Magnetic Switch for pump

Design , Outfitting , Skegs , Rudders, Pumps , Sails , Modifications
Kels
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Magnetic Switch for pump

Postby Kels » Thu Nov 19, 2009 7:41 am

Hi All,

After a number of failed attempts to build my own magnetic switch - using Gnarly's instructions - I found a small, sealed magnetic switch from Jaycar (CAT. NO. LA5074) that suits the job perfectly. I encased the store-bought switch in sealant (just in case) and secured it as per Gnarly's instructions - works perfectly.

For those, like me, that are not experienced at mixing epoxy (as shown in Gnarly's plans) this may be a good option. I found that the switches I made were not "stiff" enough to prevent a small amount of flexing, which always broke the tiny reed switch just as I was fitting it! Very frustrating indeed, particularly on my 3rd attempt...

Of course, you still need the relay etc... as per Gnarly's instructions.

Cheers,

Adam

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Re: Magnetic Switch for pump

Postby gnarlydog » Thu Nov 19, 2009 9:22 am

Adam, I have seen those magnetic switches at Jaycar and one mounted on somebody's deck.
They work fine.
The magnet part (on deck) is not easily installed as a sliding unit to activate the reed below deck.
The one I saw had a Velcro attached to it instead of being a sliding unit. It did not look vey neat and the Velcro would let go occasionally.
I am sure that there is a way for making the Jaycar ready-made unit work, I just have not played around with it since I prefer my magnet sliding along the foredeck bungee cord.
The below deck part however seems OK and not that different than my DIY.
Are the wires long enough to reach the day hatch where the battery is located? splicing wires where you have often salt water (cockpit) poses challenges with sealing the wires.

You say that your epoxy DIY reed part of the switch (below deck) remained soft.
What brand epoxy did you use and what ratio did you mix it at? last but not least, how long did you cure it and at what temperature?
Some epoxies remains flexible for a few days in low temperatures but eventually go hard, unless your mix was not correct.
In summer temps my epoxy work goes off overnight, in winter it remains a bit flexible for a few days (unless I bring it inside and leave it at room temps).
Some manufacturers cure their epoxy work by "baking" it (higher temp curing).
I use 105 West System epoxy and a variety of hardeners and, depending on ambient temperature, I can make my epoxy stay "liquid" longer or shorter, depending on the work I have to do.
Full curing time will obviously be related to the hardener used.

While it all sounds awfully complicated it really is not. The epoxy mix however must be measured rather precisely (no eyeballing there) :-)

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Re: Magnetic Switch for pump

Postby Kels » Thu Nov 19, 2009 1:54 pm

Hi Gnarly,

I didn't use the magnet that came with the switch as I had already made my own (as per yours) - this works perfectly well with the store-bought switch. The wires were only about 20cm long so I spliced them into the system I had already made, where the other switch would normally be. All my joins are soldered, covered in sikaflex then heat-shrink - I've used this on previous kayak pumps and it seems to work well (no corrosion so far).

My switch is actually mounted in my day hatch with the magnet running along a deck bungee - its right behind my hip and seems to work well. I didn't want the magnet on the front deck as I often use a deck-bag there and it would be too easy to knock the switch on whilst fumbling in the bag.

My epoxy efforts were basically a shambles! The last one I made was left to cure for 2 days (both nice and warm) but my mix was obviously not correct - although the switch seemed hard, when I was gluing it into position there must have been just enough flex to break the glass of the reed switch. Luckily I tested the system before the glue set!

Cheers,

Adam

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Re: Magnetic Switch for pump

Postby mick M » Fri Nov 20, 2009 5:50 pm

I yous epoxy a lot, like Gnarly I prefer Weat, another alternative for small one of jobs wher only a small amount of epoxy is needed Sellys Araldite may be a good alternative, not the 5 minit stuf but the full strenth stuff , Iv even started yousing it to bed mast steps into Aluminium tubing with exelent resolts, after clening the tubing with acitone.

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Re: Magnetic Switch for pump

Postby rippunzel » Mon Nov 23, 2009 11:35 am

For those, like me, that are not experienced at mixing epoxy (as shown in Gnarly's plans) this may be a good option. I found that the switches I made were not "stiff" enough to prevent a small amount of flexing, which always broke the tiny reed switch just as I was fitting it! Very frustrating indeed, particularly on my 3rd attempt...


G'day Kels,

I was in the same boat (excuse the pun), and mixed the epoxy with varying levels of success. Solution I came up with was to set the reed switch inside a short piece of a clear plastic biro (pen) - using it as permanent 'formwork' - then it didn't really matter how long it took for the epoxy to go off (which I presume it has now!) Using the clear pen casing allowed me to see which way up the reed was, and also had a nice flat surface to use to mount it with . . . .

Regards
Mark

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Re: Magnetic Switch for pump

Postby Kels » Mon Nov 23, 2009 4:35 pm

Ah, that's thinking with your head Mark! Good one.

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Re: Magnetic Switch for pump

Postby ianv » Fri May 06, 2011 2:02 pm

Hi all, late into this thread. I've been trying (!) to fit a reed-switched bilge pump into my greenland T using the switch embedded in epoxy.I have used small rare earth magnets from jaycar. All worked fine in test, put it in the boat, switch failed.Now have the damn thing beautifully sikaflexed in but doesn't work Very careful not to flex the epoxy block. Relay is fine, everything else tested OK. So made another switch, and then tested it before ripping out the failed one. It promptly jammed on. Bit of research indicated that reed switches can become permanently magnetised, so I guess the permanent magnet I used was too strong. How do you tell?Would hate to have that happen at sea, so am thinking of going back to a boot toggle switch, I don't want to invest in a degausser!

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Re: Magnetic Switch for pump

Postby roadkillchef » Fri May 06, 2011 3:43 pm

Owch, that's a shame - I liked the simplicity of the magnetic switch, but now I am worried after hearing of your experience.

Have you thought of trying the air-activiated switch?
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Re: Magnetic Switch for pump

Postby JohnA » Fri May 06, 2011 7:49 pm

ianv wrote:reed switches can become permanently magnetised


Hi Ian,

it could be that the magnet is too strong or just left in close proximity to the switch for too long. Reed switches come in two configurations, Normally Open and Normally closed. In once case the magnet would turn the pump on and in the other it would turn it off. If you use it to turn it off then the magnet will be positioned over the switch the majority of the time and the switch is more likely to be permanently magnetised. I set mine up to be normally open and use the magnet to close the switch so the magnet is only over the switch when the pump is running. Not sure if it's the case with yours but thought I'd mention it anyway.

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saltypaddler
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Re: Magnetic Switch for pump

Postby saltypaddler » Fri May 06, 2011 7:56 pm

The air switches are okay but no good for your part of the world as they fail when you have extreme temperatures throughout the day. This happened on Bass strait (not in my kayak as I have the magnetic switch) the pumps would remain on, something to do with the cold air in the hose expanding throughout the day and activating the switch.

As for the toggle switches, the rubber boot will eventually perish making them useless.

I have installed countless magnetic switches in all my kayaks and my friends' kayaks and they work. I first came up with the prototype about 6 years ago (the one that Gnarly pinched the design from) and I'm still doing the same thing and they work just fine. Oh, and there is no need for any epoxy at all, just use a polyurethane (Sikka) for all sealing and sticking.

Cheers,
SP

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Re: Magnetic Switch for pump

Postby roadkillchef » Fri May 06, 2011 8:44 pm

Thanks Salty
The cure for anything is salt water: sweat, tears or the sea

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Re: Magnetic Switch for pump

Postby JohnA » Sat May 07, 2011 8:56 am

The problem with the pneumatic switches can be corrected by adding a very small bleed hole (pinhole) in the tubing. It allows any gradual pressure build up to escape but when the switch is pressed it won't let the air out fast enough to prevent the switch from activating normally.

When nicely executed, I think both systems have their merits, but the air switch has more moving parts and consequently a higher risk of failure, IMHO.

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Re: Magnetic Switch for pump

Postby paulw » Sat May 07, 2011 10:33 am

Hi Guys,

I use the rare earth magnets from Jaycar and haven't had a problem since I started putting the reed magnetic switch in the biro encasement. I don't use epoxy and just plug some skikaflex in both ends to hold it in place. This is mounted in the day hatch (with skikaflex) to avoid having it on my deck as the magnet can stuff with your compass.

Go the biro - and kudos to the person who came up with the idea!


Paul.

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Re: Magnetic Switch for pump

Postby gnarlydog » Sat May 07, 2011 11:06 am

I first came up with the prototype about 6 years ago (the one that Gnarly pinched the design from) and I'm still doing the same thing and they work just fine.

Salty, I never claimed to have "invented" the magnetic switch. The idea is too brilliant to have come from me. I am good at modifying things, rarely inventing them. I did see it first on your kayak, but I did refine the components a bit and made it more compact. I didn't come up with that idea and I made that public by saying: "To my knowledge, I was the first to publish the idea of the switch, even though it is not my invention." (ref: http://gnarlydognews.blogspot.com/2010/ ... atent.html)
On my blog you will find a lot of ideas that I bother documenting as open-source for the paddling community, however rarely any of those ideas or modifications are original designs.
I just take the time and effort to publish them instead of keeping them private.
Cheers

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Re: Magnetic Switch for pump

Postby saltypaddler » Sat May 07, 2011 9:17 pm

JohnA,
Great idea, wish I had thought of that :oops:

paulw,
I like the Biro tube a lot as it makes it possible to keep an eye on corrosion. Might try that on my next kayak (did I say my next kayak?) ;)

Cheers,
SP

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Re: Magnetic Switch for pump

Postby JohnA » Mon May 09, 2011 11:54 am

Thanks Salty, but I can't claim the credit, not my idea, unfortunately I can't remember where I saw it or I would pass on the credit. Is 44 too young for Oldtimers disease ?

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Megan
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Re: Magnetic Switch for pump

Postby Megan » Fri May 13, 2011 8:24 pm

I am glad this topic has come up as I have almost finished procuring the supplies and parts to install a magnetic switch, based on Gnarly's notes. Luckily I have found a biro case at home! I like Paul's idea of using Sikaflex to seal in the reed, especially as I am inexperienced with epoxy resin. I have not got my head around how to install the relay and the fuse, hopefully I will get help on this. I have a few other questions:

Could the magnet be enclosed in marine Sikaflex?

What have people used for the black sliding unit that holds the magnet?

I like idea of the switch on the front deck as the curvature would help keep the magnet in place and away from the reed when off. On Gnarly's page, the picture of the reed under the deck shows the wire going from the right to the left side. I assume that this is not needed if the wire was run along the left side of the kayak. Is my assumption right? Perhaps there is need to avoid deck area where the skeg wire ends is for the particular kayak in Gnarly's photos, which looks to be an Impex Montauk just like my sea kayak.

Cheers
Megan

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Re: Magnetic Switch for pump

Postby Kels » Sat May 14, 2011 7:07 am

Well, seeing as how this thread got resurrected - the Jaycar switch is still going strong.

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Re: Magnetic Switch for pump

Postby roadkillchef » Sat May 14, 2011 12:26 pm

Nice one Kels.

Any chance of a photo? Interested to see how you mounted the jaycar switch
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Re: Magnetic Switch for pump

Postby gnarlydog » Sun May 15, 2011 7:15 pm

Megan,
the reed switch could be enclosed in Sikaflex (or other type of Polyurethane sealant) and directly attached to the deck of the kayak, but I have never tried that. As long as one handles the reed with great caution when sealing it and not break it, it should be OK.
The underdeck image of my electric bilge pump install article is of an Impex Assateague: very similar to the deck of the Montauk.
The wired do run across the underdeck and you are right, there is no need for that.
I often use a plastic cap as housing to enclosed the rare earth magnet. I found that irrigation pipes black screw caps have the right shape and wide base for the magnet.
I have installed a Rule pump in a Montauk once and there was not a lot of room behind the seat. Since the owner didn't want to move the seat forward, the rear bulkhead had to be slightly modified to make room for the pump.
I have documented the process in this article:
http://gnarlydognews.blogspot.com/2009/ ... khead.html


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