crank for short steep climbs.

    Speaking of cranks, I would also consider a longer crank arm length. 140 is fine for single speed 'kids leg length', but if you want to ride this beautiful build, I would go longer.

    Otherwise TJ, you definitely have my attention on this one! As always.... RaT oN~!
     
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  7. tjwilson

    tjwilson Pro Member

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    Thanks for the input!

    That Apache is just begging to be at the back of a muscle bike. Here's a cross section I got from Vee Tire. I'm using a rim that has the same bead width as shown so overall width should be just under 4".

    09_20X4-Apache-Fattyslick-with-RIM-66mm.jpg

    So this was my thinking on the chainring size and crank length. I've been riding the wheels off a stock Fastback all summer and just love the ride. I ended up finding cranks that matched the Fastback arm length. Then I figured the front chainring by working back from the rear cassette to find a close match to the ratio of the gears I usually ride in. Also, shorter cranks should reduce some of the toe clipping at the front tire (this build has a short wheelbase). And lastly, a smaller chainring would help me slip the chain-stays past the crank between the chainring and tire.

    BUT...

    You're saving me from painting myself into a corner. If I make the frame fit a larger chainring and crank I can always swap out to smaller ones later. If I start smaller I may not be able to fit the larger chainring and longer crank arms to the frame later on.

    PLUS...

    At 170mm this is a bit longer than I was originally thinking but I really like the look of this crankset. Guess I'll just have to watch my toes in tight turns!

    10_fsaGimondi130BCD170mm.jpg
     
  8. MattiThundrrr

    MattiThundrrr

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    That big heavy wheel will be a lot to spin. You may want an easier gear than your Fastback, as the same ratio will be more work. The Worksman trike I roll at work is a ton, but its lower gearing really works for accelerating.

    Edit: oops, I was thinking about another bike, forgot you are using 10x. You'll have plenty of gears!
     
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  9. Dr. Tankenstein

    Dr. Tankenstein

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    That Apache is gonna look MASSIVE, total drag strip look, love it!

    Sweet crankset too, god thinking of building the big to accommodate a larger chainring with the option of going smaller later

    Sent from my iPhone using Tapatalk
     
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  10. Psychographic

    Psychographic

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    Thar's going to be one slick looking ride. I bet it will turn on a dime too.
     
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  11. tjwilson

    tjwilson Pro Member

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    Thanks for looking out for me. Yup, not only heavier but it will be a little taller too.
     
  12. tjwilson

    tjwilson Pro Member

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    Es-Press-Oh!

    With past frame builds there are a couple of bends that I've always either designed around, struggled with, or used sections of donor frames for. Specifically the "S" shaped bends in the chain-stays and seat-stays. I have a hydraulic pipe bender that I thought might be able to be used as a mini-press if I made some sort of dies. So, while waiting for parts to arrive I came up with this.

    Die Pieces and Parts
    01_piecesParts.jpg

    Welded up
    02_version01.jpg

    Here's the dies in the hydraulic bender. The red line shows the bend of a test 3/4" piece of tubing.
    03_inPipeBender.jpg

    The first test bends weren't as smooth as I had hoped for.
    04_bendFirstPass.jpg

    05_3qtrInchFirstPass.jpg

    I modified the dies by adding a section of thicker tubing that had a larger radius.
    06_modified.jpg

    I also applied bearing grease to the dies for a second test. The thinking was that the grease would help the tube slide while being pressed and make for a smoother bend.
    07_bendSecondPass.jpg

    Not sure how much the grease helped but I'm much happier with the modified die results. Here is a comparison between the two. In these images the latest modified die test piece is shown on top.
    08_bendCompare01.jpg

    09_bendCompare02.jpg
     
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  13. MattiThundrrr

    MattiThundrrr

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    I don't know if this is an option where your press is, but @GuitarlCarl suggested filling tubes with sand or salt to prevent them from getting crushed. It supports the tube similar to a mandrel
     
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  14. GuitarlCarl

    GuitarlCarl

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    Sand is commonly used when bending freestyle with no mandrel. I use salt because it's easier to manipulate (pretty easy to pour down the tube from the container) and it's cheap.

    Where are the curved mandrels supplied with that bender,
    and why aren't you using them?

    Carl.
     
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  15. sdframe

    sdframe

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    We have some serious building going on here. Can't wait to see more.
     
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  16. tjwilson

    tjwilson Pro Member

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    I'm putting these tubes under a *big* squeeze. Believe it or not I did fill them with sand before bending! I'll be able to use some of the flattening and dimpling to me advantage for the chainstays... another *big* squeeze. I thought the first pass bends had just a little too much and wanted to try to tweak them a bit. I plan to use the same set-up for the seatstays / cantilever tubes. Those will be half inch. Hopefully between the die tweaks and smaller diameter tube there will be less flattening on those.
     
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  17. tjwilson

    tjwilson Pro Member

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    Never tried salt only sand. I have a small funnel that I use to fill the tubes. I've also switched from welding plugs into the ends to using duct tape for all bends. The heavy duty tape seems to work as well and is a lot faster.

    I've never been able to get a "good" bend using the hydraulic bender and the mandrels that came with it on thinner tubing. Thinner being .065", .049" wall verses 1/8" or so for black pipe. Even packed with sand the tubing dimples both at the high point of the mandrel and the top rollers.

    This is the roller I typically use for larger curves (image is from a previous build). It's a workout but you can control the curve by tightening or easing the roller tension to change the bend radius.

    tubingRoller.jpg
     
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  18. tjwilson

    tjwilson Pro Member

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    Drivetrain Back Pedal

    With parts in-hand I've been able to measure and create a dimensioned drawing of the chainline. I'll be printing this out at 100% and use it as reference when shaping the chainstays. Started out with a bottom bracket spindle width of 164mm. This gave me a lot of room but the chainline didn't look good. Even with the chainring mounted to the inside of the crank arm.

    01_164BBspindle.jpg

    I've got a 137.5mm spindle ordered. Makes for a tight pass with the chainstay but I think this will give me a more acceptable chainline.

    02_137dot5BBspindle.jpg
     
  19. Chad T

    Chad T

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    Totally honored to even be mentioned in connection to this. That looks like a killer selection. 10 speed is a great way to go. Not as expensive as 11 and better selection than 9.

    I like the idea of longer cranks with the gearing you have. You'd need a smaller front ring to make them little egg beaters fun. Can you raise the bb a bit to give you some more clearance?

    Sorry it took me so long to chime in...must have been a snag with the tag. Never got an alert. Looking cool..:thumbsup:...dig the wheel/tire selection too.
     
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  20. GuitarlCarl

    GuitarlCarl

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    Well my friend, I have used a tool to bend offsets in thinwall electrical conduit. We always called it a kickbender and it would bend a "kick" in a stub so that the conduit running along a wall would offset into an electrical box. Looks almost identical to what you were trying to bend they only cost 2 - 300 bucks...
    kickbender.jpg
    You could hand bend it with a conduit bender KOTA style, hand benders are cheap at 40-50 bucks, even cheaper at a pawn shop... But I think your tubing roller should be able to do that offset bend.
    I too use duct tape to plug and salt to fill...

    Hey I wonder if you could fab your die to include curved mandrel like sides made from pipe?

    Carl.
     
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