6 Wheel Chassis for GNR Coaches: OO

[MikeTrice]

I really don't think any of those two suggestions would work given the limited clearances. Instead I have taken a more drastic action: provided a recess in the underframe for the wheels to move in and remove the centre of the w-iron units.

 

A template was produced to show where the cutouts needed to be provided:

 

Holes were drilled in each corner and the scrap fretted out with a piercing saw leaving a ledge alongside the solebar:

 

The assembled w-iron unit was then epoxied over the cutout:

 

Once cured the remaining brass w-iron centre was removed using a rotary slitting saw:

 

The wheels popped back in now have plenty of clearance and can travel the full depth of the spring without the posibility of shorting. One down, two more to cut:

[JCL]

Interesting Mike. This is becoming quite a job. If there is so little clearance, and I know they will be mounted differently, but it'll be interesting to see how much the middle pair can slide.

[MikeTrice]

The centre wheelset were mounted on some 2mm o/d 1mm i/d brass tube from Eileen's Emporium. A length of 1mm steel (also from Eileen's) trimmed to length and the ends rounded off in a drill with a file:

 

Mounted in the chassis showing the potential displacement:

 

 

So how did it run? Initially not very well until I discovered one of the centre wheelsets was jammed stopping the unit from springing upwards. On cleaning out the spring carrier it performed much better.

 

The minimum radius this arrangement managed is Radius 3.

[MikeTrice]

Hindsight is a wonderful thing. Having messed around with the Bill Bedford sprining units and complicated things considerably an alternative solution dawned.

 

Two pieces of 0.6mm N/S wire are soldered across the units, then slots to clear the wheel flanges fretted out with a piercing saw:

 

In the end I opened the slots out further as can be seen here:

 

Now the wheels can move throughout the spring range and providing the units are not mounted to a metal floor cannot short. If only they were available like this to start with and to the GNR pattern

[MikeTrice]

This may well be my last post on this subject as there are few options left.

 

Comet Models produce a w-iron specifically for 14mm wheelsets:

 

It is based on the rocking w-iron principal. The instructions state "it may be necessary to open the slots slightly to ensure the wheel rims clear the stretcher base". I interprete this to mean that they did not allow sufficient in their artwork and only realised after the etches were produced:

 

I was able to open them out using some very fine needle files. Here the left slot has been widened:

 

Here is the arrangement I used (not as described in their instructions) with a fixed w-iron one end, a rocking one the other end and a piece of 0.45mm brass wire acting as both a pivot and suspension for the centre wheelset:

 

The etch includes a central cradle which is intended to be soldered to one of the w-irons, but proved ideal as a carrier for the centre wheelset seen here soldered to the carrier wire:

 

With the centre cradle soldered and the carrier wire threaded through to act as pivots in reality only one end of it needs soldering as can be seen here:

 

The other end is left unsoldered so that on displacement of the centre cradle the wire can move unfettered:

 

Thus fitted the chassis will accomodate Radius 2 curves.

 

Of all the options the Comet solution is by far the easiest however unlike the Brassmaster's Cleminson, the w-iron profile is incorrect for GNR coaches. Only the Brassmaster etch provides the correct w-iron, so any other solution is going to involve a compromise or further modification to correct.

 

[billbedford]

There is a w-iron in the Bill Bedford range designed for 3'7" wheels - BBWF003-4

 

There are also 3 specifically designed for 6 wheeled coaches I suspect the MR one is as close as you need - BBWF517-4. Note that the graphic on this page shows the 7mm version. The correct  version is:

 

BWF517 MR Coach W-Irons.pdf

Edited June 25, 2016 by billbedford

[MikeTrice]

I have also used the MR ones you mentioned and as you suggest they are probably the closest available, however I honestly feel it would be a great benefit if you were to do some to the GNR carriage style which is distinctly wider:

 

I chose the pedestal units on the basis I could add a styrene w-iron representation on the outside and fully accept that I am using them in a way that I assume they were not designed. The big benefit from using your units is it results in the narrowest underframe and there is no need to provide clearance for the w-irons to rock.

[MikeTrice]

Sorry Bill, can you clarify something please. Are you saying that ONLY BBWF003-4 suits 3'7" wheels? That would imply the other 6 wheel coach ones are for 3'1".

 

Thanks.

[billbedford]

There are four that are designed for 3'7" wheels BBWK003, 017, 020 and 031 with BBWK517, 520 and 531 using w-iron from the frets with the same last two digits but in a different configuration of the fret.

 

 

I have also used the MR ones you mentioned and as you suggest they are probably the closest available, however I honestly feel it would be a great benefit if you were to do some to the GNR carriage style which is distinctly wider:

 

I've given up designing etches, especially these small frets, but there is nothing to stop anyone else drawing up a similar arrangement for prototypes that are not included in the present range.

[MikeTrice]

Thanks Bill. I think my simple answer is to cut the wings off of the 3'7" versions to look like the pedestal version then add a cosmetic overlay in styrene.

[MikeTrice]

Following Bill's comments I can confirm that I have tried a set of his MR 6 wheel w-irons (BWF517/4) and can confirm that I have no clearance issues with them. By snipping off the existing wings of the w-irons I effectively have pedestal units for 14mm wheelsets.

 

Thanks Bill.

 

Edit: I should add that the MR etch includes brakeshoes on two of the w-irons and the triangular brake rodding, ideal for GNR coaches.

Edited June 26, 2016 by MikeTrice

[gr.king]

The Comet solution that you have illustrated is essentially the one that Dan Pinnock incorporated into his D & S kits, as you no doubt know. My three OO gauge D & S six wheelers, with the centre "lightly sprung / floating" unit given more sideplay than the kit originally allowed for, also cope with second radius set track if required. The fact that the outer axles don't steer appears not to matter. The one thing that has to be kept in mind if giving more sideplay to the centre unit in the D & S design is that it becomes necessary to partly bridge or blank off the cut-out in the floor pan above that unit, otherwise the top edges of the moveable unit can catch on the edges of the cut-out as sideways displacement can encourge the unit to tilt a little.

[micklner]

The Comet solution that you have illustrated is essentially the one that Dan Pinnock incorporated into his D & S kits, as you no doubt know. My three OO gauge D & S six wheelers, with the centre "lightly sprung / floating" unit given more sideplay than the kit originally allowed for, also cope with second radius set track if required. The fact that the outer axles don't steer appears not to matter. The one thing that has to be kept in mind if giving more sideplay to the centre unit in the D & S design is that it becomes necessary to partly bridge or blank off the cut-out in the floor pan above that unit, otherwise the top edges of the moveable unit can catch on the edges of the cut-out as sideways displacement can encourge the unit to tilt a little.

 

I have added as much lead as possible underneath the centre axle carrier, as I found on the D&S kits I have built  the centre axle was reluctant to go around curves without derailing . The small amount of lead I managed to fit helped its behaviour.

[scotcent]

Why not cut a wee slot each side of the base to allow a bit more vertical clearance for the wheel tread?

This could, relatively simply, be done using a cutting disc

Jim P

 

Do  you  have  Bill  Bedford's  W  Irons  for  coaches  or  NPCS?  These  cater  for  the  larger  wheels.

 

Allan  F

[MikeTrice]

A quick recap. One of the chassis was being built to suit a Diagram 3D D281 Third Brake 6 wheeler. The Diagram 3D body is too narrow and so I had to reduce the overall width of the solebars to suit. The chassis was put together with Bill Bedford's pedestal units which I had modified to accomodate coach wheels, the centre wheelset featuring Bill's suggestion of sprung pedestals and a 2mm brass tube sliding on a 1mm axle.

 

I used the pedestal units as nothing approached the original GNR w-irons from Bill's range. My idea was to produce styrene "cosmetic" w-irons to the right pattern to use as overlays.

 

Here are a couple. The one on the left was cut by hand, very badly, at which point I decided that this was a job for the Silhouette Portrait cutter, the result of which is on the right. Why on earth I thought I could cut them by hand I will never know. Call it a "Senior" moment:

 

The overlay in place stuck on with minimum amount of epoxy so as not to gum up the sliding axle bearing:

 

Note that with the non-existant depth to the solebar there is very little room remaining for the cosmetic axlebox:

 

With the cosmetic axlebox/spring added they float outside the solebar:

 

The cosmetic 6 wheel components available from my Shapeways' Shop were not designed to be used with a central axle that was mounted in external bearings so in oder to fit them I had to grind part away with a mini brill and diamond burrs:

 

Here is the central unit in place:

 

Again lack of solebar width causes problems:

 

I did manage to resolve to a minor degree some of the issues by bending the spring ends inwards and fixing them to the solebar with superglue:

 

And this is how I have left things at the moment. All a bit of a bodge really just to try and use the Diagram 3D body:

 

 

 

 

[gr.king]

I wonder whether those in charge of Diagram3D would now care to consider altering their designs in order to give full width to the coaches at solebar level? Failing that, or in the meantime at any rate, builders of the kits may be able to work out how to alter the construction so as to get true width, or possibly a trifle more than true width to facilitate construction of a chassis that will go round curves..

Edited July 5, 2016 by gr.king

[MikeTrice]

I think option one is the only viable way forward. Stretching the width would have a knock on effect on the panelling overlays.

[MikeTrice]

Against my better judgement I am going to have one more attempt at producing a 6 wheel chassis for the Diagram 3D bodies.

 

Early 7'6" coaches had a 7'1" dimension across the bottom of the coach which is still fractionally larger than the D3D bodies. I think I have fathomed out a way to shoehorn a chassis into the body without the issues previously highlighted. I have started building a new unit, however it will probably be a few days before I can say if it will work or not and provide photos.

[MikeTrice]

Why have I had a problem with Diagram 3D kits? Well a lot of the problem has been of my own making.

 

As designed the D3D kits have a fixed floor to which the varous body parts are attached. In my thread reviewing these kits I devised a way of building them with a removable floor. Allowing for the thickness of the sides the remaining cavity was too narrow to accomodate a chassis based on the way I have built them so far in this topic. I also compared the overall body width for one of their coaches against a 7'9" wide prototype whereas I should have been comparing it to a 7'6" wide prototype.

 

So going back to first principals and comparing various dimensions against the prototype I think I have come up with an approach that looks to be working which I will detail now.

 

There seem to be two general widths of GNR 6 wheel coach, those with Guard's portions at 7'6" and those without at 7'9" (whether this rule is always the case I cannot state so please don't take it as gospel). At the time of writing D3D produce 5 vehicles as follows:

 

D281 4 Compartment Brake Third @ 7'6"

D156 5 Compartment Composite @ 7'9"

D245 5 Compartment Third @ 7'9"

D243 6 Compartment Third @ 7'9"

D303 Full Brake @ 7'6"

 

On the prototype the solebars are 4.5 * 11 inches with a 6'1.25" spacing giving an overall width of 6'10.25" (27.42mm)

On the 7'6 bodies the width across the base of the bodies is 7'1" (28.33mm) thus the prototype underframe is slightly narrower than the base of the body. On the 7'9" bodies there is an additional 3" overhang.

 

Based on my research to date in this thread the method I wanted to use for these vehicles features Bill Bedford sprung w-irons for the two outer axles and a separate internal cradle allowing the centre axle to just go along for the ride. An assembled Bill Bedford unit is approximately 24.65mm across the outer faces which is slightly wider than the prototype's 6'1.25" spacing. So in order to feature a scale width solebar I would need to increase the overall width of the chassis, not desirable given the narrowness of the body. I could recess the solebar as I have done previously but would need to ensure that the cosmetic spring mountings are located sensibly. Instead I reasoned that if I dropped the scale 1.5mm width of the solebar down to 1.25mm I might just get away with things as I would have an overall model width of 27.2mm compared with the prototypical 27.42mm. Near enough and still giving the correct external appearance compared to the body.

 

Instead of trying to mount my underframe on a solid strip of styrene I decided to modify the approach to make the solebars a separate assembly. With this in mind I produced a template and used it as the basis for measurements and assembly starting with cutting spacers from a single length of 60thou black styrene 24.7mm wide which was then chopped up to the lengths to match the template. These were stuck down to the template with a glue stick using a ruler to ensure alignment:

 

A length of Evergreen 137: .030 x .156" (0.75 x 4mm) strip was cut slightly overlength and glued in place against the spacers:

 

A length of Evergreen 127: .020 x .156" (0.5 x 4mm) strip was then laminated to the first piece and process repeated for the opposite solebar. This lamination gives me the desired 1.25mm solebar width:

 

The chassis was removed from the jig and the solebars filed to length then headstocks added using the same technique. Here a Bill Bedford w-iron has been placed between the solebars to chack they are a good fit:

 

Here is the unit for a D245 5 Compartment Third:

 

And placed under the body:

 

Likewise for the narrower D281 4 Compartment Third Brake:

 

And placed under that body:

 

So at this stage all is looking promising. The dimensions of the chassis compare favourably with the D3D bodies and do accept the chosen suspension system. A quick trial with my 3D printed axlebox/springs show that the spring mountings work fine with the 1.25mm solebar so looking good so far.

 

Once the solvent has dried off the overall height of the solebars can be reduced to 3.66mm on a flat sheet of wet and dry paper and the length of the headstocks reduced to match the bodies.

 

I have taken the liberty of attaching a PDF version of my template which should be printed off with no scaling. At present it only contains templates for the D281 and D245 coaches, however I will produce a second version later covering all 5 D3D bodies.

 

 

 

Diagram 3D chassis.pdf

[MikeTrice]

Taking the main w-irons from a Bill Bedford 4mm MR 6 wheel W-Irons fret the side wings were snipped off with Xuron cutters:

 

Any remaining edges were then filed smooth:

 

During a previous experiment I had used a styrene overlay to give the correct pattern w-iron as used by the GNR. The disadvantage of this is it adds thickness to the w-irons which can be ill afforded. I did try cutting them and gluing them behind the w-iron but did not feel it would be very robust. In the end I decided to fit replacement metal wings.

 

First off a drawing was produced to show where the new wings were to fit to the pared down w-iron etch. Once that was done I could produce a simple jig from mounting card to manufacture the new wings:

 

The jig is easy. Just load up a length of 1mm * 12thou brass (or in my case N/S as I had it to hand) then snip off against the edges with the Xuron cutters:

 

It was then relatively easy to produce a number of near identical strips with correctly angled ends:

 

To assist in the soldering I created another jig that would hold the main etch in place and guide me for the positioning of the new wings:

 

The new wings are soldered in place. I thought this would be more difficult than it ended up:

 

After all soldering completed cleanup followed:

 

Of the two faces the inner one is the most important as any solder must not restrict the sliding of the axle bearings:

 

Here the revamped w-irons have been folded up and positioned in the solebars to check fit:

 

The revised profile can be seen in this view. Unfortunately the autofocus insists on focussing on the rear w-iron:

 

[chris p bacon]

Really appreciate the tutorial on these Mike, I have all this to come!

[MikeTrice]

Bill Bedford units with springs and axles in place. The supplied brakeshows have been adjusted to better match the OO wheelsets, however I am having second thoughts about retaining them as they are now in the wrong position relative to the centreline of the wheel and the supplied brake yokes are now too wide to fit:

 

The two units have been glued to the solebars with 5 min epoxy using the template as a location guide:

 

The outer springs/axleboxes from my 3D printed GNR 6 wheel coach set:

 

Here two axlebox/springs have been epoxied (sparingly) to the w-iron/solebar remembering to avoid getting any adhesive on the sliding bearing carrier. The spring shoes fit the slightly thinner solebar quite well:

 

This is the chassis so far posed with a Diagram 3D D281 body:

 

 

Note to self: I really must dust the end of the D3D body!

[MikeTrice]

The central wheelset cradle is fashioned from an old mjt internal unit I had lurking around. Unfortunately this was in EM/P4 so needed narrowing to accept OO wheelsets. The two pillars were separated and bent over to provide a soldered joint lowering the ride height at the same time:

 

A mounting plate was fashioned from the offcut of the MJT unit and the two units soldered together using 0.6mm N/S wire with the template to position the various elements:

 

Top view of the central cradle to illustrate the way the sides were folded over before soldering:

 

Wheelset fitted after shortening the axles with a rotary drill and the mounting plate epoxied to the underframe, again using the template as a guide:

 

Rather than just let the central wheelset flop about I decided to fit a restraining strap to limit it movement. This was fashioned from 0.6mm N/S and the depth set by standing the outer wheelsets on offcuts of mounting board and ensuring the central wheelset can touch the work surface:

 

The 3D printed central axlebox/springs ready to fit:

 

And now glued in place:

 

 

Here is the chassis on a previously completed D3D body. The roof vents and lamps were also mouldings from my Shapeways Shop:

 

The same chassis offered up to the provided D3D MDF floor:

 

So there you have a basic GNR underframe that does go with the D3D bodies. All that is left to do is add buffers (also available from my Shapeways Shop) and bolt detail. Oh and stepboards.

 

If anyone is brave enough to try and follow suit, feel free to post photos of your models.

[MikeTrice]

A small roll offcut from a sheet of roofing lead arrived today. A small section was cut off and glued to the underside of the central cradle:

 

The unit is now extremely stable through curves. This view from the top shows that it will just negotiate a Radius 2 curve:

[2750Papyrus]

A small roll offcut from a sheet of roofing lead arrived today. A small section was cut off and glued to the underside of the central cradle:

IMG_8802.JPG

 

The unit is now extremely stable through curves. This view from the top shows that it will just negotiate a Radius 2 curve:

IMG_8805.JPG

 

I have only just discovered this topic, having spent much of the summer away.  Your earlier thread on Diagram 3D prompted me to build a couple of the bogie coaches, which I completed using mainly butchered MJT components.  Even these had issues due to the narrowness of the prototypes - I had to trim the supplied solebars and the Fox bogies fitted to one are really too wide.  However, the Diagram 3D kits are good fun to build and this thread shows us how to tackle a 6 wheel underframe reasonably simply.  Thanks very much, and well done!