3D Sheaves

[DonB]

3D Sheaves.

I have a requirement for a sheave similar to Colliery headstock wheels, but rather smaller at  34mm diameter.

It would be used horizontally, have twin grooves for two 0.5mm ropes, and 12 round spokes. The centre boss to accept a 3 mm motor shaft. Maximum over-all thickness 4mm.

My computer, purchased from my employer when the factory closed with its early, and not updated Autocad program  has crashed.

So, does anyone out there have a similar wheel already drawn which I could use to get a 3D print?

I have seen larger diameter versions advertised on Ebay, but contact with the vendor did not produce a response.

Advice on the material to be specified would be welcome.

My thanks in advance for any guidance, as I venture into uncharted territory! A photo of the prototype is available but copyright prevents me posting it here.

 

 

[Etched Pixels]

There's a open source parametric tool for doing just about any wheel in OpenSCAD. There a couple of things you didn't mention - size of centre boss, spoke diameter, spacing between the two rope grooves.

 

The tool is documented at http://www.thefrankes.com/wp/?p=2674 which gives a flavour of the parameters it can take.

 

For Shapeways type stuff the constraint is about 0.8mm diameter or smaller. Which also means if your boss is 3mm hole then 4.6mm minimum diameter (or you could use a smaller motor - 1mm isn't too hard to get).

 

Give me the numbers and I'll type them into the script and press go. Assuming it works right it'll take me about 2 minutes to render and bung onto shapeways as an orderable object.

 

Alan

[Xerces Fobe2]

Until I ventured to the San Fancisco Cable Car Museum I had no idea what a sheave was! I am just wondering if anyone in the USA models working cable cars and has produced model sheaves; might be worth a Google search?

 

XF

[Xerces Fobe2]

just found this http://www.model-dockyard.com/acatalog/rb-Rigging_Block_Sheaves.html

 

XF

[Dazzler Fan]

Don B :-
 

It is possible I had your original query for Bridenorth Cliff Railway, working against the handicap of

exchanging e-mails on eBay.

 

I have supplied these to various sizes up to 100mm. This wheel has 38 spokes at 48mm

and for 3D-print limitations would have to reduce the numbers to get down to 34mm - your

12 would do it.

The cost is in FUD as the material for the detail.

 

This is the Review by Chris Nevard in Model Rail.
 

 

Regards

Noel

Edited April 20, 2015 by Dazzler Fan

[SpoorObjecten]

haha "are 'FUD' aka 'Fine Ultra Detail'"

 

nooooo it's Frosted!

[DonB]

just found this http://www.model-dockyard.com/acatalog/rb-Rigging_Block_Sheaves.html

 

XF

Thanks, I will be using their small dia. sheaves for (hidden) rope guides but need the larger spoked version to match the prototype which is visible

[Etched Pixels]

SpoorObjecten: Sure it's not 'Fragile' ;-)

 

Dazzler: Thats a lovely looking bit of work. Presumably it would also print in the new lost wax/brass process ?

[Dazzler Fan]

Etched Pixels:-

 

It is too fine for the lost wax minimum parameters.

FUD can be very brittle in cold temperatures, but has an amazing

property of returning to shape if it becomes distorted.

I think for Don's application, he needs to consider a sprung jockey

wheel to take-up any shock. For 3 ropes on the sheave in a picture

he has available, I think the rims will be fairly strong. Of course any

unsupported torque drilling the boss is likely to cause damage.

[Arthur]

I've got a couple of pairs of Noel's sheaves, the first 3D prints that I've bought, and they are very good indeed. They're one of those items you wonder how you could otherwise model.

[SpoorObjecten]

SpoorObjecten: Sure it's not 'Fragile' ;-)

 

Dazzler: Thats a lovely looking bit of work. Presumably it would also print in the new lost wax/brass process ?

 

Fragile Ultra Detail

 

Though this might be an interesting read:

http://http://www.dcyale.com/shapeways/fudmicro/acetone.html

[DonB]

Dazzler / Etched pixels:-

 

Thanks for the input and thought that you have both obviously put into this problem.

I had thought of using just a direct drive to the sheave with the two ropes on a half-wrap round two Sheave grooves. There is a suggestion that the 3D print would not support the working loads and may not tolerate a tight fitting shaft.

The carriages are to be weighted (to get them to stay on the tracks!) but are balanced with one going up the other descending, so there will be a bending force on the sheave shaft.

A quick trial with a card dummy indicated that I will need at least 20 grams ballast weight in each of the two carriage supporting structures. I'm beginning to think that perhaps I should consider having the visible sheave just as a rotating but decorative item and have robust, solid (brass?) working wheels hidden away under the building.

 

In the prototype there are three cables, one is connected to both carriages via a half-loop round the sheave, The others, one to each carriage, go via guide rollers to separate co-axial contra-winding drums on what is, essentially, a colliery-based winding capstan. Neither of these ropes goes round the sheave, which seems to date from Victorian times when the operation was a water-balance affair, so now two of the three grooves are unused.

I will have to re-visit my thoughts and look at where I can insert a drive module within the model's support structure. I need to find a sharp pencil! I will not be around much for the next couple of weeks.

[Dazzler Fan]

Don B

At 34mm diam, and 12 spokes I think if the spokes were thickend to 1mm

or more, you would have a good "shock taking"  wheel.

The drive could also have an intermediate pulley that would take up shock.

With a continuous "cables" I don't see the need for much ballast - the cables

will pull down as well as up.the incline.
 

SpoorObjecten

 

Interesting link. I think Bill Bedford has carried out similar experiments.
In general, the vegetable oil being used is a great improvement over the

previous heavy wax from Shapeways, and cleans with a good brush-up

from a toothbrush and washing-up liquid.

 

Does anyone have long term experience of various adhesives holding?

 

[SpoorObjecten]

so would you like it if shapeways offers clean models without any wax residue left knowing that your model will not be transparent but will look like WUT (white ultra detail ).

This way you shouldn't have to do any cleaning yourself, and we might be able to offer it for a lower price

 

 

edit: note i'm not referring to 2hrs with Acetone,, just a few minutes to get rid of wax and oil residue

Edited November 23, 2013 by SpoorObjecten

[Etched Pixels]

SpoorObjecten: for quite a few things yes. Most of what I do is going to arrive from Shapeways and get a good coating of primer. The 'transparent' is not very transparent anyway so it's not a useful property for me at least.

 

Also if it arrived white it would be much easier to photograph when it arrived !

[Etched Pixels]

Dazzler: I did render it with 1mm spokes based on the Bridgenorth one (I got amused by the problem and spent 10 minutes writing a generic OpenSCAD tool for producing sheaves with that kind of "bicycle" spoke pattern). It looks fine, and the prototype looks as if they spokes could easily be 3" or so. That one will print in WSF which also means it comes out very cheaply.

 

Alan

[Penrhos1920]

so would you like it if shapeways offers clean models without any wax residue left knowing that your model will not be transparent but will look like WUT (white ultra detail ).

This way you shouldn't have to do any cleaning yourself, and we might be able to offer it for a lower price

 

 

edit: note i'm not referring to 2hrs with Acetone,, just a few minutes to get rid of wax and oil residue

 

Yes please.  The frosting is actually a problem when you do not want to paint the print as it is going to be used as a master for resin casting.  Some colour would be very helpful in seeing the surface detail.

 

PS What solvent are you think of?

[Dazzler Fan]

.......so would you like it if shapeways offers clean models without any wax residue ......

They have already done this.

[billbedford]

so would you like it if shapeways offers clean models without any wax residue left knowing that your model will not be transparent but will look like WUT (white ultra detail ).

This way you shouldn't have to do any cleaning yourself, and we might be able to offer it for a lower price

 

 

To my mind the problems with cleaning FUD has nothing to do with the wax residue, but more the difference in texture between the clear top surfaces and the supported bottom ones. This is even more of a problem were there is detail on a vertical surface and the support material produces trails of rough texture under the detail.

[DonB]

Quote; (Dazzler)....' With a continuous "cables" I don't see the need for much ballast - the cables

will pull down as well as up.the incline.'

 

Sorry to disappoint, but the cables are not continuous in that way. the safety cables are just run from carriage to carriage via the (free-running) sheave under the top station platform doors.

The operating cables are attached, one to each carriage which are effectively suspended from the cables. The operation relies on gravity to lower one, whilst the other is pulled up the slope. these two ropes terminate at a capstan within the top station building, which pulls one cable while relaxing the other, hence the need for ballast in the model, the prototype carriages weigh about 6 tonnes each.

I was originally hoping to just have a couple of rope loops round a motorised sheave at the top of the slope, but comments about limitations on loading and tight fitting shafts have caused me to reconsider my choices.

I will need a sheave (working or decorative) at the top of the incline since it is a visible feature of the Cliff Railway.

[Etched Pixels]

It should be fine strengthwise in WSF. Trade off is 1mm (3" in OO) spokes and a bit of hand polishing. Bonus is its a lot cheaper than FUD and a lot more stable.

 

WSF is Nylon so you can even print gears in it (albeit not particularly fine ones do to the print resolution)

[DonB]

Just to round this thread off, Etched Pixels has now supplied the 34mm Sheaves which I required. Not only did he adjust his drawing file  (post #16 above) but also put a locating flat in the bore to match the shaft on my motor.

My thanks to him and to Dazzler Fan who also offered assistance. My thanks also to all other respondents for their interest and input.

 

Here is the supplied Sheave (Picture copyright Etched Pixels, reproduced with permission )

It is 34 mm dia. with a 3mm bore.

 

 

[Dazzler Fan]

+

With Shapeways offering of FXD material, the Sheave Wheels

are now finally available at 15' diameter for 2mm/ft. N gauge.

 

Noel

[synthnut]

Hi All,

Yes, I realise this is an ancient thread but rather than start another, it seemed more relevant to resurrect this one!

 

I'm building some colliery headstocks and have sourced the sheaves via Shapeways but am having a hard time finding any suitable plummer/pillow blocks.

Does anyone know of any suitably small plummer blocks that would work with these:

https://www.shapeways.com/product/6UXLXB9ER/pit-sheave-wheel-70-mm?optionId=57963000

I could mess about trying to create something auitable looking but I'm really suprised there's nothing more obvious being offered on Shapeways for example other than a super expensive set that I can't tell how large they are!

 

Cheers,

 

Ben

Edited June 28, 2017 by synthnut

[Gordon A]

What are plummer / pillow blocks?

 

Gordon A