I regret that I haven't been able to participate in this discussion
before now, because I have been, well, doing other things.
Gary Jackson wrote:
>
> I've sent mail and heard back from a few more bicycle manufacturers.
> This is a summary:
>
> Cactus10:
>
> They told me that the BiGBOY would not hold a 180-200kg rider, but
> that they were willing to work with me on a custom bike.
That's a manufacturer I was previously unacquainted with. Thanks for
the tip.
> Surly -- I asked about the Long Haul Trucker. The fact that they
> haven't gotten back to me disappoints me the most, since their bike is
> very reasonably priced.
I have ridden lighter-duty frames than the Long Haul Trucker without
any noteworthy problems. The stock wheels on the LHT aren't going to
cut it, and I would not use the specified crank-- but as for the
frameset, you have little to worry about. Front braking might have to
be limited to less-than-extravagant power so that the fork doesn't get
bent by the load.
For my single-speed bikes, I use two old 68cm lugged steel frames with
small diameter tubes, one straight-gauge and one butted. Neither one
seems remotely up to the task of accommodating vigorous riding under a
350-pounder, but they've both done just fine. One of them served as a
platform for my first electric-assist bike, and in that role it
carried a gross weight of about 500 pounds at respectable speeds over
some of the worst pavement in the western world (in the Port of
Seattle area). The wheels are all 48-spoke; the cranks are Primo
Powerbite freestyle cranks. I coddle the forks of these two bikes by
using a caliper brake on one and no front brake on the other.
My point in bringing this up is that if you beef up the parts that
really need it (wheels, cranks, stem, bars, seat and seatpost), the
rest of the bike will probably be OK. Stay away from lightweight or
gimmicky frames, or frames that use cantilevered structures (boom
frames, "feet forward" frames, ladies' frames, elevated chainstay
frames, etc.), and you should be able to work with whatever you
find.
> Rivendell -- I asked about a model with a double top tube. This seems
> sort of silly, though, now that I know the history of the Co-Motion
> Mazama.
That's an idea worth considering-- reinforcement is reinforcement,
after all-- but a regular diamond frame can clearly cut the mustard if
it is simple and substantial. Rivendell is hesitant to use larger
tubing diameters for stylistic reasons, and that works against us big
guys. An extra frame tube in there wouldn't hurt a bit.
I'm sure you are already aware that a custom Rivendell frame costs
serious money.
To address some other issues you brought up:
In my experience, using 48 spokes allows me to have trouble-free
dished wheels (front disc or derailleur rear) where their 36-spoke
counterparts wouldn't hold up. Using high spoke count wheels is no
longer as neat and tidy a decision as it used to be, though. The most
robust of today's 26" and 700c rims just don't come in 40 or 48 hole
versions. If I had to choose between running 48 spokes on an 8/9-
speed tandem rear cassette hub laced to a 700c Sun CR18, Alex DM18,
Velocity Dyad, etc. or running 36 spokes on a dishless 7/8/14-speed
gearhub with a Kris Holm mountain unicycle rim, I'd go for the
dishless wheel with the badass rim every time.
http://www.unicycle.com/shopping/shopexd.asp?id=805
Especially in 26" MTB-sized wheels, it's difficult to find 48-hole
rims anymore that can compare to the most rugged rims available in 32
and 36 hole versions. It might be worth consulting with these folks
and seeing what they recommend:
http://www.mtbtandems.com/
As for cargo bikes, they are not as troublesome as you suggest.
Bakfietsen are a bit strange due to their linkage steering and lightly-
weighted front wheels. With a front-loader, essentially all rider
weight is borne by the rear wheel. That's not ideal, but it can be
taken into account.
Longtails ride very nicely, are not tippy unless you carry a top-heavy
or imbalanced load, and have the distinct advantage of distributing
the rider's weight evenly between the two wheels. I would happily use
a one-piece longtail frame like the Yuba Mundo, Kona Ute, or Surly Big
Dummy. I would not ride an Xtracycle-equipped frame due to the
dropout/subframe separation issues I have seen on some of them when
they are heavily loaded.
The Yuba Mundo and Kona Ute would definitely require custom seatposts
due to their one-size geometry. The Big Dummy comes in sizes up to
22". I'd use a Thomson seatpost with that one.
The Nashbar 853 frame you mentioned is lightweight and not suitable
for riders as big as we are.
Getting a garage-sale MTB, especially one with a rigid fork, would be
an easy way to get in the game for cheap. To eke a little more
longevity out of the wheels, you could take them to a local shop to
have their spoke tension raised to at least 100 kgf. It won't make
them reliable in the long term, but it will keep the spokes from going
loose immediately. Older MTBs often have sturdy components that make
them more plausible in your application than a more up-to-date bike
would be.
If your starter bike has a freewheel rear hub, you'll probably bend or
break the axle. This is usually a "ride home" type of failure, often
discovered at a later time. Among commonly available equipment, a
cassette hub is better-- but you are likely to bust up the ratchet in
the cassette body instead of the hub axle. The repair job is almost
the same in either case.
Recent experiences with cassette hubs have convinced me that no
cassette hub, not even the Gusset Jury or similar Woodman Bill
Extreme, is likely to have a cassette body that can handle the stress
of a superheavy rider with low gearing. A face ratchet like the one
in a Chris King hub might hold up better, but that hub is light enough
to give me very little confidence in it.
http://www.woodmancomponents.com/catalog/categorie.php?cat=hub&lang=en&art=hub7
Depending on the terrain you have to deal with, single-speed gearing
might be a good choice for you. Single-speed freewheel hubs with
135mm MTB spacing make the strongest rear wheels around, all else
equal. SS freewheels and chains are incredibly inexpensive, and they
last a lot longer than multi-speed stuff.
Chalo
