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[derekwarner]

Guys...somewhere in the dim dark past I have read about "spring loaded steam throttle cushioning" ..mounted between the servo & the throttle

So even with proportionate RC control trimming of the servo arc of travel [stroke].....the "spring loaded steam throttle cushioning" ensures full desired stroke can be achieved....also with positive steam shut off.....but prevents any additional movement from what ever force or applied torque that could cause damage to the throttle internal mechanical stops or weakest part being the linkage arrangement

Am sure it was two captive springs that work in a push pull arrangement ......from memory the original concept came from Sandy Campbell....but cannot find any reference to it via Google

Any thoughts appreciated  ... Derek

[Jerry C]

Derek, think back to twin motor Helie Shaw steering gear with tele motor control. I'm sure there is a double spring buffer on one of the control/actuator rods. Will attempt a drawing when I've got a minute.
Jerry.

[Jerry C]

Derek I found a minute. This anything like it?
Jerry.

[derekwarner]

I think your sketch is very close ...thanks Jerry......two reactive elements  being load or force sensitive .....

Will wait & see if Sandy makes a posting before I send him a PM  ....

May have to go & raid the grandchildren's Christmas pen collections & steal a few springs as I have only 2 mm clearance between the horizontal axis of the servo control arm & the steam regulator arm to the underside of the engine entablature and 20 mm in length for the buffer to be installed................. Derek

[AlexC]

Hi Derek,
 
Here you go: -
 
Had to hunt around my old PC files to find it... lots of old drawing to yet be transfered to the new system.

You can fit this at either end of the pushrod.
 
Jerry's one is very neat, but might be more tricky to adjust the spring tension without a threaded insert at the floating end... something to think about.
 
Keep happy
 
Sandy.
 

[xrad]

I use a 'servo saver' system (dubro?) on the servo arm.  Great for positive shutoff and over-torqueing when closing or opening. You can see it working in Steam-up vid in my Brooklyn build thread.

[derekwarner]

Thanks xrad & Sandy [& Jerry]..........in the wee hours of this morning I found the e-mail from Sandy detailing his servo/regulator spring loaded device...it was from 7th November 2005 

His version notes using BIRO springs.......hence my previous mention that I would pinch some Christmas pens  .......knew I had read it somewhere.... Derek

[xrad]

update to my earlier post, I only use the spring on the 'closing' side of the servo rod. this cuts down on the 'play.'  Opening has more freedom in excess of the servo throw.