To shift or not to shift?

[Neal Probert]

If you have to stop to shift gears, it's not worth it. You only have a couple minutes in the contest and wasting time just shifting gears is not a good idea.

We tried it, with the shifter on the drill motors, last year on #830. With the servos linked to the clutch on the drill motors, it never really worked right.

We had to lock the clutch to prevent slipping and we eventually locked the drill into low speed. We could push around a bit and still get across the field reasonably fast.

This year, on #1015, we have tentative plans to go with a dual motor gearbox.

[ChrisH]

Originally posted by Neal Probert
If you have to stop to shift gears, it's not worth it. You only have a couple minutes in the contest and wasting time just shifting gears is not a good idea.

It depends on your mission whether or not taking time to shift is a waste of time. It also depends on the length of time it takes to make the shift and how reliable your system is.

We tried it, with the shifter on the drill motors, last year on #830. With the servos linked to the clutch on the drill motors, it never really worked right.

There's your problem right there, servos. A small pnuematic cylinder works much better for shifting if it is properly linked to the tranny. The pnuematics are also much faster and if all you are doing is shifting, you probably don't need the compressor either.

We had to lock the clutch to prevent slipping and we eventually locked the drill into low speed. We could push around a bit and still get across the field reasonably fast.

Locking the drill motor clutch should be standard procedure. If your low speed was still reasonably fast it was geared too high to start with.

This year, on #1015, we have tentative plans to go with a dual motor gearbox.

Hope you're working on it already, not the real one, a prototype of course!

[FatNick]

In spam 180s case we used a shift on the fly design and numatics to shif. they worked out well together. and the sensors desined to work with that reflective tape they work great in the shift on the fly area the drive train.

[FatNick]

Originally posted by ChrisH


. A small pnuematic cylinder works much better for shifting if it is properly linked to the tranny. The pnuematics are also much faster and if all you are doing is shifting, you probably don't need the compressor either.

IN spams case that compressor was the most important thing on our bot, yes we also had a pnuematic goal graber but we shifted back and forth between gears at least 10 times in one match. we even broke our toggle switch to sift one but thanks to our driver who has long finger nails (he plays guitar) we were still able to shift.

[Alexander McGee]

i think that it is bsolutely necessary to shift during game play. our robot had 4 wheel drive, witht he technocats transmission desigm, and our matching, patented designed for the chiapuah motors. its shift on the fly, and extremely reliable. you cant do much without shifting.

[PMGRACER]

Originally posted by sanddrag
Those bosch gearboxes are pretty fragile from our experiences.

Most of the fast and powerful teams shift these days. It is a necessaty to have a machine that has more than one configuration. The way that the games have a qualifying session and an elimination run, require you to have different strategys to be competitive. Most of the teams who were in the final rounds of the Nationals were bot's with split personality transmissons. To us this extra time and effort seems worth it.

We have been using the Bosch trans for some time now. This year is the first year we decided to shift. We however, decided to shift using servos utilizing the stock housing and shift ring--if anybody watched Team 27 in the pits, they usually saw us constantly going through that silly system! We like the compact size of the planetary system, although they do have more friction than a spur gear style trans.

To avoid the struggle of 2002, 2003 guaruntees we are using a Drag race inspired Air Shifter, also promises a new Aluminum trans housing. A new "Shift Ring" made of steel or brass. A one piece Housing for both the planetary sections and out put. If anyone has seen our trans assembly, then they have seen how we eliminate the clutch. I have all this drawn in AutoCad 14 as a 3D file. If anyone has any questions on how this looks or works I be happy to share some data.

[JVN]

Originally posted by magnasmific
and our matching, patented designed for the chiapuah motors. its shift on the fly, and extremely reliable. you cant do much without shifting.

Did you really patent it? Rock on T3.
Let me know when the FIRST royalties start flowing in.
Of course you'll have to pay 45 for using part of their design...

[Antonio]

I've heard from some of you that change gears refer to the Bosch gearbox, do guys mind telling me what that is, since my team is interested in switching gears for this years competition Thanks!

[sanddrag]

The bosh gearbox is also referred to as the drill motor gearbox. it is pictured below. It has a shifting mechanism that uses a shift lever and two sets of internal planetary gears. High speed gives 1000 rpm and a stall torque of 10Nm and low speed gives 300 rpm and a stall torque of 29 Nm.

www.team696.org/motorspecs.html

[Al Skierkiewicz]

For Rookie Teams...
We should remind everyone of the locking pawl in the drill motor transmission. There is a white paper on this board about how to remove that little tooth. With the locking pawl in place you are almost assured to breakout the transmission case during competition.

[Ken Leung]

Originally posted by Antonio
I've heard from some of you that change gears refer to the Bosch gearbox, do guys mind telling me what that is, since my team is interested in switching gears for this years competition Thanks!

You know how hand drills have a little switch that makes it spin slower but more torque? That's what teams use in the drill motors to shift gears. What you couldn't see in the picture of the drill transmission, is a silver strip of metal that you can move back and forth to select either high gear or low gear. Teams usually use a servo motor for each drill transmission to move that metal strip to switch gears. I know some teams use pneumatics to do that as well.

There are planetary gears inside the drill transmission. The metal strip engage one of the ring gears that slide from one stage of the planetary gears to another. In High gear, that ring gear is in a position where it lock one stage of planetary gears together so that it act like as if that stage doesn't exist. When you switch to lower gear, the ring gear slide out and unlock that stage, adding further reduction to the transmission causing the output shaft to spin with a slower rpm, but higher torque.

Of course, this isn't the only way to do this. There were different transmissions I've seen in the past years, and the technokat's servo transmission is only one of them. There are other ways like
having another set of wheels on your robot with a different gear ratio, and you lower those wheels when you want a different speed/torque combination. I've seen this on 131's 2000 bot, and 258's 2002 bot. Changing wheels size is also a mean of switching gear ratio too.

There are also ones where there are two set of gears on the same shaft, and only one set is engaged at a time, and you use pneumatics to engage the other set of gears for a different ratio. I've seen this on 67's 2001 bot, and 45, 60 and 254's 2002 bot last year.

Then there were other teams who lower another set of drive train with a lower gear ratio, like 111 and 810 last year I believe.

But most teams use the servos to switch gears on the drill transmissions because its fairly easy to do. You just got to figure out a good servo mount on top of the transmissions, and make sure the linkage between the sergo output arm and the metal strip is good enough.

[Antonio]

so, if we used the Bosch gearbox......would that, say, lower our speed or reduce our torque compared to having a gearbox that fully switched gears using pneumatics and stuff like that?? because I'm not sure how powerful these bosch motors would be compared to different gear ratios

[Antonio]

also, how would we design the bosch motor to shift gears, if we were to use it as a shifting motor?? pneumatics?

[Alavinus]

so, if we used the Bosch gearbox......would that, say, lower our speed or reduce our torque compared to having a gearbox that fully switched gears using pneumatics and stuff like that?? because I'm not sure how powerful these Bosch motors would be compared to different gear ratios

It depends on the gearbox design you would use outside of the Bosch transmission. You can also find equations and charts on this site to help you determine the benefits and disadvantages of an external gearbox.

also, how would we design the Bosch motor to shift gears, if we were to use it as a shifting motor?? pneumatics?

Check the previous replies. Some teams use pneumatics, others use the servo motors in the kit. I would also highly recommend that you do a detailed check through the white papers of this site. There are many different designs here, so look around. My team is currently trying out the most recent dual motor transmission design, as it looks very promising.

[Antonio]

thanks for the help Alavinus the white papers helped a lot . However, I'm curious on how some of the gear shifting robots were able to shift on the fly?? how did they make the gears mesh properly? and if they don't mesh properly what are the chances of those gears being destroyed?