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 Posted - June 28 2009 : 09:25:26 AM
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I have an HO F7A [I think circa 1973 onwards as it has 'brass' flywheels & the connector clip set up, but also a can motor & the super weight]
I have been working on hard wiring to improve the patchy electrical pick up.
It is fairly noisy & I put some Teflon grease into the couplings systems.
I noticed that shortly after that when it is run in reverse it starts off then after about 2 seconds it slips to approx. half speed with a vague 'fizzing' sound in the back end.
I am trying to figure out if its the rear truck gear box or if something is slipping on a shaft in the coupling set up?
Anyone else had this??
Tanked
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Posted - June 28 2009 : 11:16:14 AM
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If it is "fizzing", maybe it is causing a short circuit at certain points where the wheels touch the electrical pick-ups, or maybe the wheels themselves are dirty.
If you see sparks coming from the wheels they are probably dirty, and if the headlight flickers you've got a pick-up problem.
I'm sure somebody else probably knows what this sound means though, and I could be wrong.  
    
- Matt -
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Posted - June 28 2009 : 1:37:04 PM
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quote:If it is "fizzing", maybe it is causing a short circuit at certain points where the wheels touch the electrical pick-ups, or maybe the wheels themselves are dirty.
If you see sparks coming from the wheels they are probably dirty, and if the headlight flickers you've got a pick-up problem.
I'm sure somebody else probably knows what this sound means though, and I could be wrong.
Originally posted by MM 1498-June 28 2009: 11:16:14 AM
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I've had a closer look at it & don't think its sparking/electrical.
The sound is more like a 'zzzzzzzzzzzzzzzz', plastic on plastic or metal rotational rubbing or slipping.
I noticed that when I have run backwards & its making the sound, & I stop, then go forwards - it makes the sound for about two seconds as the drive train spins & the loco moves forwards, then there is a 'click' & the 'zzzzz' disappears & the drive train sounds 'normal' again.
Thanks for suggestions.
Tanked.
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Posted - June 28 2009 : 1:47:25 PM
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Perhaps the motor is not fastened to the frame tightly enough, so when the motor spins in reverse, it moves to the side slightly, making the flywheel rub against the frame or shell.
- Matt -
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Posted - June 28 2009 : 4:27:44 PM
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quote:Perhaps the motor is not fastened to the frame tightly enough, so when the motor spins in reverse, it moves to the side slightly, making the flywheel rub against the frame or shell.
Originally posted by MM 1498-June 28 2009: 1:47:25 PM
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Rock solid motor mounting.
After further ear to the rail running back & forth I am thinking now its the gearbox in the rear truck. When the 'zzzz' occurs, the loco slows down, so its losing tractive power. It sounds a bit like a missed gear shift in a stick shift car, the motor revs up, then the revs come back down.
Tanked
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Posted - June 28 2009 : 10:46:36 PM
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| Seems odd that it makes noise in reverse "full time" but not in forward. Have you tried running it backwards with the shell removed? Try running the loco with the rear drive shaft and worm removed. This will allow the rear wheels to free spin. If there is a gearing issue in the rear truck, the sound should still be present.
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Posted - June 29 2009 : 11:50:43 AM
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quote:Seems odd that it makes noise in reverse "full time" but not in forward. Have you tried running it backwards with the shell removed? Try running the loco with the rear drive shaft and worm removed. This will allow the rear wheels to free spin. If there is a gearing issue in the rear truck, the sound should still be present.
Originally posted by Hypoponera-June 28 2009: 10:46:36 PM
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Okay.
All running has been with shell off.
Whats the easiest way to get rds & worm out?
Tanked
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Posted - June 29 2009 : 11:52:28 AM
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It may be motor brush noise. The newer gold Athearn motors have this problem, and I think it's due to the brushes having a loose fit in the brush holders, so that they can shift their position when the motor reverses. I would take the brushes out, clean them, and make sure they aren't too worn. Sometimes changing the spring pressure will eliminate the brush noise, but not always. The loco will often slow down when they start chirping.
Some guys swear by CRC 2-26 electrical contact cleaner as a way to quiet them, but I found it left too much residue. Adding washers to eliminate end play in the armature is always a good thing too, because these motors tend to have a lot of it.
More tuneup tips here: http://www.mcor-nmra.org/Publications/Articles/Athearn_TuneUp.html
The Tyco Depot
Edited by - NickelPlate759 on June 29 2009 11:57:06 AM
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Posted - June 30 2009 : 11:43:52 AM
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quote:
Thanks Nelson, hadn't thought of the brushes - will check them out. I think they have a fair bit of wear on them.
Tanked
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