Grate, Rake, and Kevlar Hinge Doors in RASSOR Drum for Improved Efficiency and Performance

Last crawled date: 1 year, 10 months ago

NOTES:
- The gif. after the presentation has no thumbnail but it is working, please click on it first to see.
- The doors on the model is simply for illustration purpose, it cannot be simulated because it is fixed in place
- '80%' on the presentation should be '70-80%'

Design Summary:
The design purpose is to met the design requirement from the competition description and the paper that is included on the description. The design goals are as follows:
- Meet the dimension requirement
- Manufacture-able and functional
- Last for at least 5 years
- Prevent icy regolith (equivalent as damped sand on earth) to stuck on the scoop
- Successfully exclude rocks of certain size from entering the bucket
- Maximum weight of 5kg

Based on that, I've created this design. The design is able to:
- prevent rock larger than 1cm in diameter to enter,
- eliminate cohesion of icy regolith prior to entering the scoop,
- able to retain whats inside the bucket when on a trip back to the lander for about 8.5 minutes
- all parts that is expected to wear out will be replaceable
- manufacturing is possible, as explained on the pictures
- assembly is possible, as can be seen on the gif.
- structural integrity

Weight of the bucket in total is about 4.5kg. Dimension of the drum has already fulfilled the dimension requirement, with max. diameter of 450mm with scoop, 340mm without scoop, with length of 360mm, and maximum engaged scoop at any given time 175mm. It will be able to AT LEAST collect 22L of regolith in one mining cycle, with AT LEAST 80% full.

To make it reach at least 80% full I use doors to prevent regolith from falling out, the doors only located in 1 or 2 scoop in each segment. To keep the mining cycle fast, the other scoop that has no doors will have larger outlet, so it catches more regolith as it rotates backward, thus creating faster unloading on that scoop. Will the mining cycle be faster? I don't know, but using this system will allow it to be more effective, as regolith lost is minimal, with still three scoops on each segment, keeping the time of mining fast. It uses marker so the operator can control the position of the bucket for maximum regolith volume retained.

The scoop that has no doors will not be functioning as good as the one with doors when RASSOR is mining. The reason is that when its reaches about 30-40% full, regolith will start to fall into the scoop cavity, so the regolith will not be that much since the way is blocked by the falling regolith from the inside. Thus, to add more regolith when its already 40% full, the scoop with doors will have a more crutial role, as the scoop cavity will not be filled with regolith from the inside, keeping digging capacity for that scoop just like normal, until its about 70-80% full after mining about 10 minutes, beyond that the openings of the door will be limited by the regolith surface, making it less effective.

As an additional information (because its not mentioned on the presentation uploaded):
- the scoop can cut 5cm deep, but cutting it 5cm in one scoop will jam the scoop, as mentioned by Jason Schuler on the competition comments. The design scoop is at least 5cm, therefore able to do the task just like prior design, cutting it only half full about 2.5cm.
- If the grating system got clogged, the main corrective action is to redesign the grate. Maybe enlarge the holes to 2-3cm, or make the holes longer, about 83.5cm while keeping the width 1cm. Also, the vibrating mechanism mentioned on the research article might help.
- Will the centrifugal force hold the door closed? No it won't, centrifugal force at 20RPM is really low compared to weight force of the regolith and the door itself
- To increase the volume, the drum circle line should've been tangent to the scoop curve
- Will the doors got stucked by regolith? No it won't, see my discussion with Sava Savov on the comment section
- After thinking of it for a while, the doors might also have the ability to unload. When its about 60-80% full, the doors won't be fully closed when it rotates backward and reach the surface of the regolith inside, thus some of the regolith will get through the door and will be able to unload through the scoop with doors. But thats not the case when its almost empty, in this case the scoop without doors will unload the regolith

File including:
- STEP and STL file is compiled into one rar.
- STL also available to download in single part
- Renderings
- Explanation pictures
- Animated gif.
- The gif animation in mp4 format

Reference:
- Mueller, R.P., Cox, R.E., Ebert, T., Smith, J.D., Schuler, J.M. & Nick, A.J. 2013. Regolith Advanced Surface Systems Operations Robot (RASSOR). IEEE Aerospace Conference Proceedings. 2013

- Wilkinson, A. & DeGennaro, A. 2006. Digging and pushing lunar regolith: Classical soil mechanics and the forces needed for excavation and traction. Journal of Terramechanics 44 (2007) 133-152

Illustration:
The videos listed below is just to illustrate the reason why I choose the design, all of the videos are not my creation.

- https://www.youtube.com/watch?v=cgI5EzcpK6s&t=456s
- https://www.youtube.com/watch?v=Q675gKNp6zs&t=22s
- https://www.youtube.com/watch?v=C-b-7BYygFs