pic: what do you think?

[JVN]

Seems like after all that hassle, it would just be easier to do a 4-speed similar to 33, or 968. (I'm especially partial to 968, but it is more difficult to manufacture than 33's).

Then again, I've found no need for more than 2 speeds.
You can get along fine with just 2, more is overkill.

John

[Tom Bottiglieri]

Originally Posted by JVN

Seems like after all that hassle, it would just be easier to do a 4-speed similar to 33, or 968. (I'm especially partial to 968, but it is more difficult to manufacture than 33's).

Then again, I've found no need for more than 2 speeds.
You can get along fine with just 2, more is overkill.

John

Well If you go for 2 speeds, your probably going to have a manual tranny set up where the driver switches speeds as needed. Going more than 2 implies you are going to have an automatic that switches accoring to speed and load. (See: Team 33)

Either one works, but a 4 speed gives a hungry programmer more to work on

[RogerR]

before you take my advice, realize that i'm not an expert (yet... )

it would apearr that there isn't enough space between the gears that are being shifted. i would say you need at least double the face width of the stationary
gears, otherwise you would end up engaging two different gearsets in mid-shift.

then again, i didn't see anything saying that this drawing was to scale, so this might be a non issue.

[sburro]

Originally Posted by RogerR

before you take my advice, realize that i'm not an expert (yet... )

it would apearr that there isn't enough space between the gears that are being shifted. i would say you need at least double the face width of the stationary
gears, otherwise you would end up engaging two different gearsets in mid-shift.

then again, i didn't see anything saying that this drawing was to scale, so this might be a non issue.

you are right, it is not to scale, but as aI said, a work in progress. I figured a team would use at most three gears, a "speed gear", a "tourque gear" and a "driving Gear" for normal use. our past robots just used the drill motors. I have been in First for one yaer now and I cannot stop thinking about it .
The gears that are on the piston are attached to the same rod.

[Kevin Sevcik]

We used a similar design for a simple 2 speed tranny this year. We also had no problems at all shifting on the fly, but we ground the outsides of the gears to points so that the would mesh better. I will say that you need to be very careful about the size, pitch, strength, etc of your gears, as it's easier than you think to strip them.

Also, I'm also questioning the need of 3 gears, when you only really need a pushing and driving gear. I'm doubting that a mid-range would really help the acceleration of your robot THAT much, considering how short the field is, and how hard it is to make a turn at full speed.

That being said, I was thinking of a way to accurately shift one of these cylinders half way. I was thinking of using a split system of pneumatics with 60 psi and ~30 psi. shifting full distance would involve flooding one side with 60 psi. to shift half way, you lower the pressure on the extended side to a little more than 30 psi, then flood the other side with 60psi. Then P1V1=P2V2 does all the complicated positioning for you. The valve system would be complicated and/or impossible. I haven't looked into that yet. but it should work in theory, atleast.

[Veselin Kolev]

Here's what I think.
If you want to just go for the design, meaning make it even though you probably will never use it, awsome. I think you're just going for a challenge, which is great. As for the mechanical part of it...

Sure, it looks like it'll work and all, if you get the right gear ratios, etc... but I myself have 2 "major"issues with this form of 3 speed. You notice that the spacing on the 3rd gear is a lot larger than for the first 2 gears. That is necesary to clear the first two from engaging, but it eats up space. Second, you are literally using the gear teeth as a shifting medium. Sure, cars do it too, but cars have syncros. Sure, other teams do it a lot, but I look at their gears by the end of the season and they are worn out a lot. For robotics purposes, sure it works. For anything else, I would look for a different method.
If you get a flexible coupler on the output shaft of this transmission so it takes the forces of shifting, your gears will probably be fine. Just look up "lovejoy" couplers online if you want an example of one.

If you're interested in slick transmissions, check out the white paper on the Technokats 2003 tranny. It's a two speed, but, as we've seen from other teams, it can be modified to be much more.

Other than that, this concept can work easily. Cool idea!

[Phil 33]

Are there any pictures/specifications about the killker bees transmission.

The design is being drawn up in CAD, and the code to make the transmission automated is being perfected. Before next season however, we will have CAD drawings, code, design details, etc.

i think that this might be problematic when it comes to meshing the gears

We had almost no problems with this. As Andy said, take the spot where the gears fit together perfectly, and move the center of the shafts apart 0.0015'' and its enough to allow the gears to mesh nicely. I believe we also originally filed the edges of the gears a bit to make them mesh a little better. Also, be sure to heat treat the steel gears to harden them which will reduce grinding. Making the gears a bit wider so they have more contact surface area also helps some.