super detail "train set" on a super budget?

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Bufferstop
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Re: super detail "train set" on a super budget?

Postby Bufferstop » Tue Aug 07, 2018 11:52 pm

I've had a look at one of the newer 0-4-0 chassies from China. The worm and gear are the same dimensions but the tooth profile is quite different. The biggest improvement is probably in the reduction of friction allowing the motor to turn at a lower voltage.
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Mountain
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Re: super detail "train set" on a super budget?

Postby Mountain » Wed Aug 08, 2018 1:59 pm

The reduction of friction was achieved in two ways. One is by usingvery thin and springy wheel contacts instead of the heavy duty ones they once had. The other difference is that the motor has a sticky pad to prevent movement when it is in place on the chassis and motor retaining block. The metal spring wire retainer remains.
Do you think the gearing itself is different from before and hence the lower top speed?
I've noticed that the new pickups are a bit more difficult to take out and put back in then they used to be. One now could do with three or four tiny hands where with the older pickups one could almost put them in single handed.
The thing I love the most about these chassis is the simplicity of design. Due to this simplicity and that modifications over the years have been made in such a way that they fit the original design mean that one can rebuild using parts from several different locos of this type. As long as the gears mash together (The worm and cog are compatible) all should be fine. One can even mix and match the later Triang cast metal chassis as they share the same axle spacing and con rods, and the later Triang motors were carried on into the earlier Hornby 0-4-0 shunters. (Earlier Triang chassis used the beefier X03/X04 type motors where the newer motors had a cradle to fit the old Triang chassis designed for the X03/X04).

The China made chassis have had two modifications depending on how modern they are. The earlier years of Chinese production were identical to the Uk Margate ones except they had blackened wheels. The blackened wheels did seem to be slightly more refined. The later ones as mentioned earlier have much thinner pickups and a slower top speed running. The motor is turned the other way up and now has wires to connect it between the pickups and the motor.

Out of all the years they've made them, the only design that is less desireable is the brief few years where they made them with square axles and they skimped on the chroma plating of the wheels. This was about 1977 or 1976 where they made a budget version of the design aimed at kiddies with limited pocket money. (The loco was cheaper then the standard 0-4-0 with the same chassis design).
The only main differences of all the different bodies using this chassis is some have piston rods and the chassis is designed to take them with pistons, and others dont and the chassis doesn't have the pistonsad it is used on models without piston rods. An interesting version using the same 0-4-0 chassis is the class 06. With this loco, the chassis is turned backwards and (Not sure about newer versions) the pistons of the chassis are hidden under the body.
The versions that have piston rods have extended crank pins to take them and the con rorods just with the rearmost set of wheels. Those which only have con rods have standard crank pins.
Various attempts by modellers to improve these chassis over the years have been noticed. Some have changed the piston rods to mount them in slide frames which improves the look of the model. Others have addressed the versions with the high top speed with the most popular way being to convert to a double reduction gearing.
I am planning on modifying some of mine to change the look of the wheels. While I dont really mind the locos top speed as long as it runs well, I do like the older Triang metal chassis. However, to use them it takes a fair few days of work in trying to cut and drill/mill mazak chassis weights. Also if one changed the wheels one needs to make pickups as Triang wheels are designed to pick up on one side (The other side picks up live between the axle and the metal chassis). The newer wheels need both sides to have pick ups.
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Bufferstop
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Re: super detail "train set" on a super budget?

Postby Bufferstop » Wed Aug 08, 2018 4:03 pm

Do you think the gearing itself is different from before and hence the lower top speed?

If it is it's not by much. I think the motor has a different torque range and runs out of "puff" sooner, it definitely pulls better, maybe a better magnet. Stronger mag field means higher back emf, means lower speed and more grunt.
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Mountain
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Re: super detail "train set" on a super budget?

Postby Mountain » Wed Aug 08, 2018 5:46 pm

It could be that. But doesn't a stronger magnet mean that the smoothness of the motor is effected? I was assuming that there was some sort of resistance to limit the top speed of the motor? It is interesting.
Another thing which is interesting is about worms. In my thinking, a double worm gives a lower gearing then a single wound worm or is there no difference? I dont think there is a difference between the gearing on a fine toothed worm compared to a coarse toothed worm as it has more to do with the sizes of the worm and cog (As in diameter). But a doubly wound worm.... I'm trying to think how things work. :lol:
I know about cog to cog gearing and used to know how to work it out. (We used to cover things like this in college, and I also need to know about gear inches in the bicycle trade (E.g. gear teeth on front and back cogs and the relationship between them and the wheel size etc).. But worms where it spins a different direction... My thinking is to treat it like a cog but when a double wound worm comes into the equation it all gets complicated! :D )
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Re: super detail "train set" on a super budget?

Postby Pete » Wed Aug 08, 2018 9:08 pm

But a doubly wound worm


Not sure what you mean by doubly wound, do you mean the equivalent of an involute form to maintain contact, transmit greater loads and reduce backlash?

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Mountain
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Re: super detail "train set" on a super budget?

Postby Mountain » Wed Aug 08, 2018 9:37 pm

Eh? :lol: Sorry. You've lost me. I mean... A standard worm has a thread that starts from a single point and screws its way down to the other end. The twin type has two "threads" starting at the top and they both wind their way to the other end. (I'm trying my best to describe the mental picture into words!)
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Bufferstop
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Re: super detail "train set" on a super budget?

Postby Bufferstop » Wed Aug 08, 2018 10:23 pm

Two start worm is the proper description. This one is definitely not two start, it has a very open profile. Without breaking the motor open it's difficult to decide how it's been constructed. Providing you don't want it to creep around it will perform ok on a DC controller. Doubtless on DCC you could tailor the start voltage and top speed to get slower running.
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Emettman
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Re: super detail "train set" on a super budget?

Postby Emettman » Wed Aug 08, 2018 11:32 pm

A double start worm produces a *faster* final drive than a single one.(everything else being equal)

While a single-start worm advances its associated gear wheel one tooth per revolution, a double-start worm advances the gear two teeth per revolution.

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