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Old 08-24-19, 06:23 AM
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strumbuddy321
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Help spokes

whats best way to true a wheel after new spokes fitted
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Old 08-24-19, 12:00 PM
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adipe
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Originally Posted by strumbuddy321 View Post
whats best way to true a wheel after new spokes fitted
radial true should be sought before axial(lateral) true but you need to have the tension variance as to agree to the radial untrueness so to speak.
for example:
1.8mm spoke diameter;
290mm length;
179GPa modulus of elasticity in tension at about 70kgf average tension - when you should ensure radial true for a rear wheel or a disc front with the NDS spokes rather slack on the rear or non disc side for the front.
lets say one particular spoke is at 80kgf, therefore 10kgf (98N) higher than the average;

98N/2.544sqmm=38.5MPa higher stress than average
38.5MPa/179GPa*290mm=0.062mm

the rim would be ok to be further out from the hub with respect to the average distance.
you should tolerate this runout for that portion of the rim with all these above parameters.

after you fix radial true at this lower tension (supposing you have a rather lateral true wheel) you raise the other spokes tension exclusively to a high level being careful to keep the lateral true. don't touch the DS nipples (for a rear wheel) after you went beyond fixing the radial true.

you might need to go back to fix radial true after the nipples have bedded in the eyelets and the spokes in the hub flanges in an other than uniform way.

you either fix the dish before the last stages of seeking a high tension (in order to be able to straighten the rim) and then backing to a lower level after all goes well or you fix the dish after all this.

it's useful to stress relieve at each stage of raising the tension - remember to don't touch the nipples of the spokes that are in high tension - DS rear, disc side front.

and the most important thing: don't use nipples other than brass and wax them. linseed oil would work but you would have a hard time later if you need to retrue. wax lubricants are best and its best to leave the wax solution be able to dry on the spokes thread and the nipples before assembly.

it's not very hard to achieve +/-0.05mm lateral and radial true with +/-5% spoke tension variance but you need to be careful to balance out the DS tension variance with the radial true from the get go.
find (google) a tone generator - i'm not allowed to insert links as i don't yet have 10 posts.

spokes vibrate together, when plucking one keep the other quiet to be able to discern which is higher and which is lower you sometimes need to pluch each one several times to discern between them.

find this equation:
T = 4μL≤f≤

tension as a function of linear density, length of vibrating wire, frequency.
google to check it out.

example:
T=4*600*600*0.15*0.15*0.9*0.9*0.008*3.14159...
where
600 = frequency, Hz
0.15 = length between nipple and cross, m
0.9 = spoke radius (1.8mm/2), mm
0.008 = density for the stainless steels in respect to sqcm being 1000*sqmm
---
result: ~659.58 Newtons = ~67.3Kgf
for 603 Hz the tension (all these parameters above being kept) would be 67.6kgf

thats a very small difference (error) supposing you are careful and there aren't other noises/distractions and therefore are able to discern 603 vs 600 Hz.

radial trueness is fixed at a medium spoke tension for other reasons as well.

you don't need to worry about accuracy at the end tension values for spoke tension variance in regards to adjusting radial true considering spoke tension. radial true should not be normally be fixed at high tension for different reasons. if you need to go back to fix radial true you should lower the NDS tension first.

make sure you don't have a lateral untrue wheel when fixing the final radial true - with spoke tension variance being taken into account.

a new wheel could need two stages in fixing radial true because of bedding in - nipples/eyelets and flanges/spokes.

don't forget to stress relieve at every stage of raising tension NDS wise: raise tension, fix lateral, stress relieve.

put labels on DS spokes as to make sure they don't remain twisted. you might as well put numbers on them to keep track.

put labels on rim to be able to adjust dish in exactly n*90 degrees of spoke key turn. mark lines on the labeled rim as to be parallel with the spoke key and therefore end with exactly n*90 degrees for all nipples on the flange for this matter. you could use this trick for balancing radial true with spoke tension variance and therefore need to apply either another label on the rim or a different colour marked line.

you can neglect error due to spokes being thicker at the nipples; the error spread around all the spokes;
be careful not to mix different spokes as to be sure to have them at the same exact diameter;
you can neglect the very very very small variance of the spokes diameter at different tensions. if you doubt this you can research and even use online calculators. you only need to google "poisson's ratio" to find out the matter;

the only way you can be in considerable error is in regard to the estimated average tension because you won't be very accurately measure the distance (0.15m) for the vibrating chord etc. but for relative tension all this works very well.

you need not worry that you don't have an exact 140kgf average DS tension and it could be 136kgf etc.
you need to worry about uniformity in tension.
and you need to make sure stress corrossion does not happen. treat the surface on the inner rim around the eyelets with something to prevent corrosion.

i might have been slightly offtopic but all this for the sake of ensuring a long lasting wheel.
stress corrosion and fatigue being affected by the chemicals that need to be kept away from the vulnerable surface are not to be neglected things.

don't ask me exact figures for the fatigue being affected by corrosion, just make sure you deal with it. treat the surface ot the rims with something no matter the spoke tension you choose to have as a target, 120kgf as written in the books or 150+ as what professionals use as a target BUT with a very small tension variance and the stress relieving and the lowering the tension after seeking a high tension and therefore cold working (strain hardening) the rim when straigtening small imperfections.

150kgf is need to ensure the wheel is long lasting with a heavy load.

don't ask me exact figures for aluminum vs brass nipples. avoid aluminum nipples like plague for wheels that you build expecting them to last for decades. aluminum nipples are ok for competition, just to shed some grams.

if you don't believe me you can do your own research.

Last Edit: i've cut the erroneous second muliplying by the pi() number in the example that at first added twice (forgot that i already put once) and observed now.
tone generator for assessing frequency: https://www.szynalski.com/tone-generator/
i can discern between 600 and 603 Hz clearly, other people could have different outcomes.
at least it's better than using just your fingers or just listening without something to compare to and therefore being able to compute.

Last edited by adipe; 08-29-19 at 08:46 AM. Reason: NDS tension should be lowered before readjusting DS if needed
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Old 08-26-19, 02:49 AM
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strumbuddy321
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wow you certainly know your stuff, very informative many thanks to you for that
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