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Bachmann Class 66 - Derailing on Points but not a b2b or nem pocket issue


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Hi all,

 

I have an issue with my Bachmann class 66, i have not had it that long, already have a couple of Hornby 66's. the Bachmann is derailing on Hornby points, i took a video here:

 

have been searching and reading and trying the various fix's

 

I have set the back to backs on the wheels to 14.4 using a gauge and it does not seem to be snagging the pocket, have also tried adding a washer under the boogie to raise it up a bit. 

 

any help which what im missing? 

 

Cheers

Daz

 

Edited by Dazzlerofkernow
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Is there anything obvious happening at the other end of the bogie, particularly with respects to the track leading up to the points being level? I've had an issue with Bachmann class 47s where they didn't cope well with the points being on a gradient compared to the next bit of track, causing one end of the bogie to lift.

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As above.  The leading wheel spins without forward movement, then you have movement and it derails.  Just before it spins you see the flange (left side as you view it), ride up on your track.

 

But the question now is why isn't the bogie negotiating the point as it should.  Does it do this on any other similar point?

 

Interesting watching the video whilst wearing headphones!

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Probably a little obvious but does this happen when the loco is running in same direction through the point but opposite way round? Or indeed, what happens when loco runs through point in opposite direction?

The answers may give some clues.......

In my limited experience, and not with this loco, but when an odd loco didn’t like a point that others were ok with, (but others points and this loco combinations were ok)  I found on a couple of occasions, the issue seemed to be the point was not sitting quite flat - I’d managed to lay it with a slight twist, due to untrue baseboard.

Edited by ITG
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Hi Thanks for all the reply's will try to answer all of them, 

 

first up its a standard Hornby R8072 and it happens on a few of these, could it be just too small a radius? (im still building the main layout, this is a tamp layout on a board on the kitchen table) I have some express pecos to go on the main layout. 

 

this happens in both directions and the bogies are free turning, I have added a washer on the top of the bogie's to make them a little higher so they dont snag the frame. 

 

as for the watching with headphones, in the slowmo it makes quite  a thump as it comes back down! lol 

 

not sure what it is that's making it hit the V of the points but does seem to do it on all of them, its a great runner on a loop but does not seem to like changing tracks :P

 

Cheers

Daz

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6 hours ago, smokebox said:

Those wheels look quite thick, so it may work better if you reduce the back to back down to somewhere near to 13.9mm, which was the standard that Hornby used in the not too distant past.

That's an interesting idea, I wonder what the standard wheel thickness is...

 

I checked with me gauge and a set of calipers, 

 

I saw a post about the plasticard on the checkrail might have to get some and give this a go. 

 

Also the centerwheels are free to move left and right they are not stuff at all. 

 

 

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Mmm not sure that narrowing the checkway with platicard is going  to help. If it is only this loco then the problem is with the loco, not the track.

In that case, the b2b are just too wide. As suggested above, you need to double check and narrow them ever so slightly. 

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Its a back to back issue. loco B to B too wide for the point. the check rail should hold the flange away from the V of the frog. If the B to B is too wide the flange rides up.  2 nd radius points are marginal for 66s and the like anyway.    The trouble is some locos need the wider flange way to cope with their narrow B to B some Hornby were 13.9mm approx.  I regauge coaches etc to  14.25 mm approx Hornby Dublo 2 rail plastic wheel B to B with a go/ no go gauge with 14.2 and 14.5mm ends

I haven't had any issues with Bachmann on Peco Streamilne points but have re gauged lots of Triang Hornby and Hornby locos to 14.25 to get them through Streamline points.  

I suspect the Hornby points may have wider gaps between check rail and running rail than Peco set track,  

Relaying with code 75 and putting the old stuff on eBay for me to buy is a possible solution.

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I have encountered similar problems with Bachmann 66s.

 

All 4 turns into the fiddle yard are 4th radius Peco (24" more or less) and the lead wheel derails - not the same turn for each loco!

 

I replaced the settrack on one turn with flexitrack and this cured it (same radius!) although 66 714 Sence still has a problem running on one turn.

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15 hours ago, ikcdab said:

Mmm not sure that narrowing the checkway with platicard is going  to help. If it is only this loco then the problem is with the loco, not the track.

In that case, the b2b are just too wide. As suggested above, you need to double check and narrow them ever so slightly. 

 

You may narrow the flangeway on the check rail side a little (this is usually too wide anyway) but this will pull the wheelset away from the nose of the crossing.

 

Try it with some card first or clear plastic from packaging.

 

Dave.

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so i did a little test i reduced the b2bs down to 13.9 and guess what.... no derailing! initial testing looks good will do some more testing over the weekend, looks promising! (only tested on a short bit of track with a couple different points, will test on the temp layout next time its out) 

 

Cheers

Daz

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From the excellent video, it looks to me that the real problem is the bogie not turning enough. When the offside wheel rides up onto the vee, it immediately pulls the nearside wheel up with it, as if the bogie is incredibly rigid. However, when the offside wheel drops off the vee, the bogie twists before the nearside wheel is dragged off the top of the check rail, so the bogie is not as rigid as all that. Even when the offside wheel rides up onto the vee, the nearside wheel ought still be able to remain in the flangeway, but clearly it does not want to, so my guess is that the bogie at that point is already turning as much as it can. What is restricting its movement I cannot see. It could be the other two wheelsets or it could be something else.

 

Clearly the point check rail gap and the locomotive's original back to front measurement (back to back plus flange thickness) are incompatible, but in some respects it does not really matter which is at fault. Reducing the back to back by 0.5 mm shifts the whole bogie 0.25 mm further to the left (in the direction of travel), and then the offside wheel is shifted another 0.25 mm away from the vee, all without changing the angle between the bogie and the locomotive. If you went and reduced the check rail gap instead, although this would also keep the flange away from the vee, the bogie would have to turn a little more, and this appears to be the thing the bogie cannot do.

 

However, reducing the back to back is probably something of a fudge. Unless the locomotive has particularly thick flanges (about 1.25 mm), you should not need a back to back of 13.9 mm, and you might encounter a problem running through finer-scale points, if you have any on your layout or if you want to run the locomotive on someone else's (does anyone know how wide Peco flangeways are these days? I was under the impression they would not accomodate 13.9 mm back to backs). What might be worth doing is slightly increasing the back to back till you find the largest size that works. If you can get to 14.2 mm without derailing, your locomotive should run on any proprietary track.

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On 30/11/2020 at 20:42, Dazzlerofkernow said:

so i did a little test i reduced the b2bs down to 13.9 and guess what.... no derailing! initial testing looks good will do some more testing over the weekend, looks promising! (only tested on a short bit of track with a couple different points, will test on the temp layout next time its out) 

 

Cheers

Daz

 

Daz.

 

This was always going to work but if you run your locos on any other type of track you may well find the opposite problem in that the b2b is too narrow.

 

Try the plasticard before altering all the locos wheels.

 

Dave.

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Cheers Dave, I have some plasticard for further testing. At the moment the only loco I'm having trouble with is me Bachmann 66 although we the offer on at hattons I'm tempted by one of theirs...

 

(My Hornby one is perfect with no problems)

 

Cheers

 

Daz

 

 

 

Edited by Dazzlerofkernow
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