Another thread drifted to external frame packs and I came across an old Jansport yesterday and thought it would be interesting to look at it with 21st Century eyes.
I don't know the exact model on this one. I did find a label that identified it as a medium size.
Specs and features:
Tubular aluminum with machined aluminum joints. Approximately 33.5" tall and 14.25" wide. It has two cross bars plus the bag mounting frame. The bag mount mounts via two machined blocks and spring/ball detents. The lower cross bar is fixed at 14.5 inches above the bottom of the frame. The lower section of the frame is a U-shaped section of tubing that completes the rounded rectangle shape of the frame and attaches with the same pins used for the lower attachment of the shoulder straps. There is a top cross bar that forms the upper attachment for the shoulder straps and can be adjusted using sliding aluminum blocks with cam-action locks
The shoulder straps are closed cell foam padding with nylon fabric covering and molded plastic mounts at each end, attaching to the frame with aluminum pins and split rings. The top mount can be adjusted for width by moving the pins to one of two holes drilled in the top crossbar. The crossbar is adjustable to suit torso height. There is no sternum strap on this version, although I have seen other models with one.
There is a 6" tall soft mesh and foam back pad held in place with web straps and ladder locks. I recall seeing back bands that were a plain sheet of mesh, almost like window screen. The back band keeps the user's back from sinking too far into the frame and making contact with the tubing. It hits me at the lower ribs, with the lower edge about 2.5" above the waist belt. It can be adjusted for tension and height; the pack back mounts and the center cross bar form some limitations to the placement of the back band.
It feels like open cell foam with a Cordura-like covering. There are 1-7/8" straps sewn to it that couple in a big side-release buckle. It is attached to the frame sides using a horizontal 3" wide webbing band sewn to the back of the padding. There are no adjustments on this band; it simply slides onto the tubing when the bottom section has been removed. There is a 1.5" webbing strap that runs from the horizontal band and goes around the bottom of the frame and is adjusted with a ladder buckle. There are two 3/4" webbing strap that run from the top of the horizontal band up to the middle cross bar. This arrangement allows the waist belt to slide up and down the frame rails to adjust to the user's torso length.
Coated nylon pack cloth, measuring roughly 21" tall by 13" wide and 8" deep, totaling 2184 cubic inches or about 36 liters. I estimate that the top side pockets are 2 liters each and the lower side pockets look like simple water bottle pockets, so I would add another liter for each, for a total capacity of about 42 liters (I think I'm being very conservative with that). The left top side pocket has panel behind, forming a sleeve to allow long poles to be carried. The main pack body has two panel-loading compartments with zippered openings; the upper compartment is about 31" tall and the lower one is 8" tall. There are no openings between the compartments. There is a flat zippered pocket on the door of the lower compartment with a mesh outer panel. There are four plastic loops on the bottom of the bag to attach web straps to lash on large bulky items like a sleeping bag, pad, or tent. There are also two lash tabs on the top panel for the same purpose. There is a single compression strap across the top compartment with a side release buckle.
The pack bag mounts to the frame using the U-shaped tubing bar that snaps into the top aluminum blocks and runs through a channel sewn in the top edge of the bag. There are also three Velcro straps on each side that simply wrap around the side frame rails. The bulk of the weight is carried by the top bar, much like a curtain.
The pack weighs 59 ounces (3lbs 11oz) total. The bag is 19 ounces and the frame with suspension is 40 ounces (2lbs 8oz). I didn't tear it down further to get the weight on the bare frame or suspension parts.
What is good about this pack:
My general impression is that the design is very simple with a minimum of buckles and hardware.
I think the tubing mount for the top of the bag is genius. By hanging the weight from the top, there is no need for compression straps or reinforcements to keep the bag from collapsing on itself. The rest of the bag mounting (which amounts to about 24" of 1/2" Velcro) is mostly to stabilize it on the frame and the bag simply hangs like a curtain. The pack bag is basically a big cube with a couple panel loading compartments. There is no padding, just the coated pack cloth and one mesh pocket. The side pockets are very straightforward zippered compartments.
The frame is light and relatively low tech aluminum tubing, with no apparently exotic materials or manufacturing techniques. The cam/lock blocks for the shoulder strap top bar are probably the most complex parts to manufacture. There are no welds in the design. Most of the plastic hardware can be found in any catalog. The top mounts for the shoulder straps are the only specialized plastic parts and don't look complex to manufacture.
Although the pack bag is about 46 liters, the carrying capacity extends far beyond that. There is 5" between the top of the bag and the top of the frame and the load could be extended past that. It looks perfect for placing a bear can or a tent. There is an 11" space between the bottom of the bag and the frame bottom. It was common to stow a sleeping bag, pad or tent (or all three) horizontally in that spot.
What can be improved with modern materials and techniques:
Frame materials: I think aluminum has a great cost/weight ratio, but titanium and carbon fiber tubing certainly come to mind. It could be pulled off with square tubing too.
Smaller frame size: Dana Design made an external frame pack where the frame closely followed the perimeter of the pack bag, avoiding the extensions found on this Jansport. If you don't need to lash bulky items to the frame, dropping the top of the frame would clean things up a bit. The current Jansport Carson model has a much larger (80-90L)pack bag that extends to the top of the frame, but the bottom is much the same as the example here. I think that begs for a top heavy load, not to mention encouraging the user to attempt to fill all that space. It can catch on brush and makes crawling under a log difficult. The bottom frame extension does help protect the bottom of the pack and it gets that massive load up another 11"-12" towards picking it up to get it on your back. Some of that space is used for torso adjustment, but not nearly that much. This frame could be shortened 8" without changing the suspension geometry.
Pack bag materials and design: it begs for Dyneema or Cuben fabric. There is the panel/top load debate and I would keep to the panel loading, but with a 1/2 height zippered door and a good stretchy mesh pocket on the lower half for wet gear and daily trail goodies. I would drop the upper side pockets and re-work the lower pockets into good water bottle carriers. I would definitely keep the bag top mounting bar.
Suspension: I take advantage of newer 3D mesh and padding materials and construction techniques, using more ergonomic designs. Waist belt pockets and a sternum strap would be welcome.
Why bother? The external frame design is simple, well ventilated, and very efficient at weight transfer. It lends itself to multiple interchangeable bag designs and is excellent for hauling bulky items like bear cans, inflatable boats, photographic equipment, tools, or scientific instruments. I think smaller packs are better suited to internal frames, but once the 50 liter mark is reached, an external frame can be lighter and handle the bulky or heavy load more comfortably. The ability to adjust the frame to a wide range of torso sizes can make them useful for families and outdoor organizations.
Note: the orange and black rod is a trekking pole to prop it up for the photo: