Category: Technical

Grabbed the electric adjustable bed from up the road earlier. Could tell it contained at least some angle-iron and a motor, as well as an oversized controller.

It’s about what I’ve come to expect from all commercially available “medical” appliances. Off-the-shelf parts in a design so basic it’s crude. It smacks of zero product development; no refinement beyond the first working demonstration model.

Controls all run on mains voltage so the flex to the massive hand-held controller is about half an inch thick, the controller itself being slightly larger than that used to control industrial gantry cranes. All angle-iron frame, welded, with M6 bolts and nylon washers as hinges. No nylocs, all counter-tightened slim nuts to hold them in place. Even using two bolts as load-bearing end-stops. Considering the bed has two separate “massage” vibration motors, it seems dangerous to use pivot nuts and hold the bed portions raised with a scheme that could easily shake loose over time (and many of the nuts were already loose enough to undo by hand). The internal control box that I expected to contain relays only contained some fuses and a small transformer (probably for the vibration timer in the controller), the rest of the box being 3/4s empty. Another off the shelf project box you could pick up from any electronics hobbiest shop. Connector bundles also held together with a project box. MDF covers for the vibration recesses have been neatly and pointlessly bevelled on all edges, where no-one will see it or or any wire would touch it. The vibration motors themselves have a bolt and washer as a weight drilled into the cooling fans at each end.
Also noticed there’s no packing on the pivot bolts for the actuators so they twist in their mounts when changing direction. This will surely lead to metal fatigue and sudden unexpected failure of the mounts in the actuators cast aluminium housings.

Why is it every single piece of consumer medical equipment is apparently designed as someone’s final GCSE Design & Technology project??

It’s no wonder the devices needed by our most vulnerable are also so expensive when they never refine the designs at all. Even a courteous bit of refinement could drop construction prices by a large amount. Even if they didn’t drop the sale price, the companies would make more money! Where’s the downside? Or is there some bit of safety legislation that demands any “medical” equipment be explicitly built like a 1920s farm tractor?

That said, I now have some short sections of sturdy angle-iron and a pair of mains 250Watt linear actuators rated at 2500N with about 200mm travel.
The reason for it being thrown out? They’d accidentally yanked the mains cable out of the controller box. I plugged the pins back in, changed the fuse, and it worked fine.
Except for a week outside, the foam mattress portion smelled like rancid fish.

Truly, it pays to remember that when something breaks, it generally only means one single part of it has actually broken.
The attitude of the consumer however is far more often that the magic box is dead, so they need a new one. Well, I suppose that is why they’re called consumers.

Wondering if the actuators would be sufficiently powerful to make a small crane. I doubt it actually. Could probably shift a large satellite dish or similar though.

[20/06/2010: Amalgamating old posts from “Dreamwidth Creative Blog” into sci-fi-fox.com to re-purpose DW blog account.]