pic: 971 Friction Clutch Transmission Insides

[Travis Schuh]

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[Answer42]

This is a really cool approach to take for shifting. What method are you using to transmit force from the cylinder to the clutch mechanism? Roll pin maybe?

[s_forbes]

Neat!

It looks like with a drum on each second stage gear, that you would need air pressure to engage either gear set, regardless if it is low or high gear, is that correct? Seems like a big plus to that is you can shut off your air pressure after a match and the robot would roll freely with no motors engaged.

Based on the results of this off season project, do you see enough benefits to use this approach (instead of dog shifting) if the game requires a two speed drivetrain this year?

[Travis Schuh]

Originally Posted by s_forbes

Neat!

It looks like with a drum on each second stage gear, that you would need air pressure to engage either gear set, regardless if it is low or high gear, is that correct? Seems like a big plus to that is you can shut off your air pressure after a match and the robot would roll freely with no motors engaged.

You are correct that you need pressure to engage the gear sets and our initial thinking was exactly along the same lines as you outline, however we found that this didn't turn out to be the case. When you drain the pressure on the robot, the transmission stayes engaged in gear to the point where the motors spin as you push it and it wasn't possible to dis-engage it by hand. We took appart one of the transmissions to check wear, and found that the shoes were wedged into the drum pretty well. We are not sure of the exact mechanism of this or how strong the engagement is, as we got everything together at the last minute and have been so busy with other projects since that we haven't gotten a chance to dig into this further. The nice thing about the linkage approach rather than say a taper lock is that whatever lock we have dissengages pretty smoothly because the shoes pull away from the face as you pull on the selector.

-Travis

[BBray_T1296]

Originally Posted by s_forbes

Based on the results of this off season project, do you see enough benefits to use this approach (instead of dog shifting) if the game requires a two speed drivetrain this year?

Is there any particular need to have a 2 speed propeller? Huehuehue

This is really cool, and a unique/very-untraditional way of shifting in FRC

[DampRobot]

Originally Posted by Answer42

This is a really cool approach to take for shifting. What method are you using to transmit force from the cylinder to the clutch mechanism? Roll pin maybe?

A roll pin connects the triangular central piece of the shifting mechanism to the shift shaft (that tiny one you can see in the photo). It went through the output hex shaft through a clearance slot, which isn't shown in the photo. (EDIT: I've been told that it was a dowel pin, rather than a roll pin, which is stronger.)

I hope that this doesn't get lost in the game hint chatter. This really is a huge technological leap, and a great experiment, similar to how a ball shifter was a few years ago. It's just a pity it took 3 weeks to machine. If it didn't, I'm sure 971 would be rocking it next year. I have to hand it to Travis, Austin, Brian, and co for pulling off such a innovative, different and cool idea.

[T^2]

Originally Posted by DampRobot

This really is a huge technological leap

I don't understand this viewpoint. Yes, it's cool, but it feels like a solution in search of a problem.

Originally Posted by DampRobot

3 weeks to machine

I'm getting nightmare flashbacks to last season...

[AdamHeard]

Originally Posted by T^2

I don't understand this viewpoint. Yes, it's cool, but it feels like a solution in search of a problem.

This is half my opinion and half my recollection of conversations with Austin, so please don't hold Austin accountable for my statements.

They had a clear problem they wanted to solve. An effectively utilized autoshift function with properly picked low/high ratios could potentially shave seconds off each match (4-10 maybe?). This time saved isn't huge, but could amount to a 5-15% increase in scoring each season.

Both the dog and ball shifter do not shift instantly, and neither does this clutch method.However the clutch method does shift faster than the previous two, and with a smoother engagement; this better blends with their goal of smooth autoshifting.

You can debate whether or not their overall goal is valid or cost effective, but please don't say that it's a solution in search of a problem. Valid analysis and engineering went into this, and it wasn't created for the sake of coolness.

[T^2]

Originally Posted by AdamHeard

This is half my opinion and half my recollection of conversations with Austin, so please don't hold Austin accountable for my statements.

They had a clear problem they wanted to solve. An effectively utilized autoshift function with properly picked low/high ratios could potentially shave seconds off each match (4-10 maybe?). This time saved isn't huge, but could amount to a 5-15% increase in scoring each season.

Both the dog and ball shifter do not shift instantly, and neither does this clutch method.However the clutch method does shift faster than the previous two, and with a smoother engagement; this better blends with their goal of smooth autoshifting.

You can debate whether or not their overall goal is valid or cost effective, but please don't say that it's a solution in search of a problem. Valid analysis and engineering went into this, and it wasn't created for the sake of coolness.

I can see why taking seconds off of operation time would be helpful, and I concede that I shouldn't judge the necessity of this mechanism without knowing the design process behind it.

I wonder, though, if time wouldn't be better spent on low-hanging fruit -- some mentors and I made a lively discussion of this a few months ago when talking about how 1678 could improve our competitiveness. I know 971's bots always have high score ceilings, but often fail to execute to full potential. Would not it be more efficient to ensure basic functionality in each match, as opposed to some fantastic and some mediocre matches, rather than build a smoother autoshifter? (This isn't to say that both of these improvements couldn't happen simultaneously, of course.)

Perhaps someone from 971 could chime in here.

Originally Posted by Brandon Holley

Also keep in mind that you do not necessarily need to optimize-for-efficiency every single action your team takes.

My mistake. I usually take just this approach.

[Michael Corsetto]

Originally Posted by T^2

I can see why taking seconds off of operation time would be helpful, and I concede that I shouldn't judge the necessity of this mechanism without knowing the design process behind it.

I wonder, though, if time wouldn't be better spent on low-hanging fruit -- some mentors and I made a lively discussion of this a few months ago when talking about how 1678 could improve our competitiveness. I know 971's bots always have high score ceilings, but often fail to execute to full potential. Would not it be more efficient to ensure basic functionality in each match, as opposed to some fantastic and some mediocre matches, rather than build a smoother autoshifter? (This isn't to say that both of these improvements couldn't happen simultaneously, of course.)

Perhaps someone from 971 could chime in here.

I'm not on 971 (actually on your team T^2 ), but you can't make these assumptions without any understanding of team structure, goals, etc. I just spent the last 5 hours at 971's shop, I can assure you that developing a friction clutch transmission is certainly NOT the only thing 971 is doing this off-season. Arguably, they've made larger strides this fall than we have.

You know what happens when you assume...

-Mike

[Nuttyman54]

Originally Posted by T^2

I wonder, though, if time wouldn't be better spent on low-hanging fruit -- some mentors and I made a lively discussion of this a few months ago when talking about how 1678 could improve our competitiveness. I know 971's bots always have high score ceilings, but often fail to execute to full potential. Would not it be more efficient to ensure basic functionality in each match, as opposed to some fantastic and some mediocre matches, rather than build a smoother autoshifter? (This isn't to say that both of these improvements couldn't happen simultaneously, of course.)

Perhaps someone from 971 could chime in here.

We are working on that too, but a lot of that is very game specific, so it's hard to address with specific projects in the off-season. We've had a very detailed discussion of the robot issues last year and how to avoid them again. I will also say that there has been a conscious choice during build to go for riskier designs with higher potential the past few seasons.

This was one of several off-season projects, one of the others being a 3rd robot, HP-load only for Ultimate Ascent that we ran at Madtown. That was designed and built almost entirely by freshman and sophomores, with some help from the upperclassmen. The friction clutch is a lot cooler, and I don't know of anyone else in FRC who has tried to make one as a replacement for the dog shifter, so we thought it would be more interesting to CD.

[T^2]

Originally Posted by Nuttyman54

we thought it would be more interesting to CD.

It is. Could we get a picture of both halves assembled together?

[Travis Schuh]

Originally Posted by T^2

It is. Could we get a picture of both halves assembled together?

Try http://www.chiefdelphi.com/media/photos/39233?

This is the closest we have of what you are asking. You can see the large gear and steel drum that is in this picture, and then the opposing steel drum and smaller gear. Unfortunately all of the inner workings get hidden once you assemble it.

-Travis

[Michael Hill]

Pretty cool, I've been thinking about how to implement a clutch transmission for a few months now. Pretty awesome to see. Nice job!

[Brandon Holley]

Originally Posted by T^2

I don't understand this viewpoint. Yes, it's cool, but it feels like a solution in search of a problem.

And I don't understand this viewpoint....

Originally Posted by AdamHeard

You can debate whether or not their overall goal is valid or cost effective, but please don't say that it's a solution in search of a problem. Valid analysis and engineering went into this, and it wasn't created for the sake of coolness.

...but it is EXTREMELY cool.

If you are unsure as to the exact purpose of someone's particular project (one that they've more than likely poured a tremendous amount of blood, sweat, tears and money into)- there are a number of different ways to approach that viewpoint that will not cutdown someone else's hard effort.

Possibly begin a dialogue centering around why shortening shifting time is important to 971...



Also keep in mind that you do not necessarily need to optimize-for-efficiency every single action your team takes. Sometimes doing something the hard way, or doing something new, or even something for the sake of coolness can be a great exercise in teamwork and inspiration...


Travis, Austin and co., a job very well done. This is a really cool little clutch. Are you guys feeling good about trying to implement it this upcoming season? (Assuming shifting makes sense for the game).

-Brando