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

[47137]

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

 

Thank you for all of this. I do know of LOLER through my work, though I have avoided much actual knowledge of it by telling the client to get a contractor to do a lift (using their mobile crane), not simply provide hire of a crane. My layout is set in June 2012, but located in a fictional British Crown Dependency where a great deal of modern legislation has not really come home. Nevertheless, I will try for something plausible if a bit simplified.

 

My model has an electrical control box on one leg of the supporting structure, this is the leg nearest the camera in my photos. I imagine a looped cable harness for the crane above this, but hidden from view on the inside of the front of the supporting structure. Then a second harness for the crab, this harness along the far side of the bridge. So I can try to add two motors, but ignore the wiring harnesses because I will never see them.

 

I can also try for a walkway across the top of the supporting structure, at the far (left) end. This would be parallel with the bridge. The bridge can be parked beside the walkway for maintenance. A ladder giving access to the walkway.

 

I ought to be able to manage a representation of wheels for the bridge. The layout is 3.5 not 4mm scale, so some details do get rather small and it may be best to ignore them. The main thing for me is to put detail I know is right or at least plausible, but not spend effort on things which are wrong or difficult to see.

 

I will report progress when I have glued more parts into place.

 

- Richard.

[47137]

I have added three "motors" and an access platform. The idea is, the access platform is sufficient for scheduled maintenance on the crab and hoist; a more thorough overhaul will use portable access equipment:

 

 

 

The access platform has toe boards so hopefully the model HSE people will see, the model is fully compliant with all applicable regulations and no detailed inspection is called for. The toe boards hide the thickness of the plastic platform too.

 

The narrow brown strips are supposed to be metal rails for wheels to run on, not bus bars.

 

The yellow paint is two thin coats of Revell "Aqua" brushed on, this is the best-covering yellow paint I have ever used. It is more muted than (for example) my Railmatch warning yellow, so it gives a slightly faded look to the model before adding weathering.

 

I will leave the ladder until I can find a plastic one in proportion to the railings. Putting an etched brass one makes the railings look too chunky.

 

I need to touch in some of the paint, but I think this is a fair transformation from what I started this topic with.

 

- Richard.

[PhilJ W]

Brian is quite correct in post #6, it is the type of crane used for transfering nuclear flasks from road to rail. It is very like the one at Southminster and may even be based on that prototype.

[34theletterbetweenB&D]

... 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...

 So when did riding the hook get outlawed? I love pictures from the 1930s showing merry groups of visitors to railway exhibitions being hoisted by a breakdown crane in an open container.

[Scottish Modeller]

Hi all,

 

This particular model was done for Knightwing and based on a real one that used to be in the Indutrial Estate near the Heljan factory by CRH Concrete.

 

I've checked Google Earth and the thing has gone totally!

 

Not even a trace of the concrete bases it was mounted on.

 

It was used to trasfer palletised loads from the ground onto vehicle trailers for delivery.

 

The palletised loads were moved around the yard by fork lift and positioned under the crane ready for loading.

 

Hard to think it was 30 years ago since this was first introduced.

 

Thanks

[47137]

It would be great to see a photo of the prototype for the Knightwing model.

 

At the end of the day, I think my layout is better-suited to a crane in the style of a nuclear flask crane (fewer but heavier lifts) but still, the cane for palletised loads at Heljan would be good to see. Perhaps the person who drew the instructions for the kit made a mistake, and the original longitudinal bridge (traversing carriage) was intended to run on top of the girders and not inside them. This frame did have end pieces (see post 13), but they were not very easy to see in my photos.

 

- Richard.

[Scottish Modeller]

It would be great to see a photo of the prototype for the Knightwing model.

 

At the end of the day, I think my layout is better-suited to a crane in the style of a nuclear flask crane (fewer but heavier lifts) but still, the cane for palletised loads at Heljan would be good to see. Perhaps the person who drew the instructions for the kit made a mistake, and the original longitudinal bridge (traversing carriage) was intended to run on top of the girders and not inside them. This frame did have end pieces (see post 13), but they were not very easy to see in my photos.

 

- Richard.

Hi Richard,

 

I've asked Mel if he still has the original photos that were sent before it was produced.

 

Unfortunately he is a bit of a Luddite when it comes to the internet and emails.

 

Some one at Knightwing will have to print the email and give it him......

 

Thanks

[47137]

In the meantime while we wait and see if Mel replies, the main thing left for my crane is to decide on its capacity. This is a bit "cart before the horse" but I have tried to do the rebuild while keeping the fixed structure as I originally built it.

 

So:

 

Brian is quite correct in post #6, it is the type of crane used for transfering nuclear flasks from road to rail. It is very like the one at Southminster and may even be based on that prototype.

 

 

... 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. 

 

... Lastly your crane must be marked with it's Safe working Load (SWL).

 

 

A nuclear flask weighs around 50 tonnes ... I agree there is very much a family resemblance but I think my crane is a bit smaller. I based my bridge assembly on a drawing from a web site in India, and I think this showed a general-purpose crane not one specifically for flasks.

 

A forty foot shipping container weighs about 4 tonnes (tare) and has a carrying capacity of say 26.5 tonnes so 30.5 tonnes in all. Add a 10% margin needs a crane capacity of 34 tonnes. This would be a reasonable maximum load on my railway.

 

My bridge crane has two girders, height 6.5 mm and span 91 mm, representing prototype dimensions 570 mm x 7.9 m. Can anyone tell me, does 34 tonnes look reasonable or is it way too much? I cannot find any tables for dynamic loadings of steel beams, at least free ones. Then I can mark the SWL on the model.

 

 

 

... 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. 

 

The pendant can follow another day, but I have added a ladder:

 

So if I could put the SWL on a notice on the framework at this end (or possibly on the bridge itself?), I think I can consider the model finished.

 

- Richard.

 

 

[47137]

In the meantime while we wait and see if Mel replies, the main thing left for my crane is to decide on its capacity. This is a bit "cart before the horse" but I have tried to do the rebuild while keeping the fixed structure as I originally built it.

 

So:

 

A nuclear flask weighs around 50 tonnes ... I agree there is very much a family resemblance but I think my crane is a bit smaller. I based my bridge assembly on a drawing from a web site in India, and I think this showed a general-purpose crane not one specifically for flasks.

 

A forty foot shipping container weighs about 4 tonnes (tare) and has a carrying capacity of say 26.5 tonnes so 30.5 tonnes in all. Add a 10% margin needs a crane capacity of 34 tonnes. This would be a reasonable maximum load on my railway.

 

My bridge crane has two girders, height 6.5 mm and span 91 mm, representing prototype dimensions 570 mm x 7.9 m. Can anyone tell me, does 34 tonnes look reasonable or is it way too much?

 

No response.

 

I have studied a crane at the Museum of Power at Langford (Essex):

 

The girders are similar sizes to those on my model, but the span is 15 metres not 7.9 metres. The SWL is 10 tons, marked up on one side of the bridge. So all other things especially the strength of the supports being equal I suggest a SWL of 20 tonnes for my model, not 34 tonnes.

 

Thinking about the poor state of some of roads on the island, a 20 tonne lift sounds better. This is rather less than the maximum weight of a 20-foot shipping container, which is around 23 tonnes.

 

This leaves this topic waiting for a response from Mel, or of course a reply from Knightwing to my email.

 

- Richard.

[47137]

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. (...)

 

I have stumbled upon the wiki at steelconstruction.info and there is plenty here for anyone making a model bridge. In particular, the site shows the usual depth of a girder to be in the range span/20 to span/30, with span/20 for a simple span.

 

To my mind, the loading on a bridge is a combination of the traffic (dynamic) and of the bridge itself plus any stationary vehicles (static). The crane also has both dynamic and static loadings but in different proportions.

• For the bridge of my crane I have (mm) 92 / 6.5 = 1/14, with the load spread over two close parallel beams
• For the supporting structure I have 28 / 5.5 = 1/5, at the greatest unsupported location

So I suggest, my rebuilt model represents a structurally sound crane with sensible proportions. I am happier with this than a copy of an actual prototype, not least because I had built and glued down the supporting structure before the rebuild. But - I still don't know what the prototype chosen by Knightwing looked like.

 

The web site at steelconstruction.info is a really good resource for model bridges.

 

- Richard.

Edited September 2, 2018 by 47137