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Another loco stalling on points issue

2068 Views 29 Replies 7 Participants Last post by  Graham Plowman
Apologies for regurgitating this all over again - I have looked at previous posts on the subject, but I wanted to ask a specific question, in relation to a theory about the points design/manufacture, that I couldn't find an answer to.
My layout (controlled by DCC) incorporates Peco insulfrog points. My two locos, a J94 and a class 4575 small Prairie both tend to stall at low speeds at several sets of points, as the central of the larger wheels reach the plastic of the insulfrog.
I thought I had the problem sussed when I tried applying a small weight (about 10 grams) to each loco - at the front of the J94, and the rear of the 4575. (Each loco moving slowly in a forward direction). However the issue returned, despite the weights still being in position, when running in the opposite direction. I'm starting to suspect that the locos are being lifted imperceptibly at the frog which is affecting electrical contact to the driving wheels, and the application of the weights is just enough to keep the wheels in contact at one end.
So, here's the question. Would you think that the base of plastic insulfrog mouldings are not made low enough to the base of the track, to allow the wheel flanges to pass over them unhindered. If this is correct what remedy can be taken?
Thanks for taking the time to read
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Thanks 34C and Graham, great advice both.馃憤. I'll follow both suggestions through, but as I had a minute to spare and steel rule to hand I did a quick check on one, and it does seem there is a slight deviation.
By the way all points were already glued firmly down, using weights, so all good there.
Thanks again
Update - Having checked on the flex of the glued down points (and there was a little in places), I have now done belt and braces, so as well as glue, I've pinned all the points as well. Is there a slight improvement in slow speed running? Well, maybe, but equally could just be because I'm willing it to be better??
I have also used my vernier callipers to confirm that the loco wheel flanges do not interfere with the base of the groove of the plastic frog mouldings. All that's left now is to address the cause of the slightly raised section around the frogs
Hi Suzie,
Thanks for your comment, much appreciated. I'm beginning to wonder if I should have installed electro frogs instead 馃. It is noticeable that my J94, having a short wheelbase between the wheels with the contacts is more problematic than the longer class 4575.
Graham, thank you for your further explanation and the link, which describes the wiring and alterations needed very clearly. Very helpful.
Update 2 - I have followed the good advice above, and worked through several possibilities as to why I'm still seeing the locos stalling. I've made sure the pick ups are properly in contact with all the wheels in relation to axle side to side movement (thanks Butler-Henderson), and while I was at it, I cleaned the treads, flanges etc to ensure good electrical contact. I'm still not sure if I'm getting a momentary short somehow but the DCC controller does not trip, and I checked to ensure the wheel treads are not shorting at the converging of rails at the frog. Overall, the situation has improved with complete stops being reduced, but I'm still seeing the locos regularly 'stuttering' through the same points each time (although not all interestingly). However when the locos do completely stop it inevitably is when the central coupled wheel is over the plastic of the frog. When this happens, to get the loco moving again it either needs a slight downward pressure on the cab, or funnel, or slight sideways movement across the wheel axles. Of course, there is no such problem if the loco speed is increased.
I'm coming to the conclusion that I need to replace one of the points for an elecrofrog with associated IRJ to prove this cures the issue once and for all, then replace all the others likewise.
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Graham, thank you for continuing to help, it's much appreciated.
I should have said earlier that I did try your mirror technique which was very helpful, insomuch as it didn't highlight any issues with the points. I will try the two wire technique next, and also check for vertical axle movement. I had already found that the central axle has virtually no side to side play, and had wondered about that, although of course it does stop the possibility of the loco looking off centre in relation to the track.
I was naturally focusing on the track to identify the issues as the two locos I have are brand new, and I thought it unlikely that they would both have similar electrical pick up problems.
I don't know if other newbies experience similar problems, and although frustrating, it is giving me the opportunity to quickly learn various maintenance techniques which otherwise may have taken much longer to pick up.
Thanks again for your help and patience
I've now completed the two wire test on both locos and all axles. No problems encountered.
The total vertical axle movement appears to be less than 1mm on front and rear axles, and pretty much nothing on the centre one. This is the case with both locos.
Electro frogs are getting closer 馃槈
Ooops, I hope I will be corrected on this, but thinking about replacing the insulfrog No. 2 radius points (code 100) with electrofrog equivalents appears to be a non-starter. Having looked on Peco's website it seems that there are no electrofrog points with the same dimensions as the insulfrogs, not only are the overall lengths different but so is the radius and frog angle.
Back to the drawing board 馃
Thanks for the confirmation 34C. My set track points have a smaller radii with bigger angles than the Streamline range. Because my current layout is designed for a small baseboard, I won't be able to accommodate the different geometry if I attempted to change, so I think I'll be restricted to continuing to use set track.
On a more positive note, I think I'm better understanding why the locos are stuttering across the points, and I'm hoping to devise a solution to the issue. Work in progress 馃槈
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Hi Julian, thanks for your suggestion. Having played about with some kitchen foil to confirm the frog is the issue (rather than the closure rails or switch rails), I am thinking along the same lines as yourself.
I believe what is happening is that at very slow speed the loco wheel is 'dropping' off the V of the frog causing one or more of the other wheels on the opposite stock rail to rise slightly and lose electrical contact, when the loco tips slightly towards the frog. Using a test wire between stock rail and those wheels re-establishes contact and the loco starts moving again
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Thanks again Graham for your reply.
I'm learning all the time, not least to now call my track 'Crap Track', which has a certain ring to it. 馃榾
I've measured the wheel sets. On the Bachmann class 4575 they are 14.2mm to 14.3mm, whereas the EFE Rail J94 is 14.3mm to 14.4mm. I'll apply some gentle persuasion to see if the wheels will move, but I don't want to overdo it. I will also try shimming with plastic too, as that's a potentially easier one to try out.
Thanks RPJ, that's another possibility you've given me, I'll have a look at that too.
Thanks 34C. A bit risky, me and a hammer, I think I'll keep it in reserve at the moment
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