Building an Exoskeleton
I’m working on building a powered exoskeleton to help my Mom walk and I’m going to begin documenting the process over at openexo.com. I hope that it might be of interest to others. I’ll also be updating this blog with major updates as the project evolves.
In Part 1 I rambled on wrote about the lead-up to building the treadle-based exerciser and power generator. Now on to the actual mechanics!
I decided fairly early on that the double bass pedal I bought was going to be conducive for modifying and that it’d be best to build the device from scratch. Here is a shot of a recent iteration:
With the drill attached to the base standing up by its base, I discovered that the force of the chain on the drill chuck would bend the plastic drill body and thus create too much slack between the drill chuck and the wheel cog. So I’m now laying the drill on it’s side and clamping it to the base with hose clamps:
It’s now very sturdy.
How it Works
- User starts spinning the flywheel (pink wheel) by hand to get the motion going
- Then the user starts pushing the wooden pedal down as it’s traveling up and down to maintain the speed of the spinning wheel. The linkage between the wheel and the wooden pedal converts the radial motion of the spinning wheel into the linear motion that causes the pedal to travel up and down.
- As the wheel spins, the sprocket on the wheel also spins and that rotates the sprocket at the head of the drill chuck via the connecting chain
- The regular 18v cordless drill that I’m using acts as a DC generator when it’s driven in reverse (a force driving the chuck as opposed to the drill motor driving the chuck) and electricity is produced which can be harvested at the motor connection terminals (the terminals which in normal use would be connected to the drill battery).
- The motor terminals are then connected to the DC input of a battery pack to store the juice. I’m using the Electromate 400:
The neat thing about the Electromate 400 or something similar is that is a has A/C conversion and output built in. But if you were using straight batteries you could rig up (or buy) a rectifier to convert the DC energy to AC. - I’ll also most likely need to add a blocking diode to the connection between the drill motor terminals and the battery pack in order to stop the juice from flowing back from the battery and into the drill putting a load on the drill motor.
Parts Breakdown
Here is a list of the parts that I’ve used so far in the project:
- Wood board for the base
- Wood scrap for the pedal
- Door frame hinge for the pedal to the base connection
- Kid’s (Barbie?) 16″ bicycle wheel that my Dad had picked up along the way
- Bike chain
- Additional used coaster hub sprocket to use on drill chuck
- 18v cordless drill (bought on Craigslist cheap because the battery wouldn’t hold a charge)
Assembly
In general the assembly is pretty straightforward.
I took a brute force approach in converting the coaster brake hub of the bike wheel into a fixed gear in order to drive the sprocket from the spinning wheel and in turn drive the sprocket on the drill chuck. I used JB Weld to “fix” the sprocket fitting on the hub to the hub flange.
I also used JB Weld for attaching the spare coaster brake hub sprocket to the head of the drill chuck. I also considered JB Welding/arc welding the sprocket to a broken drill so that the bit could then be inserted and tightened into the chuck. This would allow the sprocket to be removed if need be. I ruled that approach out though because of the headaches of centering the sprocket with the bit base and also it not being as sturdy as the current setup.
While iterating, I realized that the flywheel was going to need to be a lot heavier in order to develop a sufficient momentum to keep it going with the treadle pedal. So I filled the wheel with concrete:
I’m a concrete newbie and one thing I learned that for this purpose it would have been better to use straight portland cement as opposed to concrete. Concrete contains gravel and the larger pieces made it difficult to work the mix between the spokes and into the wheel whereas portland cement is purely the fine cement itself. It would have also been easier to mold the outside of the wheel which would make it more aesthetically pleasing.
Stay tuned as I should finally be generating juice in part 3!
DIY Standing Frame
Here’s my Mom in a standing frame I built for her:
I made it using:
- Gold’s Gym Standard Gym Bench I got from Walmart for $77
- A 2 ton bottle jack that my Dad had from a an old vehicle which is nearly identical to this one on Amazon
- Some miscellaneous steel scrap: angle lengths (from a bed frame), some thin gauge tubing for the adapted jacking handle and some 3/16″ plate
Altogether my cost was the $77 (+tax!) for the bench but if you need to buy the jack as well as some of the additional steel, it would still only cost $110 or so. Of course not including the labor 
I spent probably 15 hours on it. But a lot of that was figuring things out and trying things out (and then finding out I needed to do something else!). I think I could probably do it again in a day. But that of course doesn’t include any finishing work. My Mom refers to the one in the photos as “industrial style”.
I needed to cut, grind, and weld some of the steel pieces from the gym bench to make the standing frame components.
Here are some more pictures of it:
The white tubing coming up from the jack is an extension for the jacking mechanism to allow the user to jack him or herself all the way up to a standing position from a sitting position.
The knee/leg lock at the front of it can be removed by pulling it up out of the center tube and placed back in relatively easily to allow the user an unobstructed path for transferring onto the seat.
It’s designed so the user doesn’t have to put his/her feet into the foot pedals and can just leave them on the floor which I think in most cases makes transferring easier. I think that the reason the commercial stands have the foot pedals is for the ability for the whole unit and user to be wheeled around on the casters that they come with. That’s probably really handy in outpatient rehab settings where the frame (along with users of it) might need to be rearranged on the floor quite a bit throughout the day.
Imperfections:
- The seat height isn’t adjustable and although the fixed height works well for Mom, I think it would be better if it were a bit shorter and of course might be difficult for others to adapt to it. But there are some areas for play in the height for the future.
- The weight bench seat is 11 inches wide and so a lot of users would probably feel more stable and transfer more easily with a wider seat. This could be done relatively easily by doing some custom upholstery with a board of desired width and length and padding and cover or by sourcing a wider seat from something else.
- The knee pad post is a bit on the heavier side and so, if it were lighter, it would make it easier to put it in the tube and pull it out. That could be done by using narrower tubing.
To Do:
- Attach another long handle (like the one for the jacking) to the bottle jack on the release screw so the user can let him/herself down from the standing position alone. I encountered some difficulty with this because the screw is a small welding target and also, in retrospect, when I was trying to weld to the screw I grounded the welder off the tube so basically the current was forced to try and make it’s way through the hydraulic oil to complete the circuit and so the arc wasn’t good at all. Should be able to wrap this up quickly though with another attempt.
- Creating a transfer bar on the transfer (right) side of the seat to help with transferring
- Maybe add a seat back. Not crucial, but would probably add additional comfort
- Create a chest brace. Depends on the user on how necessary this is
- Create a table in front for use when standing. Would be nice to have
I received my Arduino board in the mail yesterday and setup my first circuit with an FSR sensor and an LED using this great tutorial.
The LED lights up when force is applied to the sensor and its brightness is determined by how much force is applied. Here it is in action:
I’m looking forward to getting busy with some more complex projects using the FSR!
Spending upwards of eight hours a day sitting at a desk working on the computer takes a toll on your body. So over the last few years I’ve been thinking about ways to work my legs to keep my blood moving and muscles active while sitting at my desk.
My first thought was to try a typical hand/ped ergometer like this one:
I found though that because of the cycling motion, my knees would rise too high and hit the bottom of my desk and even if I could avoid that, the gross movement of the legs would work my hip joints causing me to rock in my chair. Not very conducive to focusing,
So rethinking it I decided that a more isolated pedal-based movement would be the way to go; no more knee hits and chair rocking.
I looked around to see what might be commercially available for this kind of thing but I didn’t find anything very appealing. Here are a couple of examples of related products that are marketed for what I was looking for:
My concern with these was that there was no real resistance to the pedal action and in turn would make the movements rather jerky which I’m pretty sure would turn most people off to these products after a bit of use.
I kept digging and I happened on the double bass drum pedal setup:
My friend Matt says that they’re popular among metalheads
But I thought it was perfect because it had a pedal for each foot, had resistance from the springs shown in the picture and was constructed of sturdy hardware.
I bought one from Amazon.
Right around this time I began thinking that if I’m going to be expending energy while I’m working at my desk, why not convert that energy to electricity? And that would add an additional motivation for using the pedals. I juice up my computer and monitors while I was at it. Hey, why not?
More to come in part 2!
Completed Bike Trailer!
Custom bike trailer I built. Finally complete and hitched up!
“Another satisfied customer” -Aaron. Myself and Aaron, master metal worker at his shop Trimount Ironworks in Dorchester. He taught me to weld and to work with metal. Couldn’t have done it without Aaron. Thanks Aaron!
Balancing Tabs
Tabs in web browsers are awesome. Want to view a new page but save the context of the current page? No problem. I shudder to think about going back to a tabless world.
But tabs can also be dangerous. I’ll be working on a website or just hyper-linking around and all of the sudden: where the heck am I? How did I get here? Where am I going?
And I’ll check out my tabs and they’ll be mad tabs open that don’t help to answer those questions. And usually, I’ll say, oh okay, I should be working on this now. Or I was looking into that. Then I’ll Proceed to open more tabs after choosing something.
Sometimes this is great. Like during very loose hyper-learning which is awesome for producing creative scattered brain showers (my Dad’s term .
But it’s bad for focus.
I guess it’s about achieving balance. And I don’t think it’s about delineating specific time slots for each because sometimes I just can’t focus on one particular thing and my time during those periods is better suited to ingesting data and connecting what might not be unconnected dots. Of course I think it’s important to recognize those times when the mind is an arrow capable of hitting focused targets and consciously work to keep the arrow pointed at the bullseye because of course cruising the web can be awesome for creativity and just thinking but it’s also a cheap drug.
Week in Review
Highlights from this past week:
- Last Sunday Mom put together a most delicious cheese fondue dinner complete with kielbasa, french bread, veggies and baby gherkins. The 30 year old fondue pot produced a ghostly high-pitched squeal as it kept the cheese nice and melty but all in all it held up very well. Ars, Mom, Dad, and I ate it in front of the fire. Warm food, warm house, warm people.
- On Tuesday I was crowned mayor of Christina’s Ice Cream on Foursquare. I picked up a pint of pistachio and a pint of coffee toffee frozen yogurt. It feels good to be the king.
- Christina made such deliciously memorable meals this week including pasta with homemade sauce and baked ginger veggies and garlic bread. She also made chicken parmesan with pastina. She definitely knows the path to my heart. <3
- Liz and Julio put on this great installation show at meme gallery in Cambridge called encontracosas or ‘found things’ that I went to on Friday Night. It was awesome. You’re encouraged to actually touch and play with all of the found things, move them around, stack them, spin them, mash them. All sorts of things. VHS cassettes, toys, furniture, photos, hair bands. All things lost or discarded at one point (or perhaps multiple points) and then found. It was cool to be part of the art like that. From the website: In MEME, encontracosas: real time weavings uses installation and improvisation to form paths, webs, ensembles and gathering points made from found materials and sounds, creating new axes of ‘meeting/finding’ each other and things in space. The axes of ‘meeting/finding’ each other was the coolest part. There were always little things around to play with while I met people, which seemed to aid in lubricating those exchanges in a neat way. That and the people I met were so friendly like those who run the gallery – Vella, Derrick, Phil, and Sandreen. Oh, and I got to spend some time with the wolf moon walking to and from meme. It was a beaut.
- Yesterday C and I went to 1369 while we waited for a table at the ECG for brunch. There was this neighborhood guy there that channeled some Daniel Johnston and he danced to the jangly music while he waited for his drink. He talked to C and I about how you used to be able to buy the male chicks that are now ‘discarded’ at egg houses for 5 cents around Easter. He was great.
- Then onto an excellent brunch at the ECG served by the always gracious and wonderful brunch captain. Art steers that ship and he steers it well. Incidentally, Drew Houston, the founder and ceo of Dropbox came into the ECG when C and I were waiting to be seated but didn’t stay after he found out about the wait. When I mentioned it to Art, he offered that the Grill could have shared a brunch platter to his Dropbox He and his team have created an awesome product for wicked easy sharing of files between computers and/or people and is worth checking out if you haven’t yet. Here’s a video of him giving a talk at Berkeley recently.
- Then tonight Matt and I met up, got jazzed up about work talk over a burrito, then went to a Haiti Relief Concert that my friend Adam helped organize. It was a good time and this one band called Zili Misik really rocked it. Here is a video (although it doesn’t really do their live music and energy justice):
See you in a week, week in review.
Shakshouka: It’s What’s for Dinner
This past Sunday I made a North African dish called Shakshouka. I was inspired by a food-travel show (a la No Reservations w/o all the sass) where the host went to Israel and visited a restaurant where the proprietor made up a gigantic pan of this stuff. It looked so good I had to try making it that night.
One of the neat things about the dish is that when it’s time, you plop eggs in and let them slow poach over the peppery stew slurry.
C and I both agree that it came out very tasty. We ate it with hummus, pita, and some simple homemade olive spread (chunky chopped olives, a bit of thyme and olive oil).
And even though there’s traditionally no meat in the dish (although you could certainly add sausage or other meat), it has a thick and beefy vibe along with the egg protein that doesn’t leave you missing it.
(I’ll include my recipe after the pics)
Cut up peppers hit the pan after sauteing the onions and garlic
Fresh peppers and onions up close
Neat texture on the wood spoon, right?
Just added generous amounts of cumin and coriander
Starting to come together
10-15 minutes into a steady simmer
Volcanic love
Eggs are in! It’s poaching time. You can see four here but there’s actually a fifth that was lost to the abyss in the top left.
Note the hummus on the table. It’s the perfect compliment for the shakshouka. We also had fresh and chunky olive spread with it. Also note our cat Petunia under my thumbs up. She’s the perfect compliment to shakshouka making.
The end result! Yum! Seriously.
Recipe
Thanks to Tamara, whose recipe I worked off of with some revisions along the way.
Ingredients (for four good-sized portions):
- 1/4 to 1/2 cup of olive oil (olive oil is a key component here and you won’t more than just a coating on the bottom of the pan)
- 2 medium to large onions chopped
- 6-10 garlic cloves minced (garlic is big in this dish too)
- 4 large bell peppers (red, green, yellow, and/or orange) knuckle-sized pieces or anything would work really
- 5 tsp cumin
- 3 tsp coriander
- 4-5 tsp paprika
- A dash or cayenne or red pepper flakes (optional)
- Salt and pepper to taste
- 1 28-oz can diced tomatoes
- 4 (or more or less) large eggs
Steps
- Saute the onions in the olive oil until translucent (not browned) in a large pan.
- Add the minced garlic and saute them w/ the onions for a few more minutes.
- Add the peppers and stir it all together
- Add the spices – cumin, coriander, paprika
- Saute all of that until peppers soften up
- Add the tomatoes
- Saute the entire mixture on low heat for 15 (or more minutes) stirring regularly along the way. Also taste and add salt and pepper to your liking.
- Now it’s time for the eggs! Take a spoon a push it into the top of the mixture to make a little hole where you want the egg to go. But don’t make it too deep. I lost an egg that way.
- The eggs will probably need 10 minutes or more from when you put them in. It all depends on how you like your yokes, a bit runny or more well done.
- Spoon and serve!
Great w/ pita and hummus!
Manny’s last homerun
My friend Jamie caught a great photo of Manny’s last home run at Fenway park:
http://www.jamesconnell.com/?p=106
