pic: Inverted CIM 2-Speed Gearbox

[JesseK]

I'm not crazy about the tiny idler gear - seems like it'd wear very quickly and as a result become a detriment to efficiency as the season went on. Is that the largest gear you can get for that initial stage?

Originally Posted by KrazyCarl92

School B:
-Low gear is intended for completing game objectives with a short sprint distance, and again some fine movement tasks.

More and more I find myself learning from the masters in School B for certain games. 2011/12 would more have a School A thought - the field was congested or blocked and objectives needed slow/meticulous movements. 2013/14 required much less precision in control (so long as the intake made up for margin of error) so School B would have dominated.

As a result
- School A needs the best high-traction treads available to maximise performance in the situations the design is made for.
- School B needs tread that WILL slip under enough torque so as to not trip the breakers. Colsons fit that spec nicely, imo.

[asid61]

Originally Posted by JesseK

As a result
- School A needs the best high-traction treads available to maximise performance in the situations the design is made for.
- School B needs tread that WILL slip under enough torque so as to not trip the breakers. Colsons fit that spec nicely, imo.

I've found colsons tend to be rather grippy if you're aiming for slippage under high traction. Something like sky wheels or the white KOP wheels would work better IMO.

[KohKohPuffs]

I'm not crazy about the tiny idler gear - seems like it'd wear very quickly and as a result become a detriment to efficiency as the season went on. Is that the largest gear you can get for that initial stage?

So the main purpose of the idler gear is to get the gear space in between the CIMs because the way the gearbox is designed. If we do end up doing idler gears, then we could just replace them with new ones if they ever wear down. On the other hand, the big gear is a 72T gear, so I might be able to replace it with an 84T and remove the idlers. However, I remember on another gearbox I was working with another person, we had trouble with the gear sizes with an 84T.

I plan on making another gearbox of a similar design, and perhaps take a look at Andymark dog gears, which come in smaller diameters, so hopefully that will eliminate the need for dog gears.

I've found colsons tend to be rather grippy if you're aiming for slippage under high traction. Something like sky wheels or the white KOP wheels would work better IMO.

I was thinking this gearbox to be one of those that goes decently fast on high gear, and slow for pushing matches on low (I guess this would be School A?). With that being said, I was considering the nitrile rubber treads that go on Andymark performance wheels.

Hopefully this is the right way to go if I'm going for a maneuverable and defensive bot?

[MichaelBick]

Originally Posted by KohKohPuffs

So the main purpose of the idler gear is to get the gear space in between the CIMs because the way the gearbox is designed. If we do end up doing idler gears, then we could just replace them with new ones if they ever wear down. On the other hand, the big gear is a 72T gear, so I might be able to replace it with an 84T and remove the idlers. However, I remember on another gearbox I was working with another person, we had trouble with the gear sizes with an 84T.

Switching to belts might be a good solution here. Plus, you'd get a nice efficiency boost.

[Ari423]

Originally Posted by asid61

I've found colsons tend to be rather grippy if you're aiming for slippage under high traction. Something like sky wheels or the white KOP wheels would work better IMO.

You know which wheels aren't too grippy and work really well for slippage? Lunacy wheels

[GeeTwo]

Originally Posted by Ari423

You know which wheels aren't too grippy and work really well for slippage? Lunacy wheels

If it weren't for the emoji, I'd have to report you for trolling. My right eye is twitching, even though I never heard of FRC until April or May of 2011.

[KrazyCarl92]

Originally Posted by Knufire

I thought 33 2013's robot used shifitng for improved acceleration with their autoshift code.

You may be right. You likely had more interaction with them that year than I did. The information from my post was what I remember from a conversation I had with one of their members at Championship when I asked how they arrived at their drive train gear ratios (they seemed odd to me, and I wanted to learn more).

I would not be surprised at all to hear that they incorporated autoshifting in 2013, given that they developed a 4-speed autoshifting drive train and code as far back as 2004. However, the logic for gear ratio selection for autoshifting would still probably be consistent with the thought of having good sprint distance for both floor pick up and cycling. Maybe someone from Killer Bees could fill us in with more details?

Originally Posted by JesseK

2013/14 required much less precision in control (so long as the intake made up for margin of error) so School B would have dominated.

Interesting...I would have classified 2014 into School A given the prevalence of defense and the fact that just about every team would be playing D at one point or another. That is to say, sustaining a pushing match for 15+ seconds would be more valuable than shaving a few tenths of a second off of a 10 foot sprint. But like we were saying before, depends on which criteria you're aiming to meet.

[JesseK]

Originally Posted by KrazyCarl92

Interesting...I would have classified 2014 into School A given the prevalence of defense and the fact that just about every team would be playing D at one point or another. That is to say, sustaining a pushing match for 15+ seconds would be more valuable than shaving a few tenths of a second off of a 10 foot sprint. But like we were saying before, depends on which criteria you're aiming to meet.

(Apologies, just noticed this comment)
It seemed to me that the better defense for 2014 was a 'pillaring' technique. Pillaring is a tank warfare term, where the tank drives back & forth perpendicular to the cannon's aim. It requires planning & setup, but it makes the tank much harder to hit while making it relatively easy for it to maintain sighting on a target. This is prevalent in the Battlefield series of games.

This same concept works for defense on the FRC field. Sprint into position, then pillar back/forth and force the other team to either push you sideways or drive fast enough around you to get to their goal. The likelyhood of them pushing you is high - yet it's time consuming and usually not as effective as one would thing since it still doesn't solve the problem of them getting to their desired spot for an open shot.

Faster low gear speeds on an open field also give more opportunities to clip/turn a corner of a shooting bot - much more effective than raw pushing.

[Chris is me]

Originally Posted by JesseK

(Apologies, just noticed this comment)
It seemed to me that the better defense for 2014 was a 'pillaring' technique. Pillaring is a tank warfare term, where the tank drives back & forth perpendicular to the cannon's aim. It requires planning & setup, but it makes the tank much harder to hit while making it relatively easy for it to maintain sighting on a target. This is prevalent in the Battlefield series of games.

This same concept works for defense on the FRC field. Sprint into position, then pillar back/forth and force the other team to either push you sideways or drive fast enough around you to get to their goal. The likelyhood of them pushing you is high - yet it's time consuming and usually not as effective as one would thing since it still doesn't solve the problem of them getting to their desired spot for an open shot.

Faster low gear speeds on an open field also give more opportunities to clip/turn a corner of a shooting bot - much more effective than raw pushing.

While this is a great defensive technique for many years, 2014 included, it was a better technique for years such as 2013, when one had to navigate the length of the field, around obstacles, and pushing a robot into a specific area was a liability.

In 2014, pushing was much less risky as there were no safe zones. T-bone pinning a robot had a bit more risk than "pillaring" but a lot more benefit - the robot is essentially immobile for the duration of the pin. I don't think "pillaring" was definitively better in 2014 just because of the T-bone pin and the relatively wide space to drive around. It is an important part of a defensive strategy but not the end-all.

[JesseK]

Originally Posted by Chris is me

While this is a great defensive technique for many years, 2014 included, it was a better technique for years such as 2013, when one had to navigate the length of the field, around obstacles, and pushing a robot into a specific area was a liability.

In 2014, pushing was much less risky as there were no safe zones. T-bone pinning a robot had a bit more risk than "pillaring" but a lot more benefit - the robot is essentially immobile for the duration of the pin. I don't think "pillaring" was definitively better in 2014 just because of the T-bone pin and the relatively wide space to drive around. It is an important part of a defensive strategy but not the end-all.

When determining where to set low gear when executing defense is a consideration, is an effective T-bone pin mutually exclusive of an effective pillar defense?

Do (e.g.) sailcloth bumpers change this consideration at all?

This plays into the original topic a bit - shaft spacing is usually determined by the gear availability and the desired difference between high gear and low gear (e.g. the dog gear choices). School A wants a larger gearing difference, School B wants a smaller gearing difference.

[Chris is me]

Originally Posted by JesseK

When determining where to set low gear when executing defense is a consideration, is an effective T-bone pin mutually exclusive of an effective pillar defense?

Not really.

Do (e.g.) sailcloth bumpers change this consideration at all?

Somewhat, particularly if you're using solid core pool noodles with sailcloth. In that case, your bumper doesn't deform or grip enough to effectively T-bone anyone (or be T-Boned, which is the point), so you can only really play pillar defense.

This plays into the original topic a bit - shaft spacing is usually determined by the gear availability and the desired difference between high gear and low gear (e.g. the dog gear choices). School A wants a larger gearing difference, School B wants a smaller gearing difference.

I don't really get school B. The advantage in short acceleration is usually so minor that it's not important, and I feel like using low gear for more precise movement is using hardware to solve a software / controls problem. While pushing matches should be avoided, low gear to me exists so offensive teams have the option to push through defense if necessary and defensive teams can themselves push all day long against the strongest drivetrains. So it doesn't get used all that much, but it's more of a safety net.

[MichaelBick]

Originally Posted by Chris is me

While pushing matches should be avoided, low gear to me exists so offensive teams have the option to push through defense if necessary and defensive teams can themselves push all day long against the strongest drivetrains. So it doesn't get used all that much, but it's more of a safety net.

In our experimentation with a "school A" drivetrain, we've actually found that we like to t-bone and play the "pillar defense" both in high gear. We found that teams can create separation from the t-bone when we are t-boning in low gear. When we are playing "pillar defense", high gear allows us to keep up with opposing robots to effectively block the field. We now teach drivers to only use low gear in head to head pushing matches.

[JesseK]

Originally Posted by MichaelBick

In our experimentation with a "school A" drivetrain, we've actually found that we like to t-bone and play the "pillar defense" both in high gear. We found that teams can create separation from the t-bone when we are t-boning in low gear. When we are playing "pillar defense", high gear allows us to keep up with opposing robots to effectively block the field. We now teach drivers to only use low gear in head to head pushing matches.

Mind giving traction details? I would expect that sufficiently high traction & gearing, in combination, would lead to popped breakers. I have no experience here myself, but I've read plenty of it on CD from 2014.

[MichaelBick]

Originally Posted by JesseK

Mind giving traction details? I would expect that sufficiently high traction & gearing, in combination, would lead to popped breakers. I have no experience here myself, but I've read plenty of it on CD from 2014.

The robot was geared for 20FPS @ 100% efficiency, had 4 CIMs and 2 550s, and had 2" wide roughtop traction wheels. The robot never stalled while t-boning, which probably helped in preventing blown breakers.

[EricH]

Originally Posted by GeeTwo

If it weren't for the emoji, I'd have to report you for trolling. My right eye is twitching, even though I never heard of FRC until April or May of 2011.

Actually, I'm not entirely sure what the CoF of a Lunacy wheel is on carpet. I'm pretty sure it's more than on that pesky Glassliner FRP (AKA regolith), though.


For those that don't get the reference... 2009 (Lunacy) was played on a field of Glassliner FRP with about a foot of carpet on all sides next to the rail. If you want to know what that looks/feels like, there's probably something similar in your nearest school/park restroom (as an anti-graffiti/easy-clean sort of measure). All robots were required to use certain wheels for their floor-contacting propulsion--the CoF between said wheels and the floor was something just under 1 as I recall, while your typical nitrile wheels are 1.something-or-other. Unlimited quantity... but that was the ONLY type allowed! Low-traction game, low-speed, low-friction...And then there were the trailers, but I'll end there.