pic: 3 speed concept - 1st gear

[dubious elise]

I think it will be more powerful than the three-speed in my car...

[sanddrag]

Originally Posted by dubious elise

I think it will be more powerful than the three-speed in my car...

Given the way we build gearboxes you might be correct. but not really, I think if a first robot used all the motors combined you'd still be under 5HP.

Originally Posted by Kevin Sevcik

I'd have to make a drawing to show you what I'm talking about, I think. Lathing the gear would get you something looking exactly like if you'd done the same thing with a rod or other cylinder. I'm talking about beveling each individual edge of each tooth.

The point of this is to reduce the cross-section that has to mesh.

I know exactly what you mean now. That's probably not a bad idea. I've seen a lot of meshing transmissions out there and they all seem to work okay. I wonder what teams like 254 or 60 do to their gearboxes to make them shift well. I've been looking at this one I wonder if they added c-c distance or beveled the gears or just left them.

I like mesh shifters because they are easier to construct, but what I don't like is that in every single one I've seen there are metal shavings inside it like this. The gears themselves have always looked fine, but metal shavings in gearboxes make me uncomfortable.

Anyway, I thought about a dog shifting 3 speed, but determined that there is not good way to do it, where there is a pretty good way with mesh shifting.

[Cory]

Of course you're going to have metal shavings in there--you're smashing two metal objects together at high speeds, which is going to wear down the teeth and leave shavings in there.

They seem to run pretty well, regardless of what is or isn't in em, so it doesn't seem like a real issue

[David Guzman]

I have always wonder about this kind of shifting, how long can a gear box like this last?

I had this idea a while ago but I didn't think it would work because of the gears hiting when shifting. What do you all think about using brass for one of the gears that meshes and steel for the other one. I think since brass is a softer metal it would start to take the shape needed to shift properly.

I know there was a team that use this method and had four speeds, i think it was team 33 but im not sure? someone please correct me if wrong.

Dave

[Arefin Bari]

Originally Posted by David Guzman

I have always wonder about this kind of shifting, how long can a gear box like this last?

I had this idea a while ago but I didn't think it would work because of the gears hiting when shifting. What do you all think about using brass for one of the gears that meshes and steel for the other one. I think since brass is a softer metal it would start to take the shape needed to shift properly.

I know there was a team that use this method and had four speeds, i think it was team 33 but im not sure? someone please correct me if wrong.

Dave

When you build a robot for FIRST you really want the gearbox to last the season. There has been mesh gearbox made before and used in FIRST which lasted longer.

The best way to do this is by beveling the gear teeth edges so it would mesh properly. Personally I would 20 dp gears. If you do use brass, I fear that the teeth will sheer off.

Yes it was team 33 who has done the 4 speed back in 2004 and they used mesh shifting. It was very cool. Team 195 also used something like 33's 2004 tranmission this past season.

[Cory]

Originally Posted by David Guzman

I have always wonder about this kind of shifting, how long can a gear box like this last?

I had this idea a while ago but I didn't think it would work because of the gears hiting when shifting. What do you all think about using brass for one of the gears that meshes and steel for the other one. I think since brass is a softer metal it would start to take the shape needed to shift properly.

I know there was a team that use this method and had four speeds, i think it was team 33 but im not sure? someone please correct me if wrong.

Dave

Teams have been using this style of shifting for quite some time, and overall, when constructed properly, it seems to be extremely reliable. I suppose if you shift a whole lot, you may need to have extras of the meshing gears on hand, incase you happen to shear a tooth, or completely wear them down, but considering that a team who attends 4 events (2 regionals, nats, an offseason. Yes I know many teams go to more than this), with an average of 10 rounds per event, that's only 80 minutes of drive time, which should be well within the lifespan of most things built for FIRST.

[sanddrag]

Originally Posted by Cory

Teams have been using this style of shifting for quite some time, and overall, when constructed properly, it seems to be extremely reliable. I suppose if you shift a whole lot, you may need to have extras of the meshing gears on hand, incase you happen to shear a tooth, or completely wear them down, but considering that a team who attends 4 events (2 regionals, nats, an offseason. Yes I know many teams go to more than this), with an average of 10 rounds per event, that's only 80 minutes of drive time, which should be well within the lifespan of most things built for FIRST.

I would agree. It's like one of those things that shouldn't work but does. I will note that as SVR I know 254 was having a good bit of trouble with it (I think it was Friday evening), but I don't know what it was caused by. So it wouldn't be fair to say mesh shifters are inherently troublesome. I don't think the design is nearly as robust as a constant mesh dog shifter, but there is no evidence to suggest that a mesh shifter is not robust enough for it's use. I don't like how mesh shifters work, but you can't deny the fact that they do work, and seemingly pretty well.

I have a couple questions. Do mesh shifters prefer to be shifted under speed and load? I know the dog shifters just love it, but I'm thinking the mesh shifters might like a slower easier shift.

Can someone who has driven one enlighten us?

[Bill Gold]

Originally Posted by sanddrag

I wonder what teams like 254 or 60 do to their gearboxes to make them shift well. I've been looking at this one I wonder if they added c-c distance or beveled the gears or just left them.

In our 2005 drive transmissions we added a little in the center-to-center distance (off the top of my head I think it was 0.0015", but I can check on that if you'd want) and chamfered the shifting gears.

Also, we didn't care how fast we were running the transmissions when we shifted. Our problems on Friday at SVR weren't related to the gears themselves. There were minor problems within the transmission related to snap-rings. We had no other mechanical issues after fixing that problem (which originated in Sacramento) for the rest of the season.