The Frame thread

[akoscielski3]

the things you should think about while building/designing a frame is

- torque (push through robots playing defence)
- speed (get around the field quickly
- Light frame (don't waist all your wieght on the frame)
- Strong frame (haveing to fix somthing on it or bending it back in place, can cost you the regional if you can't do it fast enough)
- Easy to repair ( ^ )
- easy access points to put frame together ( including wireing, attaching parts, fixing. You don't want to spend a lot of your days during build season building the chassis
- Easy to make ( ^ )
- simple to design the rest of the robot mechanisms on top of it (useing only a few new holes and bolts to attach the mechanism ontop of the chassis, or inside the chassis)

These are things that i have learned over the years that must be thought of while designing a chassis.

[akoscielski3]

Originally Posted by BrendanB

If it is the same type of tranny as the AM supershifters then by rotating one 90 degrees puts the output shafts at the same level.

Not if they are using Gen2 Andy mark transmissions, the output shaft is not in the middle, but lowered. making the output shaft moved to the side and up higher. unless he is using a different transmission though.

[Chris is me]

Originally Posted by akoscielski3

Not if they are using Gen2 Andy mark transmissions, the outdut shaft is not in the middle, but lowered. making the output shaft moved to the side and up higher. unless he is using a different transmission though.

He's using the AM Supershifter, which doesn't have a centered output shaft.

Originally Posted by Marc S.

http://www.simbotics.org/media/videos/presentations

If nothing else, you can build a super easy drivetrain like the one above, that is also "better than 90-95% of teams". Certainly better than the tank drive and very simple.

This is an amazing video and should be required viewing for all rookie teams.

[akoscielski3]

Originally Posted by Chris is me

He's using the AM Supershifter, which doesn't have a centered output shaft.

I see now, i've never really seen these or even looked at them to use on a chassis. Does anyone know if they are better than Gen 2's??

[JesseK]

The major flaw I saw at champ's with design that Alex posted is with the side rails -- the ones that are supposed to back the bumpers. 973, 254, 968, and 1868 all used the same exact drive train with minor differences. Their bumper-backing side rails were made out of 1/2" box tubing.

On 3 out of the 4, that 1/2" box tubing was warped or bowed inward by 1/8" to 1/4" -- somewhat negating its effectiveness and being technically illegal to the most pedantic of bumper rule interpretations. To be honest, 99% of 2-level welded frames I saw are in violation, even ours. It's simply too difficult to get that thing 100% straight if it's not perfectly flat on a welding table

1" box tubing could possibly make the 2x1" vertical frame members torsion/warp rather than simply the side rail, which would then stress the side rails that hold the wheels. I'd consult with a welder before giving that concern any weight though. Perhaps Cory will chime in if he sees this.

It's easy to prevent warping during welding on a 2D frame (just the 2x1 rails). Yet things can get very tricky when moving to a level that isn't clamped directly to the welding table. It's one of the many reasons why WCD has been a very successful drive train for so many years -- its function:simplicity "ratio" is unsurpassed, thus it mitigates many of the issues that more complex frames have. Compliance with bumper rules in recent years has been the root cause of the extra necessary complexity of side rails.

[Grim Tuesday]

Originally Posted by Jeffy

Having a moving robot for the first time in week 3 is very good. We haven't had one moving in the last two years until sometime at the beggining of week 4. Your current timeline seems fine to me. Except: Your frame may a bit too complex if it takes a week to cut and weld parts. Spending a few days to achieve a simpler solution can save you days in the future.

For this next part, don't think I am saying any of this is wrong, but they are questions you need to answer:
1. Why shift?
2. Why treads?
3. Why T-slot?
4. Why multiple heights of tubing structure?
5. Live vs Dead axle

These are all questions you have to answer for your team. There is no universal best option. The best way to design and build a drivetrain is the way that works for your team.

Don't get me wrong, we didn't move until week 6. Akoscielski3, none of your images aren't there.

We do have sheet metal capabilities, so I would be interested if any of the team IFI teams could show us how they do their frames, or just any sheet-metal teams.

I wonder if anyone has done carbon fiber, or other "space age" material frames...

[artdutra04]

Originally Posted by Grim Tuesday

We do have sheet metal capabilities, so I would be interested if any of the team IFI teams could show us how they do their frames, or just any sheet-metal teams.

We have two sheet metal machine shop sponsors, and have used sheet metal for our base chassis/drivetrain in 2007, 2009, 2010, and 2011. 2007 and 2011 were 6WD, 2009 was 4WD, and 2010 was independent swerve. Here's some photos of our 2011 drive train:







This drive train was an absolute tank. Everything shown in the top CAD model (chassis, gearboxes, wheels, chain, etc) came out to 37.4 lbs. Each of our 2-speed gearboxes (custom ones made from a la carte AndyMark gears) weighed less than a stock ToughBox, and were geared for speeds of 6 ft/sec and 16 ft/sec at nominal load. The center shaft is direct-driven from the gearbox output, with the end two wheels being powered by 25p roller chain. All shafts are 1/2" 12L14 steel hex, with all shafts being live axle (it's the simplest way to power Colson wheels). Except for the custom sheet metal and COTS AndyMark parts, all other fabricated parts could be made on a manual lathe.

Even without a belly pan, this chassis was extremely rigid and had no noticeable flex. Once assembled during the build season and run through its initial break in period, we haven't touched it. Nothing broke, nothing needed adjusting, nothing needed replacement.

Edit: If you're interested, I've posted the CAD model of our entire 2011 robot to CD-Media.

PROTIP: If you can't get powder-coating, use enamel spray paint. If you properly clean all parts ahead of time (e.g. use acetone) and let the paint cure for at least 24 hours, it's nearly as durable as powder-coating and much cheaper.

[akoscielski3]

Originally Posted by Grim Tuesday

Akoscielski3, none of your images aren't there.

I can't figure out how to get them up ... can you help me

thx

[artdutra04]

Originally Posted by akoscielski3

I can't figure out how to get them up ... can you help me

thx

You are linking to photos on your own hard drive, only you can see those on your own computer. For everyone to see them you need to upload them to an image hosting website (like imgur).

[AdamHeard]

Originally Posted by JesseK

The major flaw I saw at champ's with design that Alex posted is with the side rails -- the ones that are supposed to back the bumpers. 973, 254, 968, and 1868 all used the same exact drive train with minor differences. Their bumper-backing side rails were made out of 1/2" box tubing.

On 3 out of the 4, that 1/2" box tubing was warped or bowed inward by 1/8" to 1/4" -- somewhat negating its effectiveness and being technically illegal to the most pedantic of bumper rule interpretations. To be honest, 99% of 2-level welded frames I saw are in violation, even ours. It's simply too difficult to get that thing 100% straight if it's not perfectly flat on a welding table

1" box tubing could possibly make the 2x1" vertical frame members torsion/warp rather than simply the side rail, which would then stress the side rails that hold the wheels. I'd consult with a welder before giving that concern any weight though. Perhaps Cory will chime in if he sees this.

It's easy to prevent warping during welding on a 2D frame (just the 2x1 rails). Yet things can get very tricky when moving to a level that isn't clamped directly to the welding table. It's one of the many reasons why WCD has been a very successful drive train for so many years -- its function:simplicity "ratio" is unsurpassed, thus it mitigates many of the issues that more complex frames have. Compliance with bumper rules in recent years has been the root cause of the extra necessary complexity of side rails.

We actually didn't have the same style bumper support, we just had some "cheater plates" (as we called them) that came out and touched the bumper (1x~3.5"x.125" plates riveted on) every 8" or so. The actual load of the bumper was really only supported by the two bumper mounts that were 1" diameter aluminum round sitting flush against our siderails.

[akoscielski3]

Originally Posted by artdutra04

You are linking to photos on your own hard drive, only you can see those on your own computer. For everyone to see them you need to upload them to an image hosting website (like imgur).

K thx i think i fixed them now! Thanks ... now i know lol

[roystur44]

Take a look at our galleries of previous builds. We use sheet metal and rivets for almost all the parts on the robots we build.

laser cut .090 5052 alum
student designed using SolidWorks



https://picasaweb.google.com/971.FIRST/2011Build#

[Duke461]

I don't have access to a CAD file right now, but i have a picture of the drivetrain:

I apologize for the massive size, but i couldnt figure out how to make it smaller (thread for original photo and topic: http://www.chiefdelphi.com/media/photos/36226)
This year we made a laser cut Sheet Metal Drivetrain done by Rowe Trucking. Its thickness is 1/8'', and is extremely strong. However, we could cut the thickness down to help weight wise.
All in all, i liked the drivetrain, but i really like simbotic's "kitbot on steroids".
P.S. A box frame isnt half bad either.
Hope this helps,
Good Luck,
-Duke

[roystur44]

here is another link to our 2011 build season. Has some great pictures of our frame.

https://picasaweb.google.com/1045493...on?feat=email#

http://tinyurl.com/3vsbadq

[548swimmer]

Originally Posted by Grim Tuesday

Don't get me wrong, we didn't move until week 6. Akoscielski3, none of your images aren't there.

We do have sheet metal capabilities, so I would be interested if any of the team IFI teams could show us how they do their frames, or just any sheet-metal teams.

I wonder if anyone has done carbon fiber, or other "space age" material frames...

Though not a frame, we were fortunate enough to have a sponsor donate carbon fiber drive shafts for our support structure and arm.

http://www.flickr.com/photos/robosta...7626347607815/