TT scale US wagons

What type of coupler?

Tillig style
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Re: TT scale US wagons

Postby ConducTTor » Sat Aug 14, 2010 11:36 am

Thanks Ben. It's a good piece of mind. I think it goes without saying that if things started breaking/decomposing a year down the line, the disappointment would have been pretty high.
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Re: TT scale US wagons

Postby ctxmf74 » Sat Aug 14, 2010 12:11 pm

scaro wrote:My concern was more that as I might be using different wheels to the Tillig ones most of you use, that I might run into some wear and tear issues down the track,A couple of the proto87 guys there noted various engineering applications where nylons like this are used in a 'metal on plastic' use and one suggested the porosity might indicate that fine graphite lubricant would be useful if needed.


Hi Ben, I've been wondering how to put wheels with HP size flanges in these trucks, let me know how your axel experiment works out. Nylon should be good for flexibility and wear. Is there really material porosity or is it just surface roughness due to the printing the part in little dots factor? ...dave
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Re: TT scale US wagons

Postby ConducTTor » Sat Aug 14, 2010 1:03 pm

Dave, there is some actual porosity. However, im sure its a matter of material thickness - i have no idea what the situation is in our case. I suppose putting a drop of water on one side and seeing if it comes out on the other will answer that question.

For HP wheels, I can make another version of the truck if needed. But I dont have any so someone would have to send me an axle (with wheels).
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Re: TT scale US wagons

Postby areibel » Sat Aug 14, 2010 2:20 pm

If wear gets to be an issue in the axle bores there are some simple fixes. I'd bet if you used some powdered graphite and burnished it into the axle holes it would reduce the friction.
Or a litle more complex method- John Fisher used to make white metal castings for side frames, he had a small brass bushing to mount the axles in to. You had a dimple in the casting, you just drilles a 1/16 inch hole and pressed the bushing in- it would work on the Shapeways trucks too, might need a tiny dab of ACC to hold the bushings in. I'm not sure where he got the bushings from, but they weren't that expensive- Richard, do you recall where he found them?
If you got really fancy, you could design the truck with the recess to take the bushing, that would probably be a truck that would use a stock HP axle. I think the HP axles were just 3/32 rod with blunt ends.
I can send you some, ConducTTor for experimental purposes.
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Re: TT scale US wagons

Postby richardedmonds » Sat Aug 14, 2010 2:37 pm

Al unfortunately I didn't get to know where John got those bushes. There were none in the stuff he left me and I don't have any to compare them with. They must be old 3mm society stuff as that was more or less Johns shopping mall. I will ask Matt Coleman as he is a mind of all of John's ideas and parts.
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Re: TT scale US wagons

Postby ConducTTor » Sat Aug 14, 2010 5:59 pm

@Al - the brass bushings you mention did cross my mind. However, I couldn't find them anywhere so I didn't design for them.

If you know the exact dimensions of the HP axles, just let me know and I can do without the physical part. But you gotta be as exact as possible.
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Re: TT scale US wagons

Postby areibel » Sat Aug 14, 2010 10:12 pm

OK, The HP axles are .046" in diameter and range from .721 to .723 long ( I checked about a dozen different ones) so they're 3/64" stock, not 3/32.
The Gold Coast axles are about .730 long with the needle points. I put a truck together with a pair of the HP's and they're not too far off already, just a little stiff. If I can find my little metric bits I'll try drilling the pockets a little deeperto see how they ride.
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Re: TT scale US wagons

Postby ConducTTor » Sat Aug 14, 2010 11:05 pm

areibel wrote:OK, The HP axles are .046" in diameter and range from .721 to .723 long ( I checked about a dozen different ones) so they're 3/64" stock, not 3/32.
The Gold Coast axles are about .730 long with the needle points. I put a truck together with a pair of the HP's and they're not too far off already, just a little stiff. If I can find my little metric bits I'll try drilling the pockets a little deeperto see how they ride.


Cool. It sounds like if the pockets are blunt instead of pointed it would work fine?
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Re: TT scale US wagons

Postby scaro » Sun Aug 15, 2010 2:30 am

Does anyone know if the HP wheels are still being manufactured? Certainly Elmer at PVM uses them in his kits but not sure if it's old stock or if they are still made. They are rather nice, by any standard.

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Re: TT scale US wagons

Postby Bill Dixon » Sun Aug 15, 2010 4:01 am

I started working on my model this evening.

First I weighed it. It is very light, about a third of an ounce or 10.7g for those of you who can handle metric.
I am going to add a sheet lead floor to increase the weight.
I am not sure how well the trucks will pivot under the body of the car. It may need a spacer washer to raise the body up a bit so it will handle typical curves.

First step wash the casting and then let dry. I then sprayed Tamiya grey primer on the casting an waited for it to dry.

Boy does it look and feel rough.

So I started working on smoothing it out. I used 600 grit sandpaper and made a sanding stick to get between the ribs. Just a piece of wood with an angled end and a narrow strip of sandpaper wrapped around the end. My stick is about an 1/8" wide but you could go up to 1/4" wide. With this I was able to smooth most of the space between the ribs. I used a fiberglass eraser to clean around the rivets and the grab irons. I did not worry about the under body or inside the shell. I used the sandpaper to smooth out the top of the sides, the ends and the ribs.

I gave it another coat of primer and sanded the sides again. The finish is now much better.

Tomorrow I will spray it with Scalecoat Engine Black and let that dry most of the day.

I still need decals. Can anybody point me to some pictures so I can figure out what the lettering should be?

I am not going to worry too much about smoothing the trucks. Paint and weathering should hide any problems there.

Some thoughts about future models.
- I do not know if it is worth while putting the grab irons on the casting. It might be easier to leave drill holes and let the modeler add them if they wish.
- Talking with another modeler who has made an HO scale passenger car, the process does not make totally smooth curves. Expect to do a bit of sanding to smooth the curves out.

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