New Frame

new frame

Well after a long "quiet" period in the mascot activities, we've begun to make some new changes to the design. On the previous RBNO, Mike Lynch brought in some new castors and a couple were added to the CAD files. (you can see one of them here)

Previous attempts to intrest the group in using an "umbrella" baby stroller for the frame, failed. Although this design was light and "ready made", perhaps it was percieved as, well, baby stuff.

So we've got a new frame design, based on the previous design, using 1" square steel tubing and flat plate. The motors were re-oriented to take advantage of the boss cast into the motors (that prevent them from turning around the shaft). The location of the castor wheels were widened for stability. I've included PDF drawings of the frame parts here:

The units are in decimal inches and disregard the 3 decimal places.

gusset
frame01
frame02
frame03

If you're not familiar with machinists tapes, a decimal inch is divided into 10ths instead of the archictural 1/4qtrs, 1/8ths, and 16ths. The first decimal place is 10ths of an inch, the second is 100ths, the 3rd 1000ths. You can ignore the 3rd decimal place for our purposes.

Slide Actuation for Height

accuride 3601 - 28

During the discussion about gaining height and adding "transformer" style unfolding, Dale Heatherington mentioned using drawer slides. I managed to find sample slides from Accuride, they donated model 3601 which is one of their heaviest slides. Two of them will hold 273 lbs and move smothly. I propose using just one of them for the mascot as they are so heavy and strong. There are other offers of slides in the wings and I hope they are better for our purpose, because of the 3601's weight. See the specs , 3601, web

The extended length is 57" and the closed length is 28".

Base with 3601 slide

base with slide

This image shows the base with the slide extended. It reaches 69" tall. All of the extension would not be available after adding a ball screw type extender so this example is exaggerated in height by 4 to 6". Still, five plus feet is an impressive height. And that doesn't include a head.

3601 Slide Closed

3601 slide closed

The size of the closed bot with the new slide bothered me some. The bounding box shows the total envelope as 9x28x22. Would someone measure their trunk and report if this is too big?

There's also a problem with the distance between the motors. The slide wont pass between them when closing. The interference is about 1/4". I'll have to double check the models with the actual motors to see if I left myself any spare. As I recall, the motor connectors are in the rear area, and wiring space will be needed there. We might be able to widen the frame an inch to accomodate this problem. As you will recall, we set the width to be 24" in order to pass through the smallest doors. Standard doors are 28" with 26" being a small door and 32" a large door for moving furniture through and such.

Max Headroom

maximum space for head

When the bounding box is added to the extended slide, and shortened to fit around the motors when closed, the image above shows the results. There is space for torso bracing. I'll address that after feedback on this current design comes in. My biggest concern about this design is it's weight. I coudn't say at this point if it's going to be closer to 50lbs or 100lbs. If we change to aluminum, we'll be alot happier with the weight, but welding aluminum is a very different animal, and I don't have a volunteer. The slide is steel and very heavy. I'm not aware of any aluminum slides. Perhaps we should follow Dale and Eric's leads and start using more wood and plastic. It wouldn't be a disaster if we wound up with a heavy bot. We can always make another one. We should avoid this error however if we can. Please comment and I'll adjust the design according to your feedback.

model / sketch overlay

This is a crude overlay example from the sketches we created earlier. This provides some visual cues to help visualise the finished shape for the Mascot.