Machines B/C

[JoeyC]

For sensitive devices it should generally be fine; there's almost no way to achieve perfect static equilbrium, and there's a multitude of factors that could change the equilibrium (ex: if you're using wood and the humidity/temp increases).
For the most part, your margin of error won't change much (as long as it's already somewhat balanced), or, if you're competing at high enough levels, your device won't be that sensitive.
(also, changing the counterweights of a device will slightly change IMA in someway)

[xiangyu]

Hi all who see this; I have a rule question. Rule 3e. states, "Participants must not bring masses or include them in devices except when fixed in place prior to impound to obtain static equilibrium" I realize that this means counterweights must be fixed in place; however, what is the official definition of fixed in place? Does that mean IMPOSSIBLE to remove, or HARD to remove, or what? Because my counterweight isn't permanently there-it can be moved but takes a nominal-ish amount of force.

"Fixed in place" would mean to me that, by design, it does not move for the duration of the day of competition. You must not in any sense attempt to use it as adjustable. Somehting that is screwed together is "fixed in place" even though you can unscrew it. Something that is held in place only with a finger-tight screw clamp that you could easily adjust during the event is not fixed in place.

So if I put clay somewhere on my device that's not allowed? How might I "permanently" fix that weight to my device?

[Fallsbury]

Hi, I have been studying for Machines but my first competition that has Machines is at states (March), so I have been procrastinating to build my device lol. Can someone tell me what materials you would need to make a Div B lever? Like would you use wood/metal, what the fulcrum would be, etc. Thanks!

[FiveW's]

Hi, I have been studying for Machines but my first competition that has Machines is at states (March), so I have been procrastinating to build my device lol. Can someone tell me what materials you would need to make a Div B lever? Like would you use wood/metal, what the fulcrum would be, etc. Thanks!

All you really need is spare wood, zip ties, 80 cm stick/rod, and some type of hook. We used a meter stick cut down to 80 cm for lever arm. A wood block for elevation to put a hook. Then we put the hook in the wood so we could have a fulcrum. Overall as long as it is accurate which most will be at states its fine. Doing well on the lab is mainly about time.

[GurtYo]

Hi, I have been studying for Machines but my first competition that has Machines is at states (March), so I have been procrastinating to build my device lol. Can someone tell me what materials you would need to make a Div B lever? Like would you use wood/metal, what the fulcrum would be, etc. Thanks!

All you really need is spare wood, zip ties, 80 cm stick/rod, and some type of hook. We used a meter stick cut down to 80 cm for lever arm. A wood block for elevation to put a hook. Then we put the hook in the wood so we could have a fulcrum. Overall as long as it is accurate which most will be at states its fine. Doing well on the lab is mainly about time.

You can do it anyway you want. There are endless possibilities, but the most important part is effectiveness and accuracy, so test your device.

[Fallsbury]

Hi, I have been studying for Machines but my first competition that has Machines is at states (March), so I have been procrastinating to build my device lol. Can someone tell me what materials you would need to make a Div B lever? Like would you use wood/metal, what the fulcrum would be, etc. Thanks!

All you really need is spare wood, zip ties, 80 cm stick/rod, and some type of hook. We used a meter stick cut down to 80 cm for lever arm. A wood block for elevation to put a hook. Then we put the hook in the wood so we could have a fulcrum. Overall as long as it is accurate which most will be at states its fine. Doing well on the lab is mainly about time.

You can do it anyway you want. There are endless possibilities, but the most important part is effectiveness and accuracy, so test your device.

Ok thanks!

[CPScienceDude]

Is an average TS+R1+R2 score of 35 good? Or should I spend more time making my device more accurate? (I average around 25 sec to measure the ratios)

EDIT: Decided to just make it more accurate and now I'm averaging 43.7

[ZealousZebra447]

Hi all-
I am still kinda confused on the formula. My class 2 lever does not have an adjustable sliding mass while my class one lever does. What measurements and calculations would I make to do my ratio?

Also if my levers are connected with a clip, do I take that into account with the calculations?

Thank you so much!

[JoeyC]

Hi all-
I am still kinda confused on the formula. My class 2 lever does not have an adjustable sliding mass while my class one lever does. What measurements and calculations would I make to do my ratio?

Also if my levers are connected with a clip, do I take that into account with the calculations?

Thank you so much!

Given that there’s almost no way that a formula you draw on paper will apply to your actual machine (given that centroids will likely be slightly off and friction alongside many many other factors), instead of trying to solve for the formula with theoretical equations, just use data to make one.
You’ll need data for the testing charts anyways so might as well collect some and make a formula. Just take a lot of data points (assuming one mass is fixed and the other is not) then plot them in a linear regression.

[VansBuilders]

I built a prototype with a meter stick as the beam. Would this be a good material for the event as well, or will I need to use metal? From the rules, I understand the maximum weight the beam should bear is 800 grams. Will a wooden beam be fine for carrying this weight?