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Reworking a Knightwing Crane (was "The feet of a girder crane (bridge crane)")


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  • RMweb Gold

Knightwing do a kit for a girder crane (sometimes called a bridge crane) and I have one on these nearly ready to fix down onto my layout:

 

post-14389-0-25244600-1530308235_thumb.jpg

 

Please, can anyone tell me what the moulded "feet" are meant to represent? For example are they concrete pads, poured on site with the steelwork fitted onto them, or maybe even just areas of plastic for fixing down like the moulded bases on early models of figures? I cannot find one photo of a similar crane online, after searches for "girder crane" and "bridge crane".

 

Many thanks,

 

- Richard

 

Edit 11 July 2018: Title change. The topic began as an enquiry about the feet and their foundations, and became a rebuild of the whole mechanism.

Edited by 47137
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Hello Richard,

Looking at the photo, I would say there are two options possible,

One is that the plates would be welded to the Verticals and then Bolted down to a concrete base (Assuming the crane does not travel along rails ).

Usually under the steel plates would be either steel shims or a layer of Grout to 'level' out the structure.

 

If the crane was intended for some lengthwise movement  ie on wheels and rails, flanged wheel sets would be bolted to the underside of the steel plates, while the rails would be bolted and levelled ( in a similar manner to above ).

 

In either case painting the same colour as the rest of the crane after having fitted some evidence of bolt heads on top of the plates ( say every 8 - 10" inches, depending on scale ) would probably appear suitable.

 

Regards

 

Kev T

( Ex Maintenance Manager - MMC Iron Foundry )

 

PS I couldn't find much that clearly defined what I have described either.

 

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  • RMweb Gold

Hi Kev,

 

Thank you for picking this up.

 

I think, this particular crane is for a static installation, because the arrangement of the "bridge" parts (photo) gives the hoist two directions to travel - if the whole crane travelled along, the hoist would only need to travel across the width. I was previously thinking of four concrete pads, one for each leg, but your notes make me think of two long and narrow concrete foundations, like the strips of wood here:

post-14389-0-90099100-1530345293_thumb.jpg

 

I think this would look ok when painted up.

 

I have my doubts whether this kit is a model of a prototypical crane. The hoist is supported by quite tiny horizontal beams, while the vertical structures each side (where the I beams are in compression under load) look strong enough to hold much more.

 

I'll wait and see if any more ideas come to light here before doing anything permanent to the model.

 

- Richard.

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  • RMweb Gold

If the power supply is part of the kit I think that points to it being a static crane, there being no flexible connections.

 

Mike.

A very fair point.

 

I am sure it is a static crane, but it looks wrong simply "standing on the ground". I think the two concrete pads will look ok. I could even tackle some Armco beside the one on the roadway.

 

- Richard.

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A very fair point.

 

I am sure it is a static crane, but it looks wrong simply "standing on the ground". I think the two concrete pads will look ok. I could even tackle some Armco beside the one on the roadway.

 

- Richard.

I've worked in several locations which employed similar cranes, and all, as far as I remember, were bolted down on concrete slabs a little larger than the feet of the girders. Concrete extending beyond that would cost money and serve no useful purpose. The bolts, which would have been placed, thread-side upwards, in the concrete when it was being poured. The bolts themselves were pretty substantial, the nuts (double-nutted on each corner) being several inches across faces.

Similarly-arranged cranes are used for handling nuclear-fuel 'flasks' at several locations. The one at Hunterson seems similar:- http://port.hunterston.eu/nuclear_flask.htm

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  • RMweb Gold

Yes ... individual concrete slabs, not too far off the ground look right to me too. I have cut four rectangles of thin plywood:

post-14389-0-82731600-1530357638_thumb.jpg

 

The model is near the back of my work bench so usually only the camera lens gets this close - I can forgo the studs and nuts.

 

It will be good to get this model fixed down because the legs are curving inwards slightly and this will let me straighten them up.

 

- Richard.

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  • RMweb Gold

A query on your positioning of the crane, it's only ever going to unload the last wagon of a train, could it move forward a tad to enable a few wagons to run through it?

 

Mike.

I'm afraid not - the siding begins to curve immediately in front of the crane, and then starts to climb a few inches further along.

 

The crane exists on the layout to complement a cottage at the other end and provide an aesthetic balance to the whole project - I added it during early development of the layout. The whole of "Shelf Island" is based around one-wagon trains and equally minimal passenger workings, so the lack of capacity here is not a limitation; rather, the crane lets me run different wagon loads.

 

In the fiction of Shelf, the siding has been foreshortened, and used to extend beyond the timber buffer stop and along the side of the processing plant, but I haven't worked out of the history yet.

 

- Richard.

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You are certainly right about the discrepancy between the vertical and horizontal beams, however with it stood at the rear on the four concrete pads with a layer of grime (dating the original installation back before the siding was foreshortened and therefore shrouding it's design in mystery) I think a nice little cameo is in the offing.

 

Regards

Kev

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  • RMweb Gold

You are certainly right about the discrepancy between the vertical and horizontal beams, however with it stood at the rear on the four concrete pads with a layer of grime (dating the original installation back before the siding was foreshortened and therefore shrouding it's design in mystery) I think a nice little cameo is in the offing.

 

Regards

Kev

 

I fixed the crane down onto the layout today. I've put the photos on my layout topic but yes indeed - there are three angles for photographs and the ability to add trains and road vehicles to make different scenes.

 

- Richard.

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I have my doubts whether this kit is a model of a prototypical crane. The hoist is supported by quite tiny horizontal beams, while the vertical structures each side (where the I beams are in compression under load) look strong enough to hold much more...

 I cannot claim huge experience of such overhead cranes, but have never seen one arranged like that where the traversing carriage ends are inside the cross beams. (It would be structurally unsound for a start because unless my eyes deceive me the traversing carriage ends are not tied together.)

 

The more usual arrangement is that the traversing carriage is a rectangular frame running on rails mounted atop the static frame, and then the hoist unit in turn runs on rails atop the traversing carriage. There needs to be a perch for an operator too; ideally a ramshackle little hut, that looks like it is attached by pipe cleaners, pieces of scrap pipe and other junk. And a ladder with two seriously bent and one completely missing rung to gain access (authentic feature on one of the first of its kind I encountered, there was some seriously shoddy kit in use in UK industry...).

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To be honest as an ex-crane surveyor, I have never seen a structure like that in use as a crane and would have condemned it on sight. The whole design concept is wrong. There are plenty of photos of real cranes on the internet. Find one you like the look of and model that. That is unless your railway is based on Middle Earth where anything goes. 

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  • RMweb Gold

Typical. The only structure on the layout I have built from a kit is completely wrong.

 

I will live with it until I can find the willpower to start again. Fortunately the layout is not scheduled for public exhibition.

 

- Richard.

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Typical. The only structure on the layout I have built from a kit is completely wrong.

 

I will live with it until I can find the willpower to start again. Fortunately the layout is not scheduled for public exhibition.

 

- Richard.

Don't fret about it, this is railway modelling, lives don't depend on it, but like all things if you want to do it right you need to do some research. All the information is out there and photos are one of your best resources. 

The problems with this "crane" is it doesn't have a stable enough base or bracing in the right places. In the event of lifting a load it could collapse in either direction. Girder sizes need to be sized for the load they are expected to carry, not just for the load the crane is expected to lift, but also the weight of the crane and the span between supports. Also the moving bridge should sit on rails on top of the Gantry, (base), not within it. The Crab (the bit that carries the lift mechanism with the hook) should also sit on rails on top of the Bridge not within it. Otherwise the Bridge I beams (girders) would just spread and everything would come crashing down. Depending on the size of crane you need a cab for a driver or a Pendant controller hanging from the Crab or Bridge.

Lastly you need access. All cranes need a means of access for maintenance and inspection (and possibly a driver). How safe this access needs to be depends on the era you are modelling. One building I had to inspect had three cranes on the same gantry. To access these I had to walk along the rails from the ladder, this was fifty foot up and the whole gantry shook when any of the cranes were moving. Health and Safety has moved on since then. Lastly your crane must be marked with it's Safe working Load (SWL). This is just the basics on a very complex subject. A lot of model cranes I've seen (as well as bridges) would have fallen down before they got built.

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  • RMweb Gold

I have written to Knightwing, asking what they had in mind when they produced the kit. Perhaps they were thinking of something more sophisticated, and simplified the design when they put the kit into production.

 

- Richard.

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  • RMweb Gold

In the meantime, could this be acceptable? That is to say, not condemned on sight:

post-14389-0-10242500-1530861877.png

 

The white-filled parts are from the kit, the green parts two I beams rather taller than at present, added bracing in blue, and on top a travelling bridge and a crab underslung below it.

 

Nothing is completely wrong - even a clock which has stopped is right twice a day.

 

- Richard.

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Yes, you are heading in the right direction now Richard. The hoist block should run on the lower webs of the yellow "I" beam. such as shown in this web page. https://www.theratchetshop.com/hoisting-and-material-handling/chain-hoists-trolleys/plain-girder-trolley/500kg-plain-trolley.html?utm_source=google_shopping&gclid=Cj0KCQjwpvzZBRCbARIsACe8vyLIIBplGO7wj0HNWet141hzVv3BfE_9T16RhCH1AL1wV5IYlV2WbJMaAuvjEALw_wcB.

I am not familiar with the Knightwing kit you refer to and how they arrived at their design is anyone's guess.

There are a number of good crane kits on the market such as this one from Walthers. https://www.comfortplace.top/ho-scale-c-1_2_3/ho-scale-walthers-cornerstone-9333102-overhead-traveling-crane-kit-p-2368.html

The size of all components depends on what you are intending to lift.

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  • RMweb Gold

The Walthers kit looks a bit big for the space on my layout, even after hefty modification. Suppose I try to work backwards from the model I have, I could go for something like this:

post-14389-0-60012800-1530870254.png

 

I have two lengths of Plastruct I beam to hand. One is much the same size as the girders in the kit, the other is about 50% taller. Using the smaller size, the two bridge girders will scale at 435 mm deep and 174 mm wide, which is close to a stock steel section of 457 x 152. The capacity of the crane would be whatever such girders can hold. The larger Plastruct scales up to 522 x 348 mm.

 

The span is a scale 7.8 metres, and the beam height has got to be 435 or 522 mm. The task seems to be, to find out whether the larger Plastruct beam is ok with the given supporting structure. The two beams along each side of the structure do seem to have a lot of support, even though they are quite slender.

 

Having decided this, then if anyone has a beam calculator suitable for a dynamic loads (or of course a good memory or a sample crane to hand) then this would tell me what capacity to write on the crane.

 

I am looking at this as a protoype: https://www.indiamart.com/proddetail/double-beam-eot-crane-11923788648.html

 

The nice thing about this approach is I can paint the bridge in (say) yellow and keep the paint on the supporting structure unchanged. It has had three coats of paint already, tho' this is another story. Also I can keep the original 'crab'. All I need to make are the housings (dollies?) at each end for the wheels.

 

- Richard.

Edited by 47137
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  • RMweb Gold

Here is a mock-up of how my crane could be - does this look reasonable?

post-14389-0-26874700-1531040698_thumb.jpg

 

I am using the larger of the two Plastruct beam sizes because it looks better. There will be "rails" of microstrip for the dollies (trucks?) to run along, I tried some code 60 rail but it looked too coarse. I can add a ladder and a control pendant later, when I have some confidence in the general arrangement.

 

- Richard.

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  • RMweb Gold

Well ... I've gone ahead anyway:

post-14389-0-31767400-1531078253_thumb.jpg

 

This arrangement has more "play value" than the original kit because I can move the bridge and the crab. I had to glue the original solid to stop it falling apart, which probably says more than it should about the structural integrity.

 

Anyway, I want to paint the bridge yellow so it now has an undercoat in off-white.

 

Comments and ideas welcome, I am sure there is still time to change a few things.

 

- Richard.

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Yes Richard, It's looking better. Some signs of wheels for bridge and Crab would improve the look. There is more to a crab than just the hoist block, it needs a motor  for traverse as well as hoisting. The bridge itself also needs a travel motor and evidence of a control system. Be aware that open conductors and pick up shoes were outlawed several years ago, it depends when your era is set. And if you can't gain access with a simple ladder due to height, obsticles etc, you need fixed ladders, platforms, handrails, safety hoops and the like. You wouldn't want your 4mm personnel coming to grief.

 If you really want to get into it there are these documents you may be interested in,

http://www.engineering.com/download.aspx?folder=fb267e40-6538-470d...Crane...pdf

also the LOLER regulations, LOLER is not a night club artist, but the Lifting Operations & Lifting Equipment Regulations

http://www.legislation.gov.uk/uksi/1998/2307/contents/made

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