Could anyone give me some answers to the following questions concerning the expansion of white oak timber, or how we could evaluate how much a 12" diameter turned white oak shaft would expand after turning, and it being subjected to continuous water conditions. The timber presently is not turned but in the rough form ready for turning. Historic cast iron collars will be snugly fit over the turned sections and become parts of a very early barrel wheel water turbine. No moisture tests yet have been made on the timber but I would like some input on proper proceedure that need to be taken to identify its present moisture state, and then apply it to future expansion. It appears like the timber has been cut for about 2 years and been in curing storage. Our problem is that We need some expansion to really seat the collars in place, but not too much to crack them.--Help please

If you have a sample of the cut log in cross section measure it very carefully. Boil the section sample for 4 hours or more which will artificially inflate the wood to its probable max in any water exposure environment short of total immersion. Measure the boiled result and you have your worst case answer.

Richard –

Some thoughts here which do not answer your question directly, but hopefully may help in your decision making.

White oak is notorious in the time needed to reach a “cured” state. The same cell structure that is part of why it is so rot resistant is also why it holds so tight its own moisture. In scantlings above say 12/4 it will not even dry in the kiln at a rate considered efficient.

I once milled a very large piece of white for one of Mr. Krickers mill projects which had been set aside for years waiting for just the right end use and prior to setting under cover all that time it had stood as standing dead for perhaps a greater number of years, and mere inches from the surface it was a green as green can be.

Your twelve inch cant drying but two years has not shrunken appreciably at all and any portion of it that has will be lost in the turning, nor will it reliably expand when immersed.

I have successfully fitted iron collars to dry timber but this is perhaps a situation where those you are following may have fit the originals like a wheelwright fits a tire, expanding the collar in a bed of coals and then hurriedly seating and quenching for a shrink fit.

My thanks to both of you for your input. In historic mill work it seems that you always run across problems that necessitate input from many sources.
I was thinking of doing what you suggest Emmet cutting a section, turning and then immersing, measuring and documenting expansion. But in my mind how much expansion is too much?, and how much expansive pressure will the casting take before failure.
And Will Your reply had some good information and carried on from Emmets's remark left off, concerning the rate of drying, and that the turning would remove some of the already dried outer layers. I was also interested in your reference to the timber cut for Mr. Kricker's mill project, and the fact that it was still quite green on the inside after a lengthy storage period. Your seemingly solid remark that the timber would not expand appreciably upon coming in contact with a considerably moist environment I appreciate and will consider over the next while as I ponder my next move.
What I will share with both of you now is that I manufactured a new shaft about 30 years ago using green oak being very fearful of expansive forces on the collars. I found that there didn't seem to be enough expansion to seat the collars properly, and they eventually wore loose and caused a deterioration of the seating. this time around I would like to improve my methods but I didn't want to move too far to the left as far as the cured timber is concerned. It seems that the timber that I have may be just right, and I take my hat off to both of you for helping with the decision. I also invite more suggestions and conversation on the subject.

I just thought that I would update this site with what we are planing to do in regards to the expansion problem. We have cut away about 10 inches off the end of the 14" octagonal White Oak blank that we are going to use, and moisture tested it. I mentioned before that it has been cut about 2 years ago and has been drying in a fairly humid damp area (saw mill). It tested 46% moisture at the heart and it progessively became less in moisture content until about 1" from the surface it tested 26%. As you move in about 3 " from the surface the moisture jumps up to about 35% and rises fast as you go towards the heart of the timber. This just food for thought and maybe it will help someone
NH

NH, Your testimony and moisture measurements point out the obvious. Drying from surface to core is a slow NON linear process. Easy to understand when you consider the cell structure channels are at right angles to the cross cut section. Your previous experience with banding suggests any new work should use very tight bands. I vaguely remember my grandfather banding barrels and wheels with very hot iron and then plunging the assembled work in cold water to tighten and accelerate the metal shrinkage. You have to accept a bit of browning of the wood where it first contacts the hot iron. Talk to your friendly local blacksmith.
have fun, work safe

deralte

I have not re-checked the reference, in a FPL booklet on air drying a drying rate estimator factor was given for thicker timber by using a known base rate at a given thickness. Time to dry = (base rate at a given thickness) x ((the factor of thickness increase) ^ 1.5)

thanks again all you experts for commenting and being interested in this project. We are going to turn the 10" section cut from the blank, take careful measurements as noted below, immerse it for 3 or 4 days, and then remeasure it both in circumference and across the heart at 90degree angles. If anyone can think of any other methods please come on board I welcome your comments. There maybe someone out there who has had a similar project either ongoing or about to be done. This is an 1846 Barrel Water Wheel , sometimes referred to as a Rose Wheel, the shaft that we are reconstructing ran in a horizontal position through a 36" Wide pressure box and the cast collars that I keep referring to spun with the shaft up tight against each side of the box, reacting to the escaping pressurized water from inside of the box. the shaft attains speeds of 110 rpms, and has enough power to easily saw lumber using a muley blade 6.5 feet in length, transmitting the power using a pitman, and an offset 9" cast crank on the end of the shaft. This creates an 18" stroke for the blade. Once again thanks for your help so far,
NH

NH,

Although members of this site are very knowledgeable in joinery and wood it seems the data you desire might easily be gathered by posing the question to a wooden boat building site.
It is the goal of timberwrights to make homes that stay dry and avoid them submerging at all cost, therefore, the data is limited. LOL

White oak was often used in traditional boat building. Here is a link to a local man's website who recently built a traditional batteau of white oak. I am sure that he can provide you some very good info on shrink/swell for submerged timbers as that is how many of the boats are made watertight before the races.

http://www.batteaufestival.com/river/rucker2.asp

One of white oaks natural charachteristics is that it is somewhat "waterproof" because of tyloses in it's cell structure. A common use was for boats and staved whiskey barrels. It was the material first used for "hot tubs" at mineral springs. Both of these items being held together with steel or iron bands.

Have you considered useing a timber that is not dried or seasoned but rather green and wet? As long as it is kept wet it should remain fairly stable in dimension. I see little advantage to continue drying it only to get it wet again. Another idea would be to soak it in pitch, pine resin or linseed oil for a period of time after turning and therefore render it almost impervious to water penetration.

Hope this is useful to you and good luck with your restoration project. Old mills are certainly worthy of restoration as they were literally the hubs of our countrys development in their days.

Thanks Crabtree Creek

The site you recommend is very interesting especially because I also helped build a Bateaux here quite a few years ago, and experienced some of the same problems they did in their three tries. Your suggestion to use green White Oak for the shaft, was exactly what I did when I did the first restoration about 25 years ago. I found that I din't get quite enough swelling to keep the cast collars tight, and maybe caused the eventual wear on the shaft. This time I am wrestling with the idea of using wood of the right dryness to give me the proper expansion without too much to crack the original cast collars. thanks again and if anyone thinks of a foll proof method to do this please come on board I welcome the info. Thanks again Crabtree
The Northern Hewer