Shortbow

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

  1. tjwilson

    tjwilson Pro Member

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    I read some of the troubles you had with the brakes on Sting Rat. Sounded like fun ;)

    I ended up getting what was called a Shimano "J-kit". The calipers and levers come pre bled and the hose is only attached to the caliper. They offer it as a retrofit option for bikes with internal routing. Not sure if the hoses will be long enough but figured I'd start with as close to completely matched and ready to go components as possible to avoid trouble.
     
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  2. tjwilson

    tjwilson Pro Member

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    I did do a little looking around to try and find info on caliper orientation. Nothing indicated a problem with being upside down. And like you mention, I've seen front calipers that lean back pretty far. The only thing I did find was that brake *system* was not designed to operate upside down. This was from the Shimano manual. That seems to have to do with the caliper being positioned higher than the lever / fluid reservoir. Apparently any bubbles within the system can migrate from the reservoir to the caliper and cause issues. Might be the problem that @Chad T is having while moving his Sting Rat around?
     
  3. SpikeFC

    SpikeFC

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    Rule no. 1

    Don't trust all Shimano manuals :21: In one of their manuals it states that Nexus 3speed hubs should run with a cog set of 20-22 rear 38 front, mine is working 16 to 46, the same manual has a line about roller brakes not working with v-brake levers... mine are working fine :21:

    Rule no. 2

    Not operating upside down means that the lever can't be lower than the caliper, cause it's a gravitational system. Air bubbles always go up the line, and when the whole system is operated upside down they gather in the caliper instead of the lever (that actually has a small tank for the oil inside it). The working idea is 100% the same as in motorcycle brakes.

    Yes, you're right, that is the problem that @Chad T is having. I'm personally thinking that hydraulic brakes are very good for any build - even rat builds, you just need to remember to bleed them properly and make sure that you have not worn or greasy pads. That can lead to catastrophes.

    Since hydraulic brakes are used in almost every new bicycle, I have a lot to do with those systems, and from my experience - don't use cheap hydraulic kits, and avoid using other producers than Tektro, Magura & Shimano, cause replacement parts to other producers brakes (like Avid or Formula) may be super hard to find.
     
  4. tjwilson

    tjwilson Pro Member

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    Overview and Details with Seat Stays / Cantilever Tubes

    Page 5 needs some images...
    01_side.jpg

    02_rear3qtr.jpg

    03_frnt3qtr.jpg

    Finished up the filing of the canti-tube welds. Still need to get a bridge made up to connect the two sides.
    04_cantileverDetail.jpg

    Clearance around the chain stays, the chain and tire is tight. Looks workable but there may be some chain rub on the chain stays in tenth gear. Might call for a rub guard?
    05_clearanceDetail01.jpg

    06_clearanceDetail02.jpg
     
  5. OddJob

    OddJob

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    TJ, to take up some of the slack in your high gear, and maybe alleviate any chain rub, check the B screw on the back of the rear derailleur. If you turn it in (to the right, clockwise) about half way, it will tension the chain a bit more.

    This will also keep it from rubbing on the upper pulley wheel in first gear. So a double benefit.

    Most of the time, these derailleurs come with that B screw nearly all the way out. It really helps with a more crisp shifting between the cogs. I usually pull the der cage back towards me to take the spring load off the screw and then turn it in 5 or 6 rotations of my wrist.

    The other thing to do is keep the chain as short as possible, so it is the least slack it can be when in high gear.

    Here's a pretty good Youtube on the adjustment:
     
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  6. GuitarlCarl

    GuitarlCarl

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    Yep adjust that derailleur a bit
    and maybe a strategic dimple on the inside of the tube...
    :eek:
     
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  7. tjwilson

    tjwilson Pro Member

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    Awesome info, thanks. I saw the screw but had no idea what it adjusted or how it should be adjusted. The derailleur came out of the box with the screw about half way in. I shortened the chain according to the manual... chain around the front chainring and the largest rear sprocket (without derailleur) plus two links. These images are with that initial screw setting and after chain shortening. It was difficult to run through the gears because I didn't have the bike fixtured and it's not ready to ride but it seemed to shift fine. After watching the video I'm wondering if I've got the chain too short / tight?

    Tenth Gear
    01_tenth.jpg

    First Gear
    02_first.jpg
     
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  8. tjwilson

    tjwilson Pro Member

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    Those poor chain stays, in the gun sights again
     
  9. OddJob

    OddJob

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    TJ, since you don't have a front derailleur, that position in 1st gear is fine. Especially with that short cage der in the rear, you want a shorter chain when you are down in 10th / high gear. otherwise it will rub against the pulleys between the two.
     
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  10. tjwilson

    tjwilson Pro Member

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    Thanks for your help and input. Much appreciated and gives me confidence with this new to me hardware
     
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  11. Chad T

    Chad T

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    OJ knows his stuff. He's my secret weapon when I get into trouble.

    Chain clearance looks good. Will probably slap the stay while you're shifting. Does it clear the tire in first? That's the problem I always run into with a wide tire.
     
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  12. tjwilson

    tjwilson Pro Member

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    It clears but just barely. There might be a little rubbing of the bottom of the chain (return run from the cog to the chain ring) if there’s much movement side to side. Top seems good. Considering the speed I’d be traveling while using first, and how infrequent that will be, I don’t think it will be an issue. Easy to say now... a few test rides will prove if my assumption is true real fast.
     
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  13. tjwilson

    tjwilson Pro Member

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    Sissy Bar / Seat Support

    Not sure if they're called a sissy bar only if they're tall and seat support if they're short. Anyway, started with the bottom supports. These will eventually be cleaned up and polished.
    01_supports.jpg

    Fill with sand, tack weld, bend, cut free, rotate 90°, tack, bend again.
    02_bentTubes01.jpg

    03_bentTubes02.jpg

    Test fit. I did think briefly about leaving them long but ultimately decided against it.
    04_sissyTestFit.jpg

    I added the additional bends at the bottom of the tubes to keep the seat from getting too wide. The final seat width should be about the width of a typical banana seat.
    05_lowerBends.jpg

    Fairly certain this is NOT the recommended way to use a pipe bender.
    06_topCurve01.jpg

    I couldn't get the complete bend I wanted from a single piece of tubing. Took three pieces sleeved together to get the curve I wanted.
    07_topCurve02.jpg

    Support sides trimmed short and top curve dry fit.
    08_preWeld.jpg
     
  14. tjwilson

    tjwilson Pro Member

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    Rear Brake Revisited

    With the seat support in place I was able to take a closer look at the rear caliper mount. Using the 160mm disc there seems to be enough room to mount the caliper in a more "traditional" position. I'm just not sure about the hose routing. With the caliper upside down and flipped inside out the routing is really clean. I'm second guessing if that could actually be pulled off though. The bracket would have a lot of twist leverage.

    140mm Disc (Lack of) Clearance
    01_140mm01.jpg

    02_140mm02.jpg

    160mm Disc Clearance
    03_160mm01.jpg

    04_160mm02.jpg

    Hose Routing
    05_hoseRouting.jpg
     
  15. Scrap Wolf

    Scrap Wolf

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    It is such a joy to follow this build. First of all the fabrication skills are a lust for the eye. Second, all the work is so well documented in image and text. This takes a lot of time, I really appreciate it.


    Sent from my iPhone using Tapatalk Pro
     
  16. Chad T

    Chad T

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    Can't wait to see this with the nanner and apes.

    You could route the hose behind the wide section of the sissy and attach it to the seat stay to clean it up a bit. Should be able to bend the hose quite a bit so long as you don't kink it or pinch it shut.
     
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  17. tjwilson

    tjwilson Pro Member

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    That’s an awesome compliment, thank you very much.
     
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  18. tjwilson

    tjwilson Pro Member

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    I can’t either!

    Something you just said there flipped a switch to a dim little light in my head! These are hydraulic brakes. Aren’t automotive hydraulic brake systems made up of both flexible and hard lines? I wonder if they sell or, if it would be possible to make, hard lines that would connect to a bike hydraulic brake system. Even just an angled fitting attached to the caliper would completely change the hose routing. Something like a v-brake noodle.
     
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  19. MattiThundrrr

    MattiThundrrr

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    Steel braided lines would be MAD SICK!!:rockout:
     
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  20. kingfish254

    kingfish254 CHECK OUT MY SALE THREAD FOR COOL STUFF! Pro Member

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    WOW! What an absolutely mind blowing design. Your work is some of the best around. Love it man!
     
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