7/8ths Scale Hudson Rugga Skip started or remake

[78ths]

Hi all
I had posted my resin skips some time ago. They were made in molds made about 4 years ago. Recently I have switched from resin casting to tin alloys and love the metal a lot more. Less waste and it has that hard to ignore hefty feel to it especially in 7/8ths scale or 1:13.7 .

I redesigning the skips (which are to go behind a Fordson Rail Tractor also in 7/8ths - that is another post I will start later) the decision was made to go more finescale and a good 20-30 hours was spent going over drawings and hundreds of photographs or current museum pieces and in use relics. Matching photo to drawing and trying to figure out what was creative license on the railroads part and what was stock factory is a challenge at times. Non the less my first step was to do up cad files, to aid in both the build and 3D printed parts.

Here are 3D renderings of the parts that were sent off to be printed. They just arrived back today and I will post an update once the molds are done and the first parts are cast in tin.  The only tricky part re the mold is the frame itself. The remaining parts are simple two part molds.

Software for 3D work is all done in Viacad as the files are interchangeable between the Mac and PC and I have all Mac's (Apple) in my office and all PC's in the workshop.

The axle boxes have the large circular cutouts to hold the sealed stainless bearings. They make a big difference in how the skips run.

[JohnP]

I assume you will be using a rubber mold. Will the bearing recesses be difficult to fill and pull?

This whole shebang will be quite a show when it is running.

John

[78ths]

I really like the smooth-on high temperature rubber. If my design was done properly the parts will pull without a hitch. If not the mold will tear. The high heat rubber has a much lower tensile strength compared to the mold max or platinum cured line. The nice feature of the high heat line is being able to pour the metal at 600 degrees which tin needs to really flow properly.  Casting the parts in resin would be no issue at all (I cast all my resin in a pressure pot and vacuum all the rubber before pouring and after pouring.)  I am also trying to get a home made spin caster complete - I just need more hours in the day for all the tasks at hand. Have to throw in making a living too. 

[78ths]

First attempt at making a mold for the skip frame was a total failure and master destroyed in process.  Oh well its all part of the learning curve - you think once you have done 50 or so molds you would learn to think of every possible cause of failure. Back to the drawing board - will post an update once the mold is done. Looks like it will be a three part silicone mold.  Just threw a 40$ part and 50$ worth of silicone in the bin. 

[finescalerr]

That must have seemed rewarding. Did you propel everything at high velocity against the nearest wall? I would have. -- Russ

[78ths]

Hi Russ
The last time I did that I hit another model that was on the shelf on the wall. I did use excessive force when the whole lot hit the bin. I have since salvage the rubber to use as filler in the next mold.
I keep repeating the mantra "a hobby is stressfree and FUN" so far not working. 

cheers Ferd

[JohnP]

The learning curve still continues in my bridge part mold making. The snapshot here is a collection of RTV molds that failed sooner or later. Soft mold, hard mold, blue mold green mold; lots of trials in that heap.  They're from just today to a few years ago. I have more in old mold boxes.

So keep going Ferd, Scheiß happens.

John


Why the heck am I saving those anyway? 

[78ths]

Here is the frame complete - just cast the rest of the skip (excluding tub) and will clean up one set and prime tonight.
I am happy with the frame and am really looking forward to coming up with variations for the deck ie. flatcar, passenger etc..
Next will be to do a master for the tub and cast it in metal too.

The frame has only been primed so far.
cheers Ferd

[Chuck Doan]

Congratulations!

[78ths]

Thanks
Here are some test fits of the remaining castings.  It was hard finding bearings small enough to fit in the axle boxes. The bearings are almost scale. I will have to throw the wheel sets in the lathe and shave off a few thou so they fit in the axles - small price to pay for a better look.

Top image show underside of the skip.

[W.P. Rayner]

Looking good Ferd... I like the setup for the photo as well: jackstands, mallet and empty coffee cup... nicely done.

If you don't mind my asking, what are the dimensions of those bearings and where did you find them? I'm planning on making small sintered oil-impregnated bronze bearings for my brke van and other rolling stock. They are not going to see a great deal of operation, rolling static models mostly. But for Katie, I'd like to take it up a notch.

Paul

[78ths]

Hi Paul
I brought the bearings in from China directly. They are MR63ZZ   from  http://en.lily-bearing.com/ the specs are
6mm outer 2.5mm thick and 3mm inner bore.

cheers Ferd

Funny how photographs show so much more detail and areas that need to be worked on. Viewing models without the reading glasses they look so much better.

[W.P. Rayner]

Thanks for the info Ferd... much appreciated.

Paul

[fspg2]

Hello,

I got my axle bearings here: http://www.modellbauershop.de/assets/s2dmain.html?http://www.modellbauershop.de/index2.html

for example: 6mm outer 2.5mm thick and 3mm inner bore 10 peaces 6,90 € .
I don´t know what´s the price you paid.

Frithjof

[78ths]

Hi shipping included 200$ for 250 shipping included.  So ~ $0.80 each.  or 5.7 euros for 10 - shipping included.