Invicta slip eccentrics

This topic has 8 replies, 4 voices, and was last updated 14 June 2013 at 22:03 by Sub Mandrel.

Viewing 9 posts - 1 through 9 (of 9 total)

Author

Posts
12 June 2013 at 20:54 #122117
nigel jones 5
Participant
@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?
Advert

12 June 2013 at 20:54 #6749
nigel jones 5
Participant
@nigeljones5
13 June 2013 at 10:02 #122148
Sub Mandrel
Participant
@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
13 June 2013 at 11:04 #122152
MICHAEL WILLIAMS
Participant
@michaelwilliams41215
**LINK**
13 June 2013 at 13:45 #122165
william Powell
Participant
@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
13 June 2013 at 14:00 #122166
william Powell
Participant
@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
13 June 2013 at 22:15 #122182
Sub Mandrel
Participant
@submandrel
Does invicta/canterbury lamb have gab gear? If so the gear LBSC designed for Lion/Titfield Thunderbolt should work.

Neil
14 June 2013 at 20:55 #122248
nigel jones 5
Participant
@nigeljones5
whats a gab gear?
14 June 2013 at 22:03 #122258
Sub Mandrel
Participant
@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
Author

Posts