The Spring

[CEF]

Originally Posted by Justin Ridley

We got our spring in as well. See link for video showing it is in fact "springy"

Seems like the pilots will need to be careful with how they lift the gears. A gear which is decidedly "on" the spring when the Pilot starts pulling could easily bounce off.

[Cothron Theiss]

Originally Posted by ahartnet

Our McMaster one came in today. I took it over to the Robonauts so we could do a direct comparison between the century one they got with identical specs to the mcmaster one as far as I can tell (https://www.mcmaster.com/#9664k68 vs http://www.centuryspring.com/extensi...ings-e-41.html) They behave very differently.

Foreground picture is the century one, background one is the mcmaster. Heading over to FIRST Q&A now to ask if they're only going to source the spring from McMaster. Aw man, just missed being the cheesy poof question: https://frc-qa.firstinspires.org/qa/255

Wow. That's really helpful to know. Though another thing to consider: While at the beginning of the season all the springs may behave like the McMaster spring, by the time champs rolls around, it may be an entirely different story. A Lift spring that has become damaged will hopefully be replaced. But a Lift spring that has become slightly stretched out and more likely to drop a Gear? We can be sure they'll still be in use.

[dardeshna]

We have a local spring manufacturer that offered to send us a couple for free... will post a video of our results when we get those to compare to century and mmc.

It looks like there are a few different ways to mount the spring (peg, something with screws, shaft collar?). Has anyone tested the shaft collar?

I remember reading that spring manufacturing tolerance is +/- 10% for the k value. Is there some math that determines how this affects the "bendiness" of a spring? How would one even measure the "bendiness" of a spring?

[ahartnet]

Originally Posted by dardeshna

We have a local spring manufacturer that offered to send us a couple for free... will post a video of our results when we get those to compare to century and mmc.

It looks like there are a few different ways to mount the spring (peg, something with screws, shaft collar?). Has anyone tested the shaft collar?

I remember reading that spring manufacturing tolerance is +/- 10% for the k value. Is there some math that determines how this affects the "bendiness" of a spring? How would one even measure the "bendiness" of a spring?

The field drawing specifically calls out a 1/4" long rod (like 0.625 OD or something) that the spring very snugly fits over. The tour video shows a shaft collar not called out in the drawings. I asked about the shaft collar in my question on frc q&a

Sent from my SM-G930T using Tapatalk

[GeeTwo]

Originally Posted by ahartnet

Our McMaster one came in today. I took it over to the Robonauts so we could do a direct comparison between the century one they got with identical specs to the mcmaster one as far as I can tell (https://www.mcmaster.com/#9664k68 vs http://www.centuryspring.com/extensi...ings-e-41.html) They behave very differently.

Foreground picture is the century one, background one is the mcmaster. Heading over to FIRST Q&A now to ask if they're only going to source the spring from McMaster. Aw man, just missed being the cheesy poof question: https://frc-qa.firstinspires.org/qa/255

Have you tested the "initial load" "Minimum Load" of these, or the spring constants? Those would shed some light on the different behavior.

[dardeshna]

Originally Posted by GeeTwo

Have you tested the "initial load" "Minimum Load" of these, or the spring constants? Those would shed some light on the different behavior.

The initial load of the mmc spring is almost 25lbs, while the century spring is only 22lbs (according to sites). That might be a significant factor when combined with manufacturing tolerances.

Also the century spring seems to be carbon steel, while the mmc one is spring-tempered steel. Not sure what the difference is really though.

[bhughesa]

Our spring that came in was much less stiff than we had assumed. I am not sure how far off from the true spring it is (got it locally, very similar but not identical dimensions).

But, as a practical example, our gear falls off very easily if it is not put down at the very back of the spring. Anyone see this behavior as well? Anyone have the real McMaster part and have practical examples of how to get the gear on without slipping?

[JR0405]

https://www.chiefdelphi.com/forums/s...d.php?t=153835

[Karthik]

I've merged a couple of threads on this topic.

[Dale]

Andymark has them in stock now.http://www.andymark.com/Spring-p/am-3557.htm

[Bkeeneykid]

Originally Posted by Dale

Andymark has them in stock now.http://www.andymark.com/Spring-p/am-3557.htm

Does anyone know if these are sourced from McMaster or somewhere else? It seems springs with supposedly same specs are significantly different. Being AndyMark, they'll probably be the ones on the AM fields for districts, so hopefully it's the same source as FIRST.

[cbale2000]

What I want to know is, if you drive into it and the tip of the spring hits one of the spokes of the gear, will it flex/deflect into one of the open spaces on the gear to allow for a successful hook or is it rigid enough that it acts like a solid dowel?



EDIT:

That merge really threw me off, I swear there was only one reply to the thread I posted in when I hit "Save".

[GeeTwo]

Originally Posted by Dale

Andymark has them in stock now.http://www.andymark.com/Spring-p/am-3557.htm

Emphasis mine

Originally Posted by AndyMark Site, page linked above

Product Overview:
This is a steel compression spring, similar to the one used in the 2017 game FIRST STEAMWORKS℠.

[ollien]

Originally Posted by GeeTwo

Emphasis mine

I'm sure that's simply to play CYA if the springs end up being different.

[Ari423]

Originally Posted by Bkeeneykid

Does anyone know if these are sourced from McMaster or somewhere else? It seems springs with supposedly same specs are significantly different. Being AndyMark, they'll probably be the ones on the AM fields for districts, so hopefully it's the same source as FIRST.

https://www.chiefdelphi.com/forums/s...6&postcount=53