tag:blogger.com,1999:blog-6433960116916971791.comments2023-07-05T06:31:31.651-04:00Woodworking Stuffstevehttp://www.blogger.com/profile/16865364479881938306noreply@blogger.comBlogger41125tag:blogger.com,1999:blog-6433960116916971791.post-44865282671509989602015-07-23T16:49:39.505-04:002015-07-23T16:49:39.505-04:00You can download my sketchup model for the table h...You can download my sketchup model for the table here:<br /><br />https://3dwarehouse.sketchup.com/model.html?id=5ef5685e19c5b253674ce64e4bf77aec<br /><br />That and the play-by-play here should get you there.<br /><br />Thanks for reminding me I used to be a woodworker!stevehttps://www.blogger.com/profile/16865364479881938306noreply@blogger.comtag:blogger.com,1999:blog-6433960116916971791.post-69093569734705191732015-07-22T16:54:17.871-04:002015-07-22T16:54:17.871-04:00Hey, I was wondering if you have plans those bedsi...Hey, I was wondering if you have plans those bedside tables, please. <br />Cool projects.<br />Thanks.Anonymoushttps://www.blogger.com/profile/11529207154971137976noreply@blogger.comtag:blogger.com,1999:blog-6433960116916971791.post-76602602950952711832014-06-02T04:38:39.984-04:002014-06-02T04:38:39.984-04:00Nice blog with detailed explanation, thanks a lot ...Nice blog with detailed explanation, thanks a lot for sharing!<br />Regards, <a href="http://www.cabsathyderabad.com/" rel="nofollow">cabs in hyderabad</a>Govardhan Avvaruhttps://www.blogger.com/profile/03681151511044647785noreply@blogger.comtag:blogger.com,1999:blog-6433960116916971791.post-19327144550510515232012-01-08T23:05:25.900-05:002012-01-08T23:05:25.900-05:00Oh, also, FWIW:
The T box(s) related to this post...Oh, also, FWIW:<br /><br />The T box(s) related to this post I made for an "elevated platform" bed which I delivered to my sister shortly after this original post (in 2008).<br /><br />The T box sits on two cleats on the inside of the long rails of the bed... that is, the T box SPANS the distance between the rails. So, the important (unbroken) ribs run in the direction across the bed, not from headboard to footboard.<br /><br />As I write this, it's 2012. I'd rather not speculate on how much, uh... let's say "dynamic loading" my sister and her husband put on this bed, but it's still in one piece and keeping them off the ground these few years later.stevehttps://www.blogger.com/profile/16865364479881938306noreply@blogger.comtag:blogger.com,1999:blog-6433960116916971791.post-35337171167181030412012-01-08T22:57:28.570-05:002012-01-08T22:57:28.570-05:00I need to do a better job attending to this post -...I need to do a better job attending to this post - sorry to all.<br /><br />1. I got this math from this book: http://www.amazon.com/More-Woodworkers-Essential-Short-Cuts-Essentials/dp/1892836211.<br /><br />2. I believe the math posted for THE BOX I MADE is wrong. I vaguely recall a miscalculation/ recalculation at some point, and I don't recall updating the blog post to reflect it. Backing stuff out of it probably won't work. AFAIK, the equations are correct, tho.<br /><br />3. The math suggested by Mr. Horner jives with my aging memories of engineering classes:<br /><br />The equation for deflection of a beam is as stated. <br /><br />"I" is the moment of intertia.<br /><br />Since the "beam" is composed (in a section view looking through the side of the box anyway) of a rib with a skin on each side, you must calculate I for both the rib and the skins and add them together to get the TOTAL moment for the assembly which is then chugged into the deflection equation. <br /><br />IIRC, the "thickness" of the "rib" is the total for all ribs. IOW, if you have 5 ribs at 3/4" thick (in the span direction), that's like having a 1.25" thick rib. <br /><br />On calculating I for the skins:<br />The equation is different from the rib moment calculation because 1) the skins are separated from the centerline; 2) the skins have breadth, whereas the ribs only have thickness. I specifically use "breadth" so as not to be confused with "width".<br /><br />If you study the rib moment equation (more confusion because what I call "width" is really "height"), note that the width and thickness are accounted for... NOT LENGTH. So, for the skins, breadth is analogous to "width" of the rib; you're capturing the amount of skin going "into the page" in your section view.<br />Note that each I calculation takes a dimension to the 4th power - and NONE of those dimension are LENGTH (that comes into play in the actual deflection calculation). For the beam (rib) I, it's a height X thickness cubed (4th power); for the skins, it's an area (already a square) times a distance squared (4th power).<br /><br />Now, "D": The "neutral axis" of the box is the centerline, IF the skins on both sides are the same thickness. So, a 4" rib with 1/2" skins on both sides would have "D" = 2" (half the rib) + 1/4" (half the skin). If you draw the section view, visualizing "D" becomes trivial.<br /><br />Also note: there's usually TWO skins, note that in the Itotal that gets plugged into the deflection equation.<br /><br />Lastly, note that a T box is usually a GRIDWORK of ribs. The ribs that SPAN should be continuous (unbroken, not half-lapped into the perpendicular ribs). THOSE are the ribs that carry load, and for which we're calculating all this jazz. Ribs running perpendicular to the span DO NOT contribute to stiffness (preventing deflection), they ONLY contribute to keeping the span ribs from twisting/ folding under load.<br />If you're building a box to be FLAT, this doesn't really matter. If you're building a box to carry a LOAD, I'd pay attention.<br /><br />4. DISCLAIMER: It's entirely possible I don't know WTF I'm talking about. I went to school for engineering a thousand years ago and have never actually done it for a living. PLEASE don't rely on me as an "expert" on this.<br />Like those who seem to have landed on this page, I was a dude frustrated by trying to find math online to calculate T boxes. When I saw a reference to a book that contained the math, I bought it, and posted it on my blog so it would be easy for me to find should I need it again (I still own the book, but if my life depended on it, I doubt I could find it).<br /><br />Hope all this helps someone.stevehttps://www.blogger.com/profile/16865364479881938306noreply@blogger.comtag:blogger.com,1999:blog-6433960116916971791.post-24614056986134229142012-01-08T13:04:53.222-05:002012-01-08T13:04:53.222-05:00Steve, thanks for posting the math for a Torsion b...Steve, thanks for posting the math for a Torsion box. You're the only place I've found it thus far, but I don't understand your algorithm, specifically the skin calculation.<br /><br />I=AxD^2<br />A=Breadth x thickness of skin<br />D=Centerline of skin to neutral axis of box<br /><br />I don't understand what A and D are. I tried to back into it using your example, but no luck.<br /><br />I think most examples of torsion boxes I see are over engineered, but I need the math to prove it.<br /><br />Thanks.Concrete Deck Headachehttps://www.blogger.com/profile/12780160426587416041noreply@blogger.comtag:blogger.com,1999:blog-6433960116916971791.post-88848791938125490922009-04-24T08:25:00.000-04:002009-04-24T08:25:00.000-04:00Nice work.Nice work.Jeff Branchhttps://www.blogger.com/profile/01402561454519694074noreply@blogger.comtag:blogger.com,1999:blog-6433960116916971791.post-38467496767251755382009-04-20T06:34:00.000-04:002009-04-20T06:34:00.000-04:00Get the best online Platform Beds India from theur...Get the best online <A HREF="http://www.theurbandecor.com/modern-bedroom-furniture-india/modern-bedroom-furniture-india.html" REL="nofollow">Platform Beds India</A> from theurbandecor.com.You will find the best of the best.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-6433960116916971791.post-21742558228745790262009-04-11T17:39:00.000-04:002009-04-11T17:39:00.000-04:00Pretty cool. I never have tried floating tenons. ...Pretty cool. I never have tried floating tenons. Next project I do, I may have some questions for you.Jeff Branchhttps://www.blogger.com/profile/01402561454519694074noreply@blogger.comtag:blogger.com,1999:blog-6433960116916971791.post-26516652174302919322009-02-15T23:54:00.000-05:002009-02-15T23:54:00.000-05:00I am math challenged and would like some advice on...I am math challenged and would like some advice on torsion boxes. I am making a table 4'x7' only supported at ends. I would like the table to be 2" thick. When finished I will be putting a thin (3/8" including thin lath) concrete veneer over it.<BR/><BR/>My initial plans are to use strips 1 1/4h x 1"w on a 4"x4" grid. Then enclose it with 3/8" sheets.<BR/><BR/>This is of course guess work, a math solution would be greatly appreciated.<BR/><BR/>Thanks, my brain thanks you in advance.John Basshttps://www.blogger.com/profile/16556993847823831263noreply@blogger.comtag:blogger.com,1999:blog-6433960116916971791.post-87115227837731260952009-02-13T15:46:00.000-05:002009-02-13T15:46:00.000-05:00fishfishAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-6433960116916971791.post-50932983365449184562009-02-10T08:28:00.000-05:002009-02-10T08:28:00.000-05:00As for donating wood, you can drive over and I'll ...As for donating wood, you can drive over and I'll be glad to give you some of my scrap lumber, cut offs and such. I live in Alabama. I know what you mean about the coffers being dry. I am starting on a coffee table project and just purchased some lumber. The wife is going to kill me.Jeff Branchhttps://www.blogger.com/profile/01402561454519694074noreply@blogger.comtag:blogger.com,1999:blog-6433960116916971791.post-44539736072056623302009-02-01T20:11:00.000-05:002009-02-01T20:11:00.000-05:00Thanks, JB.Ric, so are you going to issue the fund...Thanks, JB.<BR/><BR/>Ric, so are you going to issue the funds out of the dues kitty? ;)stevehttps://www.blogger.com/profile/16865364479881938306noreply@blogger.comtag:blogger.com,1999:blog-6433960116916971791.post-67639957197602242112009-01-31T13:18:00.000-05:002009-01-31T13:18:00.000-05:00That's pretty darn nice.I think next Steve should ...That's pretty darn nice.<BR/><BR/>I think next Steve should work on a repro of http://arstechnica.com/gaming/news/2008/08/sultan-table.arsAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-6433960116916971791.post-23976644204773259912009-01-30T20:06:00.000-05:002009-01-30T20:06:00.000-05:00I have been working with wood for about 25 years, ...I have been working with wood for about 25 years, so I look at your hall table and notice the nice sheen of the top and the relection of light on the area adjacent to the open drawer and I don't see any blemishes in the finish. Looks like a fine job to me. What are you building next?Jeff Branchhttps://www.blogger.com/profile/01402561454519694074noreply@blogger.comtag:blogger.com,1999:blog-6433960116916971791.post-73857805432601591742009-01-29T21:57:00.000-05:002009-01-29T21:57:00.000-05:00Looking good - like the color combination.Looking good - like the color combination.Jeff Branchhttps://www.blogger.com/profile/01402561454519694074noreply@blogger.comtag:blogger.com,1999:blog-6433960116916971791.post-51339750540054836052009-01-27T23:56:00.000-05:002009-01-27T23:56:00.000-05:00jb, as you can see - I can relate!Larry, attempt 1...jb, as you can see - I can relate!<BR/><BR/>Larry, attempt 1 was with "Old Fashioned" milk paint. It worked SOOoo well on the sample boards. I topcoated with Waterlox and I think it was nearing the end of it's life.stevehttps://www.blogger.com/profile/16865364479881938306noreply@blogger.comtag:blogger.com,1999:blog-6433960116916971791.post-3622795847220889802009-01-27T21:23:00.000-05:002009-01-27T21:23:00.000-05:00I hate finishing furniture! I design it, build it...I hate finishing furniture! I design it, build it and then mess up the finish. Good luck.Jeff Branchhttps://www.blogger.com/profile/01402561454519694074noreply@blogger.comtag:blogger.com,1999:blog-6433960116916971791.post-8324367514342184002009-01-27T08:33:00.000-05:002009-01-27T08:33:00.000-05:00Sorry to see you having to refinish your table. Y...Sorry to see you having to refinish your table. You might consider giving General Finishes "milk paint" a try. It's not a true milk paint (it's an acrylic) but it looks like milk paint after application. But, it's far easier to get a smooth, even finish.<BR/><BR/>Cheers --- LarryLarry Marshallhttps://www.blogger.com/profile/02211549672565037525noreply@blogger.comtag:blogger.com,1999:blog-6433960116916971791.post-69655358949470655722009-01-23T20:19:00.000-05:002009-01-23T20:19:00.000-05:00Good luck - I hope to have a sprayer some day.Good luck - I hope to have a sprayer some day.Jeff Branchhttps://www.blogger.com/profile/01402561454519694074noreply@blogger.comtag:blogger.com,1999:blog-6433960116916971791.post-35470206634883151682009-01-12T11:39:00.000-05:002009-01-12T11:39:00.000-05:00Hey Jeff, I'm going to try rubbing it out - that w...Hey Jeff, <BR/>I'm going to try rubbing it out - that will either fix what's there or ruin what's there. <BR/><BR/>If it's fixed, I'm done. If it's ruined, I'm starting over and spraying. Me + brushing finish is always a crap shoot.<BR/><BR/>I used to just accept the disappointment of a less-than-good finish, but so much of the overall appearance and "quality" of a project comes down to the finish. It's worth getting it right, even if that means starting over.stevehttps://www.blogger.com/profile/16865364479881938306noreply@blogger.comtag:blogger.com,1999:blog-6433960116916971791.post-48786246094685156452009-01-11T22:13:00.000-05:002009-01-11T22:13:00.000-05:00Looking good. Like the dovetails. I would be int...Looking good. Like the dovetails. I would be interested to know how you work out the finish problems. I just completed a bookcase for my daughter and as usual, I was not pleased with how it was finished, not my strong point.Jeff Branchhttps://www.blogger.com/profile/01402561454519694074noreply@blogger.comtag:blogger.com,1999:blog-6433960116916971791.post-76249671260260175632009-01-08T08:40:00.000-05:002009-01-08T08:40:00.000-05:00looking good. Can't wait to see it with the black...looking good. Can't wait to see it with the black.Jeff Branchhttps://www.blogger.com/profile/01402561454519694074noreply@blogger.comtag:blogger.com,1999:blog-6433960116916971791.post-62561538546114909822009-01-05T23:36:00.000-05:002009-01-05T23:36:00.000-05:00The top is cherry - the finish going on is clear s...The top is cherry - the finish going on is clear so the color you see is the natural color of the wood.<BR/><BR/>The rest of it (legs and aprons) is soft maple which will ultimately be getting painted black.stevehttps://www.blogger.com/profile/16865364479881938306noreply@blogger.comtag:blogger.com,1999:blog-6433960116916971791.post-41959021493268953422009-01-05T22:10:00.000-05:002009-01-05T22:10:00.000-05:00I am getting into your project a little late - wha...I am getting into your project a little late - what wood is that? I like the color.Jeff Branchhttps://www.blogger.com/profile/01402561454519694074noreply@blogger.com