# Quartering locomotive wheels



## Chiefmcfuz

Is there any tutorials or videos on quartering O Gauge locomotive wheels?


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## teledoc

Chief, Is there a specific question about quartering the wheels, you need answered. Quartering only comes into play, when dealing with Steam locos, that involves linkage.


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## mesenteria

Quartering is important on the real steam locomotive, but not so much on the models. What is important is getting all the crank pins in the same position on either side so that the rods don't bind as the engine moves. A single crank just a fraction of a mm out of position imparts a lot more wear and stress on the drive mechanism. Plus, it ovalizes the hole in the rod and it ovalizes the crank pin itself over time.

The other matter is why one or more wheels have slipped on their axles, thus moving their cranks out of true with the others. Getting them back into line might not be much of a challenge as much as getting them to stay aligned and immobile on their shafts. If the inner wheel hub is not cracked, and there are no splines for alignment on the axle, you'll have to pull one or more wheels, rough up the axle so that an adhesive will have some 'tooth' to adhere to, and then use an epoxy or CA. It's critical to ensure the crank will end up in the correct position, and you do that by placing the rod back on to ensure the crank pins are aligned. By the time the epoxy dries, you'll not be able to correct alignment.


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## Chiefmcfuz

Primarily I am asking because I am replacing wheels on prewar locomotives and I am interested in making sure that I am doing everything as correctly as possible


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## gunrunnerjohn

mesenteria said:


> Quartering is important on the real steam locomotive, but not so much on the models. What is important is getting all the crank pins in the same position on either side so that the rods don't bind as the engine moves.


Well, not really true on most O-gauge locomotives. The rods actually driven the wheels, and if they're out of quarter, you'll run into problems. It's obviously not quite as critical as with a real steamer, but it's fairly critical, especially with x-8-x or x-10-x models.


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## Chiefmcfuz

How do you do it?


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## mesenteria

gunrunnerjohn said:


> Well, not really true on most O-gauge locomotives. The rods actually driven the wheels, and if they're out of quarter, you'll run into problems. It's obviously not quite as critical as with a real steamer, but it's fairly critical, especially with x-8-x or x-10-x models.


We're saying the same thing: the pins must be in alignment so that the rod will fit, and then drive all drivers. But it doesn't follow that the cranks must be quartered. Quartering means the cranks are set at precisely 90 deg apart on either side of the locomotive, normally with all the right side cranks showing at bottom dead center while all the crank pins on the left side of the frame are in the full forward position (meaning the piston is as far forward in its cylinder as it can go).

This is important on the prototype because one of the two valves must have a an inlet port partially uncovered so that steam can flow past the valve and into the cylinder, forcing the piston to move. On our models, the valve gear doesn't really do anything, and certainly moves no valve because our models don't have valves, and don't need steam to move them. They only need electricity and gearing. When the can motor turns, the gears turn, and all the cranks turn, making the rods churn. But you could have all the cranks at bottom dead center, both sides, and the motor and gearing would still make the model move normally, even in O scale.

So really, in our hobby, when we say we want to quarter the wheels, what we really want to do is to ensure all the pins on one side line up and that we can place the rod easily and fully over all the pins. If one crank doesn't line up, we can't place the rod over them. In order to make the model look realistic, in fidelity to the prototype, we do quarter the cranks and fit the valve gear commensurately. It's for looks, and to ensure the cranks all line up, not so that the locomotive can move.


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## Chiefmcfuz

Ok so the drive side has to be 90 degrees off of the non drive side but the wheels on the same side must be parallel?


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## highvoltage

Chiefmcfuz said:


> How do you do it?


On one side of the train, make sure the balance weights are all pointing the same direction (let's just say in the 6 o'clock position). On the other side of the train make sure the balance weights are 90 degrees off (say 3 o'clock or 9 o'clock). Either 1/4 turn ahead or behind might be specific to certain types of locomotives, someone with more knowledge than I should chime in.


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## Chiefmcfuz

highvoltage said:


> On one side of the train, make sure the balance weights are all pointing the same direction (let's just say in the 6 o'clock position). On the other side of the train make sure the balance weights are 90 degrees off (say 3 o'clock or 9 o'clock). Either 1/4 turn ahead or behind might be specific to certain types of locomotives, someone with more knowledge than I should chime in.


Great explanation. Thanks so much.


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## gunrunnerjohn

mesenteria said:


> So really, in our hobby, when we say we want to quarter the wheels, what we really want to do is to ensure all the pins on one side line up and that we can place the rod easily and fully over all the pins. If one crank doesn't line up, we can't place the rod over them. In order to make the model look realistic, in fidelity to the prototype, we do quarter the cranks and fit the valve gear commensurately. It's for looks, and to ensure the cranks all line up, not so that the locomotive can move.


Your explanation was fine until you got to the last paragraph here. If you simply put the wheels on the opposite side 180 degrees out from the other side, even though the rods don't bind, the locomotive will not run properly. Try it, I've seen it.

What is correct is precise quartering is not necessary, the wheels could be 100 or 110 degrees offset from side to side and the locomotive should still run. Virtually all the modern O-gauge locomotives only drive one set of drivers with the gearing, the rest are driven through the rods from the driven wheels.


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## mesenteria

What could stop it from running? The rods are all simply pinned and move because their cranks move, the cranks move because the drivers all move, and the drivers all move because they are linked to the one geared axle, regardless of scale, by the side rods. 

If you were to remove the worm gear from the motor shaft and just push the locomotive along the tracks, the valve gear would move just as it did with the worm engaged in the first gear atop the tower. Backwards and forwards, reliably. So it is the gear that makes the valve gear churn and the crosshead reciprocate. There's no piston with backpressure, no steam admission via valves, and there's no timing, dwell, and lap to worry about. There's nothing restricting the action of the various links, levers, and rods. So, regardless of whether or not they are quartered, the drive mechanism slaved to the can motor can make the rods and valve gear on each side look normal as it spins. Even 180 degrees offset.

Look at it this way; suppose we were to remove all pins, levers, links, and rods on one side of the steamer. Would it still run? Of course it would. If we were to arrange the same links, levers, and rods 180 deg from their original position, that is with the quartering reversed, would the motor still be able to turn everything and make it look natural viewed from either side? Of course it would. And it would work at 120 degrees, 140 degrees, 66 degrees, and every other degree because there is no valve timing to consider. Just a gear tower driving it all.


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## gunrunnerjohn

When it's close to or at 180 degrees differential is where the issue arises. At slow speeds, like when starting up, as one side's rods bottom out fully extended, the other side's rods are directly aligned with the axle. So, you're pushing directly on the wheel in line with the axle, and there's uncertainty which way the small amount of slop will take it. If it goes in reverse, the wheels lock up. Been there, done that. I don't know how the guy did it, but I got one for repair in that state.


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## Nathan3350

*Don't you need the tool?*

Ok, I haven't been into this hobby in 25 years, so I'm rusty, but don't you need a quartering tool to do this? I just picked up a big boy in pieces from a guy who was trying to fix it and gave up. With the locomotive he gave me this little tool that saddles the driver and has a wedge in it (a picture really is worth a 1000 words here...). Anyway, it seems to me that if you arent dead nuts on that 90° center, they could bind up.

(I'm HO scale so accurately quartering is probably more critical with my little guys than O, but this isn't something you can just "eyeball" right??)


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