Truly modern electric wheelchair design – part 2
This article follows my original article that set out the essentially 19th century design and manufacturer of electric wheelchairs foisted on to disabled people by an industry motivated more by greed than desire to improve their products of the health and well-being of their customers.
In that article I explained several problems with currently available models some of which were:
- Use of heavy, inefficient, outdated electric motors
- Appalling design with little, if any, thought given to the practicalities of (for example) something as simple as folding the backrest to reduce the size of the wheelchair for transportation.
In my previous article I made a comparison between the design, production costs and testing requirements of the 27,000 euros priced wheelchair that was being proposed to me and a 23,000 euros BMW 116 car. I won’t repeat myself, just restate the point that the car is a thousand times more complex, is made of a thousand times more component parts, is crash-tested far more rigorously than any wheelchair and contains many more creature comforts than any wheelchair on the market.
I had reason yesterday to peruse the service manual for the Ford Galaxy minivan (all 4,402 pages of it – just to provide a fair comparison with the 62 pages that detail how to service every part of the Luca wheelchair I’m sitting in) that carries my existing, cumbersome wheelchair. While looking through the manual I came across an exploded diagram and description of the main components of the driver seat.
But before getting to that I’d like to show what a “modern” wheelchair looks like. The chair I am current sitting in is a Luca Q. Luca, a Dutch company whose chairs make at least a passing nod at practicality and design, has been bought by Invacare since I purchased this chair and Invacare is currently busy withdrawing Luca’s product range from the market. Draw your own conclusions. For me, it means I am currently busy trying to buy up a stock of spares that I know easily and repeatedly break before they become unavailable – forcing me to buy another wheelchair for the sake of some small but essential and no longer available spare part – but let’s not get distracted.
The Luca Q at least hides its seat motors under the seat – unlike say the Otto Bock B600 and many more “high end” wheelchairs that hang a massive motor and piston behind the back rest – just to make the backrest recline.
So, let’s look at the Luca Q – one of the better electric wheelchair designs.
Having looked at one of the more practical wheelchair seats on the market (I can tell you in case it’s not already obvious, that the seat appears crude, ugly and shouts “cripple” from every angle) let’s look at a seat fitted to a car as specialist and uncommon as a Ford minivan.
The numbered parts refer to
1 Servo motor, electrically adjustable backrest
2 Front belt buckle
3 Servo motors, seat height and seat angle electric adjustment
4 Heated Seat Module
5 Servo motor, forward and rearward motion
6 Power seat module
7 Switch group for electrically adjustable driver’s seat
8 Blower motors, front seat
9 Side airbag
Ok – we don’t need an airbag on a wheelchair. But look at the design (EVERYTHING is enclosed within the seat itself) and the functionality.
Here’s how Ford describes the seat’s functions:
- Vertical adjustment of the front of the seat cushion;
- Vertical adjustment of the rear of the seat cushion;
- Horizontal seat movement along the seat track through a mechanical worm drive;
- Seat backrest position adjustment of the backrest rake angle.
The driver seat with full eight-way power adjusted seats may have an option of driver seat memory. This option has an eight-way memory seat switch, additional memory motors and a memory module.
This is the specification of the front seats fitted to my car – omitting only the lockable storage containers fitted beneath each seat – in the space that a wheelchair similar to the Luca Q uses to place its ridiculously huge motors, gearboxes and massive batteries.
Not only is there room to place all the actuating motors inside the seat its control electronics are contained there too and it has creature comforts including fan forced ventilation and heating – something that could easily be achieved on a wheelchair iwth the additional of a simple electric Peltier device to provide the cool/warm airflow in place of a car’s full climate control mechanism.
Just in case it’s not already obvious
Comparing the wheelchair seat to the car seat one thing stands out above all else. The wheelchair seat is constructed from cheap “parts-bin special” components – essentially, whatever can be bought cheapest frm a manufaturer advertising on Alibaba. The car seat use custom made parts designed to accomplish as specific purpose as well as possible.
Back to the car seat
I’d like to draw your attention to the back rest motor (Item 1 on the diagram).A more detailed view of the entire mechanism is this:
Note the small size of the entire mechanism and that, simply by being fitted to the correct place (the seatback hinge) it is possible to tilt the backrest through a complete 180 degree arc – from flat bed to folded onto the seat base all under electrical control – with no need to detach anything or play with fiddly cicrlips that tend to fly off into bushes
Already we can see that this seat is FAR easier for a disabled person to use than anything currently fitted to an electric wheelchair.
So, lets; turn to the seat lift and tilt mechanism. The Ford motors that do this are shown as items 3 on the exploded diagram. Individually they look like this:
A compact mechanism simply because it is placed in the correct position to make use of the maximum (as opposed to minimum) leverage. I accept that the range of height adjustment on a car seat is nowhere near that required by an electric wheelchair that might need to raise 12~18 inches (30~45 cm) but I have already explained it is possible to design a lightweight alloy scissor lift mechanism that folds fold flatter than the crude, heavy steel one fitted to the Luica and use a simple worm gear mechanism to push/pull the lower slide inside its rack or even fit small direct-drive motors with a worm-drive gearbox to drive the mechanism directly to provide the necessary amount of lift.
So, let’s look for a compact, lightweight worm-drive mechanism. Oh look, found one!
Turning to the part of the Ford mechanism that moves the seat back and forth to accommodate different leg lengths. the design of the mechanism is shown here:
and its operation can be more clearly seen in Item 5 on the exploded diagram, above. In short, the motor simply turns two flexible worm drive cables that engage with fixed gear parts attached to the seat runners so that when the motor turns the seat moves backward or forwards as commanded.
It;s easy to see how such a simple mechanism could be adapted to drive a scissor lift .. OR .. if the seat runner were extended and the front part radiused to offer a vertical part, how the seat base could be made to tilt fully upright … add some matching control to tilt the— back rest and leg hangers as the seat base became vertical and ,,, you have a simple wheelchair seat design that provides a standing facility. Maybe we don’t need that scissor lift at all?
Is it safe?
To anyone wondering whether such a seat using motorised components so much smaller and lighter than the great iron lumps used in current wheelchairs would be safe or practical I would say this. Car seats have to survive a high speed crash-test head-on into a 30 ton concrete block and must not move or break but remain serviceable and supportive to prevent whiplash injuries to car occupants. Such a test is an order of magnitude grater than any test a wheelchair seat is subjected to. Car crash tests mean that the lightweight motor mechanisms used (for example) to control the backrest recline must be strong enough not to break even under these extreme loads.
Great – for an able bodied person – But what about a disabled body that cannot lift itself.
Car seats are designed to accommodate the maximum range of human body shapes and sizes. That means in practice that if a 300lb (~140Kg) human chooses to sit in one of these Ford seats, reclines it back into the bed position then pushes the button to raise the seat back to an upright position – without offering any physical help – just relying on the seat motors to do the job – the seat will do it. Equally it will happily accomplish all its other functions with as much load placed upon it. And still pass far more rigorous crash tests than any existing wheelchair seat is ever subjected to.
So car seats are designed and built way better than wheelchair seats
Yes. So let’s look at what more we might do with one to make it more suitable or comfortable for a disable person.
In my previous article I mentioned that I also own a Maserati with even fancier electrically controlled seats. Functions that I find useful when driving the car and which would prove equally useful in a wheelchair. In addition to everything the Ford seats offer, the Maserati seats provide:
- Electrically adjustable lumbar support
- Electrically adjustable seat squab cushion position (ie; the side cushions move in or out to provide the desired level of lateral support for the legs)
- Electrically adjustable seatback side cushion positioning to provide the desired level of lateral upper body support
- Electrically adjustable upper back suport
- Electric “Shiatsu” massage facility with variable patterns
- Electrically adjustable headrest height, reach and angle
Of these only the electrically adjustable headrest might seem a luxury too far – that is, until you imagine having a single button which when pressed, drops the backrest onto the seat base, draws in the headrest to minimise length and perhaps drops the entire chassis to minimise height – making the wheelchair as compact as possible for transportation.
Then the utility of even a “luxury” feature becomes obvious.
Throw in othe common features of current car seats – such as position memory settings – my Ford provides three – supposedly for different drivers or passengers. But repurposed to wheelchair use I would set one for my preferred tilt and recline settings when working at my desk, another to make the chair as low as possible to get under typical restaurant dining tables and a third to stand me up when I want to talk to visitors or reach supermarket shelves without having to wait for a passer-by I can beg for help.
Surely this is fantasy – it couldn’t possibly be done now!
Yes it can! I’ll give a couple of examples – there are many more.
Take a look at the German company Greiner (website: https://www.greiner-gmbh.de/en/traffic.html) and look at the Sport and Touring standard seats you can buy from them off the shelf today. Feel free to compare them to the specification I outline above – neither seat is a perfect match but they come pretty close – the Touring model folds flat and even has in-built back massage. Then note their Seat Development program – which offers design,development and manufacturing of even small series of seats.
Another example that comes very close is from the German manufacturer Recaro – whose seats graced all my race cars. Their Orthoped model (https://www.recaro-automotive.com/us/product-areas-us/aftermarket-seats/products/orthoped.html) comes quite close to my specification including lumbar support, extendible thigh support, climate control, power adjustable back bolsters, powered headrest and collapsible backrest (see:https://www.recaro-automotive.com/us/product-areas-us/aftermarket-seats/products/orthoped.html) – oh – and its weight including all the in-built electric motors and electronic control packs? 17.2Kg. Take that wheelchair manufacturers!
As for comfort and support I can attest that a Recaro race seat gave me enough lateral suppert to endure +1G cornering loads (that’s a 2G swing when you drive a chicane or S-bend) over 2 hour race distances and kept me entirely uninjured during an unfortunate meeting I had with a straw bale that registered a peak +86G impact in the car’s telemetry.
I’m sure if someone talked nicely to Recaro’s or Greiner’s development department they would be happy to produce a seat to the precise specification I have described – all based around a carbon fibre shell with an all-up weight of ~10Kg and every convenience we could ask for.
What about cost?
I hear your fear. The Recaro seat mentioned above is available to order off-the-shelf at a retail price of 2.500 ~ 3.000 euros. Recall that the price I was quoted for the wheelchair seat whose lumbar, thigh and lateral support cushions were held in place with strips of velcro was a mere 13,500 euros – meaning that you could buy 4 better built and specified Recaro orthapadeic seats for the price of one piece of crap.
I must contact Maserati to find out who makes their seats as one of those in a simpler cloth would potentially completely cover all the parts of my specification.
Existing wheelchair manufacturers
Rest assured that I intend to keep this campaign going – showing piece by piece the deficiencies in the cruddy products you foist on to the market at vastly inflated prices until you either start building better, more affordable products or someone new takes up the batten and starts to drive you out of business.
I (and from the responses already received to my first article) many other disabled people are fed up with the crap and ripoff pricing you subject us to.