tender derailing

[esquire]

Mr Bachman
                   My spectrum (pacific) has developed a derailment issue with the tender,  It appears that the wires leading from locomotive to the tender are some how lifting the front tender  truck up off the rail consequently it derails at switches and curves,  I've tried to push the wires back up into the tender and vice versa this seems to be a temporary solution only.  Has there been a service bulletin about this kind of problem. or am I the only one experiencing it.  Thank you for anticipated response.

Neville  Happy Holidays

p.s. the locomotive is 5 or 6 years old and has worked very well up to now

[Atlantic Central]

Many say they have no problems, many of us, myself incuded, add weight to the tenders. I have always found that tenders should be heavier than average freight cars because the drawbar relationship with the loco is not the same as a coupler, AND the additon of the wires on these newer models adds to the problem. I add about 2 oz ot all my spectrum tenders, they stay on the track fine after that.

Sheldon

[Mark Damien]

G'Day Neville,

The Spectrum PRR K-4 Pacific & N&W J class; as well as Bachmann's British outline N Class 2-6-0, all have the same problem of the tender catching on points & track irregularities. These problems, to a large degree  are the result of the Cam Action Close Coupling System common to all three locos.

For this coupling system to work effectively requires it to be near frictionless. To do this would require highly machined cam surfaces in the loco & tender & roller bearings on the Cam Follower arms, neither of which are on the loco. No surprise really, it would be grossly uneconomical. So from the day you buy one, there is a built in problem.

For example, if you watch the loco on straight track, traveling away from you from above,  "after it has exited a right hand curve", the tender will have it's leading truck flanging the left hand rail. This will pick up any irregularity in the track, or split a set of points. The more you load the loco, the worse it gets. The N-class suffers most from load, to the point where the loco starts to flange the track on one side & the tender, the other. This is caused by the cam not being able to self centre, as it cannot overcome the friction generated near the centre of the cam.

To demonstrate this hold the loco & tender on a smooth surface & try to emulate the motion & load to make the cam work; You'll find it nearly impossible to to centre the cam as it will skip from one side to the other.


As the loco gets older , the cam surface gets dirty & lost lubrication, & the 'cam follower' may be worn & therefore has a much larger rubbing surface, causing more friction. Due to the friction problem this system does not work well from new.

Bachmann UK has even made modified wheelsets to "overcome the result" of the Coupling System, & much has been written about complicated & expensive modifications owners have made to their N-Class locos to make them run OK, well, sort-of. None of which involves ridding the loco of the cam system & solving the the problem. This, to me, seems a bit odd. Why would you attempt to modify the result!..... & not even attempt to solve the problem causing it.


If you want to test this, simply run any of these locos without the coupling system connected, the loco & tender run straight & true & do not catch on points or irregularities as they are not flanging the rail. So, if the Loco is OK & the Tender is OK, you can probably guess the rest!.

I have removed the Cam Action Close Coupling System, from all my Spectrum PRR K-4 Pacifics, N&W Js &  N Class 2-6-0s. I fitted ordinary metal or plastic flat drawbars, & have instant results, with all locos & tenders running perfectly.

Sheldons suggestion of adding some weight to the tenders will not go astray as the design of the wiring harness will still attempt to hi-jack your tender.

Personally I don't, preferring instead to get the harness to behave by bending the wire to better suit the situation or re-routing it under the footplate, where applicable. This, ofcourse is fiddly & most will not want to make modifications to their locos. It would be nice if Bachmann would start putting the wiring sockets on their yet-to-be-released locos, horizontally under the footplate like a certain other Builder of Locos In the US.

Finally, Kudos to Bachmann for attempting to improve model railroading products. I think, for the money its hard to beat a Bachmann. But, the cam coupling system, although designed with the best intentions,  really does not work.

[Atlantic Central]

Mark,

Be it cam action drawbars or conventional ones, they still act differently than couplers - that other brand you mention has very heavy tenders, regardless of how their wires plug in.

I too arrange the wires carefully, modify the conventional draw bars for better clearance, etc - but I still add the weight. I found bending a "dip" into the Heavy Mountain drawbar (along with the extra weight) eliminated all problems.

I don't own any of three locos you mentioned with the cam drawbar, but am familar with them, and agree with your assement of them, yet many people say they have no problem with them - I am also familar with how light those tenders are. Some of those who report good performance simply added weight.

Sheldon

[Mark Damien]

G'Day Sheldon,

I agree with you; extra weight is a a great equalizer, figuratively & literally, to overcome the lateral forces both the wiring harness & a Cam action close coupling system create. 

With the Cam action coupling system though, the more weight the loco pulls, the greater the lateral forces on the lead bogie, & the greater chance it has of finding that illusive irregularity in the track or turnout. 

Fortunately, the K-4 does not have the traction to pull enough 'train weight' to overcome  even a moderate amount of added weight in the tender. If it had traction tyres, that would change the equation drastically.

Apart from the derailment problems, having your tender & possibly your loco "Crabbing" along the track is a bit unsightly. This is more noticeable with the N class [as used in Bachmann's 'IRISH Train Set'], and occurs even when running light.

In regards to the Brand of Locos Incognito, their harness [on many of locos] springs back into the tender & so has no excess wiring suspended between the units, reducing the problems we are so familiar with other systems. 

On some models this feature, is not present & in these cases, I lift the tender shell & bend the wires toward the back of the tender, where the harness plugs into the PC board. This creates a spring action, which sucks the excess wires back into the tender after coupling. This lasts indefinitely, if care is taken not to over-extend then harness when coupling & uncoupling.

The wiring harness in the Bachmann Low Boiler Ten Wheeler is the most critical to get right, don't you think?

I had one running great for months, then packed it up & took to to a friends, where I spent the best part of the night fiddling with it.

At that point I decided this is not how it should be. Not wanting to do major surgery to change the position of the locos harness sockets, I mucked around with the tender & the Harness itself. I found two areas  I could improve. The first being the harness wires glued together. I swapped them with a set from another Bachmann loco - the unglued set are much more pliable.
The second problem, was the hole in the tender floor where the harness exits, rubs on the lead axle, causing a braking/skidding wheel, & those horrible lateral forces causing the lead axle to Flange the rail & cause derailments.
I removed the tender shell & drilled a hole in the floor where the coal spill is. I  then fitted a KADEE coupler box to route the harness above the axle & smoothly down each side of the drawbar to the loco connection. It has very little slack & the harness no longer drags on the sleepers.

These are just my solutions to some problems & everyone has a different viewpoint & their own solutions.  Any suggestion to make these little bundles of joy run better, couldn't be bad

P.S. Gene, if you're there, the 2-8-8-0 lark, has had some serious consideration, & appears feasible. I have some more measuring to do, but it looks good. I was thinking I might give it a really weather beaten, neglected look, so no particular road number & name willbe legible [or blamed] 

[Atlantic Central]

Mark,

Again, not owning the K4, or the J, I can only go on the experiance of others and I agree about the side pressure and "crabing" action.

I have a large fleet of Bachmann locos, just not those models.

I do not have the low boiler 10 wheeler either.

I do have two of the high boiler 10 wheelers, both of which have been converted to oil fired medium vanderbilt tenders - after adding weight to the tender they run fine with no other modifications. My wires are easily arranged to not drag the ties/sleepers.

I have 6 Heavy Mountains, with the drawbar modification discribed above and added tender weight - again no wire issues.

I have 5 Consolidations - tender weight and careful wire arrangement solves all issues.

I have 3 2-6-6-2's, converted to the long vanderbuilt tenders. a very slight up bend to make the drawbar level, and the tender weight, was all that was needed to make them run perfectly.

As to pulling power and the effect of added tender weight, I know from others the K4 is not a good puller out of the box - more loco weight seems in order. As for the locos I have they all pull very well - If you have followed any of my other posts you may remember the work I have done with free rolling trucks and how it dramaticly increased the number of cars pulled.

On the topic of that other brand, I have 2 of their Reading 4-8-4's and had to add weight in the smoke box to correct its poor balance and tracking and had to modifiy the tender frame to elimiate drawbar binding, so they are far from perfect either - but the tender, even without sound, is plenty heavy as is the one on my N&W Class A.

The 1-2 oz that I add to the tenders has had no measurable effect on pulling power with my very free rolling stock.

Let me just also note here that the reason I do not have any of the other locos in question is because they do not fit the theme of my railroad and I am not a collector, I only buy items that fit the theme I have planned for my layout.

In closing let me say that I surely could have provided more info in my first post and made more clear what may have been needed. And, if I ever did buy any J's or K4's, I'm sure the drawbars would be changed before they ever saw a piece of rail.

Sheldon

[jsmvmd]

Dear Mark,

Very impressive is your knowledge and explanations.  I consider you and Sheldon et al to be very bright chaps.  He has helped me tremendously with my foray into wireless cab control of an upcoming HO layout.

Thank you for your good tips, which I will put to good use!

Best Wishes & Merry Christmas!

Jack

[SteamGene]

Sheldon, which way did you bend the draw bar of the heavy Mountain? 
Gene

[Atlantic Central]

Gene,

I will e-mail you a drawing if you want - what I did was to bend a dip in the drawbar directly behind the loco end mounting screw hole. The dip is about 1/8" down and about 1/4" long, than back up to its original horizontal line.

This does several things, it shortens the drawbar very slightly and leaves a larger clear space for the wires right at the loco sockets. Than by neatly bending the tender wires right at the plugs the wires no longer interfere with the drawbar.

Sheldon

[MC]

Thanks guys,
My new K4 has been driving me nuts with the tender derailing. I have been trying to find out what is wrong with my track and now maybe I can look for the real problem. I went back to Gene's info on adding weight to find out what he had done so I will try that first.
MC