FRC Blogged-Kit of Parts Drive System Option
 

http://www.usfirst.org/roboticsprogr...em-Option-2014

Interesting to see that the new kitbot is a sheetmetal structure.

Re: FRC Blogged-Kit of Parts Drive System Option
 

Interesting, I wonder if this is any indication on next years game.

Looks interesting though...

Re: FRC Blogged-Kit of Parts Drive System Option
 

Excited to see what the new kit frame looks like. Making superstructure attachment easier might make more teams want to stick to the kitbot.

Nice work AM!

Re: FRC Blogged-Kit of Parts Drive System Option
 

I'm guessing the standard 12.75:1 toughbox mini with 6" wheels. That's 10.9fps unloaded and 8.83fps with standard JVN loads.

I really do wish they would give a bit more information. I always like having a KOP drive to build so my team can be trained to help rookies. If I know it was simple enough to not need it I would rather have the voucher.

Giving a direct drive system to teams is very interesting.

Re: FRC Blogged-Kit of Parts Drive System Option
 

10.7:1 looks like the correct option.

Anyway, I'm interested to see a sheet metal chassis that is long or wide out of the box.

Re: FRC Blogged-Kit of Parts Drive System Option
 

Curious what they mean by this, as the KOP drive (ever since it's inception in 2005) has always been sheet metal :cool:

Re: FRC Blogged-Kit of Parts Drive System Option
 

I am actually really interested to see the new design of the kitbot.

To that end, I'm wondering what will be the pricepoint for the frame and such. Is the $450 the dollar equivalent of a new kitbot?

- Sunny G.

Re: FRC Blogged-Kit of Parts Drive System Option
 

I wonder if the direct driven wheel means we'll be getting a WCD kitbot this year. My gut tells me yes. I hope it's true, if not for the advantages of WCD then for the sheer coolness of it.

Re: FRC Blogged-Kit of Parts Drive System Option
 

I think even though it is a direct driven center, I think it will still be a dead axle system. I don't think FIRST would make the kit chassis not have an outer frame member because that outer member is very helpful for both mounting structure and mounting bumbers, and I dont think they want rookies having to worry about how to mount things without that outer member.

Re: FRC Blogged-Kit of Parts Drive System Option
 

I just hope it's revealed prior to October 3rd (or 17th at the very latest).

Re: FRC Blogged-Kit of Parts Drive System Option
 

Yeah, I'm wishing for this, but I don't think we're going to see it anytime soon.

The speculation about the game with be insane. At the very least, it would throw some hints about frame sizing and such.

- Sunny G.

Re: FRC Blogged-Kit of Parts Drive System Option
 

They could reveal it without giving away any frame size hints. For example, put it together at the largest dimensions the frame possibly can go (something like 30x30), so it's ridiculously oversized for our purposes. Then just include a small note that says something like "This shows the maximum for each dimension possible with the KoP frame. This does not reflect legal robot dimensions for the 2014 season." Just about anyone who has been around for any length of time will realize that you'll have to cut a few members shorter to fit into the legal dimensions, and which members are chosen will define if you have a wide or long bot.

Re: FRC Blogged-Kit of Parts Drive System Option
 

Most recent KOP frames have been marked with a small hole for the cut line to the smaller dimension. I would assume this one would have the same feature. Posting a picture to this community would lead to us probably figuring it out. The better question is why does anyone care about releasing frame size 3 months early. For about 8 years we knew frame size and it was never an issue.

Re: FRC Blogged-Kit of Parts Drive System Option
 

We always appreciate AM's efforts, and given the information provided, there is a very good chance we'll pick the chassis option over the PDV again. Getting a frame on day 1 where we don't have to do much fabrication and every part is aligned correctly is hard to pass up. Gates' belt system is also awesome. We have ran it through 7 competitions with no issues, and we will happily use it again.

A couple requests, if Andy/others are watching, which I'm sure you all have probably considered:
1) Making the length/width ratio a little less this year in the long configuration to improve turning
2) Making the drive shaft of the center wheel hex if possible, so interfacing a VEXPro transmission is easier and the system comes together without keys.

Re: FRC Blogged-Kit of Parts Drive System Option
 

I smell modular robot systems...
Easy attachment of "superstructures" means easy removal of superstructers.

Re: FRC Blogged-Kit of Parts Drive System Option
 

Not if you weld, epoxy, or shrink-fit them on :)

Re: FRC Blogged-Kit of Parts Drive System Option
 

I'm disappointed in the CD community. This was the first game hint. We now know that the robot rules will allow rectangular framed robots that needn't be square. Surely someone can take that information along with choices of phrasing in the blog post and make logical inferences to conclude that this year is a water game.

Re: FRC Blogged-Kit of Parts Drive System Option
 

Probably the reason for more sheet metal and extrusion instead of the c-channel is because it's now going to be easier to waterproof; instead of the old, obsolete, leaky c-channel system.

I also do want to see it before we have to make a decision. Since our machining capabilities are still uncertain, it would be nice to know what the drive was and how customizable it is, before deciding either way (I just want to put colsons and 6 cim gearboxes on it :D )

Re: FRC Blogged-Kit of Parts Drive System Option
 

If it ain't broke, don't fix it.

Re: FRC Blogged-Kit of Parts Drive System Option
 

The previous kitbot frame had been referred to as being made from "c channel" as opposed to "sheet metal" like the upcoming one. Based on that, we know that things beginning with the letter c ("c channel," "carpet") are out and five letter words ("sheet," "metal," "water") are in.

Bam, water game.

Re: FRC Blogged-Kit of Parts Drive System Option
 

The KOP drive so far has been extruded aluminum C-channel, not sheet metal.

I have a feeling this new drivetrain is going to look eerily similar to the VexPro DIAD Chassis

Re: FRC Blogged-Kit of Parts Drive System Option
 

Actually, Adam is correct. It is bent 5052-H32 sheet metal. Not extruded. The corner connectors are the extruded parts.

Re: FRC Blogged-Kit of Parts Drive System Option
 

Really? Interesting, I'll have to take a closer look at that C-channel next time I'm at the buildsite.

Re: FRC Blogged-Kit of Parts Drive System Option
 

Great to hear that the kit bot is getting an upgrade - I'm very curious to see what it looks like. Hopefully it's possible to put in 2 speed gearboxes with slight modifications.

I like the C-Base frame (we've used it in some fashion for 3 straight years). But I'm excited to see improvements. In my opinion, the biggest drawbacks of C-Base are as follows:
1) Not setup for direct drive
2) Track width not maximized: wheel treads are at best about 2" from the outside of the frame perimeter
3) Limited electronics room: belly pan area too narrow / wheel channels too wide

It's fantastic to hear that this is a direct drive ready frame. On items 2 and 3, I think there's a decent chance we'll see a bit of an improvement with Corner Connect presumably going away. If wheels can be 0.5" closer to the outsides and wheel channels can be 1" narrower, I'll be a pretty happy guy.

Re: FRC Blogged-Kit of Parts Drive System Option
 

For students with inquiring minds...

In the spreadsheet, the 8.83 number is calculated directly from the 10.9 number by multiplying by a "Speed Loss Constant" (default is 81%).

This constant is not computed within the spreadsheet from user-entered info about physical loads and motive forces in the drivetrain: you get the same 8.83 answer from the spreadsheet if you change the number of motors, stall torque of motors, the mass of the robot, or gearbox/drivetrain friction.

The best way to determine what value you should use for the "Speed Loss Constant" for your drivetrain is to build the drivetrain and measure its top speed, then divide that by the theoretical unloaded speed.

Re: FRC Blogged-Kit of Parts Drive System Option
 

Perhaps they wanted to make it easier to attach superstructures because this year's superstructures will need a lot of structural support to do some heavy lifting? I'm calling stacking game.

Re: FRC Blogged-Kit of Parts Drive System Option
 

Wild speculations about what this means about the game.

First big assumption: You can build a competitive robot using the KOP chassis as designed.
Second implied assumption 6 in wheels based on stated speed.
Third implied assumption direct drive places the gear box center line on the wheel.

So with a 3" high nano box & 6" wheels, you have 1.5" ground clearance at the center of the robot. 8" wheels give you 2.5" of ground clearance in the center of the robot.

Leads to Big assumption based on this is no big obstacles the robot has to go over.

Wheels & stated speed also implies no water game. Again. Sorry guys.

One limitation of a direct drive box is the difficulty of changing ratios.

Re: FRC Blogged-Kit of Parts Drive System Option
 

If you look on Andymark's web site, you find the drawing it is made from.

So it is true that it is made from sheet stock. In modeling terms & usage I think of them as more of a shape though.

In a previous lifetime I use to have I beams occasionally made from plate metal. Once they were made, people called I beams & would look at you funny if you called them plate.

Re: FRC Blogged-Kit of Parts Drive System Option
 

It could be 6" wheels with 12.76:1 gearing or maybe 4" wheels with the 8.46:1 gearing option.

If it's 6" wheels, the gearbox options give the options of switching to 13 ft/s or 16 ft/s, at least.

It's too bad Toughboxes aren't setup with a 50:12 initial stage instead of 50:14. Then we'd also have the option of switching the first stage to 50:11 or 48:14 for a bunch more options.

Re: FRC Blogged-Kit of Parts Drive System Option
 

Use velcro. Bam, removable. :rolleyes:

Re: FRC Blogged-Kit of Parts Drive System Option
 

Maybe AM made it easier to attach super structures because teams typically need to attach super structures? Nothing can be implied with these kit frame details other than the robots will most likely be allowed to have wheels.

We loved the kit frame last year, it's great to see some improvements are being implemented. I'm hoping the transmissions are easier to get into than they were on the previous iteration, that's what gave us the biggest setbacks.

Re: FRC Blogged-Kit of Parts Drive System Option
 

but...but...reality without wild suppositions is so much less convivial! ;)

This is silly. Obviously, the point is that all robots will have to be both long- and wide- simultaneously. In fact, they'll have to be entirely symmetrical, because we're landing on the field like this* [/sarcastic wild supposition]


*Mars Pathfinder 40g "bounce" landing, if you don't want to click.

Re: FRC Blogged-Kit of Parts Drive System Option
 

If its 6" wheels, with the 10.71:1 ratio configuration, JVN's calculator drops out 10.51fps as the max speed.

Re: FRC Blogged-Kit of Parts Drive System Option
 

How do you know what "Speed Loss Constant" to use?

Re: FRC Blogged-Kit of Parts Drive System Option
 

I don't. I just assumed the 81% isn't wildly out to lunch. I'm also guessing that HQ/AM in saying "10.5fps" did some kind of calculation using commonly available tools -- likely JVN's calculator.

Re: FRC Blogged-Kit of Parts Drive System Option
 

Does anyone know where the 81% number came from?

Re: FRC Blogged-Kit of Parts Drive System Option
 

Two stages of gearing, each 90% efficient -- .90 * .90 = .81

Re: FRC Blogged-Kit of Parts Drive System Option
 

Are you sure that's not just a coincidence?

The "Speed Loss Constant" in cell I5 is independent of the gearing in cells C12 thru D15, or the Drivetrain Efficiency in cell J5.

.

Re: FRC Blogged-Kit of Parts Drive System Option
 

Looking at the blog again, I see that they're calling that an "estimated final drive speed," so I shouldn't have been looking at maximum theoretical speeds.

As an extra piece of information, last year they said this about the 2013 kit drive:
That drive had a 42:39 timing belt reduction, so the ratio was 11.53:1. If they used the 0.81 factor last year, they'd get around 9.75 ft/s, which they might have rounded up to 10 ft/s. Based on that I'd agree that they're very likely doing 6" wheels with 10.71:1 gearboxes. If not, they're estimating the speed differently this year.

Re: FRC Blogged-Kit of Parts Drive System Option
 

Also worth noting: in the real world, the % of "speed loss" is not constant when changing gear ratios either:

Team 1678 did some testing earlier this year on a bot with a 2-speed gearbox. The "Speed Loss Constant" was 92% in low gear and 72% in high gear.

Re: FRC Blogged-Kit of Parts Drive System Option
 

Ether is correct on most accounts. Keep in mind that JVN's "speed loss constant" comes after a "drivetrain efficiency" (i.e. losses from gearing), therefore the 81% number cannot be attributed to gearbox losses. The testing we did earlier this year found the overall speed loss from the theoretical free speed of the motors. The numbers we found make intuitive sense, given that motor resistance, friction, rolling resistance, and air drag all tend to increase as speed increases.

My conclusion now is the same as it was then: test your drivetrain instead of blowing smoke from your behind about the theoretical speed you think you'll get.

Re: FRC Blogged-Kit of Parts Drive System Option
 

The Speed Loss Constant does not come "after" the drivetrain efficiency (at least not in the 2013 version). It is completely independent. See below:

^^This is exactly what the "Speed Loss Constant" in the JVN spreadsheet is.


I love test data too.

But I still think it may be possible to develop a physics-based model that will reasonably predict overall drivetrain performance -- including not only top speed but also time to reach a desired speed, time to reach a desired distance, and accel, speed, distance, motor amps, motor volts, and Coulomb consumption versus time -- based on a priori estimates of a limited number of parameters .

Re: FRC Blogged-Kit of Parts Drive System Option
 

What if the water is only 1" deep?

Re: FRC Blogged-Kit of Parts Drive System Option
 

Then that drastically reduces the coefficient of friction between the wheels and the playing surface, reducing the robot's ability to accelerate to the maximum drive speed, and possibly making it impossible to accelerate to 10 ft/s within the length of the playing field. However, they never said that the robot would be able to achieve that speed on the field. That was just the estimated speed. ::rtm::

Re: FRC Blogged-Kit of Parts Drive System Option
 

I'm hoping that the dimensions are increased this year. The dimensions last year severely limited what teams could design (although it meant less clutter on the field). The fact that they somehow fit 6 wheels in a wide configuration makes me hopeful the dimensions are increased this year.

Has anyone tried modifying last year's wide 4-wheel KOP drive base in a 6 wheel base, keeping the same dimensions? This could answer the question of dimensions; if it's unfeasible or useless, then chances are that the dimensions could have been increased for next year.

Re: FRC Blogged-Kit of Parts Drive System Option
 

Just some ideas.

"Belt drive robot" - "direct driven center wheel"

Unless andymark has aquired new belts, there are currently only two sizes. The 20.47in belts are not large enough to accommodate 6in wheels or larger(and I imagine they might be using their new 6in HiGrip anyway). Because it is a direct driven center wheel, the outside wheels are the pulley center distance away from the middle wheel(minus the 1/8in center drop). Inferring we are using the current pulleys and the 31.5in belts, the center distance is about 11.5in.

Soooooooooooooo
(11.5in * 2) + (3in(HiGrip radius) * 2)
= 29in

Possibility the new drive train is at least 29 inches in length.

Re: FRC Blogged-Kit of Parts Drive System Option
 

Will it be possible for teams to buy a second kitbot for a practice robot?

Re: FRC Blogged-Kit of Parts Drive System Option
 

Historically, its been available from AndyMark after kickoff.

Re: FRC Blogged-Kit of Parts Drive System Option
 

Andymark usually puts the kitbot on sale sometime within the first week after kickoff

Re: FRC Blogged-Kit of Parts Drive System Option
 

I wish we had more information to base our decision off of. I'm generally not a fan of the kitbot, but if it has some new improvements, it would be a great option.

Re: FRC Blogged-Kit of Parts Drive System Option
 

I liked the new dimensions. The new limitations were really cool and forced kids and mentors to think harder and iterate more. It also made transportation easier, made more room on the field, and I felt it made everything a bit more fun.

I hope the new dimensions stay.

Re: FRC Blogged-Kit of Parts Drive System Option
 

Agreed. Seeing the little robots beside the 2012 and earlier robots really showed me how inefficient teams were with their space.

Re: FRC Blogged-Kit of Parts Drive System Option
 

If I remember correctly, I once read a really, really old CD thread that said 81% was determined by taking one of 229's drive bases, running it to top speed, and measuring that speed. Ratio of that top speed to actual speed became the default "speed loss constant". I'm sure this number is somewhat correlated with efficiency, wheel size, tread type, etc etc. For most practical purposes it's "good enough".

Efficiency in JVN's calculator is used to calculate motor loading, not speed.

Re: FRC Blogged-Kit of Parts Drive System Option
 

I seem to recall reading that somewhere too, but I wasn't sure.

It's a lot more than "somewhat". In the real world, the top-speed to theoretical-speed ratio is correlated with playing surface, wheel type (e.g. pneumatic or solid) and tread type, chain vs belt, chain or belt tension, wheel alignment, wheel runout, torque-dependent friction in the gearbox and drivetrain, and speed-dependent friction factors such as large airfoils.

It's quite useful as a rule of thumb. Whether or not it's good enough depends on what you're using it for. Students need to understand the limitations.

That is true. In a physics-based model, the torque-dependent friction (gearbox "efficiency") would affect top speed.