Convenient though they may be, [Trevor Faber] found some serious shortcomings in shifting spanners: their worm gears are slow to adjust and prone to jamming, they don’t apply even force to all faces of a bolt head, and without a ratchet, they’re rather slow. To overcome these limitations, he designed his own adjustable ratchet wrench.
The adjustment mechanism is based on a pair of plates with opposing slots; the wrench faces are mounted on pins which fit into these slots, and one plate rotates relative to the other, the faces slide inwards or outwards. A significant advantage of this design is that, since one plate is attached to the wrench’s handle, some of the torque applied to the wrench tightens its grip on the bolt. To let the wrench loosen as well as tighten bolts, [Trevor] simply mirrored the mechanism on the other side of the wrench. Manufacturing proved to be quite a challenge: laser cutting wasn’t precise enough for critical parts, and CNC control interpolation resulted in some rough curves which caused the mechanism to bind, but after numerous iterations, [Trevor] finally got a working tool.
To use the wrench, you twist an outer ring to open the jaws, place them over the bolt, then let them snap shut. One nice touch is that you can close this wrench over a bolt, let go of it, and do something else without the wrench falling off the bolt. Recessed bolts were a bit of an issue, but a chamfer ought to improve this. It probably won’t be replacing your socket set, but it looks like it could make the odd job more enjoyable.
If you prefer a more conventional shifting wrench, you can make a miniature out of an M20 nut. It’s also possible to make a shifting Allen wrench.
Thanks to [Adam Foley] for the tip!
The high part count of precise components with tight tolerances and costly machining will make this very expensive if ever produced commercialy. That being said, I applaud the cleaver design, skill, and determination it took to create it
Although, kudos of identifying the most obvious problem: that the mechanism bends under stress and goes out of alignment, binding it up. Many Makers would be completely stymied by that, but he did get it to work by proper analysis and design.
Too bad it’s only for hex cap bolts.
I have standardized on 7.4 sided bolts.
Great work, loved watching the design process. Very
I’m an electronics design guy so everything mechanical engineers do is very cool and impressive to me even though I don’t understand much!
reminds me of https://www.youtube.com/watch?v=8IewMXUzt7U (and adjustable allen key)
very hard to make the moving parts of a tool like this rigid enough to actually be useful and not deform when you reef on it.
No.
Too complicated.
Useless for toolbox, not good for emergency kit either.
Most cars are 99% 3 or 4 size fasteners anyhow.
If you don’t already know what those sizes are, what are you going to do with an adjustable ratchet on the side of the road?
Dowse with it?
‘Holy ratchet, point to the broken part!’
Also ‘shifting spanners’?
Is that some sort of B&D gizmo?
What exactly is he intending to crank this socket down on?
The hex head has always been a defective design concept. By its very geometry, the forces rounding the head and bending/breaking the tool far exceed the forces making torque on the bolt. Fewer sides (square) are better, and splines (external Torx) are better.
Trevor’s design is brilliant, even with its limitations. I doubt that it can ever be made as strong as an equivalent socket. It’s bulky. It might be vulnerable to contamination with grit. Still, even if he’s the only person who ever owns one, he’s made something to be proud of.