ATLAS to KSSU Airline Trolley Castor Adapter

updated by 4 min read #3d printing

One of the castors on my KSSU airline trolley broke, and replacement KSSU castors are hard to find. ATLAS castors are easy to buy, so I mounted them on 3D-printed adapter plates. This post explains the two trolley standards, the adapter and the build.

ATLAS and KSSU#

Galley equipment such as trolleys, drawers and ovens follows one of a few size standards, so an airline can mix equipment from different manufacturers in the same galley. Trolleys with these standards arrived in the late 1960s, together with the first wide-body aircraft.

ATLASKSSU
Named afterAlitalia, TAP, Lufthansa, Air France, SabenaKLM, SAS, Swissair, UTA
Other usersabout 80 % of all airlinese.g. Cathay Pacific
Drawer guide rails60 mm apart30 mm apart

The names come from airline groups that also shared maintenance, operations and training for their wide-body fleets. Some sources name UTA instead of TAP as the “T” in ATLAS.

The two types look almost identical and differ only slightly in their dimensions, but they are not interchangeable. A full-size ATLAS trolley is about 810 mm long, 300 mm wide and 1030 mm high, and weighs around 15 kg empty.

The problem: no spare castors#

I own two airline trolleys: an ATLAS service trolley from Lufthansa and a KSSU trolley from Austrian Airlines. Austrian had used the KSSU trolley since 2004, certainly under harsh conditions. Recently one of its nylon rollers failed from material fatigue. The rollers are held by a riveted, hardened steel pin, so the whole castor had to be replaced.

Worn original KSSU castor with a double nylon roller
One of the original KSSU castors after almost two decades of service
Housing of the broken castor without its roller
Housing of the broken castor; the roller had already gone in the bin

I could not find replacement castors for KSSU trolleys. ATLAS castors, on the other hand, are easy to buy and very similar in design. The main difference is the spacing of the mounting holes.

The adapter#

An adapter plate between castor and trolley takes care of the hole spacing and keeps the brakes working. The ATLAS castors are a different height, so all four castors have to be replaced; otherwise the trolley would wobble.

  • Design: first revision by the engineering student Beatrice Zaage
  • Size: 77 × 91 × 7 mm
  • Material: PLA, 3D-printed with a honeycomb infill for torsional stiffness and compressive strength
  • Castor mounting: four 16 mm M5 countersunk screws, whose heads sit flush in the plate
  • Trolley mounting: the original KSSU bolts through the four outer holes
  • Centre recess: room for the brake rod
  • Files: a left and a right version, as STL: left, right
Sliced adapter cut open halfway, showing green perimeters around a yellow honeycomb infill
The adapter sliced with PrusaSlicer (12 % honeycomb infill), cut open at 4.4 mm: perimeters in green, infill in yellow

The model below is interactive; drag it to rotate.

Why the recess matters#

The pedals move a brake rod up and down. The rod presses a brake shoe inside the castor onto the rollers and locks them. The new castor has the same kind of brake, so the rod has to reach it through the middle of the adapter.

Brake rod protruding from the trolley's underside
The brake rod

Assembly#

New ATLAS castor mounted on the printed adapter plate
New ATLAS castor on the adapter
New castor with adapter next to an old KSSU castor
Left: new castor with adapter. Right: old castor, in very bad condition.

Here are all four castors fitted, shortly before the first test. The small gap between the front rollers and the pedals worried me (see below).

Underside of the trolley with all four new castors
Underside, fully assembled

Result#

The result looks remarkably good, and the brakes still work.

Trolley standing on a new castor with the grey adapter plate
Fully assembled trolley

Known issues#

  • Two of the holes for the KSSU bolts sit so close to the ATLAS castor’s holes that there is no room for washers.
  • During a full turn, the front rollers can hit the brake pedals. If that happens, shorten the pedal a little.

Trivia#

  • ATLAS and KSSU are not the only families. A third one, ACE, was specified by British Airways.
  • The trolleys’ design and safety requirements are written down in SAE standards: AS8056 for minimum design and performance, ARP4171 for safety during food and beverage service.
  • The KSSU airlines also split heavy maintenance among themselves; Swissair’s Zurich base, for example, maintained aircraft for the group.
  • Airline trolleys have a second life as furniture. The German retailer Manufactum even sold ATLAS-standard shelf inserts for trolleys and containers at home.

Sources#

cd ~/projects