Friday, January 29, 2010

Drive System 4

Did a bunch of work on the drive system today.  I finally had all the parts in hand, so I could move forward without stalling.  Most of the day was spent modifying, cutting, trimming, drilling, and filing all the pieces to get them all to fit together right.  I got the foot shells off of the R2 and checked the fit.  It turns out that there's not much width in there, so I needed to reduce the width of the frames.  That meant moving the side plates to the inside of the lip instead of the outside of the lip on the top plate.  The wheels have wider hubs than the treads, so I used the band saw and sander to trim those down to have a narrower profile:

Once the wheels were trimmed down, I could get the axles and bushing in there and start cutting the chains and getting all the gears set up.  This all went pretty well.  It looks like I won't need an idle gear on this side.  The chain is just right for snugness here.
Getting the other side with the motor bracket, gear, chain and motor all cut and sized right was tricky.  I used some carriage head bolts on the inside there for a low profile. That way the bolt heads holding the bracket on don't interfere with the motor gear.

There are several little things to do here.  The inserts need to be tightened up and secured with a small screw.  The axles need to be cut to a miminal length.  And some of the bolts haven't been put in there.  It took me a little while to get everything lined up and get smooth rolling action on the wheels.  But it seems to work well now.

Very beefy.  Notice that I cut the lip off of the top plate on the frame so that the motor bracket would sit in there flush to the side plate.  To get the motor to line up where it should go up inside the battery boxes, I needed to get it shifted in closer to the frame.  More on that in a minute.

I still haven't cut the outside axle off here.  And I used my old drive frames to map the holes on top where the threaded rods from the legs come down.  So far it looks like all of this fits pretty well into the foot shells and onto the legs.  Some other views:

I had to do some work on the foot shell for the bracket to fit through the hole into the battery box.  Cut the holes much bigger.

The battery boxes are going to be a problem.  With the bracket, the motors stick out a lot.  The outside width of the motors is about  2.5 inches.  My battery boxes are made with PVC pipe that's about 2.9 inches wide on the outside.  So the interior space with .25" side walls is 2.4.  That is, the motors won't really fit inside the battery boxes.  For now I'm going to get these motors all assembled and installed without the battery boxes.  I can think of a couple of possible fixes for the battery boxes.  1) I could cut out the whole back side of these, and then add a pieces of 1/8" PVC cell board across the back to increase the interior volume.  Then I could build up the curved sections to blend in with the box with body putty or something.  That would take quite a bit of work.  2)  I could make some new battery boxes with the next size up of PVC pipe.  The problem is that the next size up is 3.5" O.D.  The plans call for the battery boxes to be 3" wide exactly, so that would be a pretty big fudge.  You'd be able to see how fat those were right away.  But the inside diameter would then be 3.042" which would be plenty to house the NPC motors.  I'll think about it some more.  I don't think this will be too hard to solve, but I will probable have to effectively rebuild my battery boxes.  Fortunately, since I have been selling those, I have several of them around and I can build them quickly.

And here's a video of the bench test of the motor all mounting into the drive system.  Works well.  I am going to try to take the half link out of the chain on the motor gear.

1 comment:

Victor Franco said...

Looking good! I know from experience this is a lot of effort, so kudos.

Regarding the fit inside the battery boxes, it is a very tight squeeze for me. I filed down the corners of the motor tops, and sanded down some of the interior of my PVC battery boxes from Craig Smith.

Senna actually has the very bottom of his drivetrain exposed through a cut on the bottom of his battery boxes, but you pretty much have to get on your hands and knees to see it.

Keep up the good work,