IN THIS ISSUE:
RUMP Packaging
CSPC: The Poor Man's Composite
Assorted Updates

Art without engineering is dreaming;
Engineering without art is calculating.

(quote is on a coffee mug from Cafe Press; click to buy one)

RUMP Packaging

RUMP packaging is something everybody thinks about at one time
or another in their lives, and overweight BEHEMOTH is no
exception. The RUMP (Rear Unit of Many Purposes) is a
cellulose-core, silicon-matrix, polyester-filled composite
enclosure mounted to the Blackburn rack on the bike's rear --
occupying the entire space a long-distance cyclist normally
devotes to panniers and various lashed-on packs. But all the
usual touring gear lives in the trailer; the RUMP is the second
of three major electronics bays.

A quick overview: the console, the most obvious repository of
high-tech gizmology, is where most of the computers live. It
carries the Mac, the two main DOS systems, the FORTH
bicycle-control processor, GPS board, head-mouse controller,
modems and packet TNCs, diagnostic systems, Audapter speech
synthesizer, Covox speech recognition board, RF datalink to the
manpack, and so on -- in short, most of the computing and
datacomm gear.

The trailer (or WASU) is mostly for radio communications and
power management, and the aft-most third of its volume is a
commbay with flip-down door and operating table. This is where
the Icom 725 HF rig lives, along with the Yaesu 290 and 790
multimode VHF and UHF transceivers for high-power packet and
satellite operation, the AEA ATV unit, an audio filter, SWR
bridge, antenna tuner, smart code keyer, cellular phone, and so
on. Since the lid of the trailer is the big solar panel, this
is also where two of the three main batteries and all
power-management hardware resides -- along with the trailer
control processor to manage data collection, trailer security,
cable minimization, audio routing, power control, etc. The
main antenna mast (BYP, or Big Yellow Pole) mounts on the left
rear corner of the trailer, and the cellular whip emerges from
the center of the solar array.

The RUMP is in the middle, and has become a sort of nexus. The
BIU (helmet) whimsically featured last week plugs in here,
along with the cable harnesses to console and trailer. There
are three equipment bays in the RUMP: port, starboard, and
main.

The port RUMP-bay is where the SPARCstation will live, along
with its hi-res LCD screen, 210 meg hard disk, CDROM drive,
image processing tools, and associated interfaces (CellBlazer
and local network). The starboard bay is the refrigerator, a
thermally-insulated space pumped by a pair of Melcor
Peltier-effect modules -- taking advantage of excess solar or
regenerative braking energy to cool my drinking water and, via
a fluid loop, my head. And the main RUMP-bay is what I've been
working on all week.

This enclosure (an integral part of the whole RUMP, but
effectively a sealed space) carries the MIDI system (a hacked
Yamaha DX-100 as well as a Casio CSM-1 and a Breakaway
Vocalizer, all tied to the Mac via Apple's MIDI interface), the
stereo amps and a pair of Blaupunkt speakers pointing at my
head, the RUMP control processor, taillight controller, all
major security system components including microwave sensor and
UNGO box, paging system, the base unit of the Swintek
full-duplex wireless intercom, an Ampro core-module stack for
Private Eye control (on a LAN to the console), and the RUMP
control processor to hold it all together and handle this
site's audio and serial crosspoint matrices (replicated in
console and trailer and linked by general purpose long-line
buses).

This whole unit is notched out to accommodate a Zero
Halliburton case with solar lid, containing the laptop,
business-band packet system, Icom dual-band HT, and other
communication remotes.

Now you see why the RUMP packaging is such an issue. Here we
have what essentially amounts to a fiberglass composite box on
the back of a bicycle, subjected to rain, shock, direct
sunlight, wrecks, sweat, and other forms of abuse that would
give an industrial-control system designer bad dreams. Yet it
has to protect things as delicate as hard disks and CDROM
drives. (In case you're wondering, by the way, the Sony audio
CD player and related stereo gear will live under the seat in
its own enclosure for easy access... the NEC CDR-35
dual-function CD turned out to be too sensitive for mobile
audio use without extensive cushioning.)

The floor of the main RUMP-bay is fiberglass-covered plywood,
and it is bolted with stainless 1/4-20's down into an aluminum
plate TIG-welded to the Blackburn rack. A baseplate of .062
angle-stiffened aluminum sheet is mounted to the floor via four
shockmounts from Lord Manufacturing. This is slowly
becoming loaded with equipment, including one of the bike's
three main Sonnenschein batteries (12 pounds) to allow
uninterrupted system operation when on local rides without the
trailer.

But the internal stuff is pretty easy. The hard part is
keeping the water out, minimizing road noise amplification, and
allowing at least a minor accident without having to do nasty
fiberglass surgery. Everything is gasketed, of course, a
non-trivial problem in itself -- usually with EPDM rubber
strips glued into all critical closures. Gasket compression on
the lid is achieved with Southco soft latches, lovely rubber
assemblies that allow all sorts of imprecision while still
looking clean and professional (Southco is at 610-459-4000).
These are mounted with careful attention to the dangers of
point-loads in fiberglass, and I machined in some adjustability
slots with the aid of trusty Cecil.

It's a bit hard to describe all this without pictures (which is
why you should immediately hit a psychological control-S and
send a $15 check to Nomadic Research Labs for the print edition
of all this), but the manpack mounting introduces special
problems of its own. The idea here is to be able to grab it in
a single quick motion whenever I leave the bike, and have with
me a complete communication link back to the server, cellular
gateway, security system, audio monitors, speech I/O, and so
on. This will let me turn my back on BEHEMOTH now and then to
think about something else... but still be in touch.

Two of the original Zero aluminum feet (which are noisy and
rough on surfaces anyway) have been replaced by rubber ones,
and the other two by little Z-shaped brackets cushioned with
Permatex Color-Guard (a rubber dip coating often used for tool
handles). These are inserted into slots in the assemblies that
make up half the RUMP-lid mounting system, the case is dropped
onto its foam nest, and a single soft draw latch is used to
cinch it down.

The port and starboard RUMP-bay doors are a real problem, not
yet entirely solved. The original plan was for flush
fiberglass doors, but the hardware overhead required to achieve
reliable gasket compression was absurd. The current plan is to
mount a fabric bulkhead with riveted aluminum strips, with a
hooded zipper providing flip-down access to the internals.
This also allows addition of a pannier-style outer pocket,
which will help absorb shock in accidents. Fiberglass ALWAYS
loses in an encounter with concrete.

Finally, there is the problem of cables... entering the RUMP
just behind my shoulders and leaving it down by the trailer
hitch is the bike's cable harness, a rather bulky affair of
various wire types all terminated by LEMO environmentally
sealed connectors. Again because of point-loading problems,
these headers will be aluminum panels gasketed over large
cutouts in the fiberglass. Other fixtures that don't impart
significant stress -- like speakers, the taillight, and so on
-- require no special attention beyond sealing.

It's a bit difficult to describe packaging details in a
text-only publication, but I thought you might enjoy a bit more
physical overview. I get occasional letters asking what this
looks like (and yes, there are two projects underway now to get
image files that can be electronically distributed to anyone
interested -- stand by!).

Back at the beginning of this article, I mentioned that the
RUMP is a cellulose-core, silicon-matrix, polyester-filled
composite enclosure. If you wondered what on earth I meant by
that, read on.......

CSPC: The Poor Man's Composite

This article about cardboard-core fiberglass construction has been updated
and moved here.

Assorted Updates

In the continuing saga of power management, I have an update
from last week's lament. You may recall that I was complaining
about finding a simple, standalone solar charge controller for
the sealed lead-acid batteries (one that works even if the
computers are all down). I had objected to the Sonnenschein
pair's uneven current distribution and the SCI's dark current.

Thinking again, I've decided to stick with the SCI (the
Automatic Sequencing Controller from Specialty Concepts --
818-998-5238). The dark current is 5.6 mA, which will kill my
batteries in about 8,000 hours of dark storage (assuming a
perfect world, lumped constants, and no self-discharge...).
The unit is actually quite clever, and the fix for the
oscillation was to simply eliminate the schottky diode and let
it sit on the battery bus where it belongs. It now switches
neatly and quietly, harmlessly shorting the solar panels when
the battery is at or above setpoint (and it doesn't care about
the presence of other charge sources).

In ham radio news, I did another Outbacker test last weekend:
worked a sked on 40 meters, along with a nice handful of
stateside stations, Japan, and Chatham Island on 10 meters. It
is very satisfying to do that bicycle-mobile, since one of the
design specs for this whole thing is achieving near-100%
probability of making contact with someone, somewhere, at any
time from anywhere. Piece o' cake.

Back to a night of packaging and wrestling with balky
adhesives...

Cheers from the bikelab!!!