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Kill Flap Montage

Kill Flaps and Switches

This page is still under construction so please keep checking back...

What is the difference?

Why do I need one?

So either you or someone else can stop the engine if something goes terribly pear-shaped! These devices are mandatory safety features required by nearly all the Pulling organisations and Sledges operating in the UK and Europe. If you are going Tractor Pulling you need to have one fitted to your Puller.

I hate to mention the obvious BUT we all have a 'Duty of Care' imposed on us when we go onto the track, which means that you as a Puller have to look after not only the Track Crew but also the spectators and the Track Crew have to look after you as well as the spectators. Just a little thought, but a fundamental one, especially in these days of litigation (no win no fee Lawyers)!

The four primary reasons for a Kill Flap or Switch are: -

  1. So the Sledge operator can bring the tractor safely to a stop if he or she feels the driver is no longer in full control of the run and is in danger of running off the track or the Puller is so badly 'out of shape' that an accident is imminent (see point 3 as well).
  2. I the event of the Hitch failing on the Puller or the Chain breaks on the Sledge, to prevent the (now 'unloaded') Puller careering off down the Track or into the 'out of bounds' safety zones.
  3. If for any reason the driver is incapacitated (either as the result of an injury or ill health) during the Pull so the Puller can be safely brought to a halt before it runs 'out of bounds' into the safety zones and presents a risk to either the track officials or the spectators (see point 1 as well).
  4. Should the throttle or pump malfunction, resulting in the engine 'running away' (running flat out with no way of shutting it down) at the end of the Pull, therefore enabling either the Sledge operator or a member of the Track crew to stop it. This is a particular problem with Bosch and Minimec Pumps which are being run 'on the rack', in other words without the governor.

This is what the ETPC Farmstock Rules have to say on the subject: -

"The kill switch must activate the air shut­off. A cable may be used for this purpose, but the flap must have a spring­loaded closing mechanism. A system to be deemed acceptable must at least prevent the building of boost. A hole with a maximum diameter of 25 mm* in the flap is allowed. It is recommended that a gasket/seal arrangement is used to shut off the air flow more effectively. All diesel engines must be equipped with an emergency shut down air shut off at the air intake, which can be utilized (operated) from the driver’s seat."

* For UK 'Independent' or Demonstration Pullers this hole would be far too large! I would suggest a 5 mm hole would be more than sufficient. Under the 'old' accepted UK convention this drilled hole would have been 1/8th inch or 3.1750 mm but most of you will have a 5.0mm drill in the workshop.

Why does the Flap need a hole?

Put very simply, to prevent your engine wrecking itself if the Flap is operated! Assuming the Flap forms an airtight seal and your power plant is revving at anything between 2,700 and 4-5,000 rpm when the Kill system is operated, air is no longer entering the cylinders but the mechanical injection pump is still working, fuel is being pumped in and the pistons are still 'sucking'.

There is also a very strong possibility the engine may start to scavenge some of the oil out of the sump. Both diesel and oil are liquids which do not compress particularly well which means the more liquid in the cylinders the greater the strain on the connecting rods and crank. Yes I am sure you can see where this is leading...

The purpose of the small hole is to let in just enough air to prevent damage occurring but not enough to allow it to continue producing power. When the Kill is actuated the engine should at best gracefully come to a stop or at worst drop to an idle. In the UK it is (generally) accepted the hole should be no larger than 5.0 mm.

The 25.0 mm maximum size stipulated in the ETPC Farmstock rules is far too large if applied to something like a classic 'Under 401', the 6.2-litre (380 cu in) Ford. Admittedly the engine would not be able to generate any meaningful power but would still merrily rev away to itself which is highly undesirable if the injector pump it stuck fully open!

What types are available?

Where can I get one?

Guillotine Kill Flap

Ready Made Guillotine

Peter Richardson in Lancashire can supply custom made Guillotine Kill Flaps and comes highly recommended by Chris Wilkinson of S.J. Wilkinson. Pete can supply custom Fuel Tanks, Intercoolers, Roll Cages, Wheelie Bars, etc.

Schlunder Trumpet & Kill FlapSchlunder - Metal & Pulling Parts. A German company however Matthias Hoffmann's web site is currently under construction however he does have a Facebook page for the business. As we are still in the EU, there is no duty to pay.







Antech Wire EDM Inc. Guillotine Kill FlapAntech Wire EDM Inc. - Robert Alves over in Canada can supply these beautifully made Guillotine Kill Flaps to order. You can also contact Robert via his his 'n hers Facebook page.







DIY Guillotine

Axminster Aluminium BlastgateAxminster Tools Aluminium Blastgate - Dave Williams says: - Remove threaded pinch bolt and drill through. Drill the swelling in the gate out and use a slightly opened up split pin. Add a couple of springs to snap shut. Not forgetting to drill a hole 25 mm or less in what will be the centre of the gate when it is shut.

These are only available in 100mm, 125mm, 150mm and 200mm.


Dust Spares Blast Gate Damper

Available in 63mm, 80mm, 100mm, 125mm, etc. up to 355mm. Dave Williams says: - Remove threaded pinch bolt and drill through. Drill the swelling in the gate out and use a slightly opened up split pin. Add a couple of springs to snap shut. Not forgetting to drill a hole 25 mm or less in what will be the centre of the gate when it is shut.


Butterfly Kill Flap

Ready Made Butterfly

Van der Waal Pulling Parts Butterfly ValveVan der Waal Pulling Parts Butterfly Valve - the only maker of the Butterfly-type valve I can track done on the internet, unless you know different of course...



DIY Butterfly

Exhaust Brake Butterfly Valve If your engineering skills are not that hot then you could always scour the vehicle recycling yards for something like an Exhaust Brake valve off a truck and adapt it to fit your inlet piping. On the other hand you could go down the Ben Ryder route...





Inlet Flap Kill Valve

DIY Flap

GenCat Stainless Steel Exhaust Flap

GenCat Stainless Steel Exhaust Rain Caps - You will have to sort out the spring closure and 'trigger' modifications for yourself.



Agrimech Stainless Steel Rain FlapAgrimatch Stainless Steel Exhaust Rain Caps - You will have to sort out the spring closure and 'trigger' modifications for yourself.






Steve Knight's Kill FlapThis is Steve Knight's Kill Flap Installation on his Holset Turbo which he as been using very successfully for a number of years. My thanks to Steve for the photograph...




'One Trick Pony' Guillotine Kill Flap

The Guillotine Kill Flap fitted to Rob Uphill's 'One Trick Pony'.