SUPERMARKET TROLLEY LINKAGE
 
 

Our client has MS and relies on her wheelchair and help to get around,  but found that her new wheelchair had side frames that were much further back than usual, such that she could no longer use the special wheelchair trolleys at her local Morrisons supermarket when she went shopping with her carer. Using a separate trolley significantly increases the time to do the shopping as well as being a bit impractical.
 
Transferring to one of the in-store electric buggies which are also available was out of the question.
 
The solution involves a removeable aluminium frame with longer arms which clamp to the wheelchair frame hand grips, using special clamps, and then onto the rear of the trolley. The existing trolley linkages can be tucked out of the way as they aren't needed.
 
The frame is also constructed so it can be taken apart for storage without any loss of strength, by undoing hand wheels at the two corners. It is covered in heat-shrink sleeve for a durable finish and improved grip when attaching/detaching it.
 
 
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Trolley linkage in use, to the delight of client and carer.
 
The available trolleys showing the standard linkages and the back rail to which our frame is attached.
The completed aluminium frame made from channel, rectangular tube and flat bar supplied by Paul Hill.
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Detail of a clamp for the wheelchair hand grips. Note the rectangular tube in the L/H picture appears solid, as a bearing has been welded into the end for additional strength.
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Detail of the two trolley clamps showing the Polymorph moulded jaws, and the piece of scrap copper tube used to ensure the moulding accurately reflected the bar of the same diameter at the rear of the trolley.
 
Polymorph - low temperature themoplastic granules - are great for fabricating parts like this. Just pop them in v.hot water and squeeze the granules together when they turn clear, mould, and allow to cool. The result has similar properties to nylon.
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Detail of the corner joints. The rectangular tube has a simple bearing inside, to cut down wear around the hole and stop the tube being squashed and mishaped if the hand wheel is overtightened - which could jam it in place. This bearing is secured with machine screws front and back.
Captive M8 stainless bolt.
We considered the slight risk that if a carer accidentally lost grip of the frame when attaching/detaching it from the trolley, it could swing down onto the clients legs (trolley brackets first). Eventhough aluminium has been used to keep down the weight, there is still enough to cause a bit of bruising.
 
Adding some padding was easier than trying to damp the movement at the wheelchair end, and more reliable than some sort of "stop" at that end where the weight of the dropping frame might still be enough to lever the clamps off if they weren't on tight enough.
 
An aluminium tube was welded to a couple of brackets and secured to the back of the trolley clamps.  Heavy duty 22mm copper pipe foam insulation was clipped around it and secured with velcro straps. This was then tested (on the engineer, not the client!).  
Pipe insulation forms an effective cushion.
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Harrogate and Ripon Group