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Model Forum / General / Railroads / June 2006Advice on jerky running
Hi all, I have just disassembled a Bachmann J39 to fit a DCC decoder, it used to run fine before, but now it seems to have acquired a tight spot in the revolution of the wheels. I'm not entirely sure how this could have happened, I certainly haven't been fiddling with the wheelsets. I suspect the quartering may have gone off slightly, but am not sure. Any advice on how to correct this? BTW, fitting the decoder wasn't that easy. Had to put it in the tender eventually and channel the wires to the loco. Then there were also problems where the connection on the motor was managing to get a feed from the chassis, despite being isolated. Turned out the plastic coating on the DCC wire had a split and was touching the motor casing's metal, which in turn had contact with the chassis... Ian J. > Hi all, > [quoted text clipped - 4 lines] > the quartering may have gone off slightly, but am not sure. Any advice on > how to correct this? > Ian J. I'd be very surprised if you had really managed to alter the quartering; that usually takes some force, and you'd certainly notice you were doing it unless the wheels are loose on the axles, which would be a manufacturing fault. Other possibilities include (i) general binding - at the 'tight spot' does every axle have a reasonable amount of side-play, or is one of them binding, perhaps caused by a mis-aligned keeper-plate or a bit of flash on the back of a wheel catching something; (ii) muck in the teeth of one of the gear wheels (I don't know the details of the drive-train on this loco); (iii) slightly dodgy pick-ups or muck on the wheels preventing reliable pick-up - this can imitate binding astonishingly convincingly; (iv) wheels removed and not returned in exactly the same place - perhaps accidentally swapping them from one side to the other of the loco while you were working on it. There are many other possibilities which could cause this problem, and no doubt other people will have their own suggestions. The classic way of finding out if the binding really is caused by a quartering / coupling rod problem is to remove the motor - or whatever it is in the drive-train that prevents the chassis free-wheeling - and then pushing the motorless chassis along on a piece of paper to see if the binding still exists. If it does, then you'll know where the problem is, which is the first stage to fixing it. Of course, if the bind is only slight you could always use a feedback-enabled chip to smooth it out ;-) John >> Hi all, >> [quoted text clipped - 37 lines] > > John Thanks for the response. The J39 is one of the old split chassis locos, so there are no pickups. The decoder I've used is a Lenz Gold, so that has feedback enabled, but the binding problem is still there.. :( I will have to examine the whole drive train and see what I can discover... Ian J. > Thanks for the response. The J39 is one of the old split chassis locos, so > there are no pickups. The decoder I've used is a Lenz Gold, so that has [quoted text clipped - 3 lines] > > Ian J. In my experience those split chassis locos vary between running very well and running very badly - I've seen manyinstances of each. I'd feel inclined to run a wire direct to each motor brush to see how it works then; if there is 'real' binding rather than a pickup glitch, this will show it - then, as you say, look through the drive-train to see if there's any grit in the teeth of any of the gears. John > Thanks for the response. The J39 is one of the old split chassis locos, so > there are no pickups. The decoder I've used is a Lenz Gold, so that has > feedback enabled, but the binding problem is still there.. :( It's almost certainly a problem caused by the motor & decoder not being compatible. It's possible with the Gold to change the settings to suit different types of motor. I can't remember the CV you need to adjust, but read the manual which came with the decoder and the solution will be in there. I had a similar problem with a Bachmann K3. John. >> Thanks for the response. The J39 is one of the old split chassis locos, >> so there are no pickups. The decoder I've used is a Lenz Gold, so that [quoted text clipped - 9 lines] > > John. Are you sure? when I tested the motor before attaching it to the chassis it seemed absolutely fine, and the problem of the jerkyiness only happens at one point, the same point in the revolution of the wheels... Ian J. > Are you sure? when I tested the motor before attaching it to the chassis > it seemed absolutely fine, and the problem of the jerkyiness only happens > at one point, the same point in the revolution of the wheels... Of course I can't be absolutely sure, but the symptoms sound exactly the same as those with my K3. I t ran fine of DC but didn't like the Gold decoder I fitted, until I tweaked the 'motor type' settings. You've nothing to lose anyway even if that is not the cause, all you do to put things back to where they were is to reset factory settings on the decoder (write '33' to CV8). John. >> Are you sure? when I tested the motor before attaching it to the chassis >> it seemed absolutely fine, and the problem of the jerkyiness only happens [quoted text clipped - 9 lines] > > John. I don't seem to be able to find any advice on which motor type setting to use with which motor, any ideas on which settings go with which motor types? Ian J. > I don't seem to be able to find any advice on which motor type setting to > use with which motor, any ideas on which settings go with which motor > types? Just experiment and see what happens. John. >Hi all, > [quoted text clipped - 13 lines] > >Ian J. Iassume this is an 6 coupled loco. To illiminate the possibility of a motor / gear train/decoder problem -- remove the coupling rods and run it on the straight and level. If all is well then the problem is in the quartering/coupling. > Hi all, > [quoted text clipped - 13 lines] > > Ian J. Hi all, Many thanks for the replies so far. I have disassembled the loco again, checked the gear train for any bits of dirt that might have been causing trouble, but found nothing. It does seem as if the centre wheels don't run quite true, wobbling slightly, however when I put the loco back together it did seem to perform better, if not as before. So it might be a combination of a slightly poor running that didn't show with conventional DC, and the addition of the decoder. I have yet to try out the different motor settings to see what effect they have, I will post back once I have tried them. Ian J. > Many thanks for the replies so far. I have disassembled the loco again, > checked the gear train for any bits of dirt that might have been causing [quoted text clipped - 6 lines] > > Ian J. Good luck, and do let us know how you get on! Is the centre axle on this model fixed, or is it sprung as on some Bachmann models? If so, could this be puhsing the axle out of alignment? John Ian, >It does seem as if the centre wheels don't run >quite true, wobbling slightly, Wobbling wheels can be a sign of quartering being off - i.e. the coupling rods force the axles out of normal alignment to accommodate the errors in quartering. Jim. >> Hi all, >> [quoted text clipped - 27 lines] > > Ian J. Well, I've tested the J39 with various motor settings, it seems to like bits 1 and 2 (0 and 1) (decimal 3) being set best, though it wasn't much of a difference between them all really. Btw, for John (caronprom) the J39 is a solid chassis 0-6-0, no springing whatsoever... Ian J. >>> Hi all, >>> [quoted text clipped - 36 lines] > > Ian J. Until I got one of those snazzy guage tools from Mainly Trains I frequently set wheels slightly out of paralllel when adjusting the B2B - result of levering one side out then the other, but differing amounts. This often resulted in wobbly wheels and somewhat jerky running. Worth a check. Cheers, Simon (Snipped) > Btw, for John (caronprom) the J39 is a solid chassis 0-6-0, no springing > whatsoever... > > Ian J. Let's be clear here - you haven't taken the wheels of the axles at all, you've just removed the wheels and their axles from the chassis after taking off the keeper-plate? If that's all you've done I can't see how it could possibly affect the quartering - if it was out to begin with, then that's a manufacturing error, but I'm supposing that you'd have seen that to begin with, and anyway since you've been tinkering with the loco I suppose that they won't accept responsibility. Next question - is it possible to do anything that will enable the chassis to 'free-wheel' (Lifting or removing the motor for instance? John > (Snipped) >> [quoted text clipped - 15 lines] > > John Yes, I did that and it free-wheeled more or less ok. I think there might be an alignment problem in the gears though as they do seem to 'hunt' while being turned by the motor, and that has an effect on the geared axle. Ian J. >> (Snipped) >>> [quoted text clipped - 22 lines] > > Ian J. Dont know about that, gears do that anyway. Be more concerned that more or less ok free wheeling translates to jerky when coupled. Did you check the back to back all round the circumferance ? Simon >>> (Snipped) >>>> [quoted text clipped - 28 lines] > > Simon I didn't test without the coupling rods, so the freewheeling was with all the wheels coupled anyway. Ian J. >>>> (Snipped) >>>>> [quoted text clipped - 33 lines] > > Ian J. Sorry it was late, didnt mean coupled as in with coupling rods but all connected up with motor and gears. The additional stresses are what changes more or less ok to jerky. Strange but would really like to know if B2B same all way round on wobbly wheels - any chance ? Cheers, Simon >>>>> (Snipped) >>>>>> [quoted text clipped - 42 lines] > Cheers, > Simon I don't have a B2B gauge, but the measurement by ruler/eye looks about right. Ian J. >>>>>> (Snipped) >>>>>>> [quoted text clipped - 49 lines] > > Ian J. I used to use a bit of plastic cut to about right size - about right is fine as long as everything is consistent. But must admit when got a proper guage (L shaped, approx 3mm thick) it made an amazing difference to one or two locos. went from slight wobble of wheels to perfect with no wobble and loco was much smoother running. Cant say what tolerence required but 0.5mm differnce results in big wobble. Simon > Sorry it was late, didnt mean coupled as in with coupling rods but all > connected up with motor and gears. The additional stresses are what changes [quoted text clipped - 4 lines] > Cheers, > Simon Now I'm totally lost ;-) Were the coupling rods in place when you did the freewheeling test? I presume that the drive-train from the motor wasn't! John >> Sorry it was late, didnt mean coupled as in with coupling rods but all >> connected up with motor and gears. The additional stresses are what [quoted text clipped - 12 lines] > > John Coupling rods have always been in place, motor hasn't. In the freewheel test the motor gears were removed, and wheels seemed ok (there was a very, very slight binding but I couldn't even figure out exactly where it was occuring.) With the motor and gears in place, but without the base plate of the chassis in place, there is a definite binding occuring at one point in the revolution of the wheels. That's why I feel that maybe the gears are contributing to the problem. Anyhoo, the loco is generally running better now, so I am less bothered with it specifically at the moment as I have others to attend to. Many thanks for all the general advice to all who replied. Ian J. Ian, >Coupling rods have always been in place, motor hasn't. In the freewheel test >the motor gears were removed, and wheels seemed ok (there was a very, very [quoted text clipped - 3 lines] >the revolution of the wheels. That's why I feel that maybe the gears are >contributing to the problem. If your quartering is off then you can get the results you are getting. When the axles rotate with faulty quartering, then the chassis tries to get over the tight spots by using the play in the axle bearings and the crankpin bearings. You can see this when a chassis runs, and one or more axles tend to rock. When you engage the motor and gear, you restrict the free play on the driven axle and the out of quarter chassis has lost a bit of its elbow room and tends to bind more. You might find that it runs better if you pack the motor mount so that the gear mesh is very loose, which might let the axle move around a bit again. Jim. > Ian, > [quoted text clipped - 20 lines] > > Jim. I suppose what has happened must have been a slight loss of true quarter when I took the chassis apart to install the decoder, but I did try to manually move the wheels on the axles and couldn't budge them, and I definitely didn't handle the wheel set roughly, quite the opposite in fact. Whatever happened, it looks likely that quartering will need adjusting to get a smooth runner again... Ian J. > I suppose what has happened must have been a slight loss of true quarter > when I took the chassis apart to install the decoder, but I did try to [quoted text clipped - 4 lines] > > Ian J. Dont stop now, its excellent experience cos theres so many 'slightly out' locos that benefit. Theres almost as many causes. I realise its arkward as youve just chipped it, but if you can stand it upside down and apply continous power so that you can watch wheels, coupling rods and valve gear etc then sometimes its a lot easier to spot the problem. Simon >> I suppose what has happened must have been a slight loss of true quarter >> when I took the chassis apart to install the decoder, but I did try to [quoted text clipped - 12 lines] > > Simon Well, I did that, that was how I found that it was the gear meshing that seemed to be pushing the wheels to bind. This looks to be a quartering issue, as far as I can ascertain. Ian J. > Well, I did that, that was how I found that it was the gear meshing that > seemed to be pushing the wheels to bind. This looks to be a quartering > issue, as far as I can ascertain. > > Ian J. I'm missing something here on quartering and would like to be re-assured or corrected. Having removed all the wheels on the average Hornby or Bachmann loco i then :- put 1st wheel on axle put axle onto chassis put other wheel on axle in approx posit set one side to 1200 look at other side - twist wheel on axle to 0300 (or 0900) look back at first side, reset it if not right look at other side - twist..... and so on till happy theyre right. Then do other wheels to match. Is this, in the teams opinion, just not good enough ? Cheers, Simon >> Well, I did that, that was how I found that it was the gear meshing that >> seemed to be pushing the wheels to bind. This looks to be a quartering [quoted text clipped - 20 lines] > Cheers, > Simon Er, why are you removing the wheels from the axles? Certainly on locos like the J39, there is no specific need to do this. On a loco such as this the three axles come out as a 'unit' - the coupling rods keeping them together. Ian J. >>> Well, I did that, that was how I found that it was the gear meshing that >>> seemed to be pushing the wheels to bind. This looks to be a quartering [quoted text clipped - 17 lines] >> >> Is this, in the teams opinion, just not good enough ? If it works for you then fine. Its usually easier to assemble the first wheelset before putting it in the chassis, then you can see both sides at once and get it right first time. Only if you have to deal with the very old chassis that don't have keeper plates do you have to assemble the wheelsets in the chassis as you describe. Keith >>>> Well, I did that, that was how I found that it was the gear meshing >>>> that [quoted text clipped - 27 lines] > you describe. > Keith true, I do do that if theyre fully out. Only described this way cos Ian's are (presumably) back in now and I wouldnt bother taking them out just for quartering. Simon >>> Well, I did that, that was how I found that it was the gear meshing that >>> seemed to be pushing the wheels to bind. This looks to be a quartering [quoted text clipped - 27 lines] > > Ian J. Lots of reasons. well one or 2 such as on second hand loco thats been oiled from a tanker. Have to remove crankpin so may just remove wheel anyway. Nearly always remove coupling rods cos am ham fisted and dont want to bend them when cleaning wheels. With modern hornby its a devil to get the flat plastic sandwhich at base of chassis back on whilst keeping pickup strips in place. Easier to remove one wheel from axle. Any advice suggesting better ways always welcome. Cheers, Simon >> Well, I did that, that was how I found that it was the gear meshing that >> seemed to be pushing the wheels to bind. This looks to be a quartering [quoted text clipped - 20 lines] >Cheers, >Simon I too use the visual method! Having set one pair, I then attach the conn rod to one side. I then hang the other conn rod to the chosen master pair and adjust the 3 rd pair until it fits nicely at its apogee ( having locked the datum pair with a clamp. The centre pair or pairs can then be set con rod hole to wheel pin hole using a paper clip as a probe and if necessary a magnifying glass to see it ( essential in my case. The paper clip can also be used to determine the centering of the second pair as with such small diameters the wrong position is quickly evident if the axle centres are used as an aid to alignment i.e. set the first wheel with its crank pin horizontal to the axle pin and aim the other in the same plane. > Yes, I did that and it free-wheeled more or less ok. I think there might be > an alignment problem in the gears though as they do seem to 'hunt' while > being turned by the motor, and that has an effect on the geared axle. > > Ian J. If the chassis freewheels with no binding - hold it firmly down on a pad of paper while pushing it along to make sure that the wheels are turning properly, or run it down a slope - then you can be pretty sure that the quartering is fine, so don't mess with it! As suggested, the gears may 'hunt' a little anyway - are they all turning smoothly and without resistance? John >> Yes, I did that and it free-wheeled more or less ok. I think there might >> be [quoted text clipped - 12 lines] > > John Yep. Ian J. |
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