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A typical pickup truck will have the standard 4 wheels. A modified version that is designed to carry heavy loads will have 6 wheels, 2 in the front and 4 in the back, 2 on the left, paired together, and 2 on the right, paired together. Pairs of wheels are also common on other trucks, like the typical
"18-wheeler".
A bicycle is in some ways the most efficient form of transportation, because while it is lightweight, it can carry many times its own weight. So, power used to move the bicycle and the rider mostly goes toward moving the rider. Compare that to a big truck, which tends to weigh about the same as the maximum load it can carry; half of that vehicle's power goes to moving the vehicle, not the load.
Nevertheless, bicycles do have weight limits; a bike that carries too much weight will often experience broken spokes, most often in the rear wheels. That's because of the way the typical bicycle is designed, more of the rider's wieght is carried by the rear wheel than by the front wheel.
So, this Idea is simple; replace the single rear wheel with a pair of wheels. Both wheels would be on the same axle and inside the frame of the bicycle; this is not a "trike" design; at first glance this bike will appear to be quite ordinary. But this bike can carry a quite heavy rider, with twice as many spokes for support. And anyone who thinks riding a trike is "sissy" will not object to riding this bike!
Naturally, the rear part of the bike frame will need to be a bit wider, to accommodate two wheels. And the brake system might need modification as well, although many new bikes these days have a kind of disc brake (could easily put the disc on one wheel while the gear changing mechanism is attached to the other wheel).
Not the one I saw, but similar
http://www.walmart....0944&ci_sku=5679542
[21 Quest, Apr 24 2009]
More comfortable (but less cargo)
http://urbanscooter...Adult-Tricycle.html
[21 Quest, Apr 24 2009]
Closer, and stronger, but smaller cargo deck
http://urbanscooter...trial-Tricycle.html
[21 Quest, Apr 24 2009]
This ought to do it!
http://urbanscooter...-with-Platform.html
[21 Quest, Apr 24 2009]
Load-bearing bicycle
http://www.worldbik...ian-bicycle-company
//in addition to hauling large loads of goods with our heavy load-bearing bicycle. By owning a heavy load-bearing bicycle one has the means to work via transporting water and/or goods from rural areas into the city. By owning a bike Zambians are empowered to start their own businesses and have the tools to succeed financially for themselves and their dependents.// [21 Quest, Apr 24 2009]
Bamboo Bicycle, looks like a grasshopper
http://www.youtube....watch?v=C5VdRaJkc7c
[21 Quest, Apr 24 2009]
[link]
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I've seen bicycles with very wide (about 4-inch) rear wheels, and that would probably get you the same benefits as a pair of normal wheels. However, if you're planning to carry a load heavy enough to damage the spokes on a wheel, then a trike is probably your best bet, because you have to take balance into consideration. A very heavy load is going to make balance a hard thing to achieve and to maintain while cornering. I saw a guy yesterday riding a trike with a cargo deck between the rear wheels. I think he had a large garbage bag full of empty cans in it. I imagine that would bear the same kind of weight you need, while retaining your balance, with the added benefit of a large cargo deck to set your load on. |
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And the advantage of this over a single wheel with a stronger
rim and spokes (but using the same frame and breaks) is..... |
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[21 Quest], a guy weighing 150kilograms will need the bike to be able to carry the load. An existing bike probably can, for a modest time, until the spokes start breaking. In this case the distribution of weight is nearly normal; the trike design is not needed if the rider has decent balance and bike-riding practice. |
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[maxwellBuchanan], the advantage is that the heavy-duty bike wheels are not easy to find in the average bicycle shop. But all shops have plenty of ordinary wheels available. |
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Ok. The links, by the way, are just things I thought you might be interested in, not meant to invalidate your idea. The last one, if you look closesly, has bamboo reinforcements in the wheels for greater load-bearing strength and in the video it carries 3 guys all weighing over 200 lbs. |
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By the way, I've never seen a 330-lb person riding a bicycle. I've very rarely seen them ride motorcycles. No offense, but in regards to your comment about balance, I doubt a person weighing that much has a lot of practice riding bicycles, and decent balance on such a top-heavy load is not going to be easy to come by. I guess if they're trying really hard to lose the weight, they might... |
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I'd go with the industrial load-bearing trike (links #3 & 4), personally. They can hold up to 350 lbs and are made of industrial-strength steel. Or the bamboo bike (link #6). You've got to take frame strength into consideration, too. |
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[21 Quest], it might be a kind of chicen-and-egg issue, because if the big guy is always breaking the bike he tries to ride, because it can't carry the load long enough, then of course you won't see many big guys on bicycles. (There are plenty of heavy-set motorcyclists, though.) |
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Um, 320 lbs here when I started riding, it's dropped a bit
since then. However, a deep v wheel, with the correct
spokes and keeping them correctly tensioned will stand up
to an awful lot. I routinely drop 30-40 lbs on my rear rack
without any wheel breakage problems. |
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four words, Ho Chi Minh Trail. A properly tuned and loaded bicycle can transport 350lbs, plus rider, over cross country terrain for 150 miles without failure. |
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// But all shops have plenty of ordinary wheels available.//
Yes, but they sell very few bikes capable of taking two rear
wheels. |
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If you've got to either make and distribute modified bike
frames which will only be useable with a doubled-up standard
wheel, or a modified bike wheel which can be fitted to a
standard frame, it's a nob rainer. |
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Don't forget that except at very slow speeds, you steer by leaning. Two back wheels would make it hard to steer the normal way, but not really stable enough to steer like a trike, unless you had them wide enough, in which case it's just a trike. |
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Also, due to uneven ground and leaning, only one of the rear wheels would be supporting the weight much of the time, which may defeat the purpose to some extent. |
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Ah, which leads to where I was going. With some smart suspension, this could be a racing enhancement. |
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This design specifically says both wheels have the same axle. Though this can be modified to accommodate a slight unevenness of the ground, it would be inferior when compared to independently suspended rear wheels with their own axles to handle extreme unevenness, especially often encountered when leaning upon cornering on rough roads. The only way to accommodate unevenness is to have a horizontal support beam structure to which the axle can pivot, but within limits such that the downward force should only lie somewhere between the two ground contact areas of the two wheels. Well, this is much simpler than independently suspended rear wheels, but when only one of the rear wheels would be supporting the weight at a certain instance, as pointed by [spidermother], the purpose could be defeated. |
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