Chain routing for simple hoist / crane

[BroadLeaves]

I'm having a go at building the Ratio 543 hoist - and in a wild departure from the norm I've actually read the instructions first! However, I'm a bit confused...

There's a good image of the finished thing here: https://www.southdevonrailway.co.uk/wp-content/uploads/543_1.jpg and it's how the chain goes around the two mail pulleys that's confusing me. It appears to be one chain from the bucket, over the pulley at the end, round the smaller central pulley and then down and back up in a loop to finally go over the larger central pulley.

Metcalfe do a very similar looking item https://www.metcalfemodels.com/product/po540-00h0-goods-yard-crane/ and that has the same chain routing, and even looks more-or-less the same, so I'm assuming these are based on an actual real-world item somewhere.

The problem I've got is that I can't see how it would actually work. As there's just one chain, where's the mechanical advantage to make raising and lowering the load easier? Looing at the image from the Metcalfe site, which is probably clearer, as it shows more of the chain itself, if the bucket is in mid-air, what stops it dropping to the floor and making the loop that runs between the large and small pulleys smaller? Surely the chain would just slide over the smaller central pulley under the weight of the load? To lift it up, a person would have to pull down on the left-hand chain with the same force required to lift the bucket, so what's the point of the larger pulley?

I think I must be missing something obvious here, but I can't see what.
 

[Grovenor]

The pictures are not clear, especially the Metcalfe one which has the chain on the large pulley falling off.

There are two chains, a loop round the large pulley. The chain from the load is wound up onto the small pulley.

The difference in diameters gives roughly a 3 to one advantage when pulling on the loop to raise the load.

[BroadLeaves]

35 minutes ago, Grovenor said:

There are two chains, a loop round the large pulley.

That's what I would have expected, as it would give a mechanical advantage in the ratio of the two radii as you say.

However, for both images, I think there's only one chain (and there's only one chain in the Ratio kit, and the instructions make no mention of cutting it or making a loops). For the Metcalfe image, if you start at the top of the larger pulley and follow chain down and to the right and then back up again on the left, it lines up with the smaller pulley, so it's definitely not a loop. The Ratio image shows, as far as I can see, the same thing.

For the smaller of the two central pulleys, the chain is only making contact with a quarter of the circumference, so will have no "grip" on the chain at all, unless it's wrapped around multiple times and the instructions don't show that at all. The Ratio and Metcalfe models are very similar so I'm assuming they're both based on a prototype somewhere (rather than one manufacturer copying the other).

The instructions for both kits imply that one end of the chain is fixed to the rim of the larger pulley and that, in isolation, seems sensible. If a loop of chain was just placed over the large pulley and not mechanically attached to it somehow, I can't see the friction between the chain and the pulley being anywhere near enough to turn the pulley and lift a load. I can't find an online copy of the Radio instructions, but the Metcalfe ones are at https://www.metcalfemodels.com/wp-content/uploads/2018/10/PO540_instructions.pdf 

The whole thing makes no sense!

[Grovenor]

The problem being with the kit instruction writers not having understood what they have made. IMHO

The large pulley will have teeth so that the loop does not slip, there are special designs for these teeth to fit with chains.

The other chain will be secured to the small pulley (drum really) so it winds onto it when lifting. The drum has to be designed to take the amount of chain needed for the maximum lift, not a lot with these sort of cranes.

The way the instructions suggest there is no possible way for the operator to raise the load. 🙂

Ps. There also needs to be another control to lock and release the pulleys.

 

The ratio one does get rigged correctly, although with a triple reduction gear it will take a heavier load but be much slower. https://www.buffersmodelrailways.com/ratio-531-yard-crane-plastic-kit-oo-scale

Edited August 12, 2023 by Grovenor

[bécasse]

These cranes are intended for use inside goods sheds, not outside in the yard. The ones that I have been most familiar with had a hand-cranked geared arrangement at waist level to lift or lower the load (which would often have been of only a few cwt), the chain then passing right round the "large" wheel above a couple of times before continuing over the pulley to the weighted hook. The ones that you depict appear to require the chain itself to be hauled in or out rather than providing a geared arrangement and they would have been very restricted in the weights they could lift, although still potentially useful within a goods shed.

 

There are a few photos of goods shed cranes on the internet but the real things were notoriously difficult to photograph inside poorly lit sheds and the shots available don't appear to be especially useful. Lack of readily available prototype information was probably an issue when Ratio and Metcalfe set out to make their models. I have attached one of my own photos of the interior of the goods shed at Ventnor IoW which shows the pair of cranes that were provided.

 

[Jeremy Cumberland]

Both models seem to be fundamentally flawed in that there is no room on the small pulley (which should be a drum, as @Grovenor says) to wind on any length of chain. If chain isn't wound on the pulley, then 1/4 turn, even with shaped grooves so the pulley acts as a sproket, is hardly enough grip to lift a load. And why chain for the hook, rather than rope? Chain's a lot heavier, and it's all dead weight that needs to be lifted, as well as lifting the load. I suppose if the chain comes down vertically at the back of the pulley, then it would act as a counterweight, and although I can conceive of a way of rigging it - taking the chain from the small pulley down to the operator then back up over the back of large pulley (which also needs to be a sprocket), then down the front to a neat pile of chain on the floor - it is far from satisfactory. Until someone finds a photograph of a prototype, I can't believe that something like this ever existed. The Ventnor goods shed hoists in @bécasse's post use windlasses, which were a lot more commom than chains from what I've seen in photographs.

 

The basic principle of using a chain and sprocket for lifting is fine - modern hand-powered hoists use them, but with rather fancier gearing - but I'd expect a lot more than 3:1 mechanical advantage otherwise 5 cwt would be about your limit, and that would need someome over 13 stone, and the only thing holding up the load is the grip of their hands on the chain.

 

The Peco/Ratio 531 Yard Crane uses a chain and sproket (I wonder if it is actually modelled as a sprocket), and looks like it is based on the crane at Midford (photo from Mike Arlett's The S&D at Midford, found in another RMWeb post). It's got far more than 3:1 mechanical advantage:

 

 

[BroadLeaves]

@Grovenor @bécasse @Jeremy Cumberland

Thank you all for your replies. You've confirmed what I was thinking, and I'm now wondering if in fact one manufacturer made the model and the other copied it, given the lack of prototype information and that it wouldn't work anyway.

 

1 hour ago, Grovenor said:

The problem being with the kit instruction writers not having understood what they have made.

Yes, I suspect that's the case.

 

1 hour ago, bécasse said:

I have attached one of my own photos of the interior of the goods shed at Ventnor IoW which shows the pair of cranes that were provided.

That's very useful. I failed to turn up any real photos - all my searches came back with pictures of models.

 

35 minutes ago, Jeremy Cumberland said:

And why chain for the hook, rather than rope? Chain's a lot heavier, and it's all dead weight that needs to be lifted, as well as lifting the load.

Indeed; a very valid point.

I shall, I think:

• Loop a chain solely around the larger pulley. Teeth interfacing with the chain will be rather hard to model, so those will have to be imagined!
• Wind a rope around the smaller pulley, (or drum as it's now more accurately called) and run that along the jib and down to the hook.

The intention was to put this outside, rather than in a goods shed, and with a dose of Rule 1, that will most likely still happen (mainly because in the location it's intended for, there isn't room for a goods shed), but I may well get an 531 kit too and have one that actually works properly, as it were.

 

[MartinRS]

I have found prototype pictures of a similar crane, now at the site of the former Lancaster Green Ayre Railway Station. The chain is missing on most images though the photographs do show a drum.

 

See these links:

https://rogerfarnworth.com/2020/02/28/lancaster-green-ayre-railway-station/

 

http://www.lancasterrailwayclub.co.uk/?page_id=121

 

https://en.wikipedia.org/wiki/Lancaster_Green_Ayre_railway_station
(Photograph from https://www.geograph.org.uk/photo/35058)

 

https://www.geograph.org.uk/photo/1710874 (Information here says the crane came from Hornby. (Try searching for Hornby station and you end-up in Margate, not Lancaster!)

 

http://www.chiark.greenend.org.uk/~owend/I/R/stnpages/lancastergreenayre.html

 

 

 

https://yourmodelrailway.net/gallery/1459/1459_122242_360000000.jpg

The other impracticable feature of the Ratio and Metcalfe models is the lack of any mechanism to rotate the jib.
 

[BroadLeaves]

6 hours ago, MartinRS said:

I have found prototype pictures of a similar crane

Excellent - thank you.

http://www.chiark.greenend.org.uk/~owend/I/R/stnpages/lancastergreenayre.html is particularly useful. I'm assuming the ring set into the ground is for the hook or whatever is at the end of the rope, and then the rope is pulled taut as a way to stop the hook swinging about when the crane is not in use. I may well add one of those in.

 

6 hours ago, MartinRS said:

The other impracticable feature of the Ratio and Metcalfe models is the lack of any mechanism to rotate the jib.

The model has the ability for the vertical post to be mounted so that it isn't square to the base plate, but as you say, there's nothing on the model to rotate it, other than maybe dragging it by the hook on the end of the jib, which sounds less than ideal and most likely not what happened in reality.

[jim.snowdon]

These cranes were either built into the structure of the goods shed, or supported by two diagonal stays reaching to the top of the vertical post. They were not self-supporting, but supported between top and bottom pivots. Rotating the crane was a matter of pulling jib round by hand, if not by the hook then by a rope attached to the end of the jib. The job of the crane was simply to lift that which couldn’t be manhandled, nothing more. Everything else was what goods porters were employed to do.

 

[MartinRS]

6 hours ago, BroadLeaves said:

I'm assuming the ring set into the ground is for the hook or whatever is at the end of the rope, and then the rope is pulled taut as a way to stop the hook swinging about when the crane is not in use.

Yes, I think you are right. I have never noticed the use of an eyelet or (in the case of Beamish) an inverted U to hold the jib steady when not in use.

I think I can just make out an iron loop in a photo of Kenilworth station goods yard. The suspended chain is not vertical. The inverted U is clearly visible in the Beamish photo.

 

I have never seen either feature modelled.

 

https://www.warwickshirerailways.com/lms/lnwrk2066.htm

 

 

[Wickham Green too]

10 minutes ago, MartinRS said:

... The inverted U is clearly visible in the Beamish photo. ...

I hope that's loose so it drops out of "Trip Hazard" zone when not in use !!?!

[Rowan]

I have just started making the Ratio 531 kit and my already diminished head of hair is even more diminished! In all my years of making kits of various types and materials from various manufacturers I don't think I have ever encountered such badly written/drafted instructions! There is no substantial guidance as to the optimum sequence for assembling the kit. I am not even halfway and already I have had to dismantle parts many times to enable me fit other parts in place. My guess is Peco have made the classic mistake of not having a someone unfamiliar with the product test both the kit and the instructions. Can anyone kindly point me in the direction of some clearer instructions I can download? Thanks.

Edited February 24 by Rowan

[Michael Hodgson]

On 13/08/2023 at 21:54, Wickham Green too said:

I hope that's loose so it drops out of "Trip Hazard" zone when not in use !!?!

Trip hazard??   Unlikely.  Health & standards in their era were "Look where you're going"

[Wickham Green too]

Even so it wasn't good for business having your staff hobbling about with broken ankles ! ☹️

[BroadLeaves]

On 24/02/2024 at 09:30, Rowan said:

Can anyone kindly point me in the direction of some clearer instructions I can download?

 

I can't point to anything you can download, but I can tell you how I'm planning to tackle it. My progress has been... well, if it speeded up a bit, it could be described as glacial! So far, everything is off the sprues and painted, but not yet assembled.

I've taken a photo of the parts laid out on one of my "bits" trays. It's come out a bit dark, but hopefully it will show which parts I'm referring to.

My approach is going to be:

1. Fit pully C between plates B
2. Fit this assembled piece onto the end of the jib at A
3. Glue the reinforcing plates G to the sides of the main post at I, level with the top of the jib (make sure the one with the pulley mounting hole is the side you want the main pulley, with the mounting hole towards the top)
4. Push pin D all the way through pulley E and then through pulley F
5. Trim the remainder of the pin so that only about 0.5mm is protruding from the rear of the smaller pulley F
6. Glue the two pulleys to the mounting plate. The instructions say to drill into the plate - my plan is to not do this, but just glue it to the plate, setting the small pin into the mounting hole in the plate (this is why the pin was trimmed in step 5)
7. Wrap some cotton around pulley F and thread it over pully C and down to the hook (not shown)
8. Use fine chain from Scale Model Scenery ( CX006 ) instead of the supplied chain, which is far too coarse and make a loop, placing it over pulley E
9. Finally, mount the hoist to its base H

 

[melmerby]

On 12/08/2023 at 21:32, Jeremy Cumberland said:

The Peco/Ratio 531 Yard Crane uses a chain and sproket (I wonder if it is actually modelled as a sprocket), and looks like it is based on the crane at Midford (photo from Mike Arlett's The S&D at Midford, found in another RMWeb post). It's got far more than 3:1 mechanical advantage:

The kit has just a grooved wheel and the mechanical advantage is about 12:1

 

On 12/08/2023 at 22:11, BroadLeaves said:

The intention was to put this outside, rather than in a goods shed, and with a dose of Rule 1, that will most likely still happen (mainly because in the location it's intended for, there isn't room for a goods shed), but I may well get an 531 kit too and have one that actually works properly, as it were.

With the Peco Kit

"working" is a euphenism for "the parts rotate"

The gear wheels are eccentric so fit together 'sometimes' and the teeth are not well formed.

 

On 24/02/2024 at 09:30, Rowan said:

I have just started making the Ratio 531 kit and my already diminished head of hair is even more diminished! In all my years of making kits of various types and materials from various manufacturers I don't think I have ever encountered such badly written/drafted instructions! There is no substantial guidance as to the optimum sequence for assembling the kit. I am not even halfway and already I have had to dismantle parts many times to enable me fit other parts in place. My guess is Peco have made the classic mistake of not having a someone unfamiliar with the product test both the kit and the instructions. Can anyone kindly point me in the direction of some clearer instructions I can download? Thanks.

It wont work when assembled anyway (see above)