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It's tough accurately estimate the safe loading of something like this, for what an engineer charges, I think it's well worth providing the details of the column, base plate, beam and length of the span etc. Having it checked and verified is well worth the cost. Other than that, you can duplicate something similar that is known to work, but in my opinion this is like building a wood framed home, barn or similar, a lot of people don't know the engineering aspects of the wood framing, but certainly know what works, mostly because of how common this kind of construction is. In my opinion what you propose should be checked out, it's a significant span, if it ever fails, it's going to kill. One of the handiest little reference books out there regarding steel is the A.I.S.C. - American Institute of Steel Construction handbook, it has all the steel shapes illustrated. You can select something from the book that has potential for the span and have it checked by an engineer. With a span that length, you are going to get some deflection in the middle of the beam even with a 1 ton load, what max. allowable is it's hard to say. The other thing is, once it is up, people tend to push things, " Oh it'll hold" etc. but not knowing makes it dangerous even if like you say, you will only use it for light loads, just takes one time. - just opinion here I'm thinking you will want a low profile shape. If I recall correctly, steel is defined first by its shape, using a letter, then by it's web size and then how many pounds per foot it weighs. A W12x75 is a W shape ( why they call it that I don't know ) 12" web beam that weighs 75lbs. per foot. This would be a heavier style shape, stonger than one that weighs 25lbs per foot. I'm just using this as an example. Assuming that you can place columns on each side with a base plate that can be securely anchored into the existing concrete slab, and will carry the load of a beam spanning across + additional live load of your rigging and whatever you intend to hoist, that certainly is half the battle and not complicated by any means. The next thing you would want to consider is the lowest profile ( shortest web ) beam that you can use to make the span and provide the loading you want with some safety margain inlcuded. The top and bottom of the beam being the flanges and the web in between, you may want a wider flange, thicker web, to reduce the impact on your ceiling height, if that is an issue, otherwise I believe the web dimension will increase to meet the loads of supporting itself and what you intend to rig from it. This is only important if the ceiling height is an issue and you have to maintain the span unsupported except on the ends. Another consideration would be stiffeners added to the beam, but they cannot interfere with your trolley, so a wider flange may help. Just some considerations here. I like the idea of having this set up in a shop, it's a valuable feature. I'd also suggest that if for some reason you need to pick something heavy, see what kind of allowable shoring could be placed, to reduce the span and increase the loading. These could be fabricated and used when needed, then removed and stored out of the way. An engineer can provide details on that, and or take your suggestions, but could be a valuable accessory to the set up if you ever need to increase the loading it's always good to look ahead when doing these things, may need it someday. Don't get me wrong, a lecturer I am not, this is not a complicated thing at all, a good hands on engineer should be very helpful, inexpensive and once said and done, you will have a stamped sketch and calculations, know exactly what to purchase, have fabricated, know how to install it, and can label a rating on it in clear view as a reminder to it's safe capacity. You may also want to provide details of existing steel framing, if you have drawings for the building, it may be of help. If you were to provide, strength and thickness of your existing concrete slab, fastening and baseplate details, column, and beam size, with the span length, you should be able to have a competent engineer calculate, it out in a few hours. In construction, I used to live by field sketches, a fax machine and the phone when having to make changes to large exterior component structural connections due to the ever changing field conditions, it was a pain to keep the sketches and calculation booklets updated for record, more so than solving the problems and having things re-calc'ed. The structural steel guys did not usually have to do this, but our work it was common, nothing is ever as it appears on paper LOL ! Well not always but, we used to do a lot of changes. My engineer was in Wisconsin and I was in NYC, his rate was at the time I think $75.00 / hour and very pleasant to deal with.
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