We started out the morning fired up to build! We had coffee in hand, and a whole bunch of items on our checklist we wanted to get through. We were focusing on parts that need milling, as we wanted to get as much done with the vise aligned as possible before taking if off and moving on to other operations. Click Back after viewing an image.
We're starting out with work on the second version of our hobbyweight drumbot. Here we're sizing up a replacement speed controller for the weapon motor. The original speed controller (bottom) weighs a bit over two ounces and is non-reversible. The replacement speed controller (above) is half the weight and reversible, so we're going to use it in this build.
One of the things we're replacing in the new version is the aluminium weapon motor mount - we're swapping it for a polycarbonate one so save a bit of weight. It took us a good ten minutes to lever the weapon pulley off the weapon motor - it had ground itself into the shaft, but finally gave in to the claw hammer/large screwdriver approach.
To get on, we move over to Milly, and clamp down the two outer walls for the hobbyweight in the vise, intending to mill pockets for the top and bottom plates to sit in. This is the first time we've tried milling aluminium, and need to learn feed rates and spindle speeds. There was a fair bit of chattering going on during this process, but it completed without incident.
The next operation involves slotting the side walls for the internal walls of the 'bot. We ended up missing by a couple of hundredths of a inch - oops - but we'll deal with it!
And here we are with the outer walls milled. Not superb quality, but pretty darned good for a first try, and things will get better the more we practice. Now for the polycarbonate.
Can you see the difference in this photo versus the one before? We've milled a slot in the top and bottom of the front wall for the top and bottom plates. Yeah, gratuitous, but it's our web site :-)
Okay, so here's some progress: we've milled slots in the polycarbonate and can now finally slot the chassis together. Things seem to line up fairly well, so we're happy with it. Time to move on to - yay! - drilling and tapping.
We'll spare you the drilling and tapping pics, so here's the end result: with a couple of small exceptions, we've been able to put a screw in every hole, and the chassis is fairly square - bonus! To fix the missed holes we'll wait for our selection of end mills to show up so we can elongate the bolt holes a fraction.
A parting shot for this 'bot - you can see one of the bolt holes we missed. The observant amongst you will also note that the chassis is upside down. Anyhow, our next steps for Nihilistic Naysayer 2.0 will be making gearboxes and installing the drive train, followed by the weapon drum.
While we had the mill set up we decided to pocket some holes in the legs for our featherweight, because the gap between the legs is only three inches, whereas the wheels have a diameter of 3.125", so we've put some clearance in with a quick bit of milling.
Moving on to another 'bot, and here we're fabricating a weapon bearing for the antweight Poor Punctuation 0.9. We determined a few nights ago that we wanted to make a bearing for the main weapon shaft, so we've cut a bit of UHMW and written a G-code program to cut it out.
After some milling and follow-up drilling/countersinking we had a bearing! It looked good, and fit the chassis well.
After marking and drilling a hole in the base of the bearing we pressed in a 1/4" bearing.
Success! Here we've bored the weapon shaft pulley to a quarter-inch and we're trying out the fit. All seems well at this point, but we wonder how much of our 16 ounces we've used up with the new part.
Hm ... 14.4 ounces so far, without some bolts or weapon teeth ... not looking too bad. But we still have a couple of minor pieces to fabricate.
One of which is a top plate for the bearing, into which we pressed another 1/4" bearing. Note that we've also screwed down the bearing into the chassis, and everything is pretty sturdy. The bearing has given us the clearance we need for the shell to clear the weapon motor pulley, and we're going to press home our productivity advantage by finishing the shell.
The top plate for the bearing has added some weight to the equation, and we're now up to 14.9 ounces, not leaving much for weapon teeth! But that's okay - we weren't planning on huge teeth, and we can still trim some weight out of the chassis.
Now we finally have all the weapon shaft layout completed we drill the shaft and it's pulley for a 1/16" roll pin.
Here we've inserted the roll pin and trimmed it with the Dremel to leave a grab-able length that won't get in the way of the operation of the shaft and belt.
Here we're tapping the top of the shell to fix the shell ring to the top using #6-32 screws.
Ta-daa! The only thing left (other than the teeth) is some way to couple the shell to the weapon shaft. Before we do this, we stuck everything back on the scale, and we're now up to 15.0 ounces, so we need to start to think about trimming weight to maximise the size of the shell teeth.
The coupler is a ver simple piece of drilled and tapped 1" x 1" x 1/8" aluminium, and we're pretty happy with how it came out. There are four #6-32 screws holding the shell to the coupler, and a 1/16" roll pin holding the coupler to the shaft. The only thing left to do now is trim down the weapon shaft, and hopefully save a bit of weight in doing so.
With the coupler, but without trimming the shaft, we're now up to 15.2 ounces. We'll probably use a fraction of an ounce mounting the electronics tomorrow, so we're guessing we'll have a touch more than a half of an ounce to make teeth with. Not a lot, but hopefully enough.
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