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From: Bob La Londe <none@none.com99>
Newsgroups: rec.crafts.metalworking
Subject: Re: Shop Crane Revisited
Date: Sun, 22 Dec 2024 10:02:48 -0700
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On 12/22/2024 7:26 AM, Jim Wilkins wrote:
> "Bob La Londe"  wrote in message news:vk7mtd$9buc$1@dont-email.me...
> 
> ...
> Anyway, out by the back fence I found several fairly large I-beams
> setting up off the ground on wood beams.  I think I just found my gantry
> crane.  Now if only I can stumble across some big steel casters out
> there somewhere I'll be set.  Maybe they are under the old gas pumps
> over by the south fence.  ;^)
> Bob La Londe
> ------------------------------------------
> If you don't need to roll a loaded gantry you can use trailer tongue 
> jacks for retractable casters. Position them so you can crank both at 
> one end up and down simultaneously. You can still travel with a load 
> above their rating in steps, moving the load and gantry alternately.

Actually their individual load times four.  Just like any other caster. 
Trailer jacks is not a bad idea, and I have seen this sort of thing done 
on other equipment.  They are also available (at a substantial cost) at 
much higher ratings.  Having seen a few failures generally the 
limitation of most lighter ones is the plastic wheel.  I've seen them 
break.


> Adding outrigger wheels to the casters lets them roll better on dirt but 
> then they don't swivel well. They can be linked and controlled with 
> steering knuckles made from strap steel, drilled to go on the axle, with 
> a pull handle.
> 
> Custom axles are a use for a lathe.
> 
> I've seen boat trailer winches on commercial gantries to raise and lower 
> the unloaded beam. I use them on my tripod supports, attached to a leg 
> with muffler clamps. I would want a lowest beam height that allows 
> hooking on the chainfall without a ladder, they are heavy and awkward. I 
> modified my trolleys with connecting rod sleeves that the chainfall hook 
> fits over (endwise), increasing the working height and allowing the nuts 
> to be tightened without restricting the hook. I put the chainfall on a 
> table and lower the beam to match so I have both hands free to assemble 
> the trolley to them.
> 
> Unbreakable rubber farm buckets are good for storing and carrying a 
> chainfall, and in use they can keep the hand chain out of the dirt/mud.
> 
> The sleeves were a lathe job, water pipe bored to fit over the trolley 
> rod. Much of what I make could be done on a small inexpensive hobby 
> lathe, the shafts and bushings, but not the gears and pulleys. My small 
> lathe turns much faster than my larger one, which is handy to drill deep 
> grease holes in axles. I use the little one for grinding, sanding and 
> polishing to keep grit off the ways of the good one.
> 
> The tripods stand upright without the beam, which makes one-man assembly 
> easy. Published specs suggest that some sizes of water pipe, EMT and 
> chain link fence post may telescope together, I haven't tried with the 
> 2" sizes appropriate for a tripod gantry support. You can check their 
> column strengths with on-line calculators, I know what loading my 
> rigging gear has proof tested to but can't guarantee it for someone 
> else's likely different construction. Single post uprights with free 
> rolling bases would need to be much stronger. The conventional rolling 
> design makes sense on level pavement, mine is for uneven ground outdoors 
> and disassembles for storage.
> https://www.amazon.com/Klau-Industrial-Hanging-Display-Factory/dp/ 
> B0CFFCSFJW/ref=asc_df_B0CFFCSFJW?
> 
> On-line calculators can give you the load capacity of a simply supported 
> standard structural beam with a single centered load, the worst case. 
> The first number is the nominal height of the beam, the second the 
> weight per foot, determinable from the dimensions. I used 1/240 
> deflection as the limit, the beam can handle more but the load may roll 
> toward the center.
> 
> I didn't specifically include loading the truck in my gantry design 
> because the towable shop crane that moves in all directions is more 
> convenient for slung loads, the platform lift for others. Plus I can 
> mount the bed crane to lift on or off anywhere.
> 
> For the heaviest log loads (>3000#) I moved and secured the trolley with 
> two blocks-and-tackle, operated from outside the danger area. They gave 
> fine control to center a maximum sized log within 1/2" on the sawmill 
> and should help to position a heavy lathe chuck or workpiece.
> 
> jsw


-- 
Bob La Londe
CNC Molds N Stuff

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