Can I use a double helical pinion with a herringbone gear?

[jarimasen]

At one of the plants they are asking me the following:

They have a NEW double helical pinion (it has a gap in the middle) and they have a USED herringbone gear.. You can see where this is going...

They are supposed to be same pitch, et cetera... However, I have not seen before a double helical pinion with a herringbone gear. I am no expert in gears, and so I could not think of a reason why it can't be. So, is this possible? Are there justified reason against this mixed match??

Photo of pinion is not actual pinion, but very similar

https://files.engineering.com/getfi...90-4cb6-b00c-17970bdbc797&file=1356272843.jpg

Photo of gear is the real gear

https://files.engineering.com/getfi...e1fb-42d6-b422-b2e422eb2c31&file=IMG_7394.JPG

Regards,
JM
thread406-77165

JM

 

[tbuelna]

A herringbone gear is a type of double helical gear. So if what you say is correct about the pinion & gear geometries (DP/module, pressure angle, helix angle, profile mods, etc) being compatible, then they should work together. The only thing to watch for is that the inner edges of the double helical pinion teeth (ie. at the center gap) are never allowed to contact the radiused center section of the herringbone tooth flanks, as shown in your photo. Double helical gear pairs will self-align in the axial direction, so at least one gear of the pair must have sufficient axial float to allow this to happen. Take this into account when checking for interference between inner edges of the double helical teeth and herringbone tooth flank apex fillets.

 

[jarimasen]

I have been thinking about what you mention here. About the self alignment of the pinion. This type of transmission usually has a fixed bearing and a loose bearing (see drawing). The fixed bearing is the one between the pinion and the motor. If this is fixed and does not let the pinion shaft move, then it will cause a misalignment.

https://files.engineering.com/getfi...65-4581-4e4e-a155-7bd6e7fe3736&file=drive.jpg

Furthermore, this type of motors tend to align with their magnetic center (some is absorbed by the pneumatic coupling), but this also causes an axial movement.

My question is, should the fixed side be on the other side of the shaft? or better yet, why have a fixed side at all if the pinion is the one that holds the pinion shaft from moving axially

Regards





JM

 

[tbuelna]

Only one member (pinion or gear) should be constrained axially with your example. Whether the axial constraint is provided by the pinion or gear shaft bearings will depend on factors like available space, mechanical efficiency, cost, etc. The primary consideration will always be to ensure the system is not over-constrained.

Regarding your sketch, the blue pinion is shown as a herringbone, and the green gear is shown as a double helical. The relative angles (left hand/right hand) of the teeth are also not shown correctly. The left hand helical pinion teeth should mesh with right hand helical gear teeth. Not clear how the gear bearings are arranged.

 

[lukin1977]

can you tell us what will be the use of the gears?

 

[jarimasen]

@tbuelna

You are right about the sketch, I guess it did not help to clear things... I hope this can clarify better

https://files.engineering.com/getfi...4d35-4dd9-bf00-6855cbe282e3&file=Picture1.jpg

@lukin1977
The gears are used for an open transmission of tubemill

We checked and the mill has an axial displacement of 44mils. Is not clear where is the movement coming from. Feed in one direction and transmission on the other?

Regards,

JM