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.