Motors - another concept for FRC

[Lil' Lavery]

Originally Posted by JVN

If you could have a CIM instead would you really use a FP?
To me that is a NO brainer.

Unless I'm building a high-speed, low-torque, application with a low chance of stalling the motor (say, a "shooting wheel" as used in 2006 and 2009 by many teams), I definitely agree with JVN. CIMs are simply much more reliable and a better fit for most FRC applications than a FP.

Also, I <3 globes. My favorite motor in the kit for non-drive applications, without a doubt.

[ChuckDickerson]

Let’s face it, just about everything on an FRC robot is driven by either a motor or a pneumatic solenoid. OK, so there are some uses for springs and servos and such but the bulk of everything that FRC robots “do” are ultimately actuated by either a motor or a pneumatic solenoid. I welcomed the changes this past year in opening up the choices we had for pneumatic solenoids. I think FIRST is on the right track. Now maybe it is time to look at the motors.

Many teams, especially rookies, don’t have the resources (tooling, experience, funds, whatever) to develop custom gearboxes. The FP motors are a fairly standard 550 style “can” motor thus there are several off the shelf options for gearboxes that will turn the high speed, low torque FP motors into something with a more usable speed and torque output and just as importantly something with a more reasonable output shaft format such as a ½” keyed shaft (or whatever). Likewise, the CIM motors have several COTS gearbox options from companies like AndyMark and BaneBots. We even get usable CIM motor gearboxes in the KoP. That’s why the majority of teams, again especially rookies, use the CIM motors and the KoP “CIM gearbox of the year” (aside from the BaneBots planetary debacle of 2007).

Yes, we get a bunch of other odd ball motors in the KoP but most of them have such funky output shafts that they are just a royal PITA to use. Heck, most of the time we don’t get the special electrical connectors required to even use some of the window motors and such so we end up hacking some kind of unreliable soldered up connection. The Globe motor is sort of in between and isn’t too bad to deal with. We can talk all we want about optimal torque curves and choosing the most efficient motor for the job, etc. but when it comes down to it a lot of teams look at the pile of motors they are given to work with and say “these are ones we can do something with given our resources so lets design around these” and “all these other funky ones are kind of useless to us even if they would be great for an arm or wharever we can't make anything that uses that wierd output”.

There is a reason AndyMark and BaneBots sell such nice options for gearboxes for the FP (and other 500/550 style can motors) and for the CIM motors and not the window motors, etc. The FP/CIMs are a known quantity. The COTS gearboxes adapt the speed and torque of a FP/CIM to something more reasonable and just as importantly something we can easily stick a hub and sprocket or pulley or wheel or whatever on. If you are a team with a drill press and a miter saw it can be quite difficult to make something that reliably uses some of the other odd ball motor outputs. That is one reason I feel the designs are being too limited by the motors we are given to use. If more/all of the motors in the KoP had more standard/common/usable output interfaces like say a ½” keyed shaft (or whatever) then there would be many more off the shelf options as far as gears, sprockets, etc. that teams with limited resources could just acquire and use. Then many of the limitations on robot designs and capabilities would be reduced and the whole level of play would be raised.

I know a lot of the motors with the funky outputs like the window motors, van-door motors, etc. are probably donated automotive industry surplus and that’s fine. If FIRST gets them for free or real cheap then by all means throw them in the KoP. But if we all get 10-12 motors each year but only half of them are really usable by a large number of teams then designs and capabilities are being limited for a lot of those teams when compared to the teams that do have the resources to use more of the odd ball motors. In effect some teams get 10-12 motors in their kit while others get 4-6. For these reasons I would love to somehow see more options to use some kind of motors/gearboxes with outputs that are a bit easier to work with for ALL teams.

[Brandon Holley]

Originally Posted by EricH

John: The CIM weighs a lot more. That might be enough to put an FP in where a CIM could go. Just one of those accursed design tradeoffs that come with any design problem. And yes, I might use an FP instead of a CIM even if I could use a CIM. It depends on the application.

Did you account for the weight you are going to add to get the FP motor to an equivalent spec of a CIM motor? Unless your application requires ~15000 rpm at w/e the output torque of the FP is theres going to be some weight gain there.

Sure there will be weight for the CIM too because not too many applications are goign to use the CIM at a free speed of ~5000 rpm, but to simply get the FP to be similar in speed and torque as a CIM it will require a signifigant amt. of weight.

I agree with JVN on this one, given the choice of FP or CIM I would go CIM everytime, regardless of any kind of weight gain. The reliability factor alone is worth it.

Brando

[EricH]

As I recall, the last time 330 smoked an FP was when we had the 6V ones given in the KOP instead of the 12V ones, if then. The time before then was deliberate... Reliability, if the system is designed right, is just as good as with a CIM.

Sure, you need a gearbox with an FP. A CIM is about 3 pounds, IIRC, and an FP is about one pound. If your gearbox (say, an AM or BB planetary) is less than 2 pounds, you're lighter for close to equivalent functionality.

[Bob Steele]

If we want to open up some of these choices we already have the materials in previous KOPs...

By limiting the power to one battery.... and also limiting the output to a single 100 amp breaker.... we could limit power.... (we already do this....)

We could also say... any motor... BUT you are only allowed
4 motors on 40 Amp breakers,, 4 motors on 30 Amp breakers and 4 motors on 20 Amp breakers but not to exceed 10 motors...

This along with the weight limit for the entire robot would really limit what a robot could do....and level the playing field

Judicious use of the power that you have would be necessary... (not unlike what we have to do now....)

I think that this would lead to a very interesting engineering experience involving the actual calculation of power loads and drains...

Many of the teams already do this but it would be much more real world.

I also really like the idea of giving three motors...CIM,FP, GLOBE in unlimited quantities but with the above restrictions on power use.

If a team chose to use 10 CIMS they would have some serious issues with Power consumption to deal with... (not to mention weight..)

Interesting proposal....

[Richard Wallace]

Richard's first rule of motor selection: you pay for torque.

How you pay varies somewhat by application. It might be money, weight, space claim, service life, etc.; or combinations that include some or all of these 'costs'.

Richard's second rule: choose a motor that can take the heat.

How much heat must your motor take? Make sure you are confident of the answer to that question as early in the design process as you can, hopefully before your preliminary choice becomes so entrenched that changing it will be a major upset (or worse).

Quite often, FRC robot designers (and designers of many other things) don't really find out how much heat that is until they encounter a rare (but usually forseeable) overload. Think about how someone could overload your system.

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Back to the OP's main topic: As a motor designer I'd love to see more varieties of my favorite technology showcased; however, as a FIRST mentor and volunteer, I know that limiting motor selection to a short list is consistent with the system-thinking emphasis and tight schedule constraints that make FRC an inspirational challenge.

[ajlapp]

A very smart man once said...

Battery, Maximum Weight, Maximum Size... no other restrictions.

Spoken like a true genius.

FIRST spends a lot of time finding all of these types of items for the kits......open up the rules and put the burden on the teams!

[DonRotolo]

Originally Posted by Bharat Nain

We are given the names of 7 (arbitrary number) motors legal for an FRC competition. We are allowed to use as many of each type of motor as long as the total number of motors is less than 10 (again, arbitrary number).

Originally Posted by Andrew Schreiber

Akash, the reason this isn't practical is because we simply don't have the TIME to research the optimum component for each aspect of the game. By constraining us to 10 motors the GDC is restricting our decision to help us, instead of choosing from hundreds of motors we can only choose from 10.

No worries about picking from hundreds - you must pick from seven, explicitly specified.

One issue is that many of the motors we are given are not available in huge quantities on the open market. If every team decided to use 5 of the LH window motors, I think the Earth would be hard-pressed to supply them.

One alternative would be to supply some motors, and give teams the option that they can use "x quantity of these other, not-supplied motors if you want".

On a related topic: I sure would like to see an off-the-shelf linear actuator (like those used to turn satellite dishes) become available. Slow but powerful.

[IKE]

Originally Posted by JVN

Battery, Maximum Weight, Maximum Size... no other restrictions.

-John

Battery, Breaker, Max Weight, Max Size.

[NickE]

I like the idea that teams can use as many of each type of KoP motor as they want, as long as its under a certain number. If you wanted to limit it even more, you could put a limit on the total power (wattage) that all the motors together might be less than.

[Collin Fultz]

Originally Posted by Brandon Holley

Did you account for the weight you are going to add to get the FP motor to an equivalent spec of a CIM motor? Unless your application requires ~15000 rpm at w/e the output torque of the FP is theres going to be some weight gain there.

Sure there will be weight for the CIM too because not too many applications are goign to use the CIM at a free speed of ~5000 rpm, but to simply get the FP to be similar in speed and torque as a CIM it will require a signifigant amt. of weight.

Not to take a side on the FP vs. CIM debate, but an FP + AM Planetary to get it around the same output speed as the CIM is actually about 1 lb less than a CIM. We looked into this as a weight savings option for 2009, but found the weight in other areas. Just want to pepper some facts into our daily discussion.

[sanddrag]

I think the absence of a full and structured set of rules would be the failure of FRC.

[EricH]

David, I think the expansion of the MI district system will be the failure of FRC.

Note: The above statement is not repeat not my real view. I am making it to make a point.

Anyone can say anything they like, but I'd rather have some reasons. I don't really care if it's just plain, "I don't like it", as long as it's a reason. Especially if it's a reasonable reason or brings up something I didn't see.

I can see where he's coming from. FRC started with a very restrictive set of rules. KOP, $X00 from SPI, Y, Z, A, B, C, in various amounts from Home Depot, here's the game, go build us a robot. Then they relaxed the rules, in part because suppliers were getting overwhelmed. They're very open now. If they're opened further, nobody really knows what's going to happen.

But I don't think FRC would fail. It could get very interesting, though, as teams face more difficult decisions. It would also depend on the manner of the expansion--X types in Y amounts, anything under $Z, A power, 12V system, or any other type of expansion you can imagine. But it probably wouldn't fail. It might even become stronger.

[Travis Hoffman]

Originally Posted by Collin Fultz

Not to take a side on the FP vs. CIM debate, but an FP + AM Planetary to get it around the same output speed as the CIM is actually about 1 lb less than a CIM. We looked into this as a weight savings option for 2009, but found the weight in other areas. Just want to pepper some facts into our daily discussion.

The FP + Banebot 42 mm planetary (currently in P60 form) is even lighter and more compact, I believe. This has been a reliable combo for us the past few years. The RS-550 has also been a reliable workhorse when coupled to this gearbox. In many, but not all, cases, I'd still prefer this option over a CIM + reduction of choice.

[Brandon Holley]

Originally Posted by Collin Fultz

Not to take a side on the FP vs. CIM debate, but an FP + AM Planetary to get it around the same output speed as the CIM is actually about 1 lb less than a CIM. We looked into this as a weight savings option for 2009, but found the weight in other areas. Just want to pepper some facts into our daily discussion.

I can see the FP being lighter as you have pointed out here, and I really dont have a strong preference either way. I simply like the reliability of a CIM over that of a FP, so much so that in most (but not all cases) i'd be willing to sacrifice that pound of weight.