LumberJocks Woodworking Forum banner
  • Please post in our Community Feedback thread for help with the new forum software! If you are having trouble logging in, please Contact Us for assistance.

Project Information

I was given the opportunity to bid on the fabrication of two BIG variable pitch columns that were to be 13.35" dia X 96" high. The architectural firm that asked for the quote told me that they had found only two other wood turners in the United States that could (or would!) fabricate a varied pitch structural column, one in Texas and the other in Massachusetts. The architects were based in Pasadena, CA only 18 miles from me, and the house site where these would be used was in Laguna Nigel, CA, about 60 miles away…they said they'd like to keep the work local if possible.

I had no idea how to accomplish this, to make a single lead barley twist that made a complete turn in 18" of length at the bottom and then gradually tightened the lead until it was 12" for a complete turn at the top. I did a logical thing: I quoted a price that would cover me if I had to do it all by hand, $2,500.00.

I had lots of lead time (which I mostly spent scratching my head trying to figure out how I could make my lathe do this job!). I called in my 'Brain Trust' which consisted of Gary (contractor) Bill (electrician), Skip (plumber) and JJ (framer), bought a couple case of beer and figured together we could hit on a solution. At the end of the (fun!) brain storming session we'd come up with some great ideas…which, unfortunately, did not include a solution to my dilemma. A couple days later I woke up in the middle of the night with a really preposterous idea that might be the answer. Twenty four hours later I had a viable solution, and turned a 1/2 scale model to test it. (The Luxor Surprise was made from that model, see that project).

My son Steve III (he's the BIG guy in the first photo and indespensible to this operation!) and I had fun putting this altogerher, with a few whiles of OMGs. The 12 part glue-up was challenging all by itself and the turnings (which were done incrementally) each took approximately 200 passes.

When we delivered to the job site we discovered that the 4" steel columns in the house that were supposed to be inside of our columns were already in place…no provision to get our Twisted Sisters installed around them. Their bad, not ours, and the architectural firm asked us to do two more as split turnings, that could be installed around the 4" steel posts already holding up a mezzanine in the house. We popped them out within a few days and delivered. Four columns = $10,000.00, 2 weeks work. No harm, no foul (at least not by us!). By the way, in at least of one of the in progress photos you can see the pneumatic bag sander on a flexible shaft used to clean up tool marks on this kind of turning.

The last photo here show the nuts and bolts of my solution. And, incidentally, I made the aluminum parts (Indexer varied Spool 4.325" dia, Driver Spool and Idler Spools) on my wood pattern makers Imperial lathe also.

In the last photo I show my solution to the variable pitch problem. Starting from the bottom: this is the Driver Cylinder, it is 2" diameter X 6" long and has 'threads' which are actually grooves to hold 7 turns of a vinyl coated aircraft cable (if you look really close you can see the cable, even in this poor polaroid shot). The next bar up is simply a Brace to hold the outboard end of the Driver Cylinder. The next up is a 1" bar holding 2 individual Idler Spools (they are turned by the cable passing them, in opposing directions) used to separate the two cables and provide tension on the cables. The top narrow waisted spool is the Indexer Spool (72 divisions on the left end, 4" diameter at the ends tapering to 2" diameter in the center; the grooves on the slanted part are left handed and right handed) and this is the mechanism that makes the varied pitch possible. It happens in this way: The Driver Cylinder (bottom) is geared to the carriage travel of the lathe (which holds the cutter) and turns at a constant speed; it moves the cable (that is wound around it) past the Idler Spools to the Indexer Spool, where it is wound up on the right and unwound on the left. The varying diameter of the Indexer Spool turns the work piece (the column) at a constantly faster speed as the cutter traverses the length of the work piece at a set speed.
The actual indexing was manual (operator moved it one of the 72 divisions each pass) and the depth of cut was incremental (36 divisions for the total 3" depth of cut, moved one increment each pass. Each column had approximately 175-200 passes of the cutter, each pass 84". The only way I kept it straight was to have a clipboard and log each pass. Don't worry if this 'solution' isn't readily apparent to you…I still have to stop and think it through each time I contemplate it. Fact: the key to moving the cutter at the correct feed rate was keyed exactly to the diameter (changing diameter) of the Indexer Spool. The 4" to 2" wasn't super critical though since I could make a gross feed rate change by changing sprokets at the carriage feed motor point. However, the number of turns on that spool was critical; I learned more math figuring this out than I ever learned in school!

Gallery

Comments

·
Registered
Joined
·
1,192 Posts
INCREDIBLE!!
 

·
Registered
Joined
·
14,490 Posts
fun read and a cool look in to another woodworkers domain
 

·
Registered
Joined
·
10,899 Posts
great work :)
I hope you got paid than twice for the doubble work

thank´s for sharing

Dennis
 

·
Registered
Joined
·
1,656 Posts
Interesting and challenging work! Well done, Stephen. The word "impossible" does not exist in the creative woodworkers vocabulary!
 

·
Registered
Joined
·
4,440 Posts
Thanks for the post Stephen, I think seeing professionals work here on LJ's helps us amatures raise our own bar a little higher.
Nice job on the columns by the way it would have been a pretty meaty project
 

·
Registered
Joined
·
2,281 Posts
Those are so cool! I would like to see them in the house when it was ready to move into. Any pictures of that? Keep up the good work, is that you in photo #5?
 

·
Registered
Joined
·
229 Posts
Thanks for the nods everybody!

Dennis, Yup, got $2,500 each for four, total $10,000. Funny note, about a year later I saw the first two in an antique shop, they were tagged $5,000 each!

Darrell, No pictures of the completed installation. They were for a sea side home near Newport, CA.
 

·
Registered
Joined
·
437 Posts
Definitely a great build and good story. I agree with peteg that these glimpses at what is possible with wood help to raise the bar on what we should expect to be able to do.

Of course, by the same token it's a consistent reminder that there's always someone better out there.

Thanks for the story.
 

·
Premium Member
Joined
·
25,660 Posts
Interesting project for sure. Congrats on getting it done ;-)
 

·
Registered
Joined
·
3,191 Posts
Terrific Work Stephen!!
 

·
Registered
Joined
·
1,442 Posts
That was a fun description to read and attempt to follow, a little beyond my present capabilities. Thanks for sharing this with us, I know I enjoyed the read.
 

·
Registered
Joined
·
3 Posts
Hi, This is Stephen's son, I remember delivering the second set to the home as it was being build. The house was very much through most of the build, drywall was up and in a very large entry to another room were two round metal poles, floor to ceiling at the far left and right of the entry. Here I was, alone, dropping off these two amazing pieces of art work and one thing I really remember were the construction workers could have really cared less, lol. I guess this might have been one of "those" builds. The other thing I kind of remember was that though in a "nice neighborhood near the beach" it wasn't anything HOLY COW, look at this mansion! Interesting times for sure…

Steve III
 

·
Premium Member
Joined
·
25,660 Posts
Unless they were turners, they probalby had no appreciation of what they were, just a nother piece of the puzzle.
 

·
Registered
Joined
·
893 Posts
awesome story, even more awesome work!
 
Top