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Heat shrink tube: pros, cons, how to, where to, alternative methods

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    Heat shrink tube: pros, cons, how to, where to, alternative methods

    Heat shrink tube is indispensable for making well insulated, waterproof (more or less) repairs/mods to electrical wiring on e-bikes, appliances, cars/boats, anywhere you find wires. Electrical tape is fine for a quick temporary fix but shrink tube is much better in terms of durability and waterproofing and it's much easier to use than tape.

    I use a lot of shrink tube and find it's not cheap. The worst deal are the boxes of tubing of various diameters and colors in pre-cut lengths. They seem convenient but I find they are not. And you pay extra for the box and the pre-cutting. I tend to use only the smaller diameters (3/32" to 3/8", 2.37mm to 9.47mm) and rarely use the larger sizes. When I've used up all the smaller sizes I always have half a box of larger sizes I will never use up for 2 reasons: I seldom work on wire that big and they are usually too short anyway. In fact even the smaller diameters are too short for many jobs which necessitates using 2 lengths when a single length would be more waterproof and durable.

    The only thing I like about boxes of pre-cut shrink tube is the variety of colors. The low quality of the boxes makes them useless for storing nuts/bolts/washers, fish hooks, etc.

    Fortunately there is an alternative. Shrink tube is available in 4' lengths in various colors and diameters on Amazon. They also have 50' rolls (least expensive per foot) and probably 25' rolls too. I can cut exactly the length I need for the job I'm working on which reduces waste. Sometimes I want a 1/2" length, sometimes I want 6" and I don't want to combine 2 X 3" lengths to get get 6".

    Heat shrink tube comes in 2 grades, maybe more:
    1. Standard grade is 2:1 shrinkage which means it shrinks to 1/2 it's original size. It seems it's available only in single wall (no glue inside) which means it's not very waterproof. This is the most economical and sometimes it's good enough.
    2. Marine grade is 3:1 shrinkaqe, double wall and more expensive. It shrinks as small as 1/3 original size. The inner wall is glue that softens when heated to provide better water proofing than the single wall variety.
    How waterproof is marine grade? None of the ads or spec sheets for various brands quote a recognised standard. They claim it's impervious even to saltwater but surely the seal depends on what the glue is adhering to. Perhaps it bonds well with one type of insulation but not other types. I suppose 2 tubes, one over the other with the top layer longer to cover and double-seal the ends of the inner layer would give much better protection against moisture but maybe that's over-kill?

    Would like to hear from other e-bikers regarding better ways to use shrink tube. Maybe there are other products that are superior to shrink tube?



    #2
    Yesterday, soldered my throttle wires, did not want to strip enough wire to make room for a sleeve of shrink wrap, so had to tape it, any suggestions?

    Comment


    • 73Eldo
      73Eldo commented
      Editing a comment
      There are products called liquid electrical tape that may be an option when there isn't room for tubing. Hot glue can also work well and adds some mechanical strength to a weak area which could have been the cause of the original failure you were trying to repair. With hot glue you generally want to use the basic more clear stuff. Some of the colors can be conductive.

    • AltaBrad
      AltaBrad commented
      Editing a comment
      Never heard of self-amalgamating no-adhesive silicone tape until just now. Gonna look for some because the difficulty in wrapping regular tape nicely (smooth and tight) arises from the adhesive. Seems no matter how careful I am the tape folds over and sticks to itself, argggh! Or it sticks to my fingers or the work bench at the very moment I don't want it to.

    • AZguy
      AZguy commented
      Editing a comment
      The liquid electrical tape is more or less permanent and doesn't come off cleanly like the self-amalgamating tape or heat shrink so for me I don't have much use for it... I usually have rtv laying around so would likely just use it any place the liquid tape seemed appropriate


      The self-amalgamating silicone tape sticks to itself (that's all it sticks to!) like no tomorrow so that's it's greatest challenge applying it. The second issue is that finger oils will slightly degrade the self-amalgamating property so I'll either wear gloves or I'll wash my hands right before applying, wet hands are better than oily.

      I discovered the stuff about fifteen years ago and it's a staple in my shop. It's really quite amazing and has its place. It sticks to itself instantly and over time fuses the layers together and if wrapped tight will be waterproof (I first heard of for marine applications)... but then when it comes time to remove any, a careful hand with a razor blade and there's zero residue... sometimes the last wrap might want to come loose, particularly if some oil gets in there so often I'll just shrink some heat shrink over the last wrap...


      I don't think I've used electrical tape since I discovered the stuff...

    #3
    For the occasional diy person those pre cut assortments are a good way to go because you get the sizes and colors and something that is easy to ship and store. The long boxes especially if you are just getting a few tend to get destroyed in shipping.

    I likely use more of the stuff than a lot of diy people do and I think I have gone through maybe 2 of the assortment boxes in 5 or so years I have grabbed some 4' pieces to refill some sizes if I had a big project that used a bunch but it was easy to do because I had a store I could walk into and buy one stick so I didn't have to buy a whole box or deal with having it shipped.

    If you want it to be reasonably waterproof you are best to get the type that has the glue like stuff inside that gets activated by the heat when you shrink it. I think they make em that way for small stuff. That is what you use on underground splices.

    Comment


      #4

      About self amalgamating tape

      Self amalgamating tape, also known as self fusing tape, is a self bonding rubber or silicone tape used for electrical insulation applications. When stretched and wrapped around itself, this product fuses together to form a strong, waterproof and electrically insulating layer. Self amalgamating tapes are commonly used for waterproofing, corrosion protection, jointing and repair of cables. Products are available for general purpose, low voltage and higher voltage applications.

      Self amalgamating tape characteristics:
      • Conformable
      • Moisture resistant
      • Non-tacky
      • Available in a range of colours and thicknesses
      • Easy to use and apply
      • Range of service temperatures
      • High stretch performance
      • Available in rectangular and triangular profiles
      • Excellent weathering resistance


      Comment


        #5
        Hey Eldo, thanks for tip, so much to learn, so little time. Reason for the solder job was to install a bafang throttle onto a KT cable because because the pinouts are different, got it done and took the newly all wheel drive bike out for a test spin today.

        Comment


          #6
          Originally posted by ynot View Post
          Yesterday, soldered my throttle wires, did not want to strip enough wire to make room for a sleeve of shrink wrap, so had to tape it, any suggestions?
          Sounds like you have the same problem nearly everybody has when using shrink tube... it gets warm and shrinks while you're soldering the wire and then you can't slide it over the solder. And you don't want to strip off more outer insulation so you can slide the shrink tube further away from the heat zone because the wire is already short or you want to keep the repair zone short and less visible. I struggled with too until I picked up a few tips from some experienced solder jockeys. I share those below. Now that I know about self fusing tape and liquid tape (thanks 72Eldo and AZguy) it's not going to be such a problem but I still like to keep the repair zone as short and smooth as possible even if I use self fusing tape. So the points that follow are written with shrink tube in mind but they'll help even with self-fusing and liquid tape.

          First, on small gauge wire such as used on a throttle, if you're doing like so many do and strip 1/2" of insulation from the conductors then twist the ends together then solder that twisted portion you're doing it.... well I don't want to say wrong... so let's go with "less than optimal". Twisting ends is good and perhaps even advisable on large wire that can get yanked or kicked around a lot because the twist creates a good mechanical joint that becomes even stronger when we sweat solder into it. Examples would be a 110 volt extension cord, the cord on a toaster oven, TV, etc. A throttle cable isn't likely to get yanked that hard because if you're like me you've got it secured along the handlebar. It doesn't need maximum mechanical strength. Most people want a repair zone on something like a throttle cable to be short, free of lumps and bumps, as unnoticeable as possible. And that's what I attempt to tell you how to do below.

          The objective(s) are to strip off minimal outer insulation but not shrink the shrink tube prematurely. Obviously reducing the amount of time the iron is in contact with the wire [u]when the shrink tube is on the wire{/u] would help. Reducing the distance the heat conducts down the wire helps too. The solution in a nutshell: bare only 1/8" of copper on the conductors and tin the bared ends before sliding the shrink tube onto the wire. Tinning puts into the wire 90% of the solder and heat required for a top quality joint before you slide the shrink tube on. We adding the last 10% after the shrink tube is on the wire but it's only 10% and it happens so fast the odds of prematurely shrinking the shrink tube are near zero. That allows positioning the shrink tube closer to the solder zone which means we don't have to remove as much outer insulation.

          Proper wire tinning is an art in itself. It's far easier to demonstrate than explain so maybe find a Youtube vid that shows how to do it. There are visual cues that tell you when you've done it right and when you have not. One vid is worth a thousand words.

          When the wire ends are tinned they are too stiff to twist around each other and at 1/8" long they're too short for a twist even if not tinned. All you need to do is position them side-by-side (not end-to-end!), touch your iron to the end of solder wire on the spool (not the tinned wire ends) which will put a drop of new solder and a wee bit of new flux on the iron. Then quickly (before the new flux burns away completely) touch that drop to the top of the side by side wires. In a split second the hot drop will melt the solder on the wire and flow into it. That's when you lift the iron slightly and pull it away. Don't drag it off the wire else it will bounce the wire which will shake the still molten solder off the wire. Lift first then pull back. Then allow the joint to cool and freeze on its own, don't blow on it.

          The insulation will have melted and pulled back slightly but if done quick you'll end up with no more than 1/4" of exposed conductor. So you need only 5/16" long piece of shrink tube which means you don't have to strip off as much outer insulation just to keep the shrink tube away from the heat.

          A solder helper hand is a huge aid to positioning tinned wires side-by-side. Furthermore, the alligator clips are heat sinks. If you position them between the wire ends and the shrink tube they will soak up a lot of heat that will otherwise go down the wire to the heat shrink tube. That allows you strip off even less outer insulation :)

          After the joint freezes check for candles. A candle is solder that pulls away from the joint and follows the hot iron for a short distance as you raise the iron off the joint. Eventually it separates from the iron but it freezes before it coalesces with the molten solder on the wire. The result is a pointy protrusion sharp enough to poke through shrink tube or tape resulting in a possible short to other wires in the bundle. Let the joint cool completely so it doesn't melt entirely then quickly brush the iron over the candle. Don't hold the iron on the candle just brush over it quickly. You might have to brush more than once. If you give it just the right amount of heat the candle will melt and coalesce completely into the other solder without heating the entire joint to melting point at which point the 2 wires will separate. Sometimes you give it only enough heat to take the sharp point off the candle leaving a rounded and shorter candle that is far less likely to poke through the shrink tube. That's usually good enough but it's your call.

          Now check for mavericks...single stands that break away from the main herd for whatever reason. Don't bother trying to melt a single maverick back into the main herd just trim it off. Fingernail clippers get in nice and close and trim it down to near nothing. If that's still too much for your tastes then brush it with the iron to melt just enough solder off the surface of the joint and drag it over the remainder of the maverick.

          3 or 4 mavericks is a different story. If you trim that many on small gauge wire you lose appreciable wire thickness and ampacity. Melt the joint apart and redo it. Maybe not so important on a throttle where I suspect not a lot of current flows continuously but on a battery to controller wire it's very important. Headlamps also draw current continuously so it's important there too. A turn signal is not continuous so less of a concern.

          Comment


            #7
            FWIW if when soldering wires together and the tubing shrinks from the heat, generally speaking the iron isn't hot enough or at least doesn't deliver the heat good enough - if it's a good iron the time it takes to solder should be shorter than the time it takes to heat up nearby things... not always possible but usually the case...


            Regardless, like and skill, soldering etc. takes practice...

            Comment


              #8
              "doesn't deliver the heat good enough"

              Yep. Don't need a $500 iron for that, a $20 rheostat controlled 45 watt unit will do. In fact for wires they even work better because they have a larger heat reservoir than a high dollar iron. After that it's simple:
              1. clean and tin the tip frequently
              2. tin the wire ends before you slide the shrink tube on and position the wires together

              Comment


              • AZguy
                AZguy commented
                Editing a comment
                3. Good flux is your friend

              • AltaBrad
                AltaBrad commented
                Editing a comment
                3 a) Or your worst enemy.

                If you burn it then it often creates porosity in the joint. Porosity decreases tensile strength and reduces conductivity.

              • AZguy
                AZguy commented
                Editing a comment
                3. Good flux [used properly] is your friend

                Didn't think it needed that but there - flux is essential for good flow... used properly will greatly speed up the time it takes to flow and make a good joint so less time heating

              #9
              The right iron for the job I think is the most important. Digital and rheostats don't have to mean anything. I see it all the time where people get hung up on needing something with a display on it and thinking that will just magically let them solder anything. Many irons have a lot of issues getting the heat from the element to the tip as well as controlling it. Some applications it doesn't make much difference and others its pretty critical.

              The context of what most people do with an E bike I don't think there is one that covers all. Most ebike install and repairs are wires which tend to be either small or big. Doesn't help that the quality of the wires tends to be bad (easy to melt insulation). What you need to solder XT90's and 10 gauge wire isn't going to work well for small wires like going to a display. What works on the display wires isn't going to do a good job on the battery wires. A car is probably an easier one to get a one size fits all because you don't end up with really small wires and don't solder the big ones.

              I have tips for my Metcal setup that can do both small and large but no way I would recommend someone tinkering with E bikes spend that kind of money. Just the tips are $30 each. I think if someone was asking me what to get for E bikes I would tell them to just go to a home depot sort of place and get something in the 30 watt range which should be less than $30 then maybe the big old classic 100w weller gun which I think cost around $50 these days. Those are easy to get and cheap as well as easy to get tips for and will handle what most people run into around the house and garage. They don't need a Hakko FX station or some USB powered kit. I would not confuse them with talking about or getting any sort of flux other than to be sure they are getting proper rosin core solder meant for electronics. Ending up with solder and flux meant for plumbing is really bad for electronics and something that seems to happen a lot.

              Comment


                #10
                Originally posted by 73Eldo View Post
                ...The context of what most people do with an E bike I don't think there is one that covers all. Most ebike install and repairs are wires which tend to be either small or big. Doesn't help that the quality of the wires tends to be bad (easy to melt insulation). What you need to solder XT90's and 10 gauge wire isn't going to work well for small wires like going to a display. What works on the display wires isn't going to do a good job on the battery wires. ...
                The Hakko I've been using has been great for large and small - with a large chisel tip (~$5) I'm soldering 8-10AWG quickly and cleanly (albeit at high temperature) and with a micro-smd tip (also ~$5) have been doing 0402 parts (teeny tiny, about the size of coarse ground pepper) on PCB's very well too... I've also done the centers of UHF coax connectors and 32AWG wires and soldered down shields to thick ground planes - unsoldered the same shields too (really tough job!)

                This is all with a iron I got for $85 at the time (likely closer to $100 today?) with a huge assortment of tips that are ~$5 per

                So while I agree that the iron is likely the number one concern, I respectfully suggest that not only can one iron do everything an electric bike might need, but also do it at a reasonable cost


                And while like I don't think it should need to be mentioned that flux needs to be used properly I guess I also don't think we should need to say it shouldn't be plumbing flux... I not so respectfully think if people don't ask or better yet do their research they end up with what they deserve... Oh well...

                OTOH I see folks that have been soldering for hobby purposes (vs. professionally) for a long time not realize the tremendous benefit using flux brings... so while I don't mind pointing out something they may not already know I'll leave it to them to either ask, or better yet do their research on what types and how best to use...

                FWIW having said that I've been using an activated liquid rosin flux (there are *many* types of flux that are suitable however) in a dispenser bottle (I've got several tips for this) - another tip folks might not be aware of is that you can get tips for the dispenser bottles that have a teflon sleeve inside the metal tip and these are great in order to prevent them from clogging (the metal only tips, especially the really thin ones, get clogged very easily with rosin flux and are nearly impossible to clean)... regardless it's very easy to apply just enough flux to penetrate and wet the entire joint... I clean the residue with a liquid flux remover however 91-99% isopropanol will work ok too...

                Comment


                  #11
                  Is that still a current model Hakko? $100 isn't bad if they still make it or something that can actually do the same job. I was never a huge Hakko guy so maybe they did better than Weller as they 'upgraded' their line. I don't think Weller did very good. I remember trying out a replacement unit for one I had forever and it was terrible. I ended up on ebay to find tips for the old one.

                  Hakko is also apparently the most often counterfeited so like most things this day if the price seems too good to be true or the seller seems a little sketchy its likely a fake. There was one of the more popular models a few years ago that was so bad it barely worked at all unless what you were working on happened to be grounded at which point it got good an hot because the circuit was so bad you had pretty much a direct line voltage connection to the tip.

                  I have not spent a lot of time looking at whats currently out there but last time I did it seemed to be one of those things were there wasn't really a middle ground anymore, you can get junk or really overpriced stuff that doesn't do that much better than some of the cheap stuff. Weller used to make some really good and cheap irons but I think the irons went out of production maybe 25 years ago and now you can't even find the tips anymore. I still use mine occasionally when I have something too big to put on the bench and I'm too lazy to take apart and move the Metcal (which is most of the time).

                  Acid flux is a bigger problem than I ever imagined it would be. I have seen it on some e bikes I have helped others with. I also saw it when I was into DIY EFI were users had to assemble their own ECUs. That was before things like youtube and cheap online storage so you did have to look a little harder to find information but it was out there. Many people I helped were trying to solder stuff on boards with open flame and acid flux.

                  Comment


                    #12
                    Originally posted by 73Eldo View Post
                    Is that still a current model Hakko? $100 isn't bad if they still make it or something that can actually do the same job.
                    That's a super good question - it was six years ago that I bought mine and after having it for a good while and getting time on it wrote up a review here: https://electricbike.com/forum/forum...is-it-any-good

                    I just looked and Hakko is still advertising it on their site for $110 list and amazon has them at $105 - life is pretty good!

                    HAKKO and artist Toshiyuki Kita partnered in the creation of the FX-888D product design, the number 1 soldering station on the market. A light weight, compact station, with an ergonomic handpiece. ESD safe and high HEAT resistant.


                    https://www.amazon.com/Hakko-FX888D-.../dp/B00ANZRT4M

                    Originally posted by 73Eldo View Post
                    I was never a huge Hakko guy so maybe they did better than Weller as they 'upgraded' their line. I don't think Weller did very good. I remember trying out a replacement unit for one I had forever and it was terrible. I ended up on ebay to find tips for the old one.
                    Decades ago I used wellers and then the metcal's, jbc's and other "professional" brands... I don't think weller has done a great job of keeping up with technology and they do seem to have poorer thermal conduction and control at the tip than the others I've used. The cheap hakko isn't on par with some of the "professional" stations but then again they are 10x the price. It still has excellent temperature control and the element goes way into the tip and they have really good thermal conduction... if I was going to critique them compared to the higher end stations I'd say that the time to heat up initially isn't rocket ship fast (still nowhere near as slow as the wellers I've seen lately) and it would be nice if it had an automatic sleep mode, but I've gotten really good at the habit of turning it down to a "sleep" power level and for the cost it's no surprise the feature is missing. I haven't yet burned up a tip in the six years I've had it and I use it often professionally. The really big selection of tips (30!) and that they are very inexpensive (hakko lists $5-$8, amazon <$10) is a really big plus.

                    Originally posted by 73Eldo View Post
                    Acid flux is a bigger problem than I ever imagined it would be. I have seen it on some e bikes I have helped others with. I also saw it when I was into DIY EFI were users had to assemble their own ECUs. That was before things like youtube and cheap online storage so you did have to look a little harder to find information but it was out there. Many people I helped were trying to solder stuff on boards with open flame and acid flux.
                    I get the nasty feeling you may be able to teach them about flux... maybe... and as mean as it may sound they're likely better off leaving the soldering and probably many other tasks requiring some mechanical aptitude to others

                    Comment

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