Rotating electrical contact - solution?

[beatbox]

Hi all,
Sorry if this may be more of an engineering question, but maybe
someone here has some experience of this.
I am making a toy for my son. There is a small motor which drives a
propeller, which makes part of the toy spin. The motor is mounted on
this spinning part. The power source cannot be mounted on this part.
So I need to make an electrical contact between a spinning part and a
static part. I am not sure how to do this reliably, and with the
minimum of friction.
Any ideas?
Thanks

 

[steamer]

--Head over to carlpisaturo.com for a really excellent photo essay of
how to do this.

 

[John Fields]

Hi all,
Sorry if this may be more of an engineering question, but maybe
someone here has some experience of this.
I am making a toy for my son. There is a small motor which drives a
propeller, which makes part of the toy spin. The motor is mounted on
this spinning part. The power source cannot be mounted on this part.
So I need to make an electrical contact between a spinning part and a
static part. I am not sure how to do this reliably, and with the
minimum of friction.
Any ideas?

---
I take it, then, that the shaft of the motor is affixed to the rest
of the device while the body of the motor and the propeller are free
to spin.

If that's the case, then you could use slip rings to transfer
electrical power to the motor.

If you could post some photos to a web page somewhere or to
alt.binaries.schematics.electronic of what the device looks like
then we might be able to come up with a physically realizable
solution for you.

 

[ehsjr]

--Head over to carlpisaturo.com for a really excellent photo essay of
how to do this.

And click on Serprntine ARm, then commutator?

This link?
http://www.carlpisaturo.com/SRP/Commutator.html

Ed

 

[default]

Hi all,
Sorry if this may be more of an engineering question, but maybe
someone here has some experience of this.
I am making a toy for my son. There is a small motor which drives a
propeller, which makes part of the toy spin. The motor is mounted on
this spinning part. The power source cannot be mounted on this part.
So I need to make an electrical contact between a spinning part and a
static part. I am not sure how to do this reliably, and with the
minimum of friction.
Any ideas?
Thanks

Build a slip ring or pair of them.

I made this kinetic wire sculpture that needed something like that.
Small airplane with navigation lights and prop . . . the plane was
supported with a #12 steel wire - I cut the terminations off of a 1/4"
stereo phone jack and slid the works down over the steel wire
(scrapping the "tip" and keeping the barrels and insulators). Put a
couple of phosphor bronze wipers to make connections on the stationary
part.

Real high current slip rings are a little harder. Cut rings from
rigid copper tube or use straight couplings and slide them down over
CPVC pipe - takes some effort but chucking the pipe in a drill press
and using sandpaper to turn it down a little. Hardware stores carry
DC motor brushes, hobby shops have rectangular brass tubing for
building up brush holders.

 

[beatbox]

Build a slip ring or pair of them.

I made this kinetic wire sculpture that needed something like that.
Small airplane with navigation lights and prop . . . the plane was
supported with a #12 steel wire - I cut the terminations off of a 1/4"
stereo phone jack and slid the works down over the steel wire
(scrapping the "tip" and keeping the barrels and insulators). Put a
couple of phosphor bronze wipers to make connections on the stationary
part.

Real high current slip rings are a little harder. Cut rings from
rigid copper tube or use straight couplings and slide them down over
CPVC pipe - takes some effort but chucking the pipe in a drill press
and using sandpaper to turn it down a little. Hardware stores carry
DC motor brushes, hobby shops have rectangular brass tubing for
building up brush holders.

Thanks all.
Something like that should do the trick. Nice idea to use a stereo
jack. I'm just a bit worried about the friction slowing the movement,
as it will be quite a delicate thing without a great deal of
propulsive energy. I'll do some experiments and see what works.

 

[Nobody]

Sorry if this may be more of an engineering question, but maybe
someone here has some experience of this.
I am making a toy for my son. There is a small motor which drives a
propeller, which makes part of the toy spin. The motor is mounted on
this spinning part. The power source cannot be mounted on this part.
So I need to make an electrical contact between a spinning part and a
static part. I am not sure how to do this reliably, and with the
minimum of friction.

As others have noted, slip rings are the usual way to do this.

An alternative is inductive coupling (i.e. a coil of wire on each part).
This is significantly more complex (you have to convert the power to AC
then back to DC), but has the advantage that you don't get wear or arcing
on the brushes.

 

[beatbox]

As others have noted, slip rings are the usual way to do this.

An alternative is inductive coupling (i.e. a coil of wire on each part).
This is significantly more complex (you have to convert the power to AC
then back to DC), but has the advantage that you don't get wear or arcing
on the brushes.

Thanks, I'll look into that.

 

[John Fields]

Thanks, I'll look into that.

 

[HapticZ]

if this is some relatively toyish thing, just use the shaft as a
spindle/conductor

wrap some cello tape on it to give a single electrical insul layer

then use aluminum duct tape to create another layer of electrically
conductive path, just enough to wrap maybe twice around.
the adhesive should hold if the shaft is degreased well

connect your wires at the motor end to the shaft and the aluminum somehow

use some kind of springy type brass strip to rub against the shaft for
ground?

and another to rub against the aluminum for the other positive volts.

this arrangement is not meant to last forever, as the aluminum will wear out
, but it should work for a while

improvements include using adhesive copper foil in place of aluminum

i have assumed the propellor spin rate is fairly slow, less than 200 rpm, if
you start going really fast, >>200 rpm you will get unbalance problems, then
u must find soembody with a precision lathe to machine special parts to
perfection.

 

[steamer]

http://www.carlpisaturo.com/SRP/Commutator.html

--Yup that's the one!

 

[Jon Slaughter]

Hi all,
Sorry if this may be more of an engineering question, but maybe
someone here has some experience of this.
I am making a toy for my son. There is a small motor which drives a
propeller, which makes part of the toy spin. The motor is mounted on
this spinning part. The power source cannot be mounted on this part.
So I need to make an electrical contact between a spinning part and a
static part. I am not sure how to do this reliably, and with the
minimum of friction.
Any ideas?
Thanks

A more exotic solution is to use a conductive liquid such as mercury

 

[Jamie]

A more exotic solution is to use a conductive liquid such as mercury

I hear tell china has a good deal on over stocked lead that is nicely
applied via paint!

 

[default]

too true, and now they seem to not understand why children eat small beads!

i smell a bad bad drift in all these recalls of toys.

china culture been around for what 4000 years? perhaps they have
eliminated potential rivals using slow, sublime , innocuous means over the
milleniums!??

or better yet, they just dont give a damn!

Their culture doesn't encourage individual ego or thought.

Probably don't give a damn. I saw a blog that referred to an "egg
making" mold. The idea being that you take gypsum, sodium hydroxide
(to adjust pH only) and some other, largely inedible, ingredients and
mold an egg with one mold for the yolk and another for the whites and
shell. I didn't believe it until I visited the site selling the molds
and how to use them.

Apparently it is cheaper to "make" eggs from industrial byproducts and
waste than chickens.

It isn't what we know about that is scary it is what they may use in
foods that we don't know about . . .

Selling glycol as glycerine to be used in cough syrup, melamine added
to starches to improve the protein test score, etc..
--

 

[default]

or better yet, they just dont give a damn!

Couldn't find the original site but did turn up this for artificial
eggs.

http://en.epochtimes.com/news/7-9-11/59598.html

One-Tenth the Cost

According to the report from The Chosun Ilbo, due to the sharp
increase in food prices in China, artificial eggs, made only from
chemicals with no natural ingredients have appeared in Zhengzhou City,
Henan Province.

Mr. Wang, who runs a company that makes food additives, described how
artificial eggs were made. "The 'egg white' is made by dissolving
sodium alginate in water. It appears to be a transparent viscous
liquid and it's hard to distinguish it from real egg white.
--

 

[HapticZ]

too true, and now they seem to not understand why children eat small beads!

i smell a bad bad drift in all these recalls of toys.

china culture been around for what 4000 years? perhaps they have
eliminated potential rivals using slow, sublime , innocuous means over the
milleniums!??

or better yet, they just dont give a damn!

 

[HapticZ]

apparently price driven market is priority to them.

with such a viable DNA stock to draw from, they fear no invaders

what is the 'break even' cost over long term?

perhaps the 'ego' of the culture itself is the very thing that will force
self limitation,

& at expense of human blood, which seems to be held as relatively with out
value!

ah, so be it, time will tell