Scalefour Forum

David Bigcheeseplant wrote:Give me the info of a 9F wheel and I will pop it in and see what it comes up with.

I don't have it to hand, but I think I know who does.....

Two types that need to look like this....



...5’-0” diameter, 15 spoke, 14” throw.

Morgan

Something like this?

Just noticed I need to enlarge the centre balance weight.

I have just modified them with a bigger boss on the central crackpin

The centre axle wheels on a 9F were flangeless. The flanges on axles 2 and 4 were modified as well, although it's questionable how noticeable [or effective] that would be in 4mm.

A few mods to the 9F wheels removing the flange from the centre driver.

David

Now if the Society were friendly with a tyre supplier ...

David Bigcheeseplant wrote:I have just modified them with a bigger boss on the central crackpin

Looks almost like a set for one of the German 2-10-0s...

"Looks almost like a set for one of the German 2-10-0s..."

Why would anyone be interested in modelling those!

David Bigcheeseplant wrote:"Looks almost like a set for one of the German 2-10-0s..."

Why would anyone be interested in modelling those!

Well, if you will show them in red.....

I have added more variables into the wheel generator, I can now add the flare of the spokes into the hub and also the shape of the spokes are also adjustable and are oval or egg shaped in section.

David Bigcheeseplant wrote:A few mods to the 9F wheels removing the flange from the centre driver.

David

Are the rims bevelled? Can't see due to heavy shadowing.

On some wheels yes others no, I can just add in what angle bevel I need and it is there.

The 9F wheels have a bevel.

David

David Bigcheeseplant wrote:...The 9F wheels have a bevel.

Ah, thanks for confirmation.

Presumably BR Std. 6/7/8 6'2" wheels are also possible.

just tell me all the info with maybe a picture and I will see what I can do.

9F wheels.

Drawing of the front wheels. Sorry about the quality.



92220 intermediate front driver showing different centre boss.



92220 centre & rear Intermediate axles.



With apologies to those that have seen the images before.
The different centre to the front intermediate axle has been the subject of some debate and something I have not yet got to the bottom of. It looks as though it could have been a reclaimed centre axle that has had tyres fitted.

Hope it's of some assistance.

P

That is really helpful, is Evening Star the only 9F with the weird second driver? The Centre driver is really different to the others, I can do the variants if people really wanted them!

The wheel generator will get the wheels 98 percent there I may have to add things like fillets later but this is not an issue.

David

David,
Another key feature of BR Standard [and Stanier LMS] wheels is the triangular section rim. It's not apparent [to me] if you have incorporated this feature in your generated wheel files.
I must say, the concept of bespoke wheel design and printing does sound very interesting.
Dave.

This is all very interesting to read. But in practical terms, how much variation in design is possible? For example, how about flat fronted spokes as per Barclay wheels? One of their 'standard' sizes was 3'5" which is a bit of an oddball but I suppose 3'6" (which is a tyre size that would probably be more obtainable) could do at a stretch.

I used to get tyres from Alan Gibson BITD when I was making my own brass centred wheels for split axles. I turned the centres to be a good 'interference' fit into the tyres and, if I'd got it slightly wrong or there was a variety in Alan's inner diameter then a splash of flux and a wipe around the join with a hot soldering iron sorted it.

But would Colin provide the same service given that these wheels could be seen as being in competition with him?

I'd also like to ask how the axle holes will be dimensioned. Similar to Gibson wheels ie a push/interference fit? Does the plastic being used have the slight inherent 'flexibilty' to allow this?

A flared boss is very easy to do it is one of the parameters I can change see the two versions of the same wheel. Barcley wheels again no problem I simply change the variables in the spoke shape.


David

Enigma wrote:This is all very interesting to read. But in practical terms, how much variation in design is possible? For example, how about flat fronted spokes as per Barclay wheels? One of their 'standard' sizes was 3'5" which is a bit of an oddball but I suppose 3'6" (which is a tyre size that would probably be more obtainable) could do at a stretch.

It depends on how much time someone wants to put into doing the CAD to get the variations, flat fronted spokes should be easier to draw than oval ones. I have 3'3" and 3'6" rims but nothing in between.

But would Colin provide the same service given that these wheels could be seen as being in competition with him?

I think Colin takes the view that P4 wheels are a very small part of his business and he needs to make his money in other directions.

I'd also like to ask how the axle holes will be dimensioned. Similar to Gibson wheels ie a push/interference fit? Does the plastic being used have the slight inherent 'flexibilty' to allow this?

This is where things get interesting. There would be relatively few problems printing a Romford type wheel, but if it's finescale that's wanted then the limits of the printer and the materials start to come into play. If the wheels are to have the same sort of interference fit with the axle as injection moulded wheels then a resilient plastic is needed. Today this is usually ABS. FDM printers, that use spools of plastic wire, can use ABS, but as far as I know, very few of these machines can produce wall thicknesses down to 0.5mm, which would be needed for a tapered spoke. The other common printers like the jetted type ( Shapeways' FUD etc) and the liquid resin machines (SLA and DLP) use photoacrylic resins which in their common form is too hard and brittle to use with an interference fit. This means that a glued sliding fit has to be used with all the problems of concentricity and squareness to the axle. Oh, and most photoacrylic resins creep, meaning that within some time after printing, maybe 3-6 months, the bores close up enough to stop the axles being inserted. This is probably not what is needed when sales are made to customers that habitually salt away kits and components to use in the future.

Anyway Here are a couple of photos of work in progress. The light speckles are filings from removing the support pips. The wheels should have gone into the ultrasonic before I took the photos.

Romford type axle holes would enable the use of the semi-mythical Romford P4 axles, ensuring quartering and allowing a prototypical looking variety of axle end caps.

jon price wrote:Romford type axle holes would enable the use of the semi-mythical Romford P4 axles, ensuring quartering and allowing a prototypical looking variety of axle end caps.

These wheels have keys printed into the bore and the axles have keyways, so they are self quartering.