Motor required for spin casting, 10-100rpm

[tiviny]

"..motor being bigger affect torque? " i don't follow.. torque will be in proportion to motor current.

I asked because you said this

How's the torque feel to you? Your machine is bigger that i thought, still those wiper motors are stout.

I wasnt sure what you were getting at here.

As regards attatching, the nylon gear spins too slow and doesn't have enough RPM range. The motor shaft spins at at a good speed with good range, but slowed down to where the good range is it vibrates more than I would like. It looks like I will end up attatching a pulley system using the nylon gear. That would give a good rpm range and isolate the vibrations somewhat.

sophiecentaur, I've tried a few sorts of levelling bases and basically my conclusion is I want to at least solidly try the hanging method. I assumed that getting something to spin would be a very simple thing, not so. The 3 issues are getting the spinning base to spin true relative to its shaft, getting the shaft true to vertical, and getting the container to spin accurately around its axis. Each one sounds relatively simple to fix, but each is really a whole problem of its own, and combined they make for a poor parabola.

Hanging will ideally (naively?) bypass the first 2 problems, however your concept of a very tough, nicely spinning base attatched to the axis of a container is sound, provided I had funds for such a machine. I've seen videos of purpose built ones and they indeed do look nice, but Ill post a photo tommorow of the best I've managed to come up with. 'Baseplate with diagonal slots' is a good idea.

I haven't properly considered how to attatch the container to the support to allow for adjustability, but I have ideas, mainly based on using screws.

The required accuracy is "very" accurate, haha. As best as possible. Its going to be used for visible and maybe IR wavelengths. Focal length/size isn't important, I am just going to use a container that's about the size I want, and spin it up until the liquid is just below the rim. I can get a potter to make a nice container. Ballpark is good enough, because as long as its a parabolic shape it has a focal point somewhere, and that is all i need.

 

[sophiecentaur]

Practical choices are personal in the end and the method anyone really fancies will be good in many ways.

I gather you are more interested in 'focussing energy' than forming a good image. The accuracy needed will depend largely on target size, I guess.

 

[jim hardy]

I asked because you said this

I see - the old disconnect - I'm mildly Aspergers and miss a lot .

I meant to convey that the rotating assembly you are building is larger than i thought it would be.

Actually your windshield wiper motor is somewhat shorter than the one in my Ford Ranger..
Still i think it'll make plenty of torque.

Sorry for the disconnect at my end , \sheepish grin icon\

old jim

 

[jim hardy]

"""The 3 issues are getting the spinning base to spin true relative to its shaft, getting the shaft true to vertical, and getting the container to spin accurately around its axis. Each one sounds relatively simple to fix, but each is really a whole problem of its own,"""

I think Sophie is saying at some deviation from vertical a hanging, rotating load could emulate a slingshot...

so experiment as you go.

keep us posted - this is interesting.