Gear Train Alignment

[gdechaine]

What is the proper way to align a gear train to keep backlash to a minimum and extend the life of the gears? There are two gears in the assembly, one set about a foot higher than the other. Both gears contain the same overall specs including pitch diameter, pressure angle, etc... Maximum backlash < .045

 

[BobM3]

Adjust the center distance.

 

[gdechaine]

I wasn't sure if there was a tool or gage that could be used for setting these distances besides a tape measure etc.. I guess I should have phrased the question differently. Thanks.

 

[BobM3]

Feeler gages can be used to measure the backlash. Also a dial indicator can be used to measure the backlash. There are forumulas that can be used that would tell you the amount of center distance changed needed to change the gap a certain amount. It's been awhile but I could probably find them. Is that what you were looking for?

 

[gdechaine]

I think the feeler gage you mentioned in combination with some of the gap formulas will probably be the best option. I tried searching for some of those equations but couldn't find anything that would really help so I gave up on the search a while back. If it's not to much trouble I would really appreciate if you could locate some of the equations as long as it's not to much trouble. If its easier just put a link up if it's on the internet.

 

[dinjin]

Many folks mark the gear at the max runout or point of
min backlash. The same maybe true of the pinion. Set the
feeler gage into the space and force the centers together.
Often a suggested min backlash is specified and that would
be the thickness of the feeler gage.

 

[BobM3]

Take a look at this:

http://www.sdp-si.com/D190/HTML/D190T47.htm

 

[gdechaine]

Thanks for the info. Definitely helped.

 

[tbuelna]

Some backlash is usually necessary for the proper operation of most gearsets. It is not desirable to have a condition where the tooth of one gear is forced hard into the space of the mating gear, and backlash prevents this. Also, modifying the pitch centers away from the gearset's designed condition may cause scoring problems. Unless the gearset application is backlash sensitive, like for timing, backlash is not a problem.

With parallel axis gears, backlash is usually designed into the gear profile, since it is not usually practical to adjust the pitch centers at assembly. Backlash is usually measured with a dial indicator, and should be taken at several points around the mesh to account for tooth-to-tooth errors.

With non-parallel axis gears, backlash (as well as contact pattern) can be adjusted somewhat by shimming.

Good Luck.

 

[agdyp]

Please see this link:

http://www.wmberg.com/catalog/pdf/b00k2-16.pdf

Look at page K12, table E.
-agdyp

 

[Tmoose]

a contact pattern free of edge loading is real important for good surface durability, which is what limits the life of many gear designs.

 

[sreid]

We use to use paper/carbon paper to check gap and to check for mesh alignment.

 

[mfgenggear]

The back lash will depend upon the fit, form function of the gear train, Dudleys Gear Handbook has recommended Backlash allowance for power gearing , Page 5-37 , Table 5-11.

the Min & Max center distance according to Dudley is the following.

the stackup of center distance mounting bores, the thickness of the teeth, The pitch diameter runout.

from my experience the the machine tolerances of the housing mounting bores,the mounting shafts, and the precision of the gears will affect alignment.

in other words the application will dictate the precision required to maintain the all of the above requirements.
and it must be designed and machined up front, and must be inspected accordinly. so it's more than just backlash,
it the overall attributes of the gears train.

not a so simple answer:/