hot rope cutters - what would you pay?

[Alicatt]

I bought a Portasol professional gas soldering iron in 1992, I have used it and still am using it and the hot knife is excellent for cutting and sealing ropes, it cost me £32 back then and it has given me great service as most of my jobs using it were in places without mains power, I also got a box of different sized tips for soldering, it also has a blow torch and a hot air attachment great for heatshrink tubing etc.

Tools of my trade:


The hot knife is in the RS box second from left

 

[LadyInBed]

blow torch (creme brûlée torch (from Aldi) - essential equipment in every galley - or workshop)

Agree, essential equipment ?

 

[davidpbo]

Silly money here:

HSGM Rope Cutter - Portable Hot Knife - Cuts Sailing Ropes, Industrial Ropes: Amazon.co.uk: DIY & Tools

£20 seems cheapest

12 volt hot knife rope cutters - Google Shopping

My sums mean I can make one (if I buy materials in bulk) for about £3. Sell on ebay or my own website for say £9 with 3 year guarantee.

But it looks like a frayed knot idea. Back to tending to pot plants.

Edit: £6 for a gas soldering iron (if it does the job) is cheap. I have a cheapish £15 one that just about does all I want on windy days and a cheaper one that is only of use in still weather (and even then is pretty useless - "Workzone" I think). Neither have a blade for cutting rope.

I have been making soft shackles for fun and had a few electrical bits in the car to knock together a rope cutter and hence my idea grew. At least I have a cheap rope cutter until I run out of rope...

Cheers

Not necessarily silly money if you want a good quality product and/or are using it in a commercial environment. For me personally I use a 50 yr old Weller Soldering gun with hot knife attachment or 100w + Orego gas iron with rope cut bit.

 

[Sailingsaves]

Anyone else mentioned that you need to consider product liability protection? Either through insurance or clever , creative trading structure. Simplest would be to pretend to be a Chinese company and change the name and ebay account every few weeks.

This is a good point. I stopped being limited company a few years ago and no point creating one for a tiny product such as this.

I will make a better looking prototype and stick photos up. Others can make it then. It is not an invention as too much prior art exists. It is simply a useful product for me now and anyone else that makes one.

I don't think I will be able to sell it because of the liability risk.

It can work from a 12 volt 'cigar' lighter socket or from 3 AA cells and cut rope up to 40mm thick and webbing, sails, canvas etc, Heat is within 3 seconds.
Most boats have 12v or can kick down to 12 v.

One may run out of butane gas. Soldering irons etc take more than 5 seconds to heat up.

AA cell version useful and a slight USP perhaps, but as not selling, just a UP (unique point) now.

The pot plants are flourishing on the window sill however, so all is good.

 

[Sailingsaves]

Not necessarily silly money if you want a good quality product and/or are using it in a commercial environment. For me personally I use a 50 yr old Weller Soldering gun with hot knife attachment or 100w + Orego gas iron with rope cut bit.

Relatively speaking.

And I don't mean the Special Theory of Relativity.

£3 to make a product that works better than a £30 device and from 12 volts or even 3 Volts.

I have one of these for large soldering jobs and it is quick to heat up and a good product (I did need to re-new the bit last year), but needs 240 V AC

https://cpc.farnell.com/weller/8100ud/expert-soldering-gun-100w-240v/dp/WL8100UD

 

[Black Sheep]

I will make a better looking prototype and stick photos up. Others can make it then. It is not an invention as too much prior art exists. It is simply a useful product for me now and anyone else that makes one.

That sounds like a good plan - essentially Open Source hardware. No money in it, but kudos, altruism, and the potential for others to help improve the item.

 

[Dipper]

Buy blades? I sharpen hacksaw broken blades. I have used them, with a handle to cut rope when the blade has been heated with a blow torch (creme brûlée torch (from Aldi) - essential equipment in every galley - or workshop) Jonathan

For cutting ropes I use an old Junior hacksaw blade held in mole grips and heated red hot on the gas hob.

 

[STATUE]

What is the cheapest hot rope cutter you know of?

How much would you pay for a:

1) 12Volt version that plugs into cigar socket with a long length of thin flexible wire (in case you wished to work on deck)

2) A 3Volt portable device that works via 2 AA cells (they could be rechargeable AA cells at a lower voltage)

A friend is letting me stay in their spare room and I was bored so have made myself a hot rope cutter whilst I tinkered with lines and soft shackles.

Thinking of making a webpage selling such devices to stave boredom and make pennies or pounds.

I don't think this breaks any forum rules because I am not selling on the forum.

Thank you

Use every day items, that you can use for other things = gas blow torch & wallpaper scraper.

 

[thinwater]

Until you have used a hot knife to cut Sunbrella, you don't know what you are missing. Also carpet and sail cloth. No fraying, just zip and done. Ropes and bungees are just a side benefit to the real deal. Every poster that has used one knows what I mean.

 

[FlyingGoose]

I chose the wife’s best cutting knife from the galley , heated on gas hob until red and cut , no problems .
Apart from the wife.

 

[ShinyShoe]

I clearly don't spend enough on my butane irons as they always struggle in wind.

12v is fine on a yacht. Less use in the dinghy park. Can't always get the car alongside without effort.

My preference would be USB chargable. With LiIon so it is still charged 3 months later when I next need it...

 

[Sailingsaves]

I will get around to it, but I have not made prototypes worthy of displaying yet.

The wire has to be correct length to match the voltage; too short a wire at 12V and wire is destroyed.

Too long a wire at 3V, 4.5 V or USB 5V and the wire does not get hot enough.

Simple calculations and simple to make if I had access to my workshop.

I have working prototypes at all voltages, but they look awful.

Will get around to it.

 

[thinwater]

Just FYI, my 150W soldering iron with a wire cutting.hot knife blade installed operates at about 0.8V, 150 amps (I just put a gauge on it). In that case, 3-4 inches of coat hanger wire is about the right resistance. At 12v, you'll need about 6-8 amps (fewer watts would work). You will need some manner of current limiting resistor. After that, a stainless strip (a common strapping material) about 0.5mm x 4mm x 20mm should do the job. The strap alone will pass way too much current. I did a few quick tests, but did not have a suitable resistor surrogate handy

 

[Sailingsaves]

Just FYI, my 150W soldering iron with a wire cutting.hot knife blade installed operates at about 0.8V, 150 amps (I just put a gauge on it). In that case, 3-4 inches of coat hanger wire is about the right resistance. At 12v, you'll need about 6-8 amps (fewer watts would work). You will need some manner of current limiting resistor. After that, a stainless strip (a common strapping material) about 0.5mm x 4mm x 20mm should do the job. The strap alone will pass way too much current. I did a few quick tests, but did not have a suitable resistor surrogate handy

I use less than 5 A and the metal (3 part alloy) glows red hot. Cuts rope, webbing in intricate patterns like the proverbial.

At 5V and 4A I am using 20W

Circuit breaker is set at 5A .

I can use AA cells, lead acid, USB power bank as someone asked.

I have not used a resistor.

I could make a version that is variable current and heat by using one extra component costing £1.

I just made a video with my ugly prototypes and I have moved away from the melted rope fumes.

Ugly prototype 1 with 3 AA cells

 

[thinwater]

I use less than 5 A and the metal (3 part alloy) glows red hot. Cuts rope, webbing in intricate patterns like the proverbial.

At 5V and 4A I am using 20W

Circuit breaker is set at 5A .

I can use AA cells, lead acid, USB power bank as someone asked.

I have not used a resistor.

I could make a version that is variable current and heat by using one extra component costing £1.

I just made a video with my ugly prototypes and I have moved away from the melted rope fumes.

Ugly prototype 1 with 3 AA cells

I mentioned the soldering iron numbers just for people's interest. Most commercial rope cutting devices use only 20-40 watts.

Very cool and it solves the stated problem (cuts rope), but I like an need a tool to do a few more things:

• Melt the ends a bit more. For example, when cutting shock cord, you need to melt a bit of a button.
• Hot knife for cloth. For me, I use this function 3 times more often and for FAR more hours that cutting a few lines. It is far more vital. Nearly every sewing project, including sail work, will benefit from a hot knife. Also cutting carpet, webbing, chafe gear... the list goes on and on.

You need to try a hot knife to realize how much you need it.

 

[Sailingsaves]

Well I wasn't ready but here is proof of concept.

Remember, I wasn't ready yet.

 

[Sailingsaves]

I mentioned the soldering iron numbers just for people's interest. Most commercial rope cutting devices use only 20-40 watts.

Very cool and it solves the stated problem (cuts rope), but I like an need a tool to do a few more things:

• Melt the ends a bit more. For example, when cutting shock cord, you need to melt a bit of a button.
• Hot knife for cloth. For me, I use this function 3 times more often and for FAR more hours that cutting a few lines. It is far more vital. Nearly every sewing project, including sail work, will benefit from a hot knife. Also cutting carpet, webbing, chafe gear... the list goes on and on.

You need to try a hot knife to realize how much you need it.

This should cut and seal fabric and webbing.

I have no proper rope with me as I am sort of homeless at moment.

 

[thinwater]

Well I wasn't ready but here is proof of concept.

Remember, I wasn't ready yet.

Again, very cool. I small tool like that with a handle would be handy.

I agree, comercial hot knives and rope cutters are rather over priced. I think I lot of people would be interested in a reasonable 12v version.

 

[TernVI]

Just FYI, my 150W soldering iron with a wire cutting.hot knife blade installed operates at about 0.8V, 150 amps (I just put a gauge on it). In that case, 3-4 inches of coat hanger wire is about the right resistance. At 12v, you'll need about 6-8 amps (fewer watts would work). You will need some manner of current limiting resistor. After that, a stainless strip (a common strapping material) about 0.5mm x 4mm x 20mm should do the job. The strap alone will pass way too much current. I did a few quick tests, but did not have a suitable resistor surrogate handy

The 'solder gun' is more subtle than first meets the eye.
It's basically a transformer, with a multi-turn primary and a single turn secondary, of which the 'tip' is a resistive part.
But cunningly, the temperature is somewhat controlled. The power is reduced as the tip heats up.
Is that just the resistance of the metal tip changing?
I'm not sure!

You need the power to go into the tip, not any current limit resistor.

I'm surprised nobody has spoken in favour of whipping the rope either side of the cut and just cutting it with a proper knife.
Much better for some applications.

 

[thinwater]

Here's a butane version for $20. No idea if it works, just came across it by accident.
http://www.zarcor.com/products/hotblade/index.php