Frame and spacer width

[Len Cattley]

Could somebody help me with the following questions? What would be the frame spacer width for S7 as the actual is 4' 1,3/4" and what size width would be the frames be if they are 1,1/8"?

Len Cattley

 

[Dog Star]

I think that you are asking for the scale width over frame plates and the scale width of frame stretchers if the frame plates are 1.125" thick.. if that is the case then the answers are:-

* width over frame = 1.144" or 29.06mm;
* width over frame stretcher = 1.092" or 27.74mm

Judging by the prototype measurements I think that you are considering a (large) GWR tender engine.

 

[Len Cattley]

Hi mate, is that 27.74mm between the inner frames or 29.06mm? No mate Rebuilt Scot.
Len

 

[Dog Star]

Using the information in your original post, then 27.74mm is the distance between the inner surfaces of the frame plates and 29.06mm is the distance over the outer surfaces of the frame plates. In case you want to know, the scale thickness of the frame plates is 26thou or 0.66mm.

To get these results:- convert the prototype measurement to imperial inches, then divide by 43.5 to give scale result in imperial... then multiply by 25.4 to get a scale dimension in millimetres. If you try this then you will see that there is a small dose of rounding in the answers.

Rebuilt Scot? Well it was meant to be a Castle .

 

[Len Cattley]

Thanks for your info, not very good at maths as you can see. Can I use this for S7 or would I need the frames narrower? I should have said that I want to build three kits in S7, Princess Royal, Rebuilt Scot and a Fowler Tank in B.R times. I just need to know what measurements to use for frame width and spacer size. I want to use the drawings from the NRM to get the measurements of these loco's so I can CAD them (if possible), I have the Wild Swan books but they are a bit basic. Stanier was (in my opinion) the best thing to come out of Swindon

Len

 

[Dog Star]

I have no experience with models of your intended prototypes so the only advice that I can give is to build some track to the likely radius of your layout and then construct a "basic" wheeled frame to find out what works and what does not. If you make the dummy frame a bit less than scale (say 28mm overall) then you can control the side-float of the axles using etched washers (Slaters) - adding / removing washers allows you to try different combinations of clearance between back of wheels and axleboxes.

 

[Len Cattley]

Thanks for the advice, will try that.

Len

 

[Scale7JB]

As Graham has mentioned its really down to the radius of curve that you would like the the engine to be able to navigate..

I generally build my engines as wide as possible, though I might have come a cropper on the F5 that I have just built, with the frames being too wide behind the radial trucks... There are a few fudges that I have in mind as I really don't want to strip the whole chassis down..

If you build a chassis you need to look for clearance between the wheels and the frames, not only because of wheels popping off the rail, but also electrically shorting out the chassis with wheels touching the frames, which is never a good thing..

JB.

 

[Len Cattley]

Hi JB I'm like you and would like to build them as wide as possible, I think that I will be picking-up from the tender as I can put as much detail in the loco chassis as possible.

Len

 

[Eastsidepilot]

29mm o/a frame width is, give or take a gnats, 4'-1 3/4", I think you'd be ok with that but bear in mind that the axle bearings/hornblocks may protrude beyond the face of the frames and with the min.b/b in S7 at 31.2 mm this realy determines the max. frame width, the max inside measurement being 0/a the hornguide faces, if that makes sense
Frame spacer width will be o/a frame width less 2x frame material thickness.

Col.

 

[Overseer]

The other thing to remember, and check for, is that the prototype frames were often not the same width for the full length. For example 4-4-0 and 4-6-0 frames often had the front end of the frames bent inward to provide more clearance for the leading carrying wheels on curves, and rear radial axles quite often had joggles in the frame between the trailing drivers and the carrying axle to provide extra clearance - on the ones I have looked at in detail are about 3" narrower across the rear part of the frame. I also have drawings showing the alterations required to allow a smallish 2-4-2T to operate around 160' radius curves - one of the changes was to double the offset of the rear frame.

 

[Len Cattley]

Thanks Col I think I know what you mean I'll have to make the axle bearings/hornblocks fit inside the frames. Hope to see you at Brightwell.
Len

 

[Scale7JB]

I also have drawings showing the alterations required to allow a smallish 2-4-2T to operate around 160' radius curves - one of the changes was to double the offset of the rear frame.

Love to see those...!

JB.

 

[Steph Dale]

Stanier was (in my opinion) the best thing to come out of Swindon

Len

Hehe; I think it was probably Harry Holcroft...

Steph

 

[Overseer]

Love to see those...!

JB.

Your wish .....


This was a small 5'3" gauge Beyer Peacock 2-4-0 design from the 1870s. Some of them were converted to 2-4-2T with a radial trailing axle but the more extreme alterations shown on this drawing were never carried out, some small 0-6-0 locos had the flanges removed from the centre axle instead to shunt the power station sidings.

 

[Scale7JB]

Many many thanks for that, the drawings have given me a few ideas..

I need to rebuild the F5 chassis, and looking at these drawings, I could chop down the frame sides, and move them inboard by the thickness of the frames, and that would be more than enough for what I need...

Thanks again, definite food for thought !

JB.

 

[mickoo]

Many many thanks for that, the drawings have given me a few ideas..

I need to rebuild the F5 chassis, and looking at these drawings, I could chop down the frame sides, and move them inboard by the thickness of the frames, and that would be more than enough for what I need...

Thanks again, definite food for thought !

JB.

Tut tut, that' s not the Scale 7 way now is it

I did something similar with my Fowler 4P, the front end frame width is near scale width (30.15mm) but behind the cylinders I jogged the frames inward to give an overall width of 28.75mm over outside faces which gives quite a bit of side play, in retrospect, too much. The Standard 5 is 29.5mm outside frame width with minimal side play but enough to get through point work.

 

[mickoo]

Len,

First you really need to decide on the overall width of your frames, take into account bearings and their overhang etc, once you have that dimension over the 'outside' faces then you need to define your material thickness, once you have that then your frame spacing will be the gap in between.

If you decide on the frame spacing first and then try to make everything else around that then "path of much difficulty you shall have young padwan".

The overall width will be defined by your layout or perceived minimum track radius you will encounter, I've opted for 6' radius and B7 point work. In greater detail, the overall width is determined by the type of bearings you use, the way they fit into the frames and the amount of side play you ultimately want.

In short, start from the outside and work inward, when you have eliminated and measured everything else the dimension you are left with will be your frame spacing.

Addendum; On reflection this is the order of importance for the path of enlightenment,

1: Define which bearings you are going to use and work out how far they stick out from the frame.
2: Define the frame material thickness.
3: Define your side play.

When you have measurements for all three above then your frame width can be worked out

 

[Len Cattley]

Thank-you master My intention is to to pick-up from the Tender, use an inside and outside frame to match the prototype and to do the same as Nick has done to his Princesses and to do the same to my Royal Scot, will have to work out what to do with the Fowler tank when it becomes available (hopefully) in Telford.

Len

 

[mickoo]

Thank-you master My intention is to to pick-up from the Tender, use an inside and outside frame to match the prototype and to do the same as Nick has done to his Princesses and to do the same to my Royal Scot, will have to work out what to do with the Fowler tank when it becomes available (hopefully) in Telford.

Len

Tender pick up will have little bearing on the loco bearings...so to speak, the majority of O gauge bearings...as far as I can ascertain...sit slightly proud of the outside face of the frames, on real locos, the ones I'm familure with they sit flush with the outside frame face or slightly inset, note, Britannias and WC/BB (there may be others) the frame sits smack bang on the middle of the bearing and they do stick out past the outside frame face.

34081 'Battle of Britain'

Note Bulleid welded horn guides.

45596 'Jubilee'

Note traditional riveted horn guides.

Whilst it's not obvious from the Jubilee shot the outside face of the bearing is as near worrying about, flush with the outside face of the frame.

You will need to follow the Jubilee practice as that's pretty standard across the locos your looking at.

Anyway, enough of these LMR distractions LOL, just finally picked up a copy of the Stanier 'Crabs' Irwell Press Book of series, some very tempting photos in there!