I have a binding problem in a Bachmann 2-8-2. I notice that the eccentric cranks are not oriented in the same way. Could this cause the binding? Do the eccentrics need to be in identical positions on both sides of the loco? If so, how is this done?
Anthony
Crank pins are quartered. Because the cylinders on a steam locomotive are double acting. That means they generate power on the out stroke and the in stroke. So the eccentric pins are also a quarter turn apart from the other side.
Your binding can be any one of these issues.
1. One or more wheel is not quartered on the axle.
2. Side rod bent or the crank pin holes are not in the same location.
3. Any one of the valve links are bent or too tight and will not pivot.
4. Cylinders and crossheads not in alignment.
5. Side rods are worn out and the crank holes are oversized or egg shaped.
Pete.
The position of the eccentric crank does not matter on an electrically powered model.
I don't know if the Bachmann 2-8-2 is this way, but their older steam engine models had stub axles on their drivers that press fit into a middle plastic axle. They were notorious for the axles being able to twist and slip out of "quarter", the relative alignment with the other axles.
It's #1 on Pete's list above, and that's the first thing I'd check especially on a Bachmann. Even a little tiny bit off will cause problems.
Set the model so one side's crank pins are all absolutely 90 degrees straight down. The other side's pins and rosd should all be perfectly level with the track. Dan
Yes, so the pins need to be at something like 6:00 O'clock one side, all in line, and 3:00 O'clock on the other side, all in line. On some models, if they are not both in line and quartered, the engine will run erratically.
Simon
Overmod The position of the eccentric crank does not matter on an electrically powered model.
I have only had modest success across forums in establishing this truism myself...but the response is generally that, if the aesthetics count, then the statement is false.
Wrench has answered correctly that the binding is likely to be bent and swiping/rubbing rod and linkages, backed out screws or pins there as well, bent piston rods or worn crosshead components and pins, worn insertion orifice for the piston rods, slight problem with quartering (this happens over time with many steamer models) where the metal rods won't stretch to accommodate the off-quarter changed pin distances (or compress),...those kinds of things. However, internally, it could be a gear problem, worn trunnions, worn bearings (driver axles or gear axles), wheel gauges,...the list goes on.
The loco is new( 6 monthes old). It has intermitant binding. The binding was there when I first ran the loco but disappeared and started again after several months. How hard is it to quarterer the loco without using NWSL quarter?
Have you inverted the loco on a foam mount of some kind, powered the tender drivers with clips and leads, and then run it to see if the binding happens that way? You can use a flashlight or an Optivisor and get overtop the drivers and running gear and see if there's something binding. If not, it's probably internal.
BTW, historically, the Bachmann steamers have needed something of a 'running-in'. I found that with a Spectrum Class J 2-8-4 (which never did run in well and I had to sell it), and a Spectrum 'Heavy Mountain' 4-8-2 which is still stiff after many hours of 'running-in'. In fact, it's the only locomotive across my 28 or so that requires a CV2 setting higher than about 15. In it's case, it's closer to 45.
Sandcounty ... How hard is it to quarter the loco without using NWSL quarter? Anthony
... How hard is it to quarter the loco without using NWSL quarter?
It's more involved than 'hard', and is quite effective if...IF...quartering really is the problem. I'm not convinced unless you can look at all the driver cranks on each side and notice that at least one of the four cranks on each side is off by more than 2 deg.
OvermodThe position of the eccentric crank does not matter on an electrically powered model.
Well, it did have an impact on a brass 10 Wheeler when the screw that held the valve gear in-place on the engineer's side of the loco, managed to work free, and when the screw and associated valve gear dropped to the ties, it flipped-over the loco.No other damage done, but I may have to drill and re-tap for a slightly larger screw to better-hold things in place.
Wayne
I have a test tract that I can watch the running gear from the side. It only binds in the forward directiont. It only bind when all wheel connecting rods are parallel to the track. I also put it on my test stand and observed the running gear in action. Same results, it binds when all wheel linkages are parallel to track. I have the shell off of the engine and will try to determine if the wheels are quartered correctly. I will also test the loco in the inverted position.
Another point: on an electrically-driven model, accurate 90-degree quartering isn't required, but getting precisely the same quarter angle on all the driver pairs is.
If you make a homemade quartering jig that is 'about' 90 degrees and use it consistently on all the driver pairs, it would eliminate binding due to inconsistent quarter.
You might want to take the rods off to check binding in the drive and chassis, then install the siderods in pairs to check binds, then the mains and cranks.