Which of these structures is stronger? 1

[edison123]

Which of these structures is stronger in terms of resisting the bending?

Muthu

http://www.edison.co.in

 

[dik]

Is that delamination? It appears to be two 'sheets' of copper.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[rb1957]

this thing spins, right? so a significant load is radial (axial to the "beam") and a transverse load when start/stop. Only a very small load (weight) in the direction posted ?

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[edison123]

This is the OEM manufacture and it has two copper plates brazed together, intermittently and it spins at 1000 RPM. The delamination happened after the cracks and then the flashover.

There is no force acting on these parts as shown when it rotates?

Muthu

http://www.edison.co.in

 

[dik]

I'm not familiar with the mechanism... why does it have the 'arch' shape in the middle? If it is spinning the shape would only increase the stresses having that deformity. If the deformation part of the commutator design?

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[3DDave]

The arch is likely to provide thermal expansion compliance.

 

[edison123]

The arch is for thermal expansion as well as for stiffness since the radial length is about 150 mm while the thickness is only 2x1.5 mm.

Muthu

http://www.edison.co.in

 

[dik]

Thanks... it's much larger than I thought... I was thinking it was about 1/2" long...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[rb1957]

"There is no force acting on these parts as shown when it rotates?" ... what? not omega^2*R ??

these elements are laminated sheets ? what caused the delam ? how laminated ??

How old is this machine ? how does this service life compare with others ??

Is that an unusual amount of paint on the elements ??

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[edison123]

The two 1.5 mm thick copper are brazed together intermittently about 3/4 inch apart. There are two motors that have this problem in service and cracks started about two years into service. Motor vibrations are well within the limit.

My thought - if the arches bend towards the direction of the rotation (as against the present against the rotation direction), would it help?

Muthu

http://www.edison.co.in

 

[Compositepro]

The varnish filling the space between the wire arches not only blocks cooling air, but will also lead to the varnish cracking. The arches are there to allow movement of the wire when it expands and contracts with temperature.

 

[rb1957]

ok, 2 out of a population of ?

after 2 years ... that doesn't sound good.

can you look at other "beams" ?

the proposal is that the delam started first ... ok, what could have caused the delam ?
environmental ?operational ? (you say you're within vibration spec, but are starting/stopping the device quickly or often ?

I don't think the shape (bowed one way or the other) will make a difference.

Is this feature (the bowed strips) common to commutator design or unique here ? Are they typically laminated ?
I don't see much evidence of "brazed together intermittently about 3/4 inch apart" in the pix. Maybe I wouldn't (after the flash fire) ?

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[edison123]

2 out of 2. Such arches are common in commutators with long and thin risers. And mostly, they are laminated.

As I said, the delam happened after the cracks developed.

Muthu

http://www.edison.co.in

 

[dik]

I'd be more curious to find out why it was delaminating? and whether there is a reason to use two 'bonded?' strips.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[edison123]

They are made of two strips to connect to the winding at the top. Issue here is cracks not delamination.

Muthu

http://www.edison.co.in

 

[dik]

Thanks... still curious about delamination and if this can have an effect.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik