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Building lugged CX/touring bike

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Building lugged CX/touring bike

Old 07-13-18, 07:58 AM
  #26  
Nessism
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A couple of comments that may help...

I like to miter all the tubes as the first step, being sure there are only minimal gaps when the tubes are laid directly down on the pattern form.

When assembling I do as unterhausen says... "...bb/seat tube joint first. Then the hockey stick (head tube/down tube) then put the front triangle together."

For brazing, it's critical to concentrate the heat on the lug, not the tube. Get the entire lug hot, all around, then feed in the silver starting from a top point and then use gravity and heat to pull the molten silver through the lug. Don't be shy to add a good bit of brazing material. Rotate the frame as needed to use gravity and be sure the lug is filled. If you get a little build up on the lug edge you can pull that inside as the last step or even get some braided stainless mesh material to suck it away as I think Brian Bayless used to advocate.

Good fun
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Old 07-17-18, 09:06 PM
  #27  
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Thanks for your comments. Not sure I understand the braided SS mesh idea. I'm assuming you'd have to flux and heat the mesh, and then use it while it's hot to capillary the excess solder away from the joint and into the mesh?
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Old 07-17-18, 10:48 PM
  #28  
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Did another test lug, but with pinning this time. There's 3 pins per tube, spaced as evenly as possible around the circumference. Here the lug and tubes are pinned and fluxed ready for brazing.


Cooling down after brazing.


After a soak in warm water to remove the flux, and the pins trimmed down. The joint moved less than 1mm, 400mm out from the lug at the end of the TT.
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Old 07-19-18, 02:19 PM
  #29  
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See comment in photo below. It looks like more brazing filler is needed.



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Old 07-19-18, 05:03 PM
  #30  
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I see filler at the bottom of the lip. In particular, your bottom two arrows go right over some filler
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Old 07-21-18, 07:13 AM
  #31  
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Yeah there's a couple of spots where the gap between ST and lug-inside-lip are a little too large for the silver to fill. The lip inside the pressed lug is an irregular shape, and I didn't bother filing the top of the ST to match up with it. All the test lugs I've cut up show full silver penetration though.
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Old 07-22-18, 07:12 PM
  #32  
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Here the frame is all jigged up with shims and spacers, ready for drilling for tapered pins. The front end of the frame is only supported by the ends of the HT, to ensure its in line with the ST. I placed weights on top to help hold everything in place.


I've done 3 pins per tube-lug connection.


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Old 07-22-18, 07:19 PM
  #33  
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Made up a little tool for holding down the water bosses for brazing



BB and ST brazed together.


Can see that there's a good amount of silver in there.
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Old 07-22-18, 07:59 PM
  #34  
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After the ST, DT and HT where all brazed together, I slid some tight fitting steel pipe through the HT, to act as a wider measuring surface. I then laid the ST and HT pipe on 2 spacers each. By looking at which way the frame rocked back and forth, I was able to bend it into line. I also flipped the frame continuously to account for any unevenness in the MDF base.


This was the high tech straightening setup. BB in a leg vice with cardboard jaws, and just yank on the pipe through the HT. Check and repeat until straight.


I placed the TT vent hole low on the ST, so that any water/condensation that ends up in there can drain through to the BB and out.


Seat lug all brazed up.


Dissolving flux off in a bucket with a heating element.
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Old 07-22-18, 08:02 PM
  #35  
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Also thanks for all the suggestions, I did end up doing a variation of the hokey stick method. I did ST to BB, DT to BB, HT to DT, and finally TT to ST and HT.
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Old 07-25-18, 06:31 AM
  #36  
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Awesome work! Keep going!

Noticed you used rattleCAD. How did you like it? I'm getting ready to start a new project and was planning on giving it a try. I've always used pencil drawings in the past but I'm feeling lazy...
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Old 07-25-18, 10:18 AM
  #37  
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Just ran across this thread. Nice work!
Looks like your heat control is spot on.
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Old 07-25-18, 02:37 PM
  #38  
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Originally Posted by Nessism View Post
Awesome work! Keep going!

Noticed you used rattleCAD. How did you like it? I'm getting ready to start a new project and was planning on giving it a try. I've always used pencil drawings in the past but I'm feeling lazy...
I have doodled with rattlecad, but since I have BikeCad pro, I have never bothered to design a frame with rattlecad. Of course, they do things their own idiosyncratic way. But even if you were going to eventually make full-size paper drawings, fiddling with the design on cad first is a great idea.
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Old 07-25-18, 11:11 PM
  #39  
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Originally Posted by unterhausen View Post
I have doodled with rattlecad, but since I have BikeCad pro, I have never bothered to design a frame with rattlecad. Of course, they do things their own idiosyncratic way. But even if you were going to eventually make full-size paper drawings, fiddling with the design on cad first is a great idea.
I'm a rattleCAD user and it does everything I need it to do. I have started doing full size printouts for the chainstays now that i'm using curved stays and tighter tolerances between rings and discs and the stays with wider tires. It's difficult to know how the angles, radii and length will end up in the software so, I enter them to the software as best I can, then I print out using Poster on 11x17 sized paper and then tape it all together to get full size drawing. This is probably printer dependent but, even if you had to do it on regular letter sized paper it should work. Fiddly, but it works. I lay my fixture right over the top and use 1-2-3 blocks to line everything up before mitering and brazing.

After doing this, I circle back around to reconcile the results with what I input to the software so the next one will be dimensioned more reliable/accurate.


Untitled by Duane Draper, on Flickr
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Old 07-26-18, 04:32 AM
  #40  
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so that drawing is generated by rattleCAD? Maybe I'll have to start using it.

Neat fixture, I am planning on building something similar so I can get rear dropouts brazed on more accurately.
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Old 07-26-18, 03:12 PM
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Originally Posted by unterhausen View Post
so that drawing is generated by rattleCAD? Maybe I'll have to start using it..
Yep, as I allude to, the user can manipulate the bend of the stays using the crosses that are seen just above where the fixture is sitting. you can drag them to lengthen the sections and so on. User can also simply double click and enter measurements. It's a bit fiddly and I find translating real world into the software a bit of a challenge. I enter measurements as close as I can for the chainstays and then measure the cranks, disc, chainrings and tire to enter those parameters. I print it out and then lay this fixture over the top and make sure the tubes clear the tire, disc, chainrings, etc.

Originally Posted by unterhausen View Post
Neat fixture, I am planning on building something similar so I can get rear dropouts brazed on more accurately.
I have another one that is a bit more compact so it fits into my mill (small vertical knee type) with it's limited Z travel. Those tube blocks are the ones that Alex Meade just came out with and they are great. I was using v-blocks before and those weren't as nice or secure.
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Old 07-26-18, 05:47 PM
  #42  
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I found rattlecad pretty simple to use. Takes a little while to figure out which measurements and angles take priority when you change something, also the default for the DT and ST are tapered for some reason IRC. Once I was ready to start, I got the frame plan printed 1:1 on an A0 page, made everything much easier being able to measure directly, and also visually being able to check angles.
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Old 07-30-18, 07:19 PM
  #43  
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Main triangle almost finished up


Made a rear dummy axle out of 3 diameters of tube that fitted nicely inside each other, some 10mm all thread, nuts and washers. I drilled holes in the tubes and plug welded them to each other, then cut to length and squared off the ends on a disc sander.


Completed dummy axle, and some silver rings that I press fit into the ends of the CS before fluxing and fitting up for brazing.


Jigged up with some SHS to keep the dropouts parralel and in phase with the ovoid CS's.


Block of wood I carved out to support the CS's while dimpling. I used a 30mm long piece of 12mm round as the indenting tool, and rounded off both ends. I used a bench vice to do the squishing.


Using the frame as a reference to align the wheel, which in turn, then held the CS's in the correct position. I was only really worried about the axis that the CS's dictate. The axis that the SS's dictate can be tweaked later.


3 pins per CS seemed to hold everything quite nicely.

Last edited by Saul KK; 07-30-18 at 07:22 PM.
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Old 07-31-18, 07:20 PM
  #44  
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Brazing CS's into BB


Brazed up and cooling off


Checking alignment against the SHS. Note the 2 pieces of steel clamped either end of the SHS to keep it square to itself.


Checking the dropouts are centred to the frame. Made sure to flip the frame over and check again, as the CS's sag somewhat under their own weight.


Checking for the correct angle between ST and CS's


Didnt get any photos, but prior to brazing the seat stays in, I had shaped and brazed the end plugs into the tops. Here they are ready to be brazed into the drop out sockets.


Seat cluster pinned, fluxed, and ready for brazing.


Main frame pretty much complete after soaking off the flux and a quick scotchbrite. Still have a whole lot of filing, sanding and clean up to do, as well as adding all the little braze ons, cantilever bosses, and bridges.

Last edited by Saul KK; 07-31-18 at 07:23 PM.
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Old 07-31-18, 10:32 PM
  #45  
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I'm about ready to make a jig for lining up and holding the cantilever bosses in place while brazing, and I'm having a hard time trying to figure out the exact location I need. I plan on using tektro CR720 cantilever brakes, and 700c rims. It seems I need 283mm from centre of wheel axle to centre of cantilever bosses, and 70-80mm between cantilever boss centres? Can anyone please clarify this for me? Thanks
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Old 08-01-18, 06:00 AM
  #46  
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I always have to look up those numbers. Since the spacing was established, rims have grown 5mm wider, so you want to be at 80-85mm. I would also just put a wheel in and look at the way the brake shoe falls on the rim as a sanity check. Note that the Tektro brakes have really long slots. You want the brake shoe to be close to the pivot in order to get the most mechanical advantage. If you have them at the other end of the slot, they don't work that well. And also, Paul brakes will not fit because their slots are short.

My first canti fixture was a flat plate with a couple of holes in it. That was back before there were standard distances, I just figured out where they would hit the wheel most conveniently and brazed them there. Wonder how that matches up to the standard numbers.
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Old 08-01-18, 08:44 AM
  #47  
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I would always check any published location numbers by mocking up the parts. I also tack the boss first and recheck the actual arrangement before fully brazing the boss. And I only use brass/bronze to attach the bosses with. Andy
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Old 08-02-18, 06:25 AM
  #48  
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Ok thanks for the advice, I've just ordered the brakes, so I'll wait till they arrive before doing anything, and yeah I plan on using bronze for brazing them on. Cheers
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Old 08-07-18, 09:04 AM
  #49  
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Hey! That's looking great!

Like others, just a block of material - I used .750" square bar - drilled to the right width makes a fine canti fixture. I slotted mine so I had some side to side adjustment so I could get them placed just right. Get them in the fixture at the right width, then miter to fit the tubes at the right distance from the axle. SRAM/Avid do a good job of publishing specs. The linked doc below doesn't give rim diameter but you can use these to figure it out based on the rims and brakes you have.

SRAM/AVID Frame Fit Spec Documents

Good Job!

Last edited by duanedr; 08-07-18 at 09:14 AM.
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Old 09-08-18, 11:56 PM
  #50  
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Stearer and crown pinned, fluxed and ready for silver.


All brazed up. I also filled the brake hole at the front with some silver.


Jigged up to hold the dropout in phase and in line with the fork blades. I made up some silver rings and inserted 2 into each fork blade end. This was then heated until the silver bled out through the dropout socket.


Tacked a bunch of steel SHS and RHS into a fork fixture. Pretty crude, but I was reasonably happy with how it held everything in line.


Spacer to support the dummy axle at the right offset/rake from the stearer tube.


All brazed up
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