Tri-Axle Bogies

[Anonymous]

Having some bother with long wheelbase passenger cars on my 22" Mainline curves I removed the centre axle & wheels and voila! the cars stopped derailing. Even close up you can't really see that the wheels are missing. This might help others in the same predicament.

Cheers from Oz

[Eriediamond]

Oz, Glad you found an easy fix for the three axle trucks on your passenger cars. Please don't take this reply as a put down, but the biggest reason you had trouble was not the 22" radius curves, but rather uneven track work or poor quality wheel sets in those trucks or poor quality trucks. I suspect the reason for the derailments is this. Model trucks are build ridgid (not sprung) allowing no movement for the individual axles. Also the bolsters on these trucks are not located in the center above the center axle, either in front of or behind the center axle. Lets say say on a given truck the leading axle is #1 and the center one is #2 and the last is #3 and the bolster is between the #2 & 3 axles. Because of this the #2 & 3 axles are carrying most of the weight, so when #1 axles encounters a dip, instead of dropping down in the dip it hangs out there in the air high enough the flange rides over the rail and presto-derailment. By removing the center axle, you've effectively allowed the #1 axle to drop and follow the dip or irregularity. Out of round wheels will do the same thing. With todays smaller scale-like wheel flanges, the same thing can happen going through switch frogs at times. Diesel locos with three or four axle trucks are subject to the same thing, but because they are heavier can some times get away with slightly uneven track, but only rarely. I replied like I did because lots of times, derailments like yours are attributed to small radius curves, when that isn't the real problem. Thanks, Ken

[Anonymous]

You make some good points. Perhaps I should have explained that the coaches in question are Bachmann Spectrum fitted with brass wheels. The bogies tend to be quite long, allowing for scale. The track I use is 35yr old (re-cycled many times) Peco Code 100. It is laid directly on 12mm MDF sheeting, as I have modelled a combination of "Federal Street" --in MR last year, & open cut coal mines, and Iain Rices' "Coalport & Maryland". All of these are OK set on a flat surface-- of course the harbour is elevated with 18" curves. It is hard not to try & run long wheelbase stock, rather than look at them on a shelf! Hence my "adjustment".

Cheers Oz

[Anonymous]

I have found that the axles do not have any up and down movement like they do on real trains or sprung trucks, so on uneven track wheelsts are lifted off the track far enough for the flange to jump. Taking out the center wheelset let the truck stabilize bak on four wheels. I've taken a motortools with a sharp=pointed burr and slotted the journal on the inside where the end of the middle axle rides on both sides. This slot runs up and down only 1/16th of an inch, but it lets the middle axle float and puts the load on the outer axles just like removing it. It is a little tedious, but it can be done. My trains are ran more at eye level where the removed wheelset would be alot more obvious.

[Anonymous]

Thanks for that Tweet, I must confess I didn't think of a slot. After 44 years I'm still learning! What a great Hobby this is!