Rapido/Locomotion Models GNR Stirling Single

[Phil Parker]

So the two axle drive looks like the best solution, I wonder if it has been tested yet under practical conditions and what is expected of it.

 

Stephen

 

Scorpio models do a GWR single in O gauge which has the same sort of drive system. If anyone has built one of these, they should be able to give an idea under real world conditions.

Edited April 17, 2017 by Phil Parker

[rapidobill]

So the two axle drive looks like the best solution, I wonder if it has been tested yet under practical conditions and what is expected of it.

 

Stephen

This being the first full sample and with it only having been delivered just before the show, actual test running time has been limited. However, it did run for quite a while on Monday night (before I gummed it up with Halfords' primer!) and it operated well, including over #2 radius curves and set track points. It hauled 4+ full-length coaches as is, but I expect more. The front bogie was sprung using a mix of left-over springs at the factory and the spring rate is too soft. the rear wheel. This causes the rear wheel to not make full contact with the rail so the main driver was doing most of the work. This and other small issues will be sorted while I'm in China next month, Watch for an update from there.

 

Bill

[34theletterbetweenB&D]

You mean this will be a RTR OO model where I won't have to fiddle around with carrying wheel springs to optimise performance? (In all fairness both Bach and Hornby have shown significant improvement of late in this matter.) Really interesting to see and read what has been achieved in the process of development of this model, thanks to those who made these recent posts. Mr Stirling's high stepper properly looking very sexy indeed.

[bertiedog]

Are there any rtr, or kit, coaches that would suit, by suit, teak finish, not really concerned as to exact accuracy,, just about four coaches for display running.

Stephen.

[rapidobill]

You mean this will be a RTR OO model where I won't have to fiddle around with carrying wheel springs to optimise performance?

If you let us know which order you are we can put a note to remove the front spring if you really enjoy doing this....  

 

Bill

[Steamport Southport]

Are there any rtr, or kit, coaches that would suit, by suit, teak finish, not really concerned as to exact accuracy,, just about four coaches for display running.

Stephen.

 

Nothing really as the last one was withdrawn in 1916 before anything even close RTR was built. But number One was returmed to steam in the 1930s and then again in the 1970s and 1980s.

 

 

That's the reason I wanted one with the other tender as then it could have ran with LNER Gresleys and even BR mark ones. Nevermind.

 

 

 

Missed the kit bit. I believe Bill Bedford is making suitable GNR coach kits.

 

 

Jason

Edited April 17, 2017 by Steamport Southport

[JSpencer]

This being the first full sample and with it only having been delivered just before the show, actual test running time has been limited. However, it did run for quite a while on Monday night (before I gummed it up with Halfords' primer!) and it operated well, including over #2 radius curves and set track points. It hauled 4+ full-length coaches as is, but I expect more. The front bogie was sprung using a mix of left-over springs at the factory and the spring rate is too soft. the rear wheel. This causes the rear wheel to not make full contact with the rail so the main driver was doing most of the work. This and other small issues will be sorted while I'm in China next month, Watch for an update from there.

 

Bill

It sounds like a challenge to balance that. Too strong a spring on the front bogie will take weight away from the drivers (if far too strong, the drivers will be lifted off the track completely). Too soft causes the trailing wheels to lift.

 

But that will not be the end of the problem. Change in incline going up will compress the spring causing the bogie to apply a lifting force at the front. This can then cause the drivers to loose adhesive weight at the worst moment, or worse, lift off the track altogether.

 

Ideally it would be best for both bogie and trailing wheels to be sprung (equal strength and distance from the drivers - or calculated to give the same) with all weight centred over the drivers themselves. The resulting model would cope with any kind undulating track work thrown at it too ( I'm a fan of spring axles and believe they bring therapeutic properties for their owners).

 

There has been much discussion on weight distribution of the Hattons 14XX thread whereby weight is centred behind the drivers meaning the front pair serve no purpose,

Better the model is lighter with weight correctly centred over the drivers than a heavy model with weight focused over non driving wheels.

Edited April 17, 2017 by JSpencer

[bertiedog]

I am not suggesting it would be needed in this case, but you could put weight on the front of the two axle area, with a pivot just behind the driver and a long Sharman style drawbar to the tender.

 

The front two axles on the tender "float" in the bearings or have a small hidden frame added so that the tender weight bears down on the drawbar, and if the tender is heavy enough can dramatically improve the running.

 

The drawbar at the front end must be supported by a large washer to keep it level to the back of the loco where it acts as an ordinary coupling to the tender, the front of which is supported on the drawbar.

 

It increases traction, but also steadies the running of the tender. But the drawbar is not easy to make as it has to be a T section for strength. It shows no more than an ordinary draw bar. Mike Sharman developed the idea mainly for Crampton Locos with rear drivers.

 

But I suspect the powered rear wheel approach will work as well, bar setting the springing of the front bogie.

[JSpencer]

I am not suggesting it would be needed in this case, but you could put weight on the front of the two axle area, with a pivot just behind the driver and a long Sharman style drawbar to the tender.

 

The front two axles on the tender "float" in the bearings or have a small hidden frame added so that the tender weight bears down on the drawbar, and if the tender is heavy enough can dramatically improve the running.

 

The drawbar at the front end must be supported by a large washer to keep it level to the back of the loco where it acts as an ordinary coupling to the tender, the front of which is supported on the drawbar.

 

It increases traction, but also steadies the running of the tender. But the drawbar is not easy to make as it has to be a T section for strength. It shows no more than an ordinary draw bar. Mike Sharman developed the idea mainly for Crampton Locos with rear drivers.

 

But I suspect the powered rear wheel approach will work as well, bar setting the springing of the front bogie.

Oh,,, ah! Don,t like the sound of that system personally.

[Jeff Smith]

Personally I do not favour the 'weighted tender' solution. Two of the three 4-4-0s I have built have had the drivers compensated with side centrally-pivoted beams so that no matter (within the movement allowance) what angle the footplate is to the track all four wheels are firmly on the track. The bogie controls the height of the front and thus keeps the footplate level with the track - it has a certain amount of side-play but with a weak centring spring. These two locos didn't have tenders anyway. The third one, which did have a tender, had a fixed rear driver with the front driving axle compensated with a central beam to the bogie. Weight on the rear from the tender would have ruined the balance..... These were all in P4 but in OO, with the bigger wheel flanges the main reasons for keeping the wheels firmly on the track is for current collection and adhesion.

[bertiedog]

Well I built many singles with the Sharman coupling, and an LBSCR single No 200 Dieppe is about to be done that way in a few weeks, they all work and gain a curious smoothness in operation as though the tender is sprung.

 

The drawing shows a 422, the joint underneath can be rigid or with a small left to right movement, and the tender sits on the bar, transferring the weight to the loco. You pack the tender with lead,

Such an arrangement with both axles powered would be interesting. No problems with sudden gradient changes causing wheel lift.

 

 

Not in any way suggesting Rapido do this, just for reference in case another type needs a hand on pulling or smooth riding, which the system helps. It cures the Lord of the Isles pulling problems.

 

Credit for the idea goes to Mike Sharman, not me,

 

Stephen.

Edited April 17, 2017 by bertiedog

[Roy Langridge]

Well I built many singles with the Sharman coupling, and an LBSCR single No 200 Dieppe is about to be done that way in a few weeks, they all work and gain a curious smoothness in operation as though the tender is sprung.

 

The drawing shows a 422, the joint underneath can be rigid or with a small left to right movement, and the tender sits on the bar, transferring the weight to the loco. You pack the tender with lead,

Such an arrangement with both axles powered would be interesting. No problems with sudden gradient changes causing wheel lift.

 

ss.jpg

 

Stephen.

However many times I look at that picture I find that it seems to be trying to defy the laws of physics. Surely the trailing wheel acts as a pivot, lifting weight from the driver?

 

Roy

Edited April 18, 2017 by Roy Langridge

[Titan]

However many times I look at that picture I find that it seems to be trying to defy the laws of physics. Surely the trailing wheel acts as a pivot, lifting weight from the driver?

 

Roy

I presume the trailing wheel is not in any way attached to the drawbar and is therefore not a pivot point for it.

[JSpencer]

However many times I look at that picture I find that it seems to be trying to defy the laws of physics. Surely the trailing wheel acts as a pivot, lifting weight from the driver?

 

Roy

 

I think the drawbar passes underneath the trailing loco wheels otherwise it would indeed make no sense. Not a solution I would go for on an RTR model personally. In any case the Rapido model will doubtless use the tender space for DCC sound.

 

From an RTR perspective, the classic solution is for all weight to be centered just behind the main drivers with the trailing wheels fixed (not sprung), and the front being light with a lightly sprung bogie. You could place the motor in the smoke box, and use a drive shaft to a compact gearbox (what Hornby did on their J15 and their recent Merchant Navy) and therefore maximize weight over the drivers.

The solution used is a diecast body, so doubtless a heavy model for sure, but one which requires a sufficiently strong (though not overly so) bogie spring to ensure the rear wheels remain in constant contact with the rails.

 

Given how tight the front bogie wheels sit with the front splashers, there will not be much up play to start with unless the splashers are part of the bogie. This is Rapido's first steamy and they picked a challenging subject for sure.

[bigherb]

However many times I look at that picture I find that it seems to be trying to defy the laws of physics. Surely the trailing wheel acts as a pivot, lifting weight from the driver?

 

Roy

The front bogie wheels are not bearing any or minimal weight. The weight of the boiler in front of the drivers is pivoting over the drivers being balanced by the weight of the tender, if done right there would be minimal weight on the trailing wheel and most of the loco weight would be on the driven wheels.

[No Decorum]

The “trailing” wheel is powered, is it not?

[Jol Wilkinson]

It should be remembered that Rapido are producing a RTR OO model. Therefore it is important that they produce something simple to use, robust and reliable. 

[Hilux5972]

The “trailing” wheel is powered, is it not?

Yes I believe it is.

[34theletterbetweenB&D]

... a challenging subject for sure.

It should be remembered that Rapido are producing a RTR OO model. Therefore it is important that they produce something simple to use, robust and reliable. 

All too true.  Apart from this prototype's importance to UK express power development, and its outrageous beauty; not least of my interest in a purchase is seeing how Rapido get around the many 'inconveniences' that Mr Stirling's design visits on those required to produce a set track capable OO model. Having a representative of Rapido prepared to discuss their doings 'ices the cake' on this project.

[Theakerr]

I have just seen some pictures on Wright Writes.  It looks really nice but I do hope that front coupling pocket is removable (like the one on the Bachmann A2).  It sticks out like the proverbial sore thumb and looks absolutely awful.  Whilst I don't mind taking the shears and knife to said offensive pocket on some lesser models, I really don't want to do that on this one.

Same comment may apply to the back of the tender but I haven't seen a picture. 

[Steamport Southport]

Exactly my thoughts when I saw the picture of Bill holding it. I wouldn't have thought it would work tender first very often and it would probably lead if double heading something like an Atlantic.

 

Still undecided about this.one.

 

 

Jason

[CF MRC]

Probably very wise to power the rear wheels. My experience of a Johnson single is that the sloppy track and wheel standards of N (and by implication OO) meant that the engine spent as much time going sideways as forwards. Conversion to 2mm finescale made a significant difference to haulage for this loco, as the wheel / rail standards work better.

 

My later GNR singles have no problems pulling long trains, especially the Ivatt rebuild of a Stirling 2-2-2 with a weighted Sharman type tender. Interestingly enough the Stirling 8' single worked better without a weighted tender, but there is a lot of front end weight and the loco is effectively only supported by its driving wheels and a centre pivot on the front bogie wheels only - the rest go along for the ride.

 

Glad also that the splashers will be adjustable on the Locomotion model. For the best appearance, it is important that these are as close to the bogie wheels as possible.

 

Tim

[34theletterbetweenB&D]

...I do hope that front coupling pocket is removable (like the one on the Bachmann A2).  It sticks out like the proverbial sore thumb and looks absolutely awful...

 Mr Stirling would probably agree. He wouldn't have a brake standard on the front of the 4-2-2s while he held office, they were not to run double headed!

 

Whatever, the underside view reveals that with the front bogie wheel unclipped the pocket will easily enough be cut away. That will be my choice. If there is any future owner he or she may cement it back on! (I usually leave such small deleted parts in the bunker space so they stay with the model.)

[JSpencer]

I have just seen some pictures on Wright Writes.  It looks really nice but I do hope that front coupling pocket is removable (like the one on the Bachmann A2).  It sticks out like the proverbial sore thumb and looks absolutely awful.  Whilst I don't mind taking the shears and knife to said offensive pocket on some lesser models, I really don't want to do that on this one.

Same comment may apply to the back of the tender but I haven't seen a picture. 

 

While I agree it sticks out like a needle in a sore thumb in grey, will it be less intrusive in black?

[G-BOAF]

A few observations based on the Wright Writes pictures and feedback for Rapido:

The lifting holes on front frames are too large

The brake rods accross the front drivers should be near horizontal.

The interface between the smokebox and cylinders needs to be improved (I accept there will be a slight line visible)

The transition of the curve handrail over the smokebox door should be a curve rather than a sharp angle (is this just a feature of an prototype model?)

Buffers should have holes in the middle.

 

http://www.rmweb.co.uk/community/index.php?/topic/64295-wright-writes/page-648

 

Other than that, lovely model! My comments are supposed to be constructive :-)