Animated pantorouter tradeshow display
Mac Sheldon has started distributing the pantorouters made by Kuldeep. He wanted a display showing a scaled-up animated pantograph to demonstrate how following the template can be used to cut a tenon. He asked me if I could build such a thing so he could show it at the wood show in Baltimore, Jan 2016.
I don't normally take commissions, and there really wasn't a whole lot of time to make this. But it was an interesting challenge and would help to sell pantorouter machines, so I started tinkering around with it.
I took one of the feed roller drive chains from my old thickness planer that I had smashed to build a build a jointer. This chain seemed a reasonable length. It was also the same pitch as a bicycle chain. Some plastic sprockets from the gear shift derailleur were about the right size for what I needed. I could have designed custom sprockets with my gear generator, but cutting sprockets for bicycle chains out of wood is iffy at best.
I welded a piece of metal to one of the links to pull the follower along.
So I thought about what to do about this. Then I had the idea of making the pantograph extend to "below the table", and have the chain mechanism there. That way the chain could be at the same scale as the "tenon" being cut, and the pantograph would scale up to a template that's twice as big.
With the chain mechanism below the table, I could optimize for robustness instead of making it hidden. So I drilled a hole in the strip of metal and shortened it so it will hold the shaft near the chain.
The mechanism pivots on 3/16" diameter shafts. I needed the shaft to turn freely in the links, but not fall out. So for the "inside" layer, I drilled a hole that tightly fit the shaft, and for the outside layer, I drilled it to fit loosely. The tight holes are drilled with a 3/16" metal bit, the loose holes with a 3/16" brad point bit. It's not unusual for metal drills to drill slightly undersized in wood, and brad point bits to drill slightly oversized.
It had a bit of friction between the links. Then I realized, with paint there would be even more friction. So I made the pieces a bit thinner to cut down on friction and leave some room for paint.
I rounded all the inside corners of the "outside" links on my strip sander. That way, when it gets painted eventually, the paint won't get too scuffed up where the links are.
Next, drawing the "router mount" link on some plywood, using my beam compass.
Again, experimenting with balancing. By holding one set of links vertical, I was able to balance the other set of links, then reoriented so the other set of links was vertical, and balanced again. I used some large fender washers, hooked to extra long pins on the pivots to do the fine balance.
This was actually the second base. I initially miscalculated the height so the first base wasn't tall enough. I turned that one into a storage box.
I found the shaft wiggled around a bit too much in my initial assembly, so here I'm adding a bearing block to hold the other end of the shaft. The bearing block has a steel bushing on the inside.
I used my benchtop power supply to provide power, though I later swapped that for a small 7.5 volt wall power adapter.
My box was initially to be held rigid by its sides, but I needed to be able to access the front and back while working on it, so I added some cross members and gussets on the inside to hold it rigid even without the front and back.
I didn't make the chain totally taut, so there was some wiggle room when the chain link with the hook on it is between the sprockets. I added a bearing to the shaft and blocks of wood to constrain it to a straight line.
First test, with a "tenon" template. I put a 1" piece of dowel in the middle of the router link to represent the router bit. By this time, I had also cut out the middle of the router mount link and glued a very thin piece of plywood to the back. This makes it look more like the real pantorouter, but more importantly, it makes it lighter.
Just for good measure, I put some glue in the holes that I put the threaded inserts in, then installed the inserts by driving them in with a long bolt
I drilled some very small holes in the links next to the pins and used paper clips to hook the pins in place. The pins have flat plywood knobs on them and the paperclip hooks to that.
I needed something to hold the template to the template holder frame. I figured, I might as well make this look like the template holder on the actual pantorouter. So I bought a piece of acrylic plastic and drilled a grid of holes in it, just like on the actual machine.
I tested the whole thing on my workbench. I had to make a shorter version of the "operating lever", because the handle extension kept hitting the ceiling.
The pantograph is scaled up two times from the actual machine. A pantograph that size can quickly become unwieldy!
Finally, disassembling it and cramming the whole thing into a shipping crate that I made specially for it. I was just barely able to fit all the pieces into the box. Luckily, I was able to get the pantograph part in without taking the tightly fitting pins out.
Then screwing the lid on, and shipping it off. I was only too happy to finally get it out of my shop!
Update (Jan 14 2016):
Mac completely disassembled the pantograph mechanism for painting and only reassembled it on the tradeshow floor. He mentioned "it didn’t go flawlessly due to my mistake in resembling after painting the parts". No surprise there, I'd put it together backwards a few times myself!
He had the demo running for three days non stop. I'm pleased that it didn't break. I only ran it for maybe 30 minutes total during testing!
Another video from the Baltimore wood show, this one with much better sound, recorded by Mikhail Makarevich. I recorded an introduction for him.
I still have a hard time believing my animated display machine worked the whole length of the show (and still works as far as I know). You can see people taking down the displays in the background in part of the video, and the machine is still running!
Mac Sheldon's YouTube channel
Hybridpantrouter.com - Mac's website