Etched loco chassis

[richbrummitt]

If they are in situ and painted, then yes.

 

They are neither painted or ballasted, sorry.

[Thos]

^{Suggestion to mods}

^{This thread seems to have moved to buffers - could it be split and tidied?}

[queensquare]

^{Suggestion to mods}

^{This thread seems to have moved to buffers - could it be split and tidied?}

 

The thread does not need splitting. Chris asked for photos of assembled Association etched chassis and also mentioned he would like some of the buffers as well. Its a related diversion and does not justify a new thread.

I,m sure the mods have better things to worry about.

 

Jerry

[richbrummitt]

I'll get it back on topic later, I promise. I have some further progress on 2284 to upload...

[richbrummitt]

As promised yesterday, some progress:

 

 

2284 is sitting on her chassis after the removal of some bits of the running plate highlighted below in red and Chris explaining how to get the brass lump out of the firebox, by removing the screw hidden by the smoke box door. The body isn't fixed back to the running plate yet, hence the slight gap visible in the above picture, because I haven't securing the nuts for the chassis fixing points yet.

 

 

I'm wondering how much more of the area contained by the blue rectangle was not present on the prototype? Some trawling of photographs will be necessary to check PECO's work

 

Here is the underside of the tender that 2284 will pull until the ROD tender that I am working on is ready for her.

 

 

The pick up strips and draw bar boss have been cut away here, along with the rear coupler pocket, to allow the body to sit down on the chassis.

 

More soon...

Edited October 13, 2012 by richbrummitt

[Chris Higgs]

I'm wondering how much more of the area contained by the blue rectangle was not present on the prototype? Some trawling of photographs will be necessary to check PECO's work

 

I'm pretty certain that the space between the frames under the boiler between firebox and smokebox will be open, with the inside valvegear showing.

 

Chris

[richbrummitt]

 

 

I'm pretty certain that the space between the frames under the boiler between firebox and smokebox will be open, with the inside valvegear showing.

 

Chris

 

I am too. I haven't seen a photo confirming it yet but that is how I remember all the GWR engines I ever looked at, and the JLTRT kit is like this. From a practical perspective it doesn't make any sense to unecessarily cover up parts that you need to access on a regular basis.

Edited October 13, 2012 by richbrummitt

[justin1985]

After a few hours work over the weekend I've made up my jinty chassis to the stage of rolling with wheels but it doesn't run as freely as it might. I had a bit of a false start after forgetting to file down the bearings projecting through the outside of the frames, meaning when I fitted and quartered the wheels they rubbed. Second set of muffs now and the wheels all spin freely independently. However, putting the intended connecting rods on results in it rolling smoothly with finger pressure applied from above, but not so freely that it will roll under its own weight. I reamed the holes slightly, but the fit is exact. I used the Association quartering jig so I assume the quartering must be spot on. The back to backs seem correct too - bobbin gauge is a snug fit. Should I ream the rods much further? Or is there anything else to check?

 

After a pretty comprehensive failure of my Fence houses J72 build (couldn't get the quartering right, ended up opening up the connecting rod holes too much, and eventually bending both the frames and one wheel set). I'm reluctant to open things up too much!

 

Justin

[Kris]

I'm pretty certain that the space between the frames under the boiler between firebox and smokebox will be open, with the inside valvegear showing.

 

It is open, unfortunately the the photos I have are not quite as clear as they could be to show this. I'll keep looking to see if I can find a better one in my collection.

[Nigelcliffe]

However, putting the intended connecting rods on results in it rolling smoothly with finger pressure applied from above, but not so freely that it will roll under its own weight. I reamed the holes slightly, but the fit is exact. I used the Association quartering jig so I assume the quartering must be spot on. The back to backs seem correct too - bobbin gauge is a snug fit. Should I ream the rods much further? Or is there anything else to check?

 

 

Its time for systematic checking to find where the tight spot may be.

 

The cause could be rod holes needing slightly enlarging, or it might be a bent (or mis-aligned) crankpin in a wheel. The latter isn't common, but it is also not totally unknown in 2mm wheel production.

 

Rod setting is covered in an article in the April 1995 magazine (backnumber archive!). I think its repeated in one of the booklets, possible the split-frame chassis booklet. The basics are to remove the rods, turn them over and refit so the loco is a 2-4-0, study whether there is a tight spot with the 2-4-0. Now repeat again as a 0-4-2.

I'd expect a small enlargement of a rod hole is what's needed. But, which direction it needs enlarging is important.

 

 

- Nigel

[richbrummitt]

It is open, unfortunately the the photos I have are not quite as clear as they could be to show this. I'll keep looking to see if I can find a better one in my collection.

 

Kris, I found one and it's been chopped out. Thanks for looking.

 

Its time for systematic checking to find where the tight spot may be...

...The basics are to remove the rods, turn them over and refit so the loco is a 2-4-0, study whether there is a tight spot with the 2-4-0. Now repeat again as a 0-4-2.

 

I don't have a quartering jig, but get satisfactory results working from a four coupled chassis and then flipping the rods over and matching the third pairs of wheels to the first two, which then remain untouched. Have you used the new wheel quartering jig? I've used the old fold up V type but this will only get you close in my experience.

 

If it's really close but not quite I would open up the holes in the coupling rods, but not to more than 0.6mm in diameter. I drill them out to avoid going larger than I intended with a broach or file. It sounds like you've discovered yourself about the perils of opening out the holes too much

[justin1985]

Many thanks Nigel and Rich for your advice. Methodical is the way forward! I did a little fiddling at lunchtime (working from home has mixed blessings!)

 

I don't have a quartering jig, but get satisfactory results working from a four coupled chassis and then flipping the rods over and matching the third pairs of wheels to the first two, which then remain untouched. Have you used the new wheel quartering jig? I've used the old fold up V type but this will only get you close in my experience.

 

It is the new Association wheel quartering jig - this should give consistent quartering to a high degree of accuracy, no?

 

I noticed that I had missed one frame bush when filing them back, so out came the soldering iron to melt off another gear muff.

 

With the middle axle out, I tried the rods back on only the front and rear, and it seemed to run very freely indeed.

 

 

Once back together things were slightly better. Testing various combinations with the rods, it seems everything is fine with the left hand set on as intended, but things go stiff whenever the right hand rod is introduced.

 

I imagine this means the central hole on the right hand rod needs a bit of reaming? Or there might be a problem with the wheel itself?

[Izzy]

Could I suggest that you check that the crankpins are at right angles to the wheels. I have found that they can easily shift out of true and cause quartering issues.

 

Izzy

[Nigelcliffe]

 

 

Once back together things were slightly better. Testing various combinations with the rods, it seems everything is fine with the left hand set on as intended, but things go stiff whenever the right hand rod is introduced.

 

I imagine this means the central hole on the right hand rod needs a bit of reaming? Or there might be a problem with the wheel itself?

 

Could be anything on the RH side. So, do it methodically, turn the RH rod over and fit the rear crank hole over centre axle, centre hole on rear axle. Study what happens. Now put front crank hole on centre axle, centre hole on front axle. Study again. Then decide where the tight spot lies. It really is worth getting the article mentioned !

 

Before you cut anything check the crankpins very carefully for perpendicular to wheel and, if you can, crank throw.

 

 

- Nigel

[Tim V]

Try the RH coupling rod on the LH side and vice versa.

 

That way you will reduce the variables. Also compare the coupling rod's length.

[renovater 1]

Hi, i have been following this thread, very good work, there is though a point i would like to make concerning the Faulhaber and in general all coreless motors. To use these types of motors with a worm gear is not good practise, what you will find is that they will work perfectly in one direction but will be slightly noisy in the other, this is because the worm will be trying to pull the motor axle away from it's natural position and will generate interference around the commutater leading to the eventual distruction of the motor making it useless. To avoid this and when there really is no alternative than a coreless motor you must have a thrust bearing in between the motor and the worm, but what is most important is to ensure that when setting up the position of the worm and it's thrust bearing in relation to the motor this shoud be done with motor axle in it's natural position and not working against itself. In other words the motor axle and the worm shoud not be able to move backwards and forwards away from where it was intended, i hope i haven't confused anyone, it's just to make sure that your expensive coreless motor's last longer, bye.

Edited October 21, 2012 by renovater 1

[Chris Higgs]

Hi, i have been following this thread, very good work, there is though a point i would like to make concerning the Faulhaber and in general all coreless motors. To use these types of motors with a worm gear is not good practise, what you will find is that they will work perfectly in one direction but will be slightly noisy in the other, this is because the worm will be trying to pull the motor axle away from it's natural position and will generate interference around the commutater leading to the eventual distruction of the motor making it useless. To avoid this and when there really is no alternative than a coreless motor you must have a thrust bearing in between the motor and the worm, but what is most important is to ensure that when setting up the position of the worm and it's thrust bearing in relation to the motor this shoud be done with motor axle in it's natural position and not working against itself. In other words the motor axle and the worm shoud not be able to move backwards and forwards away from where it was intended, i hope i haven't confused anyone, it's just to make sure that your expensive coreless motor's last longer, bye.

 

Hmm, yes OK, we have heard this as the conventional line, but there are rather a lot of 2mm models out there that have been powered for years and years using direct drive from coreless motors without adverse effect. Could be that they don't actually do many hours running, spending most of their time in boxes, or perhaps the smaller forces involved in such light models do not produce that much stress.

 

Chris

[renovater 1]

Hmm, yes OK, we have heard this as the conventional line, but there are rather a lot of 2mm models out there that have been powered for years and years using direct drive from coreless motors without adverse effect. Could be that they don't actually do many hours running, spending most of their time in boxes, or perhaps the smaller forces involved in such light models do not produce that much stress.

 

Chris

..I agree about the weight factor and to contradict what i have said i have seen on the net a known German precision locomotive site using this system in 1/87, but then again they may have deep pockets ? This was the reason why the portescap gearbox was designed as it was to avoid this problem of thrust on the motor, to insert a thrust washer or shouldered bearings to protect the motor shoudn't be too hard even in your scale, the thing is these motors don't give you a second chance and they cost a lot. One of the best motors on the market for this type of gearbox has to be the Mashima, for price and all round reliability, save the coreless motors for a gearbox without worm. At the end of the day the choice is yours, but it pays to be wary. Edited October 21, 2012 by renovater 1

[Nigelcliffe]

As Chris says, theory tells us about thrust bearings or other couplings between worm and motor. Practise tells me that in small locos it doesn't matter. My DY1 has done a fair amount of running in the ten or so years since it was built, though it doesn't do Copenhagen Fields mileages. The DY1 is on its original Faulhaber motor, worm direct on motor shaft. Other locos have similar arrangement but fewer years running.

 

- Nigel

[CF MRC]

I put a worm directly onto the motor shaft of Denys Brownlee's N2, which has run hundreds of miles on Copenhagen Fields. However, this motor is a Maxon and I suspect they are a little more heavily engineered than the Portescap type. The worm is actually on a motor shaft extension with a bearing at the far end, but tightly controlled for end float. It replaced a nasty Sagami motor many years ago.

 

More recently I remotored a Farish V2 with an almost direct replacement with a Maxon motor direct onto the worm: it made the engine much more controllable and allowed the hideous skirts to be filleted. This hasn't yet done many miles, but I suspect will be OK.

 

Tim

[Horsetan]

Maxons are certainly quite strong. I have one which is a near-direct replacement for the Escap 1616. The kind of momentum it can generate from 9 volts is quite frightening.

Edited October 29, 2012 by Horsetan

[Valentin]

I am building the 2mm Association Replacement Chassis for the Graham Farish LMS 3F (Jinty) 0-6-0T locomotive. Before fitting the front PCB spacer I have checked it for short-circuits ant the resistance, on the 200 Mohms scale was infinite. Then I soldered it to the frames, removed the frames from the jig:

 

 

 

and checked the resistance again: 1.6 Mohms:

 

 

Is this correct?

Edited December 9, 2012 by Valentin

[Valentin]

After drilling the wholes for the screws I've removed the guiding tabs and now the resistance is infinite.

 

[Chris Higgs]

After drilling the wholes for the screws I've removed the guiding tabs and now the resistance is infinite.

 

 

My guess is that it was down to some residual flux from the soldering.

 

Chris

[SteveBedding]

Season’s greetings to all,

 

I'm finally about to get my act together and start on one of these replacement chassis and have been reviewing all the thread and posts to get everything clear in my mind before starting to wave the iron about... (…possibly a last attempt at procrastination, but it really is the last excuse!)

 

I'm happy with all of the general principles of constructing these replacement chassis, but I do have 2 questions on the fitting of the wheel bearings:

1. I always thought it was normal practice to file the wheel bearing flush with the outside surface of the frame - I notice that this does not seem to have been done by people making these chassis kits - therefore is filing flush necessary?
2. When fitting Simpson Springs, I thought I'd seen a picture (somewhere online?) where the top half of the inside of the bearing has been filed away to allow the PB wire greater space to rest on the axle without interfering with the muff? Is this a good idea and can anyone think where I may have got this idea from?

Any suggestions and comments/observations appreciated

 

Cheers