monstermetal Posted January 30, 2010 Share Posted January 30, 2010 I am working on a set of gates, this is the last of three pair for a private school, this one is the widest at just over 30'... and I got to thinking about he next gate I have to build, which is just over 40' (double swing so each leaf is 20') This one seems pretty big, I think its the biggest double gate Ive built.. and the next one is a 1/3 bigger! Just got me worried about sagging, strength, adjustments ... Anyone had any experience with big swinging gates? Quote Link to comment Share on other sites More sharing options...
pkrankow Posted January 30, 2010 Share Posted January 30, 2010 Do you have a software package with some finite element modeling in it? That way you can apply gravity to the design and see the deflection and stresses. Might even be worth outsourcing this after you have a design if you lack the software or expertise in house. Phil Quote Link to comment Share on other sites More sharing options...
monstermetal Posted January 30, 2010 Author Share Posted January 30, 2010 Do you have a software package with some finite element modeling in it? That way you can apply gravity to the design and see the deflection and stresses. Might even be worth outsourcing this after you have a design if you lack the software or expertise in house. Phil Um... No, Im a blacksmith? Yeah saying "I lack the software and expertise" would be the nice way of putting it Quote Link to comment Share on other sites More sharing options...
pkrankow Posted January 30, 2010 Share Posted January 30, 2010 Yes, but you are also a successful and resourceful businessman. Phil Quote Link to comment Share on other sites More sharing options...
BIGGUNDOCTOR Posted January 30, 2010 Share Posted January 30, 2010 Since it is for a school I take it that they will all look similar, or can you do some different designs? Can you put an outboard wheel to help support the end? Can you adjust the design for the longer gate using more triangulation? How much weight are you talking about? Quote Link to comment Share on other sites More sharing options...
arftist Posted January 30, 2010 Share Posted January 30, 2010 We build some heavy (though not nearly that long) gates. Even with computer modeling, there is plenty of sag. We compensate for this by building the gate significantly out of square, allowing it to sag to square. This is not the proper method however, and is a LOT of extra work. We do this because the gates are designed by architechs who think they can order the laws of physics to change at their will. The traditional method is to incorperate a diagonal tension member, originating at the upper hinge and terminating at the diagonaly oposite corner. In traditional work, this tension member could take the shape of a very large scroll, and can be supplemented by additional scroll work. Even small gates which do not need the diagonal tension member were often treated to such, as the purpose is also to provide a focal point and breakup the large expanse of vertical bars. In fact, in shorter gates, the diagonal members often take the form of an X, crossing in the center of the gate, for the most part straight, with just small ornamental scrolls at the ends, in which case, while providing some stability, the primary purpose is visual. I highly recommend you take the traditional path for a host of reasons. Quote Link to comment Share on other sites More sharing options...
monstermetal Posted January 30, 2010 Author Share Posted January 30, 2010 Yes, but you are also a successful and resourceful businessman. Phil So that's an excellent suggestion and something completely different that what I expected to hear.. I have zero experience with such things although I am sure there are locals who are capable.. Would an architect be a good place to start? I realize its more of a engineering problem but I have a architect who I like and listens to what I say (I find most architects nod there head and then do what ever they want) Quote Link to comment Share on other sites More sharing options...
monstermetal Posted January 30, 2010 Author Share Posted January 30, 2010 Since it is for a school I take it that they will all look similar, or can you do some different designs? Can you put an outboard wheel to help support the end? Can you adjust the design for the longer gate using more triangulation? How much weight are you talking about? Two of these gates are already in place and I am confident that this one is going to work out fine, I made hinges that attach with bolts behind brick columns and there are provisions to shim them as necessary to square and adjust. The next gate is the big one... its a completely different design.. Much more ornamental with some forged organic stuff and some big wildlife cut outs... I can incorporate fixed diagonal bracing as well as a cable/turnbuckle to load the post. The client does not want a outboard wheel... Originaly I was going to build him a single cantilever gate... it would have had to be 60 feet long with the captured part.. There are all kinds of problems with the site.. The grade varies a foot from one post to the other... At least the posts are stout... they are 2' square solid concrete covered in stone that go 4 feet into the ground with a full rebar cage and mounting pads ( the guy is a big wig with a large scale commercial contractor and just had "the guys" come out with an excavator and a cement crew) Quote Link to comment Share on other sites More sharing options...
Fe-Wood Posted January 30, 2010 Share Posted January 30, 2010 monster m, I'm sure you know this and have already designed it into the structure.... The gate going up to my shop is 15' wide and after ten years of opperation (solar power opener) it is tearing itself apart. The soft start and stop on the opener is not soft enough for that wide a gate. I should also add it looks very similar to the one lying on the floor in your picture Quote Link to comment Share on other sites More sharing options...
bigfootnampa Posted January 30, 2010 Share Posted January 30, 2010 Your architect is not likely to have the needed technical expertise for this but he may well know who does and be able to refer you in the right direction. Architects usually have engineering contacts because they need them too. While I do think that the recommendations of a good engineer may be useful... keep in mind that your project is a bit outside the bounds of traditional design and engineers are very cautious people, generally... therefore you might get a recommendation from him that makes the whole project too expensive to be practical. In the end YOU are an artist who is rapidly developing a specialty in these very large gates and YOUR experience and judgement based on the smaller (but still LARGE)projects you have already done will be the most reliable resource available. As a fellow craftsman/artist I have had to develop a very fine tuned intuition for the needed strengths/design-considerations for many of my own projects. Trust your instincts because YOU are the best source of expertise for this job! Do listen to your engineer though his input could be quite useful. I once had a good friend who tried VERY HARD to stop the construction of the Teton Dam. He was a professional hydrologist and testified for days saying that the dam would NOT HOLD WATER because of the geology of the site. Because he also had a reputation as an extremely concerned environmentalist, people tended to think he was biased (he was) and they did NOT LISTEN to his warnings. As we all know now the result was the worst xxxx DAM DISASTER in North American history!!! Quote Link to comment Share on other sites More sharing options...
Mainely,Bob Posted January 30, 2010 Share Posted January 30, 2010 The thing that came to mind when I saw your pic was the "bump gates" that used to be used out in the oilfield.They had to be big enough to allow a semi loaded with drilling rig parts thru and stand up to the abuse and traffic of oilfield conditions. If anyone here lives or works near an oilfield(been over 20 years since I`ve left)they could probably put you in touch with some old roustabout who is familiar with the nuances of their construction.All the ones I built were smaller and connected to a steel cattleguard below as a base and support for the post and cable support. If this gate is attached to a solid wall or a fence that could hide the tracks and mechanism a retractable rather than a swinging type gate may be something to consider also.You probably already thought about that though. Quote Link to comment Share on other sites More sharing options...
pkrankow Posted January 30, 2010 Share Posted January 30, 2010 We build some heavy (though not nearly that long) gates. Even with computer modeling, there is plenty of sag. We compensate for this by building the gate significantly out of square, allowing it to sag to square. This is not the proper method however, and is a LOT of extra work. We do this because the gates are designed by architechs who think they can order the laws of physics to change at their will. An engineer would say that is _a_ correct answer, letting the gate sag to the correct shape. Architects could not design what they want to see without allowing for sag. You would need an engineer (or draftsman) to do the modeling. You can also calculate this by hand, as deflection with a distributed load but that will be unpleasant at best. The traditional method is to incorperate a diagonal tension member, originating at the upper hinge and terminating at the diagonaly oposite corner. In traditional work, this tension member could take the shape of a very large scroll, and can be supplemented by additional scroll work. Even small gates which do not need the diagonal tension member were often treated to such, as the purpose is also to provide a focal point and breakup the large expanse of vertical bars. In fact, in shorter gates, the diagonal members often take the form of an X, crossing in the center of the gate, for the most part straight, with just small ornamental scrolls at the ends, in which case, while providing some stability, the primary purpose is visual. I highly recommend you take the traditional path for a host of reasons. If you are developing the design, this may be the better route to go, but if the design is mostly dictated to you then you may be stuck. Lastly, what type of school is this? If this is a technical school or university then you may be able to get student involvement in the design process to help model your designs. I studied this, but I have not done this. I did not mean to come across as patronizing. I did some classroom exercises that resemble this in school, but that was over 10 years ago now. Phil Quote Link to comment Share on other sites More sharing options...
HWHII Posted January 30, 2010 Share Posted January 30, 2010 I do not know if this will help you at this stage of fabrication but I have been envolved with gates this big with a company I use to work for.. They where design on a cad program. The design was simular they used a 4x4 1/2 ' wall hing post and the vertical hinge tube on the gate was also heavy wall 2x2x3/8. The bottom horizontal piece was of a heavy rectangular tube about the size of the one you are using for a straight edge about 11 gage. The L shape these two pieces create together is what gives the structure it strenght to prevent saging. They used this design in alot of large gates. I have also seen where designers have used 10"x 10 gage channel like on stairway stringers usually broke up on a press brake on the bottom of gates to give the same strenght. Quote Link to comment Share on other sites More sharing options...
monstermetal Posted January 30, 2010 Author Share Posted January 30, 2010 Your architect is not likely to have the needed technical expertise for this but he may well know who does and be able to refer you in the right direction. Architects usually have engineering contacts because they need them too. While I do think that the recommendations of a good engineer may be useful... keep in mind that your project is a bit outside the bounds of traditional design and engineers are very cautious people, generally... therefore you might get a recommendation from him that makes the whole project too expensive to be practical. In the end YOU are an artist who is rapidly developing a specialty in these very large gates and YOUR experience and judgement based on the smaller (but still LARGE)projects you have already done will be the most reliable resource available. As a fellow craftsman/artist I have had to develop a very fine tuned intuition for the needed strengths/design-considerations for many of my own projects. Trust your instincts because YOU are the best source of expertise for this job! Do listen to your engineer though his input could be quite useful. I once had a good friend who tried VERY HARD to stop the construction of the Teton Dam. He was a professional hydrologist and testified for days saying that the dam would NOT HOLD WATER because of the geology of the site. Because he also had a reputation as an extremely concerned environmentalist, people tended to think he was biased (he was) and they did NOT LISTEN to his warnings. As we all know now the result was the worst xxxx DAM DISASTER in North American history!!! Yeah? I am from Southern Idaho, That had family living in and around the Teton valley... I do know quite well Quote Link to comment Share on other sites More sharing options...
monstermetal Posted January 30, 2010 Author Share Posted January 30, 2010 Thanks guys... There is a lot of helpful information.. and I should add that I think I have a pretty good idea of what is necessarily, I just tend to way over build things If I have any concerns.. Quote Link to comment Share on other sites More sharing options...
Fe-Wood Posted January 30, 2010 Share Posted January 30, 2010 Thanks guys... There is a lot of helpful information.. and I should add that I think I have a pretty good idea of what is necessarily, I just tend to way over build things If I have any concerns.. In my book, that is always the best answer :D Quote Link to comment Share on other sites More sharing options...
John B Posted January 30, 2010 Share Posted January 30, 2010 I am working on a set of gates, this is the last of three pair for a private school, this one is the widest at just over 30'... and I got to thinking about he next gate I have to build, which is just over 40' (double swing so each leaf is 20') This one seems pretty big, I think its the biggest double gate Ive built.. and the next one is a 1/3 bigger! Just got me worried about sagging, strength, adjustments ... Anyone had any experience with big swinging gates? Having read through most of the posted replies, and being a bit of a traditional old fossil with regard to this blacksmithing lark, a couple of questions and some old tips towards your next set. Sagging seems your primary concern, Traditionally made gates, whatever width (Bear in mind these were a LOT heavier than your construction) had an out of square allowance built in to compensate for this eventuality. That allowance was 1/8" (one eighth of an inch) per foot (12") of gate length, so if you have a 20 foot wide gate, you need a rise from base datum square of 2.5" (two and a half inch)at the 20 foot mark. Triangulation for rigidity is good (Diagonals or suitable linked infil) bounce, whipping and twisting can be more of a problem than sag. Uneven ground, up a slope, or self closing can be accommodated by using rising hinge design. If you are using box section, depending on your climate, condensation can fill this with water, which adds weight, and could freeze and split the tube, a channel section as the bottom rail can be as strong as box, but lighter and not prone to water damage, if you use box, vent to allow drainage of condensation. Adjustment for wear on pintles and eyes could also be considered at this design stage, To go back to traditional blacksmithing gates, they were not hung as such. The backstiles were mounted directly into a socket set into the ground so the weight was taken into the solid foundation, this helped prevent bounce and whippiness. The base of the backstile had a spherical shape forged on, and this mated with a hemispherical socket in the ground this socket was traditionally made in cast iron because of its self lubricating qualities. The top "Hinge" was a journal that was attached to the pillar and allowed the backstile to rotate on its axis directly over the base socket, the journal was built into the pillars, and if the gates were really heavy the fixed part of the journal may be attached to a long strap that was built through the pillar and into the masonry buttressing the pillar. To try to clarify the "top journal", basically it is a U clamp that fits over a round portion on the backstile at its top end, the backstile rotates in this U clamp, and the U clamp fits like an axle bearing around the backstile, with the U part of the clamp being detachable and able to be bolted into position after the gates are placed in situ. The solid bit that fits inside the U clamp is made to mount/fix into the pillar, and the other end made semicircular to fit to the round portion of the backstile, the U clamp formed to the diameter of the portion on the backstile, this fits over this solid piece, and the "eye" is formed for the round portion of the backstile to be fitted into. Holes are drilled to secure the U clamp assembly so it can be fitted to the pillar part of the assembly, and then the gate fitted into this U clamp. I Hope that makes sense, a picture would help but I am afraid I don't have one easy to access at the moment, let alone get it posted. This technique is also useful for fabricated gates with box section backstiles, and relatively easy to do, a blueprint may help if I can get something sorted. Again sorry for another long winded post but I am struggling with trying to explain Quote Link to comment Share on other sites More sharing options...
Mainely,Bob Posted January 31, 2010 Share Posted January 31, 2010 John B, If you were struggling I couldn`t tell it.I thought it was an in depth,well thought out explanation and I had no trouble tracking what you were saying.I came to the end of the post thinking,"I wonder what other great tricks this guy has stored away". I especially like the idea of using the stile as a pivot point to eliminate hanging the gate with conventional hinges.Seems like it would make it easier to hang the gate and especially to build in provisions for adjustment over a wider range for both height and level. I know I came away with information I plan to put to use in the future. Thanks for that. Quote Link to comment Share on other sites More sharing options...
John B Posted January 31, 2010 Share Posted January 31, 2010 John B, If you were struggling I couldn`t tell it.I thought it was an in depth,well thought out explanation and I had no trouble tracking what you were saying.I came to the end of the post thinking,"I wonder what other great tricks this guy has stored away". I especially like the idea of using the stile as a pivot point to eliminate hanging the gate with conventional hinges.Seems like it would make it easier to hang the gate and especially to build in provisions for adjustment over a wider range for both height and level. I know I came away with information I plan to put to use in the future. Thanks for that. Thanks for that MB, The hanging method I describe was the conventional method for all styles of gates, the eye and pintle was mainly for door hanging, nowadays this seems to be regarded as the universallly accepted method One thing I failed to mention in the previous post was the use of the slam plate/bar which served as a way to eliminate the noticable gap between the gates when in the closed position, it also disguised/covered any discrepencies in the space between the gates that were not parallel, and allowed for wear/settling over a long period of time, plus it kept the gates together when using a latch and a drop bar, the drop bar allowing users to just open one gate in one direction only if a smaller opening was required, ie pedestrian or horse mounted traffic as opposed to a coach and horses Quote Link to comment Share on other sites More sharing options...
pkrankow Posted January 31, 2010 Share Posted January 31, 2010 I suspect, but it was not specified, that the gate will be used with an electric opener of some type. Will a "slam bar" aid in the function of the gates even if using an actuator instead of being opened and closed by a person? Phil Quote Link to comment Share on other sites More sharing options...
John B Posted January 31, 2010 Share Posted January 31, 2010 I suspect, but it was not specified, that the gate will be used with an electric opener of some type. Will a "slam bar" aid in the function of the gates even if using an actuator instead of being opened and closed by a person? Phil Like a lot of questions on the site, facts are short, and speculation rife, the more info the better in giving a qualified answer. Short answer Yes I would think so, as it would help prevent inertial runthrough providing the actuators are set correctly so the gate with the slam bar fitted is very slightly in advance of the other when started. There are numerous types of actuator, so check their specifications first. Quote Link to comment Share on other sites More sharing options...
monstermetal Posted February 1, 2010 Author Share Posted February 1, 2010 Yep they have fancy openers, however not installed by me What do you mean by slam bar? Quote Link to comment Share on other sites More sharing options...
John B Posted February 1, 2010 Share Posted February 1, 2010 Yep they have fancy openers, however not installed by me What do you mean by slam bar? Slam Bar (or Closure plate) is merely a strip of metal attached to the front stile of one side of a pair of gates and allows the other to close up behind it, if the drop bolt is in position on the other gate, the access gate cannot 'swing through' onto a pavement or out into the roadway if it is a large gate. It also hides any discrepencies in a central gap, and prevents draughts coming through (joke that last one) I have attached a picture, not very good I am afraid, of a small double gate with just a plain strip of metal used as a slam bar, that may illustrate what a slam bar is. On larger gates the bar may be a profiled section, produced by drawing and swaging/fullering in the section, and can be topped off with a broad ended type of scroll as a feature at the top centre of the gate, this could be a bolt end scroll, or a split end scroll, Fleur de Lys, or other finial feature Quote Link to comment Share on other sites More sharing options...
monstermetal Posted February 1, 2010 Author Share Posted February 1, 2010 Slam Bar (or Closure plate) is merely a strip of metal attached to the front stile of one side of a pair of gates and allows the other to close up behind it, if the drop bolt is in position on the other gate, the access gate cannot 'swing through' onto a pavement or out into the roadway if it is a large gate. It also hides any discrepencies in a central gap, and prevents draughts coming through (joke that last one) I have attached a picture, not very good I am afraid, of a small double gate with just a plain strip of metal used as a slam bar, that may illustrate what a slam bar is. On larger gates the bar may be a profiled section, produced by drawing and swaging/fullering in the section, and can be topped off with a broad ended type of scroll as a feature at the top centre of the gate, this could be a bolt end scroll, or a split end scroll, Fleur de Lys, or other finial feature So no, no slam bar... these are at a school and between the three gates have 30K worth of fancy hydraulic openers and controls... the openers have soft start and soft stop... the only mechanical stop is at the hinge side and is only a safety and to re-square the gates Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted February 1, 2010 Share Posted February 1, 2010 One more general word of wisdom: "Never take a job where they won't let you do well" eg: you are provided with a design you *have* to follow exactly that doesn't take in account things like sag, wear, lever arm deflection of mounting points, etc. As you can make it *exactly* to what they demanded; but when it doesn't work it's *your* reputation that gets bad mouthed. Quote Link to comment Share on other sites More sharing options...
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