Dapol Britannia minimum Radius

[Paul80]

Hi all

 

Hope this is in the correct section

 

I have just picked up an N-Gauge Dapol Britannia Oliver Cromwell DCC Factory Fitted, that looked to be un-used and other than needed the traction tyres replaced as the old ones had expanded during storage or exposure during its obviously short running life and now runs backwards and forwards fine.

 

The problem I am having is on the curves, I have googled this and it appears this loco is supposed to be able to negotiate 9 inch radius curves but on my layout because the tender is so close to the cab it derails on 20 inch radius curves but is fine on the 22 inch radius curves.

 

Anyone else have this issue with their Britannia? I ordered a new draw bar and drive shaft from DCCSupplies just in case someone had fitted a shorter version in the past, but the new ones are the same as the ones already fitted.

 

It does look nice on the straight with the tender so close the the cab but as soon as it hits the curve the tender and cab hit on the inside and the tender derails.

 

Anyone else have this issue with their Britannia, did you fix it, or are the instructions I have seen claiming 9inch radius navigation wrong, as mine didn't come with written instructions.

 

My Dapol 9F goes around the 20 inch Radius curves fine but that has a bigger gap between the tender and cab.  I suppose I could just run it on the outer loop but would rather fix it if a fix is possible.

 

Thanks in advance for any help with this

 

Paul

[Campaman]

A lot of tender locos have two different mounting holes for the drawbar, maybe the previous owner has moved it to the close coupled one if it has one.

[Paul80]

Thanks for the reply

 

Had a look and as far as I can tell their is only one set of mounting holes, 

[Kris]

I thought that this needed a 2nd radius curve.

[Paul80]

Sorry, what radius in inches/mm is 2nd radius ?

 

Paul

[Paul80]

Just googled it, Peco say second radius is 263.5mm mine is struggling with a radius of 508mm very odd if it's supposed to go around 2nd radius?

[Kris]

Are you measuring the radius as the complete width of the circle or half of it? 

[Paul80]

I am measuring from the centre of the circle to the track is that not the radius of a circle? The baseboard is 48 inches wide at that point so takes the 20 and 22 inch radius curves. 

 

Unless I have miss understood the way the term  radius is used ?

Edited September 26, 2019 by Paul80

[dpgibbons]

My Britannia will go round a 10 inch radius curve - but not with all the drivers on the rails.  

[steam-driven boy]

Hi,

I had a look at the original topic and found this by 70021 Morning Star:

https://www.rmweb.co.uk/community/index.php?/topic/20828-Dapol-britannia/&do=findComment&comment=1947401

Quote

Posted July 7, 2015 (edited)

.

FIX FOR BRITANNIA DERAILING ON 3RD RADIUS CURVES

 

[Thought I'd already posted this?] Anyway, I've recently had a bit of fun with my n gauge Dapol Britannia - 70021 "Morning Star" of course - constantly derailing on even 3rd radius curves. This was strange, as it had been running perfectly.

 

Eventually I traced the problem to the tender front being too close to the cab of the locomotive.

 

What happened is this: I always pick up both locomotive and tender, as a single unit, between my finger and thumb. Seemingly, the weight of the motor in the tender had caused it to drop away from the plastic bodyshell clips. It had then moved the bodyshell forwards, just a smidgen (so small it wasn't noticeable) then it reclipped itself in this incorrect position.

 

Seems there's a bit of free play in how the bodyshell clips to the tender chassis. Just enough to cause it to foul on the cab.

 

Anyway, the fix is to reposition the bodyshell so that the rear of the tender aligns with the rear buffer beam, then press it securely home. And, whenever you put this beauty on the track, just check that alignment hasn't moved before running. The Britannia will then happily negotiate 2nd radius curves.

 

Superb model.

 

 

Rick

Possible?

 

Regards, Gerry.

[Paul80]

Thanks for that, will have a look and report back.

[Karhedron]

My Brit struggled on 1st radius curves (227mm IIRC) but you should be OK on the radius you are using. I remember a post about some drive shafts having flash on them which causes problems on curves. 

 

https://www.ngaugeforum.co.uk/SMFN/index.php?topic=24487.msg263261#msg263261

[Kris]

9 hours ago, Paul80 said:

I am measuring from the centre of the circle to the track is that not the radius of a circle? The baseboard is 48 inches wide at that point so takes the 20 and 22 inch radius curves. 

 

Unless I have miss understood the way the term  radius is used ?

 

No you haven't but some do. I didn't want to assume either way. 

[Paul80]

Just checked the tender and it seems to be in the correct position eleven with the rear buffer beam.

 

I did find two other issues.

 

1 the drive shaft cup (don't know it's proper name) on the motor shaft had moved forward on the shaft, so might have been drive shaft lockup pushing the tender off, will give it a run tomorrow and report back.

 

2nd problem I found is that there is no electrical connection between one side of the driving wheels and the tender so it's relying on the tender pickups only although I had not noticed any running issues.

 

Both connecting wires are intact and when I checked with the meter there was no continuity between the driving wheels and the screw that the connecting wire connects to.

 

So next question how do I get the body off, I tried removing the screws at each end under the pony wheels but all that did was drop the chassis out and nearly had a disaster with the valve gear, how does the body come off these or should I just leave it as it is as it is running ok just picking up from the tender on one side only.

 

Thanks again for all the input and help with this.