Attention Segmenters will this stay together

[Jim McLain]

I have been thinking about this concept for several years and may finally get to it this year. I want to assemble a segmented wheel probably 12 segments per layer. The inside if the wheel will be 6 inches with an outside diameter of 24 inches. It will have four layers of 3/4 inch boards but the center will be hollow. Where it gets tricky is the two middle layers will consist of two rings each about 1 1/2 inches wide. the inside ring will have an id of 6 inches with an of of 7 1/2 the outside ring will have an id of 22 1/2 with an id of 24. All four rings will be capped with rings 9 inches wide with an id of 6 and an id of 24. Hope this makes sense.

 

[Don Wattenhofer]

If you want it to stay together make the outside layers of three 1/4" layers each with the center layer seams staggered. The inside should be made of six 1/4" layers and finish the inside 22 1/2" diameter before sandwiching it with the two outside layers. The sectional view in the sketch should show 3 layers rather then the 2 shown and if you wanted to make the inside layer three 1/2" layers that would work also

How about if you let us know what it is for.

 

[Jim McLain]

If you want it to stay together make the outside layers of three 1/4" layers each with the center layer seams staggered. The inside should be made of six 1/4" layers and finish the inside 22 1/2" diameter before sandwiching it with the two outside layers. The sectional view in the sketch should show 3 layers rather then the 2 shown and if you wanted to make the inside layer three 1/2" layers that would work also
View attachment 58922
How about if you let us know what it is for.

Thanks Don I appreciate it. I like doing more layers and particularly like the double layer on the top and bottom. I have done some segmenting but this one is a little over my pay grade.

The wheel once turned will receive a basket illusion on one side and the outside edge. The other side and the center will have my Chaco carving on it. Similar concept to cave 7 in my photos but a larger scale.

 

[Don Wattenhofer]

Thanks Don I appreciate it. I like doing more layers and particularly like the double layer on the top and bottom. I have done some segmenting but this one is a little over my pay grade.

The wheel once turned will receive a basket illusion on one side and the outside edge. The other side and the center will have my Chaco carving on it. Similar concept to cave 7 in my photos but a larger scale.

One other thing to say: The three layers are desirable to not only assure that the 12 end grain joints per layer are brick laired, but structurally balanced similar to plywood that always contains an odd number or plies.

 

[Steve Bonny]

Your very wide segments on the cap layers are risky. With moisture change the segments will expand across the grain, but not along it..... which means the segment angle will want to change, forcing gaps between the segments. The effect gets worse the wider the segments get. The bricklayered approach with multiple layers will help but the stresses will still be there. Mixing the grain direction between layers may help - i.e. like plywood. It would help to balance the growth in both directions.
Good luck!

 

[Alan Miotke]

Your very wide segments on the cap layers are risky. With moisture change the segments will expand across the grain, but not along it..... which means the segment angle will want to change, forcing gaps between the segments. The effect gets worse the wider the segments get. The bricklayered approach with multiple layers will help but the stresses will still be there. Mixing the grain direction between layers may help - i.e. like plywood. It would help to balance the growth in both directions.
Good luck!

Steve,
I was just about to post when I saw yours. I agree with 100%.

I was thinking about the test you did last year stabilizing wood movement by making segments with alternating grain at a 45degree angle. This could be a good solution for this configuration. Agree? This was the idea originally proposed by Jerry Bennett.

 

[Steve Bonny]

Steve,
I was just about to post when I saw yours. I agree with 100%.

I was thinking about the test you did last year stabilizing wood movement by making segments with alternating grain at a 45degree angle. This could be a good solution for this configuration. Agree? This was the idea originally proposed by Jerry Bennett.

Al, I think Jerry's base would help for sure, but at this size it would still be at risk of failure at the outside where the wide rings join to adjacent rings. I think the plywood concept where there are several layers with the grain staggered at 90deg each layer would help balance all the movement out.

Jim, Jerry's concept is illustrated below. With this the grain direction is at 45deg to the center line of the segments. The segments are arranged to alternate the grain direction. This balances out the movement so the segment joins are happy. But it still allows distortion at the outer edge which could lead to a joint failure at the size of your project. Hard to say for sure.



Exaggerated distortion at edge with added moisture content.....



I built a few of these rings and did some extreme testing. Mine were about 8" diameter. I baked them dry and then soaked them to a high moisture content and as stand-alone rings they survived but took on the distorted shape shown above. I then added regular segmented rings to build it into a box and repeated. They failed joints in the adjacent rings. Pretty extreme conditions, but the large size of your project will make the situation worse than my 8" rings.

One of the test pieces was built into a bird feeder and is hanging outside. It rained for a few days here in Iowa and the joints on the adjacent ring are starting to fail.



I'm not sure what you plan to use your wheel for. If it is an indoor project in a stable environment, this concept might work. If it is a waterwheel for a mill....... Likely not going to work.

 

[Jim McLain]

Al, I think Jerry's base would help for sure, but at this size it would still be at risk of failure at the outside where the wide rings join to adjacent rings. I think the plywood concept where there are several layers with the grain staggered at 90deg each layer would help balance all the movement out.

Jim, Jerry's concept is illustrated below. With this the grain direction is at 45deg to the center line of the segments. The segments are arranged to alternate the grain direction. This balances out the movement so the segment joins are happy. But it still allows distortion at the outer edge which could lead to a joint failure at the size of your project. Hard to say for sure.

View attachment 58967

Exaggerated distortion at edge with added moisture content.....

View attachment 58968

I built a few of these rings and did some extreme testing. Mine were about 8" diameter. I baked them dry and then soaked them to a high moisture content and as stand-alone rings they survived but took on the distorted shape shown above. I then added regular segmented rings to build it into a box and repeated. They failed joints in the adjacent rings. Pretty extreme conditions, but the large size of your project will make the situation worse than my 8" rings.

One of the test pieces was built into a bird feeder and is hanging outside. It rained for a few days here in Iowa and the joints on the adjacent ring are starting to fail.

View attachment 58969

I'm not sure what you plan to use your wheel for. If it is an indoor project in a stable environment, this concept might work. If it is a waterwheel for a mill....... Likely not going to work.

Steve - Thanks for this illustration very helpful. How much of an impact will wood selection make on this? I am planning on using genuine mahogany. As I said earlier the wheel will be carved with basket illusion on one side and my Chaco carving on the other side. if I do go forward with it, it may have to be a keeper for a year or two before i sell it to insure it is not going to come apart.

 

[Steve Bonny]

Steve - Thanks for this illustration very helpful. How much of an impact will wood selection make on this? I am planning on using genuine mahogany. As I said earlier the wheel will be carved with basket illusion on one side and my Chaco carving on the other side. if I do go forward with it, it may have to be a keeper for a year or two before i sell it to insure it is not going to come apart.

Wood choice will be a factor. Woods do exhibit different rates of expansion/contraction with moisture. Also they have difference glue joint strengths.

There are some comparisons of some common woods here, but no mahogany on the list!

https://www.popularwoodworking.com/wp-content/uploads/Screen-Shot-2012-08-24-at-9.24.29-AM.png

This is from the wood database - indicates you have a good choice.....

• Excellent stability. As much as it’s known for its workability, mahogany is equally known for its superb dimensional stability. Flat pieces will remain flat. Joints and glue-ups will remain intact. In the midst of seasonal changes in humidity, mahogany exhibits minimal shrinkage and swelling.

 

[Steve Bonny]

Jim, I'll add that "failure" can show itself as a crack in the finish (especially with film finishes), a minor gap in a joint or crack in the wood. Worst cases I've heard of are projects breaking into multiple pieces. I've seen pictures of many of these!