# "Tetherless" concept

**URL:** <https://discuss.bluerobotics.com/t/tetherless-concept/12123>\
**Category:** General Discussion\
**Created:** [May 13, 2022, 6:54pm UTC](https://discuss.bluerobotics.com/t/tetherless-concept/12123 "2022-05-13T18:54:56Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![EliotBR](https://sea1.discourse-cdn.com/flex019/user_avatar/discuss.bluerobotics.com/eliotbr/32/6937_2.png) [@EliotBR](https://discuss.bluerobotics.com/u/EliotBR)\
**Post date:** [May 15, 2022, 5:09am UTC](https://discuss.bluerobotics.com/t/tetherless-concept/12123/2 "2022-05-15T05:09:51Z")

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Hi @model14,

Sounds like an interesting project! 🙂

> [@model14](#):
>
> I set a limit of 60 feet for depth and attached a 70-foot tether from the crawler to a small (8” X 6”) foam float. On the float was an RC receiver and a video transmitter, plus a battery. On shore a video monitor and RC transmitter was used to control the crawler.

In case it’s of interest, there’s a similar system that was brought up recently [here](https://discuss.bluerobotics.com/t/arming-without-qgroundcontrol-ground-station/11692/5) 🙂

> [@model14](#):
>
> There was one problem, however, that I was unable to overcome. The lake bottom is so soft that the wheels almost immediately bogged down and game over. The wheels were 5” diameter RC crawler tires.
> 
> I decided to not pursue the project any further. A possible solution would be to use much larger diameter tires and add a vertical thrust motor to “unstick” the crawler.

I expect that spinning and rolling propulsion mechanisms are in general poorly suited to gradual vertical density changes in the medium being moved through:

- propellers pull up denser material from below which can make them slow down and/or get stuck while also reducing visibility
- small wheels have little to grip onto, and large wheels are heavy, bulky, and may have similar issues to propellers

Likely a more effective solution would be an undulating, gliding, and/or flapping mechanism (e.g. something like [this biomimetic robot](https://www.pliantenergy.com/robotics)). Unfortunately such mechanisms don’t tend to be readily available, or have readily available control algorithms, so making one would likely need a fair amount of custom development of both hardware and software (although it’d also be really cool…).

> [@model14](#):
>
> It’s good to be back on the BR forum again.

Glad to hear it, and good to have you back 🙂

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