Pannier Racks: why not aluminum?

[JBMorse]

I hope this isn't a dumb question, but I often wonder why folks who build hard luggage and racks don't build the racks from aluminum tubing? Is it a question of strength, ease of welding, cost, or what?
It seems like a rack made from aluminum tubing would be easier to bend into shape and lighter.
Any ideas?

[Worroll]

If it's easier to bend into shape, then it's easier to bend out of shape.
My personal choice for steel is - strength, ease of initial fabrication, easier to find someone to repair steel when traveling.

I dumped my KLR in Mexico and a weld on my homemade luggage rack popped. A very nice farm hand welded it back together with an old banged up stick welder. If it was aluminum there is no way I would have found someone to fix it that easy.

[clintnz]

Given that it's difficult to make a pannier rack that doesn't flex a little without going into overkill mode, the big issue is that aluminium is really crappy at fatigue resistance. It will be much more prone to cracking.

Cheers
Clint

[Stan_R80/7]

My Krauser (BMW) bag mounts are made of aluminum. Two steel supports anchor the mount on each side to the frame on top and another bends around the shock mount at the bottom. The mounting hardware is steel, but the main mount frame is cast aluminum.

They are not much less weight than a crome-moly steel tube mount and quite sturdy. From looking a photo's posted on broken mounts, the steel supports are where the mounts typically fail. So, yes it can and has been done.

[fritzcoinc]

I made these out of Home Depot aluminum. The goal of the project was to make racks as light as possible. It is 1/2" round. They worked well all and all. I never lost a turn light. They would take one maybe two falls without breaking, but always bent. If I were to do it again I would use 6061 T651 3/4" and I believe this would be a very strong, as steel, and light set up. The Milwaukee power tool boxes were very light in weight as well.

[victor441]

It could be done with good design. Bicycle pannier racks are usually aluminum and the good ones stand up to heavy loads, bumps, and vibration for many miles...I've been using my set for loaded touring for 20+ years and a LOT of miles and they have held up fine

[Strong Bad]

Good aluminum parts (6061 Tx) are heat treated/artificially aged after welding. As said aluminum, is subject to work hardening and breakage due to flex. For DIY steel or even stainless would be a much better option for extended usage (In my not so humble opinion).

[tbarstow]

Originally Posted by fritzcoinc

If I were to do it again I would use 6061 T651 3/4" and I believe this would be a very strong, as steel, and light set up. The Milwaukee power tool boxes were very light in weight as well.

6061 really doesn't like to be bent.

The another reason nobody uses aluminum is that steel is a lot less expensive. I also know that pretty much anyone can spatter enough of a welding electrode onto a piece of steel to call it "welded" for an emergency repair. TIG welding rigs can be few and very far between.

[fritzcoinc]

I have since abandoned the aluminum racks in favor of plastic. I copied a Husky design. I made a steel mount bracket to attach to four points on the sub frame and made mounting post to attach the heat bent plastic sheet rack. Strong, way light, no cracking issues. Material is Star Board. This is the material used in boats for custom rod racks and such. One of the goals of this project was to get the carried load as low as possible. the canvas bags are army surplus stuff.

[Bronco638]

You lost me a little here. Are the sub-frame pieces you added Star Board or metal? They look like aluminum to me.

Originally Posted by fritzcoinc

Is this piece the Star Board?

Originally Posted by fritzcoinc

Thanks.

[LuciferMutt]

Most type of aluminum don't bend well without introducing stress cracks -- even if you can't see them, they are there. It might last a day, a year, ten years, but I'd rather not gamble on that.

There are bendable types of aluminum, but I don't know if they are available in tube?

[sailah]

6063 pipe I get locally bends nicely. It's 0.75" nominal which puts the OD at 1.05" . I've bent it on my JD squared 1" tubing die and it gets the job done with a little gouging.

The reason I'm not using it for racks is that I can weld the steel right to the subframe of my projects and thus save some weight there compared to the bolts and brackets.

I may still do a bolt on rack system for the new bike haven't decided. If I do I'll be using the 3/4" 6063 pipe.

6061 doesn't bend for shit. 5052 bends nicely, but I've only done panniers and such. It'll take a 90 degree bend on a brake with ease. If you look very closely you can see some micro cracking almost like stretch lines but not enough to make me even the least bit nervous on a log bent seam on a pannier.

[ttpete]

Originally Posted by sailah

6063 pipe I get locally bends nicely. It's 0.75" nominal which puts the OD at 1.05" . I've bent it on my JD squared 1" tubing die and it gets the job done with a little gouging.

The reason I'm not using it for racks is that I can weld the steel right to the subframe of my projects and thus save some weight there compared to the bolts and brackets.

I may still do a bolt on rack system for the new bike haven't decided. If I do I'll be using the 3/4" 6063 pipe.

6061 doesn't bend for shit. 5052 bends nicely, but I've only done panniers and such. It'll take a 90 degree bend on a brake with ease. If you look very closely you can see some micro cracking almost like stretch lines but not enough to make me even the least bit nervous on a log bent seam on a pannier.

If you're doing sheet metal bends on a box brake, you can bend several layers on top of each other leaving them on the fingers and get a nice easy radius on the work piece that won't be as liable to crack. Then save the pieces as shoes for subsequent bends.

[Worroll]

Originally Posted by ttpete

If you're doing sheet metal bends on a box brake, you can bend several layers on top of each other leaving them on the fingers and get a nice easy radius on the work piece that won't be as liable to crack. Then save the pieces as shoes for subsequent bends.

I cut a length of 3/4 square steel tubing lengthwise into angle iron that gave a perfect radius to bend aluminum sheet around with a brake. I used 6061 T6 sheets. I used the torch to heat up the area to be bent to about 400degrees, let it cool then made the bend. This takes the heat treat out temporarily. After a few days it supposedly gets most of it's hardness back. The cases survived a hard dirt crash with just getting a bit tweaked (was able to straighten back out with a hammer. And they survived a 65mph highway crash attached to a KLR that went bouncing sideways down the highway. There was no cracks after either crash(edit- I also survived the crash without cracks- ATGATT).

[fritzcoinc]

Originally Posted by Bronco638

You lost me a little here. Are the sub-frame pieces you added Star Board or metal? They look like aluminum to me.

Is this piece the Star Board?

Thanks.

When I bent the aluminum rod I heated the bend area with a propane torch to 600 DF. I used a temp stick to control the heating. There were no cracks, remember I used pure aluminum and not 6061 T651. However the formability of 6061 in the T651 condition is rated as fair so some care will be required to bend without cracking. There are no issues at all welding 6061.

The mount that attaches at four points on the sub frame is hot rolled steel flat bar 1/8" thick x 1 1/2" from Home Depot. When welded and fitted complete I painted it with silver epoxy spray paint. That's why it looks like aluminum.

The white plastic is Star Board.

I made a wood die to form the Star Board sheet. The sheet was heated to 160 DF then quickly removed from oven and clamped in the die and allowed to cool in the die. I made one of these Star Board racks for my Husky too. It mounts on the OEM Husky steel mounting I copied for the Honda. The OEM Husky rack is molded plastic and looks great but is very small and again I wanted to get the load weight as low as possible.

I carry tools in one canvas bag and a fuel bottle in the other. The area between the canvas bags is a deep saddle for other stuff.