4mm OO 0-6-0 chassis, which axle to drive ?

[Blacque Jacque]

Hi folks,

 

I'm working on my first ever loco kit; a Judith Edge Sentinel 0-6-0 4mm built for OO gauge. The body is coming along nicely but the chassis was a different matter. After much reading on here of tips from the experienced kit builders I purchased a copy of Iain Rice's book on etched chassis construction. This led me to completely strip & rebuild the chassis with the aid of a jig made from 1/8 silver steel & aluminium angle.

 

The chassis now runs freely without rods & sits square on the rails, even though I have built it as a rigid chassis.

 

Power is from a Mashima 1220 via a Branchlines 80:1 gearbox plus a small flywheel. Using these components, the optimal layout seems to be to power the middle axle rather than the more traditional, (as I understand it), rear axle. This means the motor & it's flywheel are nicely contained within the bonnet at the expense of the gearbox edges intruding a little into the cab.

 

I went with the larger motor & gearbox ratio to allow me to add weight & get reasonable haulage power without straining a 10xx motor and keep speeds down to something reasonably scale.

 

I can live with the cab intrusion which can be mostly concealed with the control desk anyway, but is there anything fundamentally wrong with powering the middle axle ? To my mind it should potentially make it easier as it should behave as "two 4 coupled chassis' sharing an axle", therefore any slack will not be compounded at the ends.

 

Would I need to articulate the rods or keep them rigid ?

 

Thoughts from those with more experience much appreciated.

[Miss Prism]

There's nothing wrong with powering the middle axle.

 

There is no need for articulated rods on a rigid chassis.

[RedgateModels]

oooh, not strictly true IMHO. IF you want your loco to go round R2 curves (yes there are still some of us ) then having articulated rods will help with the side-play no end.

 

I'd always try to drive off the centre axle, but wouldn't lose sleep if I couldn't. The 2-8-2 runs fine driving off the rearmost axle of four

[Miss Prism]

oooh, not strictly true IMHO. IF you want your loco to go round R2 curves (yes there are still some of us ) then having articulated rods will help with the side-play no end.

 

That's a fair point. I was thinking of the Sentinel in question rather than the general case.

[Blacque Jacque]

Ah yes, I hadn't considered tight curves (or at all for that matter). Some of the yard points it's expected to negotiate will be pretty sharp curves (Peco Code 75)

 

My first concern is to make sure it goes in a straight line without binding, lurching, wobbling or otherwise qualifying for The Ministry of Silly Walks.

 

Dividing the rods is a good idea from the outset I think, as it should allow me to address any issues at either end without affecting the other.

[Kenton]

My first priority would be to hide the gearbox and motor so I would have ditched the branchines. This Sentinel works really well with a High Level gearbox and a Mashima 1216 with no straining. I would not increase the size of motor or gearbox simply to add weight - I would rather use the space for some additional lead (as required for most etched brass kits).

 

But I guess driving the centre wheels is not out of the question and is really down to how much you can put up with in the cab.

[Adam]

I'd agree with Kenton here, a High Level gearbox will fit in this prototype with, probably, a 1224 or 1220, the latter with a flywheel. I have an 0-4-0 version with 108:1 reduction and an 0-6-0 Thomas Hill on the bench which, although slightly bigger, has bags of space for such an arrangement. There's also loads of space for weight on these, for example between the cosmetic outside frames and the sudd skirts do the space in the bonnet is largely irrelevant. I'll try to remember to post some progress pictures at the weekend if that helps?

 

Adam

[Blacque Jacque]

Adam, yes photos would be very much appreciated, thank you.

 

I have already begun shaping some lumps of lead, as you say between the side skirts & inner frames, plus a block which fills the fuel tank (at least that's what I think it is), and there are still several areas where more can be added,eg; the ends of the chassis and so on.

 

I may remove the block in the fuel tank to fit a DCC decoder,or I may fit it directly in the chassis. A good quality N gauge one should be fine, although I haven't decided what as yet.

 

Kenton, we may be at crossed purposes here; My choice of the 1220 was to allow it to move a heavier loco with ease, thereby giving me scope to add sufficient weight in the form of lead. I wasn't implying the larger motor was for ballast itself, apologies if I worded things poorly. Fitting a 10xx motor would not have freed up much space for lead within the bonnet & would make it all the more difficult to get both motor & lead in that space.

 

Given the choice I would tend to err on the side of a larger motor that could exceed the available grip, rather than a lesser one that may stall, although in this particular case I suspect neither motor would stall even at the buffer stop.

[Adam]

Here we go. It doesn't show all that much and may not be wholly applicable to the Sentinel since I think this has a slightly longer cab, but the gearbox shown here provides 108:1 reduction and allows space for a small flywheel on the end of a 1220. Again, I suspect that the Sentinel might not quite have the room for this and, if you're using DCC, I am unsure (since I do not) whether that would have any benefit. With 108:1 it's marginal in any case - though it is noticeable on dad's YEC 0-4-0 and the relatively high revs of a 1220 should show more of a benefit. The advantage of Judith Edge kits is the scale CAD drawing in the instructions. This makes it very easy to use the High Level gearbox planner to assess which gearbox to use. It can be found here: http://chrisgibbon.com/webftp/gearboxplanner.pdf

 

My 0-4-0 Sentinel has a 'Hump Shunter' in is which requires only a small notch in the cab front to fit (note that you can order this with a 2mm final drive gear) and the motor mounted at an angle. The Thomas Hill uses a 'Load Hauler'. See below:

 

 

Hope that helps?

 

Adam

[Blacque Jacque]

Thanks Adam.

 

Judging by the height & location fore & aft of that gearbox, it too would intrude in the Sentinel cab. I suspect this would be the case with almost any gearbox when used to power the centre axle.

 

I seem to have mislaid my instructions in the last house move

[Adam]

No problem. The intrusion is pretty minor and, in the case of the Thomas Hill, non-existent in a visible sense - what little filing has been required is off the base of the bonnet. If you've misplaced the instructions I'm sure that an email to Mike and Judith (or a PM here) will get you another copy. Mike is very helpful in that respect.

 

Adam

[Michael Edge]

Now that you have the instructions again you will see that it is designed to drive on the leading axle with the motor in much the same position as the engine in the full size loco. It makes absolutely no difference which axle you drive on for a rod drive frame, remember most full size diesel mechanicals are driven from outside the wheelbase on the jack cranks.

Michael Edge

[Blacque Jacque]

Thank you Michael, both for the instructions, and your guidance here, and thank you to everyone else who has posted.

 

It seems I've made several mistakes with this chassis, but hopefully I will still end up with something that runs reasonably well despite this.

 

Once completed, I suppose I will need to buy another kit to "improve my skills", I'm not sure the missus will be convinced by that though

[Kenton]

Kenton, we may be at crossed purposes here; My choice of the 1220 was to allow it to move a heavier loco with ease, thereby giving me scope to add sufficient weight in the form of lead. I wasn't implying the larger motor was for ballast itself, apologies if I worded things poorly. Fitting a 10xx motor would not have freed up much space for lead within the bonnet & would make it all the more difficult to get both motor & lead in that space.

 

Given the choice I would tend to err on the side of a larger motor that could exceed the available grip, rather than a lesser one that may stall, although in this particular case I suspect neither motor would stall even at the buffer stop.

 

I'm not sure it was quite so crossed. I find that the 1220 offers nothing additional in terms of traction on an 0-6-0, just more size and a tiny bit of weight. The weight is easily offset by lead in the space gained. I wouldn't use a 12xx except on a larger/heavier loco (eg whitemetal). What gives traction is gearing and weight and there is plenty of room in the Sentinel for lead (block & shot) and a 60:1 or 108:1 is I think essential for what should be a slow moving engine.