Linear Lift Bowing?

Hello there. For our robot we are using a linear lift and I have a question. When the lift gets to the top, how do you deal with the inward bowing caused by the weight of the box+game objects. So far we have not attached motors( we are tomorrow) and i’m not sure if adding the HS chain will affect anything. Thanks for the help, 1028B.

Link for picture- http://i.imgur.com/Gdhre.jpg

Looks to me as if you might be over extending it, this allows the entire structure to bow more than it normally should, and sometimes… that can be a bit scary… our arm was like that for a bit until I finally got around to machining the parts to final spec. Now its bows maybe half an inch a absolute full extension.

It also could be the Cantilever, I know VEX parts tend to not handle it to well if not done correctly.

Food for thought,

  • Andrew

How did you go about machining the parts? I’d love to know so we could try something to reduce the outward bowing. Is there maybe a way you could make a device to keep it straight? Do you think it would be a problem if it bowed out like this?

Well I didn’t use the linear slides of any sort (College team) But I would at least support the first stage a little bit more, so it doesn’t have the tendency to tip. As for the other stages, From the picture it looks to me as if you need to have them lower just a smidge and it shouldn’t wobble as much. It looks as if your getting close to actually having the slides run out of each other.

  • Andrew

I may not exactly understand your question. But our lift did have a bit of canting when it was fully extended. We just angled the lift back about 5 degrees and this ensured the lift stayed relatively straight the entire length.

Sorry about that, I was a bit tired when I typed that. You essentially answered the question. How did you angle the lift back? I’m such a newbie with this sorry.

Ah no problem lol, just didn’t want to give a totally irrelevant answer. On our elevator base (the bottom of the first stage) we just installed it so that whole superstructure was leaning back a tiny bit. And then we kept and overlap of the sliders at the bare minimum one inch (this is with the old sliders).

Regardless of whether you are building a VEX robot or a real life forklift, a good rule of thumb for linear bearings is to maintain a minimum of 20% overlap between the two stages to avoid excessive bowing/deflection.

For example, if your linear bearing stages are ten inches long, you should always have at least two inches of overlap to avoid excessive deflection.