Re: Gear Teeth Clearance
 

Consider what you're getting from making your own gears. I find it very hard to believe that you can't just find a gear with the right gear teeth from Vexpro, WCP, Andymark, SDP-SI, etc and modify it to fit your design. Unless you want to make gears just for its own sake, I don't see any reason to try it. It wastes a lot of time and labor resources on something that won't give you any competitive edge.

You have been warned by many others smarter than me above.:p

Re: Gear Teeth Clearance
 

That's not strictly true. A good waterjet will produce little taper on a 1/4" or so thick part. One with a tilting head will effectively produce zero taper and hold .001-.002" overall tolerances. You certainly can cut a gear that will run at relatively low speed, but it will only be an approximation of the involute tooth profile and it will mesh relatively poorly with a COTS spur gear. I had some very large ring gears waterjetted for a project at work and they worked well.

That being said, whatever the OP is trying to do can almost certainly be done faster, easier, and with higher quality by adapting the design to use COTS gears, even if they are steel Martin gears that require putting a custom bore in.

Re: Gear Teeth Clearance
 

Put bluntly, there is a VERY good chance that you are wasting your time with endevour. If your team has the massive skills to design their own gears and gearboxes in your rookie year, then you can definitely turn that skill towards building innovative and robust mechanisms that blow everyone else out of the water. Seriously, consider using a couple COTS parts instead.

Re: Gear Teeth Clearance
 

For the love of all that is good, don't waste your time making your own gears. It is your first season, and frankly, I have never heard of any team that has made their own gears and used them successfully on a high-load mechanism. This doesn't mean it can't be done, but you can save yourself a ton of time and money and just buy them online. You will be much happier.

Re: Gear Teeth Clearance
 

I agree with all those who encourage the OP to find another way but if you won't be discouraged, I say more power to you. Live and learn. Either you learn or you show us and we learn.

I would ask the OP not to bet the entire season in it if you can help it. Have a back up plan, another source for the product or another option. Something to keep from having your robot be a box of rocks bot.

YMMV.

Dr. Joe J.

Re: Gear Teeth Clearance
 

And if you decide to use COTS gears (lots of good sources), a good general guide for gear spacing is (1/2)PD1 + 1/2(PD2) + .003. (in inches).

PD1 is Pitch Diameter of Gear 1, PD2 is Pitch Diameter of Gear 2.

Edited - i meant .003!

Re: Gear Teeth Clearance
 

I hope it works out well for you, I really do.
Perhaps you have a very unique mechanism and making gears is the only way you see things working. But look at all the sources for off the shelf parts.
I design gears for work, we manufacture custom gears. It is expensive and hard work, even with the proper machinery and tools. If you can buy gears I would think you would save time and money.

Op you are completely disregarding people like Cory from 254 advice. That's for lack of batter words very stupid. Very stupid. If you did not know 254 is one of the best teams in Frc and makes a lot of their own parts. Making your own gears is useless imo when there are so many stock options and you will probably have more issues with them then its worth. What you may or may not have realized yet is the frc community is helpful. As a rookie team you do not know what your doing.

But I can't force you to make a better decision you will have to learn the hard way.

Re: Gear Teeth Clearance
 

Don't cut your own gears. There is a 99.9% chance that you are spending your time on something that could be done much more easily with COTS parts. I have all the right equipment and I still wont do it if there is ANY way I can get the pitch and tooth count I need from an off the shelf part. Revisit your design, shop around, call suppliers, do what you need to do to not have to cut your own gears.

Re: Gear Teeth Clearance
 

All cots gears are the best way to go. But if you still insist on generating your own gears, I would use a website called rush gear that has software for generating custom gears quickly. That way you have an accurate cad file to reference, create dxf's, etc.
http://www.rushgears.com

Again, I'll re-emohasize cots gears are the way to go.

Re: Gear Teeth Clearance
 

Thank you for this and all the positive input.

Re: Gear Teeth Clearance
 

I know the additional .006" is some fudge factor, effectively trading gear life for less friction in operation. But the number I'd learned from oral tradition* is .003" or so. What are the benefits of adding the extra distance?

*Even before I learned this from other FIRSTers, I knew a variation on this from racing R/C vehicles, which have a similar opinion of gear life vs. speed**; there, the conventional wisdom is to run a piece of paper between your pinion and spur gears to ensure "proper" spacing--and a piece of paper is about .002" thick.

**If you haven't gathered from the "racing" part, they skew towards speed.

Re: Gear Teeth Clearance
 

Bring the heat mate!

Although I'd have a concern about how crucial the gear is because another advantage to COTS or close to COTS is the ability to not have to cut into your withholding allowance. While the success of the part may at this point in time be unknown, learning is always worth it.

Just don't go mental and if you don't get it right in time, consider making it an off season refinement.

Re: Gear Teeth Clearance
 

Just a quick note, this was from over a month ago. We went with vex gears after being suggested

Re: Gear Teeth Clearance
 

Care to share what the original intent was or any details?