Bachmann Class 66 Curves

[Chrisjh]

I am running a modern image DCC layout. 

 

However I have a curve on the layout laid using Peco Flexible track, which I am not sure of the radius. All of my locomotives Hornby Class 60, Class 56 Bachman Class 47, Class 37, Dapol Class 68 all run perfectly well over the curve. However all of my Bachmann Class 66's derail at the same place and whilst they have the same dimensions as the class 60, I am wondering why they all de-rail whilst my Class 60 which is the same dimensions doesn't.

 

Greatly appreciate any thoughts as always.

 

Best,

Chris

[34theletterbetweenB&D]

You are looking at multiple possibilities from that problem description.

 

I would guess from the fact that your other similar locos - especially the 60 - negotiate the curve, that it is not simply that the radius is too small. But that should still be checked, compare to a second radius curve to make sure it simply isn't too small at some location. Check the track is level too, any significant off level' in one or or both rails may find out a 'track sensitive' loco

 

Possibilities I would look at if the track is good:

 

Take the body off and check that both bogies are not clamped too firmly by their pivot screws. If you suspect they are, slack off each screw a half turn, and test.

 

Next  'something' preventing a bogie from swivelling fully. One of the pick up wires snagged or trapped thus limiting the bogie swing,  a piece of trapped material likewise limiting swing, or exterior detail on the bufferbeam fouling on the coupler and limiting swing. Inspect the model inverted, and compare each bogie's swing with each other and that of the class 60, to see if one is limited in some way, then go looking for cause.

 

Also put a steel rule edge across the three wheels each side of both bogies and sight along the edge to ensure it is in contact with all three tyres. If the rule rocks on the middle axle that's trouble, it's an occasional fault on Bachmann's three axle bogies.

Edited May 20, 2020 by 34theletterbetweenB&D
to correct spelling

[Chrisjh]

Many thanks that's really helpful thank you. Look forward to trying this out at the weekend.

 

Best,

Chris 

[Guest Half-full]

Check the back to backs too!

[Chrisjh]

Thanks Half full how do I do that? 

 

All the best,

Chris 

[Dungrange]

28 minutes ago, Chrisjh said:

Thanks Half full how do I do that? 

 

You'll need a back-to-back gauge - see http://www.doubleogauge.com/shop.htm - third item down.  Assuming you are using commercial point-work and unmodified ready to run stock, you'd want the "Intermediate standard", which is 14.4 mm across the milled faces.  This should be a tight fit between the backs of the wheels on each axle.  If the gauge doesn't fit, then the back-to back dimension is too small (ie less than 14.4 mm) and if the gauge slips in too easily, then the back-to-back dimension is too great.

 

 

[Matt]

Bachmann's 66 has a well known issue that seems to affect many but not all where the bogies sit a little too close to the chassis and catch on curves causing derailment.  Of my 6, I believe 4 are impacted this way (I've not had things running for a long time due a house move - have also not remedied the issue).  I'm sure somewhere within the Bachmann folder there is discussion of this issue and the remedies which if I recall correctly require inserting a spacer between bogie and chassis.

 

Hope this helps,

M

[Chrisjh]

Many thanks Matt, David that is very useful many thanks.

 

Best,

Chris 

[Guest Half-full]

3 hours ago, Chrisjh said:

Many thanks Matt, David that is very useful many thanks.

 

Best,

Chris 

A back to back is an essential tool to have.  When ever I buy a loco or item of rolling stock, I check the b2bs before it gets tested - it will surprise you how much these vary - even on the same model!

 

If the wheelset is too tight to get the gauge in, then use a small vice to grip (gently) one of the wheels and rotate the axle whist pulling - just a fraction at a time.

 

Its worth the extra bit of time taken to check these

[atom3624]

Are the axles sliding side-to-side freely enough.

 

Could be they cannot move that freely, limiting movement and the flanges gripping the rails and derailing?

 

Al.

[Chrisjh]

Many thanks Al and Haf full much appreciated will investigate over the weekend. Thank goodness for Model Railways during the lockdown.

 

Best,

Chris 

[The Black Hat]

Think Bachmann 66s don't like some tight corners due to the way that the shaft connects to the bogies from the motor. I have had issues where this has led to derailments but curve was tight. Suggest you check the radius and realign if needed.