Connecting two simple machines

smansman
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Connecting two simple machines

Post by smansman »

Someone submitted a question and the following FAQ was provided:
-----
Can there be a release of stored energy between the two simple machines in a transfer or does the output of the first simple machine have to directly drive the input of next one?

Yes, there can be a release of stored energy between the two simple machines in a transfer. No, the output of the first simple machine does not have to directly drive the input of next one.
-----
In parts of our machine, say from screw to inclined plane, we have other simple machines between the screw and the inclined plane in order to achieve the mechanical connection between the screw and the inclined plane. For example, our screw pushes something into a hanger which pivots, pulling on a string, and lifting the edge of a platform to release a mass which falls in the inclined plane.

We documented it as S->IP, but fully described what was happening.

This weekend, at our regional, we were advised by the judges (who were from a team participating in the regional) that the hanger is a lever and that the platform is a class 2 level. They said we needed to document this as:

S->L1
L1->L2
L2->IP

If we had documented it their way, they confirmed they would not allow it as a S->IP.

Essentially, they say (based on what they say they learned at the Wright State Invitational) that you can have anything you want between two simple machines as long as it isn't a simple machine itself.

These guys went so far as to document a mouse trap in their device as: X->L1 (the "sensor" is a 1st class lever), L1->L2 (the spring holder/release is a 2nd class lever), and L2->L3 (the killing part of the trap is a 3rd class lever). They didn't count for points, but they felt it needed to be fully documented this way.

Anyone have an opinion on that? It seems like they are really stretching.

In their machine, they had a ramp that they pulled a marble up > 10 cm. After that, there was another marble waiting near the top of the ramp, waiting to get hit, I suggested that under their rule interpretation that their machine was doing an IP->IP (first marble went up the inclined plane 10 cm, then hit another marble that went maybe 1 cm up the plane, pushed by the first, before falling off). They, of course, thought theirs was just fine.

Under this strict interpretation, I would suggest that a string passing through a screw eye and having its direction be redirected was going through a pulley. Same thing for the string passing over anything else like a nail. And if we can't use string going through screw eyes or other objects, I suspect that no one will have a machine.

I submitted two questions in this regard this morning, but know I'm unlikely to get a response prior to our state next month.

Thoughts?
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Re: Connecting two simple machines

Post by Uncle Fester »

First part, non-simple machines linking simple machines, is good. Only issue is it's easy to iadvertantly use something that's actually a simple machine.

Mousetrap explanation is wrong. Althoughh a mousetrap has three simple machines, it's one device (unless you happen to have BUILT the better mousetrap), and only one simple machine can be claimed per integral device. In Indiana, and anywhere people I've trained run events, you're allowed to claim whatever lever you want, but must describe and label it correctly -- no need to even mention the other two.

Haven't looked at the other stuff.
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Re: Connecting two simple machines

Post by smansman »

So is a screw eye with a string running through it a pulley? It's redirecting the string and allowing you to apply force in a different direction, just like a pulley. Pulley doesn't have to have a wheel, it's just there to reduce friction. Sure seems like a pulley to me. Therefore, no string going through screw eyes, or really anything, between your simple machines.

You could certainly create a compound pulley with IMA greater than 1 with screw eyes.

And it doesn't matter if it is just one screw eye, so IMA = 1. It would still be a simple machine, would have to be declared, and it would break the connection between two other simple machines. It just wouldn't count for points, since IMA not greater than one.

It's sort of a bottomless pit. Even the comments about allowing an integral component with a simple machine Are confusing. Who is to decide what is an integral component and what isn't? Frankly, that's how we approached our device, treating everything up to the end component as part of the component. How do you decide where the component ends? Does it have to be glued to something? Connected with string? We built individual components, each with an input on one end, and an output on the other. There are other simple machines built into them to facilitate the transfer. If they're part of each component, it sounds like you don't think they are an issue as long as we declare the final machine to be "The" simple machine in the assembly.
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Re: Connecting two simple machines

Post by smansman »

Anyone? Thoughts about a screw eye being a pulley?
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Re: Connecting two simple machines

Post by Uncle Fester »

I originally didn't answer because your very-ong-winded argument, dome without reading the rules, impressed me more as flame bait than an honest question. But, after being reminded about a NATIONAL tournament where someone ran afoul of this exact situation, I decided to answer. Be forwarned; you won't like my answer.

Can I use screw eyes instead of pulleys?

No. Because it's a screw eye. If a screw eye was a pulley, "screw eye" would be spelled p-u-l-l-e-y. "Pulley" was written in the rules, for the simple erason that "pulley" is the closest word that means "pulley" without misdirection. Look up "pulley diagrams" --- You can look at them all day via Google, and all you'll see are force diagrams with miles and circles; artistic diagrams that cover detail down to number of strands on each rope; photos of some reallly specialized systems designed for use on high-tech as well as simple sailboats; and never once will you see one drawn with screw eyes.

For the Love of all things Einsteinian, read the rules. Read them again. Look at what they ask you to do. Then do it -- don't go looking for excuses not to follow the rules. You don't get brownie points for trying to out-think event supervisors, you lose real points, which costs medals and higher-levl tournaments, and you won't get those points back by having a coach claim the event supervisor is being mean to kids "who worked so hard."

Also, rules aren't designed to teach the event; they're there to regulate it. LOOK UP simple machines. DO, really DO, some research. Surprise -- you won't see any srew eyes, you won't see force diagrams for downward-sloping inclined planes, you won't see Hot Wheels careening downhill, and you won't see levers that don't move (unlike at Indiana States last weekend). I'll bet some serious money that there's a reason for that.

Filing clarifications is a process that should be rarely done, and then, only done by your head coach, for the simple reason that, despite my usual annual complaints, the rule writers tend to know what they're doing. That odd wedge clause wasn't accidentally dropped in there -- I saw a team run afoul of it, and I instantly knew why the clause was put there. Clarifications is not a mechanism to get National people to hold your hand over every tiny detail and pre-approve all your points. At some point, you need to educate yourself, make some decisions, take a stand, build your device, and accept the points you earned. THis is a competition -- if you don't do this stuff, somebody else will, and they will beat you.
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Re: Connecting two simple machines

Post by SPP SciO »

With all due respect - I think the screw eye pulley question was legitimate and the discussion was helpful to our team. This is my first time coaching Mission, and I can attest to the difficulties of interpreting nuanced rules.

The original question concerned the incidental use of simple machines connecting the "scorable" simple machine transfers. In the description posted, it's easy to imagine the students not realizing the pivoting hanger counted as a lever and needed to be documented as such. It's not necessarily obvious - it's a hanger, not an l-e-v-e-r. So I interpreted the screw eye-as-pulley question not as an attempt at using them for points, but more of "if it acts like a pulley, does it need to be documented as a pulley" question. For what it's worth I recall reading that a sliding fastener, like on a book bag strap, is a pulley of sorts.

I agree that the scoreable transfers should be clear as day, with no need for any inventive interpretation. But in all machines, all those extra bits of connections that don't fit so neatly into textbook diagrams, they can be a source of confusion without firsthand explanation from experts.
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Re: Connecting two simple machines

Post by smansman »

Certainly not my intention to post flame-bait, and I've certainly read the rules many times. I've coached this event many times with great success. The screw eye as pulley was simply an example of how the rules could be misinterpreted.

I guess my real issue is that the rules say:

3d. The device must...execute a sequence of transfers from one Simple Machine to another Simply Machine.
3j. Other non-scorable tasks may be incorporated into the device but must contribute to the completion of the Final Task, receive no points and be listed on the TSL.
4c. Scorable transfers are of one Simple Machine Type to a different Simple Machine Type.
4e. Each scorable type of transfer must be unique.
FAQ. ...the output of the first simple machine does not have to directly drive the input of next one.

I'm trying to understand where it says that we can't incorporate other simple machines to help accomplish a transfer or where it says assemblies containing simple machines can be used to help accomplish a transfer.

Example: Screw to Inclined Plane. The screw hits a hanger which pushes a mass off of a ledge, falling to pull another mass up the IP. It was documented this way, and listed as S->IP. I agree hanger is a sideways class 1 lever, but we treat it as non-scorable task. We're still accomplishing the Screw to Inclined Plane transfer (4c). The screw doesn't directly drive the IP (ok per FAQ). We're not counting the screw to L1 or L1 to IP as scorable (ok per 3j).

Where in the rules does it say this couldn't be counted as Screw to IP?
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Re: Connecting two simple machines

Post by SPP SciO »

smansman wrote: Where in the rules does it say this couldn't be counted as Screw to IP?
I've been analyzing these rules pretty hard myself - so far there have been several instances where I've had to explain to my kids why their cool new idea isn't going to get the credit they anticipate.

My best interpretation is, it boils down to rule 3d, which gives the definition of a "Transfer" - it is, necessarily, one Simple Machine to another Simple Machine. So, in your example, the starting Simple Machine would be the screw. The very next Simple Machine in the sequence is the end of that transfer even if it's not getting points - the hanger is a lever, a Simple Machine, so that transfer has to be documented as Screw -> Lever. I think that if the rules were not written like this, it would be conceivable to have a device where every transfer involved springing a mousetrap, for instance, which would go against the spirit of Rube Goldberg-esque machines.

Like I said - I'm new at this - so if I've misinterpreted, please correct me.
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Re: Connecting two simple machines

Post by smansman »

In their FAQ, they actually wrote that you could release the energy from an energy storage device between the simple machines, and that the first simple machine didn't need to directly drive the second simple machine in their transfer. That suggests that a mousetrap between everything would be fine, and that other incidental simple machines would also be fine. We were told at our regional that we couldn't by a judge, but at the regional, they didn't count it against us. I submitted an official request, but they are very slow to respond, so I'm trying to start an outside conversation to see what others think.

If you had S->L1->IP, where the goal was to score S->IP, and the L1 is just helping with the transfer, I don't see anything that says you can't count it as S->IP. I would agree that you couldn't count the S->L1 and L1->IP if you want credit for the S->IP.
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Re: Connecting two simple machines

Post by Abdullah404 »

Could someone help clarify for me.

If I use a lever to raise a candle which burns the string which is holding a mass susspended. The mass falls on a wedge. Would that be LV1->Wedge
or LV1->Candle Candle-> Mass Mass-> Wedge

If you could help that would be grt!
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