Hi there, I’m a member of team 1477 and have been working on a configurable round tube elevator design over the past month. The design is inspired by the 148 2018 round tube elevator. I would appreciate any feedback/questions on the design.
Design Goals:
- Continuous Rigging
- Capstan Gearbox
- Constructed from (mostly) plate and tube
- Configurable amount of stages (1+)
- Lightweight
Quick Facts:
- Compressed Height: 37 in.
- Extended Height: 84 in.
- Total weight: 13.55 Lbs
Design
Stages:
The stages of the elevator consist of a “stage cap” and “stage plug” which contain all the pulleys, rollers, and structural components of each stage (pictured below). The stage cap and stage plug are joined together using two 1.5 OD 1/32 wall tubes.
Stage cap:
A stage cap consists of two bearing block assemblies, a 1.5 OD 1/32 wall tube, and two 3/8 Aluminum Gussets connecting the bearing block assemblies and cross tube together.
Cross section of a bearing block assembly:
Each bearing block assembly contains two 1x1 WCP tube plugs in a 3dp sleeve and a billet block underneath. The components are tied together using two .09 Al gussets, which also hold the roller bearing.
Stage Plug:
Each stage plug contains the same bearing block assembly as the stage cap (but upsidedown), and uses 1.5 x1.5 tube for the main structure. The stage plugs also have tiny “wings” that contact hardstops on the upright round tubes to maintain proper overlap between stages.
Roller Bearing
The hardest part of this elevator was designing the roller bearings. The intent for this roller bearing design was to capture as much of the tube as possible while still keeping the gap between the stages low. Currently this design captures approx 35% of the tube face and allows for a .25 in. gap between stages.
The main roller bearing body is 3d printed, and has a .25 OD .201 ID shaft pressed into to strengthen the part. The roller bearing also has a .5 OD .188 ID bearing to support the radial load and a needle roller bearing to support axial loads.
Although this design is meant to be 3d printed, we have a 4th axis on our OMIO X8 and will most likely machine it out of delrin if possible.
Rigging:
Elevator has continuous rigging, with the ropes hidden behind the 1.5 round tube uprights. The rope starts at the top of the carriage, runs through the pulleys & the capstan gearbox, and terminates at the bottom of the carriage. A 1/2 hex shaft connected to a ratchet wrench on the top of the carriage tensions the rope to remove any slack.
Capstan Gearbox:
The capstan gearbox is different from a conventional elevator spool system in that it uses the friction between the rope & capstan (black thing with ridges) to cause the rope to move along, rather than spooling and unspooling the rope.
Benefits of the capstan gearbox are:
- Capstan diameter can be much smaller than a standard elevator rope spool
- No spooling string means no dealing with issues regarding variable fleet angles and rope spooling on top of itself
- Smaller diameter capstans allow for a lower gear reduction, saving weight
The capstan gearbox in this pic is integrated into the 2x1 base tube, which allows it to neatly tuck underneath the elevator. Currently there is 1 Neo geared 3:1 to power the system, but the gearbox can accept up to 2 motors and any of the COTS planetary gearboxes.
