[Stenlite-users] Stenlite-users reviews from Hellhole

[Brace, Gordon]

Dave,

Below are three reviews of your light from the first weekend of the Hellhole
survey season.  As a rule: Everyone that saw it, wanted it.  I think you
have a winner here.  Small, light, and bright, what every caver has dreamed
of in a lighting system.

Gordon


Review from Dan Zinz:

StenLite: Both Rick and I were using the Stenlites borrowed from Gordon.  I
noticed on Rick's light that it was exceptionally bright on 2 power.  I
started using mine about halfway through the trip.  I was very impressed
with the amount of light produced.  Also the construction is good; it seems
very heavy-duty in a lightweight body.  I think that this is the next
generation of lights.  It makes my Princeton Tech hybrid look like a child's
toy.  Considering the weight, size, and amount of light produced, throw away
your TAG lights, throw away your Wheat lamps, and for Peter's sake throw
away your carbide.  Get a StenLite.  It is an expedition caliber light for
expedition caliber caving.


Review from Rick Royer:

I tried the StenLite this past weekend.  I liked the light.  It has 2 very
bright LEDs (Gordon says they are 3 Watts).  I originally planned on using
my carbide light but tried using the Stenlite for the entire trip.

Pros:
- Very Bright - I normally ran it on setting 2 of 4 and I could see a long
way.  I rarely used the brightest settings and in small passage would change
to the lowest setting.  It is bright enough that you cannot look directly at
others during conversations.
- Uniform light - no light rings.
- Very small - about the size of a Tikka.
- Clip mount - for easy on/off for lighting survey stations, reading
instruments, and peering in small leads.  I wish all electric lights were
clip-mounted.
- Small battery pack - 2 AA Lithium? battery pack - I used the Tikka strap
and duct tape to attach it to the back of my helmet.  (I do not like my 4 AA
Duo battery pack since it gets dragged off of my helmet in tight spaces).
- Battery life - lasted for the entire trip with no sign of dimming (Gordon
says 20 hour life on 2nd? setting).
- Nice Switch - easy to change between settings via "feel' with the light
still on my helmet.  (Is there a "lock" so it will not come on in a pack?).

Cons:
- Not tiltable - made reading the map harder.
- Magnetic - the light is magnetic but that was not a problem since I always
unclipped it to read instruments.
- Small coiled wire to battery desired - The cable was mostly long enough to
still wear the helmet and all light stations.
- Not available yet - Gordon only had "prototype" versions.
- Cannot mark stations - Nothing beats a carbide lamp for marking stations
though flagging is good for labeling and long-range visuals.

I generally do not like electric lights but liked the Stenlite.   I would
like to long term test the Stenlite and would probably buy one.


Review from Ed Devine:

Subject:
In-cave test review of StenLite S7 caving light with rechargeable Li-ion
battery pack (http://eludium.stensat.org/StenLite/fact-sheet.html).

Summary:
I had the opportunity to "test drive" the new dual-high-output-LED StenLite
caving light in combination with a lightweight rechargeable Lithium-ion
battery pack on the last Hellhole survey trip (17-hour trip).  As
configured, the lamp consists of a very compact (approx. 2.25 x 1.5 x 1.4)
headlamp connected to a tiny, ruggedized (presumably waterproof) battery
pack (roughly similar in size to 2 AA batteries) by a roughly 15-inch length
of cord with a removable connector in the middle.

This is probably the best caving light that I have ever used.   I have very
many pro comments and only a few cons.  

Lamp description:
This lamp is well-engineered, well-made, innovative and high-performance.
It is a high-end lamp all machined aluminum and stainless steel parts; very
rugged and durable.  The design has clearly been well field-tested.  This
lamp provides for four different, regulated levels of light output adjusted
using a simple, obvious, rugged switch.   These light levels include "low",
which it is claimed will run the light for 3 days, "medium" for 20 hours,
"high" for 5 hours and "Turbo", at 4-7 watts, which will run for 90 minutes.
The light is regulated, so presumably it will provide for constant light
output at each setting provided that battery power is available.  A Li-ion
battery provides extremely good power-to-weight performance.    The lamp has
two high-powered LEDs; I am not certain of the wattage, but I would guess
2-3 watts for each.  The lamp has thermal regulation which means that when
used in a high-power mode, it will down-power to a lower mode if it
overheats.  It is not intended to be used for long periods at "Turbo" mode,
so this overheating can apparently be expected to occur after just a few
minutes.  Experienced cavers do not usually require extremely bright light
for long periods of time, so this is probably OK. (In fact, bright lights
can be problematic as they tend to blind other cavers in the party)   It has
an indexed rotary switch built into the body of the light, with a big,
obvious knob - the five switch positions range from off at zero degrees
(straight down) to "Turbo" at 180 degrees (straight up).  Each switch
position is indexed so that you can feel the change from position to
position, even while using gloves.  This switch and knob appear to be all
stainless steel (or similar corrosion-resistant metal), rugged, mud and
waterproof.  The rotary switch apparently activates a magnetic switch, so
the electronics are internally isolated.

The two identical LEDs are mounted behind different protective lenses - one
is a clear lens, which provides for a spot light from the LED and the other
is a Freznel lens, which provides for a widely-dispersed flood light.  Thus,
the resulting pair of LEDs, which cannot be independently controlled,
provides for both a spot light and a uniform, dispersed light.  Rather like
carbide light and very functional for seeing distant objects while retaining
good all-around light.

The lamp body is machined from a block of aluminum with the lens and
supporting ring held by six screws.  The screws are beveled to provide for a
clean profile that will not catch on things.  The lamp body appears to be
anodized to protect the lamp from corrosion and abrasion.  Corners are
reasonably smoothed and rounded to prevent abrasion, injury, and lamp wear
and tear.

The lamp bracket is apparently stainless steel and functioned very well - it
fit my helmet bracket very cleanly, but has a well-positioned tang that
secured the lamp adequately but was not difficult to remove.

The lamp cord may be the weakest component of this lamp.  The cord consisted
of a length of zip-cord exiting from the lamp body at 90-degrees with an
insufficient rubber strain-relief.  These are probably the hardest
components to design for devices such as these.  The requirements of a
flexible cord conflict with the need to prevent wires from flexing and
breaking.  A poor cord will lead to wire cracking and sudden lamp failure.

Test description:
Our caving was not difficult, although the trip was fairly long.  I mostly
used the light at low setting but very many times turned to the higher
settings, including "Turbo".  Most of our surveying was big-room survey
where it is necessary to clearly see details 20-50 feet away.  This is very
challenging survey, from a lighting consideration, because the sketcher is
constantly looking around at details, for which very bright light is needed,
and then peering into a sketch-book where that bright light will blind him.
So this simple, effective light switch was a real pleasure in that it was
quick and easy to vary the light to just what was needed.

I have never liked caving with lights that require a separate battery pack
on a cord because I am constantly taking my light off the hardhat.  When
traversing complex cave floors, such as breakdown, I like to hold the lamp
low, at full arm extent, to create shadows so that I can see rocks, holes
and other features.  So before the trip, I carefully duct-taped the battery
pack to the side of lamp so that the lamp and battery were effectively a
single unit.  I had to tape the battery on at a funny angle so all the
switch positions would be unobstructed, and it looked very ugly and weird
(like a crumpled ball of duct-tape), but it worked great for the entire trip
this way and gave me no problems at all.  The combined weight of the lamp
and duct-taped Li-ion battery was very reasonable and comfortable.  This is
my biggest recommendation with this light - devise an integrated lamp and
battery or devise a battery pack that installs onto the lamp body.

Observations:
The quality of the light was excellent.  The combination of the spot and
flood lights provides for a very usable quality of light; similar in
dispersion pattern to carbide light.  The "Turbo" mode stunningly
illuminated the 150-foot by 100-foot room that we were surveying when that
level of light was needed.  It was fast and easy to precisely toggle between
"low" setting and "turbo" setting for sketching (alternately peering from
dim darkness to a blinding white page).

The lamp has a fixed bracket.  Although the angle of the bracket worked well
with my hardhat, some sort of efficient pivot or other adjustment would seem
a necessary enhancement.

There was some concern before the trip regarding possible effects of the
magnetic switch on the operations of a survey compass.  Because we were a
two-person survey crew, I was sketching and reading compass.  Unfortunately,
I forgot to check if the lamp interfered with the compass - I used my usual
method of holding the lamp a foot, or so, above the compass, which should be
a sufficient distance to prevent possible problems.  This is another reason
that I do not like battery-pack equipped lights - they are hard to remove
for compass reading.

Suggestions:
Integrate the battery onto the lamp body or provide a battery pack that can
attach directly to the lamp.  Weight is not an issue for this combination of
lamp and Li-ion battery.  The usefulness of this lamp would be greatly
enhanced for many applications as a single, integrated unit.

Provide pivot capability for the lamp bracket.

In general, improve heat management to extend the "Turbo" burn time.  Maybe
heat fins on the lamp?  Maybe some sort of liquid coolant?  I did not test
this option, but am commenting based on viewing the website.  I can see this
being a potential problem when the user has overheated the lamp and still
needs bright light.  The lamp may unexpectedly dim down when bright light is
needed.  I also think that there are potential users, such as cyclists, who
would really like to continuously run on "turbo" setting.

An elastic head band (or possibly "mouth" clip option) to use this lamp
off-helmet and hands free (i.e., for camp use, car repair, etc.)

The lamp is dark-colored.  Put reflector tape or some other reflection
surface on the lamp, at different locations, so that it can be seen if
dropped down a pit or breakdown.

Improve the strain-relief where the cord attaches to the lamp.  Possibly
improve quality of cord and plugs.

Include an emergency backup light.  A single, small LED and Lithium
button-battery, with a separate switch, on an independent circuit as an
emergency backup light could be built into the overall lamp body.  I have
integrated such circuits into several lights that I have built, and have had
to use them.  The main light can fail due to such unavoidable situations as
the battery running out or cracked wiring where the cord attaches to the
lamp body.

Provide a warning label, right on the lamp body to warn survey-users about
the magnetic switch.  (This needs further evaluation)

A light rubber jacket or coating around the lamp may improve ruggedness.

Addendum from Ed Devine:

Several more comments regarding the StenLite ...

Ditto Rick's comment regarding the need for a switch-lock.  As configured,
this lamp would be *very* prone to accidental turn-on in the pack.  This is
also a *safety* concern when a light has this much power (heat).

Also (from my video experience where I use dual 50-watt lights) for
high-powered lamps, it is essential to have a *fused* battery pack and/or
lamp.  If there is an electrical short (or if the lamp is inadvertently
turned on) it can get dangerously hot, quickly.  If the StenLite Li-Ion
battery is fused, it is not obvious (or accessible to change the fuse).