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Old 11-01-10, 01:59 AM   #1
Airburst
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Building a rear rack

Not sure if this is the right forum for this, but here goes. I'm planning to build a rear rack for my old Raleigh, and since the bike is only made from mild steel, I figured I wouldn't bother with a fancy lightweight rack. My plan is to use fairly thin mild steel bar stock (maybe 1/8", depending what I can get hold of), but I have a few questions.

I'm planning on making the two legs that join onto the frame out of a single piece of bar, avoid too many joints and keep things simple, and this requires bending the metal. My plan was to bend it in a vice, using a piece of 3/4" steel plumbing pipe to radius the bends. Will that be sufficient diameter, or should I use a larger pipe?

Also, should I heat the metal before I bend it? If so, how hot? (I've got a plumber's torch which can get steel red hot pretty quick, so I figure I can go pretty high with the temperature)

Finally, after I've bent it, will the metal require annealing or something?

Thanks in advance
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Old 11-01-10, 08:43 AM   #2
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1/8'' is quite thin, you can bend it by hand around tubes (although the radius won't be smooth if you go above a 90 deg. bend) and no heat is needed (as far I know, you never need heat if you have a proper mandrel). The radius of bend is up to you. However, 1/8'' is weak for a rack: it'll be very flexible and you may bend it by grabbing it too hard...
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Old 11-01-10, 03:46 PM   #3
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If you really aren't too fussy about results, other than function, you might try a bolted assembly using flat stock. You can place flat stock on edge for great strength, even though it is a little heavier. Here is an example for a porteur:

http://www.bikecommuters.com/2008/08...-porteur-rack/

Though the flat stock is horizontal on some of it. There is a touring rack out there in flat stock though I couldn't google it up.

You can make a rack out of 1/4" stainless, or mild steel. You need a way to weld it, possibly braze it. But the iconic racks of the 80s were solid aluminum, and many thousands have miles have been made on them. The only problem is welding aluminum. The weight cost of steel is significant, but not absolutely prohibitive, just so long as everything else you carry isn't three times heavier than need be, also.

A great alternative are wooden racks. Wood is normally the best fall back material when some high tech steel or carbon option falls through. However wood is not so good on small sections. If you want panniers then it becomes easy. The attached pic is of a wooden shopping pannier I made for my mom, but it could just as easily be the basis for touring hard shells. It is much lighter than a rack and bags, though not easily detached.

If one just wants the flat rear shelf, a light core structure would work nicely in wood.
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Old 11-02-10, 11:32 AM   #4
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There seems to have been a misundertanding here. I meant 1/8" thick flat bar stock, not round bar. Sorry, I should have made it clearer.

Peterpan1, the wood idea sounds good, but I've also got another bike with a rack which I'd like to be able to swap my panniers over to, which rules it out for me. I'm inclined to go for the bolted flat bar stock design.

Last edited by Airburst; 11-02-10 at 12:28 PM.
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Old 11-02-10, 12:39 PM   #5
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It's heavy, but it will work. I think you could use 1/8" aluminum flat stock which is enormously strong, pretty cheap, and 1/3rd the weight.

I do think you can do the wood thing with regular panniers if you want. You bond the ply together, and across the top. Where you want to hang the panniers just bond some 1/2 round along the edge that will support the hooks on your panniers. Let the hooks penetrate the ply. In the areas where the hook will penetrate, remove the wood and replace with solid epoxy so that where the hooks go through the ply the hole is in the plastic. By the way, the ply is fiberglassed. So it is pretty bulletproof. In fact the half round could be a little blob of epoxy putty.
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Old 11-02-10, 04:19 PM   #6
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perhaps fabricate the top out of angle Iron, a rectangle.
then straight struts perhaps use some 3/16 round wire, as cross bracing.
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Old 11-02-10, 04:24 PM   #7
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Well, I've only just ordered the panniers themselves, so I figure I'll wait until they get here before I actually build anything, but the wood is sounding plausible. Thanks for suggesting it.
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Old 11-02-10, 05:45 PM   #8
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Have you seen this guy's homemade racks? http://www.bicyclinglife.com/howto/HeavyDutyRacks.htm

They look really heavy duty, and you could likely use bar that isn't as wide. I also like the idea of aluminum flat bar.
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Old 11-02-10, 06:46 PM   #9
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check out the rack i just made over on the "show us your build" thread. Maybe it'll give you some ideas. http://www.bikeforums.net/showthread...1#post11718582
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Old 11-02-10, 09:50 PM   #10
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Making 4130 racks is pretty easy, but even for me, with the mass of tools I have, it cost me more money than buying retail. And sadly the same is probably true with wood, though in that case I had all the materials on hand as a result of having built my boat. The flat stock and screws method may not be pretty but it is the sort of thing one can put together from the local hardware store. The reality is for what the postage/gas for 4130 cost, I could have bought one of those Blackburn rip-offs that regularly make it across the country.
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Old 11-03-10, 06:28 AM   #11
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Agree totally with PeterP. Labor kills it for me. Brazed on the bike? forgetta' bout' it! Just lost profit of 5 bucks. More of a personal challenge, a skills test challenge.

~A
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Old 11-03-10, 11:47 AM   #12
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Right, it isn't an expensive hobby, compared to golf, even one round. It's cheaper to build than to get someone to make you a custom, it just isn't cheaper than Chinese. And that stuff will hold up for many uses. Also rack building is one of the cheaper ways of experimenting with frame related stuff, you really can do it with a MAPP torch, and you can cope with a rat tail file.
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Old 11-03-10, 09:20 PM   #13
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I made a bolted together rack kind of like the one in clasher's link, at least in terms of size. I wanted something with a bigger platform then seemed normal. As the basis of the rack, I bolted together 1x1/8"aluminum angle iron, using machine screws and countersinking the heads for a flush surface. used angle stock to connect to the braze ons by the saddle, and 1/16 u channel to connect to the dropout brazeon. Worked great when everything stayed tight. The original plan was to have a vertical and a bracing u channel to the 2 dropouts on the bike. I originally made in 6" wide, but later I thought it would be better wider. Also in the plans was 1x18 alum flat bar a couple times across the rack to keep soft stuff from going into the rack. I was using a bungee cord wrapped a couple times around for that task.

Wish I had pics to show, but the bike got stolen even before I finished my plans. even without the finishing touches, it worked great. I'm debating whether to rebuild like that, build out of steel per that link, or just go commercial. Either way, its on my mind because my bike needs a rack.
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Old 11-05-10, 12:05 PM   #14
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OK, update. I might be using 4130 flat bar stock, about 1/8" thick, for the rack, how would that handle being bent to 90 degrees? Better or worse than 1020 mild steel?
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Old 11-05-10, 01:27 PM   #15
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I don't know that you can bend aluminum like you can steel.
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Old 11-05-10, 02:23 PM   #16
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Aluminum seems to fatigue faster, but a single bend with a reasonable radius, I think it would be fine. As far as the flat stock is concerned, those are oversized sections, they have one direction to bend where they would bend with minimal stress, and the material would be a lot lighter. Obviously the Blackburn type racks were bent, they were also welded so they were presumably heat treated, Falanx level of complexity, too much for me.

For what it's worth both bows and arrows have been made with aluminium both uses involved repeated bending, though obviously not through yield at least not intentionally. When arrows are bent through yield, they can be re-straitened and reused though it is technically fairly difficult.
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Old 11-05-10, 03:51 PM   #17
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Try and break a piece of 1/8" thick aluminum bar and see how much it can handle before it buckles, and do so with the other materials you're thinking of building a rack out of. I priced out some bar stock in stainless and aluminum and they were both around 15$ for 6ft. worth of 1/2 wide 1/8 thick stuff. I was thinking of making a few racks for fun for the local community bike shop. I will update this thread should I ever get around to it.

Metal Supermarkets has stores in Canada, the US, and the UK: http://www.metalsupermarkets.com/MSC...gion=UK&Map=UK

They sell in small quantities so it's quite convenient.
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Old 12-03-10, 10:28 PM   #18
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I just finished building a front rack for my touring bike. I used 5/16 cold rolled steel rod. 20 foot stick was $6.00. It weighs about 5 pounds after welding. I have not really tested the amount of weight it will hold, but I have no worries about putting 40+ pounds on it. I am more concerned about the bolts that hold the rack on.
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