Gearbox AFTER Transmission?

[rich2202]

Our team has always used single speed gearboxes, and is now considering learning to use the 2-speed transmissions on Andymark.

Pricewise, it is $273 for the AM Shifter with the 2nd set of gears and pneumatics, or $360 for the Sonic Shifter (gears, pneumatics). Does the Sonic Shifter provide all the range typically used (assuming a complete set of gears)?

The basic setup of the transmissions allows direct drive by CIM motors, or through the AM Planetary Gearbox. If you use the gearbox, you would need one for each motor. Can you put a gearbox after the Transmission? That would be one gearbox per Transmission, rather than two.

If we can put a gearbox after the transmission, we can reuse the gearboxes we already have. Then the AM Shifter is all we need to choose between 1.56:1 or 4.00:1 ratio between low/high gear.

Summary:
1) Does the Sonic Shifter, with a complete set of gears, provide the range of ratios typically used?

2) Can you use the AM Shifter with a gearbox after the transmission?

If the Sonic Shifter (with a complete set of gears) provide the typical range, then that might be the way to go to reduce space and simplify construction.

Any other words of wisdom?

Thanks.

[Chris is me]

I don't understand what you're referring to when you say gearboxes or transmission. The shifting transmissions are gearboxes. For the SuperShifter and Sonic Shifter, you just need to input a CIM and the output can be geared such that the box can direct drive 6 or 8 inch wheels comfortably.

In addition to the shifting reduction, AM shifter gearboxes include a reduction before and after the shifting stage to further slow the CIM.

The AM Shifter only has two reductions as the final reduction is meant to be in the sprockets connecting the wheels to the gearbox output. This is easier to tune than a direct drive system.

Edit: just reread your post, I think I get your question. No, AM Planetaries are not required for typical FRC applications. They are listed on the product page because they have the same output features as a CIM and some teams may want to do something weird like using 1 CIM + 1 550 with planetary instead of two CIMs

[Michael Hill]

Originally Posted by rich2202

Our team has always used single speed gearboxes, and is now considering learning to use the 2-speed transmissions on Andymark.

Pricewise, it is $273 for the AM Shifter with the 2nd set of gears and pneumatics, or $360 for the Sonic Shifter (gears, pneumatics). Does the Sonic Shifter provide all the range typically used (assuming a complete set of gears)?

The basic setup of the transmissions allows direct drive by CIM motors, or through the AM Planetary Gearbox. If you use the gearbox, you would need one for each motor. Can you put a gearbox after the Transmission? That would be one gearbox per Transmission, rather than two.

If we can put a gearbox after the transmission, we can reuse the gearboxes we already have. Then the AM Shifter is all we need to choose between 1.56:1 or 4.00:1 ratio between low/high gear.

Summary:
1) Does the Sonic Shifter, with a complete set of gears, provide the range of ratios typically used?

2) Can you use the AM Shifter with a gearbox after the transmission?

If the Sonic Shifter (with a complete set of gears) provide the typical range, then that might be the way to go to reduce space and simplify construction.

Any other words of wisdom?

Thanks.

Well, sure, there's nothing in the rules (or physics) that says you can't. However, keep in mind that additional gearboxes = more weight and more moving parts = more likely something is likely to break. The Sonic Shifter looks like it has the same shifting options than the Super Shifter plus some.

Pardon my ignorance, but I'm not entirely sure what you mean about need a gearbox for each motor. You only need 1 SuperShifter for each set of 2 motors (generally 1 gearbox on each side).

[coalhot]

Any reason why you aren't looking at the Vexpro ball shifters? Just wondering...

[rich2202]

Originally Posted by Michael Hill

Pardon my ignorance, but I'm not entirely sure what you mean about need a gearbox for each motor. You only need 1 SuperShifter for each set of 2 motors (generally 1 gearbox on each side).

If you want a ratio that is different from the ones provided, you have to put something (another gearbox) before or after the Super Shifter. The Andymark page says their transmissions accept either: 1) 2 CIM motors, or 2) 2 AM Planetary Gearboxes. So, if you want to raise the reduction ratio, you add a AM Planetary Gearbox prior to the Transmission. Since each transmission accepts 2 motor inputs, you need 2 AM Planetary Gearboxes if they are put between the CIM and the Transmission.

However, if you gear down after the transmission (CIM->Transmission-> AM Planetary Gearbox), then you only need one AM Planetary Gearbox. This assumes you don't exceed the capabilities of the AM Planetary Gearbox (can it accept that much torque on the input?).

Any reason why you aren't looking at the Vexpro ball shifters?

My team is Andymark fans. They assume Andymark stuff will take the beating of a normal FRC competition. I'm sure once we gain experience with transmissions, they will be more open to other options.

The AM Shifter only has two reductions as the final reduction is meant to be in the sprockets connecting the wheels to the gearbox output. This is easier to tune than a direct drive system.

Thanks. Stock ratios (sonic and super shifter) are fine for typical FRC applications. Use AM Shifter if you want to fine tune with last gear.

I assume we will direct connect 2 CIMs to the Transmission. Glad to know the AM Planetary Gearbox is not normally used between the CIM and Transmission.

I assume the 4.0:1.0 ratio is when you want a lot of power to push around another robot, or fine motor control (such as when balancing). Whereas, the 2.6:1.0 gives you a little more control when driving slow.

[Woolly]

Originally Posted by rich2202

My team is Andymark fans. They assume Andymark stuff will take the beating of a normal FRC competition. I'm sure once we gain experience with transmissions, they will be more open to other options.

If it were me on your team, I'd be lobbying for the Vexpro ball shifters as well, they're $100 cheaper and over a pound lighter, and the pneumatic cylinder for shifting the Vexpro model is included with it.

Now you do have to use hex shafts with it, and buy special bearings, but that does give you the advantage of not having to deal with keys.

Originally Posted by rich2202

I assume the 4.0:1.0 ratio is when you want a lot of power to push around another robot, or fine motor control (such as when balancing). Whereas, the 2.6:1.0 gives you a little more control when driving slow.

4:1 is better for pushing power, control, and acceleration
2.6:1 is better for speed and.... speed (gotta go fast).

But both those ratios look a bit high unless you're using really small wheels.
For a drivetrain with 6" wheels, the Vexpro's 2-stage ratios would make much more sense. You have to remember you will only travel a max of 60 feet in any given maneuver, and for most games you're going to be in low gear most of the time unless you're doing something like cycling in 2013.

[Chris is me]

Originally Posted by Woolly

4:1 is better for pushing power, control, and acceleration
2.6:1 is better for speed and.... speed (gotta go fast).

He's not referring to the overall gear ratios, he's referring to the shifter spread.

The 4:1 spread is best if you want a very fast high gear and a slow low gear, or a very slow low gear and a fast high gear. If you're going for the fairly standard ~14FPS high, ~5FPS low, you'll want the 2.67:1. Really, unless you have a good reason to go very fast and very slow I would use the narrower spread.

[rich2202]

Thanks for all the advice.

Question on Pneumatics:

Let's say we don't need pneumatics for anything else (although we tend to find something every year). The shifters don't seem to need much air.

1) Is a storage tank enough air to comfortably last a round?
2) Can you keep a tank primed while waiting when you are on-deck (battery powered pump on the cart)?

[BrendanB]

Originally Posted by rich2202

Thanks for all the advice.

Question on Pneumatics:

Let's say we don't need pneumatics for anything else (although we tend to find something every year). The shifters don't seem to need much air.

1) Is a storage tank enough air to comfortably last a round?
2) Can you keep a tank primed while waiting when you are on-deck (battery powered pump on the cart)?

Yes. In 2012 our robot was slightly overweight and since we only used air for shifting the compressor was the first to go.

We used one plastic air tank on our robot and made a small board that had the compressor and other required electronics. Make sure you read the rules closely on what has to be on the robot to make the system legal.

While waiting in que we would wait until halfway through the match before us to start charging. We never ran into air problems while running the AM supershifters shifting maybe 5-10 times a match (couldn't really tell you it depends on the driver).

Since we were strapped for weight (and passed inspection by cutting off one ziptie) we only had the one tank on the robot. In the off-season we added an additional plastic tank after taking something else off as a safety. 2012 was a good year since the game was designed for fast turnaround between matches. We also worked to make sure the pnuematics system had little to no air loss.

Pistons with springs are helpful so if you lose air they shift to a specific gear (low for most teams or high if you are 67).

If our shifters were the only pnuematics we had in 2013 I would have felt much safer with 2-3 plastic tanks. We had a few matches where the time from on deck to match start were 10+ minutes.

[protoserge]

Originally Posted by rich2202

1) Is a storage tank enough air to comfortably last a round?
2) Can you keep a tank primed while waiting when you are on-deck (battery powered pump on the cart)?

1) It depends on the number of shifts you want to perform. You will need to do calculations to determine the loss of air at each shift. Longer hose runs will start to affect the number of shift actuations. We have a good presentation on this here.

2) You can have one offboard compressor powered by the robot (the
battery installed in the robot). The 44 cu in tank @120 psi should suffice if you're shifting occasionally.

3) Take a look at the VEX Pro Ball Shifters. They are pretty slick.

[Aren Siekmeier]

Originally Posted by rich2202

2) Can you use the AM Shifter with a gearbox after the transmission?

It's certainly possible (no different than adding another stage), but be careful what gearbox you put at the output of your shifter. The AM Planetary is designed to be used with a single 9015 motor at very high speeds and low torques (up 0.4 Nm to at stall) at the input. By comparison, two CIMs through a 10:1 reduction would give up to 48 Nm at the input to the AM Planetary (that's 100 times more ). I don't know how the AM Planetary in particular is rated, but usually gearboxes exploding is a bad thing.

[Qbot2640]

Originally Posted by stinglikeabee

2) You can have one offboard compressor powered by the robot (the
battery installed in the robot). The 44 cu in tank @120 psi should suffice if you're shifting occasionally.

Mount your compressor on your robot cart, and create a way to plug it into the robot's electrical system easily - so you can recharge your tank(s) quickly between matches.

[Bill_B]

Originally Posted by Qbot2640

Mount your compressor on your robot cart, and create a way to plug it into the robot's electrical system easily - so you can recharge your tank(s) quickly between matches.

I recommend using powerpole connectors for the task. Yes, the capacity is a waste for the pressure switch connection, but for the sake of ease of use it will be worth it to have all four wires able to be plugged into your control board at once. You can also insure correct connections by having all four 'poles in a row so there is only one way to hitch them together. PM if you need more info.