Adding length to a pole - 1 to 2 cm

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m2qItMot
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Adding length to a pole - 1 to 2 cm

Postby m2qItMot » Fri Feb 27, 2015 4:56 pm

I know this may sound strange or even ridiculous, but it should be fairly simple, when I think about it.

I cut my new skating poles and there is s good chance that I got them to the perfect length, but ... I have some doubts that I might be better off with a centimeter or two more. Most likely because I am still used my old poles and their handles and their weight ... will ski for a while to see how it goes. Might be just fine.

Anyway, I have the two cut-off pieces, each about 14 cm long, so I figure that if I can get some short piece of carbon or fiberglass pipe whose outer diameter matches the inner diameter of the pole shaft, it should be easy and reliable to extend the top by a tiny bit, by epoxy-ing a splice.

Has anyone done that? I am wondering where I can get such piece of splicing pipe.

The I.D. of the shaft under the handle appears to be 14.5 mm. Fischer RCS poles.

Thanks!

PS: I am pretty sure that the guys who fix carbon things, like bike frames and what-not can do anything - but it might be unnecessarily expensive.

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Re: Adding length to a pole - 1 to 2 cm

Postby JeffOYB » Fri Feb 27, 2015 5:03 pm

I've done it. I use sections from the leftover chunk I cut off earlier as spacers to re-add length to a pole. The grip holds everything in line. Never felt a wiggle. Maybe I did glue in a splicer-section of some kind. It's been a decade since I grew 2 sets of poles. They've been fine since, tho!
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Re: Adding length to a pole - 1 to 2 cm

Postby nxski » Sat Feb 28, 2015 6:39 pm

You don't want to try adding much in length since it will put more torsional strain on the top of the shaft. Also, expect that the small piece will get stuck in the handles and is quite difficult to get out if you want to reuse the handles.
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Re: Adding length to a pole - 1 to 2 cm

Postby Chris » Sat Feb 28, 2015 7:23 pm

nxski wrote:You don't want to try adding much in length since it will put more torsional strain on the top of the shaft.


This won't put any additional stress on the shaft, or at least anymore than a correctly cut to length shaft would have. It will put more stress on the grip though unless a stiff enough insert is used to join the two pieces of shaft. This does not necessarily mean the grip will break, but it will be more likely to fail.

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Re: Adding length to a pole - 1 to 2 cm

Postby nxski » Sun Mar 01, 2015 1:32 pm

Chris wrote:
nxski wrote:You don't want to try adding much in length since it will put more torsional strain on the top of the shaft.


This won't put any additional stress on the shaft, or at least anymore than a correctly cut to length shaft would have. It will put more stress on the grip though unless a stiff enough insert is used to join the two pieces of shaft. This does not necessarily mean the grip will break, but it will be more likely to fail.


It will do both, I have tried lengthening shafts and once you add more than 1-2cm (depending on the depth of the handle) you start putting torsional stress on the top of the shaft and can cause the carbon to compress and it will usually fail where the shaft meets the bottom of the grip. A similar situation can also occur when you overheat the carbon fiber.
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Re: Adding length to a pole - 1 to 2 cm

Postby jt10000 » Sun Mar 01, 2015 2:41 pm

nxski wrote:
Chris wrote:
nxski wrote:You don't want to try adding much in length since it will put more torsional strain on the top of the shaft.


This won't put any additional stress on the shaft, or at least anymore than a correctly cut to length shaft would have. It will put more stress on the grip though unless a stiff enough insert is used to join the two pieces of shaft. This does not necessarily mean the grip will break, but it will be more likely to fail.


It will do both, I have tried lengthening shafts and once you add more than 1-2cm (depending on the depth of the handle) you start putting torsional stress on the top of the shaft and can cause the carbon to compress and it will usually fail where the shaft meets the bottom of the grip. A similar situation can also occur when you overheat the carbon fiber.
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Re: Adding length to a pole - 1 to 2 cm

Postby Chris » Sun Mar 01, 2015 5:31 pm

nxski wrote:It will do both, I have tried lengthening shafts and once you add more than 1-2cm (depending on the depth of the handle) you start putting torsional stress on the top of the shaft and can cause the carbon to compress and it will usually fail where the shaft meets the bottom of the grip. A similar situation can also occur when you overheat the carbon fiber.


Torsional stress would come from twisting along the axis of the pole. In order to make this stress you are essentially grabbing both ends of the pole and twisting it like you are wringing out a towel. I would think this stress is relatively low in a ski pole under normal use. The glue holding things together would likely fail long before the shaft fails due to torsional stress. Maybe you are thinking of bending stress (Mc/I)

The stress where the shaft enters the grip does not change depending on if you have a correctly cut pole, or one with a 1 or 2 cm spacer stuck in the handle. Research shear moment diagrams and keep in mind the point the load is applied does not change. Compressive stress doesn't change either.

Overheating the carbon fiber would be a different failure mode since you have changed material properties, not geometry. This would not be dependent on if you have a correct length pole or spacers.

Without seeing pictures, my best guess at what you saw happen was that the two pieces of poles wearing against each other caused a failure where the shaft material started to fail at that interface which translated down to where the shaft enters the grip. Once that failure made it out of the support of the grip the shaft completely failed. Either that or the shaft was damaged before hand such as it was scratched at the location it entered the grip. Out of curiosity, I would love to see pictures.

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Re: Adding length to a pole - 1 to 2 cm

Postby nxski » Sun Mar 01, 2015 5:52 pm

Chris wrote:
nxski wrote:It will do both, I have tried lengthening shafts and once you add more than 1-2cm (depending on the depth of the handle) you start putting torsional stress on the top of the shaft and can cause the carbon to compress and it will usually fail where the shaft meets the bottom of the grip. A similar situation can also occur when you overheat the carbon fiber.


Torsional stress would come from twisting along the axis of the pole. In order to make this stress you are essentially grabbing both ends of the pole and twisting it like you are wringing out a towel. I would think this stress is relatively low in a ski pole under normal use. The glue holding things together would likely fail long before the shaft fails due to torsional stress. Maybe you are thinking of bending stress (Mc/I)

The stress where the shaft enters the grip does not change depending on if you have a correctly cut pole, or one with a 1 or 2 cm spacer stuck in the handle. Research shear moment diagrams and keep in mind the point the load is applied does not change. Compressive stress doesn't change either.

Overheating the carbon fiber would be a different failure mode since you have changed material properties, not geometry. This would not be dependent on if you have a correct length pole or spacers.

Without seeing pictures, my best guess at what you saw happen was that the two pieces of poles wearing against each other caused a failure where the shaft material started to fail at that interface which translated down to where the shaft enters the grip. Once that failure made it out of the support of the grip the shaft completely failed. Either that or the shaft was damaged before hand such as it was scratched at the location it entered the grip. Out of curiosity, I would love to see pictures.


My apologies, I am thinking bending stress. I would call it momentum when referring to the design of a beam. It would appear to be a shear break when it fails, but due to bending forces. The stresses do change since you are creating a longer lever in essence and the bottom of the grip will be applying more pressure on the shaft since there is always a little play within the handle itself.

Overheating is definitely a different failure mode, but the way in which it breaks appears to be the same until you remove the handle and pull out slivers of carbon fibre rather than a chunk.

I wouldn't be concerned about adding 1cm to a Swix pole since their handles have very little play in them and 1cm isn't a large amount. The only downside is that your spacer will likely never come out of your handle if you were to want to re-use them for another purpose.
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Re: Adding length to a pole - 1 to 2 cm

Postby DMK » Mon Mar 02, 2015 11:25 am

I have a pair of Exel Avanti Formulas from probably 15 years ago, they have an oval shaft. About 6 years ago I decided to add some length to them, about 1.25". After trying very unsuccessfully to make this work with the ovalized Exel grips I used some Swix grips. The grips were old and have a plastic frame with thin cork pieces (1/8" inch?) wrapped around in two pieces. Inside the extra pole spacer is from a round swix pole (ovalized shaft wouldn't fit well). There was not much of a way to make pole glue hold this together all that well so I have three stips of electrical tape on the cork. The straps are One Way.

The above combination looks really weird and weirder if you look closely (Exel pole, Swix grip, One Way strap) but it has worked for 6 winters of use. You can feel some 'flex' in one of the grips but if you try to flex the grip but honestly I have had only one real issue with it. Because there is very little plastic surface area on the grip itself, if I am not proactive and adding more glue once a year or so, the grip pops off at some point. I have started using a forth strip of tape at the base of the grip.

They are not pretty but the pole shafts are great and I really like the extra length. Every year (now about every other time I use them) I think they will finally just fully break but they keep working so I keep using them.

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Re: Adding length to a pole - 1 to 2 cm

Postby TooHeavy » Thu Mar 05, 2015 6:18 pm

I broke a Exel Avanti about three feet off the ground clean. I took about six inches of another broken pole (dowl). Split the difference at the break. Fiberglass resin jammed it together and wraped the joint with a little fiberglass resin and cloth . You would not know they were repaired when skiing, they just look a little funky. I use them for bushwacking.


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