2 axles with a gear wheel: in sync?

[philsandy]

Have just converted a Bachmann 9F to EM, it runs OK but just not quite as smooth as other locos I have converted, when running at very slow speed.

I'm sure the quartering is OK (no tight spot on each rev) and I have adjusted CV52, 54, & 55 which has improved running.

 

Something occurred to me, this model has 2 geared axles (2nd & 3rd), if the gear wheels are not in "sync" with each other, eg.say:

on the 2nd axle: a gear tooth is dead in line with the R.H. crank pin,

on the 3rd axle: between two gear teeth is dead in line with R.H. crank pin.

 

What I mean is that one of the gear wheels is half a tooth behind the other.

Could this have any effect? or as I suspect there is enough play in the gearing to allow for this?

[Miss Prism]

Could this have any effect?

 

Yes.

[RexAshton]

It could be your problem but I would think there would be enough tolerance in the chassis and rods. Have you tried running the loco on DC? I ask this because I had a G2 which showed similar symptoms to the ones you're describing. It worked fine in DC so I replaced the decoder - problem solved.

Edit - Have you checked that none of the pickups have been disturbed causing one or more to be out of line with the wheel rims and touching the back of the spokes instead?

Edited December 13, 2017 by RexAshton

[34theletterbetweenB&D]

If there are geared together rod coupled wheelsets, you really want jig assembly to ensure consistent gear tooth to crankpin placement.

 

I don't know why Bachmann felt this was necessary. Before this model came along I had managed four 4mm 9Fs, all driven on a single axle. The first was very visibly driven on the centre axle, but the latter three all drove on the fourth axle (with a concealed driveline taken down through the firebox and then turning forward onto the axle.) The one time 'Locoyard' conversion of the pushalong Hornby 9F to loco drive drove on the fifth axle, and the one example I saw ran smoothly from dead slow.

 

How easy would it be to take an axle gear off and see if that solves it? If you can leave the drive to the centre axle only that should be good. (This is a loco which I have never had apart, in a deviation from my usual 'within hours after it is home it is in pieces' approach. They simply run so well that I haven't felt the need to fiddle.)

[philsandy]

Thanks for your replies.

 

I will try to get both gear wheels in line with each other.

A 1.1 mm drill passed through the crank boss will show where the gear tooth is in relation to it, then twist the gear to align a tooth with the drill.

Failing this I'll try it with only the one gear on the centre axle.

[Flying Pig]

Would it be possible to drop out the spur gear between the two axles? That would avoid potentially disturbing a wheelset.

[John Tomlinson]

I bought a couple of these shortly after they came out, and was disappointed with the slow speed running. 

 

I mentioned this to a Bachmann rep at a show, who suggested that I attempt to go for one axle drive only, as that might improve matters. I've never done this, but it does, as has been said, sound a good idea.

 

By the way, in process of messing with the loco, and despite being careful, one of the valve gear rods broke close to a pivot hole. I managed to superglue a sliver of brass behind to make a repair, but be aware the metal quality is not the best.

 

John.

[Il Grifone]

Any sort of parallel drive needs to be spot on to avoid problems. Slop is only going to make matters worse.

 

My Hornby tender drive 9F suffers from occasional coupling rod seizure due to too much free play in the motion.

[Titan]

I believe Lt-Col L. F .R. Fell had this problem too, although you would not like his solution...