calculating post size for gate

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Lately, I have ended up doing more gate work that I have in the past.Other than the gate I built for myself, I just grossly oversize the post and it's setting to make sure it does not move too much over time. This un-necesarily adds to the cost.I'd like to learn how to actually calculate the require post size based on a gates weight and dimensions. Are there some standard calculations you guys use to figure this out?Also any tips or tricks for the actual hanging of a large gate would be great. I am a single man shop, and I have been struggling some getting big gates hung by myself. I have one I am going to build today that is 20 wide by 7 high and is made from 3x3 that I know is going to be a monster to hang alone.Thanks for any advice.RussMiller 302GMIller 12RC SuitecaseMIller 30A spoolgunHF-251D-1WP17 Tig torchSmith HD torchHypertherm 45Jet drill pressHF 7X12 wet cut horizontal band sawPlasmacam CNC table
Reply:Are you talking single panel, hinged on one end? Fork Lift, front end loader, boom truck, etc; are your buddies. I have used forklifts to lift large 200 HP motors and oil coolers from large industrial air compressors.Last edited by nadogail; 07-08-2011 at 12:30 PM.Reason: added textI offer three choices: Good, Fast, & Cheap. You may pick two.Hobart AC/DC StikMate LXHarbor Freight AD HoodHarbor Freight Industrial Chop SawDeVilbis 20 Gallon, 5 HP Compressor
Reply:Depending on weight, one or two engine hoists may be well suited.  I very often wish I had a crane on my truck and have considered a mechanics bed from IMT, or similar, for a welding rig.
Reply:I used to be a carpenter and we had to have roof trusses loaded onto houses fairly regularly. Average cost for the crane was about $250 bucks. The operators were usually very helpful with rigging and always had all the right equipment. It's expensive for ten minutes of work, but priceless in terms of stress.Simple beam deflection calculator: http://www.calculatoredge.com/civil%...eam.htm#hollowLast edited by fortyonethirty; 07-08-2011 at 03:28 PM.Ian TannerKawasaki KX450 and many other fine tools
Reply:Cranes are good. I like them. And tow trucks are the cheap commodity cranes that will show up anywhere. I have had good luck in the past rigging everything and then having the tow truck show up for a quick pick. Usually $50 for 15 minutes. Less if you pay with cash. If you can swing it, and have a truck / trailer to move it, a compact utility tractor is awesome to have. Lifting a couple thousand pounds and digging hole becomes trivial.-Jim
Reply:Buy one of those cheep harbor freight  truck mount cranes and make a mount that goes in you reciever hitch, you can give it extra support with a rachet strap. You might spend $150 total.
Reply:Originally Posted by fortyonethirtySimple beam deflection calculator: http://www.calculatoredge.com/civil%...eam.htm#hollow
Reply:Gate hinge posts should have two additional posts a few feet behind and to the side of it with horizontals welded to them and the hinge post. That way the hinge post is guyed through out the swing cycle. If you do this you could hang a thousand pound gate on 2 3/8" pipe. You can also use an over head or fence to guy the post as well.This gate has an over head to guy it in the closed direction and is attached to the fence that will guy it in the open direction. Attached Images
Reply:If it's a real heavy gate I use my "A" frame to get it into position. I block the gate up on wood blocks and use wedges to get it level or in most cases off level to allow for some sagging. Clamp pieces of angle as down legs, cross ways to keep it from falling over while you weld it. Works great.
Reply:There are no special calculations to work out. Small gates such as single security gates (side alley gates) I use 40x40 box section posts. Any heavy gates ie double security gates I use 100x100 box section posts. If you cut down some solid 20x20 bars at 200mm long and weld them onto the bottom of the post sticking out at different angles, this gives more support, something for the concrete to get hold of. If you do this and use ballust (hardcore, ie broken bricks) mixed in cement, the post will never move!.iron gates
Reply:For the sake of USA clarity, I think Iron Welder's suggestion refers to square tubing posts of about 1 1/2" (40 mm) and 4" dimensions (100 mm).  We do not know the wall thicknesses he is recommending. ScottMiller XMT 350 CC/CV w/gas solenoid opt.Miller S-22A wirefeederBernard 400A "Q" gunMiller Spoolmatic 30A / WC-24C-K 200A torch/gas lensWeldcraft WC-18 watercooled torchHypertherm Powermax 30Victor O/A
Reply:I'm no help on the calculations since, like DSW said, it's not the same as simple beam deflection. I've just gone by past experience. That said, if the people buying a gate are balking over the difference in price between a little and a lot of beef, it's time to use that as an opportunity to educate them on the difference between price and value. In the end building on the cheap is usually more costly in the long run. Here's a pic of my solution to hanging gates. It may not have the capacity of Bob's rig but it's done fine on gates up to 450 lbs. each.Brian LeonardAppalachian Ironworks L.L.C.434 Long Branch Rd, Marshall, NC 28753828 649 9966828 702 [email protected]
Reply:The beam deflection calculator is a handy tool to compare the relative stiffness of different sizes of posts. If you have experience with a particular size post, this tool will help to compare that experience with other sizes.Ian TannerKawasaki KX450 and many other fine tools
Reply:Thanks for the responses.I work out of a step van, so I think I am going to go with the bed mounted crane idea and install it just inside my roll up door.I wish I had more time right now, I'd rather build one then buy one at HF.Seems like a lot of you guys also use past experience to size posts instead of going through calculations. I guess with more experience, I'll get better at it.I am building a gate right now for a customer that put in his own posts. He put 5 inch pipe in the ground. The pipe seems to be about 3/16 and has enough concrete around it. I just know it is going to bend quite a bit because the gate that he wants hung on it is 20 feet wide by 7 feet tall.Thanks again for the responses.RussMiller 302GMIller 12RC SuitecaseMIller 30A spoolgunHF-251D-1WP17 Tig torchSmith HD torchHypertherm 45Jet drill pressHF 7X12 wet cut horizontal band sawPlasmacam CNC table
Reply:Russ,   The engineering question on the post design for lateral loads & moment is not a simple problem.  Check out bse.wisc.edu/bohnhoff/Publications/Copyrighted/EP486_1.pdf     That is not the only source, but you get an indication of the scope involved in answering your question from the soils side of the conversation.  Cantilever bending with a two hinge load is pretty straight forward calculation, loads = your gate + five of the rotten neighborhood kids jumping & swinging on the gate all at the same time.  (Boy, I remember doing that.. it was fun, no?)In this case, how deep is the 5" pipe into the ground?  How long is the pipe?  Frost depth for your location?  materials under pipe? materials around pipe?  Is there a cap at the top of the ground that will resist lateral loads?  What soils are there? (Clay, sand, rock?)  Are there any lateral supports to help support the gate at both closed and full open positions? (Concrete cap, adjacent walls),  etc...  I'm assuming that you have the owners buyoff that he is responsible for the integrity of the gate post (in writing!)  If you want to talk more, PM me.. --zip
Reply:I belong to NOMMA which is the National Ornamental for Misc Metals Association, basically the wrought iron club of america. If you plan to get into ornamental and gate stuff, I highly recommend you sign up. The list-serv alone will pay for itself. A lot of companies do it on experience, but as you probably don't know how heavy your gate will be by over compensating. A 20' gate is very heavy at 20' out, even with 2x4 framing. You will need a post that was installed really well, and I don't think (since I wasn't there) that your post was installed to handle a 20' gate. In the world of gates, the saying goes for installing, concrete is cheap insurance. So put an extra yard of concrete in the ground for safe measures.If you build it correctly, it is still going to weight 400 lbs +. I would use 2x3 or 2x4 x 1/4 post frame (meaning the vertical that the hinges will be welded to), 2x4 x 3/16 as your bottom runner, and 2x2x 1/8" for the rest for the framework. Make everything you can hollow, even really expensive gates have hollow pickets to reduce weight. 400lbs stretched over 20' can weight as much as a 1,000 lbs. can that post handle that? What about snow/wind/rain loads? Gates that are made more solid have a high wind load and can cause a gate to fall over. Also will this gate be automated? Is it someone who just wants a manual gate and won't mind putting a wheel at the far end to hold 50% of the weight?At the end of the day, I would say that 45% of gate makers like myself, have gates installed by another contractor. Its just easier and a lot less on your insurance. Also, is the gate to code? There are a huge amount of codes governing gates, sliders and swing have different codes. Will this gate be some sort of access to a pool? If it is then man are you in for a world of pool codes. Will the township even allow a 7' high gate? some require only 5', 6' whatever. Just be careful with whatever you choose to do.Edit: Neighbors love to complain if gates aren't made to township code. I have had to fix gates that other contractors made too high.Last edited by Country Metals; 07-15-2011 at 07:59 AM.