The Millwright’s Apprentice

Tools of the Trade: Rule and Compass Part 2
26
Apr

Tools of the Trade: Rule and Compass Part 2

To continue from yesterday’s post, we’ll discuss how we applied these same geometrical concepts to lay out our new water wheel. One of the beauties of compass geometry is its scalability; so long as you’re able to make a compass large enough, the techniques remain the same.

To lay out our wheel, we needed a flat, preferably level, surface. Normally this would be the floor of the shop.[1]

However, our mill’s floor warps significantly with the seasons. We had to come up with a different method and, as usual, history offered us a solution.

This is a photo of the water wheel at Mabry Mill (Part of the Blue Ridge Parkway National Park) being rebuilt in 1942.[2] The millwrights built a level surface with posts driven into the ground around the circumference of their wheel. This allowed the workers to both lay out and build the wheel at a comfortable working height and on a level surface.

We recreated this in our shop with a series of 8 stands built by both staff and volunteers.

Once these were completed, we laid out sheets of ⅛” plywood in a rough octagon. We later realized this was too flimsy for the kind of work we’d be doing, so we replaced it with 1 ½”thick Douglas fir panels.

To lay out the wheel we created a large beam compass, with one section pinned to a center post.

To lay out the wheel we created a large beam compass, with one section pinned to a center post.

With this we scribed the outer and inner circumferences. Finally we had a 15 ½’ wheel to work with.

Using a chalk line, we struck the centerline for the wheel. Then using the beam compass, we followed the same process we did in the last post, continually dividing a section in half until we had 8 equal parts.

Then using the beam compass, we followed the same process we did in the last post, continually dividing a section in half until we had 8 equal parts.

Finally, to lay out our bucket boards, we stepped out 7 divisions of one of the 8 sections. We used a smaller beam compass to do this, approximated the distance we needed, and stepped out across the outer circumference of the wheel section.

We used a smaller beam compass

We then adjusted slightly until we had exactly seven divisions across the section.

we had exactly seven divisions

Next we walked out across the whole wheel, which gave us our bucket locations.

Next we walked out across the whole whee

Now we just have to finish building it!

Again, I would normally invite everyone to come visit us in the Millwright Shop, but it’s currently closed due to COVID-19. We will be continuing to post here on the blog, and we’ll be doing more Facebook Live videos, so be sure to follow us on Facebook. Stay safe, and check back here next week!

If you’d like to take the next step and get involved in the shop once this has all calmed, please contact us at:

Email: info@newlingristmill.org

Telephone: 610.459.2359

Find us on Instagram @newlingristmill1704

Look for us on Facebook @newlingristmill

Notes

[1] Greenbank Mill waterwheel construction 1998-1999, image courtesy of Tony Shahan.

[2] Blue Ridge Parkway National Park, “Challenges,” Mabry Mill – Milepost 176, Burks Fork, Virginia.

Bibliography

Blue Ridge Parkway National Park, “Challenges,” Mabry Mill – Milepost 176, Burks Fork, Virginia.

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Newlin Grist Mill’s trails are open!

There are a few changes you need to be aware of before you visit:

  1. Open hours are 7am to 5pm. New gates have been installed at the entrance to Newlin Grist Mill. These gates will be unlocked at 7am and locked at 5pm daily. Please keep this in mind when visiting the park.
  2. Repair work is ongoing and not all trails are currently open. While the worst of the damage has been repaired, use caution and please be mindful of marked trails that remain closed while repairs continue.
  3. The parking lot by the log cabin will remain closed or partially blocked off, as we continue to work on completing repairs.
  4. Restrooms, visitor center, and historic buildings are still closed. Please be patient as we work to rebuild the visitor center and make repairs to our historic buildings.
  5. Please be respectful of our staff and volunteers as they work on repairs throughout the park.