SF Cyclotouring

Ride reports and other ramblings from a San Francisco cyclist.

12/22/2010

Rack Building Tips

Second Bend

Someone over on Flickr asked me about getting started with rack-building. Here's what I wrote to him, which I'm reposting here for posterity:

Here's where I learned about building racks:

1) Alex Wetmore's "Rack Building Basics" series of blog posts:
http://alexwetmore.org/?cat=298

2) Alistair Spence's Flickr photos:
http://www.flickr.com/photos/duncancycles

3) Pat S's blog:
http://26inchslicks.blogspot.com/

Spend a few hours/days reading those, and you'll learn a lot.

On tubing choices, Alex has recommended that 5/16" tubing is the best all-around choice, because it's beefy enough for a lightweight porteur rack, but svelte enough for a small front rando-bag rack. The other two tubing choices are typically 1/4" for small racks and 3/8" for heavy-duty cargo racks. I've been working with 5/16x0.35" tubing, and the first porteur rack I built holds 40 pounds with ease.

Benders are specific to your tubing choice. There exist low-cost "tri-benders" with three grooves for 1/4, 5/16, and 3/8" tubing, but those won't bend chromoly steel -- don't bother with those. The bender I bought is a Ridgid 405 for 5/16" diameter tubing, which runs about $60-65:

http://www.toolup.com/ridgid_36092_model-405-408m-lever-bender.aspx

I've been buying my tubing from Wicks Aircraft Supply:
http://www.wicksaircraft.com/catalog/product_cat.php/subid=10232/index.html

They aren't the cheapest, but it's easy to order online and there's no minimum order. I buy tubing from them in 4-foot sections so avoid oversize shipping charges. It works out to roughly $3/foot, including shipping.

I just use a hacksaw to make cuts. If I want to be precise about it, I'll use a fork-steerer cutting guide to ensure things are perpendicular:
http://www.performancebike.com/bikes/Product_10052_10551_1030352_-1_1549000_20000_400145

I use 1/8" thick mild steel sourced from a local hardware store to make rack tabs.

Other helpful tools:
1) Power Drill and a variety of bits -- you'll need this to drill vent holes in tubing, and holes in rack tabs

2) Bench vise

3) Tubing blocks -- you'll need to make these. Pat's blog has good tips on doing so.

4) Hand files, particularly 10" & 12" double-cut flat bastard files, and 10" & 12" round bastard files

5) Hack saw. Get one with long blade pins so you can double-up blades for slot cutting.

6) Tape Measure

7) Cheap bubble level

8) Cheap square of some sort

9) Lots of emery paper/production cloth -- sold in rolls in the plumbing department of most hardware stores

10) A "tube cleaning bit" for your drill. See
http://www.flickr.com/photos/duncancycles/2295388442/in/set-72157604138214903/

11) Lots of old leather toe straps, plus various small clamps, for jigging/fixturing pieces during brazing. Leather is important because it won't melt like nylon straps will!

12) A torch, brazing rod, and flux. I'd love an oxy-acetylene setup, but for now I'm just using a Bernzomatic handheld MAPP torch, which I bought at Home Depot years ago. Get filler rod and flux from Henry James:

GASFLUX PASTE FLUX Type “B” PASTE FLUX-Brass
GASFLUX C-04 BRASS ROD 1/16” Diameter


Let me know if there's anything else you're curious about...

3 Comments:

Anonymous Sean said...

Hey Jim - It's Sean from SFR.

Quick question. Any tips for keeping the bends in phase? I've trying to just guesstimate, but by the final bend I'm just a tad off. I'm not sure it really matters much structurally, but it would be nice to be super precise.

I also thought about drawing a straight line down the tubing, but that can be tricky since the tubing is so thin.

Here's a rack platform I made over the past weekend.

http://www.flickr.com/photos/seanchon/5281985915/

1:35 PM  
Blogger Jim G said...

Sean,

I just eyeball the tubing to keep the bends in phase. At the second bend, eyeball down the plane of the bender and adjust the tubing until the first bend is lined up. After making that bend, lay the tubing on a flat surface and tweak it until it lays mostly flat. At least that's what I do.

Your platform looks good! What tubing are you using -- looks like 3/8"?

1:47 PM  
Blogger Jim G said...

Sean,

Check this newer post...contains a video of bending the deck.

http://sfcyclotouring.blogspot.com/2010/12/tube-bending.html

1:43 AM  

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