If you are into LEGO RC models you will be happy to discover that he legendary Technic designer Sariel has just addressed the well-known problem of open LEGO differentials, which are prone to slip situations (when one wheel has less traction than the other, it becomes the only driven wheel on the axle which can stop the whole vehicle) and which can be locked but this results in very wide suspension units which are unusable for most models.
As you can see in the video below, moving the differential up, however, it’s possible to keep the suspension’s width unchanged at the cost of added height.
The differential lock can be controlled manually using one small pneumatic cylinder per axle – multiple cylinders can be, of course, connected to a single pneumatic valve. In the video below Sariel is using hi compact pneumatic compressor/valve unit to control the lock.
The unit’s building instructions are also available under the link above. The suspension’s one flaw is the combination of the two 20t bevel gears which can skip when under sufficiently high stress. To reduce the risk of stressing, it’s best to use this suspension with the planetary wheel hubs, as shown in the instructions.
(please note that due to issues with 3D models of the new parts such as the 28t differential, some pieces aren’t shown in the instructions’ parts list).
Building instructions available here: sariel.pl/downloads/