Shifting or Non-Shifting
 

Does your team have multiple speed gearboxes? If so what kind?

Re: Shifting or Non-Shifting
 

Andymark. 1-speed toughboxes and 2-speed AM Shifters/SuperShifters. The best thing now.


In the Pre-AM days, we used to use DeWalt gearboxes (3-speed servo shifted), and prior to that we built custom 2-speed and 4-speed mesh shifting gearboxes. However, an AM shifter or SuperShifter is better than the DeWalts because it shifts more reliably (the DeWalts won't shift under very heavy load), and easier to manufacture (you make nothing, unless you are reducing weight).

Our custom 4-speed took quite a lot of manufacturing resources (we cut a bunch of gears from pinion stock, welded some together, made 5 shafts per transmission, and machined side plates).

Re: Shifting or Non-Shifting
 

We used tough box nano's last year. They worked great, but in the off season were looking at the AM super shifters and were looking to use them in 2011.

Re: Shifting or Non-Shifting
 

My team doesn't shift mainly for cost reasons. It'd be nice to have for specific games and specific situations, but it's not that hard to make do with a single speed for most games. Last year wasn't so bad for non shifting teams since the field was divided into small enough sections that you might not be able to really take advantage of a robot going >9FPS

Re: Shifting or Non-Shifting
 

I chose other.

At the moment, I don't believe we have one. After our Quarterfinal defeat at NU CT Regional, there's a lot of talk about adopting one (obviously taking the 2011 game into consideration).

Re: Shifting or Non-Shifting
 

What's the game call for?

330's had both: 2-speed drill trannies from 2001-2004, single-speed KOP gearboxes in 2005 and 2006, and AM shifters 2007 and 2010. (Can't remember 2008/2009, but I'm pretty sure 2008 was an AM shifter as well.) It depends on what the game is and what we think we need.

Re: Shifting or Non-Shifting
 

Knowing how you guys played, was not shifting really your big downfall?

Was your robot 120 lbs max?

Did you have high traction wheels?

Both of those things will matter before shifting will. Shifting won't help a mecanum drive in a pushing match either.

Re: Shifting or Non-Shifting
 

Last year we had single speed gearboxes geared for about 10.5 ft/s in our swerve drive and a selectable-output shifting gearbox for our dual kickers. Our real-world results confirmed our calculations that showed a single-speed gearbox geared for 10.5 ft/sec was a very good compromise between speed and traction with our customized Colson wheels.



In the future, we'll likely use 2-speed shifting gearboxes on our drive train if we go with a normal 6WD.

Re: Shifting or Non-Shifting
 

Hey Art,
Did WPI manufacture that setup? Thats pretty impressive!

Also, AM Supershifters, shifted pneumatically. We attempted to do the servo shifting setup in 2009 (because there was nothing else that we needed pneumatics for) and we had a lot of problems!

Re: Shifting or Non-Shifting
 

AM Supershifters, shifted pneumatically.

Re: Shifting or Non-Shifting
 

1618 used AndyMark shifters in 2007 (with the big and small CIMs) and 2008 (four CIMS); 2815 and 1398 used the guts of one in a six-motor setup (CIMs and FPs) in 2010. Nobody used anything but Toughboxes in 2009, because the game didn't call for them. (That year, for the record, 1618 used two CIMs for ease of assembly, while 2815 used FPs in an AM Planetary to free up the CIMs for the most the highest-powered conveyor dumper of 2009.)

In 2010, shifting was also scarce enough to justify leaving off the compressor.

Re: Shifting or Non-Shifting
 

We have used:

* 1-speed drill transmissions in 2000-2003
* A custom 1-speed worm gear transmission in 2004
* AM Gen 1 shifter in 2005
* AM Gen 1 shifter in 2006
* ToughBoxes in 2007 (omni drive)
* ToughBoxes in 2008 (omni drive)
* ToughBoxes in 2009 (regolith)
* AM Gen 1 shifter in 2010, but modified back into a 1-speed for weight/usefulness reasons (we split the difference between high and low and that was more than fine for the primarily short dashes around the field, and we were still traction-limited in brief pushing contests)

Re: Shifting or Non-Shifting
 

What problems did you have?

We have used AM shifters with servos for two seasons without incident. In fact I'd like to see AM change the wording on their site with respect to servo shifting......I feel it is robust, fast and reliable. :D

Re: Shifting or Non-Shifting
 

All the sheet metal parts were fabricated by two sheet-metal machine shop sponsors, while the aluminum rings were machined at a regular machine shop sponsor. All the internal guts were machined or lightened on our team's manual mill and lathe. I enjoy occasionally machining parts, so I've made a few parts for GUS at the WPI machine shops before, but lately it's been easier to find machine shop sponsors.

We've also had intermittent issues with servo-shifted gearboxes; once the internal gears of the servo stripped out, and other times the servo seemed to lack the fortitude to actually shift. More grease probably could have helped both of those problems, but I have yet to confirm if this was the issue.

Re: Shifting or Non-Shifting
 

We Like shifters and have run AndyMark's shifters in the past, but now run our own design heavily influenced by his.

We shift primarily to make sure our low gear is nice and slow with plenty of force, and that our high gears is as fast as necessary for the game. It's tough to nail both of those with a single speed.

For all of the carpeted games in recent history, I can't think of one where I would not want shifting.

Luckily it is now legal to use COTS metal gear servos, which are more or less the standard in ground RC vehicles now. Still doesn't fix them having less force, but certainly they are more durable.

Re: Shifting or Non-Shifting
 

For the 2010 game we used two AM Supershifters with pneumatic actuation.

Excellent transmissions, never gave us any trouble at all.

The real question you want to ask yourself when you design is "Do i need to be able to put down power when necessary, or can I get away with one speed", because it is not an insignificant increase in cost.

Please also notice that while AM supershifters do come with servos, our team never had any luck with them. The most powerful servos we were allowed to use in FRC didn't shift at the same time, and had some pretty long delays in shifting if the robot was in motion at all. The pneumatic actuation "just works, right now"

Re: Shifting or Non-Shifting
 

Really depends on the game. For Overdrive they were critical last year not so much. Also you pay a big penalty in weight for shifting.

We have used AM transmissions exclusively since Aim High. Those include AM gen 1 and 2, Supershifters, Toughboxes and Nanos.

Re: Shifting or Non-Shifting
 

Our shifters are heavier than if we were to run our own single speeds, but they are still lighter than toughboxes by a good deal. I wouldn't quite call it a penalty.

Re: Shifting or Non-Shifting
 

That's apples to oranges man :)

Your shifters > your single speeds

AM SS > Toughbox.

Re: Shifting or Non-Shifting
 

Wow! Are all of those parts fabricated on the manual mill and lathe? Some of the gearboxes and sprockets look pretty impossible with my current skill-sets on the machines.

And the problems you are describing with the servo gears stripping out is the same exact problems we have had. We even went to the extreme and searched frivolously for the same servo with metal gears. Like we were going to find one of them! :rolleyes:

Re: Shifting or Non-Shifting
 

The servos are better now than in previous years, but if given the choice, the pneumatic shift is the stronger, more reliable choice.

If you are already going to have other pneumatic needs on the robot, then go with pneumatic shifting. Very minimal increase in weight.

If you are not going to have other pneumatic needs, you have two good options.

(1) You can use the reserviors and charge the system before a match. This saves the compressor weight. We did the math a few years ago and you can get more than a match worth of shifts from the air you can store in 2 tanks. You can calculate the volume in the cyclinder and in the tanks and do the math.

(2) Use the servos.


One tip, run both shifters off of the same valve and use a T fitting. By doing this, you are more assured that both gearboxes are in the same gear. If you use two valves, and have any kind of failure on one side (connector loose, valve sticks, software glitch, etc.) you can end up with one side in "hi" and one side in "low". This also makes sure you are defaulting into the same gear at start-up. It also saves some weight.

Re: Shifting or Non-Shifting
 

We manually machine the "internal guts" of the gearboxes like shafts, spacers, and lightened gears (and by we I mean our devoted machinist mentor/parent of two alumni).

Re: Shifting or Non-Shifting
 

Another fun way to make that part is to laser cut out a couple layers of sheet metal that have the spline cut into them, and a sprocket which has the spline cut into it, and then bolt them all together. You can see it here. Not sure if it's easier than what you did, but it's another way to do things.

Re: Shifting or Non-Shifting
 

Very nice! Those adapters look just like the ones I just machined out for my engineering design car! I would expect a little better from mechanical engineering majors at WPI! ;)

Re: Shifting or Non-Shifting
 

701 used 2-speed AM shifters in 2006 and 2008. You really need to look at the game. If we see a wide open field and a need to get around quickly - then shifters are a way to go. Otherwise I don't think they're that much of an advantage, especially considering cost and weight.

We tried the servo shifters in '08 and couldn't get them to work reliably, they always seem to shift one side before the other. Pnuematic is the way to go. If you have no other pnuematic components, consider a pre-pressurized system, and not use a compressor on the bot.

Re: Shifting or Non-Shifting
 

We found it unnecessary to shift in '06 and '07. In 2008, we used AM super-shifters so that we could shift into low going around the corners.

In '09, there was no reason to have shifters. Never once did we manage anywhere near full speed with all the tire slip, and having a more highly geared transmission (lower top speed) would have allowed us better traction control. Shame on me for not thinking about that until today....

In '10 with the compressed field, we didn't find shifting necessary. We had good traction and really the farthest you were accelerating was from one goal to the other, a total of around 20 feet. Top speed wasn't necessary.

Re: Shifting or Non-Shifting
 

Does anyone here know whether it'd be worth the weight-cost/savings (depending on what you're changing from) of using a Denso motor instead of a servo to shift? I'd like to explore the concept with my team, as we feel pneumatics have such a significant weight penalty and offer such a low efficiency and power output.

Re: Shifting or Non-Shifting
 

we have made custom 3 speed and 4 speed gearboxes for aim high and ramp riot, all the other years have been drill transmissions or 1 speed BaneBots. we are looking at using these this year.

http://www.robotmarketplace.com/prod...629059-00.html

mounted in a custom aluminum housing.

Re: Shifting or Non-Shifting
 

It has already been mentioned that in years past you could precharge a couple of tanks prior to a match and not have an on board compressor. This is not a low efficiency, it is basically free energy for your robot. The weight penalty isn't that bad either because you lose a lot of components by doing this.

I would wager that a lead screw+denso would weigh a bunch more, and would also require a lot more effort on your behalf. You probably also want to keep your shift mechanism as simple as possible, because a complicated shifter is often an unreliable shifter.

Re: Shifting or Non-Shifting
 

Low efficiency and power output! Where did that come from? How many motors in the kit can move 180 lbs without a big gearbox?

Adding pneumatics is a great way to add a lot more power and versatility to any robot, without the imposed limit on available motors. We have used it on every bot but one in our history. I don't know how many times we have quickly added extra mechanisms at competitions because we had a compressor on board. A solenoid and a bit of hose and boom your done.

Yes there is a weight and space penalty but when you start figuring weight of speed controllers, wire (adds weight a lot faster than you think) and gearboxes it's not as big as most people suppose.

Also the ability to add linear motion without a fancy mechanism is an added bonus.

Re: Shifting or Non-Shifting
 

All of the merits of pneumatics being said, some teams did use a leadscrew and Window motor to shift gearboxes last year. Almost all of those shifters were used to release kickers with >200 lbs of stored energy, though. Pneumatics are definitely okay for shifting.

Re: Shifting or Non-Shifting
 

Word of caution.

We used 36v Dewalt Transmissions during 2009 and at the start of 2010. We had been failing the 18v Dewalt components regularly during the 2008 season.

Suffice to say the 36v Dewalt components did not survive long. We switched to supershifters before our first tournament last year...and I don't see us going back to the Dewalt setup.

All told, without lightening, the Supershifters were only a marginal weight penalty.

Re: Shifting or Non-Shifting
 

We have always use the Andy Mark super shifters. They have work great for us.

Re: Shifting or Non-Shifting
 

But certainly much easier to work with, and despite not having ever ran dewalts, much more durable.

Re: Shifting or Non-Shifting
 

Well, define big gearbox. The toughbox can easily provide over 200 lb's of force in it's basic setup, and all of the benefits of pneumatics can be just as easily accomplished with a small rack, screw, or the like.

Re: Shifting or Non-Shifting
 

If you're trying to shift, the toughbox is a big gearbox to use to generate that sort of motion.

The original post you're responding to: "How many motors in the kit can move 180 lbs without a big gearbox?"
Your answer: the "toughbox".

The toughbox is a gearbox, and therefore only as good as the motors you put into it. The question still stands unanswered.

If I was to shift using a motor, I'd use a Denso with a linkage system. Plant Denso between the gearboxes; power on one way to shift one way, power on the other way to shift the other way. If you saw 330's wedges in 2005, those were powered by Densos (or their predecessors) on Spikes, IIRC. They also went from vertical to wedging in about half a second with no linkages. By playing with the linkage size, you could make a Denso faster if you wanted to.

Re: Shifting or Non-Shifting
 

We generally avoid using pneumatics for high loads due to air capacity, but to say that pneumatics don't have any advantages over electrical systems is not true.

Pneumatics are great for holding things with a (near) constant force and being able to simultaneous handle shock loads that a geared system could have trouble with. They're also nice for grabbers and the like as there is no feedback required, you tell them to go and (assuming nothing breaks) they go. To achieve similar point to point movement with an electrical system you'd need some sort of sensor, or a very talented (and overworked) driver.

Re: Shifting or Non-Shifting
 

Use a toughbox and there goes a big part of your weight advantage and stall that with anything other than a CIM and magic smoke will appear.

I have no problems with teams preferring to use motors over pneumatics but if you are going to make blanket statements like "low efficiency and power output" you're gonna get called on it.

Re: Shifting or Non-Shifting
 

Oh man. The, [SARCASM]"Fun,"[/SARCASM] we have had with magic smoke!