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9mm:foot loco project
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 Posted: Tue Feb 14th, 2017 02:14 pm
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Paul W
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Hi Folks

I submit for your viewing pleasure, a set of wheels for a 9mil scale New Zealand Government Railways Wa-class 2-6-2T kitset locomotive project that I am working on.  This kit was created by someone else and recently purchased by me.  The kit is mostly etched brass with cast whitemetal cylinders, funnel, domes, plus some smaller lost-wax brass details.

By the way, the scale of 9mm:foot is simply what you get when O-gauge track is used to represent NZ's 42" gauge railways....actual ratio is 1:33.8666

The original etch was done from hand-drawn artwork and had some issues needing correcting so I am redrawing it using CAD, tweaking some details as I go, but that's a story for another post.  Getting back to the wheels, the kit had used cast whitemetal centres fitted with 10-thou styrene insulating strips, and the thought of the time and effort to machine these gave me nightmares so I decided to have a thrash at producing 3D-printed centres.

Initially prepared to use the more expensive Frosted Detail resin, I was pleasantly surprised to find that it is possible to meet the design requirements of Black-Strong-Flexible and still produce a good-looking wheel.  Not only have I saved myself a huge amount of time at the lathe, but the centres have the correct placement and number of spokes along with correct counterweights, are already the right colour, self-insulating and dirt-cheap - only US$3 each, not including the tyre. 

While some may find the slightly rough texture objectionable, personally I think this is not a problem, resembling as it does the texture of sand castings.  If anyone wishes to have cast metal centres made, they are welcome to, but my goal is to produce an affordable, easy-to-assemble kit to attract newcomers to pick up this scale, and these wheels have made a huge contribution towards achieving this, saving around NZ$120-$180 over the cost of machining metal centres.

Regards
Paul Woods

Whangarei, NZ.

Attachment: WA-class driving wheels - Copy.jpg (Downloaded 87 times)

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 Posted: Tue Feb 14th, 2017 03:51 pm
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W C Greene
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Pretty cool drivers. Rough castings? Have you ever looked at a real steam loco's drivers? Rough "as a cob" as we say in Texas.
Interesting thread, please continue.

Woodie



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 Posted: Tue Feb 14th, 2017 03:59 pm
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Paul W
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Just for good measure, here's a set of drivers for an O-scale TH&B Berkshire, my point being, it is so easy to draw exactly the centres you need and have them printed for beans; no more 'near enough' or not building something at all because you can't get the right drivers.

Regards
Paul Woods


Attachment: TH&B berkshire wheels - Shapeways plus Protocraft tyres - resized.JPG (Downloaded 84 times)

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 Posted: Tue Feb 14th, 2017 04:19 pm
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Paul W
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W C Greene wrote: Have you ever looked at a real steam loco's drivers?

Woodie

Yes, quite a bit, as it happens.  I'm lucky enough to have grown up around the Glenbrook Vintage Railway and the several steam locos kept there so I got to handle The Real Thing until job and family finally led me away.  Here's the wheels of our largest loco, a 108-tonne 4-8-2.

Regards
Paul

Attachment: Ja1250 wheels.jpg (Downloaded 84 times)

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 Posted: Tue Feb 14th, 2017 09:48 pm
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Robert Comerford
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Looks good to me Paul. The price of the centres seems more than reasonable. I guess it is having access to turned tyres that helps.

So what have you done to prevent the centres moving on the rims? Superglue?

I want at least one set of drivers for a 38 class at some time. I'm not happy with using the small Slaters BFB wheels as some have used. Don't look right!

I had a picture of a Kb hanging from my wall for many years.

cheers
BobC

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 Posted: Wed Feb 15th, 2017 01:05 am
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Paul W
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Robert Comerford wrote: Looks good to me Paul. The price of the centres seems more than reasonable. I guess it is having access to turned tyres that helps.

So what have you done to prevent the centres moving on the rims? Superglue?

I want at least one set of drivers for a 38 class at some time. I'm not happy with using the small Slaters BFB wheels as some have used. Don't look right!

I had a picture of a Kb hanging from my wall for many years.

cheers
BobC

Hi Bob

Slow-setting superglue works fine so long as you roughen inside of tyre with fine sandpaper and thoroughly clean outside of plastic centre with acetone and then avoid handling with bare hands - standard workshop practice.  I thought about loktite, but realised that usually only heat breaks a loktite bond - not good for a plastic centre - whereas soaking in acetone will eventually soften superglue.  I felt that this would be a useful feature in case a user wore a tyre out or perhaps needed to change the wheel profile.

I have class 38 plans as drawn by Greg Edwards, 1973, in my hands right now, and I'm guessing you are talking about 7mm scale judging from your reference to Slaters - what size axle you want with those?  BFB wheels, OMG what were they thinking?!  Wrong diameter, wrong pattern spokes!  Slaters will happily sell 5'9" mild steel tyres from their range.

Apparently it will not be too much longer before the sole surviving Kb runs again; Mainline Steam in Christchurch have been working on restoring #968 for quite a while now.

Regards
Paul Woods

Whangarei, NZ

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 Posted: Wed Feb 15th, 2017 04:21 am
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Robert Comerford
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Sorry, yes 7mm scale.
I don't even have one in HO these days, sold the DJH one I built to a friend. :>(

Sometime in the future when I have finished all the other projects I will look into building a 38 (or two).
If Slaters are still in business by the time I get around to it perhaps the tyres from Slaters and my doing the centres in the manner you have outlined would be the solution.

I would probably use a 3/16" axle. What diameter are you using?

I have built most of my stuff using Slaters wheels,I have a few items with North Yard, Roxey and Easybuild too. Most of the Lima items are running with their original wheels, work well in the great outdoors.

A Canadian Berkshire in 1/4"??

Maybe when I finally get across the ditch I will be able to see 968 in steam :>)
regards
BobC

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 Posted: Wed Feb 15th, 2017 10:00 am
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Paul W
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Robert Comerford wrote: I would probably use a 3/16" axle. What diameter are you using?

A Canadian Berkshire in 1/4"??

BobC

The standard axle size for 9mil scale is 5mm.  However, the beauty of 3D printing is that I can easily do a 3/16" version for you, 5mm for someone else, 1/4" for a third joe; it only takes a couple of button clicks and then maybe ten minutes to output another .stl file to send to Shapeways.  I could then turn around and run the same CAD file in 1/32 scale.

The Berkshire is a somewhat convoluted story; I am modelling the South Pennsylvania Railroad, which was to have been part of the New York Central empire but was stopped part-way through construction in the 1880's.  This allows me to free-lance to a certain extent while still modelling the NYC, of which I have long been a huge fan.  I wanted a grunty-looking freight engine but don't like the Boston & Albany berks much.  Salvation came in the form of another NYC-influenced railroad, the TH&B, with its pair of very handsome berks which were based on a C&NW design, plans for which I found in a Model Railroader mag.  Simple, huh? :Crazy:

Regards
Paul Woods

Whangarei, NZ.

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 Posted: Wed Feb 15th, 2017 11:15 pm
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Robert Comerford
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I'm running modified Fowlers on my railway so I won't argue with your logic Paul :>)

Further to the boxpok wheels. A now deceased manufacturer showed samples of some 38 class drivers from Slaters as part of project to have a kit done. He died before the project was finished. I enquired some time later(twice)of Slaters if they were able to supply these wheels. Never got an answer.

The BFB wheels are generally to be seen on Col Shepherd/O Gauge House 3-rail models that have been converted to 2-rail.

cheers
BobC

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