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Cremation urn questions - joinery, volume calculation, etc.

Lloyd Johnson

Administrator
Staff member
If you have made or plan to make a cremation urn, how will you join the top of the urn to the vessel itself. I have seen some people have used black ABS plastic in a technique that seems reasonable. Here is a link to one such solution: http://www.woodturningonline.com/Turning/Turning_content/Threaded_inserts_for_urns.pdf

Are there other methods you think should be considered?

While we're on the subject, I have seen that the volume calculation should be one cubic inch for each pound of live weight. Do you have any experience to say how accurate this estimate is?

Also, what methods have you used to estimate the size of a turning to achieve a target of 200 cubic inches, for example?

If you have any pictures of cremation urns you have made, it would be great if you would attach them.

Lloyd
 
I have also heard the volume calculed the same way...1 cu in per lb of body weight. The only ashes I am familiar with were those of my mother, who died when she weighed around 130 lbs. The volume of her ashes were pretty close to 130-140 cu in, which I think is pretty close. Bottom line, is I would err on the side of a bit larger than estimated.

As far as volume of the turning is concerned, I once tried without much success to use Sketchup, along with a downloaded ruby script that calculated volume of solids. I imported an image of my 3D vessel shape to Sketchup, rescaled to the right height, then rotated it around a central axis to get a solid. Then applied the Sketchup script. It spit out the volume pretty well, but the whole process was difficult for several reasons. It didn't take into account my vessel wall thickness, nor the inside curvature...it was more of a ballpark estimate. One thing it DID let me do fairly quickly, was to make several height adjustments to the urn, so when I finally did complete the design using WTP, I knew how big to make the overall vessel, for the volume I wanted.

None of my urns have ever been used for ashes...they were more of an experiment in design. My lids were threaded, using wooden threads I made with a jig. Here's one example...5" dia x 8" tall. Because of the lid, wall and bottom thickness, it's about 80 cu in.
 

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Lloyd, you are correct regarding the volume calculation of 1cu in to lb body weight. I made 2 urns and I used the formula of 1/3xpi x r2 x h (volume of a cone) and shaped the urns accordingly. During the design phase i rough estimated the volume to come up with the overall dimensions. I used pvc schedule 40 threaded couplings for the lid in one and in the other I hand shaped a slope/ramp on the urn inside rim and had 2 dowels protruding from the lid side that when engaged and turned the lid would tighten. Of the two ways the threade pvc was a nicer way to do it. I tried to add photo but was unable to upload for some reason.

Regards
 
I can't imagine ever having to or wanting to remove the lid in the future so why not just turn a fairly close tolerence foot to a lid and use silicone sealent to set the lid???
 
For a standard urn, this is true. However a companion urn may be opened more than once if the companions don't die together. The purpleheart urn on my website is a companion urn that is 15" high and 10" diameter at the widest spot. It opens as many times as required.
 
Tried this once. My sister-in-law had a pet, and you know the rest of the story as they say. At the time I could not find out anything about the size, but it was a little dog so I guess "large". I have since heard (from Alex) the 1cm/pound idea. I am attaching a couple of pictures of my first attempt.The lid works like a lidded box and i glued it shut after pplacing the aches inside (in a zip lock bag).
 

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Brad, what I did was purchase a 3" male and female threaded coupling. I put the male piece on the lid and female in the urn, though this could be reversed. Prior to installing I cut doff the male thread, I cut it about 2 threads long, I then epoxied this onto a stub, equal to the inside diameter of the coupling, turned on the lid. For the female portion, I put the coupling on the lathe and turned it down to match the size of the opening in the top of the urn. I then cut the turned down coupling to about 3 or 4 thread length and epoxied this piece into the urn.
Hope this makes sense.

Regards

Mick Steele
 
I know it has been awhile, but I finally found the formula I have been looking for. To determine the volume of a cremation urn, you can use the calculation for the volume of a truncated cone. The formula is:

V = pi x h x (R2 + r2 + R x r) / 3 where h=height of vessel, R = major radius and r = minor radius. Based on this calculation, my individual urn that is 7-1/2" dia by 10-1/2" high is approximately 218ci. This is where I want it to be for most cases.

Now if we can just get Lloyd to incorporate this into WTP
 
Alex,

I think it will be a whole lot easier to post your personal email address and have you calculate the volume for them. :)

Actually, it has been on my list for a long time and I just haven't gotten around to doing it. I'll see what I can do.

Lloyd
 
Well, I gotta tell ya Lloyd, my english is more gooder than my cipherin skills. Why do you think it took me 3 years to discover this formula
 
Well the good news, Alex, is that I will use this formula so your effort in finding it is appreciated. I'll treat each row as a truncated cone with the inside wall profile at the top and bottom of the row defining the diameters. I'll then let you select the rows that are to be included in the calculation and then add the volume of those rows to give you the total volume of the selected rows. This should give you a very accurate volume calculation.

Lloyd
 
Lloyd, you posted a video using Sketchup to calculate the vol. in a vessel but I can't find it. If you haven't taken it down do you have a link?
Stuart
 
I know it has been awhile, but I finally found the formula I have been looking for. To determine the volume of a cremation urn, you can use the calculation for the volume of a truncated cone. The formula is:

V = pi x h x (R2 + r2 + R x r) / 3 where h=height of vessel, R = major radius and r = minor radius. Based on this calculation, my individual urn that is 7-1/2" dia by 10-1/2" high is approximately 218ci. This is where I want it to be for most cases.

Now if we can just get Lloyd to incorporate this into WTP

Is it my understanding that the Cubic volume of the vessel should be equal to 1 cubic inch equal to 1 pound of the deceased? So in your case this would equate to a person weighing 218 lbs??
 
Is it my understanding that the Cubic volume of the vessel should be equal to 1 cubic inch equal to 1 pound of the deceased? So in your case this would equate to a person weighing 218 lbs??

Approximately. The weight/CI ratio is not exact and I try to go a little bigger just to err on the side of caution. The mortician can give you the weight at time of death. I find that for the style of urn I prefer to turn, 10-1/2" tall x 7-1/2" to 8" diameter fits most people and stays within the golden mean. For those that chose to display the urn, aesthetics are important
 
Well the good news, Alex, is that I will use this formula so your effort in finding it is appreciated. I'll treat each row as a truncated cone with the inside wall profile at the top and bottom of the row defining the diameters. I'll then let you select the rows that are to be included in the calculation and then add the volume of those rows to give you the total volume of the selected rows. This should give you a very accurate volume calculation.

Lloyd

Sounds great Lloyd. That will allow the user to include only those rows that will actually be used to hold the cremains. Lid/Base don't need to be included. Can't wait for the next iteration of the software.
 
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