Andy Mark Super Shifters

[Jecht22]

Hey I wanted to ask a few questions to the teams who have used the andy mark super shifters before. Does it make a big difference to shift them using pneumatics or servos. Assuming the answer to this question is that pneumatics will be better, is it possible to use electrical solenoid actuators instead.

[Grim Tuesday]

The pneumatic shifting is definitely better. When you only have 120 seconds to play with, if shifting takes 1-2 seconds, it is wasted time. You also might have to stop driving to shift. With pneumatic, it is instantaneous.

The only downside to pneumatic that I can see is the requirement that you have to have a compressor and added weight. Though, if this is the only pneumatic thing on there, you may be able to get away with pre-charging some tanks.

[Matt H.]

Originally Posted by Jecht22

is it possible to use electrical solenoid actuators instead.

It might be, but the performance won't be the same as pneumatics.

R48J limits you to Solenoids rated at less than 10 Watts continuous duty:

electrical solenoid actuators, no greater than 1 in. stroke and rated at no greater than 10 watts continuous duty at 12V

A quick look at McMaster-Carr shows that all their solenoids meeting that rule have a maximum force of less than or exactly 5lbs.

In contrast the 3/4" bore pneumatic cylinder recommended by andymark has a force of about 25lbs.

Also, designing mounting brackets to interface the solenoid with the shifter will be an annoyance.

[ajlapp]

Team RUSH, FRC27, has used servo shifting on our SS transmissions since 2008 without incident.

We shift on the fly with no issues. We couldn't be happier with it.

[DonRotolo]

We avoid servo shifting because it is a little sluggish. But it is reliable enough.

[PayneTrain]

I'd go for the pneumatics if your weight can give up all of those components, but don't anticipate your robot will make a giant decline in quality if you go with the supplied servo.

AndyMark knows it's reliable enough to include it in the package. They don't ship bad stuff. (Here's to you, RS-775s!)

[IndySam]

Originally Posted by Matt H.

It might be, but the performance won't be the same as pneumatics.

R48J limits you to Solenoids rated at less than 10 Watts continuous duty:



A quick look at McMaster-Carr shows that all their solenoids meeting that rule have a maximum force of less than or exactly 5lbs.

In contrast the 3/4" bore pneumatic cylinder recommended by andymark has a force of about 25lbs.

Also, designing mounting brackets to interface the solenoid with the shifter will be an annoyance.

McMaster 69905K85 10w continuous duty is rated at 60 lbs.

[Captaindan]

they are definitely the way to go as far as transmissions we have gone with both methods of shifting with no problems

[cmwilson13]

pneumatic is definitely the way to go

if u go with this cylinder you also use half the air and if for some reason your pneumatic system fails it will lock you in low gear instead of in between gears

http://www.andymark.com/product-p/am-0591.htm

last year we used the super shifters with encoders and had automatic shifting using Hysteresis . it made a huge difference

[Easton8]

if you're using servo shifting you robot will take a few seconds to shift, and the robot can't be moving. That takes away valuable time that you could be using to be scoring or doing other things. Pneumatic shifting is faster (takes less than a second), and you can shift while your robot is driving at full speed. Unless your team insists on not having pneumatics in your robot for some reason the pneumatic shifting is most definitely the preferable method.

[Grim Tuesday]

Originally Posted by cmwilson13

pneumatic is definitely the way to go

if u go with this cylinder you also use half the air and if for some reason your pneumatic system fails it will lock you in low gear instead of in between gears

http://www.andymark.com/product-p/am-0591.htm

last year we used the super shifters with encoders and had automatic shifting using Hysteresis . it made a huge difference

What is Hysteresis?

Pneumatic shifting broke our SuperShifters. Go with servo.

We've been using our supershifters with pneumatics all of last year, and have had no such problems. Care to elaborate?

[theprgramerdude]

The locking pin, or whatever it is, that connects the shaft to the rotating thingy with the piston inside it broke; We think it's due to shifting at full power while not having the gears in motion.

After replacing (or something or other) the pin and adding quite a bit of glue (loctite? I wasn't really watching when they were fixing it), and lowering the pressure going to the pistons by means of the regulator, this hasn't happened since.

Note: This happened to BOTH SS's while they were on the robot and we were testing them.

[EricH]

I think some teams had trouble with shifters last year, but it wasn't the pneumatics. It was roll pins that were not quite durable enough, which has since been fixed, IIRC.

[cmwilson13]

Hysteresis is a programming term i don't know the technical definition but it prevents the pistons from shifting very rapidly between high and low when you are right at the speed at which the transmission shifts up and down.

a very simple Hysteresis is to have them shift up at say 5 ft/s but shift down at 3ft/s which prevents the chattering which occurs if u shift up and down at the same speed.

as for the super shifters breaking if you use pneumatics that was a specific problem m in last years supper shifters they changed a roll pin to a screw and the screw could not handle the stress and would fail. we had a roll pin in ours and with the auto shiting we shifted anywhere from 20-50 times a match depending on how much we started and stopped and never broke a super shifter

we where also shifting at 60 psi all season.


edit:http://en.wikipedia.org/wiki/Hysteresis#Control_systems

[Matt H.]

Originally Posted by IndySam

McMaster 69905K85 10w continuous duty is rated at 60 lbs.

It's rated for 60 oz which is 3.75 lbs.