Tethered kill switch source?


Thread Starter

Kevin Hammond

I have a piece of mobile railroad equipment that I would like to equip with a tethered e-stop, similar to what you might find on a jet-ski. If the operator should fall off the machine, I want the switch to open, and stop the machine.

I have checked boat dealers and motorcycle dealers, but the models they have look pretty weak. Are there any industrial versions of this type of switch available?


Kevin Hammond
Electronics Engineer
Norfolk Southern Corp.
Charlotte, NC

Jason Halligan

Hi Kevin,

Have you considered putting a pressure switch on the drivers seat (I'm assuming the driver is seated) or were ever else the driver may be positioned.

Just a thought.

Best of luck,
Jason Halligan.

Curt Wuollet

Hi Kevin

How about using a 1/4 in phone plug. These were designed in the good old days and robust ones can be had from switchcraft and others. Get an all metal one and short it or use a closed circuit jack and an open plug depending on which type you need. I did this on a 900 kawasaki motorcycle I had once, but that's another story. The only drawback is that they can resist a side pull. Running the cord through a loop a couple inches in front of the jack straightens that out. Or you can mount it high so everything is down.



Anthony Kerstens

Have you thought about a dead-man switch.

Robot teach pendants have a switch that operates if the operator releases the switch in his hand. They can be purchased as a separate item, I believe from Honeywell.

You could also use a safety gate switch with the tether attached to the operator mechanism, and a multiple pully arrangement to make sure that the operator is pulled from the socket regardless of the direction of tether pulling.

Anthony Kerstens P.Eng.
What about using a safety mat? If you are tethering the operator, it must be a fairly restricted area. A safety mat could be set up to
open contacts if the mat is NOT being stood on....

--Joe Jansen

Anthony Kerstens

The problem with cable pull switches in this application is the possibility of the cable connected to the switch could cause injury since it's not designed to break-away or pull out of a socket. And if you did have a cable that could break-away, would it do so without tripping the pull switch?

Anthony Kerstens P.Eng.

Michael Griffin

They use tethers on snowmobiles, and I can't think of any application which takes more abuse than a snowmobile. I would be surprised if your operators would present more of a problem for a tether than the average snowmobile rider does. A typical snowmobiling weekend often consists of consuming large quantities of alcohol and then driving like a maniac at ridiculous speeds through either icy cold or freezing slush while avoiding (not always successfully) trees, rocks, and the odd patch of open water. If your operators behave like this, then I think you have some rather more important problems to worry about than switches.

You might also think about the fact that a snowmobile tether is designed for this application while the various home made options are not. I would also imagine it is CSA (or other authority) approved for tethering people to machines. I'm not sure I would want to be attached to a dangerous machine by an unbreakable cord. This is intended as a *safety* device, so
you can't afford to learn about this subject by trial and error.

My advice would be to only use something which is intended for and approved as a tether switch, but to mount it carefully where it won't get hit accidentally. I've never seen them on anything other than a snowmobile, but you might check to see if some sort of similar switch is used in the forest products, mining, or other similar industry (I'm not aware of any though).

Michael Griffin
London, Ont. Canada
[email protected]

David Wooden

This could be defeated inadvertently when a mechanic unknowingly sets his toolbox down on the mat.

Just a thought...


Jeff Frischman

try a tongue operated safety switch, i know honeywell has a line of them. you should have no problem attaching the actuator to a tether
cord of some sort.

Jeff Frischman
Algood Casters Limited
605 Fenmar Drive, Toronto, Ontario, Canada, M9L 2R6
Tel: 416/749-7743 * 800/254-6633 (800/ALGOOD3)
Fax: 416/747-5671
email: mailto:[email protected]
website: http://www.algood.com
There's a kind of switch called Dead Man's switch used in mining machinery, basically to avoid runaway equipment when someone have a critical condition while operating.