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The Little House on The...

D869

Entry posted by D869

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More steamy goings on from my workbench. Now that I'm not frantically trying to make South Yard look less unfinished I've got back to some of the other items that have been in progress for a while. The main build effort amongst these is the David Eveleigh chassis for the Dapol 45xx. The various bits of this have been liberated from their paint shop boxes and put together in hopefully something resembling the right order.

 

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Under the hood is a Nigel Lawton motor coupled to the worm via a UJ with the intention of avoiding any end load on the motor bearings. The motor is on a removable mount - the intention being to test some alternative motors. In practice the only other mount that I've made (for the Association can motor) does not align the shafts quite well enough so the Lawton motor and mount is the only one that works.

 

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Everything going to plan? Not quite...

 

When initially put together the chassis (as an 0-6-0) ran appallingly. In fact I had to wire up some jump leads to a borrowed diesel bogie in order to get it to run up and down a reasonable length of track at all. Maybe I'm wrong but I think that a new chassis ought to move freely without any lubrication (not that I'd leave it like that) but this one didn't. My first gambit was to give it 20 minutes of running in (on Taw Bridge up in the loft) with this arrangement and then lubricate it. The chassis didn't free up noticeably during running in but ran quite smoothly once the gears were lubricated. So it stayed like this for a week or two.

 

The first test run after Nottingham was terrible - like it had developed a severe limp. This was quickly traced to a crankpin (on the side away from me) that had been bent. Straightening this restored smooth running but when tested carefully it still wasn't quite right - there was still some slight binding and when run at low speeds it always seemed to stall at the same crank position which seemed to be the same spot as the problem I'd had before lubricating it.

 

I'd proved already that the problem was not being caused by coupling rod binding - the mechanism had the same tight spot even with the rods removed so I decided that it must be coming from the drive train. I'd already found a few issues with this and I still wasn't really happy with it, suspecting perhaps some eccentricity in the spur gear on the axle. Last night I spent a lot of time fiddling and fettling the drive train as a last ditch attempt to get the loco working properly short of a complete strip down and rebuild.

 

For some reason my drive train just doesn't seem to have gone together as it should. First I found that the wormwheel was fouling the shoulder on the centre axle muff so I had to move the wormwheel slightly off the centre line of the worm to solve this. I also suspected that the same thing was happening with the spur gear on the axle and the shoulder on the wormwheel muff and had found during 'dry run' assembly that I could not fully push the spur gear up to the shoulder on the muff without it catching the wormwheel muff. You probably can't see any of this in the photo, but here's a photo from underneath anyway.

 

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This last problem could also account for the binding - rather than being eccentric the gear could have been slightly askew on the muff and still catching the wormwheel muff at just one point in its rotation. Resolving this without a strip down involved some leverage between the shoulder and the gear - probably not something you will see recommended in the handbook of correct chassis building practice.

 

I also found while fiddling with the gears that there seemed to be a definite machining burr on the edge of the spur gear. If the burr was uneven then this might also have caused the binding - giving the same effect as an eccentric gear. Fixing this without stripping down was not going to be easy but I used a small screwdriver to wear away the burr at bottom of each tooth gap and a thin strip of wet & dry attached to a stick of plastikard to smooth away the burr at the top of the teeth... followed by blu-tack to try to hoover up any filings.

 

I still couldn't see daylight between the wormwheel and the axle muff shoulder so I attacked the shoulder with a needle file (plus more blu-tack to remove the filings) until daylight was visible.

To cut a long story after all of this poking and prodding the chassis didn't seem to keep stalling at the same point :) . After so many problems I'm cautious about saying that it's fixed but we'll see how things go.

 

The pony trucks are another story. I wanted to pick up from both sides on each truck. I tried connecting a jumper wire but this caused too much 'steering' effect on the truck so it kept jumping the rails. It did prove that the pickup was much improved, so I wanted to persevere with it and set to thinking about how to transfer a bit more weight onto the trucks.... which made me wonder if I could kill two birds with one stone...

 

I wasn't sure if this would work but it was simple enough to try it and find out. The current arrangement might be described as a Simpson spring but I've not heard of anyone using them like this. Mine are 36SWG wire soldered to the frame spacers directly above the pony axles. They head back towards the driving wheels before making a sharp about face to come back and bear on the tops of the pony axles. Some adjustment was needed to get the pony trucks centred and to arrange for a reasonable amount of springing but so far the results seem encouraging in terms of staying on the track and electrical pickup is now better than ever.

 

The plan now is to fit some DGs and send it for a spell of testing before thinking about fitting the cylinders or doing anything to the body.

Oh, and I need a new controller. The Lawton motor doesn't like my AMRs when pushed to anything above a crawl (although the quality of the said crawl is exemplary!). So far I've been using an experimental battery powered controller for testing it but this is not a long term answer - the slow speed control is particularly hit and miss with this gizmo.

 

A few other things are gradually emerging from a long stay in the paint shop. The Hawksworth BTK is currently being subjected to my attentions with the lining pen

 

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You can also see the BG creeping into the frame. This is in for repairs because one of its bogies partly collapsed at St Albans. The bogie has now been strengthened with some brass angle and now seems very strong. I'd forgotten until recently that the BTK build and BG repair are related because I built a set of NPCS bogies with the BTK with the intention of swapping out the (long spring) bogies from the BG so that everything winds up on the correct bogies at the end of the process. My plan for tonight was to sort out the couplings ready for the bogie swap but then I got diverted to writing on RMWeb. A valid alternative to real modelling :nono:

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-missy-

Hi Andy :)

 

I had a similar thing with the chassis for my 14xx and found out that it was either a gear or a muff which wasnt quite eccentric and therefore making the whole thing run uneven with a tight spot at the same place every revolution. Dont tell anyone but I got around it with a fudge and turned down the diameter of the gear slightly to stop it jamming against the worm wheel which solved the problem really well. Fortunately even the 100dp (or metric equivalent) gears allow for a little tweaking. I always say to people that building a loco chassis is 40% actually building it and 60% tweaking it so it runs well.

 

With your modelling abilities Andy, I am sure it will be a fantastic little engine when you are done.

 

Missy :)

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D869

I had a similar thing with the chassis for my 14xx and found out that it was either a gear or a muff which wasnt quite eccentric and therefore making the whole thing run uneven with a tight spot at the same place every revolution. Dont tell anyone but I got around it with a fudge and turned down the diameter of the gear slightly to stop it jamming against the worm wheel which solved the problem really well. Fortunately even the 100dp (or metric equivalent) gears allow for a little tweaking. I always say to people that building a loco chassis is 40% actually building it and 60% tweaking it so it runs well.

 

With your modelling abilities Andy, I am sure it will be a fantastic little engine when you are done.

 

Thanks Julia. I'm glad to know that it's not just me that hits these snags. I didn't have an issue with the gears in the Manor so I didn't look at them too closely before assembling the 45xx. Sadly disassembly of a 2mm chassis is not (in the classic Haynes manual wording) 'the reverse of assembly'. I'll know better next time.

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-missy-

Disassembly of a chassis can also damage your enthusiasm too :P Another thing worth mentioning as you say, next time you know what to look for so the next one will be even better.

 

M :)

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richbrummitt

Two things I always do on a build with the 'raw' components as a matter of course; thoroughly de-burr all the gears and smooth the wheel treads through increasingly fine grades of paper (dry and then wet) followed by a good polish. I learnt as I went too and it can be confidence crushing.

 

I had a good look under Richard Wilson's build of the 45xx chassis on Saturday and he had similarly fitted pick ups to the pony wheels, but of a different design to your own. It seems like an excellent idea once tweaked such that the springs cannot lift the driving wheels away from the wheels significantly and reduce tractive effort. 

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2mm Andy

Hi Andy,

 

Have you used metric or imperial gears on the 45xx? (not that it should make a lot of difference).

 

The motor mounts look to be a very neat solution.

 

Andy

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DavidLong
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Andy,

 

The Lawton motor is coreless so probably won't like an AMR controller. On DC I use a Pentroller set to the coreless '16' setting for Lawton motors and they behave quite acceptably and they certainly don't on the 'iron core' setting.

 

David

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D869

Two things I always do on a build with the 'raw' components as a matter of course; thoroughly de-burr all the gears and smooth the wheel treads through increasingly fine grades of paper (dry and then wet) followed by a good polish. I learnt as I went too and it can be confidence crushing.

 

Now he tells me ;) I did the polishing thing though.

 

I had a good look under Richard Wilson's build of the 45xx chassis on Saturday and he had similarly fitted pick ups to the pony wheels, but of a different design to your own. It seems like an excellent idea once tweaked such that the springs cannot lift the driving wheels away from the wheels significantly and reduce tractive effort.

 

I'd be interested to know how Mr Wilson did his. Mine still need more testing before I can say whether they are definitely right but so far they seem to run through South Yard's extremely questionable turnout geometry with the loco both ways around so that's a good start. I wound up springing the Manor's lead bogie which was a big improvement but it needed some adjustment due to wheel slip when traversing not quite level baseboard joins.

 

Have you used metric or imperial gears on the 45xx?

Err... yes! :dontknow:

 

I bought the bits for this loco a long time before I started it (fancy that!) and the empty bags seem to have been tidied away so I can't actually remember. The instructions allow both options but the metric option has a greater reduction ratio, so I'm pretty sure that's what I went for.

 

Regards, Andy

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D869
The Lawton motor is coreless so probably won't like an AMR controller. On DC I use a Pentroller set to the coreless '16' setting for Lawton motors and they behave quite acceptably and they certainly don't on the 'iron core' setting.

 

Yes... unfortunately I don't have a Pentroller and the last two on eBay went for quite a lot of dosh. I think that building something is looking like the most likely option at the mo.

 

I might still have another crack at the can motor mount but from memory these motors are not massively keen on the AMR either. I suspect it's a size/inertia thing rather than cored vs coreless.

 

I know that most people will think I'm a Luddite for sticking with the AMR but in good condition (i.e. with a replaced potentiometer) they do produce superbly controllable slow running so that's quite a challenge for anything else to live up to and I've even reconditioned another secondhand one recently. Anyway I definitely need something different for the 45xx so it's going to happen one way or another.

 

Regards, Andy

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richbrummitt

I don't know what the issue is with the Pentroller (other than the man who did make them doesn't) but due to age of the design I suspect that there is some component obsolescence that would need to be designed out for any new version. I like the coast/brake functionality so I got a PICtroller. It seems largely similar except that it has a few more adjustment options and 'detects' what type of motor is presented, then works accordingly.

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D869

I don't know what the issue is with the Pentroller (other than the man who did make them doesn't) but due to age of the design I suspect that there is some component obsolescence that would need to be designed out for any new version. I like the coast/brake functionality so I got a PICtroller. It seems largely similar except that it has a few more adjustment options and 'detects' what type of motor is presented, then works accordingly.

 

Yes, that's exactly the issue.

 

I know that Jerry is a PICtroller fan but one of our friends in the North bought one (or maybe more) a year or so back and had issues with them. From what I heard they were taking too long to work out what sort of motor they were looking at with strange results while they were 'thinking'. This is all second hand info so I'm not ruling one out but trying to figure out a way to try one out before committing funds.

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queensquare
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Yes, that's exactly the issue.

 

I know that Jerry is a PICtroller fan but one of our friends in the North bought one (or maybe more) a year or so back and had issues with them. From what I heard they were taking too long to work out what sort of motor they were looking at with strange results while they were 'thinking'. This is all second hand info so I'm not ruling one out but trying to figure out a way to try one out before committing funds.

 

I reverted to my Pentroller as the Pictroller didn't like the little 8mm coreless motors - either Faulhaber or Nigel Lawton, it was great with all other motors. I really like the Pentroller and use it all the time. The great advantage with the Pictroller was that it eliminated my constantly forgetting to switch between the motor options on the Pentroller.

 

Jerry

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D869

I reverted to my Pentroller as the Pictroller didn't like the little 8mm coreless motors - either Faulhaber or Nigel Lawton, it was great with all other motors. I really like the Pentroller and use it all the time. The great advantage with the Pictroller was that it eliminated my constantly forgetting to switch between the motor options on the Pentroller.

 

Jerry

 

Thanks Jerry - useful to know. Rather a shame that the Pentroller is not being made these days then.

 

Regards, Andy

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