Hornby 9F tender wheels - oversize?

[heraldcoupe]

I've had a Hornby loco-drive 9F knocking around without a tender for some time. I've now bought a secondhand tender minus the wheels and old ringfield casting which carries them in the loco drive version. I know the casting is known to disintegrate, so I set to making a pattern and casting a replacement in a high strength engineering resin.

I had thought about using original Hornby wheels, but as I didn't have any to hand, I built it around 2mm diameter axles so that I could fit Gibson wheels and axles. With 12mm wheels fitted to test (correct diamter should be 13mm), the tender sits about right. From images, the Hornby axles sit a lot higher and look a lot chunkier - to sit right , this must mean they are considerably oversize for the overall height of the tender to match the loco.

Does anyone have one of these available to check the wheel diameter for me?

 

Here are a few photos of the work in progress.

 

 

 

[heraldcoupe]

9 minutes ago, 313201 said:

I would say given the work you have done that the result is as good as can be.

 

I say that because looking at the 4th and 5th pictures, the area where the fireman would shovel coal from is at the right height from the footplate so the wheel diameter works well.

 

Yes, it's more of an idle curiosity thing really. 

 

Cheers
Bill.

[Brit70053]

It could be that the height of the Hornby product has a 'throwback' to the original tender drive model from Tri-Ang/ Hornby days. Models were produced which rode (I think) 2mm higher than scale in order that the tension lock couplings would not foul trackwork when negotiating gradient changes - think the inclined pier set up.

             You have created a closer to scale set up and the relationship between the loco and tender footplates is more correct. Well done.

 

            Regards,

 

                            John

[DCB]

I used 12mm spoked wheels, probably GR Wrenn on mine.   I found  the Hornby class 47 /37 etc Co Co Ringfield type trailing bogie chassis block is a direct replacement for the ring field power bogie frame and  I used one on the loco drive 9F when the original Ring Field motor shaped chassis crumbled to dust.

The 9F /BR 1G combo is very difficult to get right round the cab area,  The buffers should be in the 13mm to 13.9mm range and the tender cab slightly lower than the loco cab and the ridge on the tender cab at loco cab level, plus or minus a bit allowing for water coal load.  The Hornby tends to be 2mm too high over the buffers and about 3mm too wide over the cylinders

However the loco tender gap is far more pronounced on the Hornby than the full size and the Tender steps too far forward if you get the gap right.  I went for a 3 to 4mm gap between loco and tender and re positioned the steps to suit. It still gets round 2nd Radius curves.