1:24 Heywood Wheel & PAP Project...

[RoughboyModelworks]

Here's a quickie Cobalt rendering of the Heywood wheel center for the Brake Van (superstructure design is covered in another thread). I'm thinking this will be a good test for the PAP process. I'm pleased with the center structure itself, it's taken directly from the prototype profile (the cross section profile was simply converted to a curve and revolved around the axle center to form a solid), but I'm not happy yet with the lettering. It's going to need more work. For one thing it's too small and the letter spacing is not correct. Unfortunately I'm having difficulties controlling the letter spacing in the 3D program so it's going to take a little more work. I may layout the text in Illustrator and input it into the CAD software though that may cause issues extruding the text... need to experiment.



The plan is to "print" 4 wheel centers on a sprue (enough for one van) and stack four or five sprues, whatever will fit within the size limitations of the PAP process thereby printing enough centers for four or five vans at once.

Paul

[marc_reusser]

Ahhh...now I see the wheel (very cool btw.).....that means part of my comment to you on FB is not going to be fully applicabale (I thought it was spoked)....I don't think that the PAP resolution is going to really print the letters.....I could be wrong though it did wonders on Chucks gas pump. Give it a shot....it can always be sanded out if it doesn't come out clean.

So lets talk sprue....what are the dims on this part?


Marc

[RoughboyModelworks]

No, not spoked... actually a very simple wheel. We could chrome them and make some baby moons... Chuck's success with the lettering for his pump is what is encouraging me with this part. I'm going to redo the lettering to make it larger before I proceed with the printing. If it doesn't work, I'll just sand it off as you suggest, but I'm hoping I'll get something visible. It also occurred to me I could make the lettering deeper as well as larger, thinking it could always be sanded down in the jeweler's lathe to the height desired.

The wheels are tiny. In 1:24, the outside diameter is .5625" (13.50"), width below the tread .125" (3"). The centers are the same width but slightly smaller in diameter.

I'm thinking four centers per sprue, printed horizontal to get the smoothest surfaces on the visible faces. I'm also thinking the center will attach to sprue arms at the back of the hub (leaving a partial axle hole on the front of the wheel center that could be bored out on the lathe). The sprue arms would make a right angle turn below the wheel center and connect to a main central sprue. This would form a layer maybe 1/4" high overall. I think this would be preferable to having the sprues attach to the outside diameter surface of the wheel center. I want to keep that as true as possible requiring minimal cleanup.

Here's a quick view of the back of the wheel center. I'm thinking the sprue will extend out of the axle hole on this side.



Paul

[marc_reusser]

The L shaped arm connecting sprue sounds like a good idea...You would probably not need to lap it into the cener hole much at all...maybe .010 at most...that like you say could be easily machined out. I think with the sprue connector like you mention, you could easily do all 4 sets of 4 wheels off of (1) .125 square vertical center post (4 wheels stacked off each surface/side of the center post), the L for the bottom 4 wheels forming a cross stand so to speak. The whole setup would take up about as much room as my recent print excercise.

Ine thing to consider re. the outside surface of the wheels, is again the texture...you may want to make the surface there somewhat thicker, so you can machine or surface it,  perfectly smooth and to the exact dia.

M

[RoughboyModelworks]

Yes Marc, that's what I'm thinking. Returned to the lettering problem again this morning and as yet no good solution. I laid out the lettering in Illustrator and converted it into a dwg file which I then imported into Cobalt. However, the lettering is set round a 5 inch dia. path and when I imported it, that path converted to one 12 feet in diameter ... ahh, that's not going to work, so I'm still experimenting. Very frustrating...

The thin cross section on the outer rim of the wheel center is 1/2" thick at the outside edge on the prototype which translates to approx .020" thick in 1:24... perhaps a little thin. I'm actually rethinking the scale of this project. In 1:24, the van's overall dimensions would be 1.5" W. x 3" long, pretty tiny and challenging to reproduce all the joinery in the superstructure. I'm starting to think that it would be better in 1" scale, certainly easier on these old eyes. It would still be small 3" x 6" but I wouldn't have to make as many compromises on the details.

Paul

[eTraxx]

Maybe come from it in another direction .. determine what finished size you would like .. and then figure the scale to get that size

[RoughboyModelworks]

Here's a quick view of the wheel with tire in place... just wanted to see what the full package looked like.



That's a good point Ed and is what has me thinking about 1" scale, doubling the size. The overall grandiose and life-long plan is to build the Brake Van, followed by a couple of the goods wagons and then the locomotive Katie all to be displayed on a diorama of the Belgrave engine shed on the 15" gauge Eaton Hall Railway, ca. 1896. The rolling stock is all diminutive so well suited to the larger scale. The locomotive is only 8' long x 3' wide. The engine shed however at 39 ft L., 20 ft W. & just under 17 ft H. would be fairly sizable at that scale. The more I think about it, the more I believe it would be the best way to do the subjects justice.

Paul

[RoughboyModelworks]

I've made the decision to change this project from 1:24 to 1:12 due in large part to the diminutive nature of these prototypes and the precision standards I have in mind for these Heywood pieces. Since I intend to replicate the prototype joinery work in the superstructure, the larger scale will aid that process. The parts to be printed by PAP have some very thin cross sections which would be problematic in 1:24 but substantial enough in 1:12 to allow for any necessary clean-up or truing. Meanwhile... back to the cast lettering issue on the wheel centers.

Paul

[james_coldicott]

Paul,

wow! A big decision but one that I'm sure will add to the appeal of the project.

One thought I had whilst catching up on your progress with the wheels... have you considered adding the tyres to your drawings for Print a Part and then getting the wheels investment cast in Nickel Silver? May be a less relevant idea in 1/12 due to cost and as you will also have larger mating surfaces but is true to the one piece nature of the original wheels and may end up saving a lot of time... just a suggestion!

Regards

James

[Carlo]

Wow!
Great move, Paul. I'm excited to see what you can do at 1" scale (my preferred scale, too).

For wheel rims, you should check out Gary Watkins (Sierra Valley Enterprises). He is the de-facto standard wheel maker for 7/8" and 1" scale, and he could probably CNC the wheel rims and axles for you, in steel, to your specs. Tell him Carlo sent ya.  http://www.sierravalleyenterprises.com

Also, I believe that there are lost wax brass Heywood parts (couplers, journals, etc.) available in 1" scale from England, but I can't remember the name offhand.
Carlo

[RoughboyModelworks]

OK, finally sorted out the raised lettering. For some reason Cobalt doesn't allow you to adjust the spacing between letters when letters are set along a path. To remedy this I created a template image in Illustrator which allowed me to set the text in the correct size, font and letter spacing round the circle. After importing the template image into Cobalt, I set each letter individually as a separate object using the Illustrator template as a guide. Each letter was then extruded into a 3D object, the top face and edges chamfered to more closely represent cast-on letters and the entire set up attached to the front face of the wheel. In this way I was able to get the correct font style, size and letter spacing to better replicate the original.



Carlo... thanks for the input. I have a note somewhere in my files about the UK company producing the brass Heywood parts. Believe I contacted them last spring for some information but didn't get a response. I'll have to do some more digging, but I'm still considering producing them myself. Will largely depend on cost.

James... yes, I've also considered producing the wheels as a single casting, replicating the originals. Again it will be a matter of cost, but it's certainly worth investigating.

Paul

[Chuck Doan]

Don't forget PAP has some max size limitations. Great looking wheel!

[RoughboyModelworks]

Thanks Chuck. Yes, I'm aware of their size limitations. This wheel is just over 1" in dia. and .25" deep. Their limitations will mean I won't be able to have as many centers printed at once, probably no more than three sets of four sprued up. I may just have one set of four done the first time just to see how they come out.

Paul

[Chuck Doan]

I figured you did. I was also thinking about doing something in 1/12th.

[Carlo]

Paul -
The British Company is Talisman Castings, at http://www.talismancastings.net
The owner, Peter Coulter died recently, but the business is being carried on by Si Harris (modelearth). His contact info is on this web site too. Great 1" scale brass castings of Heywood hardware.
Carlo