It seems I garbled part of one of the sentences below.

The catch wings are mounted above the beam in such a way as to stop the
piston passing through either the bottom or (sometimes) top of the cylinder.
It is, of course, physically connected to the beam rather than as my
previous sentence might have inferred being separate from it.

Interestingly, I was once at Kew Bridge when their 90 inch engine came
indoors at such a rate that the catch-wing caught the spring beams fairly
spectacularly. The whole engine house seemed to be rattled.

Re the comments about Cruquius, it strikes me that with that engine the
beams were mounted radially around the engine house so now I'll have to look
at my old photos to try and decide how the protection was arranged on that
machine :-)

Lastly, on the subject of controlling Cornish engines, there was another
component employed to control the time the engine paused at one, or
sometimes both ends of its stroke. This was in the form of a cataract device
that using a small tank of water and a float was attached to the valve gear
to inhibit release of the appropriate quadrant for a period of time.
Typically these were employed to pause the engine at the end of its out-door
stroke to give sufficient time for the pump valves to close before going
indoors again. Not all engines had these devices but they were quite common,
if not always obvious as they were often hidden away in the 'cockpit' below
the engine room floor.

During the nineteenth century there was considerable discussion from the
1860s onwards as to the suitability of Cornish engines for waterworks
service. Some of this material is likely to be reproduced along with the
article on the Sims engine at Crofton in a forthcoming edition of the ISSES
annual journal Stationary Power.



Paul Stephens
IT Manager
DS Smith Corrugated Bristol
Tel. 01275-551023 (Direct)
Tel. 01275-375311 (Switchboard)
Fax. 01275-374939
Mob. 0787-644-6777


-----Original Message-----
From: Paul Stephens
Sent: 08 September 2003 13:48
Subject: Re: Spring beams


The devices designed to stop a non-rotative beam engine from destroying
itself seem to go back almost to the earliest days of the beam engine.

The two components that normally appear on these engines were the catch
wing, mounted above the beam with a fixed above the beam, usually to a pin
pretty much in line with the centre line of the piston rod.
The spring beams were made of large baulks of timber designed to stop the
engine coming too far in-doors and smashing the bottom out of the cylinder.
Generally, but not always, a similar arrangement was provided on the
outdoors (pump end) end of the beam to stop the piston coming through the
top of the cylinder, or damage to the pumps.

Usually a replaceable piece of timber was attached to the top of the spring
beam to take the brunt of the strike from the catch wing. Sometimes
India-rubber was used instead as can be seen on at least one of the engines
at Crofton. Close examination of most of the surviving non-rotative engines
will show marks indicating that the spring beams would e stuck fairly often.
This would occur either during starting when the engine would be worked by
hand, or during a mechanical failure when something broke.

In some cases additional equipment was added to the plug-rod operated valve
gear to provide additional means of stopping the engine should a over-stroke
occur.


Paul Stephens
IT Manager
David S Smith Corrugated Bristol

David S Smith Corrugated Bristol
First Avenue, Portbury Way,
Portbury, Bristol, BS20 7XR
Tel: +44 (0) 1275 551023 (Direct)
        +44 (0) 1275 375311 (Switchboard)
Fax: +44 (0) 1275 374939



-----Original Message-----
From: Newman, Phil [mailto:[log in to unmask]]
Sent: Monday, September 01, 2003 08:57
Subject: Re: Spring beams


Thanks Andrew, now I understand what they're for but where exactly were the
cross arms or arch heads located? Were they fixed to the beam? On the famous
Perran Foundry cross section for example (printed in Barton and elsewhere)
the cylinder end of the beam on the in-house stroke is below the top of the
spring beam. Is the cross arm not shown on this drawing?

Thanks for your help

Phil Newman





-----Original Message-----
From: Andrew Hurrell [mailto:[log in to unmask]]
Sent: Friday, August 29, 2003 6:54 PM
To: [log in to unmask]
Subject: Re: Spring beams


The spring beams on a non-rotary beam engine are there to act as a buffer.
If the engine hits the bottom of the cylinder on the 'in-house' stroke or
the top of the cylinder (and bottom of the pumps) on the 'Out of House'
stroke there is a good chance that the engine will smash the cylinder
casting. This could be because of something like a pump rod breaking or the
valve gear not operating properly.

Cross arms ('Arch Heads' ?) raised above the ends of the beams line up with
the spring beams. When the engine is working correctly, the arch heads
should stop just short of the spring beams.

The Dorothea engine, because the pump rods are missing, is sat on the spring
beams inside the engine house. The beams in this case start under the
bearings and can clearly be seen to be smaller than the structural beams
below.

Regards

Andrew

----- Original Message -----
From: "Newman, Phil" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, August 29, 2003 11:10 AM
Subject: Spring beams


> Dear list,
>
> Could someone please provide a concise definition of a Spring Beam. Most
> diagrams of engine houses in the usual sources show them and the sockets
are
> usually quite evident in the structures but there precise function is not
> fully clear to me.
>
> Thanks in anticipation
>
> Phil Newman
>


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