Double heading H0 locomotives with similar speed characteristics

Hello,
I timed my locomotives around my small layout with and without cars attached. Using this information I put two locomotives (with similar
pulling characteristics) together to pull one long train of cars around. Is this sound practice or should I be concerned about damaging either locomotive prematurely. One is a Kato RS3, the other is an Atlas GP-38.
Also I have a new Model Power FPA(?) locomotive that runs reasonably well (*) but generates a lot of crackling noises in my power supply when I run it at any speed. (Computer speakers will also pick up this elec. noise.) It left the power supply unaffected when I first bought it, but more recently (with use), it has started this problem.
(*) - Actually this locomotive will derail at turnouts if I run it at top speed, while other more expensive locomotives sail around the curves and turnouts fine. I know. I get what I pay for.
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scgtking wrote:

It's OK to do this, esp. since you matched the locos as closely as possible.

This is a sign of sparking, probably on the commutator (in the motor), or else on the wheels and wheel pickups. Usual reason is lack of lubrication, dirt may also cause this. Lubricate the engine, using small amounts of oil applied with a toothpick or fine wire. Examine the loco closely and remove any fluff and stuff between the wheels and the side frames, etc. Then apply a small amount of oil to the wheel bearings and pickups where they contact the wheels. Clean the wheel. Remove the body, and examine the motor. If it's an open frame motor, you will see the commutator and brushes at one end. Apply a very small amount of contact cleaner/lubricant to the commutator.

True. ;-)
HTH wolf k.
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If these are DCC locos and if you are using DCC, you can program a MU set and configure things to take into account the power characteristics of the two locos and any decent DCC system will 'balance' the load on the two locos properly. If the two locos are really close, they should work reasonably well, even with a straight DC setup.

Probably just dirty wheels, pickups, and/or brushes.

Well there is that too...

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Maybe try slot cars if you're into speed ( sorry, someone had to say it )
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One of the things that I've noticed when double heading locos is that light locos don't like to do this unless they are very closely matched. On the other hand, heavy locos will tend to run together even if they have some fairly different speeds. A case in point. I had a Tyco GP-20 and a remotored Athearn F7. Speed differences were on the order of 2:1! When the GP got weighted a bit (remember the loco had rubber tires on the one truck) it would tend to pull the also weighted F7 along a bit at a speed slightly higher than the F7 would want to go and when the two got a good load the F7 would then start pulling also. It wouldn't matter which loco was in the front other than how the pulling transfer of power would happen. The secret here is that the two locos had enough weight in them that they would slow down a lot before starting to slip and that would keep them from sliding along. At the point where the fast loco would slow down due to the load, it would tend to get additional pull from the slower lead loco with a bit of slack running in and out very slightly with the load with the slower loco. This even works to a slight degree (with not as much difference in speed between the locos) as a rear end helper on a grade. When on a grade tho, you do need to have enough of a load that the lead loco basically barely pulls the train. On a long train, you can watch the pushing and pullling division run back and forth along the locos as slack runs in and out. Overpowering the train can put it on the ground tho, so be careful when doing this. Also good trainhandling needs to be done as rapid changes in train speed and the different inertia characteristics of the two different locos can also put the train on the ground.
-- Bob May
rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net
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I've found that if two locos have a noticable speed differential it works a lot better to entrain the quicker one ahead of the slower one, as it keeps their couplers under constant tension.
If you do it the other way around, the couplers are always being pushed open, and when you get to a grade you may discover that the train stalls because the lead engine has uncoupled itself and is walking away from the consist, while the trailing engine hasn't got enough power to pull the train up the grade by itself. (Guess how I discovered this.)
Speed diferentials are even *more* crucial if you're using mid-train or rear-end helpers: a slower engine in back will tend to straighten the train out like a bowstring and pull the consist off the track to the inside of the curve, while a significantly quicker engine in back will tend to push the cars ahead of it off the tracks to the *outside* of the curve. Both of these situations can be messy in the wrong location...
http://www.flickr.com/photos/33885727@N03/3356978423/sizes/o /
...such as in the middle of a 3' high curved trestle.
But the worst derailment I've ever had that involved multiple units and mid-train helpers was caused when one of our more innattentive club members failed to notice that my train had already taken the block he was entering from the far side, and reversed the polarity to suit himself. This meant that my lead units suddenly reversed direction, while the mid-train helpers -which were in another block altogether- continued pushing.
Took about ten minutes to clear away the carnage.
~Pete
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I've always used Kadee couplers - my first layout was a switching yard and X2F couplers were horrible for uncoupling at random points. I've never really seen uncoupling of that variety from Kadee couplers but then again, I also prefer to run my locos slow. I do agree that the fast loco in the lead does keep the slack stetched tho.
-- Bob May
rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net
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Me too. In fact, I was using Kadees before they were magnetic; back when they still used diamond-shaped uncoupling ramps. Had to convert everything over when the magnetic variety came along, and I was *not* happy about it at the time.

Me too.
But if I hadn't had it happen repeatedly I wouldn't have formed the habit of putting the quicker loco in front.
~Pete
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Spur gear drive locos will cope better with mismatched speeds than will worm drive locos, because they can be pushed or pulled under power without the gears locking up. A worm drive and a spur gear drive loco will generally work reasonably well together upto about a 1:2 speed range difference. Two worm drive locos are ok up to about 1:1.25 speed range difference. (which isn't much at all)
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Tyco fitted metal wheelsets to their tram/streetcar. (might also be in their tender drive steam loco?)Those will drop straight into their Diesel-electrics. You can also fit a second motor bogie into most of their Diesels. The Archillies heel(s) of their mechanisim is the armature gear made of soft metal, which wears out quickly and also the copper plated PC board commutator which oxidises and then runs very badly until the surface gets repolished by the brushes.
Greg.P. NZ
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GP20 has plastic worm gearsets. The solution to the problem of getting two locos together is not to overpower them but rather get their weight up to the point where they only spin their driving wheels slowly when stalled out. A loco that starts slipping when the speed is 90% of full speed won't work with another loco as well as it would if the speed of the drivers is 50% when stalled. You don't get the wide range of speed with an overpowered loco. You do get a lot more traction tho when you add in the weight to get the range of speed!!!
-- Bob May
rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net
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Just for clarification, is the noise coming from the locomotive itself OR the power supply? I first read it as the power supply yet I see that two people responded as if it was the locomotive making the noise. I just wanted to be clear...
dlm
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Dan,
The crackling noise was definitely coming from the power supply. I didn't run it very long for that reason. When I first got those locomotives, the only crackling I heard was from computer speakers that were on at the time.
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On 6/9/2009 9:49 AM scgtking spake thus:

You've got a power supply problem there.
Please don't clip all previous quotes out of your posts.
--
Found--the gene that causes belief in genetic determinism

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Check the couplers to make sure that they are not conducting to one side of the rails. Kadee metal coouplers on a metal frame do this well and provide intermittent shorts that gradually get worse as the coating on the couplers gets abraded off by the sparks between the couplers.
-- Bob May
rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net
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