Interesting Link to home built thrusters


#1

This link has some interesting info and looks like they have tried various props.

http://www.homebuiltrovs.com/mayfair750test.html


#2

David,

This is indeed a very interesting link I didn't know already. Like the guys at OpenROV HQ, they found that the Graupner 3-bladed props which are shipped now with the kits have the best thrust/amp draw ratio.

I recently replaced the old Delta-V15 impeller props of my OpenROV 2.3 with the graupners and I'm happy with them. However, they produce much less thrust in reverse direction (this is what the test also found out).

I did not replace the vertical thruster yet, but due to the fact that the Graupner Prop would produce less thrust for ascending, I'm thinking of using something like the Robbe 1471/72 here instead. Unfortunately, this type is only available with a maximum diamater of 50mm.

Has anyone other suggestions for the vertical prop?

-Stefan


#3

Thanks lot for the link David.

Very usefull and interesting.

Regards


#4

I am also using the Graupner props and yes the reverse thrust seems to be an issue. This summer on one of my dives I drove the rov into a soft bottom on the lake and I did not have enough reverse thrust to pull myself out so I had to pull on the tether to get it unstuck. Also on the assent from 60' takes some time because of this issue. I am using two vertical thrusters and was thinking of reversing one so that one prop had more thrust to get me back to the surface. I am not sure if this will make the ROV spin a bit on descents or accents. right now with two I do not get any spin because I have both a right and left rotating prop on the Vertical thrusters and that works great.


#5

For the spin problem would be nice to know the Prop torque when running left and right.

Albeit there are no data curves for those propellers, it can be approximately deduced from the motor behaviour by reading its load (current).

Maybe torque does not change as much as thrust does.

I posted on this forum the calculation procedure in an older post.

Anyway:

With known Kv and no load current Io.

Torque constant: Kq= 30/(pi Kv)

Torque: Q= Kq(I - Io)

Regards


#6

Hi All,

I am new to OpenROV, but not to the world of DIY as I have built a number of competition autonomous rovers (UGVs) and thought that it was time to investigate ROVs as where I live in FL has many ponds, lakes, and canals.

The homebuiltrovs website was one of the first ones that I found besides this website. I have decided to use the Mayfair 750 plug-in bilge pump along with a Robbe 50mm three blade prop to build my ROV thrusters.

The biggest problem I have is coupling the bilge pump motor shaft to the Robbe prop. The motor shaft is ~1/8" (3.175 mm) and the Robbe has a 4 mm threaded brass insert. I was able to find a couple of GW 3 mm shaft to 4 mm threaded shaft adapters and I plan to ream the 3 mm shaft hole to 3.175 mm and cut the 4mm threaded shaft down to fit the Robbe threaded insert. However that only takes care of the right and left thrusters and I will need a third adapter for the vertical thruster.

Steve Thone, the owner of the homebuiltrovs, machined his own couplers (adapters) and has provided a drawing of the adapters dimensions. However this would require the use of a small lathe, which I know how to use, but do not have in my shop at the moment. Therefore does anyone know of a source of adapters for the Robbe propellers?

Regards,

TCIII