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Castors & Rails - Portal/Gantry Crane

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Jelly

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As the final step before I'm really ready to start equipping my workshop in earnest, I'm looking at building a Gantry Crane spanning the full width of the workshop and running the full length.

Design load will be about 800kg-1200kg (until I finalize on a design and do complete calculations, it's hard to be exact what the SWL would be, but aiming for around 1 tonne as that would be useful, without the cross-beam getting so big that it impacts on headroom.



Issue is, I'm looking at having a 3.05m wide gantry in a 3.2m wide gap, even a tiny amount of twisting when pushed/pulled is going to make that unmanageable, the obvious thing to do is to use some kind of rails.

But I haven't the foggiest where I would source appropriate steel sections or matching castors which are load-rated.



Running regular castors in steel channel or against steel angle is an option, but is likely to result in quite a lot of friction/wear and I don't really want to have to keep changing them as once assembled it would be a huge job to change them.

Just to add complexity, the track would initially run 7.5m, but there's an option to take the workshop back to about 12m long, which I will likely end up doing in the fullness of time, so an option which would be easy to extend is a benefit.



Anyone got any suggestions?
 

TFrench

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I'd be thinking about making an overhead beam crane that runs the full length of the workshop. They come up cheap relatively often in auctions and on ebay and would be easy to modify to fit a smaller space. Alternatively, a good engine crane modded with a wider wheelbase to span over a machine, small jib cranes over machines and a pallet stacker manual lift are all good options/combinations. A workshop with an overhead crane is a dream of mine!
 

Jelly

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I'd be thinking about making an overhead beam crane that runs the full length of the workshop. They come up cheap relatively often in auctions and on ebay and would be easy to modify to fit a smaller space. Alternatively, a good engine crane modded with a wider wheelbase to span over a machine, small jib cranes over machines and a pallet stacker manual lift are all good options/combinations. A workshop with an overhead crane is a dream of mine!
That was my starting point, but as I looked into a small 2 tonne unit that was available locally for effectively scrap value, my structural engineer friend helpfully flagged that the point loading associated with the beams supporting the carriers running along both walls, would require cost prohibitive work to set them like piles, or massive intrusive plates to spread the load.

So a lighter portal type arrangement seemed like the next best thing.

I've used workshop facilities with proper overhead cranes and it takes a vast amount of hassle out of so many simple tasks, that I figure it's got to be worth attempting to get as close as damn-it as you can in a glorified Compton garage.

I was originally looking at the engine/jib crane approach too, but ultimately decided that it would occupy too much space when not in use, I do have an external yard which can be used for laydown or assembly, but I'm reticent to use it for long term storage as it's got shared access with neighbors and isn't secure.
 

Inspector

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The only ones I have ever seen (outdoors) at a little distance and were 10 to 20 ton, running on railroad track on the ground using train wheels.
The ones in the plant I worked in, 4 bays, were 10 ton and they ran on I beams attached to the walls.

For what you want which if I understand would be the first example. I would use angle iron with it point up ^ and steel rollers either bought or turned yourself, with a matching V in them. Along one wall the gantry wheels would be set so they don't move side to side, just roll. The ones on the opposite wall the wheels would be allowed to float a little side to side to allow for variations in parallelism. I doubt they would have to move much but you wouldn't want them riding up and down one or the other face of the angle iron. Something along these lines. https://www.amazon.com/Sliding-Inve...ed3e3&pd_rd_wg=kyRRX&pd_rd_i=B07V9PS8BT&psc=1

How are you going to deal with power cords/airlines from the walls?
 

Jelly

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For what you want which if I understand would be the first example. I would use angle iron with it point up ^ and steel rollers either bought or turned yourself, with a matching V in them. Along one wall the gantry wheels would be set so they don't move side to side, just roll. The ones on the opposite wall the wheels would be allowed to float a little side to side to allow for variations in parallelism. I doubt they would have to move much but you wouldn't want them riding up and down one or the other face of the angle iron. Something along these lines. https://www.amazon.com/Sliding-Inve...ed3e3&pd_rd_wg=kyRRX&pd_rd_i=B07V9PS8BT&psc=1
That's the ticket!

From that link, I can see that they're commonly used for sliding gates (a connection I had totally failed to make), and there's a sliding gate company in the next village over who may be able to advise and sort me out with the hardware (wouldn't ask them to fab because of liability/certification issues with lifting equipment).


How are you going to deal with power cords/airlines from the walls?
Run the wiring for fixed machines in conduit/cable tray along the inside of the track from the end wall; the couple of plug-in things which need to stay plugged in are going on the end wall too.

Otherwise the plan is to tolerate having to unplug portable power tools etc. before moving the gantry, which for my use case (a one man workshop doing a mix of hobby and potentially some prototyping) is an acceptable compromise.
 

Jelly

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For the reference if anyone who might be looking for be a similar be solution in the future...

Just spoke to the gate place near me who suggested Merlin Industrial as the easiest source of both Upturned V and Flanged Rail wheels.
 

Davey44

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That was my starting point, but as I looked into a small 2 tonne unit that was available locally for effectively scrap value, my structural engineer friend helpfully flagged that the point loading associated with the beams supporting the carriers running along both walls, would require cost prohibitive work to set them like piles, or massive intrusive plates to spread the load.

So a lighter portal type arrangement seemed like the next best thing.

I've used workshop facilities with proper overhead cranes and it takes a vast amount of hassle out of so many simple tasks, that I figure it's got to be worth attempting to get as close as damn-it as you can in a glorified Compton garage.

I was originally looking at the engine/jib crane approach too, but ultimately decided that it would occupy too much space when not in use, I do have an external yard which can be used for laydown or assembly, but I'm reticent to use it for long term storage as it's got shared access with neighbors and isn't secure.
Hi, you speak of an engine (etc) hydraulic lifting crane as taking up too much space when not in use. I went this route when I knew I would need to unload and shift a newly purchased (big) lathe and milling machine from the back of a truck and into my purpose-built (small) machine shop. Having accomplished the task it folded down to use a space about 1 metre wide by 450mm deep by 2 metres tall. It stands against the garage wall and causes me no problems at all. It's available should I need it for any reason and can be made ready for action in less than 5 minutes! Hope this helps?
 

Jelly

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Hi, you speak of an engine (etc) hydraulic lifting crane as taking up too much space when not in use. I went this route when I knew I would need to unload and shift a newly purchased (big) lathe and milling machine from the back of a truck and into my purpose-built (small) machine shop. Having accomplished the task it folded down to use a space about 1 metre wide by 450mm deep by 2 metres tall. It stands against the garage wall and causes me no problems at all. It's available should I need it for any reason and can be made ready for action in less than 5 minutes! Hope this helps?
I had seen those folding engine cranes, which would certainly be less of a space hog than a fixed leg unit, but couldn't quite work out how one would fit into my desired layout easily. As compared to losing 150ish mm off the width of the workshop, which is not nothing, but wouldn't be felt in quite the same wayeven though it's probably does represent a comparable area.

I suppose in the back of my mind, I was also thinking:
"Am I sufficiently lazy that having do set it up/break it down each time I need it, will guarantee that I'll only use it for really heavy stuff, and continue to do lots of sketchy lifts by hand?"
To which the answer was a resounding yes... which is where the gantry wins out.
 

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I have a folding hydraulic engine crane and it has proven it's worth over the years. More so with my old 1990 Nissan 2 wheel drive pickup truck as it was fairly low to the ground. Unlike my 2015 4x4 by the same maker where the bed is easily a foot higher (crotch high) than the old one (knee high). So picking up anything of size like a table saw is not going to happen. The splayed out legs often got in the way when trying to get under the vehicle when positioning the hook over the load. Even picking up my 13x37" metal lathe enough to get it on/off the base is a challenge. I'm not getting rid of it because it is still useful but a gantry setup would be the cat's backside since it can lift higher and then easily move the hooked item almost anywhere in the shop even over things in the way. The advantage goes to the engine crane if you want to use it outside unless Jelly has his rails extend outside. Needs a very wide door though. I have a buddy that has a chain hoist in his shop that bolts to a heavy eye in the ceiling that can lift high but can't be moved anywhere and it suits him just fine.

Pete
 

Jelly

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I figure that it might be worth turning this in to a build thread of sorts, so to start off I might as well go through a bit of the design process I've followed.

Initially it was just a case of throwing together a vague idea of how I was thinking of assembling it from 90×90×5 square tube, and a 178×102×19 UB section in CAD.

Portal Crane.jpg


A little more refinement allowed me to model how it would be constrained in space, and how it would be loaded by the trolley carrying the hoist; which allowed me to run an FEA (Finite Element Analysis) Study:
First FEA.jpg


I'm not so interested in the numerical outputs as finding unexpected stress risers at this stage; so whilst I can see that the center of the span takes the brunt of the loading, what catches my eye is what's going on at the connection between the legs and the girder.

FEA 1a.jpg


There's a lot of stress being concentrated in a small part of the web, and in the area where two of the tubes would be welded together, which is not idea by any means... I mean this is what i was expecting, given it would be common practice to use a gusset or bracket in this area, but it's still worth visualising.

So I modeled up a simple pair of gussets and re-ran the study:

FEA 2.jpg


Which, is where having the simulation inside my CAD program comes into its own, because whilst reducing the force applied to the central weld, my initial design idea actually increased the stresses experienced by some parts of the legs.

So I modeled up a pair of stays and supporting pads which would transfer the force onto the legs lower down...

FEA 3.jpg


That reduces the overall stress levels, but produces a number of new stress risers, some of which are much more likely to result in fatigue over repeated loading cycles, so that's not ideal either.

The obvious solution was to spread the load over a plate meeting the legs, and use more box section to support the cantilever because that will result in a better distribution of stress in the supporting element. Modeling this up in fact resulted in me seeing that the stresses were so much lower for the desired loading, that I could probably re-model using smaller sections and still meet the design intent, (70×70×3 and 127×76×13 respectively) which makes it both cheaper and easier to work with... Bonus!

FEA 4.jpg


Now we've substantially reduced the stresses across the whole assembly, and moved the only stress riser which remains, into a position where it's away from any welds, and is better supported, so is less likely to result in long-term failure, which resulted in the following design.

Edit: A design which I failed to highlight actually reduced the stresses on the structure by a decent numerical margin, despite me substantially reducing the size of the sections that I'm building it from from the original design.

Portal 7a.jpg


Portal 7.jpg



Which is close enough to be worth going through the stress calculation methods for the structure, set out in the relevant standards (Either BS EN 15011 and BS EN 13001-3-1, or BS 2573-1 and BS 2573-2), including determining the appropriate factor of safety for the design, and assessing if it will meet that.

Technically I could use the FEA results as an alternative to stress calculations for safety under EN 13001, but the simulation package in my CAD software is somewhat limited, and I'm not an experienced FEA user (which is important because it's highly dependent on the user setting appropriate boundary conditions).

Anyway, I'm going to do that at some point when I have a spare 40-50 mins to set up a suitable spreadsheet, and all being well, can then produce some drawings to send to the profilers and stockholders to get quotes for cutting the required plates and sections respectively.
 
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