Intro: Fly Ball Rotisserie
Twenty Years ago my friend Roman came to me to design a rotisserie he could take on a canoe trip. He wanted a water wheel that could turn a turkey over the camp fire. Then I asked which river he was camping on. Roman said "Lake Marion"! I said lakes have no water current, we need to provide a different power source.
So this is what we came up with: A Fly Ball Escapement, as seen on fancy mantle clocks. Except we used broom sticks, plywood, PVC pipe and dowels from a laundry drying rack. The drive power comes from a bucket filled with sand or firewood.
I've also fixed the two extra videos. 11-30-2016
Step 1: Basic Construction
So I started with the small pinion gear. Two circles of 3/4" plywood about 5" in diameter, I put a hole in the center for a broom stick and 8 holes around the edge for dowels cut from a laundry drying rack. The dowels were glued in, but to lock the disks to the broom stick I drove in wood screws on a angle from the disk into the broom stick.
Next was the big gear, I measured the spacing of the dowels on the pinion gear and calculated a circle for the big gear. It goes like this: dowel spacing x number of dowels / pi ( 3.14 or 22/7 is OK ). So I cut the big disk from 3/4" plywood about 18" in diameter and drilled all the holes. We needed a drum for the power rope so I needed to connect a piece of PVC pipe. To lock this to the gear and the I cut two small disks to fit inside the pipe, one for each end. Then a medium size disk for the other end of the drum and I was all set. A bunch of screws to lock the pipe to the disks and some diagonal screws to lock everything to the second broom stick.
I made a frame from 2x4s drilling the holes off center so the two broom sticks could pass each other. The horizontal broom stick went clear through the vertical 2x4s. The vertical broom stick with the pinion gear rests in a blind hole in the lower horizontal 2x4 and goes through a hole in the top 2x4.
Now this is the neat part, the fly ball. On the pinion gear broom stick I added an arm to hold the fly ball with a light rope. To make this adjustable I made the broom stick hole tight and added a clamping slit with a locking screw. I started using a 3/4" steel nut for a ball. After it hit me up the side of my head, I replace it with a rubber crutch tip. Then the fly ball needs a post to wrap around so I put another dowel in the 2x4 frame. I found this let the turkey rotate too fast so I added an arm for a second dowel and this seemed to work OK. This was all tested in my workshop.
Step 2: Set It Up Over the Fire
So the lower ends of the 2x4s go in holes in the ground, or screwed to a temporary base. A broom stick goes through the turkey. We used some wire and hose clamps to keep the turkey secured from spinning. A section of PVC pipe with slits fits over the broom sticks and clamps the turkey stick to the big gear stick. Then a rope is wound around the PVC drum then routed up a tree or something high. A 5 gallon bucket is weighted with sand or firewood until everything starts to spin. Depending on how far the bucket can fall will determine the run time. Then the other end is also tied to the PVC drum so as one end unwinds the other end is wound back on. So when one end is spend, just tie the bucket so it pulls the other way and the turkey will spin the other way. To keep the heat on the turkey Roman made an aluminum foil tent to cover the top. It takes about 4 or 5 hours to roast the turkey.
The guests are always amazed to watch it run and run. Roman has used this rotisserie four times in the last 20 years and I finally saw it cook a turkey last Saturday!
So have fun if you build one and let me know how it works!
Take care, Carl.