Construction ideas for a DIY rack
 

Hi all,

I've been looking around for a stronger rear rack for my mountain bike for use off-road. This is part of a wider project for a touring trailer, which is discussed in a separate thread.

Previously I've just bought off-the-shelf ones, and they have two big limitations:

• No towing hitch; my current trailer uses an axle mounting which I'm not keen on
• Despite 25 and 30kg load capacities, and only carrying about 16kg, they seem to fail catastrophically regularly. (between 1000km and 2000km)

Having seen some of the posts here from the likes of @thechadillac and @Charlie_R, I'm impressed and inspired to try it myself.

I don't have access to a welder, so I'm thinking along the lines of gusset plate construction using aluminium tube sections (maybe 25.4mm box section?) which are widely available in hardware shops here, and bolting these sections together using 1-2mm aluminium plate.

What has peoples experiences been with that style of construction? Are there any gotchas apart from ensuring bolts don't rattle loose?

The other method I'm considering is using joiner sections like these: Connect-it 3 Way Corner Joiner I/N 1138482 | Bunnings Warehouse -- I'm not sure about their tensile strength however. Perhaps a combination of the two techniques may do the trick? (Edit, seems I can get all-aluminium ones)

Another question is the design of the rack with regards to rear wheel access. Two rear rack/trailer hitch designs come to mind here:

• thechadillac's deer cart
• Charlie_R's rack

How do you go changing a tyre on the rear wheel with that style of rack?

With my rack, I have to remove the skewer to remove the wheel. A minor inconvenience, to me.

There is another problem that has cropped up recently. I've had to replace the pop rivets with screws, and change out all the sheet metal screws I used for longer machine screws. I used #8-32 screws, about equivalent to 4mm fine thread, with self locking nuts. For you, a 30mm would work for the 25.4mm box section. Yes, I used 1" (25.4mm) for my rack.

Another gotcha is room for the rear shift cable. A longer bottom section where I dropped down under the cassette/derailleur would have been better, leaving more room for the cable.

Heim joint is a must, My swivel wore out the rear crosspiece in only 1000 miles. Turned the round hole oval.

Good luck with your build, however you do it!

My attempt with that kind of materials - something on the front of the bike, not a rear rack - turned out to be really heavy with all of the hardware needed to bolt it together and onto the bike. If I were you, I'd estimate the weights of everything and add it all up beforehand.

Ahh agreed, but is it a case of flip the bike on its side/over or is there some way of getting it out by removing a section from the back?

Ahh okay, so I'll have to pay careful attention to that.

Ouch, okay. My father and I have been bouncing ideas off each-other, including the idea of using a castor (mentioned in another thread here), using U-bolts, crude approximations of the block and pin style hitches used on camper trailers, various other ideas.

I suppose part of this is the softness of the aluminium, versus something harder like steel. I take it the heim joint has been more reliable?

Many thanks… I'll post back on the updates.

Yes, this is a consideration too. Looking at some of the corner joints I saw mentioned, they mention weights in the order of ~300g for the solid aluminium ones… probably a bit on the heavy side, but we'll see. I know what I build will be heavier than what I have now.

There are also the through axle skewers... It might simplify the wheel removal.

I like the heim joint on my trailer. However, I would probably go for one to maximize the swiveling if I was doing it again.

QA1 PCYMR10T High Misalign Chromoly Heim Joint Rod Ends 5/8-18 RH Male - Speedway Motors, America's Oldest Speed Shop


If you use those internal joints for rack construction, you probably still need to bolt them together. Weight does add up quickly.

My old Blackburn rack has withstood the test of time. I don't carry a lot on it, but often awkward loads. It is important to have it mounted tight with no flex. I have wondered about the new rack mounts that I see with what appears to be just flimsy metal.

I haven't tried the Burley Moose, but it is designed to be strong enough to connect the kid's Kazoo and Piccolo to the rack, so it has to have some strength.

Of course, for touring, you would loose the use of the rack by using it as a rack trailer hitch.

::Moose Rack, Trailercycle | Kazoo - Burley--BURLEY--
::Trailercycle Hitch | Kazoo - Burley--BURLEY--

http://www.burley.com/shop/images/pi...large_copy.jpg

Yep, looks like the device I'll need to source, although we've got a couple of alternatives. Key seems to be hard wearing, i.e. stainless steel not aluminium.

True, but I may not notice 1kg extra: I already carry ~16kg on the back not including the rack which itself feels like it's ~2kg itself.

Yeah, that style wouldn't work for me. Not with this on the back:
http://stuartl.longlandclan.yi.org/b...sl-bm-2712.jpg

That is a pretty wild rack, and a lot of gear. The motorcycle case sits awfully far back on your rack, and undoubtedly adds stress to the rack.

Perhaps it is time to start looking at a cargo bike build.

The XtraCycle FreeRadical is an interesting add-on for an existing bike. I think there was someone on the board that posted recently about one.
Xtracycle Longbike Cargobike kit
Xtracycle Free Radical

Ahhh, you're in Australia. Shipping would be fun :(

But, it may give some ideas.

I welded my (first) cargo bike together from pieces. It came out to be a real beast. But I'd probably try to lighten it some if I did it again. Still, it is a beast.

Funnily enough, the breaks started happening once I got the panniers… when I got those I simply moved things like my battery pack and spare tubes to those, so it was a redistribution of weight.

Then I stated getting problems. The box is as far forward as I can reliably position it: any further forward and it doesn't open (the seat is in the way).

Bingo. There's a shop that sells some cargo bikes in Brisbane (at West End, so a fair distance from home), but I'd prefer to try and utilise what I've got. Not optimal I realise, but it's about 80% there, if I can fix the remaining 20% we'll be fine.

At least it'll probably see one of the bikes out at which point I can look at my options.

This is true, welding isn't an option for me as I don't have access to one, so it'll be bolting sections together, but I shall have a look and see what can be achieved. Certainly this is closer to what I'll need I think.

can't tell from the profile if it would look funny or not (or if you care), but could you put the cycle trunk on sideways, so it clears the seat sitting more forward when open? or find another if it isn't too expensive. i've seen at least one (a big one though) made to open that way.

Or perhaps put the hinges on the back, opening from the front, although then the lights would all be connected backwards.
Or, while you're building, you could design some drawer slides and a lock to push it forward and back.

That isn't E-Assist is it? How many electronics do you have on it? Do you have a generator?

As far as the rack, I went with oversized tubing on my cargo rack, but I think it turned out to be a bit of overkill, and far too heavy. Most of the other cargo bikes i see use much thinner tubing.

http://bikeforums.net/attachment.php...hmentid=439492

That, of course, was all welded. Anyway, I'd encourage you to consider light and simplicity in your design. Also make sure you can connect your paniers.

Yeah, mounting it on a drawer is one possibility… sideways won't work because the seat will still be in the way. A drawer has the drawback of extra parts that can break, so I probably don't save much there.

No to all of the above. It's all pedal power. The electrical system is charged overnight, and powers lights and the radio station. There's also a 12V cigarette lighter socket for charging devices (e.g. my headlight, phone, etc).

There are a couple of motors on-board: one attached to a tiny propeller of a cooling fan on the radio, the other attached to the platters of a portable hard drive. ;-)

I'm planning on long trips, power generation will be a 12V 40W solar panel that will form a "roof" over my trailer.

You've done a nice job on that. Not sure what metal you used, probably not aluminium since it's welded construction. I realise this is going to be a case of the laws of diminishing returns once I go above a certain size. By the sounds of things, 1" box aluminium is strong enough provided I choose a suitable design for the hitch itself. (The heim joint looks good so far.)

As for pannier attachment: I've had to make rails for my existing racks for attaching the panniers, I use gutter extrusion attached to the existing panniers using U-bolts. That has worked well so far, and the same technique should work here.

Here is my hitch detail.

I put the pin on the bike, and the Heim joint on the trailer. As I mentioned earlier, if I was doing it over again, I'd choose a heim joint with a bit more lateral motion.

http://bikeforums.net/attachment.php...hmentid=439525

The bike was all steel, mainly made from scraps I had laying around. The bulk of the rack came from some steel bookshelf? parts I had bought earlier. The trailer is aluminum, currently with wood decking. I was having a lot of problems with my aluminum welding... I need a bit more practice.

Check out bike hacks on the web! The question you ask is a re accruing theme. The site has so many good ideas that don't evolve welding.

Early Bikes-at-work trailers consisted of 6' long side trusses, a zigzag bent tube was bolted between 2 straight tubes at both top and bottom of the Ziggy wave.

i don't want to run his thread off on a tangent. could you post this in the home built xtracycle thread, or point out the page if i missed it, so i can ask you a barrage (ok... maybe just one or two) of questions?