Newbie looking for diy rear rack build ideas.

alpharalpha

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Originally this thread started with me looking for a steel store bought rack but has changed to a diy build so being merged into one thread. Thanks for any input/advice.
 
alpharalpha said:
I've decided that chromoly is the way to go but I only know of a few different chromoly rear racks. Thinking some of you guys might be more knowledgeable about this and give me some more options as not much is coming up with my internet searches. Thanks.

I am planning on purchasing this Steel rack with 150kgs rating from AliExpress for my new bike project.. I'll be using it to fit a rear seat .. Looks OK, and a good price so I think its worth a try!
Leo 1 Set 150kg Max Loading Capacity MTB Bike Bicycle Rack Carrier Panniers Bag Carrier Rear Seat Luggage Cycling Shelf Bracket
http://s.aliexpress.com/jUzeemMn?fromSns=Copy to Clipboard
(from AliExpress Android)
 
If your battery pack is so heavy that you worry that it will break the rear rack means that battery pack belongs in the triangle of the frame. The bike will handle and feel way better.
 
The widely available chromoly steel racks are those from Tubus and from Surly. The Tubus Cargo has better bracing, but it is optimized for carrying panniers. Surly racks have big wide rack tops and would be great for mounting battery packs and/or controllers.

All Tubus and Surly racks are expensive as racks go. There are equally sturdy aluminum racks available. I have to wonder what you intend to carry that an Axiom aluminum rack rated for 50kg wouldn't do. Because carrying even half that much weight on a rack is really unpleasant.

There is absolutely no way the "150kg" AliExpress rack is good for that kind of weight. Even if it were, the mounting points on the bike aren't. The fact that they brazenly lie about the weight capacity makes me wonder what other shenanigans they try to get away with.
 
My 50 kg rear rack arrived with 25 kg stamped into the metal
Might cope with 30kg
If you check like for like the same looking item may well be shown as 25kg
 
THat "150kg" rack *might* support that much weight if you carefully stack up weights on the bare rack secured to something with hardware other than what it comes with to attach to the bike.

But if you put it on a bike and put that weight on it, then ride down the road, I suspect that weird curved bit it has would just collapse the whole side it's on from pedal-wobble of the bike, much less any potholes/curb drops.

Even if that bit holds, I doubt the fasteners it has would, and if they did I doubt the bike frame mount points would.


I've done a lot of heavy cargo hauling with all sorts of improvised and purchased bike stuff, and I'd say that most of the stuff out there probably can't handle even half of what it's "rated" for, unless you're on perfectly smooth roads (so there's no bump stresses) and you don't pedal (causing hte bike to wag its' tail back and forth, stressing the rack from side-to-side forces).

For stuff more than around 25lbs, you're way better off sticking it in panniers down around axle level--the higher it is the harder it is to control the bike, and the harder it is on the rack and the bike frame/mountpoints, from side-to-side forces.


If you really have to carry heavy stuff, especially up high, you can build a rack relatively easily, if you can weld. See this post's thread for more stuff
https://endless-sphere.com/forums/viewtopic.php?f=3&t=46183&p=1346971&hilit=bill*+rack#p1346971
I don't know how much weight it can handle, but he's had someone ride on the rack without problems. (don't know their weight, but probably over 100lbs, could be twice that; I never saw it). The rack itself is unlikely to fail with any weight that wont' collapse the bike wheels, and most likely the frame mount points or hardware would break long before then.

I'd also worked out one that could handle as much weight as the stays could deal with, that would have "clamping half tubes" at the ends of the mounting rails instead of bolt-on points, where a tube is cut in half and welded to the rack rail, to sit on the chainstay and seatstay, and the other half goes below the stay and a clamp (hose, etc) goes around both halves to secure the rack to the bike, then these tubes spread the load over the stays...but even the stays aren't meant to support that kind of weight in that direction, so....

This is why I've ended up with the SB Cruiser trike (and CrazyBike2 before it), which does almost everything I need it to do by itself (and most of the rest with a trailer). :)
 
Agreed. If nothing else, the mounting points are the weak link in bolt on racks, if not seriously reinforced with heavy gussets, or some how overbuilt.

However, I would rate the welded on mild steel rack on that huffy at 150kg, even though the cheap wheel would die quickly.

Modifications to existing racks can hold a lot of weight, if you are willing to go there. I got very sturdy results from putting reinforcing legs under the sturdiest seat post racks.

In this pic, a full suspension bike, but similarly you could add legs to help support a seatpost rack on a regular bike. You could even incorporate the leg into a custom torque arm.
 

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I have the same (or similar) rack that dogman just showed and have reinforced it with similar struts. I further reinforced the seatpost and the rack's cantilever beams with a press fit and glued wooden dowel and plywood rib respectively. The dowel at Amberwolf's suggestion so that any seatpost failure would less likely be catastrophic, and the beam rib since I drilled through that beam to mount my struts (and may make more attachments to the beam in the future) and wanted something more substantial to distribute that load. The system seems pretty stiff and robust. Though only time will tell for sure.

IMG_20171214_081945216_SM.jpg
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Chalo said:
The widely available chromoly steel racks are those from Tubus and from Surly. The Tubus Cargo has better bracing, but it is optimized for carrying panniers. Surly racks have big wide rack tops and would be great for mounting battery packs and/or controllers.

All Tubus and Surly racks are expensive as racks go. There are equally sturdy aluminum racks available. I have to wonder what you intend to carry that an Axiom aluminum rack rated for 50kg wouldn't do. Because carrying even half that much weight on a rack is really unpleasant.

There is absolutely no way the "150kg" AliExpress rack is good for that kind of weight. Even if it were, the mounting points on the bike aren't. The fact that they brazenly lie about the weight capacity makes me wonder what other shenanigans they try to get away with.

The Tubus Cosmo, wow that's a nice rack! I thought the Surly rear rack was about as nice as you could get but those things are off the hook, not cheap either I can see.
 

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Here's a nice page with an overview of the Tubus racks.
http://www.peterwhitecycles.com/tubus_racks.php
 
That's some good mounting hardware they've got there, as listed/described/pictured on the linked page. YOu could probably make a way to use that hardware with a lesser rack and have a rack that's stronger than the cheapie but not as good as the Tubus...
 
That one does look good, compared to the one with the bends in the legs.
 
I'd like to switch over to steel because of it's ability to bend over breaking. But I'm having trouble finding a chromoly rack that's long and wide as my current one. I guess it doesn't have to be chromoly, any good solid steel rack would work, and probably my current aluminum will continue to work. I've thought of attaching a couple pieces of steel like this IMG_0289a.JPG
I'm glad I took the time to snap some pics of the bike because I noticed one of the rack bolts gone and the other side very loose (don't think I'd ever checked them since I've owned the bike (10 years.) I'm going to see if I can't put one bolt all the way thru the frame and then double lock nut it. On the bottom bolts that go thru the eyelets I thread them from the inside and double lock nut them--have to grind down the head on the side where the gears are. I took Dogman Dan's advice and got some class 8 steel IMG_0297class8.JPG I wish I had known stainless wasn't strong because back in my sailing days I had a tiller on a Newport 30 4.jpg that I'd bought off this old guy who had done a lot of the repair work himself and there was a stainless steel bolt going thru the tiller and the rudder which would snap so often I kept a couple nearby to replace them.
I realized I haven't posted pics of the battery pack/rack setup and maybe given my sailing experience of running aground windward of an island and what is called anviling (which is when the waves pick the boat off the ground and then it drops, 5 tons of boat hitting the ground from 5ft felt from inside left me with an appreciation of downward force.) I relate this to my 25 +/-lb battery pack every time I hit a bump in the road. I'd think over time this may cause the aluminum to fatigue, though I don't ride off road I still wouldn't want to deal with a broken rack while out. So here's a better view of the bike and the battery packs position atop the rack. I just realized though, once I get a new front rack if the worst happened and the rear rack broke, I can unplug my battery pack and could strap it to the front until I got home. IMG_0295closeupbatterypack.JPG
IMG_0288sideview.JPG
IMG_0287quarterview.JPG
IMG_0285bikefromrear.JPG
 
I can't see the actual rack under the pack, or how it mounts to the dropouts. Both of those are important in how well it can handle whatever you use it for.

The front mounts, being flat metal strips, can't prevent the rack from wiggling or swaying back and forth, which is one thing that fatigues racks at the dropout mount points (and other places; wherever it can flex under a load). Their flatness does mean that if they're steel tehy're less likely to break first, but depending on the kind of steel and how thin, they could just shear off around the bolt holes where they mount to the frame or the rack.

Topeak uses what looks like that same front mounting system (twisted flat pieces) on the ones I've seen in person, so it's possible for such a system to work--but the dropout mounts and rest of the rack have to be stiffer to make up for it, to avoid wiggle/sway. (either from pedalling or leaning, etc).


Tubes that go from the rack to the seatstays in the middle wouldnt' be as good as ones that go to the stays nearer the seatpost as far as load transfer to the bike frame, but it would be wider "stance" in the middle of the stays providing more lateral anti-wiggle/sway of the rack. The catch is that it pushes and pulls with all the loads' weight times teh energy of sideways motion into the unsupported middle of the stays, potentially fatiguing the stays themselves.


FWIW, that trek frame/bike looks almost the same as the schwinn sierra I gave my friend Bill with the custom-built red "super-rack" (whose strength limit is probably only that of the mounting point at the frame, and the bolts holding it on :lol:).
 
That's a very light duty rack. It would make sense to try a sturdy rack intended for loaded touring before jumping straight to something expensive or complicated.

Racks seem to be weight rated with the assumption that soft panniers will be used to carry the load. That's a lot easier on the rack than securely mounting a solid block of battery to the rack top. I would trust a rack for about half as much weight on the top versus in bags on the sides.

This principle can be inverted to suggest that it would be better to carry a battery pack in two halves, slung down low in panniers, than mounted in one piece directly to the rack top. The bike will handle better and the rack will hold up better. The battery units would of course have to be protected well enough to endure being carried in soft bags.
 
alpharalpha said:
I use my panniers. Any better rack suggestions? Is steel better?

Steel's good. Most racks are aluminum, though, and many of those are completely appropriate for heavy loads.

http://www.axiomgear.com/products/racks/journey-racks/journey/ (very good value, strangely high load rating)

https://www.jandd.com/detail.asp?PRODUCT_ID=FREXP (big sturdy rack, very conservative load rating)

The Tubus Cargo rack compares well to the above in weight and weight capacity, and it's probably stiffer laterally than either one. It costs more at $140.

Dajia Cycle Works makes a rack that is very similar to the Tubus Cargo, but a little cheaper and made from stainless steel. https://velo-orange.com/products/dajia-stainless-steel-rear-expedition-rack
 
I gave up on aluminum racks years ago, after too many failures. I built my own from steel tubing, brazed together with a small torch, and never had problems again. Now I have a brain injury, and have been trying to do the same this winter. I had to give up after weeks of frustration, and decided to buy a quality rack instead. The next morning a Tubus locc rack came up on kijiji locally, and I got it for $100 canadian. Tested to 88lbs I think, and fixable with any torch or welder. That is a $250 rack here, so good deal, like new. Still too much money imho. If you can braze or weld, build your own, it is easy and you can build as heavy or light as you wish. Even if you have to get someone else to weld it up, I think you could do so for much less than the cost of a surly or tubus etc. Reguardless, if you carry a load, go with steel. I have been stuck in the middle of nowhere twice with busted aluminum racks when touring. they are disposable. Re: 150 kg rack baaahaahaaahaaaa!
 
You know what is holding up extremely well, 3/4" alum square and two legs down to axle mounting holes, and I have an old springy seat with steel under carriage, not the rails you normally see, no no, its vertical plate. So I added steel plate to go from seat bolt down at a 45 deg angle, about 4" then attach alum square.

There should a picture somewhere posted.
 
You know what is holding up extremely well, 3/4" alum square and two legs down to axle mounting holes, and I have an old springy seat with steel under carriage, not the rails you normally see, no no, its vertical plate. So I added steel plate to go from seat bolt down at a 45 deg angle, about 4" then attach alum square.

https://endless-sphere.com/forums/viewtopic.php?f=3&t=46183&p=1347244&hilit=rack#p1347244

I place my battery ontop and I use the rack to move the backend around.

My only concern is the mounting holes at the rear axle. Hopefully the alum doesnt rub, making the hole bigger, but I did leave lots of meat.

On one side its held on by one alum wall, so the metric bolt head is holding one wall.
The other side I did it so the metric bolt is holding both walls.

If that makes sense.

The problem with the small diameter tubular racks is that the welds will crack and the weld could fail, or the tube just breaks. I had a wooden box acting as a pannier, zip tied to the top rack side rail. The wood box had open top, and half open side, for battery.
 
I assume those "squares" are hollow - the same aluminum you can get at the hardware store?

BTW, you can get 6061 aluminum tubing at aircraftspruce.com if anybody wants something stronger than what you can get at the hardware store.
 
yes hollow not solid

solid would have been a better choice, but higher price.

I do have a bit smaller piece same shit just smaller, fits snuggly inside, telescopic I believe is what its called.
 
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