27-08-2011 17:03

steelerborn

Re: pic: Cobra box

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.

27-08-2011 17:08

Akash Rastogi

Re: pic: Cobra box

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.

27-08-2011 17:11

Andrew Schreiber

Re: pic: Cobra box

Quote:

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.

27-08-2011 17:56

steelerborn

Re: pic: Cobra box

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.

27-08-2011 18:23

Andrew Schreiber

Re: pic: Cobra box

Quote:

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.

27-08-2011 21:57

AdamHeard

Re: pic: Cobra box

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.

28-08-2011 01:08

steelerborn

Re: pic: Cobra box

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).

28-08-2011 01:17

Hawiian Cadder

Re: pic: Cobra box

Quote:

Originally Posted by 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).

28-08-2011 14:36

Jeffy

Re: pic: Cobra box

The often better way than using worm gears.

However, sometimes you really just need that worm gear or anti back-drive pins (like on a winch for hanging), but often you can get away with "passive assistance."

Just wanted to make sure this option was considered. Best of luck, it looks pretty awesome.

28-08-2011 15:50

ratdude747

Re: pic: Cobra box

Quote:

Originally Posted by Jeffy The often better way than using worm gears. However, sometimes you really just need that worm gear or anti back-drive pins (like on a winch for hanging), but often you can get away with "passive assistance." Just wanted to make sure this option was considered. Best of luck, it looks pretty awesome.

28-08-2011 17:00

steelerborn

Re: pic: Cobra box

This is what we usually do with all of our arm systems. This is a great way to get a desired effect without having to change a gearbox. However designing an arm correctly with a transmission that can hadle the arm without assistance, is the best option. For logomotion having the ability to back up grab a tube and lift your arm all the way back over to the other side to score was a really big time advantage that I noticied 973 perform over and over again. They were able to hang a lot of tubes very quickly due to this advantage. Maybe Adam can say something about this?

28-08-2011 18:52

apalrd

Re: pic: Cobra box

It's possible to counterforce even if the arm crosses vertical. It's just slightly harder. But still possible.

Good design includes counterforce. Just saying.

I know many teams who could hang as fast as 973. Watch IRI.

28-08-2011 19:37

steelerborn

Re: pic: Cobra box

I know that is is possible to add a counter weight system, however I just try to keep KISS in mind. The only point I was making was that it is better to design something right. By knowing that even if you have no counter weight your transmission should still be able to work your arm. I have no say in what the kids want to do, if they want to have a counter weight that is fine it is my job to make sure they know what to do, and to answer their questions. This was just a fun side project based off of criteria that I set.

28-08-2011 22:00

AdamHeard

Re: pic: Cobra box

Quote:

Originally Posted by steelerborn This is what we usually do with all of our arm systems. This is a great way to get a desired effect without having to change a gearbox. However designing an arm correctly with a transmission that can hadle the arm without assistance, is the best option. For logomotion having the ability to back up grab a tube and lift your arm all the way back over to the other side to score was a really big time advantage that I noticied 973 perform over and over again. They were able to hang a lot of tubes very quickly due to this advantage. Maybe Adam can say something about this?

29-08-2011 01:28

Jeffy

Re: pic: Cobra box

While taking another look at this, I thought of something else. You may want to consider putting the plates that support the worm on the "outside" and bolting into the side plates. This way the thrust loads from the gearbox (which will often be shock forces, not light constant ones) will pull in-line with the bolts used to bolt the plate on.

29-08-2011 15:27

roboticsgoof95

Re: pic: Cobra box

DUDE THATS SWEET! Solidworks?

29-08-2011 16:42

steelerborn

Re: pic: Cobra box

Wow a lot of great ideas I will add those in this week. Thanks everyone for the input.

This rendering was done in ProE 5/ Creo, but I am also working on a Solidworks duplicate at my college.

30-08-2011 08:24

roboticsgoof95

Re: pic: Cobra box

Which do you find easier to use? I was trained in Solidworks and find it very easy... but I am just curious.

30-08-2011 12:49

steelerborn

Re: pic: Cobra box

Hmm good question. I was first trained in ProE and then self taught myself SolidWorks and Autodesk Inventor. I would say for making individual parts SolidWorks takes the cake, the ribbon structure and layout is very very simple to both understand and use. However when you get into more complicated assemblies, ProE is better. ProE does a better job at keeping individual parts organized in a complex assembly. SolidWorks puts mates under its own tab and you have to find which one you want to modify, ProE automatically keeps mates together by part. SolidWorks outlines most lines (you can turn this off) and makes the part look very nice and easy to see. ProE is a little hard to stare at sometimes, but you can get used to it. ProE creates far better renderings than SolidWorks in my opinion.

30-08-2011 13:00

roboticsgoof95

Re: pic: Cobra box

Quote:

Originally Posted by steelerborn Hmm good question. I was first trained in ProE and then self taught myself SolidWorks and Autodesk Inventor. I would say for making individual parts SolidWorks takes the cake, the ribbon structure and layout is very very simple to both understand and use. However when you get into more complicated assemblies, ProE is better. ProE does a better job at keeping individual parts organized in a complex assembly. SolidWorks puts mates under its own tab and you have to find which one you want to modify, ProE automatically keeps mates together by part. SolidWorks outlines most lines (you can turn this off) and makes the part look very nice and easy to see. ProE is a little hard to stare at sometimes, but you can get used to it. ProE creates far better renderings than SolidWorks in my opinion.

30-08-2011 13:01

AdamHeard

Re: pic: Cobra box

Quote:

Originally Posted by steelerborn Hmm good question. I was first trained in ProE and then self taught myself SolidWorks and Autodesk Inventor. I would say for making individual parts SolidWorks takes the cake, the ribbon structure and layout is very very simple to both understand and use. However when you get into more complicated assemblies, ProE is better. ProE does a better job at keeping individual parts organized in a complex assembly. SolidWorks puts mates under its own tab and you have to find which one you want to modify, ProE automatically keeps mates together by part. SolidWorks outlines most lines (you can turn this off) and makes the part look very nice and easy to see. ProE is a little hard to stare at sometimes, but you can get used to it. ProE creates far better renderings than SolidWorks in my opinion.

30-08-2011 13:06

steelerborn

Re: pic: Cobra box

Yeah it is just really a personal decision. I really like ProE because all of the support you get from PTC is just amazing. It is very very helpfull for the build season.

Really?! that helps out a lot I haven't really done to much in SolidWorks yet in school so it is just me playing on the computer. Making a robot in both programs is possible, I like making things in ProE and then redoing the same parts in SolidWorks as good practice. Although I don't know a lot of SolidWorks shortcuts and tips like I do with ProE. But PTC really just makes team communication a lot easier between FAB, CAD, and all the rest of the team.

30-08-2011 13:09

jhouser

Re: pic: Cobra box

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!

Quote:

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.

30-08-2011 13:11

roboticsgoof95

Re: pic: Cobra box

Quote:

Originally Posted by steelerborn Yeah it is just really a personal decision. I really like ProE because all of the support you get from PTC is just amazing. It is very very helpfull for the build season. Really?! that helps out a lot I haven't really done to much in SolidWorks yet in school so it is just me playing on the computer. Making a robot in both programs is possible, I like making things in ProE and then redoing the same parts in SolidWorks as good practice. Although I don't know a lot of SolidWorks shortcuts and tips like I do with ProE. But PTC really just makes team communication a lot easier between FAB, CAD, and all the rest of the team.

30-08-2011 13:15

steelerborn

Re: pic: Cobra box

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.

30-08-2011 14:34

JesseK

Re: pic: Cobra box

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.

30-08-2011 14:50

Brandon Holley

Re: pic: Cobra box

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

30-08-2011 14:59

Andrew Schreiber

Re: pic: Cobra box

Quote:

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.

30-08-2011 15:26

Brandon Holley

Re: pic: Cobra box

Quote:

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.

30-08-2011 18:25

jhouser

Re: pic: Cobra box

Well said Brandon.

Quote:

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