pic: Cobra box

[steelerborn]

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[steelerborn]

All of the gears, shafts, and bearings are all from Mcmastercarr. Trying to get off and away from AndyMark as much as possible and to stick with only Mcmaster.

[Akash Rastogi]

You're better off staying away from bent 1/4" Al. Might as well have two pieces bolted to form the L to mount. Just countersink the bottom screws. If you stick with the bent 1/4" just make sure you have the proper bend allowance in there. Tolerances can be thrown off a bit of bearing holes and such because of the tolerance of the bend, but I guess depending on your shop this could be negligible. Just a thought though.

[jhouser]

Good points regarding alignment and bent plates. It's typical to assume at least a .015" tolerance per bend, which means that our tolerance on the mounting hole locations is probably approximately .030". With a good brake operator and probably a little scrap, you can probably get this down to about .005" or less depending on the amount of time you spend on it.
Ideally, I think for a nice tight tolerance on the axle for the worm, I would say bend a c-channel and then machine it. You should be able to get down to a .0001" tolerance.
One critical feature that I haven't seen mentioned yet is backlash adjustment. Typically, any gear set will require some adjustment for backlash. This will impact the precision of your drive system as well as efficiency and lifetime.
Since I was Jonathan's mentor, I know he's probably already got most of this in mind...can't wait to see the next iteration!

Originally Posted by Akash Rastogi

You're better off staying away from bent 1/4" Al. Might as well have two pieces bolted to form the L to mount. Just countersink the bottom screws. If you stick with the bent 1/4" just make sure you have the proper bend allowance in there. Tolerances can be thrown off a bit of bearing holes and such because of the tolerance of the bend, but I guess depending on your shop this could be negligible. Just a thought though.

[steelerborn]

Thanks Josh Yeah, you read my mind. I have already swapped the side plates out with a C frame lol and I moved the mounting hole locations as well.

[JesseK]

Just throwing this out there to make it easier -- Solidworks also has a little button its popup ribbon that says "View Mates". If you select a part on your render and then click the button, it lists all of the current mates for the part. Then you can edit/delete the mates as you see fit. Works wonders when doing distance mates for welded parts.

[Brandon Holley]

Ah the infernal CAD software debate...

I've really found that the software someone "learned to CAD" on, tends to be their favorite (I wonder why??). It really comes down to personal preference.

My only recommendation to students is to stay flexible with what software you use. This isn't an Apple vs. Microsoft debate. Ive had jobs where I've had to work within Pro/E, SolidWorks and Inventor in one day, often using 2 packages at a time. I know many of my classmates from Northeastern went out and learned all kinds of software packages on their various co-ops, and now full-time jobs.

Don't limit yourself to one software package. As students, you have access to all kinds of free software, try them out, even just for kicks!

-Brando

[Andrew Schreiber]

Originally Posted by Brandon Holley

This isn't an Apple vs. Microsoft debate. Ive had jobs where I've had to work within Pro/E, SolidWorks and Inventor in one day, often using 2 packages at a time.

Even in the Apple v Microsoft v Linux debate... stay flexible. There have been many days where I go from Windows -> Mac -> Linux and back several times. It is the same reason I know several different programming paradigms, staying flexible gives your more ways to solve a problem effectively.

[Brandon Holley]

Originally Posted by Andrew Schreiber

Even in the Apple v Microsoft v Linux debate... stay flexible. There have been many days where I go from Windows -> Mac -> Linux and back several times. It is the same reason I know several different programming paradigms, staying flexible gives your more ways to solve a problem effectively.

I was thinking in more "old school" terms when there was a lot bigger of a gap between the two companies (and Linux). Just like us mechanical guys, you software guys need to stay flexible (probably even more so) as you pointed out.

-Brando

[jhouser]

Well said Brandon.

Originally Posted by Brandon Holley

Ah the infernal CAD software debate...

I've really found that the software someone "learned to CAD" on, tends to be their favorite (I wonder why??). It really comes down to personal preference.

My only recommendation to students is to stay flexible with what software you use. This isn't an Apple vs. Microsoft debate. Ive had jobs where I've had to work within Pro/E, SolidWorks and Inventor in one day, often using 2 packages at a time. I know many of my classmates from Northeastern went out and learned all kinds of software packages on their various co-ops, and now full-time jobs.

Don't limit yourself to one software package. As students, you have access to all kinds of free software, try them out, even just for kicks!

-Brando

[Andrew Schreiber]

Originally Posted by steelerborn

All of the gears, shafts, and bearings are all from Mcmastercarr. Trying to get off and away from AndyMark as much as possible and to stick with only Mcmaster.

... Why?

[steelerborn]

Yeah that was another option that I was thinking of, but we have two great companies that make our parts and should be able to handle those no problem. As far as getting away from AndyMark is concerned, Mcmaster has always given us great customer service and we have never had any delays from them. AndyMark has not, and Mcmaster has a much larger supply than AndyMark, this way we don't have to order from multiple places. This is just the team's experience with AndyMark and we decide to purchase from the place that is the best for the customer.

[Andrew Schreiber]

Originally Posted by steelerborn

Yeah that was another option that I was thinking of, but we have two great companies that make our parts and should be able to handle those no problem. As far as getting away from AndyMark is concerned, Mcmaster has always given us great customer service and we have never had any delays from them. AndyMark has not, and Mcmaster has a much larger supply than AndyMark, this way we don't have to order from multiple places. This is just the team's experience with AndyMark and we decide to purchase from the place that is the best for the customer.

Fair enough. My experience with AM has been very different than yours it seems.

[AdamHeard]

It might be cheaper and lighter to do the worm gear earlier in the reduction, so that it can be smaller. That will also reduce the thrust loads you'll have to deal with in your gearbox. Do you have a thrust bearing on the shaft with the worm?

AndyMark doesn't ship as fast as mcmaster for the same price, but who does? Mcmaster's speciality is fast and good service for a price premium.

Andymark has been good to us, we've had a few defects and small issues over years, but they've always fixed any issues we've ever experienced. I love the variety of 20dp gears that are already good to go, saves a lot of time.

[steelerborn]

Excellent point Adam. I will look into it, the main reason I did it this way was for simplicity if the motor ever needs to be replaced it would be an easy swap out. I also had the idea of putting a system in place where one could simply disengage the worm gear and allow the arm to be moved manually. Really this was just for fun, and a possible solution to some problems from last season. The anti back driving effect of the worm gear is a huge advantage and allows a mechanical solution to a problem instead of adding in code to achieve the same effect. The bearings on the worm shaft will be thrust bearings however I did not have any thrust bearings in my workspace so I used just standard until I could CAD them sometime this week (only had larger ones from off of an old swerve module). I also did not place any shaft collars on the external parts of the box. Yeah I am a huge fan of Mcmaster, they are huge compared to AndyMark, and I feel like it allows a wider range of materials to do some crazy stuff with. We have had a lot of issues with AndyMark (probably because we are just unlucky). Last season we ordered some transmissions and all of the output shafts were way outside of the tolerances and none of the hubs fit well we had to grind down and press them on. When we bought another set for the real bot everything was fine. Thankfully we got the order in around week 2 and avoided the massive snow storm. Mcmaster is also a company that the students may use even when they are out in the industry so it is a good way to get them to understand how these sites work. This box is in no way attributed to the Bird Brains. We have always been a student designed team with mentors answering some questions. If they want to use this box or anything that I have designed I will usually do a lesson or talk on the design and encourage that they work on their own version, and then help answer their questions. I really hope though that we can get this fabricated to see how it works and functions (don't want them using something that is useless).