Crankpin throw for an ex. LBSCR 'Terrier'?

[Steve Carter]

Hi, I am looking to build a Comet sprung chassis in P4 to fit under the Hornby LBSCR 'Terrier' 0-6-0 tank.

I have Alan Gibson wheels that need to have the holes drilled for the crankpin and I am looking to make a jig to help with this following the non-milling machine idea from "Buffalo" that can be found on here -

http://www.clag.org.uk/crankpin-drilling.html

Just a small problem, the Alan Gibson catalogue shows the crankpin throw as 8 inches (which is a scale 2.60mm in 4mm) but the Mike Sharman Wheel specifications for the modeller book shows the wheel stroke as being 18 inches, i.e. a 9 inch crankpin throw (3.0 mm in 4mm scale).

Can anyone please help with either the correct dimension or any advice/experiences of using these AG wheels?

Many thanks

Steve

[David Knight]

A quick check with a search engine gave cylinder size for Terriers as being 12"x20" with some having a slightly larger diameter up to 14 3/16" so it looks like either of your dimensions would work depending on how thick the piston was. Not sure if that helps but...

Cheers,

David

[Steve Carter]

Thank you for looking into this David.
I think I may have found an answer that I can move forward with!

I also posted this question on the Brighton Circle's forum and from the replies there it seems that even the GA drawings can't decide as one drawing shows the crankpin throw as 7¾ inches and another shows 8 inches!

I was reminded that Tim Shackleton has done a Hornby Terrier using the Branchlines chassis and he covers this in his book “Plastic-bodied locos”. A check revealed that he used the AG wheels having to drill the holes for crankpins. Tim says that the Terrier wheel crank throw is 16 inches. I believe this should read '16 inch wheel stroke', i.e. 8 inch crankpin throw. Tim goes on to say that anything greater may cause problems with the externally-mounted brake pull rods and that in P4 the rear crankpin nuts would very likely be clouting the cab steps! He says that the short crank throw is a feature of the Terriers and is one of their most characteristic attributes and I agree that this feature is very clear on this locos.

So, failing receiving any other ‘offers’ I will go with Tim’s view and use a 8 inch crankpin throw (that is also consistent with the AG catalogue) as it worked for him!!

Regards

Steve

[grovenor-2685]

They are inside cylinders so cylinder stroke has no connection with crankpin throw, the latter is commonly less than half the stroke. As in both of the options on offer.

i note no-one offered a correction to the Sharman book on this one (see http://www.scalefour.org/resources/wheelspec.html) perhaps that page should now be updated in line with the findings above. Perhaps one of the extant locos could be measured to confirm and give solid provenance.
Regards
Keith

[Terry Bendall]

I have a copy of Colin Binnie's book on the Terriers (Ravensbourne Press 1969) No dimesions for the crank pin throw are quoted in the text but a drawing of the wheel, with a scale included, would suggest 8 inches.

Terry Bendall

[SHurst]

The Tom Middlemass book "Stroudley and his Terriers" ( Pendragon) contains a detailed sectional drawing covering pages 24 and 25. This shows that the crank throw on the centre driving cranks is clearly marked as being 10 inches.
The axle centre to coupling rod crank pin centre position on the driving wheels is less than this and whilst difficult to read the printed dimension, it scales out at 8 inches.

Simon

[Steve Carter]

Thank you all for your very helpful replies. I appreciate your time spent to research and give advice.
I'm happy with a 8 inch crankpin throw for a "Terrier".
Cheers
Steve