# 17.5 inch linear slides

Titan/Josh (1103) explained his design, and posted this picture, in this post, in this thread.

~Jordan

also this video

The basic principle is that you have “slack” built into the chain system in the form of zig-zagging chaining that is “taken up” by a powered sprocket using something that is fixed to the chain to pull everything up with it. Refer to those diagrams for more information.
Despite being the “old-school” way of powering sliders (the new way being using rack+pinions), using chain can be much more efficient and easier to implement.

1 double extending set of normal length slides give plenty of height when a double extending chain driven lift, we got all the way up to 40 inches max height and Titan made 43. We actually considered just adapting the lift for next wear and it would work well but the biggest issue is we found that over the course of the year we had to keep it very well lubricated and it also became misaligned. If we end up trying it were going to use our mentors granite sizing table and make a jig to re align and re assemble the lift before each competition or maybe during competition to make sure its running good

That would be very useful for this years Vex challenge… I would love to see them come out with 17.5" or 18" linear slides!

How did you connect the slide rails Cryptographer? I think a few well placed triangles might help with that misalignment problem,unless im confused as to what your problem was.

thats what most people have been thinking

this would be a great product for vex to come out with

that would be cool, but I think the vex engineers want us to have to use our brains more than we want to :(

Would somebody please explain to me what’s so great about 17.5" slides?
The limitation for lifts is the size of the robot-12.5" is long enough.
The only reason I can think of to have 17.5" slides is if you are doing a track that needs to go in both directions; for an elevator, you’re only going in one direction, so long slides wouldn’t help.

Well 17.5 in slides would allow for greater distance of motion than the current slides. By that I mean that if you want, say, 15 in. of vertical motion, you have to take a regular set of slide, and then cut another set and make your own set of longer ones. If the slides would be longer than you would not have to do this and it would be more solid. I think longer slides should be made for the same reason that C channel and all other metal comes in longer pieces. I know for a fact that having longer slides would have helped this year for at least (2) of our teams.

I’m aware that a titan lift will get more vertical lift, but I think that using one linear slide motion is more efficient for getting for example 15 in. of vertical motion.

“The limitation for lifts is the size of the robot-12.5” is long enough." - I am not quite sure what you mean by this. The size of the robot is 18 in. I think that a lot of people would disagree with the statement that 12.5 in. slides are long enough.

So there are two ways to solve the problem of lifting vertically 30 inches.

You can lobby Vex to make a part to do it for you, or you can engineer a solution.

ya we engineer solutions all the time. we are not complaining, we are simply saying it would be nice to have. we have engineered solutions (connecting two, creating alternate lifting systems), but they usually all end up at lengthening linear slides. for this purpose it would be much simpler and probably work better to have longer slides

Correct me if I’m wrong but I think there is a way to reach the 30" goal using 4 12" slides. Look at the picture attached. Using the double extended lift with HS chain (think 1103’s robot) this could bring a manipulator to 31" high. The question is if 2 inches of overlap for the slides (when extended) would be sturdy enough.

Any thoughts?

2 inches would probably be enough overlap because a large number of teams use 2 slider sets in parallel for stability. For round up we used a 2 wide first tier and a 1 wide second tier.

That’s what I’m thinking- you would use 4 sets of sliders. 2 parallel for the first stage and 2 parallel for the second, with the HS chain going between.

This is what I mean (sorry for not being clear):
http://img706.imageshack.us/img706/5598/125inch.png
[http://img194.imageshack.us/img194/7035/175inch.png
(Also attached)

Either way, you’re limited by the maximum height (18") of the starting position.
These use a little over 2" for the overlap.](http://img194.imageshack.us/img194/7035/175inch.png)

Our you could just make your own linear slide with c-channel…

[http://img194.imageshack.us/img194/7035/175inch.png
(Also attached)

Either way, you’re limited by the maximum height (18") of the starting position.
These use a little over 2" for the overlap.](http://img194.imageshack.us/img194/7035/175inch.png)

I understand what you are saying, but I am talking about the need for longer slides using a rack and pinion system, not a system like titan’s lift. There are advantages to using a longer rack and pinion is some cases.

Oh sorry then.
Rack and Pinions are harder to make with shorter slides, but the maximum lift height (achieved with chain) would be the same for any size, so different sizes would have different applications (I wouldn’t use 17.5" slides for a chain-powered lift).
I prefer the chain method because it is easier to implement and all the lift motors are in the same place (not being lifted, whereas using racks does require lifting the motors, and hence extending wiring).