Gearbox Mesh Question
 

Just a quick question from those of you out there that made your own gearboxes.

What have you found to be the best tooth clearance adder to the diametrical pitches of the spur gears to get a nice mesh. We have been using 5 thou total adder and it was really tight at Philly even after lapping in the gears, finally it is starting to get loose after Detroit. I would like more of that worn in feeling before the first regional.

Thanks in advance.

Re: Gearbox Mesh Question
 

Perhaps the .005 was giving you too much spacing and the tooth face was not contacting the correct point in the tooth valley? What pitch and PA gears are you using. We use 20P 20*PA. Last year, we set them at the exact C-C distance and we had a couple tight spots. This year, we added .002 to that distance and it runs smooth as silk. We did however receive one gear from Martin that was 20P 1/2" face but 14.5*PA They don't even make those! It must have been a mishap in the manufacturing line. It ran but it was really super tight. We replaced it with another correctly made gear and again, smooth as silk.

I would look for other reasons your gearbox is tight other than the C-C distance. Is it tight in just one spot? Try to "time" the tightness to a specific gear. Also, get a really good magnifying glass and look at the interface between tooth and valley to make sure it all looks okay. This is how we found that our defect gear had a different PA.

EDIT: Last year with the exact spacing we dry ran it in to free it up. This year, there really was no run in required or performed.

Re: Gearbox Mesh Question
 

Years ago, I did not use any added distance to the center-to-center distance. During the past 2 years, I have used 0.002" or 0.003".

With AndyMark AM Shifters, we are using 0.002", I believe. These are all run dry to be worn in, then greased at the application. With the AM Planetaries, we are using much more, at about 0.012" from the sun gear to the ring gear.

Andy B.

Re: Gearbox Mesh Question
 

Is there a handy-dandy "understanding gears" reference available, either in a library or online? I am perfectly happy calculating gear ratios and such (several years as a cyclist did that), but otherwise you might as well be speaking Cantonese. Unless you *are* a Cantonese speaker, then it sounds Norwegian.

Thanks.

Re: Gearbox Mesh Question
 

I use nominal for C-C distance on my gearboxes. This distance is only as good as the machine and operator that makes the plates. We also run dry for break-in under no load condition and then lube before loading.

Team 716 white papers for the dual speed has a section on determining C-C distance and selecting gear ratios for clearance of non-meshing gears.

Re: Gearbox Mesh Question
 

I also design with a .002" added for backlash. We also run our GB's dry for a good 15 minutes before applying lithium greese. I have discussed the same thing with a lot of other people, and .002" seems to be the happy spot for gear meshing. To date we havnt had any problems with excessive wearing or excessive friction in our gearboxes.

Re: Gearbox Mesh Question
 

Stock Drive Products used to include a copy of their "Handbook of Gears" as a standard part of their catalog. Unfortunately, they stopped this practice a few years ago. However, they still have a version online at http://www.sdp-si.com/D190/D190cat.htm. The information in the Handbook is very useful, and a great introduction to gear train design.

-dave

Re: Gearbox Mesh Question
 

Anyone knows what they added to the center to center distance in the kit gear boxe?

Dave