I was wondering what you guys use to build the basic frame. Last year we used 1x1 Al and welded it together. This year the majority of the team wants to use 80/20 and bolts. Personally I think welding is cooler and should be used at every chance possible, but what do u guys do?
*Originally posted by Smrtman5 *
**I was wondering what you guys use to build the basic frame. Last year we used 1x1 Al and welded it together. This year the majority of the team wants to use 80/20 and bolts. Personally I think welding is cooler and should be used at every chance possible, but what do u guys do? **
Ok, heres my hat in the ring…
I would recommend if you were building a frame for a robot or something similar. I would take either 1.5 Inch or 2 inch aluminum angles and use that to build your lower frame. It you want to take the cheaper alternative, buy some steel angles, you will find them by the aluminum in your local hard-ware store. If you get the ones with the “holes” then it should be cheaper then the aluminum about 3:1.
WARNING WARNING DANGER Smrtman5:
If you use steel, it is very hard to cut. The ones with the holes are easy to bolt, and the output is strong enough to take a 130 pound impact. I recommend two bolts with lock washers for each angle meet. Build the bottom frame first, that would be your basic “under side”. Then you can decide how to set you motors up and all that stuff. If you are doing Direct Drive of FP’s then the layout will be easy. I can talk you through it if you need the help.
Then install angles off each of the corners, If you go much higher then 2 feet high, I recommend putting in cross bars, or angles to insure stability. Then build another frame piece, the same as the bottom piece and attach it to the top of the angles.
This will give you a sturdy robot that is very easy to build. I know personally because this is the route I have taken to construct mine.Its not super easy but this is a very simple yet affordable way to get the project done. I have pics if you need to see how to build such a device.
You left your post kind of hazy, so I hope this was what you were looking for, if not re-clarify.
-Greg The Great
This year our frame came from the kit. We took the two extrusions from the kit and cut them down the center, thus leaving 4. Then, we trimmed down 2, cut all the edges at 45 deg. angles, and used a small piece of angle bolted in each corner to hold it together. It worked great. Really quick and simple, and it was strong too. We usually shoot for aluminum extrusion, or aluminum sheets for our chassis.
In the past we have used 1.5" aluminum angle, 1.5" steel angle (terrible, terrible choice, never use this stuff EVER! Way too heavy) and 1" 80/20 extrusion. For ease of use and the ability to make quick changes without having to cut welds or drill holes, 80/20, or Bosch extrusion is king. However, the expenses involved with fasteners and the material its self quickly pile up, as does the weight. I remember reading somewhere that 1" square profile aluminum gives much more strength than 1" angle for the same weight.
Cory
Our team for the past three years have used IPS extruded aluminum (similar to the Bosch stuff) - they are one of our sponsors! It’s like an industrial Lego or Erector set - I highly reccomend it! Not everyone has the equipment or the skills to weld aluminum. It is very easy to build frames and structures with it and most importantly you can easily try things and make prototypes of an idea - and then make changes later! Our teams robot is about 98% built by students and a big part of this is because of the extruded aluminum that we use. I will agree with an earlier post about the weight of fasteners being a disadvantage, but you learn how to substitue lighter configurations once you finalize a layout. If you have any questions about using extruded aluminum feel free to send me an email or send a message to our team roboclub@yahoogroups.com and many of the students would be happy to help.
Scott
If you have the time and resources available to you and your team, you may want to consider first prototyping your chassis with 1"x1" extruded aluminum (80/20, for example) so that you can quickly and easily make changes.
Once you’ve settled on a design that you like, rebuild that chassis from 1"x1" Al box lengths. It’ll be comparably strong and rigid, but much, much lighter. If I recall correctly, this is a methodology that Wildstang (111) employs.
As I’ve mentioned in the past, I don’t like extrusion because, even as heavy as it is, it isn’t too difficult to break, shear, or gnarl in unnatural ways.
Personally, I design a chassis to suit my drivetrains – but I rarely design typical drivetrains. This means that I don’t rely on any single method or material for my chassis designs, but rather, I try to find the material that is most suited for my needs. It’s resource intensive and usually means that getting your robot driving around takes a bit longer than other teams, but it still works pretty well.
I guess it mostly comes down to your design/strategy. The geometry of Bosch and 8020 has certain strength benefits over standard structural extruded aluminum. However, if you don’t plan on doing a whole lot of crashing and banging, and have the facilities and the manpower (experience), I’d use welded aluminum structural extrusion (either angle, channel, or possibly even square).
Steel is far too heavy and difficult to cut. I don’t believe it’s worth the weight versus the benefits for use in structural members. Bosch/8020 does have a certain ease-of-use factor to benefit, but if you support your frame correctly, you shouldn’t need to ever take your frame apart to fix a broken/bent extrusion. Use cross-beams to support other extrusions and disperse impact energy accross your entire frame and you should be fine.
*Originally posted by Jnadke *
**
Steel is far too heavy and difficult to cut. I don’t believe it’s worth the weight versus the benefits for use in structural members. Bosch/8020 does have a certain ease-of-use factor to benefit, but if you support your frame correctly, you shouldn’t need to ever take your frame apart to fix a broken/bent extrusion. Use cross-beams to support other extrusions and disperse impact energy accross your entire frame and you should be fine. **
Dont insult my favorite material. I am just kidding with you. Steel while hard to cut, will always win in a collision with any aluminum.
I prefer it, but I don’t have a life, all I do is make comparison charts from metal to metal and motor to motor. For a big bot, aluminum will always be the weight king.
-Greg The Great
I beg to differ, Steel is just WAY too heavy. In 2002, thinking we woud need a very strong frame, we used steel. The frame, with NOTHING on it weighed over 60 lbs. This severely limited us in the design of the rest of our robot, and is not something I would ever want to do again.
Cory
the Baxter Bomb Squad fell in love last year. With extruded aluminum item. The stuff is great. It’s strudy as all get out, lighter than almost anything, and because it has these great little bolt things designed to connect pieces of it you don’t have to worry about taking on the nearly impossible task of aluminum welding(thank god).
We used one frame last year that weighed 12 pounds(less than last years parts list book) and we were one of that fastest robots out there. Even at our very high speeds we had multiple collisions and didn’t notice any damage to the frame(other than astetics ofcourse).
For the past 4 years our team has been using 80/20 for our frame and it has worked out really well. One advantage is that we usually have a base ready for our drivers to practice with early on because 80/20 is so easy to work with.
an engineer on my team sugested honeycomb
*Originally posted by Tytus Gerrish *
**an engineer on my team sugested honeycomb **
Actually, the honeycomb by itself would make a barely effective crushable bumper. (Unless you use titanium honeycomb core, but that would be prohibited along with all other ti.) But bond on some face sheets to make a sandwich structure and you really have something strong and light. It works with foam too.
Hmmm, we had a sponsor a couple of years back that used to make panels like that. Using them at the time was illegal but next year???
*Originally posted by Jnadke *
**Steel is far too heavy and difficult to cut. I don’t believe it’s worth the weight versus the benefits for use in structural members. **
While I can’t dispute that steel is too heavy, it’s not something to totally rule out. It’s definitely strong, as we built similar frames out of steel in 2002 and aluminum in 2003. The steel frame never bent so much as a quarter of an inch… the aluminum one needed to be straightened every third match or so. However, this was not our primary reason for using steel. We had all the equipment and expertise needed to easily cut and weld steel, but none of the facilities to do the same with aluminum. We chose steel because we could work with it on our own, and it was stronger and cheaper than aluminum. Given the choice, I probably wouldn’t do it again, but it fit our needs perfectly in 2002. We had a simple, strong robot that we could build with no outside machining.
*Originally posted by Jeff Waegelin *
**… We chose steel because we could work with it on our own, and it was stronger and cheaper than aluminum. … **
I won’t argue on the first or last point. But there are some alloys of aluminum that are as strong as some alloys of steel. Aluminum is also generally easier to work, unless you’re trying to weld it. But steel is much stiffer. That is for a given load, a steel beam will deflect less than an identical aluminum beam. Of course the steel will weigh three times as much.
The key here is choosing the right material for the right reason. If weight doesn’t matter (you’re way under the limit) or stiffness does, then look at steel. But most of the time aluminum will probably be the better choice, because with careful design you can meet strength and stiffness requirements and still weigh less than a steel structure. You also need to pay close attention to which alloy you are using. Different alloys of the same basic material can have quite different properties.
we used a combination of bosch and maytec? aluminum extrusion.
Why should you care you ask?
we didn’t make a single repair all season to our frame… or to our robot for that matter.
I’d say that you’ll do just fine with some 1" extrusion. It’s cheap and light, and it is easy to assemble/disassemble. Allthough steel is nice, it’ll be easy to get along with aluminum.
The key here is choosing the right material for the right reason.
This is a good point, however if you choose steel, as also you said, that increase the weight drastically. I would think if you were only ramming into things, with a motor and a frame, steel would be ok, but in my past experiences, even with Al frames, weight is a BIG consideration.
Ah yes, now i remembered what i was planning on doing, weighing equal lengths of 80/20 and 1x1 Al tubing. Would anyone happen to know the weight or density of these materials?
I want to say one foot of 10/10 is 4 lbs, but thats just what I think I remember seeing.
*Originally posted by ChrisH *
The key here is choosing the right material for the right reason. If weight doesn’t matter (you’re way under the limit) or stiffness does, then look at steel.
That’s basically the decision we came to in 2002. We had a simple, small robot. With aluminum, we’d probably have ended up about 30 lbs under the weight limit. Our goal-grabbing arms also needed to have no bending and distortion at all when they got hit, which, given their small size, I don’t think could have worked in aluminum. We’d have been straightening pieces all day.