# "Tetherless" concept **URL:** \ **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:** 5\ **Page:** 1
**Author:** ![model14](https://avatars.discourse-cdn.com/v4/letter/m/eb9ed0/32.png) [@model14](https://discuss.bluerobotics.com/u/model14)\ **Post date:** [May 13, 2022, 6:54pm UTC](https://discuss.bluerobotics.com/t/tetherless-concept/12123/1 "2022-05-13T18:54:57Z")
Last year I built a negatively buoyant ROV crawler, with the idea of “crawling” along the lake bottom for exploration, rather than using a 3D submersible. An early design concept was to eliminate the crawler being tethered to the shore, with the inherent issue of entanglement in bankside and bottom weeds, and rocks. 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. I was most concerned that the RC PWM signals from the receiver to the Arduino in the crawler would be attenuated too much to be reliable. I was wrong on that account. Signal strength at the Arduino pins was good enough to be reliable. 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. As I posted yesterday, I am currently building a 3D ROV for lake exploration. Initially I will use a tether to the shoreline, but eventually I want to try the float tether concept as an option to eliminate long tethers to the shoreline. A thought some of you might want to think about this as a future project. It’s good to be back on the BR forum again. Richard ---
**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")
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 🙂 ---
**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 17, 2022, 7:50am UTC](https://discuss.bluerobotics.com/t/tetherless-concept/12123/3 "2022-05-17T07:50:26Z")
Split this topic on May 17, 2022, 7:50am UTC A post was merged into an existing topic: [Can we use the O-Ring Flange with standard PVC pipe?](https://discuss.bluerobotics.com/t/can-we-use-the-o-ring-flange-with-standard-pvc-pipe/5613/4) ---
**Author:** ![Bjarte](https://avatars.discourse-cdn.com/v4/letter/b/ea5d25/32.png) [@Bjarte](https://discuss.bluerobotics.com/u/Bjarte)\ **Post date:** [May 18, 2022, 10:47am UTC](https://discuss.bluerobotics.com/t/tetherless-concept/12123/4 "2022-05-18T10:47:23Z")
![image](https://us1.discourse-cdn.com/flex019/uploads/bluerobotics/original/2X/f/fb6cc6b2a8e26e56311a65149c01d13e78563701.jpeg) This was a student project in 2019 with a consept for soft seabed. ---
**Author:** ![model14](https://avatars.discourse-cdn.com/v4/letter/m/eb9ed0/32.png) [@model14](https://discuss.bluerobotics.com/u/model14)\ **Post date:** [May 18, 2022, 8:24pm UTC](https://discuss.bluerobotics.com/t/tetherless-concept/12123/5 "2022-05-18T20:24:25Z")
Very interesting propulsion. I could see that working in the mud and silt.