S7 Wheels - Australian Modeller

[Linton]

Hi,

My name is Linton and I model Australian, New South Wales Railways, era 1950s.

While I am generally a HO scale modeller, I have been collecting 7mm locomotive kits over the years.

Intrigued by the larger scale and the prospect of modelling to a scale standard, I joined the Scale 7 Group which has been helpful.

I recently asked a shop in the UK to reprofile a set of slaters driving and pony truck wheels to S7 for a kit I have started.

The wheels showed up last week however the drivers tyres are 3.57mm (0.141”) wide. This is not to the S7 standard of 3.2mm (0.127”).

Also, the centre boss of the wheel has not had any material removed making the face of the drivers far too wide to fit the valve gear in.

I emailed the fellow that machined the wheels and he said that’s as thin as he can go, stating that 0.012” is all that can be taken from the front.

After reading the slaters wheel reprofilling guidance supplied by the the S7 Group, I agree that 0.012” is all that can be removed from the front face however 0.012” should have also been removed from the back. This brings the wheel down from 0.151” to 0.127”.

He said the centre boss can not be reduced as the screw will bottom out. I thought the taper in the boss was required to be remachined to solve this.

I am a little disappointed as it cost me £135. From what I read, slaters wheels can be reprofiled to S7 however from what this fellow is saying they can’t be?

I do have the S7 tool. I guess I should of spent the money on soft jaws for my lathe.

Any advise appreciated.

Thanks,

Linton

 

[Tim Humphreys ex Mudhen]

Linton,
Try contacting Colin Dowling, eastsidepilot on this forum. his contact details are also in the S7 newletter. Colin is a professional loco builder who also provides a wheel turning service and has done loads to S7 standards. I'm sure he will able to help you.
Tim

 

[Linton]

Thanks Tim,

Will do.

Linton

 

[Tim Humphreys ex Mudhen]

Linton,
Forgot to mention that John Birch, Oz7mm on here is also modelling NSW railways in S7 I'm sure he would be pleased o make contact with you. I'm seeing him tomorrow so will mention your name to him in case he hasn't checked the forum.
all the best
Tim

 

[BrushType4]

Colin Dowling is your man Linton.

Welcome to the forum too.

 

[Linton]

Linton,
Forgot to mention that John Birch, Oz7mm on here is also modelling NSW railways in S7 I'm sure he would be pleased o make contact with you. I'm seeing him tomorrow so will mention your name to him in case he hasn't checked the forum.
all the best
Tim

Thanks Tim,

I had heard that someone on here was also modeling S7 Aus.

Nice and thanks mate.

 

[Linton]

Colin Dowling is your man Linton.

Welcome to the forum too.

Colin Dowling is your man Linton.

Welcome to the forum too.

I will try and make contact.

Thanks, the forum has been helpful in all of an hour!

 

[Overseer]

Linton
You haven't told us what the prototype for the loco is. There is a chance that the prototype tyres were up to 6" wide so close to your 3.57mm, especially if it is a larger loco. Because there are no 'self guarding frogs' in Australia there is not the absolute maximum width that the US has for example. The S7 standard width is for 5 1/2" wheels which is a common dimension for Australian loco driving wheels but not the only one, as also occurred in the UK. I have checked some VR wheel drawings but they don't have the tyre width dimension, just references to the detail profile drawing, but drawings for leading wheels show a range from 5" to 5 1/3". I have a section drawing for a NSW Baldwin 2-6-0 which has 5 1/5" wide flanged drivers and 6 1/2" wide unflanged drivers. So there was variety.

Slaters wheels vary in profile and thickness of the step in the rim depending when they were introduced, generally the more recent they are the closer to scale they are. The flanges on many of them are too narrow to allow taking anything significant from the rear face, converting to S7 really involves reducing the height of the flange. Reducing the thickness of the centre boss does not need high precision, just face it off. A sharp tool is needed for the glass filled nylon otherwise it will produce a rough surface. I either hold the tyre in reversed jaw 3-jaw chuck or use a low strength loctite to temporarily fix each wheel on a spare axle without a screw. From memory the countersink uses a 5mm drill, but I would need to check the taper angle as I may have used a Sutton Viper point bit with a sharper angle than a normal jobber drill. You will probably need to shorten the screws a bit to stop them bottoming out as well.

I did reduce the width of some Slaters wheels to 3.2mm recently and did lose most of the inner lip. The tyres are still held in place by the groove in the inside of the tyre, once painted it will not be a problem, or visible.

 

[nswgr38]

Hi Linton,
I am a 7mm and 1/32 scale NSW modeller from Sydney. What locomotive are you building? If you don't have the drawing for the prototype wheels that you are working with, I can help you with that. I have also turned down Slaters wheels to exact scale before quite easily. If you need any help, particularly with reference to drawings, please let me know.
Ross

 

[Linton]

Hi Linton,
I am a 7mm and 1/32 scale NSW modeller from Sydney. What locomotive are you building? If you don't have the drawing for the prototype wheels that you are working with, I can help you with that. I have also turned down Slaters wheels to exact scale before quite easily. If you need any help, particularly with reference to drawings, please let me know.
Ross

Hi Ross,

Thanks mate.

I am building a 36. I should really say, carrying out an experiment. I saw your other message confirming a tyre width 5.5 inches.

My problem at this point is that I payed $300 for the turned down wheels yet they are too wide, particularly the centre boss. I am also not happy with the workmanship as the chamfer on the front edge of the wheel is really uneven. This though is something for me to work out with the supplier.

My main question really is, can Slaters wheels be turned down to 0.127” wide as per the instructions provided by the scale 7 group. I was sure they could be, going by all I have read.

 

[Linton]

Linton
You haven't told us what the prototype for the loco is. There is a chance that the prototype tyres were up to 6" wide so close to your 3.57mm, especially if it is a larger loco. Because there are no 'self guarding frogs' in Australia there is not the absolute maximum width that the US has for example. The S7 standard width is for 5 1/2" wheels which is a common dimension for Australian loco driving wheels but not the only one, as also occurred in the UK. I have checked some VR wheel drawings but they don't have the tyre width dimension, just references to the detail profile drawing, but drawings for leading wheels show a range from 5" to 5 1/3". I have a section drawing for a NSW Baldwin 2-6-0 which has 5 1/5" wide flanged drivers and 6 1/2" wide unflanged drivers. So there was variety.

Slaters wheels vary in profile and thickness of the step in the rim depending when they were introduced, generally the more recent they are the closer to scale they are. The flanges on many of them are too narrow to allow taking anything significant from the rear face, converting to S7 really involves reducing the height of the flange. Reducing the thickness of the centre boss does not need high precision, just face it off. A sharp tool is needed for the glass filled nylon otherwise it will produce a rough surface. I either hold the tyre in reversed jaw 3-jaw chuck or use a low strength loctite to temporarily fix each wheel on a spare axle without a screw. From memory the countersink uses a 5mm drill, but I would need to check the taper angle as I may have used a Sutton Viper point bit with a sharper angle than a normal jobber drill. You will probably need to shorten the screws a bit to stop them bottoming out as well.

I did reduce the width of some Slaters wheels to 3.2mm recently and did lose most of the inner lip. The tyres are still held in place by the groove in the inside of the tyre, once painted it will not be a problem, or visible.

Hi Overseer,

I am building a NSWGR 36 Class, 4 6 0.

They have a tyre if 5.5 inches.

A tyre of 0.127” wide with a over axle measurement that fits between the valve gear is required. Therefore the wheels need to be turned to S7 General British Standard as far as I am aware.

Thanks,

Linton

 

[Oz7mm]

Hi Linton and welcome

I am the John Birch Mudhen refers to. I am slowly working through a pile of NSW kits but largely getting distracted by the Love Lane project also featured on this forum.

I can only reaffirm that Colin Dowling (eastsidepilot of this parish) will do an excellent job on the wheels which prompts me to send him those in my 36 kit.

I shall be interested to see how you get on with a S7 build. Will you be widening the frames (I haven't checked the drawings to see what the frame width is compared to the kit)

Please feel free to contact me off line for help with UK suppliers. I have done quite a bit of research over the last few years.

If I am correct you are the 4th S7 NSWR in the world.

John

 

[Linton]

Hi Linton and welcome

I am the John Birch Mudhen refers to. I am slowly working through a pile of NSW kits but largely getting distracted by the Love Lane project also featured on this forum.

I can only reaffirm that Colin Dowling (eastsidepilot of this parish) will do an excellent job on the wheels which prompts me to send him those in my 36 kit.

I shall be interested to see how you get on with a S7 build. Will you be widening the frames (I haven't checked the drawings to see what the frame width is compared to the kit)

Please feel free to contact me off line for help with UK suppliers. I have done quite a bit of research over the last few years.

If I am correct you are the 4th S7 NSWR in the world.

John

Hi John,

Great to hear from you.

I would not call myself a S7 modeller just yet, not until I finish the build ha ha.

My intentions are to widen the frames and while going through all the measurements is how I discovered the issue with my supplied wheels.

I have a few goals for the 36. I am quite heavily into building DCC Sound projects so would like to add working reversing valve gear. I would also like to actuate the brake rigging. I think it would be great to animate the loco to match the sounds. All things done before but as I said previously, it’s all a bit of an experiment so far.

As for the wheels, I need to sort out myvtooling and get to turning my own. At least I can only blame myself for shoddy workmanship!

I have sent Colin an email and await his reply.

I will check out Love Lane and will definitely be in contact.

Thanks for you reply.

Linton

 

[nswgr38]

Hi Linton and also John,

Linton: I have successfully turned down Slaters wheels as per the 2001 S7 instructions with wheels to go under a 17 class and also a 16 class (driving and other wheels).

Are you doing a round-boilered 36 or a Belpaire 36? I ask this because the driving wheels were replaced with wheels with a different profile rim for added strength. I have drawings for both, which show all the dimensions. I can send them if you would like. You will then know exactly how much to machine off the wheel in different places to get them more accurate.

John: I have done some work in 7mm scale exact scale (as opposed to S7). Am I one of the 4 that you know of?

Ross

 

[Linton]

Hi Linton and also John,

Linton: I have successfully turned down Slaters wheels as per the 2001 S7 instructions with wheels to go under a 17 class and also a 16 class (driving and other wheels).

Are you doing a round-boilered 36 or a Belpaire 36? I ask this because the driving wheels were replaced with wheels with a different profile rim for added strength. I have drawings for both, which show all the dimensions. I can send them if you would like. You will then know exactly how much to machine off the wheel in different places to get them more accurate.

John: I have done some work in 7mm scale exact scale (as opposed to S7). Am I one of the 4 that you know of?

Ross

Hi Ross,

It’s a belpaire, just the kit DJH produced for ModelOkits.

The drawings would be great if that’s possible.

I have a good friend that models exact HO in Sydney so he will be able to help through the wheel turning process also.

Thanks so much for the response. Glad to hear the method works as advertised for Slaters wheels.

Now to sort out the wheels I had sent to me.

Linton

 

[nswgr38]

Hi Linton,

I've sent you a message as the files are too large to upload here.

Ross

 

[Scale7JB]

Hi Ross,

Curious to know what the difference is between Scale7 and 7mm exact scale? Couldn't help but notice..

JB.

 

[nswgr38]

Hi JB,

I don't know the exact differences, but as far as I am aware, S7 isn't exactly a 7mm scaled down version of the prototype for every dimension. Of course, differing railway systems will have had different wheel/rail interfaces. When making or modifying existing wheels, I just make all the dimensions 1/43.5th of the railway drawing dimensions. I do the same for every item in the model, as far as practicable. I am not building operating models. Rather, I am endeavouring to make as exact a replica of the prototype that I can, whether it be in 7mm scale, or more recently, 1/32 scale. See the photos below, the first of which is 7mm scale and the second one 1/32 scale. In both models, the wheels have been scratchbuilt, like the rest of the model.

 

[PaxtonP4]

Hi Ross,

Curious to know what the difference is between Scale7 and 7mm exact scale? Couldn't help but notice..

JB.

The published Scale 7 wheel profiles is an exact scale reproduction of the wheel profile defined in BS276 - profile A. (as is the P4 profile).

Many different wheel profiles are used in the UK prototype with 15 different profiles used in the UK - not including light railway use such as trams.

Other countries use different profiles.

However the S7 published standard is what defines Scale 7.

regards

Alan

 

[Scale7JB]

I'd be very keen to hear how you get on with working leaf springs on the driving and carrying wheels..

JB.