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07-13-2010, 09:33 PM #1
Homebuilt bridge crane suggestions
I would like to build a bridge crane and would like your suggestions or thoughts.
For the runways I am thinking about using two W10x22 beams to span 24'
Columns 5" Box tubing - 10' tall - Beam bolted to top and gusseted about 2' x 2' back to columns.
The span between the beams will be about 15'
As for connecting the two beams together, I plan on using 8" channel near the ends of the beams and x-bracing the columns with 2"x2"x1/4" angle.
My thoughts are to build a bridge that rides between the W10x22's.
What are the effects of the bridge cars riding inside the beam on the flange itself?
What kind of weight can I safely lift with my chosen beams this way?
(Goal is 1 1/2 ton - heaviest lifts will be about 8' from the columns)
How much strength is lost and is there anything that can be done to minimize any twisting effects on the top beam flange?
(ie. cap with channel or tie them together on top?)
Would I be better off lowering the whole system and making a bridge that runs on top of the beams?
07-13-2010, 10:51 PM #2
Wide flange sections are not intended to have point loading on the flange, such as you envision, and there is no table-driven o easy calculation means to estimate safe loads. It is unlikely anyone on an internet forum who is qualified to do so will give you specific advice on what is a safe load.
However, your 10x22 is plenty strong top loaded. You can get a good benchmark by looking at crane manufacturer's catalogs on the web. Many list the beam sizes for given ratings for their standard line of shop gantry cranes.
07-14-2010, 12:30 AM #3
Can trolleys be hung under H-beams or do I need to refigure using a standard I-beam? The 24' span scares me with just I-beams twisting to collapse?
07-14-2010, 01:38 AM #4
W shape is not as strong on an underhand pull as S
i would say your 10x22 is not up to a 20 ft span as rails, maybe half that but thats just a WAG that would have to be confirmed from some other sorce
another consideration on a span that big is racking
and the simple fact that a 24 bridgebeam is to heavy to pull by hand
take my word for it
harrington sells a motorized truck kit
that is set up to run on #30 rail
thats where you need to start looking
if you buy from them they will supply a bridge beam drawing to build from also
this chart has some beam sizing info
the answer is a real engineer in a situation like this, not WAGS from trolls
07-14-2010, 03:40 AM #5
"the answer is a real engineer in a situation like this,"
I thought that was *always* the correct answer!
Seriously, +1 on that advice - not that any of the replies so far have been
trolls - but if you cannot make the calculations yourself do it right and either
find somebody who has done this for a living or purchase the system you
need. The downside on a failure here is simply too great.
07-14-2010, 04:13 AM #6
The system I'm "copying" has been engineered and certified. (I assume?)
It's used at work nearly everyday. (Generous/Gov't/Greedy Motors?)
The system has little 6" rubber wheels driven by electric motors on the bridge car.
It spans 30' with W10x(either 33 or 39?) up on 17' columns.
The bridge is aluminum, spans 18', electric driven upto a steppy walking pace.
It's only rated at 1 ton. (thought the bridge to be weak link?)
I could probably get a hold of the old build prints. (columns and beams were built in-house 10 yrs ago - bridge came ready to install)
07-14-2010, 04:26 AM #7
Sounds like you know what you want in system needs here, but I would say double check your height, 10' would be low for my needs (I'm working on something similar).
Higher is more challenging though, and would require more and heavier steel.
07-14-2010, 04:38 AM #8
Wish I could go Higher too...
07-14-2010, 05:34 AM #9
All your questions are hard to answer without knowing the tonnage for the main hoist and auxilliary hoist (if you need one).
I concur WF Beams aren't suited for poin loaded rolling weight bearing on flanges. Standard I beams are better. If you're making the crane of available materials then you use what you have.
A top runner crain trolley has double fanged wheels that typically run on rails welded to the center of the top flange. By welded, I mean skip welded to a schedule and by rail I mean the stuff like ralroad track but without the web and the lower flange - although square hotroll will do for light duty. There are de-facto standards and schedules for building crane from structural shapes. Taking a wild gues at what you have spec'ed so far you're working on a top runner tracks suited for about 5 tons assuming the usual conservative design.
Cranes pose some real safety problems because suspended loads and weighty crane structure collapsing on lives and property is too big a disaster to ignore. Once the capacity of the crane, its working envelope, and the size of the critical members are roughed out, it's time for an ME to cast a critical eye over your efforts. You can learn a lot by looking at installed cranes and the catalogs of crane manufacturers. If you don't know an ME a 2 hour consultation might be money well spent. Talk to C&H and other crane makers. They have big design staffs sitting around willing coffee anyway. Put them to work. Engineers are gullible, let them think you're going to buy a bunch of stuff.
Crane design isn't rocket science but a well balanced design will both be safe and save you money in materials. Think first, pump the brains of wiser heads and think some more. Do the engineering work before you commit to materials.
Last edited by Forrest Addy; 07-14-2010 at 02:52 PM.
07-14-2010, 06:11 AM #10
This is not to say that W flange isn't also perfectly OK for a crane, and indeed most crane manufacturers offer W flange trolleys, but they are much, much less commonly used for ordinary cranes. The point is just that the acceptable trolley loading on a W flange (and especially assymetrical as you describe) is not something you'd be able to easily infer from off-the-shelf references, simply because it's not common and you won't find many references.
On the other hand, there are lots of manufacturers of gantry cranes with very explicit documentation available, specifying beam sizes, spans, etc. You would be in safe territory copying these, without custom engineering.
If you look at the doc wippin boy linked to, you'll see right there that they list a S10x25 as required for a 30' span with 1,000 capacity. This is roughly about the same as yours as work.
Note that it's not just the overall strength of the beam and size of load in play here. Exactly how the beam is loaded is important, especially if you are loading on the flange. For example, the number of trolley wheels, the distance between them, where exactly the wheel rides relative to the web, etc. affect the stress on the flange. Again, look online at the sections. Notice that the flange on a W10x33 is 8" wide, but the flange on a S10x35 is only 5" wide. Imagine you are putting the 1,000 load on a wheel running at the outer edge of the flange. There's a big difference between that W flange's 4" lever and the S section 2.5" lever. Also, note again the fact that the S section flange is tapered.
As you should be able to imagine, the main failure risk here is not the beam overall capacity, it's point overloading on the flange (which in turn could lead to overall beam failure).
Btw, if not yet obvious, you'll get higher capacity per pound of steel in a S section for a crane than a W section, precisely because the design of the S section puts the metal where you need it for crane type loading (largely unidirectional.) W sections distribute the metal for loads that are more n-dimensional. They are designed to support building structures, which experience loads in all directions (from wind, earthquakes, etc.) In short, a W section will be more expensive than a S section, and wasting money on steel that is not doing anything for you (carrying no load). The only reason to use a W section is if you have easier access (scrap), or some specialized requirement, like wanting to carry a trolley on one side of the flange. But to do that reasonably safely, you either need real engineering or a really good seat-of-pants safety factor.
07-14-2010, 08:06 AM #11
07-14-2010, 08:59 AM #12
before we go any further
i am the troll i was referring to, so no hurt feelings up to this point please
and according to that coiffing pdf
1 ton 30 ft span is S12 x #35
if your talking your rails you have to add in the ton plus the bridge beam weight which is another 1000lbs
10 x 22 does not make it according to this published document not on a 20 ft poll to poll
07-14-2010, 10:43 AM #13
That said, I myself would be comfortable in my own shop with a 10x35 (not an endorsement for anyone else!!!) for a one ton load in his configuration, because:
- his bridge span is 15'. For a ton, that's a 8x23, so bridge weighs 345#. So bridge plus ton load is about 2,500# (including hoist and trucks) .
- the rails don't see full load. At midpoint, they see half the load, etc. I would consider how large a load I might apply at the ends.
- I would not put columns at rail ends. I would put them at about 3' from the ends because a cantilever is stronger and more efficient. (I would do stress calcs to find exact desired cantilever.) So the rail span is probably about 18'. Per coffing, 10x35 is adequate for a ton at 22.5ft, and I'm confident it's adequate for 2,500# at 18' (but again, it'll never actually see 2,500#)
Again, I am not saying use this or that beam in this specific case. I'm just saying this is an example of how to start thinking about it (although I admit in this scenario I am getting a little beyond the "copy coffing" model by introducing cantilever, etc, which the OP shouldn't do)
07-14-2010, 11:17 AM #14
Question Woodie, is there a good reason to suspend the trucks from the bottom flanges of the beams?
A look at the link Davo J provided, OldCarGuy’s New Toy Shop - Page 3 - The Garage Journal Board
....shows a top supported bridge that maximizes head room, just clearing the lighting and only lowering the side beams against the walls where it shouldn't matter. This removes the W configuration objections of bottom flange loadings, rightly voiced by some.
Again referring to that link, an auxilliary rail welded on top of the beam would be unecessary, with certain considerations and lastly, the vertical posts could be arranged in any configuration and quantity that best supports the load, whereas utilizing the lower flange demands posts only at the extreme ends and at that, will limit the bridge travel to less than a top-of-beam configuration.
07-14-2010, 02:21 PM #15
OldCarGuy's bridge crane looks awesome...
I've also pondered the idea of turning the whole system sideways for better door height clearance.
It would have to be 24' of runway (plenty of room for multiple columns this way too)
I'd need 2 bridges to span 24' and carry 3000lb (split between the two, but if one has problems? so, 3000lb each.)
I'd want as much height as possible so top running hoist cars on double beams?
I'd also feel better top loading the beams.
Thoughts on going this direction?
07-14-2010, 03:47 PM #16
To me those bridge trucks on oldcarguys crane should have some more overkill built in- they dont look stout enough.
07-14-2010, 04:17 PM #17
Davo, I could have said it better !
Woodie, if time is on your side I'd watch the auction market for your crane system. Here in the Carolina's I have seen bridge cranes just about given away at some auctions... Having a rigger not take advantage of you is another story too.
Picking up the components may well save you a nice sum of $$$.
Good luck with your project.
07-14-2010, 08:24 PM #18
Considering the OldCarGuy's setup...
For the runway rails W6x15 supported in the center and 10' out with an additional 2' cantilevered (24' total)
(maybe use W5x19 for an extra inch? 190lbs more $)
Bridge rails (two of them) - I'm thinking I'll need S10x25.4 beams
Since they're so long, cap them with channel to limit roll (channel size?)
Bridge cars - 36" to 42" long made of channel and 3/8" plate
What are your thoughts on going this route?
What size channel should I use to cap the bridge rails?
Are my beam selections good enough?
07-15-2010, 01:56 AM #19
first i was thinking that we were talking a 27 foot span on woodies project so some of my past statements are off a bit.
that being said
To me those bridge trucks on oldcarguys crane should have some more overkill built in- they dont look stout enough.
2 ton 25 foot span calls for S15 x 42.9
there is also no gusseting on trucks to prohibit racking.
abd the second you add in the second bridge beam your rails have to be twice as big or you have to put rolling restriction on bridges so they can be in the same rail span lifting at the same time
i am surely not the definitive answer here and i also do a lot of skimming in theses threads so my statements could be off as to real need for your project
but as Forrest states
do the math or
build it twice as big as you think you should
and then have someone else do the math.
your SWAGIN' this project with no real engineering support
and it could go very badly very quikly
07-15-2010, 07:59 AM #20
Post #230 of the link below includes pic's of a substantial shaper hanging on the bridge crane. The second photo of the shaper, shows it in place, in front of the 6,000# Deckle pantograph, also "flown" into place with this crane. That's a successful 150% test of a "4,000#" crane. Keep in mind that "4,000" is just contrasting black paint on a yellow background, could have been stenciled on the floor.
OldCarGuy’s New Toy Shop - Page 12 - The Garage Journal Board
Keep it low, so what (safety wise) if it wrinkles a little 'til the overload settles to the floor, there's little danger, it's a steel structure, not glass. Don't stand in range of any elevated part of even a certified crane. I don't see it in the same class as torching a fuel tank or wearing a loose necktie while spinning a 24" lathe @ 1,000RPM.
Every new lift is a test and it can be judged carefully at midspan, checking for non-destructive flexure, like a string with weight an inch off the floor, then kept nearer one side for confident lifts. Ain't like falling in a pit o' vipers...... Heck, it's a lot safer than I am riding my motorcycle on the freeway, that IS disregard for safety.
The cost of a strain-gauge/scale could easily be justified, "doesn't exceed my previous test". Most of us have heavy equipment that didn't come with certified weight, the scale eliminates guessing, always a good thing.
In a commercial shop with "just anyone" having access to the crane area? Then follow all the overkill rules, which include heavy safety-factor engineering/certification, 3 to 1 and even more. There, it's little to do with safety and all about litigation, when in court, gotta' look like you care..... a bunch. Eyeball "engineering" for safety can be wildly skewed if your education came only from observing equipment designed by lawyers.