Projects that make or build something.
It’s been a good year for growing tomatoes in my garden. The best year I’ve ever had, which isn’t saying much.
This has meant spending a fair bit of time preserving tomatoes. And while I like to grow them and eat them fresh, I’m not all that fond of preserving them. Continue reading Post #G21-048: Going full West Virginia
EDIT: The downloadable file for this post ended up with several Excel-related glitches. It is in the process of being replaced with a corrected file (with, I think, no Excel problems) using a newer year (2019) of Medicare data. The revised version of this will be posted shortly.
If you’re thinking of having knee replacement surgery and live in DC, MD, or VA, you may want to download and have a look at this Excel (.xlsx) file:
The workbook linked above contains a list of orthopedic surgeons in DC, MD, or VA who performed knee replacements on traditional Medicare enrollees in 2018. It shows the volume of each surgeon’s Medicare-paid total knee replacements, partial replacements, and repairs (revisions) of replacements. A second sheet in the workbook provides counts of fee-for-service Medicare inpatient knee and hip replacements by hospital for the same three states.
Why should you care about how many knee replacements a surgeon has done? In a phrase, practice makes perfect. This is true of most complex surgical procedures such as joint replacements, and is particularly true of partial knee replacements. To quote one carefully-done large scale study out of Great Britain:
Caseload had a profound effect on implant survival. Low-volume surgeons had a high revision rate ... and therefore should consider either stopping or doing more UKR procedures. High-volume surgeons ... demonstrated a 10-year survival rate of 97.5%, which was similar to that reported in registries for the best-performing TKRs.
(N.B., UKR = partial knee replacement, TKR = total knee replacement, revision = repair or replacement).
Why care about Medicare-paid surgeries? Mainly, that’s the only data you can get that shows the number of procedures performed by individual surgeons. The data and methods are public information (accessible at this link). That raw information is impossible for most people to use, so I created the workbook above. As importantly, Medicare is a big piece of this market. In these three states, in 2018, the traditional (fee-for-service) Medicare program paid for roughly half of all knee replacement surgeries (documented below). And so, while this Medicare-based workbook only shows part of each physician’s practice, in most cases it shows a large part of it.
Think of this as a place to start as you decide upon a surgeon and hospital for your knee replacement. Volume of surgery alone is not a direct measure of a physician’s quality or competence. But if you’re going to have a knee joint replaced, you probably want a surgeon who replaces a lot of them. You’ll obviously want to look at more than just surgical volume before choosing a surgeon. But surgical volume is one reasonable criterion. This is one of the few places were you can find orthopedic surgeons known to do a high volume of knee replacement surgery.
For now, you only need to know a few things to use the data.
This workbook also contains a crude ZIP-code based distance measure. You can use a standard Excel method (“filtering”) to find orthopedic surgeons near you. For example, you can easily reduce the list to orthopedic surgeons within 30 miles of a given ZIP code, who did at least 100 Medicare-paid knee replacements in 2018. The README sheet in the workbook briefly explains how to filter the data.
Absolutely nothing about this file is perfect. The counts are incomplete, the distance measure is crude, and so on. But for most users, it’s probably good enough to be useful. If you’ve ever tried to find a specialist, used an on-line website, and been faced with a list of hundreds of names, you’ll understand the utility of having some systematic approach to whittling down the choices. At the very least, if you’ve gotten recommendations for a surgeon, you can now look them up and see whether or not they appear to do a lot of knee replacements. And, as discussed below, you can often use the Medicare Compare website to identify hospitals to which that surgeon admits patients.
The rest of this post talks a bit more about the underlying data source, documents the estimate of traditional Medicare’s share of the market in these three states, and rambles a bit about about why I put this together.
The Excel workbook above is based on Medicare claims (medical bill) data. In this section, I describe the relevant parts of the Medicare program, and show that for the three states in question (DC, MD, VA), in total, traditional fee-for-service Medicare paid for about half of all knee replacements in 2018. Throughout, I ignore Medicare Part D (drug) coverage.
Roughly 60 million Americans are insured via Medicare, our federal health insurance for the aged and disabled. You can find a concise summary of enrollment statistics at this link.
Of those, just over one-third are actually enrolled in private health care plans, termed “Medicare Advantage” or “Medicare Part C” plans. For those beneficiaries, Medicare simply pays monthly premiums to those plans, just like any other health insurance coverage. With limited exceptions, the Medicare program itself never sees bills (claims) for services provided to those individuals. They are (almost by definition) excluded from the counts in the Excel workbook provided here.
Roughly two-thirds remain in the traditional “fee-for-service” Medicare program. For those individuals, Medicare hires contractors to process and pay their covered health care bills. For those individuals, the Medicare program gets an electronic copy of every bill that was paid. One way or the other, each bill shows what service was provided, and how much Medicare paid for it. Those are the counts that make up the data for the workbook above.
There is a small factor that also must be considered, which is that Medicare covers inpatient facility care (Part A) separately from payment for professional and outpatient services, such as payment to a surgeon (Part B). An increasingly large share of enrollees in traditional Medicare have Part A coverage (which is free) but not Part B coverage (which is merely heavily subsidized, not completely free). (This does not happen in Medicare Advantage, because (with rare exception) you must have both Part A and Part B coverage to be able to enroll in a Medicare Advantage plan.) Working from these enrollment statistics, about five million Medicare beneficiaries have Part A but not Part B. Because these are by definition concentrated solely in the fee-for-service portion of Medicare, this means that currently about 12.5 percent of Medicare fee-for-service beneficiaries have Part A (hospital inpatient bill) coverage, but not Part B (surgeon’s bills) coverage. These individuals tend to be relatively low users of care. But to the extent that such an individual would get an inpatient knee replacement, Medicare would see a bill from the hospital, but not from the surgeon.
For the U.S. as a whole, we can use a reference inpatient database (the AHRQ HCUP database) to estimate the fraction of all inpatient knee replacements paid by any part of Medicare. This will include both traditional fee-for-service Medicare and Medicare Advantage plans. As of 2018, Medicare paid for 57% of all inpatient knee replacements.
But that would include not only traditional Medicare, but Medicare Advantage as well. To parse those apart, I relied on an old analysis that I had done for clients back when I worked in this area. (That analysis required separating out Medicare fee-for-service discharges from records for Medicare Advantage discharges.) Based on that analysis, for knee surgery, for DC+MD+VA combined, traditional Medicare accounted for 90 percent of inpatient knee replacements in 2017. (For the U.S. as a whole, it was more like 70%).
So fee-for-service (traditional) Medicare’s share of inpatient knee replacements, for DC+MD+VA, would amount to 90% of 57%, or 51%.
Finally, I have to guess what fraction of those with Medicare fee-for-service inpatient knee replacement had Part A but not Part B. This is a lot harder, because those without Part B tend to have a much lower rate of service use for elective surgery such as knee replacement. As a reasonable guess, based on years of looking at this question for other procedures, I’d guess that 6 percent of those knee replacement patients had Part A but not Part B.
So fee-for-service (traditional) Medicare’s share of surgeon’s bills, for knee replacements, for DC+MD+VA, would amount to 94% of 51%, or 48%.
The upshot of all of that is that, if I’m looking at fee-for-service knee replacement claims paid by Medicare Part B, in DC+MD+VA, in 2018, I’m looking at just under half of all knee replacements done in this geographic area.
The actual public-use data file is Medicare’s summary of the individual claims (bills). Medicare summarized the file by physician identifier, place of service (inpatient or outpatient), and procedure (AMA Common Procedural Terminology (r) Code). As a privacy protection measure, Medicare blanks the data any time that leads to a count of fewer than 11 total services.
Because of that summary-and-redaction process, I will lose some counts of knee replacements every time a surgeon does fewer than 11 of any one particular type of knee surgery. But that factor is more-or-less irrelevant if the task is to find high-volume surgeons. It might might drop a lot of volume out of the file in total, but it should leave the counts for high-volume surgeons more-or-less unaffected.
I did considerable post-processing of the Medicare file, to achieve two things. First, I edited out aberrant-looking lines, mostly trying to get rid of claims for assistance-at-surgery. (Assistance-at-surgery is exactly what it sounds like — it’s the service of assisting the main surgeon who performs the surgery. Unfortunately, assistance-at-surgery is billed using the same codes as the surgery itself, with a separate “modifier” indicating assistance. Medicare just summarizes all the bills, regardless of modifier.) Second, I added the counts for the range of surgical codes to generate the categories you see labeled on the spreadsheet.
As a validation, I found that after all my edits, and all the CMS redactions of cells with fewer than 11 surgeries, I ended up with 93% of the “benchmark” count of U.S. total knee replacements. (The benchmark is based on the Medicare Part B National Summary file, excluding assistance-at-surgery (80s) claims.)
I worked more than 30 years as a health economist, and spent most of that time analyzing Medicare claims data. After three decades, I was both good and quick at doing that sort of analysis.
During my career, I was repeated floored by how hard it was for the lay person to get an answer to even the simplest questions about health care, based on Medicare’s experience. If somebody in the Medicare program had not tabulated exactly what you wanted, just by chance, then you were out of luck. In most cases, for most questions, my sole option was to work up an analysis, from scratch, directly from the large public-use or limited versions of the Medicare claims and enrollment data files.
Absent that data access and analytical firepower, I could not get answers to obvious and simple questions. And it wasn’t so much that Medicare didn’t occasionally try to provide summary data that could answer some questions. It’s more that most questions you’d like to see answered require just a little bit of analysis that is specific to that question.
And so it is with these counts of surgeries. Medicare makes the raw summary file available, and even has an interactive on-line query system. And even with that, I’d bet that the average American would find it impossible to use that system to produce any sort of meaningful information. You have to know just a little bit — about the codes used to represent the surgeries, about assistance-at-surgery claims — to convert the raw data to a useful listing.
And, since I spent 30 years developing those skills, I figured I should put them to some use.
This is actually the second time I’ve done this analysis. The first time was years ago, when a friend’s wife was facing a replacement of a failing partial (unicoldylar) knee. Her knee was not done correctly the first time, it had worn prematurely, and replacements are much harder than initial implants. She really wanted to find the best of the best for her surgery. And so I did essentially this analysis, and in fact came across the surgeon who literally wrote the textbook on revisions of uni knees.
That story then had a happy ending. But without access to information like this, it’s hard to pick a surgeon. You are reduced to asking friends for suggestions, or soliciting suggestions from social media. Both of which can work, but neither of which is very systematic.
The second time I did this analysis was two weeks ago, when a question about surgery for a uni knee revision was posted on NextDoor. I figured, I might as well dust off the old analysis and see what it said now. And it actually turned up the same national expert on uni knees, at the top of the listing.
Otherwise, finding and choosing a surgery is just a hard task. You scrape together whatever information you can find from various sources. Maybe you solicit recommendations from your family physician, friends, or via social media. And you try to synthesize all of that.
What I have found is that on-line physician finder sites give you an overwhelming number of choices. And when it comes to surgeons, it seems like all of them get top ratings. They are great for showing you all of your options. They are not much good when it comes to narrowing your options.
And that’s why I like practice-makes-perfect as a guide. It’s not merely that you should avoid surgeons with low volumes of the particular surgery you need. It’s that you will find that, particularly with anything out-of-the-ordinary, surgeons with high volumes got that way because they had a reputation for being the local expert. A surgeon doesn’t get to do (say) 80 partial knee revisions per year unless that surgeon has the reputation as the go-to person for that particular surgery.
So there you have it. It’s not perfect, slick, or pretty, but it makes that Medicare data available to people who might want to use it. Now that I’ve worked out the kinks for doing this from public-use data, there’s no barrier to doing a national version of this file, and there are only small barriers to doing this for other common surgeries where the practice-makes-perfect effect is known to be important. As a final note, Medicare updates the underlying data annually in November, so if I’m still in this business at that time, I should be able to update this using newer data then.
For about 20 years, I was self-employed as a health economist. In the course of that, I used terabytes of “sensitive data” in the form of health care claims (bills), all of which, at some point, had to be destroyed.
I started in the era of reel-to-reel magnetic tape. You’ll still see those big reel-to-reel tape drives in the backround of cheesy science-fiction movies. At some point, those open reels morphed into tape cartridges, the same magnetic medium in a more convenient and higher-storage-density package.
In either case, destroying data on magnetic tape was easy. All you had to do was pass a big purpose-made electromagnet over the tapes, and they were rendered unreadable. Bulk tape erasers were cheap, fast, and effective.
Then, for a while, I got most of my data on optical media such as DVDs. Those actually had some entertainment value when they were due to be discarded. I’d toss them on the gravel pad in my back yard and invite my kids to stomp on them. They seemed to have a good time, and I guarantee the results made the discs unreadable. It was an occasional family ritual we referred to as the dance of data destruction.
But what I mostly have now are disk drives. Boxes and boxes of high-capacity disk drives.
As my career progressed, drive manufacturers were great about increasing drive capacity. I started out using 30 and 60 megabyte drives. (Yes, megabyte). Large files had to be split across multiple drives. But as time went on, files that I used to have to split across multiple drives now easily fit on modern multi-terabyte drives. The sizes of the files that were made available for distribution increased accordingly.
Drive manufacturers did a great job of increasing capacity, but speed of access did not increase in proportion. As a result, it takes hours upon hours to overwrite the data on a modern multi-terabyte drive. I even bought a device dedicated to erasing drives. This device absolutely works at as fast a rate as the drive can handle. And for multi-terabyte drives, it takes the better part of a day to do even one pass over the entire drive surface.
And so, as much as I hate to do it, I’ve decided to destroy the drive hardware rather than just wiping the drives and giving them away. Once you figure out how to get into the drives and extract the platters (disks), this is orders-of-magnitude faster than overwriting the data and keeping the drive intact.
This bothers me, because these drives still work. But it only bothers me a little. Disk drives with rotating magnetic media are dinosaurs, being replaced by solid-state drives in just about every conceivable situation.
So my lovely multi-terabyte hard drives are, in a sense, just the reel-to-reel tapes of the 2020s. They work, but they are in the process of becoming obsolete.
I found several YouTube videos on how to take apart hard drives, but none of them seemed particularly good. So I made my own. If you’ve ever wondered what the inside of a hard drive looks like, check out my three-minute YouTube video on how to disassemble a hard drive and extract the platters.
Last year I put in a fairly serious vegetable garden. Partly it was for the exercise, partly it was to have something to do.
And partly, it was so I’d have something cheerful to see when I looked out my back window. Like so.
I’m going to start this year’s garden posts with lessons learned from last year. Scroll down to the headers in red to see if any of this interests you. Continue reading Post G21-001: Garden lessons learned.
The brief for this task: Create a floor-to-chair aid for wheelchair users. It must be able to be made at home, using only simple hand tools and readily available materials.
The end result is shown directly below.
Above: Floor-to-chair aid, folded and covered. For scale, the push-up bars sitting on top are 6″ tall.
Above: Rear view, folded. Lower stairs sit atop upper stairs when folded. The boxes nearest the camera flip away from the camera when put into use.
Above: Rear view, unfolded. Lower stairs have been flipped off the top, away from camera, revealing hardboard stair tops. Push-up bars are on top.
Above: Front view, folded. Blue cloth connects the lower and upper sections of the staircase.
Above: Front view, unfolded. Lower stairs have been flipped off the top, toward the camera, revealing hardboard stair tops. The blue cloth keeps the upper and lower stairs connected. Continue reading Post #927: Wheelchair floor-to-chair aid, V3
This post is a set of instructions for creating a utility knife guide, for making fast, straight, precise cuts in corrugated cardboard, using a utility knife. This guide only cuts cardboard to 4″ widths, but you can easily modify it for other widths. It uses about $7 in parts, and takes about 15 minutes to construct. Continue reading Post #926: Knife guide for cutting corrugated cardboard.
This is the final set of refinements for my floor-to-chair aid staircase. I’ll build a new set of stairs incorporating all the changes when the materials arrive later this week.
The upshot of this posting is that the only configuration you can build out of readily-available parts is a staircase with four 4.5″ steps. And that it might be a good idea to carpet those steps.
As planned, the entire setup, including carpet and pushup bars, should cost about $55, and should take just over three hours to build. The footprint of the stairs will now be 48″ x 32″
Details follow.
Post #913 was a proof-of-concept. It demonstrated that you can make a sturdy, portable staircase, suitable for use as a floor-to-chair aid, at home, using nothing but readily available materials and a few simple hand tools. At modest cost.
That initial design has a lot of drawbacks. It took a lot of time, used a lot of materials, had a lot of unwanted variation in the cut-up size of those materials, wasn’t really the right size, may or may not stand up well under the pressures generated by the pushup bars (used in lieu of grab rails.)
And so on.
So the point of this post is to fix what I can, to make this faster, cheaper, and better.
1: I’m sticking with using identical new boxes, at least for now.
I’m sticking with the idea of building these up from packages of identical new boxes (via Amazon). It gives them a reasonably finished look and, practically speaking, it’s the only way I can make up a set of instructions that somebody could readily follow. Otherwise, I have no idea what the end user is working with.
2: You can skip reinforcing the lower boxes.
Savings: Roughly one hour of time, and six fewer cartons required for the 3-step model.
I suspected this was true from the start. The corrugated cardboard in these cartons is rated to 32 pounds per linear inch in the “edge crush test”. That gives a roughly 500 pound theoretical load, for these boxes, before they would fail, as long as that 500 pounds were spread evenly across the tops of the box walls. (That calculation is based on this short Wikipedia article).
So I tested the theory. I removed the internal supports from a box at the rear bottom of the stairs. And when I sat on the stairs, nothing happened. There is no perceptible difference between the side with all boxes reinforced, and the side where one box is not reinforced.
This works in part because the boxes themselves are strong enough. But also because the first level of boxes — the part you actually sit on — serves to spread out any loads.
There is a risk here, in that the reinforced boxes are more robust to injury. You could damage the box wall, and still have plenty of corrugated inside, holding up the box. With unreinforced boxes, there’s just one layer of cardboard. If it gets seriously damaged, the box could fail.
I considered adding corner reinforcements to the now-empty boxes, but commercial reinforcements are only sold on large lots. The alternative of gluing up reinforcements, from layers of cardboard, is unappealing.
For the time being, I’m doing nothing. I think these short boxes are robust enough on their own. And if a sidewall gets damaged, just cut out the old box and put in a new one.
This has a lot of benefits.
This reduces the burden of cutting and carton assembly roughly in half. And means that you save six cartons’ worth of cardboard. It also makes for a neater overall look, as there will no longer be “overstuffed” cartons that bulge, below the top level of cartons. It lowers the height of the steps because the tops of these boxes no longer bulge. And it allows me to customize the height of the steps much more easily.
3: Pay more attention to form factor/box size; customize step height if needed.
The prototype turned out with steps that are too tall. I naively thought that a 6″ box would yield 6″ steps. But in fact, a 6″ (interior dimension) box is actually 6.5″ tall. Add in some “bulge” from over-cut support pieces, and the steps average just under 7″ tall.
Assuming I can eliminate the problem of bulging boxes, and noting that the hardboard only adds to the height of the first step, I now know what my options are, using stock cartons.
I can find 3″, 4″ and 5″ tall cartons whose other dimensions would work for the other dimensions of the staircase. Each step adds a foot to the length of the staircase. I’m assuming that 4′ long is the practical limit, but that’s just a guess. With those constraints, to get the top step near a common wheelchair seat height (18″ to 20″), I only have three options using stock (uncustomized) boxes:
Anything other rise height or total height would require me to cut down the boxes to a custom height.
If I had to redo the current staircase from scratch, I’d just buy shorter boxes. As it stands, rather than waste the boxes I have, I think I’m going to shorten them. This will also be a test of whether or not I could conveniently build one to some exact specification for riser height. It’s not hard to reduce the height of an empty cardboard box. Tools for doing that are readily available for under $20 (such as this one, from Amazon).
The only difficult part is resizing the very first step, because that one requires resizing both the carton and the reinforcing cardboard in the carton.
Which brings up the next point.
4: Create a cheap jig for making accurate cuts in the cardboard.
The need for perfectly-cut interior supports is a real drawback. Uneven supports weaken the load-bearing capability and they make the boxes bulge, which makes the final assembly tough and makes the results look slapdash. In the prototype, I sorted the supports by size. But what I really need to do is cut them the right size in the first place.
There does not appear to be a commercially-made “knife guide” to meet my needs. Searching for “knife guide” bring up kitchen appliances and sharpening aids.
But, in a mini-quest, I think I can easily make one.
In addition to making the cutting more accurate, I think this will also speed it up considerably.
5 Modify the reinforcement in the top boxes, the ones you actually sit on.
I decided against this. I’m keeping this the same as it is in the prototype.
The top boxes have to distribute fairly intense point loads from the pushup bars. And they take high transient dynamic loads as the user moves up and down the stairs. So this is the part of the staircase that needs reinforcement.
I’m not thrilled with my current method of little cardboard “V”s. But I’m not seeing anything that looks like it’ll work better, for the same or less effort.
I ended up with the “V”s because I tried to do the standard rectangular interlocking grid reinforcement, but that took vastly too much time. (As a means of reinforcing a box, a grid is more efficient than “V” because the cardboard supports are absolutely evenly distributed. But it just takes too much time to produce all that grid from raw cardboard.)
I considered non-cardboard materials for the support, but didn’t find any that met all my criteria (cheap, strong, fast, recyclable).
Spray foam would be expensive and of unknown durability. It would take roughly two cans of Great Stuff spray foam to fill one box. (Calculated from this source — each can produces about .31 cubic feet of foam). And that would also mean that the boxes could not be recycled.
I may yet try insulating foam board. That’s lightweight, cheap, and durable, but very tough to cut well with just a utility knife, and even tougher to cut to an exact size with a knife. That would also require removal before recycling the cardboard.
All things considered, other than cutting the pieces to an accurate 6″ height, I’m sticking with what I have.
6) Stiffen up the top surface.
The hardboard panels on the prototype serve three purposes.
First, they stop high point loads from puncturing the cardboard. E.g., think how easy it is to drive a ball-point pen into a cardboard box. So they prevent accidents like that from trashing the sitting surface.
Second, they provide a slick and wear-resistant surface. This both helps the user to maneuver, and prevents repeated use from rapidly wearing through the cardboard. (The tape, on the other hand, is a different matter.)
Third, they help to spread the loads over a larger area. But they do this poorly, because the hardboard panels are themselves quite flexible. For example, if you try to walk on this staircase, you get an unacceptable level of deflection of the step surface under your feet. Your weight is simply not spread out enough for the cardboard to take the load without deforming.
To spread the load, ideally, you’d have a very stiff top surface, one that wouldn’t readily bend. The stiffer it is, the better it will spread the load. And that matters greatly, because the entire strength of the steps comes from spreading the load over a large amount of corrugated cardboard.
I used 1/8″ hardboard because I knew I could cut that by scoring it with a utility knife. I didn’t go with something stiffer (plywood, say) because it’s too hard to cut (or cut well) with simple (non-power) hand tools. (And it makes a mess when you cut it.)
I’ve looked at options for a stiffer step (1/4″ MDF, gluing multiple sheets of hardboard together, creating foam-core hybrid materials using insulating foam and hardboard, using thin plywood) and they all have drawbacks (that I won’t bother to detail).
Instead, I’m going to take the scraps of leftover hardboard and add a second layer of hardboard on the outside 10″ of each step. These will be the “landing pads” for the pushup bars. Those bars will exert considerable point force, with the user’s entire weight resting on the eight small feet of the pushup bars. With a 200 pound user, I can plausibly expect a static load of 20 PSI and a dynamic load of twice that. Whereas the user’s rump will generate no such high point loads. And so, any reinforcement of the surface needs to go on the ends.
7 Try duct tape.
’nuff said.
8 Try a different assembly routine.
It would be nice if all the tape joints were visible from the outside. That way, if a box got smashed, you could easily cut out just that one box and tape a new one in its place. It also took quite a long time to assemble all the boxes, and I have to believe there’s a quicker way to do that.
9 Conclusion
I think that’s it. Those are all the changes that are believe are feasible for me to do. So the revised instructions would look like this:
I am guessing that with the reduced amount of cutting of supports, the jig to speed the cutting, and so on, that this will now take under three hours. And require less effort.
I’ll rebuild the existing staircase tomorrow. And I’ll build the 4-step 4.5″ riser model when the boxes get her via Amazon.
This design works, but it’s really a proof-of-concept. I’m now looking for easier ways to build it. As I figure out improvements, I’ll post them separately, and link to them here.
For example, today (12/12/2020) I tested whether or not the lower cartons need to be reinforced. They don’t. The empty cartons themselves are sufficient. That alone shows that there are faster, cheaper ways to build these steps.
See Post #914 for proposed modifications and a somewhat easier way to do this. I’ll post a revised set of directions when I rebuild this tomorrow.
Post #917 now gives the final changes. As it turns out, the only set that’s feasible to build and use, using off-the-shelf materials, is set with 4.5″ riser height and four steps. I’ll document building that set when the materials arrive later this week.
Original post follows.
This post is a set of instructions for creating a broad, shallow, portable staircase. The idea is that a paraplegic wheelchair user could use this staircase, along with a set of pushup bars, to move from floor to chair level or vice-versa.
That’s a picture of my wife sitting on the finished steps, left. It’s meant to illustrate how sturdy these steps feel, as she is perfectly comfortable sitting on them.
This is a followup to Post #886: A floor-to-chair/chair-to-floor aid for wheelchair users. If you want the background on why I’m doing this, and what this is for, read that post. Continue reading Post #913: A D-I-Y floor-to-chair aid for paraplegic wheelchair users
This is an intermediate step in the production of a D-I-Y aid for wheelchair users. The background can be found in Post #886 and Post #887.
The question is, just how hard is it to make a lightweight cardboard object capable of supporting a person’s weight? I know that it can be done, in theory. But sometimes you just have to see it to believe it.
The answer is, it’s not hard at all, to make a cardboard structure that will stand up to the weight of an adult. Hence, the brief piece of performance art below that I call “fat man stepping on a cardboard box”.
What you see above is an example of the “structural grid plus envelope” method for creating corrugated cardboard structures (Post #887). Except I didn’t even bother to create a grid. I just tossed in a bunch of strips, cut to height, and folded into “V”s.
If that works, as sloppy as that is, it’s going to be a piece of cake to make a set of steps capable of supporting a seated adult.
In fact, the challenge here wasn’t even in supporting the weight. The biggest challenge was getting those strips cut to a uniform width, so that the weight would be evenly distributed. But even with all the sloppiness, it’s obviously no big deal to construct something out of cardboard that will support the weight of an adult.
