Hi my team was thinking about doing shifting transmissions this year and I wanted to get some advice about them before we go and put down a larges sum of money.
How do you mount them I have seen the pic. and I don’t see any mounting brackets
what do most people use for the ratios. should we use the standard or go for a optional ratio.
Should my team go for servo of pneumatic shifting. Myself I would go with pneumatic but I have been wrong before,
Some background, this is my 5 year in FRC. I moved and stared a team in klamath falls OR. 3 years ago just this season our numbers have tripled. This year my team will most likely go with the kit bot on steroids,(6 wheel drive with 6’’ placation wheels). We have limited machining, but we can still make parts if necessary.
If anyone needs more info I will be most glad to share it. Any other advice would be great to.
We’ll also be using them this year, so here’s some info I know about them.
The ratios should depend on the game. You don’t want to gear for really fast if the game doesn’t require a lot of speed, and likewise, you don’t want to have a really slow gear if you don’t need to push anything.
Personally, I’d choose the pneumatic shifting, as it allows for shifting on the fly, and can be a lot better in some situations than servos (Such as shifting while going at full speed).
We, too, plan on using 1114’s Kitbot on Steroids this year, with AM SuperShifters, so if you have any questions on it, feel free to contact us or PM me!
The four 1/4-20 bolts that hold the box together can also be used to face mount. Otherwise, you’re making your own brackets and holes.
Should my team go for servo of pneumatic shifting. Myself I would go with pneumatic but I have been wrong before,
Pneumatic leads to wasted weight if you don’t have other pneumatic systems. You need at least an air tank, a relay module, valves and a solenoid in addition to the cylinders, whereas you have just the two servos in the alternate setup. You also run the (reasonably slight) risk of running out of air mid-match.
We’ve only used servo shifting recently because we haven’t used any pneumatic systems in the last few years, and it’s worked fine for us. The servos didn’t break and we shifted smoothly enough. SuperNerd is right that the pneumatic shifting is faster and firmer, but I don’t think that’s enough reason to warrant building a whole pneumatics system just for shifting.
I forgot to mention that! :o Yeah, Ninja_Bait’s right. Unless you’re using pneumatics in other places, then I don’t suggest using pneumatic shifting. While it is more on the fly, the weight used is much needed elsewhere. So unless you’re already using pneumatics for a few things already, use servos. They may not be as fast, but shave a lot of your weight compared to pneumatics.
You could just put on a large plastic tank and just refill it before each match Pneumatic over servo shifting is preferred, but 27 has had great success with servos. Try out both, but most teams end up using pneumatics for shifting and wouldn’t ever do anything else.
Here’s a shot of how we mounted our shifters this year. We took the transmission bolts and ran them through our side rail and the transmission.
Choosing ratios is a game based decision. Personally, I found that the standard ratio was a little slower than I liked in 2011. Would’ve been fine for 2010 though. On an open field you may want to gear a little faster than a closed field.
Pneumatic shifting is our preferred method. I’ve heard nothing but bad things about servo shift, and my experience with servos in FRC hasn’t been the best.
Check out FRC Designs for different robots that include shifting transmissions. This website has the CAD for different transmissions and robots. You can also go to the Drives Page to see different assemblies. Let me know if you have any questions. Thanks!
971 uses the AM guts, makes custom plates, mods the gears and adds a hex shaft with pot attachment. If you go pneumatic make sure you tune the dog gear alignment before you do a final tighten. Always good to break in the motors and the transmission and make sure you use lots of lube on the gears.
Always check the main pinion for wear and tear. If your robot is geared fast and does high speed direction changes the pinion can have a catastrophic failure. Here is our tech note
Note that if you use AM Shifters with pneumatics, you’ll want to CAD them to ensure that the pneumatic cylinders do not interfere with each other. This is especially crucial if you use the C-Base setup and direct drive the middle wheels.
If you’re doing a kitbot-on-steroids setup, this isn’t really a concern.
We mounted our supershifters in this manner and while it was simple and easy it takes a while to take off. In the off-season we built a new robot and instead of using the two c base plates to support the trannys, we took some of the AM cross hex tube from the kit to span between using the top four bolts. Very easy and a whole lot easier to work on the drivebase!
I’d recommend pnuematic shifting over servos. If the drivebase is the only item that is using pnuematics, then a pre-filled tank is viable. Do a simple test of how many times you can shift before your compressor kicks in. You’d be surprised how few times you end up shifting in a match. This past year we shifted maybe 5-6 times per match but your needs will change based on your robot. I’ve heard of several teams doing this but they just end up putting the compressor on because they have the weigh to spare.
We tried this recently and it works great. We normally pre charge our pneumatic system via an external compressor so the compressor has to do less work before each match.
On our offseason projects. We put two 44 cubic plastic tanks on there. We get around 150+ shifts via a 5/8ths od pneumatic cylinder with spring return. We normally like to have a compressor on board but if your only shifting your fine. IIRC 217 this year used hella plastic tanks and no compressor? Can someone confirm?
217 had 8 (visible, maybe more hidden) tanks and no onboard compressor.
They actuated their minibot deployment, claw, and shifting pneumatically.
We needed a compressor due to the air usage of the dual drive, and still ran low on air at the beginning of the season (With only 2 of the plastic tanks and the Viair mini-pump). We later added more tanks, and are currently at 6, and seem to be OK, but it takes 3 minutes to pump up.
Relating to the shift pistons, we used modified SuperShifters (same guts, new side plates, AM long shaft, spacers instead of the box) with small cylinders, to fit the battery in between the drive CIM’s (vertically). We had to machine a new interface plate for the piston (we took the AM one and added more holes), and an odd stud (1/4-28 one end, #10-32 on the other) to interface with the pistons.
We had no issues with the modified SS’s on the competition robot, or the stock SS’s on the practice robot all season. Each robot saw many hours of use.
Pneumatic over servo shifting is preferred, but 27 has had great success with servos. Try out both, but most teams end up using pneumatics for shifting and wouldn’t ever do anything else.
