Invicta slip eccentrics

[nigel jones 5Participant @nigeljones5]

I know the original had what were called slip eccentrics, but they clearly are not the same as those fitted to say a Juliet. Ive seen pictures of them but can anyone explain precisely how they worked and could I scale this to my 71/4 build?

[nigel jones 5Participant @nigeljones5]

[Sub MandrelParticipant @submandrel]

They are very simple. I have a slip eccentric on my Trojan, a simple vertical engine design by ET Westbury.

Instead of two fixed eccentrics in the positions fro forward and reverse and a slding link to 'choose' between them (in stephenson gear), the slip eccentric can rotate on the shaft between two stops. The stops are positioned to keep the eccentric in the right place for forward or reverse. It is set up so the stops drives the once the engine has started. The problem is, of course, they can start off in the wrong direction… and reversing is a matter of stopping and pushing the engine to start it in the right direction.

Personally I'd fit proper stephenson gear at 7 1/2" gauge…

Neil

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

**LINK**

[william PowellParticipant @williampowell50917]

Hi Fizzy

Invicta eccentric gear could be manually disconnect and the loco set to reversed with out having to push/set the loco back all from the foot plate (see the levers by the drivers knee in the first photo from the link). While it could be made too work i don't know how robust and practical it would be. I am slow building one in 5" gauge, i will have a look for a photo of the back axle, i visited the loco at her resting place in Canterbury Museum. Be aware that there is limited clearance between the axle and bottom of boiler. LBSC Canterbury lamb uses solid eccentric straps due to the limited clearance.

Will

[william PowellParticipant @williampowell50917]

Hi Fizzy

http://flic.kr/p/eL5zdB

Not the best photo, but i show the rear axle (looking from the front of the loco). From what i can remember the levers operate the shaft in from of the axle, these engage and disengage the stops. One each side for forwards and backward motion.

Will

 

 

 

Edited By william Powell on 13/06/2013 14:00:57

Edited By william Powell on 13/06/2013 14:01:51

Edited By william Powell on 13/06/2013 14:03:38

[Sub MandrelParticipant @submandrel]

Does invicta/canterbury lamb have gab gear? If so the gear LBSC designed for Lion/Titfield Thunderbolt should work.

Neil

[nigel jones 5Participant @nigeljones5]

whats a gab gear?

[Sub MandrelParticipant @submandrel]

Gab gear is a predecessor to stephenson gear. two eccentrics, but instead of a link with a sliding block between them, they have a simple link and open ends like a cross-section through a bell. the open ends face each other and when moved up or down one or the other engages with a pin on the end of the valve rod.

This wikipedia article tries to explain, but the illustration is of a later type with eth open bits on the valve rod, instead of the valve connecting rods.

Neil

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