7mm Mickoo's Commercial Workbench

[Dave Holt]

I'm intrigued by the suspension arrangements described. From an engineering point of view, i would have thought it better to have a fixed front axle and bogie central pivot (to give 3 point support over the maximum length) and have the driven axle sprung, in between. Actually, I would have compensated the two driving axles on twin beams and had the bogie pivot as the third fixed point, but there again, I'm working in P4, where suspension might be more critical.
Pick-up from only the driving wheels but using DCC stay alive to cover any supply interruption, is a useful idea I shall bear in mind for a future project (a 4-4-2 tank).
Dave.

 

[mickoo]

I'm intrigued by the suspension arrangements described. From an engineering point of view, i would have thought it better to have a fixed front axle and bogie central pivot (to give 3 point support over the maximum length) and have the driven axle sprung, in between. Actually, I would have compensated the two driving axles on twin beams and had the bogie pivot as the third fixed point, but there again, I'm working in P4, where suspension might be more critical.
Pick-up from only the driving wheels but using DCC stay alive to cover any supply interruption, is a useful idea I shall bear in mind for a future project (a 4-4-2 tank).
Dave.

Would you do the same for a 4-6-0 or 4-6-2? I've not seen many models where they leading and trailing bogies or pony trucks form part of a 3 point suspension, typically they're just along for the ride and suitably sprung to prevent derailment.

The kit has no form of compensation beam or bogie fixed point, to do all of that requires modifications to the chassis with new parts fabricated and added, in my mind all for little benefit, other than wasting an inordinate amount of time at the customers expense.

All of the weight is over the two drivers, the bogie is reasonably sprung to prevent derailments but not to the point of forming a pivot point and like a 4-6-0 along for the ride. In essence it's an 0-4-0T and set up as such. It really doesn't need to be any more complicated than that and I do fear we as modelers tend to over complicate things.

I find the smoothest models are always the ones where the powered axle is fixed, allowing that to float with all the mass of the gear box and motor (plus you have to be careful how you hold the motor to enable it to float) just leads to hours of fettling and testing for (in my experience) little gain.

It would not take much to convert to a 3 point system, there is a big fat stay ahead of the leading axle, it only needs a 2 mm hole in it and a bar passed through onto the top of the leading axle; then open out the bearing holes a fraction above to give the axle a tilt component.

 

[Dave Holt]

Mick,
I agree that trying to accommodate compensating beams can be problematic when fitting prototypical frame stretchers and adds complication. This dilemma probably warrants greater attention in my P4 locos than in 7 mm due to the fine wheel flanges and lack of mass in the smaller scale.
Where my locos are based on kits that incorporate springing (such as Brassmasters) I've generally stuck with that but for kits with no suspension provision, I've mainly gone for full floating (no fixed axle) beam compensation. I have evolved a system that includes bogies in the compensation in a way that transfers weight to the axles without involving the bogie frame (which can slide sideways, on sliding pads, and pivot but not move up and down relative to the main frames, as per many prototypes). Pony trucks generally have a sprung axle in a frame that can pivot but not move up or down, again as per prototype. Within the compensation system, I try to arrange beam lengths and pivot points to replicate the prototype weight distribution, ignoring the unsprung weight of the motor/gearbox and the spring forces from any pony truck(s).
On an LMS or BR Standard 4-6-0, I would have a single beam between the bogie centre (a pin down a hollow pivot tube transferring the load direct to the bogie external compensating beams) and the front coupled axle and twin side beams between the centre (usually driven) and rear coupled axles. A pacific would then have the sprung axle arrangement. I've tried to explain and illustrate this approach in some of my posts on WT, including my Caprotti Black 5 and BR and Ivatt Class 2 2-6-2Ts.
Of course, my models are purely for my own satisfaction and so added complexity and time are of no great significance, unlike much of your work where these are major considerations.
Dave.

 

[richard carr]

Mick

There is a book by Mike Sharman that details how to apply 3 point compensation to a multitude of wheel arrangements including a 2-10-0.
Dave's description of the 4-6-0 is as per the book, I can't remember the others. I tend to apply these to my models, including kit built diesels, as I feel that they run better than fixed chassis, but equally I'm sure all the models you build run really well, so maybe there isn't really a need for it in 7mm.

Richard

 

[simond]

I'm wth Dave here, in that I generally would do something other than an 0-4-0 with such a loco.

My Dukedog has sprung drivers and a fixed bogie pivot, my 48xx has twin rocking beams and a central pivot on the trailing axle - mind you, that was a Springside kit which has a whacking great cast WM cab, and thus it's CoG is somewhere behind the first coach...

But I'm building for the fun and satisfaction of it, so the only cost of the time is "what else could I have built in that time"? and I do think it's worthwhile.

Years back I did a hybrid job on my Castle, it has a fixed height bogie pivot, sprung leading axle, and equalised on the centre and rear. Don't think I'd do that again.

I'm inclined to spring everything now, I think they ride better and look better for it. This could, of course be enirely self-delusional justification for the time and effort involved

 

[mickoo]

There are so many ways to achieve the multitude of variations it'd take several bar crawls and beer to wade through, the end result will probably be the same, folks do what they think is best for them.

I've seen many rigid models run smoothly over complicated track at both low and high speed, by the same token I've seen RTR with unbelievably sloppy wheels (vertically) also perform the same. I've also had across the bench for repairs high end brass models where the springs have dropped out of the horn blocks and the engine is running on the stops, all ran really well leading me to question why on earth were the springs in there in the first place.

I built a fully sprung eight coupled model that ran like a right bag of , chewing the fat with a sage old builder, he said, fix the driven axle (in this case the rear one in the firebox) and throw the bloody springs away....yeah but what about 3 point and springing and engineering and all the usual hand wringing we all do,

Well I took the springs out and it transformed the performance with no other remedial work required, can't really say any more than that.

If a client request a chassis conversion to fully sprung, then that's what'll happen (they will of course be billed for it as it's not a cheap option), but I still fix the driven axle and float the rest, if the kit is designed with compensation beams then that's usually the best way to go, I find no need to add the bogie or pony into the compensation factors, it just complicates matters.

 

[mickoo]

I'm inclined to spring everything now, I think they ride better......

Maybe the focus should be on why they didn't ride better before, sometimes I think we let the tail wag the dog too often in railway modeling.

One other point here is that all bar less than a handful of people, y'all build for yourselves, you can test and check your model on your layout and tweak if necessary. Commercial builders do not have that luxury, you have to best guess and make adjustments accordingly, that means a certain amount of robustness and simplicity is of greater importance.

I've not had a model back yet for poor running which either means I may be doing something right, or, they're all sat in glass cases

Mind, the King Arthur got a pounding at Bucks Hill where the owner ran it for three hours solid before the client accepted it and took it home.

 

[mickoo]

Calling this one done, way out of time and budget for an out of the box build, the more you look at photos and drawings the more you could add, somewhere you have to draw a line and that line has been drawn.

Three outstanding items externally, sand traps and pipes (post paint), buffers (8BA die set in post to lengthen shank thread to make them captive), mud hole clamps (in post). Internally, backhead and pipework (sanity project whilst engine is away for paint), reversing lever handle (same as backhead).

 

[simond]

Sorry, i should have posted this a few minutes earlier. Lovely job, Mick.

re suspension:

My first 7mm model was a Springside 45xx, built out of the box, except fitted with a Portescap. It runs fine but I don’t like the whine from the Portescap, and I don’t like the clunk as the whole loco (rather than a single wheel or axle) reacts to track joints. I have the axleboxes, horns and a Premier helical gearbox & Canon motor to fit, along with CSB suspension.

I have another Premier helical and Canon to fit to my second kitbuilt loco, which was a Finney 47, though that one is equalised as Martin designed it. There will be a couple of Portescaps for sale at some point.

and my track’s not that bad…

 

[Mike W]

A very nice end result. I am sure the customer will be delighted. I model in Gauge 3 which I guess is as different to 7mm as 7mm is from 4mm. All my own kits are sprung, mainly because ham fisted customers can be sure that all wheels will be on the track. We tend to have outdoor tracks which move quite a bit and with live steam speeds can occasionally be .. worrying! Sprung stock is very noticeably quieter and smoother but in terms of staying on the track I see very little difference.

Mike

 

[mickoo]

A very nice end result. I am sure the customer will be delighted.

Mike

Cheers, he usually is, this is the sixth model I've built for him and I have another three at least on the books.

I model in Gauge 3 which I guess is as different to 7mm as 7mm is from 4mm. All my own kits are sprung, mainly because ham fisted customers can be sure that all wheels will be on the track. We tend to have outdoor tracks which move quite a bit and with live steam speeds can occasionally be .. worrying! Sprung stock is very noticeably quieter and smoother but in terms of staying on the track I see very little difference.

Mike

For bigger scales I think springing becomes more important for track holding, as you say, outdoor tracks are not glass smooth.

 

[Dave Holt]

Yes indeed, a very nice model and instructive mix of metallic and printed components.
Did these locos have electric jumper cables for the motor operation bell codes?
Dave.

 

[BR Tony]

Cheers, he usually is, this is the sixth model I've built for him and I have another three at least on the books.

For bigger scales I think springing becomes more important for track holding, as you say, outdoor tracks are not glass smooth.

Yes, Mick, the customer is delighted. You always go the extra mile and that is appreciated and extra costs are an accepted part of high standards.

 

[mickoo]

I'm working through all the back logged repairs and casualty jobs ahead of hopeful delivery at Kettering, bashed a couple away this morning and set them aside as done.

This one was next, a lovely clean straight build, nice paint and weathering, the remit was to get it running as it wasn't as smooth as it could be.

On opening up I found this, I had to laugh, actually it brightened my day considerably



The owner is of this parish and he will see the funny side of it and he will get a ribbing at the bar at Kettering....and many bars later I suspect, frankly it was too funny not to share.

In his defense, I even peered up inside before taking it apart looking for the motor leads as it has tender pick ups which were not connected to anything; I didn't even notice the complete lack of gearbox

 

[oldravendale]

Thank you Mick. Yep! C'est moi. In fact it's been so long since I tested it for myself I'd forgotten I'd taken the motor/gearbox out. Fortunately, though I am short my shoulders are broad - they'll need to be because I don't suppose I'll live this down for a while. Mick has my absolute permission to dine out on the story - not that it'll make any difference whether he has my permission or not.

Thanks for dealing with it, though, Mick.

Brian

 

[mickoo]

Thank you Mick. Yep! C'est moi. In fact it's been so long since I tested it for myself I'd forgotten I'd taken the motor/gearbox out. Fortunately, though I am short my shoulders are broad - they'll need to be because I don't suppose I'll live this down for a while. Mick has my absolute permission to dine out on the story - not that it'll make any difference whether he has my permission or not.

Thanks for dealing with it, though, Mick.

Brian

My second thought.....after where's the *&$% motor... (I've no idea why, but I sneaked a look in the tender half expecting to see a Hornby Ringfield or some such thing in there)... is that maybe it's one of Brians (ABC) new super quiet stealth motor gearbox combos

 

[Yorkshire Dave]

It's digitally controlled - obviously. No motor required.

 

[simond]

It's digitally controlled - obviously. No motor required.

Brio Digital…

 

[Pencarrow]

Brio Digital…

Poor Brian, going to take a while to live this one down...

 

[oldravendale]

That's an easy one to answer... Mick does the no solder solder. I do the no motor motor.

B