Homebuilt ROVs Forum

First actuator prototype built and tested.

It's really crude and wonky at the time, but the concept works and with a bit more tuning and small redesign I think it will be quite usable.

In this first prototype I am using a M4 stainless steel threaded rod. I think I might want to move up to M6 rod as the M4 is a bit small for this sort of stuff.
The clutch system works, but needs some tuning. I made it so that the arms in the clutch (yellow in picture below) can be printed separately, so adjusting flex, length and spares can easily be done. The arms broke during testing today, actually that's what happened in the end of the youtube clip below. I planned to do the acetone treatment to the arms to make them more flexible and less brittle. Will try that next.
The blue piece is attached to the threaded rod. The biggest gear only rides loosely on the threaded rod and is engaged to the gear on the motor. As this gear rotates, the flexible clutch arms hit the rigid arms on the central (blue) part and in turn starts to rotate the threaded rod and moving the piston. If the force on the piston is too great, the clutch arms should flex and start slipping.
My hope is that his will eliminate all need for end stops and protection circuits, making it a much more crude but simpler mechanism.
As shown in the video, it lifts 15kg (33lbs) easily. I was actually surprised by this. The motor and ESC seems to handle this load easily and power consumption was very low. But I suspect the readings wasn't too accurate. so more on that later.

The clutch design is brilliant... Man I love the ideas you guys come up with.

I been trying to come up with a way to get around end stops too in a manipulator I thought about trying to make a break away magnetic coupler like in the thruster I am working on but now I might have to rethink that. I can't believe how strong that is too you would be able to have a pair of cutting arms with strength like that. I can't want to see how this turns out.

-Steve

Simple Brilliance!

Ole,

Very nice work! I like your attention to detail. You are a master of the 'gedanken experiment'.

Can't wait to see more...

Thanks! Hoping this will work in the end

I have already considered adding some sort of cutting ability to my arm, but always thought that it would require more force then what was possible to achieve on a small, home built ROV.
But now I think it would be quite possible to do. If we say that an actuator like this can pull 15kgs (33lbs) MAX, though I think it can do quite a bit more. To enhance that even further, we could connect it to a pulley system that closes the cutter, have the rope/wire do 4 loops over the pulleys and you have 60kgs (132lbs) of force. A simple spring return can be used to open the cutter again but you might get jamming problems. At this point you are staring to look at some serious force on the system though and everything around it needs to cope!
Just thinking out lound

olegodo wrote:Thanks! Hoping this will work in the end

I have already considered adding some sort of cutting ability to my arm, but always thought that it would require more force then what was possible to achieve on a small, home built ROV.
But now I think it would be quite possible to do. If we say that an actuator like this can pull 15kgs (33lbs) MAX, though I think it can do quite a bit more. To enhance that even further, we could connect it to a pulley system that closes the cutter, have the rope/wire do 4 loops over the pulleys and you have 60kgs (132lbs) of force. A simple spring return can be used to open the cutter again but you might get jamming problems. At this point you are staring to look at some serious force on the system though and everything around it needs to cope!
Just thinking out lound

Man 132lb force from a small motor on a homebuilt rov! That's simply amazing just to think. But is that much force necessary for cutting?

Absolutely no idea at all
But I guess we will find out pretty soon.

Doing a total redesign of the clutch this weekend.

olegodo wrote:Absolutely no idea at all
But I guess we will find out pretty soon.

Doing a total redesign of the clutch this weekend.

Too excited to see it. Have you done the electronics btw?

Electronics for the actuator or the Rov itself?
As of now, my plan is to use Moki's raspberry pi software and electronics setup.

Great idea

Hopefully i can help you install it. Will try to find time, to fix the problems you have encounted during your first install.