"Sentinel" 0-4-0 VBT loco.

[John Candy]

A new project to design and produce a kit for a Sentinel steam shunting loco. is under way, following discussions between Ian T and myself.

The chosen design is the post-war 100HP model of the type represented in the National Collection by this loco.

http://en.wikipedia.org/wiki/File:Sentinel_4wVBTG_at_NRM_York.jpg

Do you know of any drawings of this type (especially the whereabouts of the General Arrangement drawing) or have information and photos you can contribute to the project?

The intention is that the model will be electrically powered (with battery/radio control or track-collection option) and the kit will be extremely simple to assemble, with the minimum of parts, mostly screw-together.

The aim is to produce a simple, low cost, model.

John Candy

[John Candy]

Ian and I are progressing this project with a view to having something to show at the AGM.
It is early days but the preparatory work is under way.

The loco will have chain drive as per prototype and Ian is dealing with the running chassis parts while I concentrate on the body mouldings and detailing.

Question has arisen on whether the loco should be sprung, compensated/equalised or left totally unsprung.

It will be geared/powered to run at a around a max. scale 20MPH (even that is faster than the prototype at 17MPH) so derailments should not be a problem, even with "solid" suspension.

Does anyone have the GRS Y1/Y3 (either live steam or electric models) and does that have any form of equalisation/compensation/springing and, if not, is there any problem with derailments?

John.

[454]

John,

Seems the reply button has appeared now. So have copied the email I sent to you earlier for the record.

My GRS kit electric Sentinel is fixed axle no suspension, no compensation.
It has never ever derailed on cleared track.
It has only derailed on points set against it or twigs that have fallen from the trees.

So don't waste time & expense messing about with that kind of sophistication. Keep it simple.


Dave
454

[MikeWilliams]

John,

I don't have any such loco and all of my own wagons are sprung because they ride smoother and sound better.  But, this engine has a wheelbase not much longer than a wagon and there are plenty of GRS kits, early Brandbright kits and scratchbuilt vehicles is use with solid axles so I'm sure it would be fine, if a bit clonky over some joints.

Much cheaper to provide fixed axles and the whole concept is low cost.

Mike

P.S. John - will answer your e-mail about this engine tomorrow.

[John Candy]

Mike,

Good point about wheelbase....in fact it is only half that of a wagon, being just 4ft 9ins.!

The wheels are just 30ins. diameter which is a slight concern, since they could well clonk over the crossings in turnouts, etc. (unless the crossing/"frog" has been infilled to flange depth).

I am wondering whether overscale wheel treads (to the "old" G3 standards) would be better than the newer slim standard, providing extended support over the gaps in crossings.

John.

[454]

John,

I do not believe that on the G3 GTG scene there has been an item of motive power with smaller wheels than my Fowler Railbus.

My Fowler Railbus has really tiny wheels & derails only sometimes when the gauge has been widened on curves.
But that could be speed related which is not an issue with the Sentinel. Yes is clunky over point frogs, but my GRS Sentinel has never had a problem in that respect.

So leap into 30" wheels with confidence & get the show on the road. If they clonk they clonk, tough.


Dave
454

[MikeWilliams]

There is also Arty's little Ruston which seems to perform amazingly well, albeit on small indoor layouts.  So far as I recall that is not sprung or compensated either.

As you well know, if you have a solid chassis you need to take a lot more care to assemble it dead square, whereas springing means all four wheels will be on the track however bad your soldering, but remind me - is this to be a kit, or RTR?  If the latter, then its not a problem.

Mike

[John Candy]

Mike,

Ian and I will be making the prototypes with a view to a "kit producer" taking over the moulds, CAD, etc. and offering a kit with RTR option.

Idea is that the kit will be (as far as practicable) "screw together" so a low skill threshold is required (which will also make it quicker for the kit producer to churn out RTR versions).

No idea who the kit producer may be but we have our "preferred option"!

Regards,
John.

[John Candy]

I am pleased to confirm that our "preferred option" kit-producer has agreed to participate in this project.
The kit and RTR options will be offered by Mike (Williams Models).

The development work will continue to be undertaken by Ian T and myself, with additional input from Mike on various design aspects.

The provisional timetable is to have a working chassis by the end of the year and a completed model in time for the AGM in February.

John.

[Geoff Nicholls]

I hope the preferred supplier has consulted his financial director about this.
I suggest you also produce a small(micro) layout to display it, say a Cliff Barker 4' 11" radius turnout and sector plate/fiddle yard, on a board that fits in a car. Then it could be the subject of an article in the modelling press, and be exhibited at shows.

[John Candy]

Dave,

The Sentinel will be as near-to-scale and as detailed as we can make it, while staying within budget (I hope it will be possible for the kit, complete with radio control and battery pack, to be sold for around 250GBP) but the final cost cannot be confirmed until quotes for wheels and other components have been received.
The aim is for the kit to be offered as a simple "screw-together" job.

The target date for the first models to be at the AGM is believed to be realistic.

The idea of the dockyard diorama was put forward as a longer-term idea.

Regards,
John.

This thread has been split....discussion of a diorama to display loco continues at....
http://lakes-pages.com/gauge3.co.uk/G3Forum/index.php?topic=1375.msg8332#msg8332

[IanT]

Ok, just a few words on the process we're using.

A 'master' drawing is being drawn 'full-sized' to the best available information to hand (not a GA but a pretty good dimensioned drawing). This is currently what I think of as the "MK1" type (non-bunkered, training torsion bars etc.). Not agreed yet but I believe that the version we will actually model is probably the "Mk2" (rear coal bunker, front torsion bars, various detail changes). It should be a simple progression from the Mk1 drawing to the Mk2 - as the original prototype engine was also evolved whilst retaining the underlying design.

Once completed to sufficient detail - the full sized 'master' will be scaled at 1:22.6 (exact scale) and from the 'scaled' version - component drawings will be made. At this stage we will start to move from "the way it really was" - to "the way it needs to be modelled" (given constraints of cost and ease of 'build' required) and some compromises will be necessary.

However, the essential proportions of the engine will be correct (or as good as I can make them). So whatever level of 'finesse' the engine is offered at - hopefully it will be a good enough foundation to bring up to what we would probably think of as 'Finescale' if the owner so wishes and has the necessary skills to do the additional work.

Cannot say too much more at the moment as quite a bit of the detail is still in flux but this is the design process being used and hopefully the end result will be useful to a range of modellers - both beginner and the more advanced.

Regards,

IanT

[John Candy]

The Sentinel 100HP project is now well underway, with Ian T , Mike and myself all applying our minds to the best method of producing a loco with as near as possible scale appearance, while keeping the cost to an absolute minimum.

One item which is taxing our brains at present is the wheels.
These are of exceptionally small diameter (30 ins) which presents the following problem : If the wheels are cut to the G3 standard (as used by Slaters) will turnout crossings ("frogs") cause them problems?
Running a Slaters wheelset of a scale 33 ins diameter across a Cliff Barker crossing causes the wheelset to drop by about 1.5mm.

If the crossing were to be "infilled", the flange would support the wheel but we cannot count on that being the case, since CB supplies ready-made turnouts without infill.

Can someone with a GRS LNER Y1/Y3 AND Cliff Barker turnouts, please do the following?

1) Measure the diameter of the wheels (over tread).
2) Measure the depth of the flange
3) Confirm whether (or not) the loco will run through Cliff Barker turnouts (WITHOUT INFILLING OF THE CROSSING/"FROG") without the wheels dropping into the gap in the crossing.

Thank you!

John.

[454]

John,
My Sentinel has run on GRS track, Cliff B track, G3S track etc & I have not consciously noticed that there has been an issue whilst negotiating switch frogs. Cannot believe this would be a problem even with wheels that small. My Fowler rail bus just skips along happily with it's minuscule wheels & that has been run on every standard of track imaginable.

Has anybody witnessed a real 0-4-0 wander through a set of points in shunting mode when light engine or even hauling or propelling wagons? They rock & clunk & oscillate all over in every direction. To create & expect an 0-4-0 which simply glides silky smooth through siding pointwork seems a departure from reality.

Cheers
Dave
454

[John Candy]

Dave,

The dimension which is critical is the width of the tread.
The current G3 standard is a minimum of just 5.2mm but we are proposing 6.4mm for our small wheels (overall width of wheel 8mm minus flange width 1.6mm).
I have just tried this over a Cliff B turnout and it gives a much better "ride" than a standard Slaters wheel.

I dis find that my GRS Peckett-based Bagnall 0-4-0 tank tilts right over (with the wheels at one corner "up in the air") and this is supplied with LGB wheels.
The GWR 1361 class, supplied with the same wheels, is an 0-6-0 so does suffer from the same problems.

It would be useful to know the widths of the wheels on the GRS Y1/Y3, for comparison purposes (I assume they cannot be Slaters).

Regards,
John.