3/4" Scale Box Cars

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Steve Bratina
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Location: Cambridge Ontario

3/4" Scale Box Cars

Post by Steve Bratina » Wed Jul 22, 2015 6:55 pm

Here is a project that I have been working on between locomotive projects. I want to build at least 20 box cars for a 30 car train I have planned. I had 4 box cars built originally but this new series has better detail and I have all the parts made and ready to go.
I had alot of trouble getting wheels CNC'd and I don't want to stand by the lathe for hours on end turning up wheels, so for this project, I am trying something new. Casting plastic in rubber molds. The car you see here is the first of the prototype and is under test right now. The ends of the car, the doors, the running boards, the center frame and coupler pockets, the truck bolster, journal boxes and wheels are all made out of plastic. Patterns were used to make the rubber molds and two types of plastic were used. The wheels, bolsters and journal boxes are Smooth Cast Onyx Slow and the rest of the parts are Smooth Cast 305. I went to some private classes to learn about moulds and pouring plastic and what type of plastics to try for my needs. So far I am quite pleased with the end results and hopefully the car will stand up to the use. Not including the cost of the mould rubber, the price for all the cast parts works out to about $50.00 per car.
The side frames were laser cut at a local shop and cost $4.00 per side. The couplers are 1:20 G scale couplers. They are slightly undersized but you cant beat the price. They are metal and open too. I tried to get some decals cut at the sign shop but they were too busy so I bought some letters at the hobby shop and lettered it for a famous Live Steam Line located in the far reaches of the country. I hope the President of that line doesn't mind!
Once the steaming season is done, I will try to do a blurb on the builders log. For now, here are some pictures of the finished car.
If you go on the Smooth On web site, they have a lot of info on their product that may inspire you to try a car or two.
Last edited by Steve Bratina on Fri Jul 24, 2015 6:33 pm, edited 1 time in total.

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Re: 3/4" Scale Box Cars

Post by FLSTEAM » Wed Jul 22, 2015 7:17 pm

Nice, I would like to try the same thing in 2 1/2" scale. BTW some what fewer than 30 in fact a whole lot fewer. More like one or two. :o)

John B.
Shay drawings and castings

Brian Tusin
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Re: 3/4" Scale Box Cars

Post by Brian Tusin » Wed Jul 22, 2015 8:40 pm

That looks great Steve!

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Benjamin Maggi
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Re: 3/4" Scale Box Cars

Post by Benjamin Maggi » Thu Jul 23, 2015 7:26 am

A neat idea.

Regarding couplers, did you do any stress tests to see if the G-scale couplers would hold up to the weight of 30 "larger than g scale" boxcars?
"One cannot learn to swim without getting his feet wet." - Benjamin Maggi
- Building: 7.25" gauge "Sweet Pea" named "Catherine"

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Re: 3/4" Scale Box Cars

Post by GooseOrBust » Thu Jul 23, 2015 8:11 am

Please keep us posted.

I'm interested in how the wheels and bearing blocks hold up.

I would think the entire train would be very quiet!


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Re: 3/4" Scale Box Cars

Post by Pontiacguy1 » Thu Jul 23, 2015 8:26 am

For a non-riding car in that scale/gauge, I think everything will work out fine. If the couplers don't hold up, well, it won't be too terrible to have to replace those.

Are the wheels cast individually and then pressed onto an axle? Surely they are left as-cast. How do your journal boxes attach to the cut out side frames, and what are the side frames made from? Do you have to do much cleanup to the plastic parts?

Nice way to use some mass-production techniques to produce a bunch of cars. You might consider making some of these parts available to others if it all test out good.

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Re: 3/4" Scale Box Cars

Post by WJH » Thu Jul 23, 2015 4:06 pm

Smooth On makes some nice stuff, played around with rubber moulds and pouring plastics in the past. Always had issues with air bubbles, needed a vacuum chamber for the plastic to set in.
You may want to stress test one or two cars to see how it holds up. Better than 30 all dying at same time, if it doesn't work out.
Yes, I am interested too in the long term results!

Steve Bratina
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Re: 3/4" Scale Box Cars

Post by Steve Bratina » Thu Jul 23, 2015 6:28 pm

The car only weighs 4 lbs. The bearings are nothing more than the side frame material itself. The axles are 1/4" drill rod cut to length and the wheels are cast ready to use. They are placed in a cup like holder in the lathe ( can't think of the name of the thing ) and drilled 4 thou under. The axle is pressed into the wheel and is gauged using a block which gives a fixed dimension from the outside face of the wheel to the end of the axle. With the amount of use a car gets and the weight of the car, I have no worries at this time that the couplers or wheels will hold up. If a wheel or set ever do wear badly, the cost of the wheel is peanuts and the truck comes apart quite easily to replace the wheel. Between the end of the axle and the back of the dummy journal box is a round felt pad that is oiled. There is also a small oil groove dremelled in to allow occasional oiling. The drag on the car is nil as she rolls like a rollerskate so the coupler load is quite low.
As for selling parts, send 4 box tops from any Mercer product and 25 cents to....... just kidding!
Will keep you posted.

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Re: 3/4" Scale Box Cars

Post by gwrdriver » Fri Jul 24, 2015 9:53 am

About 50 years ago a fellow name William J (Bill) Clouser began experimenting with rubber molds and cast epoxy and eventually succeeded in turning out absolutely astounding freight car bodies in O-scale. Later he moved on to producing O-scale traction/interurban car bodies with the same spectacular results. He had several articles in Model Railroader over the years but I don't know if his process was ever fully written up. One thing I remembered, aside from the perfect masters he made, were mentions of his struggle to eliminate bubbles which he eventually did. I could find hardly anything about him on the Web beyond a brief mention.
Nashville TN

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Re: 3/4" Scale Box Cars

Post by tsph6500 » Fri Jul 24, 2015 10:11 am

Steve Bratina wrote:I tried to get some decals cut at the sign shop but they were too busy so I bought some letters at the hobby shop and lettered it for a famous Live Steam Line located in the far reaches of the country. I hope the President of that line doesn't mind!
I vaguely resemble that remark. Nice car… I noticed the same number on my house when I got the morning newspaper. :)
Best regards,
Jim Leggett

Montreal Live Steamers

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Bill Yoder
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Re: 3/4" Scale Box Cars

Post by Bill Yoder » Fri Jul 24, 2015 1:28 pm

Dear Steve!
What a fantastic project! The usual prices for metal parts are now high enough to scare 90% of the candidates away from the hobby. I too have been dreaming of plastic cars without riders and hope to have at least four passenger cars behind my 4-4-0: an express reefer, an RPO/baggage car and two passenger cars. We'll have radio control on the American and can then watch a Canadian National local from about 1930 roll by.

Please do keep us posted. Super-sized HO with live steam! :D

Bill Yoder

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Re: 3/4" Scale Box Cars

Post by cp4449 » Fri Jul 24, 2015 4:13 pm

Fantastic. I too would like to know how well they hold up.
Could we try this in one inch?
C.P. Mahony
Former 1" Foreman
Los Angeles Live Steamers

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