In 1989, staff at British Nuclear Fuels Sellafield plant asked me if there wasn't something "more 20th Century" than a wooden wedge to scotch rail vehicles safely. I did some research, and apart from a steel scotch onto which the vehicle had to be rolled (sometimes known as a "sabbo"), there did not seem to be anything that fitted the requirement. My parameters were -

1. It had to be easily fitted.
   
2. It should protect the vehicle from moving in either direction, and
   
3. It should be lockable, so that it could be incorporated into Permit to Work procedures

With nothing apparently suitable in the market, I mentally began to develop a picture of a pair of wedges, which closed together so that the lightly gripped the wheel and prevented motion in either direction. After a  few trial mock-ups, the result was Safety Scotch.

Since 1989, several hundred have been manufactured and supplied all over the UK from British Rail, Corus, Ministry of Defence, Marcroft, metros and freight operators. I ended up developing three versions -

SS1 - the original version, intended to suit all wheel diameters up to 4'6" (1372), weighs in 13kg and although eminently portable and  practical, spawned two lighter weight models

SS7 - a medium sized unit, specially suited for modern multiple-unit and freight vehicles, with wheel diameters around the 840 (new) range

SS-3 - a smaller unit, intended for smaller diameters such as metros, rail-mounted plant and narrow gauge applications

So, let's take an old and well-beaten SS1 and show how easy it is to fit.

Safety Scotch comprises two wedges (in s.g. iron) linked together by a telescopic mechanism. The 'master' wedge (top of picture) is fixed to the main tube, but the 'follower' wedge slides in and out. Both wedges have clips that go behind the wheel and thus prevent the Safety Scotch from being ejected in an impact.

Holding the over-centre mechanism in the open position with the left hand  (as shown above) Safety Scotch is presented first to the left hand side of the rail wheel and slid up to it, ensuring that the flange clip is behind.

 With the right hand, the follower wedge can now be swung into line and slid along the rail into contact with the wheel, again checking that the flange clip is behind.

In this position the knurled adjustment nut is visible beyound the end of the follower wedge assembly. If you are doing much the same wheel size again and again, it will require little or no adjustment. If however, you are jumping from (say) a vehicle with new wheels to one virtually at scrapping limits, you will need to compensate. With both wedges firmly against the wheel, wind the nut until it is just entering the end of the Safety Scotch.

Now pull the handle closed - you should feel a moderate over-centre effect and the lever springs itself the last part of the way. Do NOT over-tighten a Safety Scotch - firstly you may snap the linkage between the wedges, but secondly with low axleload vehicles you can effectively jack the vehicle up!

In the closed position,  Safety Scotch can be locked into place by tabs on the handle and master wedge. Since the adjustment mechanism is enclosed within the follower wedge assembly, it becomes impractical to remove it without the user's key.

So, scotched and secured from movement in either direction.

Now to take it off -

 Unlock and open the handle - this provides enough freedom for the follower wedge to slide completely clear of the flange.

Hold the handle open with the left hand.....

.....pull the follower wedge back out with the right...

... swing out from the right and then forwards and out left.

It seems as though every customer wants to know what happens if the scotched vehicle is struck by another, and I have witnessed some scary tests over the years. With a wooden wedge, the impact fires it out like a  bullet (I wondered at first why BR engineers stood so far back!) and the vehicle rolled away. With Safety Scotch, the vehicle rode up on to the wedge and having thus put its weight on it, the latter acts like a  sledge brake, bringing it back to rest. (Just how far it moves during this is impossible to predict - it depends on the impact speed, mass and rail condition - what can be said though is that it will be retarded.)

Other customers have tried to drive dmus or locos out of Safety Scotch, and to the best of my knowledge, no one has ever succeeded. You will of course drag the Safety Scotch along, but as a Class 156 driver at Craigentinny remarked 'you sure knew it was there'.

For prices, availability and further advice on models to use, please contact me.