My team is thinking of using lots of the aluminum parts to decrease our robot weight, but wanted to know if has the same (or better) strength as the steel parts.
They are not as strong but i don’t see why you couldn’t use them because many teams use it regularly, steel is more springy and aluminium is a but stiffer but steel can hold more weight. Overall the lightness of aluminium is a clear advantage though.
Aluminum should work fine as far as structural support for the robot goes (take a look at most competitive robots; they are almost all made of exclusively aluminum), but if you’re working with a mechanism that will have a lot of stress deliberately put onto it (ex. anti-tip pegs in Starstruck), steel may work better as it is stronger.
We personally used 100% aluminum on our robot and it worked very well. The one thing I would say though is for supports such as anti-tips as mentioned by @Mystellianne or support to hold towers up, I think it may be better to use steel. I’m not sure how torsion resistant the steel is as I have never paid attention to that till last year, but the aluminum got quite bent and twisted through holding up the towers.
Try and stay away from the 1x25 aluminum pieces. They are really soft and stretch much easier compared to the weight of the steel 1x25 pieces. They will tend to bend when you don’t want them to.
There is hidden wieght on your robot and it is the number of screws. Count the screws on your robots and place a number of equal sized ones in a pile and weigh them (plus the nylocks/keps). You will be amazed at how much weight that is as a percentage of the overall weight.
In addition, keep in mind cyclical loads. Below a certain threshold, you can load and unload steel an unlimited number of times. Aluminum does not have this threshold and will be subject to fatigue failure eventually regardless of the load. We snapped an aluminum c channel in two very early on in the year and ended up using several strips of 1x to reinforce the break point.
Google term would be Fatigue Limit if you want to know more.
Do you know what a sniper and an artist have in common?
What is a rainbow 6 siege quote doing here? LOL.
Back in skyrise my teams innovate award video was comparing aluminum and steel c channels, it includes usefull graphs that may help you understand the difference between the two.
Our pushbot had well over a pound of screws in it, screws and nuts definitely make ip a big part of the robot weight.
Our teams us aluminum exclusively except where strength matters. Team 7700B did an experimental test of C-Channels for skyrise and found steel to be about 30% stronger. See the you tube vid here: 7700B Innovate Award - YouTube
I on my team only use aluminum for all but MAYBE some of the crucial supports. as for the tensile strength or the overall load of aluminum i have no idea as vex (i presume) uses a different alloy of aluminum than most other companies. overall though aluminum seems to be the better building material for Vex.
I used one piece of steel on my final bot in Starstruck, because the metal that held fold-up standoffs for the claw kind of bent a lot.
Long story short, unless you are doing something intense, the strength difference is negligible.
We use these below for specific strength point in aluminum. That way you don’t need to use an entire steel channel.
gusset.tiff (188 KB)
Aluminum and steel have very different responses to repeated flexing. Aluminum will stress fracture long before steel fails. For some uses, this is important.
Ah, I just re-read the thread. @Robo_Eng_13 covers it well:
There is a lot to think about. For example, for the same weight, aluminum is stiffer than steel (and actually Douglas fir is stiffer than either metal). There is a great discussion of materials, written for the layman and not a materials scientist/engineer, in “The Nature of Boats” by Dave Gerr. It’s probably in your library.
Oh yeah. I have only a small collection of boat books, from my wooden boat dream days. But that one is there. Also nearby is my Tony Bingelis collection, which I bought years ago from Aircraft Spruce and Specialty. Here they are on Amazon: https://www.amazon.com/Books-Tony-Bingelis/s?ie=UTF8&page=1&rh=n%3A283155%2Cp_27%3ATony%20Bingelis
(subtext: “I’ll see your Dave Gerr and boats, and raise you Tony Bingelis and airplanes.”)
Both boats and airplanes are fun to think about and work on. Both cost too much in time and money. But hey, we’ve got robots now.