Friday, 30 August 2013

Order, Order!

As well as restoring Sentinel 7109 ("Joyce"), I've also been discovering her history. Sometimes information comes to light through a deliberate search but occasionally someone turns up a real unexpected gem.

One of these gems was kindly sent to me by John Hutchings from the Industrial Locomotive Society. There are three images which can be magnified for reading by clicking on them (and 'back-arrow' to return). They show the original works orders (7109) for the manufacture of "Joyce".
Page 1
Page 2
Not forgetting the 'sprockets'!
In amongst the information are the figures for the number of gear teeth and sprocket teeth. These allow an interesting calculation of speed per engine RPM.

Crankshaft pinion: 45 teeth.
Countershaft pinion: 102 teeth.

Axle sprockets: 27 teeth.
Countershaft sprockets: 15 teeth.

Engine speed to axle speed ratio:

102/45 x 27/15 = 4.08:1.

Wheel diameter: 36 inches.
Wheel circumference: Pi x 36 = 9.42 ft.

[Feet/mile = 5280].

MPH = (RPM/4.08 x 60) x 9.42/5280 = 13.1 at 500 RPM engine speed.

So we can expect Sentinel 7109 to be speeding along at 13.1 MPH when its engines are at 500 RPM!

Other noteworthy points in the orders show that there was an injector fitted originally and that no Weir boiler feed pump was included; it would appear to have been ordered and fitted later. The boiler was a single 'experimental' type as opposed to some earlier double-engined locos that had used two 100 HP boilers!

I'm also enquiring as to whether similar information is available for the two Radstock Sentinels.

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