Wrenn R1 Replacement Chassis and Detailing

[TurboSnail]

I'm embarking on a new project, to make a relatively simple to use replacement chassis for the Wrenn R1 class. I'm hoping to model Folkestone Harbour type formations in the future, so I need a few of them that I can make in a consistent manner with the same running properties, so they can be triple or quadruple-headed. I'm also planning on detailing the R/R1 classes (also in this thread), so I need the motor to be out of the cab and the allow visible daylight under the boiler. The wheelbase will also be scale accurate, at least where it is possible while still working with the Wrenn body.

 

The first prototype is being made now, printed on an FDM 3D printer at my Uni, so won't be the highest quality. It will get used to check the general arrangement is correct before ordering the detailed ones from Shapeways. I've got some Hornby 4F wheels to try it out with so I don't have to spend too much on it, and if it works well, I'll add some detail and make it into a 'dummy' unit.

 

 

Had to do a little bit of reinforcement on the motor mount as you can see in the picture below, mainly because FDM printing is very weak in the horizontal direction. I've also moved to a different (bigger) gearset since this image was taken due to the issue I had with it on my recent freelance diesel shunter project.

 

Edited April 17, 2018 by TurboSnail

[Skinnylinny]

Looking very promising! If you're going to be getting these printed by Shapeways, have you considered making them available to the public to buy? I'd rather like something a bit closer to scale to go under my Hornby-Dublo R1. which I've been repainting. That being said, are you going to do anything about the firebox bulge on the model body? Apparently it was put there to fit the motor in, where the prototype's boiler is a continuous cylinder into the cab...

[TurboSnail]

Looking very promising! If you're going to be getting these printed by Shapeways, have you considered making them available to the public to buy?

 

Certainly can! Would be nice if someone else is able to use it. Should be able to be adapted in CAD to suit different wheelbases for other classes as well, though I haven't looked into this yet.

 

That being said, are you going to do anything about the firebox bulge on the model body? Apparently it was put there to fit the motor in, where the prototype's boiler is a continuous cylinder into the cab...

 

Stay tuned, I'm working on that today, though my solution is probably not the most elegant... I'm eventually planning to mod some Wrenn R1s into unrebuilt Rs, which have a different boiler configuration, so would replace the entire boiler with plastic tube in that case.

[Joseph_Pestell]

Don't want to spoil your fun but, quite by chance, I have just seen that a replacement R1 chassis is already available from SEFinecast. So why bother?

[Wickham Green]

Don't want to spoil your fun but, quite by chance, I have just seen that a replacement R1 chassis is already available from SEFinecast. So why bother?

... not to mention the Branchlines one ....... but then a 3D-printed one saves an awful lot of soldering, doesn't it !

 

As for the firebox bulges, it's worth bearing in mind that the whole boiler assembly is significantly over-size .......... and, of course, the bunker's a little long too ( for no obvious reason ) ........................ maybe a complete new body might be an idea ??!?

[TurboSnail]

Don't want to spoil your fun but, quite by chance, I have just seen that a replacement R1 chassis is already available from SEFinecast. So why bother?

 

I'd found that one, and the Branchlines one, but for a number of reasons I'd rather make my own:

- 3D printing means no soldering needed, so I can't assemble it wonky or misalign anything (the main reason as I want to be able to make several with the exact same performance)

- I can use any motor (and probably flywheel) I want, which will be cheaper

- I can use any gears I want (I'm going for 1:60) and it won't need a separate gearbox etch

- The layout can be tailored to the body, especially useful if I'm making an R class with a different boiler, so I can make sure everything fits where I want it to

- I think I can make it cheaper

 

And finally... I'm one of those odd sorts who likes making stuff this way! CAD is fun (usually), why would I let someone else have all the satisfaction of designing it? 

[TurboSnail]

This poor R1 has had some butchery surgery done to it in an attempt to correct some of the more glaring issues. Still got to do handrails and possibly a basic cab interior.

 

Anyway, the chassis fits! Pretty well too, considering the fairly relaxed dimension tolerances of the PLA printer. The 4F wheels are slightly oversized and shouldn't have balance weights on, but they'll do for a test fitting.

 

Here's the thing though - does it look like an R1 to you? This is the stage where I need as much feedback (on the chassis) as possible so I can make the CAD model as good as it can be.

 

P.S. well done if you can spot the two deliberate errors!

 

 

 

 

[TurboSnail]

That being said, are you going to do anything about the firebox bulge on the model body? Apparently it was put there to fit the motor in, where the prototype's boiler is a continuous cylinder into the cab...

See the post above for that fix - I ground away the raised section, then covered the hole with paper, reinforced with PVA. It's not ideal as I didn't grind enough off in some places, but it's better than it was.

[hayfield]

This poor R1 has had some butchery surgery done to it in an attempt to correct some of the more glaring issues. Still got to do handrails and possibly a basic cab interior.

 

Anyway, the chassis fits! Pretty well too, considering the fairly relaxed dimension tolerances of the PLA printer. The 4F wheels are slightly oversized and shouldn't have balance weights on, but they'll do for a test fitting.

 

Here's the thing though - does it look like an R1 to you? This is the stage where I need as much feedback (on the chassis) as possible so I can make the CAD model as good as it can be.

 

P.S. well done if you can spot the two deliberate errors!

 

P1000094.JPG

 

P1000095.JPG

 

 

The southeastern R1 chassis is etched having the correct outline plus guard Irons at each end and spring detail, it also comes with the brake gear. The one downside is its a direct replacement for the Hornby Dublo chassis so has 2 lugs which stick into the slot in the rear bunker. Easy work round to install a chassis mount in the bunkes allowing the slit to be filled in. The other benefit is you can either use the motor mount bracket in the SEF kit or go for one of the gearboxes which seen superior 

 

If you could get the mainframe outline correct and arrange for brake gear/shoes would improve the looks. The other area of concern is the longevity of the axle holes if not bushed with brass bearings

[TurboSnail]

The southeastern R1 chassis is etched having the correct outline plus guard Irons at each end and spring detail, it also comes with the brake gear. The one downside is its a direct replacement for the Hornby Dublo chassis so has 2 lugs which stick into the slot in the rear bunker. Easy work round to install a chassis mount in the bunkes allowing the slit to be filled in. The other benefit is you can either use the motor mount bracket in the SEF kit or go for one of the gearboxes which seen superior 

 

If you could get the mainframe outline correct and arrange for brake gear/shoes would improve the looks. The other area of concern is the longevity of the axle holes if not bushed with brass bearings

 

There will be guard irons and brake detail on the next version, this one was a quick test print on a low quality printer that had no hope of recreating such detail accurately - it was just made to check the overall dimensions are right. The frame outline is correct though, at least according to the drawings I'm working from. It does look a bit sparse without the detail though, so I'm backing up the drawings by working from photos, particularly this one (copyright to railway-photography.smugmug.com):

 

 

I'm modelling the more detailed version at the moment, with bearings included. Finer details like piping and brake rods will be done separately with wire. I'm more aiming for a good running loco than for absolute accuracy as the body will still be Wrenn-based, so there will also be plenty of space to add weight to the chassis as well. 

[hayfield]

Here are two photos of the intermediate design, the new ones have brake gear and 2 piece coupling rods

 

 

So if you are copying the correct profile (I have no idea how correct the Hornby Dublo one is) then fine

 

 

The SEF chassis is a mainly screw together unit, for me the main benefit is the ability to use decent gearboxes, but they need enough room to fit, using this method allows for the motor to be out of the cab.

 

Still if you can print one with the hardware on then its a good step forward

[Nile]

Does the SEF chassis have the correct wheel spacing? Or is it a direct replacement for the HD chassis, with its wrong spacing? I assume the Branchlines chassis is correct.

[TurboSnail]

Here are two photos of the intermediate design, the new ones have brake gear and 2 piece coupling rods

 

 

So if you are copying the correct profile (I have no idea how correct the Hornby Dublo one is) then fine

 

 

The SEF chassis is a mainly screw together unit, for me the main benefit is the ability to use decent gearboxes, but they need enough room to fit, using this method allows for the motor to be out of the cab.

 

Still if you can print one with the hardware on then its a good step forward

 

Thanks, those photos help show the spring location, which is a bit tricky to see in photos. I have bits and pieces of the hardware already to measure up so I can get the locations as close as possible first time, so i shouldn't need to do too many test builds.

 

Does the SEF chassis have the correct wheel spacing? Or is it a direct replacement for the HD chassis, with its wrong spacing? I assume the Branchlines chassis is correct.

 

This conversation was had a while ago on my blog, the consensus being that the SE Finecast one is slightly wrong, but much better than the HD one. If you want super accuracy, the Branchlines one is the way to go, but then it makes the body's inaccuracies show up more obviously. So I'm going for something of a compromise, as I don't want to do major work to correct the bodies, but the wheel spacing will be correct. To be honest, if I wasn't detailing the body, I'd just re-wheel an original Wrenn chassis, as they seem to run pretty well (at least, mine does).

Edited April 6, 2018 by TurboSnail

[hayfield]

Does the SEF chassis have the correct wheel spacing? Or is it a direct replacement for the HD chassis, with its wrong spacing? I assume the Branchlines chassis is correct.

 

Nile

 

Its a straight forward replacement for the HD R1 chassis, one of the few revised kits to keep the RTR wheelbase rather than a new chassis, so spot on for the HD/Wren locos

[hayfield]

Thanks, those photos help show the spring location, which is a bit tricky to see in photos. I have bits and pieces of the hardware already to measure up so I can get the locations as close as possible first time, so i shouldn't need to do too many test builds.

 

 

This conversation was had a while ago on my blog, the consensus being that the SE Finecast one is slightly wrong, but much better than the HD one. If you want super accuracy, the Branchlines one is the way to go, but then it makes the body's inaccuracies show up more obviously. So I'm going for something of a compromise, as I don't want to do major work to correct the bodies, but the wheel spacing will be correct. To be honest, if I wasn't detailing the body, I'd just re-wheel an original Wrenn chassis, as they seem to run pretty well (at least, mine does).

 

 

The chassis is quite important to get nice and square so the wheels and coupling rods do not bind, are you adapting the chassis to use brass bearings, and what about coupling rods ?

[JSpencer]

There will be guard irons and brake detail on the next version, this one was a quick test print on a low quality printer that had no hope of recreating such detail accurately - it was just made to check the overall dimensions are right. The frame outline is correct though, at least according to the drawings I'm working from. It does look a bit sparse without the detail though, so I'm backing up the drawings by working from photos, particularly this one (copyright to railway-photography.smugmug.com):

 

1124 Stirling SER R class 0-6-0T-XL.jpg

 

I'm modelling the more detailed version at the moment, with bearings included. Finer details like piping and brake rods will be done separately with wire. I'm more aiming for a good running loco than for absolute accuracy as the body will still be Wrenn-based, so there will also be plenty of space to add weight to the chassis as well.

 

Note the photo is an R and not an R1. Should be fine for chassis details though and the Stirling cab versions for Folkstone. The chimney was replace with a new style in later SR days carried over into BR.

[TurboSnail]

The chassis is quite important to get nice and square so the wheels and coupling rods do not bind, are you adapting the chassis to use brass bearings, and what about coupling rods ?

 

Being 3D printed, it should be perfectly square! I'm designing the chassis to use Markits bearings with 1/8" axles and Scalelink wheels, and the centre bearings will be recessed to allow some sideplay of the middle axle when cornering. 

 

Coupling rods I'm not sure about yet, I'm going to try 3D printing them so they will be the exact correct length for the chassis, but if that isn't strong enough they will be modified from an existing RTR set. The test chassis shown earlier in this thread will have modified RTR coupling rods (from a 4F), so it will be a good opportunity to check it works. 

 

I recently finished a 3D printed 0-4-0 diesel shunter and the hardest part of that was getting the RTR coupling rods to work with the 3D printed chassis as there was a slight difference in length, hence why I want to 3D print them this time to get the lengths exactly the same.

Edited April 6, 2018 by TurboSnail

[TurboSnail]

Note the photo is an R and not an R1. Should be fine for chassis details though and the Stirling cab versions for Folkstone. The chimney was replace with a new style in later SR days carried over into BR.

 

The R1s have an extra box of some sort under the front left corner of the footplate, I haven't managed to identify what it was yet though. Do you know if the Wrenn model has the earlier or later chimney?

 

EDITED: because I can't tell left from right, apparently

Edited April 6, 2018 by TurboSnail

[cctransuk]

.... Markits bearings with 3/8" axles and Scalelink wheels .....

 

Now that I'd like to see !!

 

Regards,

John Isherwood.

[TurboSnail]

Now that I'd like to see !!

 

Regards,

John Isherwood.

 

Ah. This is why I don't use imperial any more... Is 3.175mm axles any better?

[Guy Rixon]

3.125mm axles would be better still.

[Horsetan]

...I assume the Branchlines chassis is correct.

The same chassis is also used in the O/O1.

[JSpencer]

The R1s have an extra box of some sort under the front left corner of the footplate, I haven't managed to identify what it was yet though. Do you know if the Wrenn model has the earlier or later chimney?

 

EDITED: because I can't tell left from right, apparently

There are two types of sandboxes on the R1s. The early above the running plate type each side of the smokebox as shown on the a Wrenn (ex Hornby Dublo) model. This type was also used by the R class too and carried when converted. I believe these are gravity feed. You then have the later type which only appears on some R to R1 conversions which appear as boxes just behind the front buffer beam, below the running plate on each corner (my O1 kit thread here has the same). These I believe were steam assisted.

There is some suggestion that sandbox type was based on whether or the smokebox was replaced when the Stirling boiler of the R was replaced by Wainwright boiler in the R1. Which sounds strange considering the Wainwright boiler sits a lot higher and would require Smokebox modifications either way.

 

The Wrenn model uses the tall chimney, the R1 having an original Wainwright type some of which were replaced by a Urie type. I am not sure if the wrenn loco carries the original or Urie or a hybrid of the two (the short versions used by the Rs were originally cast and those R1s which kept them, had them replaced by a new short design that was fabricated from steel sheet).

 

If you look carefully at Folkstone R1s in BR days, you will see 31069 with tall chimney, tall dome but fitted with short Stirling cab. In SECR days, 69 had the taller Wainwright cab. So a repair towards the end of her life probably saw the Wainwright cab replaced by Stirling cab taken from one of the cut down R1s used on the Canterbury and Whitstable line. R1s are interesting class fall of detailed differences. 4 chimney types, 2 dome types, 2 cab types, 2 safety valve types, 2 whistle positions and 2 sandboxes types. Few locos were ever exactly the same in this class.

 

One final thing, Wrenn did them in late BR crest or Large early crest but I have not seen a photo of one of these with those. I,ve only seen the early crest small version and British Railways written on the tanks.

Edited April 7, 2018 by JSpencer

[Steamport Southport]

Some definitely received the BR late crest.

 

Including 31337 which was the one HD did.

 

http://www.flickriver.com/photos/train-pix/5783841892/

 

http://www.rail-online.co.uk/p806047507/h1192AD71#h1192ad71

 

 

 

Jason

[JSpencer]

Some definitely received the BR late crest.

 

Including 31337 which was the one HD did.

 

http://www.flickriver.com/photos/train-pix/5783841892/

 

http://www.rail-online.co.uk/p806047507/h1192AD71#h1192ad71

 

Ah thanks for. It is clear from these pics that at least 2 of the class carried the late crest.

 

 

 

Jason