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Over on the Aristo forum, there seems to be a constant discussion about the problem with maintaining quartering on steam locomotives. (I am talking sparkies here)
Since I got yet another nasty response from an Aristo employee (making a suggestion that there is a FAQ forum), I will post my Aristo opinions here.
The Aristo design differs from "traditional" drivetrain design.
One design is very analogous to a real steam loco, the power is transmitted among the drivers via the connecting rods on the drivers.
Of course in a real steam locomotive, the power from the pistons, but typically in a model, one driver axle is geared to a motor. Then the rest of the drivers get "power" from the connecting rods.
In order to do this, you need nice tight fits between the crankpins on the drivers and the connecting rods, and good synchronization between drivers on each side. You do not have to maintain "quarter" between the left and right side, but you do have to have all drivers in pretty good synchronization to transmit power.
Now, if you are building something less expensive, you find a way to have looser manufacturing tolerances, which typically saves money.
So Aristo had a very clever idea, power all axles via a modular gearbox system. Each gearbox has a female hex "socket" to drive the worm gear, and you can daisy chain them by hex driveshafts in any number you want. In most engines, the driveshafts are also brass flywheels.
Very cool. The gearboxes also pick up power and have a LOT of side to side play in the axles.
So now, you can negotiate tighter curves, because of the large amount of side to side play in every axle.
Of course, now that the connecting rods do not transmit power, they have have nice sloppy fits, saving manufacturing money, and assembly time. They also have to be quite loose to accomodate the side to side motion of all the axles.
Now, unfortunately there are downsides. To keep costs down, the drivers are not keyed to the axles. So they can slip if not well mated to the axles. Since they are a taper fit, if they were lapped to the axles a bit, they will not normally slip. But an additional problem surfaces: there is no way to adjust the gauge of the wheels. You could narrow the gauge by lapping the wheel "into" the axle a bit more, but all Aristo wheels are traditionally (as are many other manufacturers) gauged too narrow.
The only real solution is to shim the metal "half" axles where they bolt up to the plastic gear in the center.
So, it's a clever design, designed to be low cost, and allow the use in many different locos, but it also has downsides.
There are other tips on this on my site, as there are other issues of power pickup problems and simple fixes.
This post was prompted by repeated posts on the Aristo site as to why the drivers are not keyed, and why power cannot be transmitted by the side rods.
Regards, Greg
Since I got yet another nasty response from an Aristo employee (making a suggestion that there is a FAQ forum), I will post my Aristo opinions here.
The Aristo design differs from "traditional" drivetrain design.
One design is very analogous to a real steam loco, the power is transmitted among the drivers via the connecting rods on the drivers.
Of course in a real steam locomotive, the power from the pistons, but typically in a model, one driver axle is geared to a motor. Then the rest of the drivers get "power" from the connecting rods.
In order to do this, you need nice tight fits between the crankpins on the drivers and the connecting rods, and good synchronization between drivers on each side. You do not have to maintain "quarter" between the left and right side, but you do have to have all drivers in pretty good synchronization to transmit power.
Now, if you are building something less expensive, you find a way to have looser manufacturing tolerances, which typically saves money.
So Aristo had a very clever idea, power all axles via a modular gearbox system. Each gearbox has a female hex "socket" to drive the worm gear, and you can daisy chain them by hex driveshafts in any number you want. In most engines, the driveshafts are also brass flywheels.
Very cool. The gearboxes also pick up power and have a LOT of side to side play in the axles.
So now, you can negotiate tighter curves, because of the large amount of side to side play in every axle.
Of course, now that the connecting rods do not transmit power, they have have nice sloppy fits, saving manufacturing money, and assembly time. They also have to be quite loose to accomodate the side to side motion of all the axles.
Now, unfortunately there are downsides. To keep costs down, the drivers are not keyed to the axles. So they can slip if not well mated to the axles. Since they are a taper fit, if they were lapped to the axles a bit, they will not normally slip. But an additional problem surfaces: there is no way to adjust the gauge of the wheels. You could narrow the gauge by lapping the wheel "into" the axle a bit more, but all Aristo wheels are traditionally (as are many other manufacturers) gauged too narrow.
The only real solution is to shim the metal "half" axles where they bolt up to the plastic gear in the center.
So, it's a clever design, designed to be low cost, and allow the use in many different locos, but it also has downsides.
There are other tips on this on my site, as there are other issues of power pickup problems and simple fixes.
This post was prompted by repeated posts on the Aristo site as to why the drivers are not keyed, and why power cannot be transmitted by the side rods.
Regards, Greg