Hanging via rim as @arellcat points out is simply a reversal of the loading when a bike is ridden but with a substantially reduced load.
The Class 156 hook system was designed (sic) by Interfleet who seem to have ignored attempts to offer advice. Hanging bikes up, where the whole bike has to be lifted off the floor presents an action at or beyond the limits set the HSE Manual Handling Regulations(MHOR 1992) so any injury sustained by a person using badly designed bike stowage, where the lifting is outside of the limits, could press for a Section 3 prosecution (HSAWA 1974) where the site owner/manager has created a condition where harm can be caused to a non-employee, through the failure to perform due diligence (to prevent harm) in designing or managing the system used by the non-employee.
I can write a small paper on why the Class 156 design is so bad, and how the hooks are always working loose. A well designed vertical stowage system uses the weight of the bike to press the tyres against the wall/frame, and to hold the bike perpendicular to the hook mounting surface (plane) See the Tenement cycle parking rack installed for Edinburgh trial in 2005 (close near to Commonwealth Pool)
No idea how the idiotic design came up with hanging bikes up by rear wheel, as this places handlebars in perfect place to smash into your knees, or trip over, and the dire positioning of the hooks relative to the 'wall' face with no side bearing to hold the bike perpendicular to this means that bikes crash around, as the straps (with no instructions on how to use them) won't stop this.
The Class 153 conversions are using a stored energy lifting hook (marketed by Falco) - this design has been around for at least 20 years. It is basic and entirely mechanical, pull the arm down and charge the spring, with the arm held in place by a detent stop. Place bike front wheel on hook and tug back lightly to disengage the detent, and the stored energy in the spring assists the lifting process.
The stowage system devised for the new Stadler Merseyrail trains is almost testes canisae it turns the front wheel whilst still having the weight of the bike pressing the front tyre against the back of the seat and sliding the wheel down the hook to press the side of the rim against a face to keep the bike upright, with the rear wheel on the floor. With bars turned by around 12-15 degrees bikes can be stacked very close together.
Pictures are available
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