Jun 112018
 

Ashley, Chairman Essex North Panel, has requested help with the following please:

Remap Essex North have been asked to make a remote stop device for an older Kubota Mini Tractor. The Tractor is used on a Therapy Farm run by a very experienced OT.  Clients are occasionally allowed to drive the tractor once the supervisor is happy they are competent to do so and have had enough training. Currently if anything goes wrong or a dangerous situation arises the supervisor reaches over the drivers leg and pulls the stop control.  Tractor is quite old and diesel powered stopping it is possible only by cutting the fuel achieved by pulling the stop lever, this is common to most older diesel farm equipment. We have been asked to make a remote stop device, the solution we have currently is a cord (extending dog lead?) attached to the control in such a way that pulling it will activate the stop control. However, this solution is not really what is required they really want a completely remote system that the driver is not aware of , I think this is a driver confidence issue.  Remote we take to mean within 20-30M or so with safety person behind or out of direct sight of the driver whist still being able to assess the driving. Tractor is used on level ground albeit quite muddy at times.  We have thought of solenoid valves and car key fobs but all have issues with failing safe.  Has anybody made something like this?  Perhaps  a contact with a University or College could help we are open to any ideas or if you want more information do get in touch.

Thanks

Ashley  essexnorth@remap.info

  7 Responses to “Remote stop device for Kubota mini tractor”

  1. Wireless doorbell. A valve that’s normally closed which will remain open only if the bell push is operated every couple of seconds, or whatever the response time needs to be. To be fail-safe, it has to have a continuous stream of human-initiated commands in order to continue operation. The electronics at the “bell” end is quite trivial – indeed the typical run-time of the music may actually be just about right for giving the required response time. That output controls a transistor operated solenoid valve via a low pass filter.

    It’s possible to increase the “fail safe” still further by using two valves. One my possibly be used as a bypass valve – “short circuiting” the pump, dropping the fuel pressure to near enough zero. It’s also worth considering replacing a mechanical fuel pump (it the vehicle has one) with an electric fuel pump plus one way valve with a settable minimum operating pressure. No electricity to the pump then equals no fuel supply.

    I spend a lot of time in Norfolk, not that far from Essex and have used wireless door bells for many of these remote control situations – they are very cheap for quite a reasonable range!

  2. To make it failsafe the fuel solenoid should be of the type that requires constant power as suggested but also the remote should be constantly (or at least frequently) transmitting a signal to keep this power applied such that if the remote was dropped in a puddle, got out of range or something else happened to it the system would fail safe to turning off the solenoid.

    There are some simple 433Mhz, and 868Mhz based radio modules, the rest could be handled with an Ardiuno or similar micro-controller.

    • Good point Graham – some of those remote control relays reckon to have a range of 100M, but there might be real-life issues/obstructions which reduce the range and/or there would ideally need to be two remotes trained up to the receiver in case the battery in one fails.

      • It depends if they want true fail safe or just redundancy. Two receivers and two remotes would provide a lot of that but interference that affected both would not cause it to fail safe. Really it requires a risk assessment to decide what is needed realistically.

        Graham

        • Indeed. There are so many variables here and we can’t adequately assess without being there on a project like this.

  3. Member Ian Midgley, addresses the issues concisely, with any loss of remote signal causing fuel shut off, a fail safe system.

    If I may suggest additional safety, with a dual channel garage door controller, ( or two separate single channel ones) with a single fuel solenoid valve, and two individually controlled relays (should be positively guided type) with solenoid coil supplied through two sets of contacts in series.
    Therefore channel 1 controls relay number 1; channel 2 controls relay 2.

    The relays should be mounted to isolate them from any vibration, unless solid state ones are used.
    Machinery directive calls for two individually operated controls for most safety systems.

    You could also add a wrist cord, through plug-in, ref jet ski, if only for a little sense of danger if the clients under supervision are not daunted, or are able to appreciate this feature.

    Riding a tractor sounds a most enjoyable experience.
    Regards.

  4. Hi Ashley – you can get solenoid operated fuel valves for boats/cars, such that fuel only flows when voltage is applied. Examples here.

    https://www.seascrew.com/browse.cfm?FUEL-VALVE-ELECTRIC-12-VOLTS-SHUTOFF-ISOLATOR–SOLENOID-&p=0000006066
    https://www.electricalcarservices.com/anti-theft-solenoid-valve-for-petrol–diesel-fuel-lines-3.5mm-bore/p-2342

    What you could then do is wire the solenoid through the normally open contacts of a remote control relay of the type widely available on ebay. You’d need to test the operating distance for these.

    In both cases, you are applying power to both all the time the tractor is running. If either fails for any reason, it ought to fail safe. But of course, there is no absolute guarantee. Plus if this sits in the fuel line, you would need to consider how long the engine might still run on once the valve has been shut.

    Finally, the power to both needs to be through an ignition controlled feed or it could be left on by accident and drain battery.

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