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Etched loco chassis


Chris Higgs
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At the latest Canterbury Area Group meeting, thanks to Nick, I understood exactly how all the transmission inside the chassis works. As a result, I have ordered more stuff from Shop 3 and I progressed a bit with my Hunslet Austerity chassis.

 

All the gears and muffs are imperial; yes, Nick, I have ordered and received the 14T (bore 1/8") code 3-341, so I do not need to use the stepped muff and all the metric gears (spears for a future project).

 

IMG_0149.jpg IMG_0152.jpg

 

3-362 is the gear set but here is pictured the gear only, without worm

3-110 are stubs, cut from the 75 mm long axle; there are two stubs inserted in the muff which don't touch each other (no short-circuit)

Edited by Valentin
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this is what I was thinking given I can not get a wheel in a muff unless I ream it out first

 

You obviously need a bigger vice. I have no problem pushing them in that way. Turning them to quarter is another matter.

 

For those that don't know how to get them out again, you use a soldering iron and melt the muff off!

 

Chris

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See that bit of swarf that the gear wheel has cut on the muff - it could mean trouble. It might mean the gearwheel is eccentric, or it might be OK. Don't forget to remove it anyway - before the eagle eye of the camera spots it!

At the latest Canterbury Area Group meeting, thanks to Nick, I understood exactly how all the transmission inside the chassis works. As a result, I have ordered more stuff from Shop 3 and I progressed a bit with my Hunslet Austerity chassis.

 

All the gears and muffs are imperial; yes, Nick, I have ordered and received the 14T (bore 1/8") code 3-341, so I do not need to use the stepped muff and all the metric gears (spears for a future project).

 

IMG_0149.jpg IMG_0152.jpg

 

3-362 is the gear set but here is pictured the gear only, without worm

3-110 are stubs, cut from the 75 mm long axle; there are two stubs inserted in the muff which don't touch each other (no short-circuit)

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See that bit of swarf that the gear wheel has cut on the muff - it could mean trouble. It might mean the gearwheel is eccentric, or it might be OK. Don't forget to remove it anyway - before the eagle eye of the camera spots it!

 

Thanks Tim. It's gone. I've removed it together with another one before fixing it inside the frame.

 

IMG_0154.jpg

 

IMG_0155.jpg

 

IMG_0156.jpg

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I've just built my first etched chassis (for the Jinty) and it runs ok and reasonably slowly too provided it's on electrical leads direct to motor (Faulhaber 10/16).

Problem is it's not very happy on the track and keeps stopping if I run it too slowly. When this happens turning up the power does nothing as it requires a slight nudge to restore electrical contact at wheels/track.

I've tried:

  • Running it in on rollers
  • Running it in against the buffer stop
  • Cleaning the tyres
  • Cleaning the track
  • Adding weight
  • Different controllers such as Pentroller, Gaugemaster, old fashioned transformer/rectifier/variable resistance

But nothing seems to help. Any suggestions other than the bin and start again!

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Hi, congratulations on your first chassis. The problem is obviously one of pickup, the most difficult aspect of 2FS loco construction in my experience due to small physical size and lack of mass. This is one area where tender locos, despite the added complexity involved in their construction have a distinct advantage.

A few questions,

* are you testing it with the body on

* have you used any additional means of pickup eg. Simpson springs

*do all the wheels sit squarley on the track - its very easy with an 0-6-0 to have it rocking around the centre axle which plays havoc with pickup.

 

I had a similar problem with my Jinty (Fence Houses chassis) and eventualy solved it by adding very fine conventional wiper pickups - both back and top acting.

Above all, don't give up on it, despite the problems you are having it sounds like it is already much better than my first chassis.

 

Jerry

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Unless you use wires on the axles in generous axle holes to give the chassis a bit of flexibility, it may indeed be that the chassis is not dead flat. In fact on an 0-6-0 it's better to have the middle axle a touch high. The old trick is to put the mechanism on a mirror and look / feel for any gaps or rocks between the glass surface and the wheel tyres. If there are gaps then firmly take hold of each end of the chassis and bend / twist it in the right direction to at least make the middle wheels off the ground (only a gnat's whisker of course). I have done this Uri Geller trick on many chassis, especially Farish 0-6-0s and it helps considerably. If this prospect is too frightening, then determine which wheel set is too low and file out the axle bearings vertically to allow its upward movement to bring it into 'flatness'. This axle should then have two light phosphor bronze springs on it. This adjustment must not be done on the driven wheel, of course.

 

As much weight as possible and seriously polishing the wheel rims is also a good idea.

 

Tim

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Unless you use wires on the axles in generous axle holes to give the chassis a bit of flexibility, it may indeed be that the chassis is not dead flat. In fact on an 0-6-0 it's better to have the middle axle a touch high. The old trick is to put the mechanism on a mirror and look / feel for any gaps or rocks between the glass surface and the wheel tyres. If there are gaps then firmly take hold of each end of the chassis and bend / twist it in the right direction to at least make the middle wheels off the ground (only a gnat's whisker of course). I have done this Uri Geller trick on many chassis, especially Farish 0-6-0s and it helps considerably. If this prospect is too frightening, then determine which wheel set is too low and file out the axle bearings vertically to allow its upward movement to bring it into 'flatness'. This axle should then have two light phosphor bronze springs on it. This adjustment must not be done on the driven wheel, of course.

 

As much weight as possible and seriously polishing the wheel rims is also a good idea.

 

Tim

Axles in generous axle holes - how generous?

It may indeed be that the chassis is not dead flat. In fact on an 0-6-0 it's better to have the middle axle a touch high. - The chassis is dead flat on testing with mirrow and the centre axle by luck is marginally up by a hairs breadth.

This axle should then have two light phosphor bronze springs on it.- Do you mean on the centre slightly raised axle?

This adjustment must not be done on the driven wheel, of course. - sadly the centre axle is the driven axle!

 

And in answer to Jerry's questions,

are you testing it with the body on? - yes on and off makes no difference and I've tried loading it with a large piece of lead sheet wrapped over the loco.

have you used any additional means of pickup eg. Simpson springs? - I've looked up Simpson Springs but cannot find a picture showing exactly what is meant by this.

do all the wheels sit squarley on the track - yes the front and rear ones do but the centre ones are ever so slightly raised

adding very fine conventional wiper pickups - both back and top acting.- Please can you point me to a diagram or picture so I know what you mean exactly. (sorry to be dense!)

Edited by bogieman
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Axles in generous axle holes - how generous?

It may indeed be that the chassis is not dead flat. In fact on an 0-6-0 it's better to have the middle axle a touch high. - The chassis is dead flat on testing with mirrow and the centre axle by luck is marginally up by a hairs breadth.

This axle should then have two light phosphor bronze springs on it.- Do you mean on the centre slightly raised axle?

This adjustment must not be done on the driven wheel, of course. - sadly the centre axle is the driven axle!

 

And in answer to Jerry's questions,

are you testing it with the body on? - yes on and off makes no difference and I've tried loading it with a large piece of lead sheet wrapped over the loco.

have you used any additional means of pickup eg. Simpson springs? - I've looked up Simpson Springs but cannot find a picture showing exactly what is meant by this.

do all the wheels sit squarley on the track - yes the front and rear ones do but the centre ones are ever so slightly raised

adding very fine conventional wiper pickups - both back and top acting.- Please can you point me to a diagram or picture so I know what you mean exactly. (sorry to be dense!)

 

The recommended size for axle holes when using 'SImpson springs' is 1.6mm. These are nothing more than pieces of very thin phosper-bronze wire which bear onto the axles in the gap between the inside of the frames and the muffs and act as springs/pickups - in reality mostly the latter. Your chassis already has extra holes etched into it to locate the ends of these. You can buy such wire at Eileens emporium of use N gauge coupler springs straightened out.

 

The coarseness of the gears used in the design mean it's OK to have a little bit of play even on the driven axle in this case.

 

But I would not totally rule out the possibility of other issues. Running on wires attached to the motor, double check that it really rotates smoothly without any tight spots in the rotation. Causes for this could be quartering issues or irregularity in the gear teeth. It's possible these might not stop the loco when running on such a test, but will when it has the extra effort of moving its own weight along the track.

 

Chris

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The recommended size for axle holes when using 'SImpson springs' is 1.6mm. These are nothing more than pieces of very thin phosper-bronze wire which bear onto the axles in the gap between the inside of the frames and the muffs and act as springs/pickups - in reality mostly the latter. Your chassis already has extra holes etched into it to locate the ends of these. You can buy such wire at Eileens emporium of use N gauge coupler springs straightened out.

 

The coarseness of the gears used in the design mean it's OK to have a little bit of play even on the driven axle in this case.

 

But I would not totally rule out the possibility of other issues. Running on wires attached to the motor, double check that it really rotates smoothly without any tight spots in the rotation. Causes for this could be quartering issues or irregularity in the gear teeth. It's possible these might not stop the loco when running on such a test, but will when it has the extra effort of moving its own weight along the track.

 

Chris

Thanks for that Chris yes I had noticed the extra holes (talking of extra holes what are the holes for in the etching of the springs in the 57xx?)

  • Do they need to be on all three axles?
  • I've used all100DP gears and not 64DP but assume they could still be used
  • I was reluctant to open up the holes to 1.6mm when it ran perfectly well at 1.5mm
  • Yes it runs fine on wires connected direct to motor at very slow speeds and with hardly a flicker from a milliammeter needle as drivers slowly rotate.

After running it in some more on a little shuttle unit the pickup problem now comes down to just the front pair of drivers which is strange given that the centre drivers are up a hairsbreadth.

 

I found your coupling rods so accurate that when the second side slides onto crankpins easily I know the quartering is correct. That why I preferred no slop in the axle bearings or the crankpins holes.

 

And I'm reluctant to take it apart now that all the brake gear etc is on and everything painted. And fortunately it is getting better with running in on the shuttle rather than on rollers or against the buffers.

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Thanks for that Chris yes I had noticed the extra holes (talking of extra holes what are the holes for in the etching of the springs in the 57xx?)

  • Do they need to be on all three axles?
  • I've used all100DP gears and not 64DP but assume they could still be used
  • I was reluctant to open up the holes to 1.6mm when it ran perfectly well at 1.5mm
  • Yes it runs fine on wires connected direct to motor at very slow speeds and with hardly a flicker from a milliammeter needle as drivers slowly rotate.

After running it in some more on a little shuttle unit the pickup problem now comes down to just the front pair of drivers which is strange given that the centre drivers are up a hairsbreadth.

 

I found your coupling rods so accurate that when the second side slides onto crankpins easily I know the quartering is correct. That why I preferred no slop in the axle bearings or the crankpins holes.

 

And I'm reluctant to take it apart now that all the brake gear etc is on and everything painted. And fortunately it is getting better with running in on the shuttle rather than on rollers or against the buffers.

 

Common sense says that introducing a bit of slop on 100DP spur gears could be more problematic than 64DP/M0.4.

 

I would have thought either springing only the centre axle or all six would be stable combinations. Never spring the outside ones without the centre one, that would create the dreaded rocking action.

 

You could try adding the springs just as pickups, without enlarging the holes. Although it has now been done for so many years, it is questionable as to using bearings as pickups, which is what the split frame design does, is totally wise, given that oil might get in there.

 

Which combination of 100DP gears did you use? None of the available combinations seem to match the mesh centres used for the M0.4 gears, so I think you took a bit of a risk there?

 

Chris

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Common sense says that introducing a bit of slop on 100DP spur gears could be more problematic than 64DP/M0.4.

 

I would have thought either springing only the centre axle or all six would be stable combinations. Never spring the outside ones without the centre one, that would create the dreaded rocking action.

 

You could try adding the springs just as pickups, without enlarging the holes. Although it has now been done for so many years, it is questionable as to using bearings as pickups, which is what the split frame design does, is totally wise, given that oil might get in there.

 

Which combination of 100DP gears did you use? None of the available combinations seem to match the mesh centres used for the M0.4 gears, so I think you took a bit of a risk there?

 

Chris

Well Chris I'm no engineer so you can perfectly well say I'm mad or stupid and I won't mind but according to the gear meshing tables the centres for gears are quoted as follows:

 

64DP 14T to 18T = 6.35mm

M0.4 14T to 18T = 6.40mm

100DP 18T to 31T = 6.35mm

100DP 20T to 30T = 6.35mm

 

I tried the 3rd and 4th options and they both work perfectly well with apparantly good meshing but decided on 18/31 and it has survived testing under load for three days continuous running on a shuttle circuit.

 

My rationale is that 100DP gives you a greater number of ratio options and ability to have a bigger ratio thus enabling the loco to run more slowly and with better control for shunting. Which is what I prefer.

 

Tony

Edited by bogieman
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Well Chris I'm no engineer so you can perfectly well say I'm mad or stupid and I won't mind but according to the gear meshing tables the centres for gears are quoted as follows:

 

64DP 14T to 18T = 6.35mm

M0.4 14T to 18T = 6.40mm

100DP 18T to 31T = 6.35mm

100DP 20T to 30T = 6.35mm

 

I tried the 3rd and 4th options and they both work perfectly well with apparantly good meshing but decided on 18/31 and it has survived testing under load for three days continuous running on a shuttle circuit.

 

My rationale is that 100DP gives you a greater number of ratio options and ability to have a bigger ratio thus enabling the loco to run more slowly and with better control for shunting. Which is what I prefer.

 

Tony

 

Tony,

 

I don't know which tables you were following. The 100DP tooth counts you list are not standard shop items.

 

These centres come from the 2mm website "gear mesh calculator", which I wrote and am reasonably certain is accurate.

 

64DP 14T to 18T, theoretical perfect mesh 6.35mm, with running clearnances = 6.48mm

M0.4 14T to 18T, theoretical perfect mesh 6.40mm, with running clearance = 6.53mm

100DP 18T to 31T, theoretical perfect mesh = 6.22mm, with running clearance = 6.35mm

100DP 20T to 30T, theoretical perfect mesh = 6.35mm with running clearance = 6.48mm

 

Gears, gear mesh calculations and related items are discussed in a pair of articles by Denys Brownlee and Henk Oversloot in a 1990's 2mm Magazine, which is in the archive CD set.

 

 

- Nigel

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Tony,

 

I don't know which tables you were following. The 100DP tooth counts you list are not standard shop items.

 

These centres come from the 2mm website "gear mesh calculator", which I wrote and am reasonably certain is accurate.

 

64DP 14T to 18T, theoretical perfect mesh 6.35mm, with running clearnances = 6.48mm

M0.4 14T to 18T, theoretical perfect mesh 6.40mm, with running clearance = 6.53mm

100DP 18T to 31T, theoretical perfect mesh = 6.22mm, with running clearance = 6.35mm

100DP 20T to 30T, theoretical perfect mesh = 6.35mm with running clearance = 6.48mm

 

Gears, gear mesh calculations and related items are discussed in a pair of articles by Denys Brownlee and Henk Oversloot in a 1990's 2mm Magazine, which is in the archive CD set.

 

 

- Nigel

The figures I used are from a gear mesh calculator on the internet, don't remember now from where, but I copied all the figures out and kept them as a Excel file for all the 100DP gears readily available in small sizes (shop ones are in bold) i.e. 14 15 18 20 21 24 28 30 31 34 37 39 42 44 45

52

I did check them against various books and other internet sources as well as working them out as best I could mathematically to check them. However I'm no mathmetician or engineer so I could have slipped up on one or two. The figures for the 64DP amd M0.4 and 100DP shop available ones certainly match the figures given in the Year Book tables.

And you're right I haven't just stuck with the 2mm SA shop tooth sizes as I have a small stock of other tooth sizes also from places like Branchlines or Ultrascale so that I can play about with gear spacings and ratios.

Certainly when I work with the figures in my composite chart things seem to run ok which for a non engineer is to me the ultimate test.

Edited by bogieman
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These centres come from the 2mm website "gear mesh calculator", which I wrote and am reasonably certain is accurate.

 

64DP 14T to 18T, theoretical perfect mesh 6.35mm, with running clearnances = 6.48mm

M0.4 14T to 18T, theoretical perfect mesh 6.40mm, with running clearance = 6.53mm

100DP 18T to 31T, theoretical perfect mesh = 6.22mm, with running clearance = 6.35mm

100DP 20T to 30T, theoretical perfect mesh = 6.35mm with running clearance = 6.48mm

 

Gears, gear mesh calculations and related items are discussed in a pair of articles by Denys Brownlee and Henk Oversloot in a 1990's 2mm Magazine, which is in the archive CD set.

 

 

- Nigel

 

The chassis are designed with the M0.4 figures with slack so are 6.53mm in this case.

 

So 20:30 100DP should work fine, but as pointed out you do have to know where to buy them.

 

I'm going to be using the M0.3 gears for the design of the next batch of chassis as it gives more available options and in most cases a slightly higher gear reduction.

 

100DP 18T to 31T = 6.35mm

 

I think this should be the spacing for 19T to 31T. The way it works is that for gears of the same pitch, having the same total number of teeth on the two gears should give the same total spacing. So 19:31 and 20:30 should be the same spacing.

 

Chris

Edited by Chris Higgs
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Just stripped mine down, as I wasn't satisfied with its performance. Fitted Simpson pickups in enlarged axle holes as recommended. Having the removable motor and gear was a boon.

 

Running transformed, hoping to sneak it onto a 2mm layout in the near future....

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Just stripped mine down, as I wasn't satisfied with its performance. Fitted Simpson pickups in enlarged axle holes as recommended. Having the removable motor and gear was a boon.

 

Running transformed, hoping to sneak it onto a 2mm layout in the near future....

Could I ask

("enlarged axle holes as recommended".) how large?

("I wasn't satisfied with its performance.") was that speed, pulling power, ultra slow speed or reliability at not stopping due to loss of electrical contact?

("enlarged axle holes") was that all axles, front and rear or just centre?

Thanks

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Axle holes reamed to 1.5mm then carefully enlarged by twisting a 1.6mm drill in all three axle holes. Then the Simpson springs put on. There is a sheet about it on the VAG, plus an article in the magazine. Jerry Clifford (Queensquare) put me on to it.

 

Electrical pickup was the problem, it ran smoothly enough. Haulage power not ascertained as I don't have any other stock!

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Axle holes reamed to 1.5mm then carefully enlarged by twisting a 1.6mm drill in all three axle holes. Then the Simpson springs put on. There is a sheet about it on the VAG, plus an article in the magazine. Jerry Clifford (Queensquare) put me on to it.

 

Electrical pickup was the problem, it ran smoothly enough. Haulage power not ascertained as I don't have any other stock!

Thanks for that I'll see if I can find the sheet on the YAG I must have missed it. Will also look up article.

The problem I foresee is quartering. Dead easy when there's no slop in axles as the etched rods are so accurate. But add in the axle slop and you're into a completely different game with possibility of jerking wheels as coupling rods "rotate" if quartering not spot on and you've lost one of the ways of it happening naturally. Just a thought.

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Thanks for that I'll see if I can find the sheet on the YAG I must have missed it. Will also look up article.

The problem I foresee is quartering. Dead easy when there's no slop in axles as the etched rods are so accurate. But add in the axle slop and you're into a completely different game with possibility of jerking wheels as coupling rods "rotate" if quartering not spot on and you've lost one of the ways of it happening naturally. Just a thought.

 

I think you are over emphasising the amount of play with the term slop, we are talking a tiny amount from 1.5 to 1.6 mm - think of it as a working clearence. It has no impact on quartering at all and makes all the difference to the running of the chassis.

 

Jerry

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Thanks for that I'll see if I can find the sheet on the YAG I must have missed it. Will also look up article.

The problem I foresee is quartering. Dead easy when there's no slop in axles as the etched rods are so accurate. But add in the axle slop and you're into a completely different game with possibility of jerking wheels as coupling rods "rotate" if quartering not spot on and you've lost one of the ways of it happening naturally. Just a thought.

 

Quartering is no more difficult. I think it actually makes it easier because there is a fraction of room for some error. Electrical pick up is much improved on the one loco I have that I fitted springs to compared with others without.

 

Another thing that I have started doing is polishing the wheels based on the idea that clean bright shiny things conduct better. I put the wheels in the lathe and use very fine abrasive paper followed by Autosol on a cotton bud but I am sure there are alternatives that may be better.

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Thanks for that I'll see if I can find the sheet on the YAG I must have missed it. Will also look up article.

The problem I foresee is quartering. Dead easy when there's no slop in axles as the etched rods are so accurate. But add in the axle slop and you're into a completely different game with possibility of jerking wheels as coupling rods "rotate" if quartering not spot on and you've lost one of the ways of it happening naturally. Just a thought.

I don't see a problem, as you're quartering the wheelset against against the other wheelset, not relative to the chassis. Therefore any slop in the axle holes (and we are talking about 0.1mm here) won't affect the quartering.

 

 

I don't have a quartering tool, but I do have a lathe, a few minutes work produced this tool which is mounted in the tailstock and a dividing/indexing tool (Unimat). A slot is cut in it for the crankpin to fit through, you can just see the slot on the right hand one (right hand leads). The tailstock chuck is given bias with the key to ensure it stays in the same place. Using the tailstock wheel, I can push the wheels towards each other, checking with the back to back gauge as it advances.

post-7177-0-31377900-1341495824.jpg

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I don't see a problem, as you're quartering the wheelset against against the other wheelset, not relative to the chassis. Therefore any slop in the axle holes (and we are talking about 0.1mm here) won't affect the quartering.

 

 

I don't have a quartering tool, but I do have a lathe, a few minutes work produced this tool which is mounted in the tailstock and a dividing/indexing tool (Unimat). A slot is cut in it for the crankpin to fit through, you can just see the slot on the right hand one (right hand leads). The tailstock chuck is given bias with the key to ensure it stays in the same place. Using the tailstock wheel, I can push the wheels towards each other, checking with the back to back gauge as it advances.

post-7177-0-31377900-1341495824.jpg

Neat! I'm not that talented an engineer though. I presume you have to make a set for each diameter of driver?

My first attempt at Jinty conversion with fixed chassis and no "slop" runs down to 15secs for 10 inches which I make about 6 scale mph. How much will a "sloppy" one run down to? Walking pace or less I guess and then I'll be depressed because I don't really want to unsolder the crankpins and brakegear now! Maybe I'll just leave it in a siding or sell it and start again.

And I like Richards's polishing idea particularly as you have to do something similar to remove the paint from the tyres if you spray paint the drivers.

Edited by bogieman
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Thanks for that I'll see if I can find the sheet on the YAG I must have missed it. Will also look up article.

The problem I foresee is quartering. Dead easy when there's no slop in axles as the etched rods are so accurate. But add in the axle slop and you're into a completely different game with possibility of jerking wheels as coupling rods "rotate" if quartering not spot on and you've lost one of the ways of it happening naturally. Just a thought.

 

All I can say is that the senior 2mm modellers who use this technique do not seem to have any problems. If indeed you are quartering the wheels such that "when the run, that's OK" you might see more issues. But really you should be quartering the wheels such that they are all at 90', not just close enough to run.

 

Lathe solution is rather clever but to be honest even if you own a lathe the Association quartering jig is quicker to set up. And certainly cheaper if you don't.

 

Chris

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I expect the jig is quicker to set up, but it is £35, and I had the lathe. One thing the jig will have is repeatability - so if only one wheelset needs setting, that can be done with the assurance that it will be the same as the others.

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