This project is one we (Bert Peters, Bruno De Naeyer & Francis Van Poucke) did for school the general idea was to help develop a tool or aid to help a person with a physical limitation. The persons in this assignment all had a trained dog to help them around the house.
Our person was unable to use his body except his right arm (just enough to operatie his wheelchair joystick) and his head. So his problem is he can't drink alone his mother or a social worker has to come and place the cup at his lips otherwise he is simply unable to drink.
Now our idea was to make an arm mechanism that would bring a tube in his reach so he could drink from it when he wants and to remove it when he is done, this whole system would be operated by his dog.
The following instructable will be devided in the procedure to make and dimension the arm mechanism and the mechanism to mount it on the wheelchair (because every wheelchair is differently customized).
In the video (in dutch) you can see why luc needs our mechanism and also our mechanism in action.
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Step 1: Dimensioning the Arm (can Be Skipped)
(if the distance from the back of the wheelchair to the mouth is about 40cm (inch is for dummies) you an just use my dimensions)
Since in didn't have the patience to think of a way to calculate the radius and distance of the arm I made a parametric model of the arm and added a shape that roughly represented the dimensions of the head + backside of the wheelchair.
So here i got: the amount of parts, the amount the middle hole should be off center, the total length of each part & the angle under wich the mounting system should be mounted.
note: model is in the metric system, CAD packet is Siemens NX 8.5
Step 2: Making the Lasercut File
you can also skip this if you 'll use my files
First make 2D drawings of the CAD model components (I made so spares yust in case), you can add all the components in one drawing and dont place any measures.
Now print or export this file as a .pdf document and open it in Adobe Illustrator or Inkscape.
Remove all unwanted lines.
Make sure the document is in RGB color mode size 450 mm x 600 mm (or the size of your lasercutter)
Give the remaining ones a thickness of 0,025 mm
And give them the collor (255,0,0) so max red and all the others zero.
Now 'print' this file
Make sure the pointer is at the right place (and snap to it)
Change your material to the one you are using and the right thickness (make sure the material is flat!)(also after clicking OK go back and check if the thickness is still there it sometimes isn't)
Now make sire the air and filter are turned on.
Atlast press play and wait for a bit (about 20 minutes with ABS 4mm).
Don't forget to let the filter go on for a bit after finishing because it stinks!)
And you can go on to the next step.
Step 3: Assembling the Arm
To assemble the arm:
Start by putting the needed amout of 'normal' pieces in stacks so the holes all align (the short sides to the center of the bend)(there is a photo included that shows this with green for the short and red for the long ones).
Now you can start to rivet them together but beware of a few things:
>plastic deforms instead of the rivets so i only tightened them just enough losened the pliers and removed the nails with a hammer instead of letting the piers remove the nail and ruin the ABS.
>to lessen the friction in the arm make sure the smooth sides of the plasic face one another (if it has rough sides)
Now take your time because rivets are difficult to losen without damaging what they been put into, maybe first try with one of the pieces you have left over.
Step 4: Adding the Velcro Strips
To mount the hose to the arm contraprion we use velcro so we might be able to change the tube later on.
just use a tiny screw (and maybe some glue) and srew it tightly somwhere it wont hinder the arm 's movement. If the screws protrude from the other side be sure to file them away to not hinder opening and closing.
Step 5: Wheelchair Mount
Now this pieve is entirely dependant on the wheelchair you make this for so maybe you will have to design a different piece for this.
In our case where it met the wheelchair it had to be bent to fit behind the mounting place for the second joystick in the back. It also needed holes 4,7mm appart for the arm and a slit for where it would be screwed on the wheelchair (adjustable).
I first bought a standard alu profile 2mm thick and 2 by 4 cm L profile of 1m in length.
So now lets start by measuring I need 5cm for the slit and it can protrude 17 cm from the side of the wheelchair so that makes it 22cm long.
I proceed to drill the holes in the right diameter for the rivets and a bigger one where I ll make the slit.
to make the slit I used a milling machine (ordinairy no CNC) and started from the drilled hole to make a line and afterward pass again to make the line a bit thicker.
Now proceed to remove the excess material with a file and sanding paper I also removed all the sharp angels just in case.
Now to ply the piece with a bit of a bend i used a machine like seen in the photographs but instead of making one sharp torn I made multiple small ones to get a smooth bend, I did however have to remove a few dents afterwards.
When you're finished bending the piece you can saw the rest off and also remove the sharp angles with a file and some sanding paper.
Step 6: Putting Everything Together
Rivet the arm to the aluminium profile.
Add the tube in the velcro.
Remove the original joystick take longer screws and put it all back together.
the Bottle goes into the backpack on the backside of the wheelchair.