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Sunday, December 14, 2008

Excessive Cargo Capacity

Does not really exist. :-)

In the late afternoon, I was about to make a run to the grocery store, then realized that a tiny oversight in the new cargo pod design prevented me from using the existing trailer: There's no place to attach the "hitch", which was simply a bar-stem. Oops. :-(

I pondered for a moment, and thought of a bunch of solutions, but none I could make before it would get seriously dark and much colder (been nippy all day, and breezy to windy, making it much worse). So I decided I'd just go for what I absolutely had to have for tonite and tomorrow, in case I don't finish the new trailer (not really started yet, except design) and/or don't get a hitchmount made for the old one.

As you can see below, I didn't stick with the plan:

Besides the five 12-packs of soda you can see (each of which is around 10.5 pounds), there's also four 5-pound-ish flats of chicken breast and other assorted heavy-ish things packed in the cargo pod proper. I'd guess total about 80 pounds of groceries. Nowhere near what I carry on the trailer. I didn't intend to get this much, but they had a very big sale on the stuff, and I didn't want to miss the sale in case I didn't get back up there in the next two days (possible), and as cold as it was, getting darker and colder, I wasn't going to go back for a second trip tonite if I could possibly help it.

That's a lot of weight, but not only did it not have a problem with it, it balanced fairly well! The only part I had any problems with at all were mount/dismount and initial start, since due to the left-biased weight distribution, I could not just stand over the frame and push down with one pedal to start moving, I had to sit in the seat so I could use it for leverage to let my body balance the bike, and start in the lowest gear and quickly upshift from there. Would've been really handy to have the motor about then. ;-)

I took the pics right after getting home, before unloading it.

The cargo pod is in a mostly-finished state in the pics, with hinges and lock installed. It's only a cheap lock off the old electric scooter carcass, and will be replaced with two much better locks (and probably a different lid) and piano hinges, as soon as I have time and find the keys to the locks. There'll be more pics posted later of the pods metamorphosis into the current state, once I make the right-side unit. I didn't take pics of the left side one in-progress mostly because I forgot until too far into it to matter much, but also because I was changing things as I built it, thinking suddenly of better ways to do various things even as I was marking or drilling a hole for the previous way(s).


  1. It took about five minutes for my dial-up to load the page. I don't know if it is hard to add more pages.

    I see how you had carried more weight than I have for a long time. The pannier style system you use helps distribute the weight for balance. My bike tipped over once because all the weight was above the wheel.

    I have added a rack over the front wheel now, too. I find that I can carry about 20 pounds there. it helps balance, but makes the steering more sluggish, though.

  2. Sorry about the slow load; I've fixed it by making only the last post show up, with a more accessible archive list on the right.

    The panniers definitely work better than the cargo rack over the tires, or even just baskets above the wheel axle centerlines. Even with just the single pannier on the left side, heavily loaded, I can balance the bike far better than with the same stuff in even loads on both sides of a basket arrangement.

    I don't recommend front over-wheel racks with any kind of weight on them, because they affect steering too much, and if enough of the weight is in front of the wheel axle, it can contribute to flipping the bike during braking for sudden stops (such as a pedestrian stepping off the sidewalk in front of you, or a vehicle suddenly pulling out of driveways/etc or turning right in front of you at an intersection).

    There are a number of reasons I took the front baskets off the bike, but steering and braking were the two biggest ones.

    Now, if you were to put panniers that sit mostly below the wheel axle center, then most of the mass is lower and braking isn't likely to flip you, but steering is still a problem. The more mass you have up front on that fork, the more force it takes to turn it, and the slower it is to turn, making some maneuvers more difficult, especially during sudden traffic pattern changes. That can get dangerous.

    One other very dangerous thing is that if you have enough weight on the front, during a sudden quick turn it is sometimes possible to actually have the handlebar stem turn inside the headseat, instead of just turning the wheel, if it is not *very* tight. This will leave your steering canted until you stop and readjust it, assuming you carry tools to do this with you. I had this happen on mine with heavily loaded front baskets more than once, even though I had the stem as tight as it would physically get. (Fortunately, I carry everything I need to take the bike apart and put it back together, excepting things that I could not fix on the road anyway, like a freewheel/freehub.)

    So be careful about evasive maneuvers and such when you have heavy front-end cargo.

    The only good thing about having mass up front as well as in back is that it puts more weight on the steering contact patch, making certain kinds of skidding during steering less likely. The lower to the ground that weight is, the less likely tipping or flipping during a turn is.

    If you can do them, I highly suggest low-riding panniers instead of racks for any cargo that will fit in them. Keep the rack(s) only for things that can't be put in the panniers. For instance, a 40 pound bag of dog food doesn't fit in the pannier, but it does fit exactly across the top of the rear rack, hanging over down on top of the panniers. Unfortunately, it also keeps the bike from balancing very well, so I don't like doing it, and use the trailer instead when I can, for loads like that. It's a lot safer. :-)

    That said, I have another project in progress I'll post about in a little bit, involving adding a second rear triangle behind the built-in one, and moving the rear wheel into the second one, with the seat down between the two, semi-reclined. Overall would slightly resemble the "extra cycle" type of cargo bike, but with some added benefits of a semi-recumbent style bike. Still experimenting with shapes and parts, so no pics/etc., yet.

  3. Thanks for changing that front page.

    I seem to prefer the extra sluggishness with the balance that redistribution of weight gives, even if above the wheel. That is with about 30% front / 70% rear weight distribution and up to 70 pounds. Weight over just the front wheel would be bad. But with some of the weight near the front wheel, the bike tends to wobble, sway, and drift less. Also, the closer the weight is to the steering pivot point, the less it will tend to add inertia to the steering. In order for luggage to not hit the frame, it then means placement higher up. I lay a flattish box vertically on the rack and strap it to the handlebars.

    I have had a trailer since last summer. I find that it produces a lot of drag. The wheels are only ten inches, so it ends up really dissipating a lot of energy of motion through tire friction. But if I really need to carry about 100 pounds, or more, a short distance, I plan to use it. I just have to be prepared to use much more battery energy.

    Also, the trailer tends to cause two other problems, fishtailing and flipping the bike before you get on, especially while loading it.

  4. For the trailer drag, larger wheels would help. Are they standard bike wheels? If so, you can probably change them out by picking up a couple of kids' bikes from a thrift store for a few bucks (Deseret Industries at 27th Ave & Northern often has a number of them), and swapping out for 20" wheels, which is the smallest I can easily use on my trailer.

    Airing them up more will also help, if they aren't solid tires, and if they can handle higher pressures. My trailer unfortunately is not exactly symmetrical, so one wheel's contact patch is just in front of the other. That causes trailer-width bumps to rock the trailer, and if I happen to hit a series of them at the right speed (such as where the road has been scraped, graded, or patched) it will resonate and the trailer will tip over, if I air up the tires to normal capacity when it's empty.

    So I have to leave them low-pressure when empty, and air them up more as I fill up the trailer, to keep it from bouncing. :-(

    Loading the trailer presents problems best solved with a fixed-stand or a latching brake. I'll have three wheels on my next trailer, one small one in front as a caster to keep a loaded trailer from pulling the bike's rear downward, and two larger ones just to the rear of the trailer's centerline to actually carry the load. Then there will be a brake on the two larger wheels I can engage when I park it, to keep it from moving during loading or on a slant.

    The other option on your front cargo besides higher up is much lower down, near or below the axle point. Depends on how wide the cargo pods are.

    One other option beyond that is to revamp the bike itself into something like the extra cycle type bikes, which I am doing for my next project.

  5. I think you have a good idea about the front luggage. I have the problem of squeezing the bike into the front room of my house, so luggage has to be above the wheels anyway.

    I think the 10" tires are rated 30 pounds, but I took them up to about 35 or 40. I lack storage space so can't manage the trailer with bigger wheels.

    Your idea of the front wheel to hold the weight steady while loading and unloading could work. My trailer has a transverse axle which eliminates the problems of asymmetry that causes yours to roll with jitter.

  6. Sorry I somehow missed your last reply. :-(

    My bike also has to fit in the small front room, between the couch that sits under the front window by the door, and the varied stuff against the not-so-far wall, while still leaving enough space for the people and the dogs to easily get thru without bumping anything. The trailer has to stay outside, since I don't have enough space inside for it.

    Most of the tires I've dealt with can take perhaps another 2/3 of their ratings before blowing off the rims, and I've heard of people doubling the pressures without failure, if the tubes inside are good (cheap tubes will often explode at the valve stem base long before you get to even half-again the max rated pressure).

    My future trailer will have a transverse axle as well, but I don't have any really hard-metal rod I can use for it yet. The best I have is a piece of coarse-threaded rod about 3.5 feet long or so, which will probably bend fairly easily. The upcoming trailer will probably just have to use regular short axles again, though I will use the front forks instead of rear triangles, as it'll save a lot of weight.

    When I didn't have the front wheel on the trailer, balancing it during loading/unloading was very difficult, especially with individual items that were heavy, as removing or adding just one would unbalance it and cause the bike to fall over as well. Now I don't have to worry about that (though I have had problems with the steering part of that wheel, and I need to redo it entirely before it sticks during a bike turn with a load heavy enough in front to force the wheel down on pavement, as failure to turn at that point would cause me to crash, most likely.

    I may not need to worry about it, though, if the current Crazy Bike project works out, as I would have room for up to at least four of the large metal box cargo pods I'm using just one of on the Columbia upright bike right now.

    What do you think of that particular project? (you haven't commented on any other blog posts, so I'm unsure if you're following it or just read and commented on this post).


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