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55 minutes ago, Lacathedrale said:

I've managed to get my Jinty chassis rebuilt and rolling and I'm very pleased. There appears to be one final small hurdle to overcome however, before I can consider it the home straight. The motor I am using is an association flat can motor with a 1mm shaft. This needs to be adapted for the worm and bearing to 1.5mm.

 

Using the 'half gearbox' method I understand requires me to have a single continuous shaft from the bearing through to the motor, a length of approximately 15mm  - however the adapter shafts supplied by the association shops are only 8mm in length. To this end I have purchased some brass tube of nominal equal measurements (1mm inside/ 1.5mm outside diameter), but in any event, it is loose on the motor shaft.

 

I've already sent a request to Shop3 to see if I can get some of the uncut adapter tube, or in longer lengths - but failing that, is there a solution to maintain concentricity AND fix the brass to the steel motor shaft? See picture below - note the brass tube is obviously quite oversized, it won't poke out that far beyond the gearbox when I've figured out how to do this.

image.png

 

 

 

@CF MRC thank you kindly - should I not worry too much about maintaining its concentricity? it's very minor but over the inch or so it feels like it could be a problem!

 

Im a bit bemused as to why the motor is so far away from the gear tower. You can get the motor pretty tight on a Jinty - there's plenty of room in those big side tanks.

 

Jerry

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58 minutes ago, queensquare said:

 

Im a bit bemused as to why the motor is so far away from the gear tower. You can get the motor pretty tight on a Jinty - there's plenty of room in those big side tanks.

 

Jerry

 

Well, that's a fair point, d'oh! I can have the motor aligned vertically and move it forward about this far - maybe one or two mm further - before it fouls the gear on the middle axle - it's raised off the chassis with a thin piece of plasticard

 

image2.png

 

I can have the motor rotated 90 degrees and suspended above the driving wheel and it'll clear everything except the inside of the tanks and I've not got the equipment to do that, so I guess this is where it needs to be?

Edited by Lacathedrale

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Looking at this setup it seems to me that the worm itself is long enough to bridge the gap between the motor and the bearing in the gearbox.

If it is long enough you can mount the worm on the motor shaft with the adaptor sleeve and insert a piece of 1.5mm axle steel in the other side of the worm. This will then run in the bearing.

 

Jan

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Ah, so an adapter in one side of the worm and axle steel in the other side? Genius!

 

After some trimming and fettling, this looks like it will work with an 8mm adapter sleeve which is a much tighter fit - I'm lacking thread locker and have just ordered some, probably not a bad shout regardless.  Right now motor and adapter/worm shafts are just resting in place.

 

image3.png

Edited by Lacathedrale
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I'd want that worm a little further forwards so its not got the teeth of the wormwheel coming into the worm end.   Which might mean the front bearing has to be thinned or moved. 

 

Nigel

 

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It also looks to me as though the motor could be moved forward a couple of mms and still be clear of the final drive gear. 

 

Jim 

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3 hours ago, Nigelcliffe said:

I'd want that worm a little further forwards so its not got the teeth of the wormwheel coming into the worm end.   Which might mean the front bearing has to be thinned or moved. 

 

Nigel

 

 

The alignment of that bearing looks a little suspect to me - in all 3 photos I've seen it seems to be tilting the motor shaft downwards towards the back of the loco. Might be a good idea to unsolder it and file it down before refitting it.

 

Andy

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10 hours ago, 2mm Andy said:

 

The alignment of that bearing looks a little suspect to me - in all 3 photos I've seen it seems to be tilting the motor shaft downwards towards the back of the loco. Might be a good idea to unsolder it and file it down before refitting it.

 

Andy

 

Actually that isn't the bearing I intended to be used in the design - the same ones as used on the wheel axles are less bulky and do the job just as well. However you can file the one you have used down so there is more room for the worm to come forward.

 

Chris

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I'm not confident on my ability to be able to file down that brass bearing perfectly flat so using a phosphor bronze bearing might be a better shot and would appear to kill two birds with one stone, since I can double check the alignment while I'm at it.

 

I'll have a crack today and see how it pans out - thanks all!

 

 

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Personally, I would ditch the bearing altogether.

The motor you are using has chunky brass bearings, and with the worm being that close to the motor shouldn't need additional support at the other end.

Unless you get it absolutely perfectly aligned, that bearing will always be a source of additional friction. It may even stop the motor turning altogether.

As Jim suggested, move the motor as close to the gear as you can.

Use packing pieces to get the motor to the right height so the worm meshes nicely, then epoxy it to the chassis... like this:

10s.jpg

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Thanks Nick - I tried that before but I think my motor mount was too flexible, the chassis had warped after being bent and straightened, and I wasn't able to get a reliable mesh. I'm going to try with this one bearing and see how it goes - my sole justification is that I can cut it off and end up where I was before with no problem, but I can't put it back on!  I'll stop cluttering this thread though, thank you!

 

Edited by Lacathedrale

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2 hours ago, Lacathedrale said:

Thanks Nick - I tried that before but I think my motor mount was too flexible, the chassis had warped after being bent and straightened, and I wasn't able to get a reliable mesh. I'm going to try with this one bearing and see how it goes - my sole justification is that I can cut it off and end up where I was before with no problem, but I can't put it back on!  I'll stop cluttering this thread though, thank you!

 

 

You are very welcome to carry on cluttering this thread  I find the problems and there solutions of interest. For example Nick suggesting you might be better off without the bearing is slightly counter intuitive.

Thanks to all.

 

Don

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5 minutes ago, Donw said:

Nick suggesting you might be better off without the bearing is slightly counter intuitive.

It depends on how the shaft is supported elsewhere. There are big brass bearings at either end of the motor, and they ought to be more than enough unless the motor shaft is made of rubber.

 

I have built a loco with a similarly arranged bearing at the end of the worm. (Association Class 11 diesel shunter kit)

It has a Maxon coreless motor screwed into a mounting ring at the other end of the worm.

The idea was that the motor (with worm attached) should be removable.

Unfortunately, screwing the motor in tight upset the alignment and made the shaft jam in the bearing.

The way I solved the problem was to unscrew the motor 1/4 turn, smear Araldite round the edge of the fixing ring, and suspend the chassis verticlly with the motor running for half an hour while the Araldite cured.

An alternative approach in William's situation would be to fix the motor firmly in place, and then melt the solder on the bearing so that it aligns naturally to the orientation of the shaft.

Having built locos both ways, I am happy that both ways can be made to work fine, but experience says the bearing can be an added and unnecessary complication.

 

If the worm won't mesh reliably with the motor, either the worm bore is not concentric (not unknown!), the gear wheel is not concentric (not unknown!), the motor shaft is bent (highly unlikely), or the motor is able to move relative to the gear (???). The presence of the bearing will not mitigate any of these issues.

Another advantage of ditching the bearing is that you can use a worm with the right size bore for the motor shaft. This is more likely to make the worm run concentrically than gluing a loose sleeve onto the motor shaft.

 

Nick.

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4 minutes ago, Nick Mitchell said:

It depends on how the shaft is supported elsewhere. There are big brass bearings at either end of the motor, and they ought to be more than enough unless the motor shaft is made of rubber.

 

I have built a loco with a similarly arranged bearing at the end of the worm. (Association Class 11 diesel shunter kit)

It has a Maxon coreless motor screwed into a mounting ring at the other end of the worm.

The idea was that the motor (with worm attached) should be removable.

Unfortunately, screwing the motor in tight upset the alignment and made the shaft jam in the bearing.

The way I solved the problem was to unscrew the motor 1/4 turn, smear Araldite round the edge of the fixing ring, and suspend the chassis verticlly with the motor running for half an hour while the Araldite cured.

An alternative approach in William's situation would be to fix the motor firmly in place, and then melt the solder on the bearing so that it aligns naturally to the orientation of the shaft.

Having built locos both ways, I am happy that both ways can be made to work fine, but experience says the bearing can be an added and unnecessary complication.

 

If the worm won't mesh reliably with the motor, either the worm bore is not concentric (not unknown!), the gear wheel is not concentric (not unknown!), the motor shaft is bent (highly unlikely), or the motor is able to move relative to the gear (???). The presence of the bearing will not mitigate any of these issues.

Another advantage of ditching the bearing is that you can use a worm with the right size bore for the motor shaft. This is more likely to make the worm run concentrically than gluing a loose sleeve onto the motor shaft.

 

Nick.

 

Thanks for that Nick, the concept of suspending a chassis with the motor running while the araldite sets is priceless

 

Don

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What does it mean when wheels have a sticking point only when a) the chassis is oriented one way up, or b) flat on the workbench?

 

My Jinty was jamming very occasionally, so I assumed this was a meshing problem on the worm. Turns out, it carried on even without the motor/worm/gearbox attached. I figured it might be because the brake gear was interfering. Turns out,  after an hour of tweaking with no progress and removing it entirely, that wasn't the case either. (Which probably means the gearbox was fine)

 

Now, if I have one side of the chassis face up it's perfectly fine - even running against the edge of the workbench. But the other way up, or flat on the workbench it sticks part-way through a revolution. The only thing I can think of is that the muffs aren't cut parallel and it's catching, or the idler/geared muffs are binding.

 

Either way, it seems two steps backwards. I can't justify a lathe to cut the muffs to length, and I just can't seem to get them sub-mm perfectly parallel. I really just don't know if I can handle building ANOTHER Jinty chassis in the hope that the stars align perfectly - it's literally just one problem after the other and I'm seeing zero meaningful output after literally dozens of hours of trying.

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I am very sorry to hear you are having continuing problems, it is difficult ithout seeing it oneself. Firstly you say the loco was jamming occasionally, was this happening beforeque the motor and worm were fitted?

I did have a problem with an 0 gauge loco jamming once or twice in a two day show.d lift it off the track fail to see any reason and it would be fine when put back It was a little noisy so the motor was replaced with an ABC high efficiency motor gearbox the next show it didn't jam what it did do was remove a slide bar. I worked out that when all the tolerances were aligned in a certain way the coupling rod was just clipping the slide bar. With a worm drive it stopped the motor but the ABC box gave a much higher torque. Of course as soon as I lifted it things moved and you could see what was happening. My purpose in telling this is it points out that something not connected with quartering or crankpins can cause occasional jamming. If it was quatering alone I would expect it to be jamming or at least stiffening up at the same point in every revolution.

It would now seem that the problem is more severe. I am not certain what you mean by having it face up I would not be surprised if it didn't run laid on it side. I would probably leave it for a short period then come back to it and with a strong light and some magnification run it back and forth on a piece of straight track observing closely and try to be very sure before changing anything.

Don

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2 hours ago, Lacathedrale said:

Now, if I have one side of the chassis face up it's perfectly fine - even running against the edge of the workbench. But the other way up, or flat on the workbench it sticks part-way through a revolution. The only thing I can think of is that the muffs aren't cut parallel and it's catching, or the idler/geared muffs are binding.

I doubt it would be the muffs catching, as there shouldn't be anything for them to catch on.

Perhaps the spur gear on the driven axle is catching on the side of the worm wheel?

If you have a bit of side-play in either the driven axle or the intermediate gear axle, that could explain why it only catches when you rest the chassis on one side.

 

Occasionally I have found it necessary to thin gears to avoid this sort of thing happening. (mount gear on muff, mount muff in drill and use a file?)

Have you checked there are no burrs on the edges of the gear teeth that could be catching?

You could try putting marker pen on the edge of the gears to see if it rubs away in a particular place.

Some people lap the gears if there are rough spots by running them with toothpaste (or more drastically kitchen cream cleaner) to slightly abrade and polish the mating surfaces. If you do this, you need to be careful to clean away every last trace afterwards otherwise you will see accelerated wear. It sounds like you have a more than a rough spot though.

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Couple of thoughts if I may. That it depends on orientation seems to suggest something is moving, and that it happens once every rotation that it isn’t the worm/first stage gearing per se.

 

So, how tight are the rods on the crankpins, I.e. pushed up against the wheel face? They could be catching on the bosses.

 

If there is sideplay on the driven axle then the final drive gear could be catching on the first stage, or the chassis. It can be nip&tuck getting the gear positions correctly placed on the muffs, so the worm stage has minimal sideplay, but there is enough room for the final drive gear between the first stage gear and the chassis frame to have some sideplay.  It will sound very crude, but to prevent the teeth catching I always just file all the edges of the gear teeth at 60 degrees with a needle file so if the sides faces rub/slide against each other there is no catching.

 

I just slice bits off muffs with a scalpel. It doesn’t have to be precise.

 

It might well be none of these things. I would say what you are experiencing is something many of us have been through at times, when you just can’t seem to figure it out. Often it can be hard to find, but please don’t give up, you generally get there in the end.

 

regards,

 

Izzy

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I agree with everything Izzy says. As has been said, it's difficult to diagnose the fault without having the chassis in your hand to study closely. Sometimes you never get to the bottom of the problem and it just works its way out as the chassis runs in. Can you lubricate it and then sit it wired up and just let it run for an hour or so and then see what it's like after that? 

 

Jim 

Edited by Caley Jim
Edited for the usual predictive text issues!

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As others have said, without having the model in your hand it is very difficult to diagnose a problem. However, running it under a strong light with magnification is the best way to identify a tight spot.  One thing I would check is that a muff is not rubbing on a bearing - possible if the end of the muff is cut at a slight angle (mine always are!) and the bearing is not quite seated squarely in the chassis (i.e. the bearing is at a slight angle too - allowing the two "high spots" to catch every now and then).  

Where two gears are running face to face, I always try to file a slight angle (and polish with emery) on both sets of teeth to minimise the chance of the teeth catching, especially as the worm rotation will try to force the gear wheel to one side or the other, which gives the opportunity for the teeth to clash with those of the next stage gear wheel.  I think this often causes a slight bind or friction in one direction only (the other direction causes the worm to push the worm wheel away from the next stage gear).

As others have said, don't give up.  At the end of the day you have a chassis that does run albeit not as smoothly as you want at the minute.

Regards,

Percy Veerance

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Hi,

i discovered this problem once when I had fitted the balance weights on drivers (10 thou black plasticard with CA glue) and one projected a bit too much to clear the coupling rods. Easy to fix, either refit the offending balance weight or pack out the rods!

Keep going,

John

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On 27/08/2019 at 09:30, Chris Higgs said:

 

BR Lines will happily sell you a Farish Pannier body at a very reasonable cost.

 

Chris


At the risk of sounding quite dense.... BR Lines? I'd like to get a Pannier body (Never have too many!) but I am unsure who you mean?

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3 hours ago, Kylestrome said:

https://brlines.co.uk

 

HTH,

David

 

Yes, that is it. Bob Russell is a friendly chap. He currently has blue bodies as well as various more recent liveries.

 

If you want other liveries then Rails of Sheffield are often selling them on ebay although at a higher price.

 

Chris

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Have we drifted into some alternative universe?  Pannier body... BR Lines.... Blue bodies or more recent liveries.  I think you are confusing the query about an 08 on the VAG with this thread or have I lost the plot?

 

Don

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