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Discussion Starter · #1 ·
I bought a K3 a while ago but did nothing more thqan send it for a test spin at the time. This holiday i put it on the layout and was horrified to find out it would not pull 4 Hornby Mk1 coaches, which are free running. I checked the loco out and the tender wheels spun easily as did the pony wheels. The thing just goes into violent wheelspin, tornado style at a twitch of the knob. Placing a finger lightly on it it starts to pull so i guess the adhesive weight is not anything like enough. While i was at it i removed the spring holding the pony down as it seemed a bit stiff and I wanted weight on the drivers. A slight improvement. So has anyone else had this problem on this and similar locos? Did you fix it by adding weight and where did you add it ? I have not opened it up yet to investigate this. I am amazed the manufacturer could not get the basic mechanics right but I am more interested in a fix. BTW my layout is flat and has 30" curves. Not a big ask.
Any suggestions welcome !
Andrew
 

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Check that the tender coupling pin is not too high and lifting the rear end of the loco up. If so shorten slightly by about 1/32" and this aught to cure.

My K3 will handle 12 bogies easily.

This problem also manifests itself with other Bachmanns - B1, V2, and J39.
 

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Aha - I took another look at my K3 and it has a different tender coupling to all the other Bachmanns with LNER tenders. It's a bar type but still check that the coupling is not lifting the rear of the engine off the track, and adjust if necessary.
 

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My examples all pulled decently as supplied, would start and pull at a reasonable speed a dozen coaches or 50 wagons on level track. Not enough traction for my 1 in 80 gradients with those loads however. Bachmann have done a fair job of getting weight in, with the footplate and boiler backhead in metal, but there is space for a lot more, and substitution of cast ballast with lead which is of higher density.

I wanted the loco to weigh around 400g, to deliver traction in keeping with this types' class 6 rating. (50g increments in weight carried on driven wheels per BR power class.) Straightforwardly achieved by substituting a shaped lead piece for the original ballast weight in the smoke box (I left the void in the top half for a decoder), a sheet of code 5 lead in the recess in the boiler backhead casting, and shaping strips of code 7 lead to fit neatly in the curvature of the boiler sides. That was enough, but had it been necessary the circuit board and the pillar it is attached to could be removed (with appropriate replacement wiring) and a lead block placed in the void created; and another shaped piece of lead about half an inch wide could be glued under the cab roof. Goes faster weighted up, as there is practically no wheel slip.
 

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Discussion Starter · #5 ·
Thanks for the replies. The loco does not seem to be sitting on the tender link as there is slop up and down. So I'll have to do it the hard way and take it apart, which I hate doing to new locos. Sometime in my life i came across a sheet of used roof lead which gives me a life time supply, no idea it had a code. But i am still puzzled why it does slip, especially as 34C's ones don't. Torque at axle, weight and coefficient of friction on the (peco) track must all be known, its hardly new technology. one of life's little mysteries.
Andrew
 

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I too have acquired a K3 recently. My problem with it is not so much wheel spin, but the tender derails over anything but the smoothest section of rail. It also will not run round anything less than radius 3 curves.
 

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Andrew,

Something I didn't mention, but which has been very noticeable on some of my Bachmann steam models, the WD in particular. Initially traction was pathetic, about 20 free running wagons all it could manage on level track without terrible wheel slip. But after a week of regular running (many hours) it was happy hauling 50 to 60 wagons around, and there was a a noticeable bright metal wear track on each driving wheel, cutting through the shiny black glaze film on the wheel tread as delivered. May be worth giving your K3 a lot of running to see if that helps.

Lead codes: code 7 = 7lb/sq ft., code 5, you can guess! Traditional measures for a traditional material. You can cut code 5 with one pass of a Stanley knife, code 7 takes two passes.

Noggin,

Have you got the tender on the closer coupling hole? It's a lot less tolerant of track irregularities close coupled. How does the tender do on its' own over the troublesome areas of the track? It only needs one tight wheelset to make a three axle vehicle very track intolerant. All three axles should have about 1.5 mm sideplay, and the centre axle should be able to rise the best part of 1mm.
 

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Also check that the chassis is true - place on a flat glass surface and check that all wheels are making contact with the surface. Slight irregularities in assembly can cause havoc as I found with one WD and one V2, both now sorted.
 

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I believe it is mostly residues from the production process - possibly the blackening - on the tyres. Most Bachmann steam models show gains in traction over the first few hours of running, in a range from about 20% to 300%. a sizeable minority come out of the box pulling well, and quickly show a gain which allows about 20% more train weight. The worst I have had was an example of the O4/ROD which could only exert enough force to pull the equivalent of 15 wagons (I use a weight lift involving a thread and pulley to make the assessment). After about four hours of running it could manage sufficient force for 60 wagons, rather more like it.
 

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Once again I agree with 34c, I have 2 of these K3's and both were a bother until I set the back to backs in the vice, clearly not an issue here, I too have had poor pulling from Bachmann locos that improves after a time, one thing I do is to run them in coupled as a double header so it gets used to running as a pilot engine, so the train is towed by the train engine. As above I have had them lifting, I have had poorly set springs on the pony truck, have had 'stuff' on the driving wheels etc.

Sounds a bit like the tender wheels may need gapping as well, have you tried running it without the tender attached, that also can make a difference, sometimes I have left off the tender and run it in backwards as a pilot engine. I agree again with last post worst example I have had so far was O4 LNER 3475 (or something like that)
 

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A while back I posted a thread about some Bachmann K3s (61869) having a very wide (toylike) flange on the drivers. The back to backs were correct but the flange was so thick that it caused the driving wheels to ride up and loose contact with the track. When one looked at the wheel centres it was obvious that the wheels were not pressed all the way home. The cure was to actually press the wheels closer, i.e reduce the back to back. Others reported having the same problem as did a few members with GW 2-6-0 locos
 
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