Impeller mounting


#1

When purchasing the Impeller and motor - was a shaft required also?... if so, which one was used?


#2

The motor listed has a shaft of its own. I cut acrylic disks with the laser cutter that adapt the outer diameter of the motor shaft to the inner diameter of the hole on the propeller.


#3

Are these disks in the drawings already? Today I received the motors and impellers and definitely the shaft of the motor is much smaller than the inner diameter of the hole of the impeller. I also bought adapter shafts, but they are not long enough for securing the impeller to the motor.

Do you have a picture of your motor + impeller assembly?

That would help a lot

Thx

Simo


#4

Eric's got the dimensions in a notebook - this needs to be online, certainly.


Unfortunately, every laser cutter is a bit different. Depending on focus and the specific machine, the results can vary. Best bet might be to grab a micrometer and do a few runs of trial and error on the laser you're using.


#5

hobbyking has shaft adapters for the impellers listed... i think that is probably the best way to go? they were relatively in-expensive. The only potential issue would be with the vertical impeller's clearance?

i went without this time - and have been trying a number of off the shelf options in place without much luck....


#6

Can you post a link to the shaft adapters?


#7

http://www.hobbyking.com/hobbyking/store/%5F%5F10589%5F%5FImpeller%5FHub%5Ffor%5FEDF55%5F64%5F3mm%5FShaft%5F.html

I think that is the right one for the 64mm impeller


#8

This is exactly the one I bought. Apart from the fact that it’s just the shaft (so one should find the small hex screw to mount the adapter to the motor’s shaft) it’s not long enough and also not large enough.
I’ll take some pics and post them here to show what it looks like.
Simone


#9

Another thing to keep in mind, I think we should try and move away from this prop as soon as we can. We can definitely do better. What about a contest, x-prize style? Thoughts?

Also, Matt threw a prop file on thingiverse: http://www.thingiverse.com/thing:28223

Not sure if you access to a good 3D printer. Of course, this opens up a whole new series of potential issues...


#10

Well... the prop on thingiverse is just a 3D scan of that same impeller.

Probably we should have someone with hydrodynamics expertise design a propeller specifically for our specs:

  • low RPM
  • water
  • slow movement
  • but quick accelleration

Boat props are made to work at high RPM

Simo


#11

Agreed. Then we will probably have to injection mold them ourselves, because I don't think the personal 3D printers (makerbots, etc) can print high enough resolution.

I've talked to a few people about the design. OpenProp always comes up as a good resource: http://openprop.mit.edu/~openprop/wiki/index.php?title=Main_Page


#12

Yeah, personal 3D printers are not good enough. I agree.

Maybe Thingverse could work too...

But one thing at a time... let's the kits out first so that we have many people around experimenting, and then we can look at improving the design based on feedback and experimentation.


#13

Here is the blog post I just wrote with some pictures of impellers and motors and shaft:

http://dronesandrovs.wordpress.com/2012/08/09/motors-escs-and-impellers-some-problems-attaching-imp

I think the most important picture is this:


The shaft ends with a place for a screw, and with a specific shape that must probably be coupled with some specific cape.

Also, probably there must be a long screw to fix the cone to the shaft, otherwise it won't be impossible to attach it.

Any ideas?


#14

We never use the cone. In fact, it won't fit under the prop guard on the vertical thruster.

So, it looks like from this picture that the prop is ok, it's just the cone? Or is the prop not fixed properly, as well?


#15

Further depth in the responses' tree is not allowed, that's a good point for moving to a new forum :)

Back to impellers: the impeller is not shaped as the end of the shaft (as you can see in the image it has two flat areas, one per side) so it will slip unless fixed properly. I'll try with a normal screw and washer and see how it goes.

It would be great to see a close-up of the mounting available in the kit. I see you have some kind of black washer but cannot see in detail.



#16

Even though it would be great to have our own prop, keep in mind that this will add quite a hurdle to build your own ROV. It wasn’t as easy to find a cheap way to cut the acrylic here (Switzerland doesn’t seem to have so many open labs as the US).
It would be great if there was a way to build a ROV with parts you actually can get of the shelf.

Just my two cents.


#17

I talked to Eric about this. There isn't a good adapter, because we're basically using the props and motors in an unintended way.

We've been using the Delta-V15's lately (mentioned in the notes on the BOM) and will probably be including them in the kits, with small laser cut adapters.