Friday, May 3, 2013

Spider Project Part 2

Spiders, Spiders everywhere....in my dreams and underwear.....

Okay, lots of fumbling around in the dark about how to make a cool lightweight spider.
I've searched the interwebs to no avail...it appears that this particular project has not been attempted in this particular way....bummer...

Pictures of the cam and leg mechanism.

Close up of the cams


 The springs are there to help take the weight of the legs off of the cam. They are set so that when the legs are at their lowest they are just barely negatively buoyant.


In the above shots you can see my plywood cams, my cam followers, and my roller bearings! Or, 1/2" grey PVC pre-bends and end caps.
One of the problems in this prototype is that the plywood kinda catches on the edges of the end caps.
The final design will have to have a smooth transition.
That and because the cams are mounted on threaded rod they keep creeping forward when I'm testing.

Yep, plywood, pvc, zipties, threaded rod, nuts and washers. How professional!

Here's a little close up shot of the cams actuating the legs.
video
Remember, this is just a prototype version 1.0. If you can see anything that I could do to improve the action please let me know.

And finally the whole thing moving.
video
Doesn't look to bad right? I think that there is a pretty good amount of movement in the legs. One thing that keeps happening is that the cams all try to 'self align' which makes it really, really hard to turn the crank. I set them up with the two outside cams at 90 deg from each other and the two inside cams 45 deg of off them. In the above video the legs are rigid. I'm thinking that the spider would look a lot better is the legs maybe moved about. I decided to try to hinge the top 90 deg fitting and see if I could get some added movement.

Enter The Hasp
This is super kludgy. This hasp is not a long term solution.

Some bungee cord muscle
And when the leg is in its lowest position the bungee pulls the lower half of the leg up a bit. Not a whole lot of movement.
The right angle is how the leg would look if it was rigid. I don't  know if this much movement is worth the hassle. Leg Moving.
video
Wha da y'all think?

Questions Can anyone see any improvement that can be made? Is the leg movement worth it? How in the heck am I going to go from this and into the real deal? This will be powered with a windshield wiper motor. I still have to figure out how to connect it to what ever shaft the cams will be attached to. What should I make the final cams out of?  

6 comments:

Auntie Sue said...

Wow! I think that's pretty impressive, Mr. MadScientist!

Mom said...

Looks cool!

Jim R said...

Where I work, they would use UHMW sheet to fabricate the cams.
It's looking good.

The MadScientist said...

I was thinking something like UHMW also. A tough self lubing plastic that won't get ground down.

If I could somehow make the followers out of the same stuff I bet it'd be a pretty smooth running system.

Though, how would you attach the plastic cams to the cam shaft? I think I'll have to farm the making of the cams out as I want them to be perfectly shaped. Got any ideas?

JIm R said...

You could use shaft collers to hold the cams in place.

David Whiteley said...

How about making the ends which run on the cams longer so that they don't need so much leverage. Left/right could even overlap so that the end of leg-1-left is on the right of the body, etc. You would then need a cam for each leg.
Jim's reference to a collar might be made from the same leg tubing with notches to engage the cams. A circle of smaller holes in the cams would allow them to be locked via two or more smaller threaded rods.