Dale, Take a look at these frames. They are what Mountain Hardwear is using on their EXODUS Backpack series.

Cruiser Frame:




Motive Frame:



These Packs are on a "Sales Hold" for a hip belt problem I have been told. I have had a real close look at both and have had them both on. But now they are gone. I would like to have one of each to play with.

I agree about the terms being difficult to work out. I was struggling most to describe the forces and flex directions. If there's some other term in particular that's troublesome in my posts, please just point it out and I'll try to clarify. I hope the sheer length of these posts won't be offputting...I'm trying to give you a lot to go on now to help you avoid problems and get the best results fastest, so the project gets the most it can out of my limited available time. I know it's an awful lot of text for just now. I'll also keep editing to try to make the reading easy and keep hoping it's not overwhelming.

Let me just hit a few things and see if that's helped enough to reduce any confusion over what I said enough to make remaining bits more approachable. If something's impenetrable, please ask for clarification.

The "wings" I think we've been using consistently. Someone has previously noted that Bill has made his sheet metal ones strongest in the dimension they need to be strongest by using the sheet material, the main strength of which is aligned vertically when carrying the pack...and as gravity pushes the pack downwards, the mounts on the hips resist towards the forward extremity of the wings, where the greatest leverage would be had in bending them upwards if they were too weak; that force can be called a "bending moment". These wings can also effectively form a type of "rib" relative to the plane of the main backpack frame, which is trying to fold under weight, and additional, lower ribs running along the vertical sides of the pack frame and facing front to back like the wings are can add stiffness to the packframe; these ribs can be on either front or back of the frame depending on what clearances require, but it the ribs can be placed so that the largest forces compress rather than stretch them they will provide the needed strength with the least material.

Note how on the Stephenson frame the wings tilt upwards; this is partly to exploit the compressive strength of the tubes and joints, avoiding putting all the force into flexing the joint as would tend to occur if the tubes met the frame at 90 degrees...these parts are stronger in compression than in flexion.. So if the base of the wings (the edge where they attach to the frame) is lengthened, they form a longer rib on the frame, strengthening it more in the main direction we're worried about the frame flexing (for which we should probably come up with a short discriptive name, I think). And if the base of the wings is mounted higher on the backpack frame, at a greater angle up to the point where the wings are most purely compressed, less material will be required to make wings strong enough to hold up to the forces from carrying the pack. This tilting of the wings is a move from cantilevering towards triangulation.

The strongest structure in resisting a simple bending moment is typically called the "I-beam"...it's shaped like the most common of building girders, or a letter "I" if cut in cross-section. This I-beam form is a useful basis considering alternative structures, and mechanical engineers often consider how some 3-dimensional form approximates an I-beam when trying to estimate its strength. Imagine a simplified version of hexcore, with two skins around cores that are just a bunch of parallel strips. In terms of resistence to a bending moment along the length of those strips, the planar core board can be considered to be a bunch of I-beams, or nearly ideal for resisting that bending moment with minimum materials if the type and amount of materials and their attachment is ideal.

The resistence to bending moments of an ordinary round tube can be considered as a bunch of partial approximations of an I-beam; the tube's advantage over the I-beam for some applications is partly in resistance to twisting, but especially in resistance to bending in more directions....but it's not nearly as strong as an I-beam in the direction that the I-beam is strongest.

Now the "raised ribs" "like waves" that Dale just refered to are something we often see in molded products as stiffeners due to their being relatively easy to mold in and approximating I-beam reasonably well along their length while adding additional stiffness in a few other directions due to their curved forms...it would indeed be hard to characterize those other directions in simple language, and it's not easy to calculate either, which is one of the reasons structural engineers tend to use old familiar forms, and when they build something out of composites to proceed empirically, that is, by building and breaking things to test them. So we could call those "wave-like ribs"? Seems descriptive. They are also somewhat like like half-tubes.

Now, "triangulation", which I've used as shorthand for "triangulation in space frame structures" or some such term. The single word "triangulation" would make it hard to do a simple Google search since the term is used in so many other ways in geometry, surveying, politics, and so forth. The main idea of triangulation in structures is to exploit the better strength of structural members (such as tubes) in compression as opposed to flexion. Think of tubing racecar frames: here's an early example: http://www.utahlotusmuseum.com/id267.htm. Notice how in some of the frames' rectangles, tubes are added that break the rectangular shapes into triangles. This is the "triangulation" of which I speak. A rectangle easily collapses when pushed on a corner, as when dropping an underbuilt loaded external frame pack on its corner when lowering it to the ground. The lowest-material way to stop that collapse and keep the rectangular shape (which may be valuable for other reasons) is to brace the corner of the rectangle that you plan to drop it on to the opposite corner of the rectangle, thereby using the materials in their strongest, compressive dimension.

Why, you might ask, didn't the external frame designers of old do it this way? Why did they make ladder frames instead of triangulating? There are probably several reasons:
1) they weren't mechanical engineers and there weren't as many space frames around to notice when tubular backpacks got going;
2) they weren't hyper-concerned about getting the lightest possible structure;
3) the difficulty of getting or making non-90-degree tubing fittings was too much, as was fishmouthing tubes at other than 90 degrees,
4), with a simple tubing structure, it's hard to get the tubes out of the way of the back with simple bends if you run them in an X-pattern across the back;
5) a simple ladder structure gives you a very simple place to mount straps and such; and
6) potential buyers didn't have superior alternatives.
In fact, later designs did increase triangulation in certain areas. The angling of the Stephenson wings is in fact an example of triangulation of a sort, and it appears in parts of other frames too. Using a frame sheet is also triangulation; it just wastes some material since certain parts of the sheet take more force but the sheet used is typically all the same thickness; you could cut holes or thin the sheet in some particular areas without losing any strength.

Now we have CF layups, which give us more design latitude than do tubing structures. We can put the material pretty much where it needs to be to get maximum strength where it is needed, and not make it stronger than it needs to be where it doesn't need to be strong, just within the constraints of keeping molding simple and not interfering with the spaces dedicated to such items as arms and packbags. We can also align the the fibers so the structure is strongest against the forces it commonly encounters.

The Mountain Hardware (MH) frames depart from the rectangular ladder structure typical of most older backpack frames. There are some disadvantages to that departure, but also advantages. Let me note a couple of disadvantages, so that if we move away from the rectangle we can be more reminded to compensate for those weaknesses.
1) When you set a rectangular frame down, you can use the bottom corners of the frame to take the abuse and save your packbag.
2) The "square" bottom of the frame can help balance the pack when it's standing on the ground, and this can fairly readily be exploited to approximate a chair.
3) There are obvious points on rectangles to mount the gear that attaches packframe to human body. Likewise for packbag mounting.
4) More strength may need to be built into the waistband assembly than with a rectangular frame since attaching the waistband to the corner of a triangle at one point creates a longer lever arm between the juncture of frame and waistband assembly. Long lever arms in cantilevered structures like this require more materials to retain strength and adequate stiffness levels.

Advantages:
1)Despite disadvantage #4 above, mounting the waistband assembly to the bottom corner of a frame triangle shifts pack structural weight to a place where the body can probably most easily handle it: around the waist.
2) Again, despite disadvantage #4 above, this mounting arrangement puts a joint right about where I think we'd want if if we need to build some mobility into the joint in order to replicate biomechanics...right around the upper lumbar region. We'd probably want to make this joint stiffer than biology in the fore-aft flexion/extension motion (Dale's "crunch"), but perhaps leave the top and bottom parts of the pack free to rotate relative to one another in two other dimensions: a) around the vertical axis; b) so the left hip can move up and right hip down (and vice-versa) while the upper pack frame floats along without going up and down on with the hips...similar to the independence of our hips and upper bodies. This can be relatively easily accomplished with two axles. I think this is aligned with Dale's 05/18/2006 13:26:15 MDT post but I'm not too clear about the pentagons he mentioned and I've also been trying to get to some rotation on the vertical axis. I'm seeing triangles because I see the forces that way but pentagons and such might give a better perimeter for packbag mounting than a triangle. But pentagons don't self-brace to the extent triangles do.
3) The MH structure seems to follow the triangulation I was speaking of with hip motions relative to shoulder motions...it's basically an "X" shape connecting hips to shoulders.

Compensations for disadvantages:
1) If need be, projections from the frame could be added to absorb forces when the pack is set down roughly, and lighter-duty projections to the ground could be added (or deployed when needed) to make a chair.
2) Careful design can take care of the mounting points for the gear that attaches a non-rectangular packframe to the human body. Likewise for packbag mounting, one would hope.

Improvements over the MH frame:
1) Replacing the hipbelt assembly with a fitted CF structure might save quite a bit of weight and need for (as much) padding. A rigid structure lets us distribute the weight broadly to reduce stress on the body, and concentrate it where we might want to concentrate it a bit (because, e.g., certain parts of the pelvis are easier to get a grip on than others and/or have a preferable combination of bone near to the surface, not too many pain nerves, and so forth.) The waistband shapes they are using might be a little more cantilevered than is required by the single point of attachment to the upper frame; if in building a full-sized model around a specific human body clearances and triangulation are kept in mind it looks to me that a CF layup would allow a more efficiently triangulated hipband structure carrying forces more directly from the hipband to the joint at the upper lumbar.
2) The upper part of the MH frame looks at a glance to have been fairly carefully minimized in its major form according to ordinary structural principles. Using lighter/stronger material would certainly lighten it. Also, they may have used more material than is needed in order to simplify construction, whereas if we look for opportunities, e.g., to use ribs or double-skinned cores instead of sheets of constant thickness if they use something like that, we could save weight.

Questions:
Since the zoom function in my browser is temporaily disabled and I haven't had time to do the necessary computer maintenance, I'm only seeing small pictures of the MH frames. Are those thin verticals along the outside edge simply straps, or are they rigid? This same zoom limitation makes it a little hard for me to understand quite where the MH parts lie on the body and how stiff they might be in certain sections.
Also, I'm not very clear on how they mount their packbags.

Time limitations are likely to keep me from sorting out drawing issues soon too. I don't normally draw with a computer so I'd have to set something up, and I suspect that the time required would be such that we wouldn't get the best out of me on the other issues fast enough to help set directions for projects now.

Edited by BobOne on 05/19/2006 02:24:55 MDT.

Does anyone have a source for high-density thermofoam that might be used for padding? This is the stuff that molds under your body heat to distribute load better than regular foam. Sometimes called "memory foam".

Also, racecar seats sometimes use expanding foam to custom fit seat to driver. A typical procedure (from Carroll Smith's books as I recall) is to put the expanding foam in plastic garbage bags and quickly put the driver in the seat atop the bags till the foam sets up, then remove the bags, then trim, mount and cover the foam. This might be used for backpack pads as well: support pack at proper distance from standing body; apply foam in bags; trim, mount, and cover foam.

Terms and Ideas for a New Pack Frame:

BobOne, Thanks for taking the time to address Term/Words/Ideas question. The light in my brain is now on at a much brighter level. You obviously have thought a lot about this frame subject. I have several questions about your background but will not ask them at this time.

I am a little concerned about getting all these ideas in one neat light package (model) and then being able to make it. The first few frames may be just a "mule" or test bed if I can borrow an old term once used by
"Zora Arkus Duntov" I sat in this car for a few minutes, once, many years ago.

I want to talk about a new question as I think we are ready to get started on actual designs. In my frames I first tried to second guess the Max weight I wanted to carry with the frame. In a Super Ultra Light gear load of 7 to 12 pounds or less it doesn't take much frame to handle this weight. The frame design for me was more to try and get a space between my back and the pack bag. This window of sorts would keep my back cooler in warm weather and has a good benefit even in colder weather. There is a lot more to this idea that can be address later if necessary.

I think we need decide what our "Frame Design Goals" are at this time so we have something to focus on. They don't need to be in any necessary order of importance's but should be looked at as a group. Here are a few and I expect this list to grow. When we have a bunch we can decide which ones we want to focus on.

Frame Design Goals: (these are in my words and the exact wording can change)

1. A frame that pushes back from the back so it has a space (window) between the back and the pack bag. This feature was one of my main goals in the pack frames I make.

2. Frame Carry Weight: This can be several different weights and can be several versions of the frame so we can carry light loads and or heavier loads. This can be more than one frame based on the same general design ideas.

3. Frame Weight: What is the Goal weight for the frame?

4. Etc, Etc, Etc


The "triangulation" term was my big question. I thought this was what you meant and the Lotus article was all it took. I am a great Race Car and Hot Rod fan and have been since I was about 13. The old "tube" frames were a great idea.

The small pictures of the MH frames are the only ones I could find. I don't have a way to Re-size the pictures but it could be done with something like Photoshop. I have an older Mac with PhotoShop on it but the hard-drive died. The version of Photo Shop is old and does not work on my new computer and the new Mac OS. I was going to take some pictures of the frames at my local store but they have sent them all back. The pack bag attaches at the top of the frame with a small pocket like thing sewn onto the bag and slips over a thing?? on the frame. then the pack bag has a strap at the bottom of the frame on each side that pulls down on the bag and holds it under a little pressure. The bags come off and on easy and quick.

Some random pictures of the MH Pack:






These are a few pictures of a frame I started about a year ago to carry a heavier load. It started to get a little complicated and heavier than I wanted and I stopped working on it. My idea was to replace the Aluminum parts with home made Titanium parts. You may notice a little crude attempt at "triangulation" though I didn't know the word at that time.

Edited by bfornshell on 06/01/2006 23:21:27 MDT.

That makes me feel pretty good-- great minds think alike, eh?

Looks like MH is using stressed "wands" like some of the Dana packs.

Bobone,

>>racecar seats sometimes use expanding
>>foam to custom fit seat to driver. A
>>typical procedure (from Carroll
>>Smith's books as I recall) is to put
>>the expanding foam in plastic garbage
>>bags and quickly put the driver in the
>>seat atop the bags till the foam sets
>>up, then remove the bags, then trim,
>>mount and cover the foam

I did this once and it worked well. It gets quite warm sitting there waiting for the foam to solidify. I used a two part urethane foam used by boat manufacturers for flotation.

For a small project like this I would recommend the rigid types now available in spray cans.

Robert

I want to play with some of that foam again soon to see if it will help keep traffic sounds from passing through hollow-core doors here. There's apparently both hi-expanding and low-expanding types available in spray cans, with the latter being the type you'd use on hollow-core doors so as to not blow the panels off. I haven't used expanding foam in a really long time (last was 2-part boat foam, I think) and it would be a nice thing to have in the tool kit, I'm sure.

Wands at the sides, eh? For the mobile joint to work, they'd have to be somewhat resilient, I suppose, or would need to float. It seems like they'd help keep the packbag under control, don't you think? I guess wands might be inserted through loops sewn into the packbag then attached top and bottom, obviating packbag straps.

I'd think the first pack to build might be one directed at very light loads...then go out and use it until it breaks under measured loads, working upwards and refining to make things stronger only where they tend to fail in use and maybe lightening some in areas where there is no problem. But it might make sense to also have a second, somewhat heavier frame that could be carried as luggage on the first so that when the first one fails the second one can get the tester home. One might work upwards this way until some tester is willing to carry 65 pound loads long enough to develop a light reliable frame for those loads...this is just because I'm not imagining I'll ever see reason to attempt more than 65 pound loads again personally, someone else might want more. The military might be interested in providing testers around this load range?

I also like the ventilation of an external frame pack. In fact I've wondered about ways to use forced-air cooling here at times. There is a bit of a bellows effect just with the bag and body moving a bit relative to one another, and there's probably some slight chimney effect as well.

Another note on joint placement. The likely best height for a single mobile joint is at the intervertebral space between the 12th thoracic and 7th lumbar vertabraes. This is the most mobile joint in the region that's near to the lumbar which are more limited in motion in order to provide stability. Going above this point with the joint would, I think, tend to restrict motions more than we'd prefer as it would more immobilize joints that normally can move. Going much lower could tend to concentrate those motions at joints that don't have as much freedom to move as those in the thorax, which could overburden them. You can locate this spot with your thumb in your mid-back while standing as the most prominent convex bony point.

Also, I wonder if for some future project there's enough motion at this pack joint for a power take-off for electrical generation. If we used axles it would be relatively easy to get some of the hip up and down motion off. If we used a ball joint (limited in the crunch direction, presumably), it might be harder to extract power; it might be easier to find an off the shelf ball joint that could be adapted to simply get the desired motions, but I'm not sure.

Edited by BobOne on 05/19/2006 14:38:34 MDT.

"I want to play with some of that foam again soon to see if it will help keep traffic sounds from passing through hollow-core doors here. There's apparently both hi-expanding and low-expanding types available in spray cans, with the latter being the type you'd use on hollow-core doors so as to not blow the panels off."

Even the low expanding stuff could be ummmm.... interesting... with a door-- there's so much surface area to push on, vs the glue line on the door. Drill through the top first and see if the door has cardboard spacers in it. I'd buy some nice noise-cancelling headphones myself :)

Back to the pack-- I was thinking of simple straps or elastic cords to limit the travel of the joint. Some Sprectra Aircore would do the trick.

The wands I was referring to were used by Dana as a frame piece. The top of the wand was fixed to a plate/crossbar at the top which was also the attachment point for the shoulder straps. The bottom of the wands ended in pockets in the corners where the waist belt was anchored. It was overbuilt but capable of bearing loads that I would laugh at now. With all the hardware and heavy fabric a 2500ci pack was well over 4 pounds.

I am reposting this for input on "just" the Frame Design Goals. I really didn't expect to get many replies to the project and thank those that took the time to join in on Design comments and Material suggestions. I even thank Jim though I think he is a bit of a joker.

I will edit this post to update ideas as they are suggested and will start with what we have to date.
===============================

Frame Design Goals: (the exact wording can change as can the number).

1. A Frame designed that pushes back from the back so it has a space (window) between the back and the pack bag for ventilation. This feature was one of my main goals in the pack frames I make. This gives a "Moisture Management" breathing space for upper body garment material to really do there thing.

Things to try:
1-a. Some ways to use forced-air cooling.

1-b. Test to see if there is some slight chimney effect as well.
(NOTE from Bill)
On my packs that do push away from my back I did get a good breeze through the open area. This was tested on several hikes here in Texas last summer when it was about 100 degrees F.

1-c. Wands at the sides, eh? For the mobile joint to work, they'd have to be somewhat resilient, I suppose, or would need to float. It seems like they'd help keep the packbag under control, don't you think? I guess wands might be inserted through loops sewn into the packbag then attached top and bottom, obviating packbag straps.

(NOTE from Bill) Point me to something that shows what you are referring to when you say "Wands" . I think you maybe talking about the up-right tubes or cross tube on the MH frames? If this is what you are referring to I used something like the side tubes on my recent frame. The one I call my Exodus Clone.

1-d. Another note on joint placement. The likely best height for a single mobile joint is at the intervertebral space between the 12th thoracic and 7th lumbar vertabraes. This is the most mobile joint in the region that's near to the lumbar which are more limited in motion in order to provide stability. Going above this point with the joint would, I think, tend to restrict motions more than we'd prefer as it would more immobilize joints that normally can move. Going much lower could tend to concentrate those motions at joints that don't have as much freedom to move as those in the thorax, which could overburden them. You can locate this spot with your thumb in your mid-back while standing as the most prominent convex bony point.

2. Frame Weight and Frame Carry Weight: This can be several different weights and can be several versions of the frame so we can carry light loads and or heavier loads. This can also be more than one frame based on the same general design ideas.

2-a. SUL Version ?? Pack Load ?
2-a-1. The first pack to build might be one directed at very light loads....then go out and use it until it breaks under measured loads, working upwards and refining to make things stronger only where they tend to fail in use and maybe lightening some in areas where there is no problem.

Next it make sense to also have a second, somewhat heavier frame that could be carried as luggage on the first so that when the first one fails the second one can get the tester home. One might work upwards this way until some tester is willing to carry 65 pound loads long enough to develop a light reliable frame for those loads...this is just because I'm not imagining I'll ever see reason to attempt more than 65 pound loads again personally, someone else might want more. The military might be interested in providing testers around this load range?

2-b. UL Version ?? Pack Load ?
2-c. Something in-between ?? Pack Load?
2-c. Heavier ?? Pack Load ?

3. I wonder if for some future project there's enough motion at this joint for a power take-off for electrical generation. If we used axles it would be relatively easy to get some of the hip up and down motion off. If we used a ball joint (limited in the crunch direction, presumably), it might be harder to extract power; it might be easier to find an off the shelf ball joint that could be adapted to simply get the desired motions, but I'm not sure.

(NOTE from Bill)
When that pack that could generate a bit of electricity first came out I did a search for small generators that might work with the up and down motion from something built into the frame. I found several little generators that might be adapted to a frame set-up. I was looking for a way to power my "Backpackers OnStar" device. I had several ideas for a better system but it required the development of some really small hardware. There are better ways than the frame to generate some electricity from motion. I don't think the hardware necessary has been developed or is available. The idea I have may never even been though about. How much battery power do you want? The small "off the shelf" generators didn't put out much juice. Solar might be easier if you can depend on enough sun light.


4. Etc.

5. Etc.

6. Etc.

WANDS / STRUTS / VERTICAL LATERAL ARCHES
Wands are the term Dale used, I think for the largely-verticals at the outside edges of the usual location of a rectangular packframe. I can't see the MH pictures well enough to see if they have something like that, but it makes sense to have such verticals to give structure to the packbag once you've taken the primary loads into an X-shaped central structure, like what MH also does. Aircraft terminology might suggest "struts" for these items.

The simple way might be CF tubes. It might be nice to build some CF arches for this to get them to optimal strength and stiffness and exploit the strength of an arch to resist the packbag coming forward against the body, as well as to fit the "arches" (which might thus be more complex) so that they will clear the back of the body well but still let the weight carry as close as good ventilation allows. Seems like the they might be anchored at the top and float at the bottom (allowing free hip movement, if only to get noise associated with the floating arrangement away from the ears. Solid anchoring at both ends could also work if the pieces are flexible enough to allow the hip motion to still work. In a model without the mobile joint, of course, floating or flexibility would not be necessary.




POWER
How much power do I want...that's hard to answer off the cuff (at least once we get off talking about ruling the known galaxies)...I'd need to go look at rated battery capacities and lifes for current portable computers and phones. The basic idea is to be able to walk around part of the day then use a computer, phone, GPS, and some lighting the rest of the waking hours; some partial functionality less than that would also be useful. Last time I caught up, solar didn't have the conversion efficiency needed to collect much power by walking around with solar cells, but if I recall correctly, if there were some really solid improvements in conversion efficiency there might be enough sunlight hitting the body in some circumstances for it to work out. It would be nice to be able to kick back when you get where you're going and still have power, which recommends solar cells.

I considered various mechanical conversion possibilities over the years, and several approaches have received some development. The backpack up-and-down item was the most recent news, but I'm not sure that's a very good approach to let the pack move up and down relative to the body. But if we're already generating a partial rotary motion with the hip rocking in the backpack's motion joint, that might be sensibly exploited. The heel-pressure devices as far as I know never went much of anywhere, although that approach seems to at least put things out of the way except for wiring, and perhaps not interfere with normal motions. Using major muscles that are being employed in large walking movements seems like the obvious fount of more power, and I think I drew a leg-lever apparatus at one point. It doesn't take much load to mess up gait, though, nor much pressure on leg muscles to intefere with function. Running cords from heels to backpack would exploit probably the largest available motion (making for low load per inch of movement) and wouldn't squeeze the thighs, but could present a tripping danger. Similar approaches might be taken with arms, with maybe more fatigue problems but less danger of catastrophically hanging up on the scenery. There are probably several other mechanical approaches that I gave thought to at one time or another. I haven't really thought about power generation in a while, though, and have just tried to keep my eyes open for what someone else might have developed. Methanol fuel cells might be of some use, but then you have to carry more fuel...but you have to feed yourself to generate power too, so the efficiencies have to be considered, and the weight of all this versus solar cells, with due account taken of the number of days one will be out, with solar becoming more sensible as more watt-hours of fuel need to be carried.

Edited by BobOne on 05/19/2006 18:25:03 MDT.

This is getting pretty far off the pack development thinking, but this very nice device was just announced and gives some idea of the capabilities soon to come to fairly-light backpackers that might make power-generation more of a must-have item: http://www.mil-embedded.com/news/db/?2873

You might want to pair something like that with a (forthcoming) wireless video headset to get a larger display, a phone/3G wide-area networking device or satellite phone in more remote areas, and a wireless fold-out keyboard.

Electronics and what I want. I want a PDA with a Cell Phone built in that I can connect to the internet. The PDA needs to have a replaceable battery so I can carry more than one if I want to. (Many will do this I just have to decide which one I want). It needs to use SD as that is what my Digital Camera has. I would like to have one of the "roll-up" keyboards that are about 2/3's the size of a standard keyboard. They roll-up about the size of a coke can. As the PDA's are coming with bigger keyboards I might forgo the "roll-up keyboard.

I want a real GPS that will work with the PDA if possible. I want to be able to plot way points when there is no snow and go back into the same area in snow and if I can't tell where the trail is use the GPS to guide me. The GPS is only one of my land nav tools. One year soon I hope to try winter SOBO AT Thru-Hike. Start in Jan/Feb on Katahdin and go south as far as I can, snow permitting.

I just looked at the link you posted. To bad there is no picture. Satellite phones are getting cheaper everyday and I think you can also rent them. I am thinking about making one of these little gems:

Edited by bfornshell on 06/01/2006 23:23:20 MDT.

Bill, if anyone every breaks into your house, they are going to go running out the door-- one look in your workshop will convince them you are building torture devices for the CIA :)

As to joint stabilizing:

I was just thinking of shock cords to keep the top and bottom from flopping around and it may not be needed at all-- the pack bag would keep it all together and your body should do all the stabilizing needed once you are strapped in. If the bag is full, it will sit up by itself.

I wonder if the weight will vector off to the waist belt with just the two frame sections (vertabra?) shoulder straps and waist belt. Does it need anything like the wands (flexible shafts) to pick up the weight of the bag and transfer it to the belt?

Simple is good for general design and weight saving too. More traditional ladder/H pack frames don't flex and the weight is sent straight to the hipbelt. Once you break away from the fixed frame/backboard idea, the complexity and the weight may go exponential. I guess what I'm after is an external framesheet.

As far as pack weight, IMHO, 25 pounds would be more than enough load to aim for. There are plenty of pack frames out there for folks who want to haul half the house with them.

Oh, I get the wand idea much better in that picture. The picture size and especially color contrast helps.

It's a lot like something I tried right after seeing a hip belt on the trail for the first time...made or bought a hip belt for my shelved-aluminum-tube khaki-bagged scout pack, got the soft foam pads including slide-ons for shoulders, thought, "there must be something better than this and this was too expensive", thought..."prop the pack on the front of the belt to form a triangle with something running under the armpit...now stiffen the belt". Hard to get the belt stiff enough with what I had. Then I struggled with the arm clearance issues of having something from that far on the front run that high up on the frame. Nowadays, carbon tubes could be thinner but I still don't perceive a lot of clearance for them next to my body.

The underarm prop attempt got me thinking of running a rod to a projection out front from over the shoulder and maybe have some of the weight hang less far off the back, but I didn't have a good way to make it in the sixties so it weighed too much in the state to which I developed it, and the stuff out front was a bit in the way but it was nice step up in shoulder comfort...it all felt much lighter when it was balanced and not squeezing my shoulders any more...but I needed a better waistbelt setup. I think I was trying aluminum electrical conduit among other things for the forward tubes.

Around that time my Dad was making fiberglass boats out back of the house, and I decided there ought to be a wrap around backpiece made out of this amazing fiberglass and polyester resin goop, but didn't develop it a great deal and got hung up on how to make a decent waistband with very limited materials and tools...and the local cub and boy scout pack and troop were pretty inactive and disorganized so I wasn't getting to use the gear enough.

Along the way I got pretty sensitized to pack appurtenances interfering with the arms, and although it might just be my particular body, there's not much clearance between arms and torso to play with and still allow a very natural walk. I'm not sure I'd get used to having those wands running from so high to so far forwards under my arms as on the picture Bill just showed and I guess on the MH packs. What's your impreesion of them, Bill? Tubes in compression run from high on the pack to far forwards is potentially a very light way to go either under or over the shoulder (note the big triangles), but there are ergonomic issues at least for me.

I resigned myself to not being able to get that superlight giant triangle over the shoulder going but looked to creating a somewhat smaller triangle effect with a molding that wraps around the body and upwards into the pack...sort of like the props but in bent sheet form right up near the body. When I tried with fiberglass I didn't attempt any sort of intermediate body mold, that much plaster being sort of beyond comprehension and my non-budget as a kid in like 1966 or 67 working with stuff that was lying around. I think I used a bent piece of posterboard or some found round surface for a fiberglass mold, then trimmed the layup so it bit me less and built it up more for strength. I still didn't have the stuff to get the waistband right.

The hard molded subframe fit near to my hips for arm clearance and carrying the weight down from higher on the pack seemed to make better sense on my body then and still does...and it could create much of the effect of running props out from under the armpits with fewer clearance issues. 2006 adults are a lot better equipped to actually execute a workable version these days, though, and more.

It's just great that you're doing all that pack fabrication, Bill. I'm excited to see what you'll be able to do with laminating. You've already practiced nearly every other skill needed to pull this off.

I'll try to remember to post a picture of that little computer when there's one out. We should be seeing a lot of variants of these small Intel-based computers hitting the market over the next year.

"Vertebra"...I like that! A marketer in our midst!

As to the need for wands, Dale, I think that's why the waistband section really wants to be rigid up to the vertebra, with whatever padding is needed where it touches the body. The upper edge of the waistband assembly (girdle?) would more or less replicate the path of the wands, only closer to the torso. The system would depend on the vertebra being pretty stiff in the crunch and de-crunch direction to transfer weight into the girdle.

I'd suggest you might want to skip the joint at the vertebra in the initial build, maybe building it light enough to maybe flex just a little there. This could let you try most of the concepts with little more than a layup with some padding, straps, and bag added, and a little devising to keep the packbag from flopping forward where it's not wanted.

My guess is that a well-fit girdle will show its fit value in this context, but that as the fit improves with the rigid structure around the hips, it will start to feel like you want that vertebra moving more in order to feel less restricted.

A step up in complexity over a solid vertebra could be to a rubbery-resilient connector in there, with spectra limiting the crunch and de-crunch motion.

The full complexity version could be the double-hinged structure we already discussed (the 2/3-gimballed vertebra), or the spectra-limited ball-joint version.

I enlarged the EXODUS pack pictures in the catalog on a copy machine and then scanned them. I am posting the pictures along with what MH says about each feature.
-0-
Mountain Hardwear EXODUS Pack Series:
Two EXODUS Frames.
(NOTE: Most of the following was taken from MH information.)

1. Motive Frame:
The Motive frame is designed for active backcountry and off-trail use. Motive's free-floating design allows unrestricted mobility for technical activities. For use with medium loads.



2. Cruiser Frame:
The Cruiser frame is designed for traditional backpacking and trail-oriented use. The Cruiser's center stay provides excellent stability and support for heavier loads.


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NOTE - (From Bill):
1. I think the only difference between the two frames are the lower part of the frame sheet area. It looks like the lower cross piece on the Motive connects to the upper part of the frame the same way the lower part of the Cruiser does. If you had one of the frames you might be able to get the parts to change the frames from one to the other and back. That would give you one frame that could work both ways with a quick parts change.
2. Notice the points on the far sides of the top of the frames. This is what the pack bag slips over when you put it on the frame. Straps on both sides of the bottom of the bag pull it down and the pressure holds it. The lower straps then attach to the bottom of the frame.
3. If you could buy other size pack bags you could swap out a larger bag for a smaller bag or the other way around.
4. I would just sew me a new SUL pack bag out of some Cuben Fiber.
5. I weighed the Maestro - med. The frame alone was 3 pounds 12 ounces. The bag alone was just at 2 pounds. Total weight was just as MH lists it - 5 pounds 12 ounces. Being that close to a pack that was that heavy empty made my blood pressure go up.
6. There is a lot of room to lighten the pack/frame system. I would really like to have one to put on a diet if I could get it free or at a really good discount.
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Pack Detail:

The Mini Frame:
This piece of molded polycarbonate is the backbone of the EXODUS system. It is engineered to have great vertical stiffness (keeping the loaded pack bag under control) while having torsional flexibility (allowing it to move with you when you twist your torso). Also built in to the Mini Frame is the ability to adjust the pack's torso length. You can either custom-fit the length to one lockable setting or allow the adjustment to ride free so the frame can adjust to your movements on the fly.


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The U-Bar:
The U-Bar connects the yoke of the harness to the main frame. This does two things: it holds the yoke in its correct, load-bearing shape, and it allows you to adjust the upper body-to-pack geometry. What's more, it lets you do the adjusting on the fly.



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The Fit-Lock Harness:
You can mold our yoke-and-belt system so that it fits the contours of your neck, collar, shoulders, hips, and waist. Then lock that fit into place. The harness stays in that setting until you decide to readjust it. High density foam and polycarbonate overlay hold this body-fitting shape, so load is transferred evenly. Think of how hard it would be to hold a cup of coffee if the handle were a floppy piece of fabric. That's what packs with non-structural shoulder straps are asking you to do.



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Scandium Tubes:
Heat-treated Yunan Scandium tubes attach to the Mini-Frame and transfer load to the waist belt. These advanced alloy tubes are very light and have high compression strength combined with just the right amount of flexibility to absorb a bit of shock and to allow the aforementioned torsional flex.


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The Pivoting Waist Belt:
While wearing most packs, bending over to tie your shoes is virtually impossible. That's because you are strapped in to a structure that does not bend where you do. Our pivoting waist belt changes that. Its two pivoting joints leave the belt free to tilt forward or back when your hips do. Now you can bend forward to tie your shoes or bend back to reach for a hand hold without having your pack fight you all the way.


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Thanks Bill...I can see a lot better on those pics.

Looks like you ran the wands farther forward on your "clone", right? It looks to me from the pictures like the MH would be more out of the way, behind the hips, but would primarily not provide as much triangulation. It also looks like the MH packs would be prone to pulling backwards at the shoulders and would be suited only to moderate loads...which is fine, but not at the weight of those packs. For that sort of weight it seems to me that one ought to be able to easily get the benefits of a metal external frame with at least semi-cantilevered wings to keep the pack from pulling backwards as much. My Stephenson with large bag runs 54oz. vs. the 92oz of the big MH pack. The Stephenson gets by nicely with those ephemeral mesh shoulder pieces due to the lack of backwards pull, and doesn't require the giant puffy insulated girdle of the MH.

Seems to me there's merit for parts of the MH design, but that the layout is really best for fairly light loads in a situation where it's desirable to maintain lots of flexibility, but it seems that for that usage, a pack ought to weigh a whole lot less. That also looks like quite a hot pack to wear.

I'm curious about how light a load a modern external frame might be ideal for with on-trail use. Someone recently reported on this thread that they were experimenting successfully with externals for quite light loads, if I recall correctly. It seems to me that if one even just built on the Stephenson pattern with CF and Cuben but for the same load capacity, the pack would weigh quite a bit less than the Stephenson. If the structure were optimized to take advantage of the ability of CF layups to run where they need to rather than where fairly simple ladder construction with tubes dictates, a lighter pack should result.

If such a pack was then built to only handle lighter loads than the Stephenson is capable of, the resultant pack should be lighter still, and we might then find out at what minimum pack-contents weight (how many days' on-trail range) the external might become preferable to the simple SUL packbag.

Edited by BobOne on 05/20/2006 22:08:31 MDT.

The "wands" on the "clone" were to close to my body and I removed them. My Wands also were to stiff to bend - they had almost no flex. One of the changes I have made on that frame has been to use a longer "frame sheet" thing. I know a lot more now than I did when I made it and I think if I made another one I would make a lot of changes. If I made it wider at the top I might have space for the wands. If I can find something that will flex like MH uses I would try that. Now that I know what the MH wands are made out of I discovered that they also use that same stuff for some of their tent poles. I am going to call monday and ask about buying a set of tent poles if any are long enough to work on the frame.

If all the Exodus packs had not been recalled I would have been able to get more pictures and would have had time to study the pack at the local store here a lot more. I will check back with them and see if they are going to get them back when the problem is fixed. The packs are very heavy and I am sure they would be very hot in warm weather. The fittings are all 1" or bigger and there are a bunch of them. The hip belt webbing is 2" and the buckle for it is a monster. Lots of places to drop some weight. The hip belt is thick and heavy and the shoulder straps could be also lighter. I was shocked at how heavy the frame was when we took the bag off of it.

I have learned a lot just by enlarging the pictures and typing the data about each picture. I also think there are parts of the frame that might work on what we are after. For me this last week has all been a lot like Frame Design 101. It was nice of MH to go into so much detail and all your input has also taught me a lot. Dale, you fit in here also even if you forgot about my Cuben Water Filter.

I have made an external frame (stripped) as light under 7 oz that was full size and my Cuben pack bag for it was only 2.10 ounces. 1.28 ounces on that pack bag was for the full side and front mesh pockets. The pack bag is a little larger than the G6. For a light load of 12 to 15 pounds or less it is easy to make a external frame and bag under 1 pound.

I think I could do a long AT Hike with that under 1 pound frame/pack. I would plan a resupply cycle of every 3 or 4 days. With my SUL/Hyper-Light Gear I am sure it would work. This would be for a typical start time of April and end on or before mid-Sept. This would put me in mild to warm to hot weather much of the hike. Cooler weather at the start or at the end would be no problem as I would just add a light extra layer or remove one from my gear. If I added some Thermo Plastic pillows to the frame and hip belt for a cooler pack the weight might go up an extra pound.

If you wanted to extend your range it would be mostly just be more food weight. You might even be able to push 6 to 8 days with that pack. With a little more weight I would add a better hip belt than what I was using. My hip belt, which was almost nothing, failed at 22 pounds. That is when I started playing with the "wing" to help support a light hip belt. My next wing was going to be made out of Titanium. It was going to be a little wider and longer.

I might work on a new version of a light "wing" frame while I wait for the Composite stuff and books. I would only use Titanium for the wings and keep the frame simple, maybe. I have some new foam stuff to try for the padding on shoulder straps and hip belts. It would be a good test to see how it is going to work.

I'm not sure when I might be able to dig this out, but I think I must have some letters from Jack Stephenson somewhere. I remember him telling me his thinking about his waistband and wings, how, iirc, it wasn't intended to wrap and squeeze like the typical waistband, but was trying to tie into the shelves on the sides of the hips with the wings and that it didn't work for everyone but if I had any exposed hip bone it should. He may have said it better than I have.

Indeed that's what it felt like, which is like your thermoplastic setup, and like what I was trying to get at with a fiberglass hip shell close to my body.

When Stephenson proved the bracing to the hips idea, I became confident that my old idea with the fiberglass would work out best and be lighter if it was well-fitted to one's body and the pads were well-placed...and it could distribute the weight onto the hips more ideally than the Stephenson too. And after the advent of carbon fiber, reading Carroll Smith's seat-making procedure, and your doing the thermoplastic work, it seems like an even better idea.

Something like the wand idea could be added in later if more bracing for side-to-side floppiness of the top of the pack bag is needed, if the wands are resilient enough not to restrict the hip motion too much. They might also help in keeping the packbag away from the back, but I was also thinking a few horizontal floating ribs that follow the shape of your back might the light way to hold the pack bag back exactly where it's wanted.