Wheelchair footplate - ideas?

big-all · 22 Aug 2018

ok thinking outside the box
rather oversized feet shapes [clown type double wide toe space]
perhaps brightly coloured
with feet comfortably positioned a pivot bolt through the heel that can be countersunk flat
with perhaps a set position or slot at the toes so the they can be pivoted in but easily pushed out but limited
you would off course need a lip around the outer edge to maintain the foot
the pivot bolt would have to be perhaps 2" in from the edge as would the support point at the front

ChrisR · 22 Aug 2018

writ but I hadn't pressed Post - reply to earlier point, #15:-

Hence the opening comment, first post, above, "First thought was to make it 24mm at the edge,.....".
There's no suggestion of putting a hinge on 12mm.

I think I can do what I want with two piano hinges, spot welded to make a Z which opens both ways.

to the OTB post -

can you sketch it?

big-all · 22 Aug 2018

cant do sketch up or even get photos from one place to another -----
------ yes most can easily but i cant

ok i am going to step back here
the footrest additions would need to support perhaps 100kg without failing to be safe
you may be fine with less strength but i dont know
so please as you go make sure you put you full weight on the extension outer unsupported edge to make sure its safe

ChrisR · 22 Aug 2018

I want it to fail if I stand on it, but not in a damaging way.
EG:

Where red and green are super-magnets, red glued to the middle leaf, green fixed but jiggly in the wood. (only drawn once).
Each pair can hold a huge weight, like 20kg . (It can attract to the other hinge leaf - that's fine as long as it can't reach it it won't be strong (PVC tape will prevent if necessary). Or make a hole in it.)

Drawing - try in Word:
Format > Align > Grid settings : Snap to Grid and Show Gridlines

Insert > Shapes
bottom thing - New Drawing Canvas - makes it easier later.
Insert your shape.
Edit Points to adjust it
Right-click the shape outline (quickly) to format it

When done use the pointer to draw all round what you want
Ctrl-C (or hit Prt Screen but then you have to Crop later)
Go to Paint
Ctrl-V
Save As thing.jpg

Then Upload that .

Word isn't great, but it's there and there's loads of online help.

big-all · 22 Aug 2018

you are misunderstanding the mechanics an up to mean perhaps half that so 10kg
you now have leverage and a fulcrum [pivot point]so your now 10kg holding force will now support perhaps 1kg
you now add on active load[bouncing about in motion] halving the the grip
if you dont understand what i am saying about leverage take a 2L bottle you could carry about with you all day the hold it at full arms length

ChrisR · 22 Aug 2018

Sure, there's a lever.
Are you assuming only one magnet pair, badly placed components, or supporting more than one child's foot, or something else?
I've used magnets before, hence the red ones and "wiggle" note which I didn't explain. They're ok.
I'd run the numbers already allowing a 4:1 fudge factor. I can make it support several times the weight I want it to with enough magnetry - there's plenty of room/options.

If she kept "snapping" the flap, she'd learn not to press so hard. It would be on a spring of some sort so it would snap back up.

That was a 2 minute sketch not a finished design!

big-all · 22 Aug 2018

ok i wont pretend to have a clue as to what is the finished design

just keep in mind 2 magnets face to face 100% grip
2 magnets touching one edge but a lmm gap the other perhaps 50% loss off pull
1mm gap all round perhaps 70% loss off pull
if you use wood or any material that expands or contracts without adjustment to the magnets they will go out off adjustment

ChrisR · 22 Aug 2018

Yes, I know, been there, hence "wiggle". If you let them align....
That's why cupboard catches usually have movable elements.
1mm gap is a lot more than 50% loss of holding force. 1mm sideways slide on a 3/4" magnet isn't so critical. The lines of flux curve.
"Exterior" ply is pretty stable. Never use the sheds cheapo stuff, it's full of voids. I doubt she'll be going across fields of wet grass but I'll tell her Mum to put a bin bag over it is she does!

It'll only have to last a couple of years. Then she'll likely need another chair. This one will be scrap, and the NHS spends another £4k...

mattylad · 26 Aug 2018

We absolutly need to see a youtube video of the finished item in action.

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Wheelchair footplate - ideas?

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