easy way to find your robot weight.

[Tytus Gerrish]

if you are designing your robot in cad. it is a simple command of using Mass Proprieties. in autocad's case the command is massprop. the mass properties will tell you the volume of 3d objects all you have to do is take that volume and multiply it by how much that material weighs. like a cubic inch of aluminum weighs 0.0975 pounds roughly. this site http://www.allmeasures.com/Formulae/ has spreadsheets and tables that let you just let you plug in your numbers and you have your weight.

and thats my tip of the day.

[sanddrag]

Thanks for the tip. Although I think anyone who models their robot in AutoCAD is at a great disadvantage. Inventor is the way to go. And you can set the material properties for each part and find out the weight of an entire assembly instantly!

[David Guzman]

Thanks for sharing tytus but I also agree it is much easier to use inventor. Althoug if the only thing abelable is AutoCAD then yes this would come handy and save some time.

Dave

[Elgin Clock]

Originally Posted by sanddrag

Thanks for the tip. Although I think anyone who models their robot in AutoCAD is at a great disadvantage. Inventor is the way to go. And you can set the material properties for each part and find out the weight of an entire assembly instantly!

Yep.. Same with SolidWorks.. somehow.. idk.. I did it once. lol

[Michael Hill]

You could just build the robot and if it's too heavy in the end, take a chain saw to the parts that are heaviest...lol. But I guess that doesn't really support the careful engineering aspect of FIRST now does it?

[mechanicalbrain]

Does Inventor have the weight listing for carbon fiber?

[Greg McCoy]

Originally Posted by mechanicalbrain

Does Inventor have the weight listing for carbon fiber?

If not, you can add it

[Madison]

Please note that many prefabricated models of FIRST-specific parts made available over the internet are not accurately modeled and require some modification such that they accurately reflect their true weight. The battery model available at www.firstcadlibrary.com, for example, weighs 5 lbs. as per Inventor.

To correct these errors, the easiest thing to do is learn the component's weight and manually manipulate the density of the model so as to make it match its real counterpart.

Further, please understand that both wiring and fasteners can quickly become a significant portion of your robot where its weight is concerned -- sometime as much as 15%. Modeling these things is both difficult and resource intensive, so many people leave them out.

[jdiwnab]

I used inventor to estimate the weight for last year's bot. I estimated that there might be about 10-20% error becuase of wires, fastiners that I didn't feel like modeling all of, welds, and just plain error. Inventor estimated about 105 lbs with battery, and I think it came out to 110 lbs with battery. So not to bad, as long as you expect some deviation. It can help you with planning, but you still need to weigh it.

As far as the battery goes, if you model it and the weight is off, weigh the real thing and use a calculator (or paper) and the volume info on Inventor and change the density appropratly (density=mass/volume), but you might need to convert units.

[Arefin Bari]

Here is what I think... Inventor is a good tool to use but Autocad is the only software that has been used in the industry (there are some companies who uses inventor). Yes... it is easy for us to draw in inventor but Autocad is a really powerful tool.

Few examples teams using Autocad to design a robot:









I personally use inventor and have drawn bunch of robots. But, I haven't been able to find a Robot cad drawing like this in inventor (like swampthing's and Pink's).

Autocad does have it's own way to weigh the robot. You just have to know what you are doing.

Tytus: I personally would like to challenge you to find a robot drawn in inventor that looks like this.

[Madison]

While I'm not Tytus, I'd like to point out that -- in my opinion -- it's quite easy to design aesthetically pleasing, functional machines in Inventor.

http://www.chiefdelphi.com/media/photos/28778

[Greg McCoy]

I think most automotive, aerospace, and other large engineering companies use one of the big three: Unigraphics (GM/Delphi), Dassault Systems/IBM Catia (Boeing/Ford?/many foreign car companies), or Pro/Engineer. I think Autodesk products (Inventor, at least) are more geared toward small/medium business. I like Inventor, but I don't think it's used widely in big companies.

Hopefully someone will correct me if I'm wrong...

[Andy A.]

OK. Autocad is great, and its been in use forever. But, as soon as you try to use it to draw something 3d, your digging a hole with a stick. It's old, archaic stuff. It's not even in the same class as Inventor.

Yes, you can use it to go 3d, but why? Inventor or Solidworks were made from the ground up to do parametrics. Autocad was made to make flat things, like floor plans and such, which is why it's still used by architects. The last time I checked, you still had to make holes using Boolean subtraction (make the plate, make a cylinder, subtract the cylinder from the plate and you have a hole. Need to move the hole? Fill the first hole back in with a new cylinder, then subtract another from the new location. Inventor is as easy as drag and drop).

If you have to make a 2d design, Autocad is fast and will beat Inventor every time for speed (although inventor certainly can do it, it just needs a better spline tool). As soon as you try to make something more complex then a flat piece of sheet metal, drop autocad like a ton of bricks and boot up Inventor. There is no way you could pay me to draw up a drive train in autocad. I'm sure some people do it, but there's no reason to anymore. I would be amazed if the teams shown used autocad to do anything more then lay out the design.

On a side note, Inventor is geared for small to mid sized business. Something like Catia costs tens of thousands of dollars to implement (not just the software, but the computing power needed). So programs like Catia and Pro-E are used almost exclusively by large companies that need that kind of power. For the rest of us with more like four thousand to spend, there is Inventor and Solidworks (the two major players, there are probably others). Inventor is made by the same people who make Autocad, so you would think that with the massive built in user base Inventor would just own the market. But, Solidworks has taken a big lead and is mopping the floor with Inventor. Both are pretty good programs, but preference is for solidworks.

-Andy A.

[David Guzman]

I have been taking a Drafting class for almost a year and a half now, and I have had the opportunity to work with both Inventor and Auto-CAD. To tell you the thruth as far as mechanical designs is concern Inventor is a lot better. Anything you can do in Auto-CAD you can do in Inventor a lot faster and with a lot more helpful tools.

As far as weight is concerned you can always find the weight of things that you downloaded from on-line like motors and batteries and then change its properties in Inventor.

Honestly if I was asked to draw swampthing's robot i would choose Inventor without hesitation.

Just my $.02
Dave

[ChrisH]

Originally Posted by mechanicalbrain

Does Inventor have the weight listing for carbon fiber?

For carbon epoxy composites (the most commonly available form of carbon fiber) you can use a density of 0.056 lbs/cuin. That is for a high performance, aircraft grade composite with about 33% epoxy content. If you're slapping wet resin on carbon cloth it will be a little lower strength and density.