Electric wheelchairs are responsible for giving back independence to a great many people the world over. They do have their limitations, however, including long recharge times and a general aversion to large amounts of water. Being weatherproof is one thing, but taking one to a waterpark is another thing entirely. Fear not, for The University of Pittsburgh has the answer: the air-powered wheelchair.
Known as the PneuMobility project, the chair relies on a couple of compressed air tanks as a power source. They appear to be a of composite construction, which would cut down on weight significantly and help reduce risk of injury in the case of a failure. The air is passed through a system of valves to a special compressed air motor, allowing the user to control the direction of travel. Unfortunately details on the drive system are scant — we’d love to know more about the design of the drivetrain! Reportedly a lot of the components come from the local hardware store, though we haven’t seen a whole lot of compressed air drive motors on the racks of Home Depot/Bunnings/et al.
Range for the wheelchairs is listed as about 1/3 of an electric wheelchair but recharging compressed air takes minutes, not hours. Developed by the university’s Human Engineering Research Laboratories, the wheelchair isn’t just a one off. There are plans to supply ten of the machines to the Morgan’s Wonderland amusement park to enable wheelchair users to share in the fun of the water park.
We’ve seen some great wheelchair hacks in the past, too – like this chair built specifically for the sand dunes! Video after the break.
[via Gizmodo, thanks Itay]
The motors from air-drive power tools might be suitable for experimental purposes,and buying them at Harbor Freight (lots of types, speeds, power levels, hoses, connectors) lowers the cost of entry.
Looks like the google search term for what they are using is ” Radial piston air motor”
This reminds me of an episode of Penn & Teller Bullshit, they were out hitting unusual religious traditions in this episode. They went to Israel where there was a small section of an engineering school dedicated to creatively exploiting loopholes in Orthodox Jewish law pairing engineers with religious scholars(apparently they go by the letter and not so much the ‘spirit’ of the law). I recall it was mostly enable Jewish disabled and emergency services to skirt and not have to outright break Jewish law. Anyways this guy was especially proud of an air powered wheelchair and was genuinely stunned when they basically jumped his shit while he with middling English really had no idea what was going on when everything changed in seconds from interview to attack on the whole reason for the institute. I just though it was a neat way to explore often ignored solutions which we always seem to throw electricity at.
*criticism sandwich*
Great story! I started to roll my eyes and then you got to the fun part. I’m imagining an Orthodox Jew in full getup on some homemade contraption.
Please proofread a bit more. Story is a little hard to follow, and some readers would have given up because of absent commas.
Your anecdote was interesting and I would actually like to hear more about the whole ‘Jewish disabled law’ thing. I’m ignorant of most (legal?) religious matters of the Old Testament.
I have been wanting to MacGyver-up an air-powered something for years. Article has rekindled my desire for air tanks on wheels. ;)
Look up “Eruv”, which circumvents the Jewish rule/law against ‘work’ during the Sabbath by defining large sections of a city as a “private dwelling”…
That’s a bit of a misrepresentation. An eruv (a) only addresses the prohibited labor of carrying/transferring objects in/out of and through public spaces, and (b) it only mitigates situations in which the prohibition is rabbinic. Biblical Jewish law prohibits such transfers in a limited set of circumstances. At some point, laws were enacted which expanded those prohibitions to additional situations, primarily as a way of making sure that the biblical laws wouldn’t be violate by mistake. The same rabbis who enacted those laws provided a limited workaround – an eruv.
I’m not very familiar with the medical workarounds described by Dave, but from what I gather they are also intended to address rabbinical prohibitions, in situations where they would impact the health (or quality of life) of people with serious medical conditions.
There is no need for a “special compressed air motor”, as any basic steam engine runs on compressed air. (That’s how model engines are tested prior to getting around to building the boiler.) If my wet RAM refresh cycles are holding up, then the “Brotherhood” three cylinder steam engine was used with compressed air to propel torpedos. Ah, yes, look at “torpedo” in wikipedia.
I’d think they use some sort of turbine. Pistons don’t have that great efficiency and you can’t easily reverse the rotation.
Stanley Steamer easily reversed.
turbines are usually worse efficiency wise.
Different speed profiles. Turbines are no good at low speed, but are more efficient at their design-speed. You don’t see piston-powered power stations do you?
Pistons are far better than turbines for compressed air, and you can indeed reverse a steam engine with the pull of a lever. Steam locomotives would not have become successful without a reversing mechanism. The lever modifies how the piston and the steam redirection valve are related. I don’t know the actual terms for those parts.
In reality, turbines are impractical at low power scale. One manufacturer stated that you wouldn’t bother with them under 1 megawatt output. But, yes a 500 MW turbine _is_ efficient. A reciprocating steam/compressed_air engine is better at modest power and modest speed. A turbine needs to run at very high speeds to develop any useful power.
Turbines are also horrifically expensive to manufacture, with their thousands of vanes, each more complex to machine than a piston. (OK, a Tesla turbine doesn’t have any, but look on youtube, for anyone actually able to drive a substantial load with one.)
Reversing a reciprocating steam engine is merely a matter of valve timing. To reverse one with suitable valve linkage, the process it to grab the lever, and move it past centre positon, like one of the steering levers on a bobcat or bulldozer. That is not overly demanding.
Wouldn’t regulated liquid CO2 or compressed nitrogen offer a higher energy density and potential range? CO2 is relatively easy to come by as well as handle.
Yes, at the cost of having to source, store, distribute and handle it (rather than running a high pressure air compressor), the phase change materials will give great expansion power. It will also weigh more in the tank.
As a one-off or experiment that’s often pretty simple, but as an ongoing installation it gets complicated since you have delivery schedules, cryo storage, distribution & filling systems etc. to go with it.
Worth a try though, IMHO.
Afik, the fast-food at the water park will already have a supply chain for liquid CO2. Just have to scale it up to support the chairs.
Yea but with compressed air you don’t need to scale up anything. You already have high pressure compressors in the market. No need to reinvent things when they are already there.
Good point – though they make more money on fizzywater :-)
Also it occurred to me that this would require heated valves and stuff to counter the cooling/ice accumulation which would take….let’s see…electricity?
Air is 80% Nitrogen, the extra O2 doesn’t hurt in the application as a pressure power source. And air is cheap. So there is no gain in using more expensive Nitrogen.
CO2 is another thing and covered by Thinkerer’s post.
I believe he meant liquid N2 which is pretty readily available, but would have the same freezing problems.
If they sell air tools at the hardware store, there’s air powered motors…
I remember a post somewhere that involved using a part of a bicycle’s frame to hold compressed air.
Need a boost up the hill? Open valve #1.
Need to brake going downhill? Slowly oen valve #2.
Time to visit the air-tool section again!
on a less “touchy feely” note…
the US Navy is testing an electric version of their Phalanx gun turrets, which are run on compressed air.
Yes, the Phalanx are more in the “touchy shreddy” category.
B^)
guaranteed to “blow” you away?
sorry couldn’t help it
Great initiative. Hope it works out well especially for electrically hostile environments. Is there a video of the chair in operation where we can hear the noise it generates while moving?
You can hear it a little bit toward the end of the video.
As someone who needs a mobility scooter, the noise would probably make this a no-go for me. Not planning on going to any water parks anyway.
Since we’re into air-powered electricity alternatives it’s worth mentioning that there’s a good-sized furniture factory near here, run by some members of the (no electricity) Amish community, that runs entirely on compressed air. Saws, planers, sanders, blowers etc. have all had air motors swapped in and the whole thing runs on a massive (diesel) air compressor/tank installation.
Lighting, you ask? Gas lights – really, though they’re behind flame screens.
So the Amish are allowed to use diesel power but not electrical?
No electrical system, so it is apparently okay. Presumably a compressed air start for the thing – it’s either that or draft horses – but I didn’t ask. You’ll have to ask them why they don’t have diesel engines in their buggies and all the rest of “hey, wait..” thoughts that follow things like this.
Amish teenagers have been ticketed for too loud noise and speeding – in their hopped up horsedrawn buggies. They let the kids install boom boxes, lights and other things on their buggies and IIRC there’s a 12 MPH or so speed limit some places for horsedrawn vehicles. Sometimes a buggy just isn’t enough speed for an Amish kid. One group was nailed for 110 MPH in a minivan, drunk driving too.
When they are coming of age, they have to choose between leaving the Amish community or giving up all use of electricity and the other modern stuff to stay with the Amish. Some Amish communities do have one phone, typically outside of any building and on the outskirts of the village or down the road a ways. For emergency use only.
They have a bigger problem with relying on tech they can’t make than using tech itself, but what tech they’ll use depends on what their group leaders have decided on a case-by-case basis.
It depends on the community and the their justification.
There is/was an Amish tobacco salesman who carried a cellphone.
He considered it a necessary tool for his work.
Some Amish factories do use electric generators, gas/diesel/propane/etc. to them it’s okay because it is not attached to the “evil” grid.
Mennonite are similar, but different, the farmer/furniture maker I know has telephone, refrigerator, power tools, attached to the grid, and a tractor, but uses a buggy to get his children to school and his family to church.
The Amish near here have “drivers”, non-Amish who will taxi them to stores/doctor appointments/etc.
Instead of salesman, I meant “broker”.
In the 40’s there were a spate of toys powered by those CO2 cartridges used in selter-water dispensers. There were model cars and planes. Just use a tool to puncture the little diaphragm and off they go with a great whoosh.
The only problem was, the whoosh was usually TOO great. Too much thrust.
Then someone came out with a CO2 motor. It looked much like a model airplane motor, except instead of a fuel line, there was a tube connection the motor to a cartridge holder.
The design was simplicity itself. At the top of the cylinder, there was a spring-loaded ball valve that blocked the flow of gas. On top of the piston was a pin. Each time the piston neared top center, the pin pushed the ball up, admitting a puff of CO2.
The (literally) coolest part of the whole deal was the temperature. Gas cools when it expands, so instead of the engine being hot after a run, it was icy cold, with frost all over its “cooling fins.”
The “airhog” planes run similarly tough on compressed air rather than vaporizing liquid. CO2 were sold at least into the 1970s (when I got busy with college and quit paying attention). The Russians exported these for a while in the 90s – they pop up on Ebay once in a while. Video complete with frost:
https://youtu.be/E91MKc1IYDc
Paintball tanks are filled with CO2 and almost every town has a place to refill the tanks.
Here is a related idea. Instead of a battery powered riding lawn mower, how about doing the same with compressed air! Same principle here, no need for a long recharge time.
So far everyone has ignored the fact that squashing air and keeping it in a bottle takes a phenomenal amount of energy compared to electric propulsion, be it going along propulsion or spinning a blade propulsion.
Why not just waterproof an electric wheelchair?
We’ve had electric underwater things for years.
+1 for knowing physics.
But then again, this is not engineering weekly, this is Hack-a-Day, isn’t it? Doesn’t have to be practical or even sensible. But it should be a novel entertaining idea. IMO, this is neither, but that is just me doing the thinking…
I once tinkered with the idea of powering a very lightweight go-kart with compressed air. Don’t know what pressure is used in SCUBA tanks, but the oxygen tank in a welding rig is pressurized to 2000 psi. If you calculate the potential energy in such a tank is Enormous!
I was worried that it wouldn’t have enough power to go to the end of the block and back. Turns out, you could run it on a drag strip, and blow the doors off of most cars.
SCUBA, Nitrogen paintball, and SCBA tanks are roughly 3000-4500psi.
HPA (high pressure air) tanks are more difficult to fill than the air compressor you might have in your garage and they’re not ubiquitous. It won’t matter if it takes minutes to fill if you can’t find somewhere to do it or get there in the first place.
A water park using these would need a SCUBA tank filling compressor.
Lots of fire departments in the US will fill SCUBA tanks since they have to fill their SCBA tanks. Dive shops are easily found near the coast or even land locked places with a history of quarrying.
If anybody wants any more tech specs, HERL is the basement of our building I’ll go down stairs ask.
Side note: I hope someone in the hackerspace makes a blueprint for a DIY high pressure compresser one day. Or better yet, a three stage gas liquifier.
DIY and high pressure air are not a good combo. You fuck up – it’s gonna get ugly.
Friend had a SCUBA tank compressor in a shed filling tanks. The high pressure hose burst. Just the volume of air in that hose alone was enough to smash both windows of that shed.
And clean the tanks with soapy water only!
Most solvents weaken the fiberglass construction.
India’s Tata proposed a compressed air powered car. Here is a Google Search Link: https://www.google.ca/#q=india+compressed+air+powered+car&spf=385
Looks like good alternative to battery. Can someone estimate overall system cost per stored kwh?
the motors used in this chair would alost certainly be vane motors.
they are widely used in things like air tools, silos and pretty much anywhere you need high torque in a small package.
Mid 90’s, Joplin Missouri, company existed (I think on a government grant) and was converting Geo Metros to run on compressed air. Pnumecar or something like that. MASSIVE air tanks mounted on the roof, nearly the length of the car. You would sometimes see them driving around town. It was a “clean car” program. Just ignore the small block Chevy V8 running the air compressor behind the shop.
Model steam engines, the ones that will run on burning alcohol. Put dry ice pellets in the water tank instead of water. No fire needed. As the dry ice sublimates the vapor will drive the piston just like steam does. It’s common to test a steam engine on compressed air as it will work the same, just a lot of wasted fuel in compressing the air. But good for a cold test.