determine the correct spoke tension

I dont have an answer for you, but can share this. I bought a 1000W motor laced to a 26" rim from china with very thick, rugged spokes. Every 6 months or so, the spokes become so loose that they snap and crackle as I ride, so i have to tighten a bit. With only a simple spoke wrench like this (without tensioner measurement) I adjust each spoke to the same pitch to get the spoke to roughly the same tension.

Some folks in the bike world have done the same: http://www.bikeforums.net/archive/index.php/t-207084.html

Mark.
 
Radial lacing is not a good choice for torque transfer. I would stay away from it on drive wheels or on front wheels if you are using disk brakes. You will need spokes and rims that are much stronger than required just to survive light duty. If you plan on putting much power in it, the forces quickly exceed the strength of materials or at least their elastic limits, which will cause them to loosen up and lunch them selves. Never used a spoke tension gauge on anything as short as you are describing but interested on how long your wheel lasts.
 
speedmd said:
Radial lacing is not a good choice for torque transfer. I would stay away from it on drive wheels or on front wheels if you are using disk brakes. You will need spokes and rims that are much stronger than required just to survive light duty. If you plan on putting much power in it, the forces quickly exceed the strength of materials or at least their elastic limits, which will cause them to loosen up and lunch them selves. Never used a spoke tension gauge on anything as short as you are describing but interested on how long your wheel lasts.
Click to expand...
i don't know how much you know about lacing a big hub motor into a 20" rim. but everyone suggests doing it radially. torque transfer surely is a big issue, but spoke bending of 10cm/4in spokes is even worse if not even not possible.
so the questions remains: how much is enough/too much. i don't want to overtighten the spokes and make the wheel collapse. also overtightened spokes tend to brake easier.
 
izeman said:
I radially laced my crystalyte in a 20" rim.
Especially with radial lacing spoke tension is essential. But o can nowhere find information on how much is enough, and how much is to much.
Anyone can help on that?
Click to expand...
I don't have an answer for you. Just a thought: Let's say someone can provide you with an actual number for the proper tension, do you have the proper equipment to measure it? If it were me I would make them as tight as possible without damaging the thread.
 
your argument is feasable. i have an iphone app which can show spoke tension im kgf. right know i can only use it to compare one spoke's tension with the other. and it gives me a value. which is of no use to me. i also think that spoke tension should be the same no matter of spoke's diameter. afaik it's the rim that will start to fail.

btw: shown value is not real. i have values of 60-65 kgf - but it's hard to make a screenshot of the actual values.
 

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If I understand you correctly your equiqment can only show the difference in tension between two adjacent spokes. In other words, you cannot measure the tension of one single spoke, correct?

I am an amateur wheel builder but I have done quite a few and I always damaged the spoke or nipple thread when I over tightened. The rim was never damaged. But I was using regular spokes, not the fat ones.
 
now i'm not sure that i understand your question correctly ;)
i CAN see the value of a single spoke. you ping a spoke, it make a sound which is put in relation to the diameter of the spoke and it's tension. and the app calculates the tension. from the appstore comments it seems to be quite accurate.
i bought quite high quality spokes and nipples as well as a rigid rim.
so i may just check tendion regularly and hope for the best ;)
 
I see the problems you would have if you were to go with a cross pattern, butt still would classify this as a somewhat less than bullet proof setup laced this way. Will work for certain if the rim and spokes keep their dimensions. Problems I have had with loosening spokes were minimized greatly by adding just a touch of green loctite to the spoke/nipple joint after tensioning. It seeps in a bit and keeps the nipples from spinning completely out miles from home. Can still be trued easily. Best wishes.
 
((I attempted to insert a picture) http://www.classicsportscars.eu/spitfire/PICTURES/bolt_on_wire_wire_wheel.JPG classic car wire wheel

Radial is easiest in the situation. For cross spoke pattern on your set up, you would bend (soft faced pliers) the spokes at the nipple end away from the threads so it would go into the rim in a more perpendicular path. You would also need to alternate the side of the motor flange you stick them through so they would pass each other without too much bend.

I copied a section from sheldon brown below ( http://sheldonbrown.com/wheelbuild.html )

(Radial Spoking
Radial spoked (cross 0) wheels have the spokes going straight out from the hub. This pattern is only suitable for front wheels that don't use hub brakes. They are very cool-looking, and are often a good choice for the ultimate in performance, because they are slightly lighter and, in theory, may have a very slight ærodynamic edge.

There are two things to watch out for with radial wheels. Because the nipples point straight inward from the rim, they can turn more easily in most rims than when they are bent to a slight angle by a semi-tangent spoke pattern. This ease of turning increases the risk of their unscrewing themselves on the road. To prevent this, nipples on radial wheels should not be lubricated, and it is a good idea to use a spoke adhesive such as Wheelsmith Spoke Prep or one of the milder flavors of Loctite ® on them. (Or, if a rim does not have recessed spoke holes, the rim tape and air pressure in the inner tube will keep the spokes from turning -- at least with a high-pressure tire).

The other potential problem with radial wheels is that the spokes, trailing straight outward on the hub flange, can possibly rip the outer edge of the flange right off along the line of the spoke holes. This is most likely to happen with small-flange, 36 hole hubs, because there is less metal between the spoke holes. If a used hub is re-laced radially, the notches left by the old spokes can act as stress risers, further weakening the flange.

Many hub manufacturers specifically recommend against radial spoking for this reason, and will not honor warranties on hubs that have been spoked radially. :cry:


Not trying to spook you out, I just see trouble coming for you on the radial drive wheel concept. Back to your question of proper tension, well, it gets a bit more complicated. First, lets assume the wheel is strong enough to hold the spoke tensions. You would want to set the tension in the spoke high enough so that is would still be snug when it was at bottom dead center with a normal (high) load on the wheel. This assures the rim will stay round. This would be the minimum tension. For maximum, you will want to stay well below (lets say 50% )of the elastic limit of the spokes. This allows for 50% more stretch before you permanently deform them and thus loosen the wheel.
 
on two of my hub ebikes I did't have to even touch spokes, one for 23,000km , other for 8,000km.
Both use Alexrims and DT Swiss spokes.
Are you sure the thing is not about quality of spokes and/or rim?
 
On the ebikes.ca spoke calculator page re: radial lacing " In spite of popular wisdom not to use radial lacing on drive wheels,empirical experience has been that this isn't really an issue with the large hubs in small rims." Sheldon Browns reasoning in favor of using Loctite on the spoke threads when radial lacing makes sense to me.
 
I use a Park TM-1 Tension Meter on my wheel builds. An old CSM wheel builder once told me that if I had nothing else, to go by the pitch of the spoke, which should be F Sharp (F#) on nearly any build. A guitar tuner from your local music store could be in your future. As always YMMV.
 
miro13car said:
on two of my hub ebikes I did't have to even touch spokes, one for 23,000km , other for 8,000km.
Both use Alexrims and DT Swiss spokes.
Are you sure the thing is not about quality of spokes and/or rim?
Click to expand...

I agree, use the good stuff. Some folks will break anything. Some nothing.

aroundqube said:
On the ebikes.ca spoke calculator page re: radial lacing " In spite of popular wisdom not to use radial lacing on drive wheels,empirical experience has been that this isn't really an issue with the large hubs in small rims.
:) Building a wheel that is five - ten times stronger and much heavier than is required just to over compensate for poor / no engineering is considered acceptable, just to make it easier to build. :p The saying "Overbuild it! Use a thick pencil", the old timers would say." Great for bridges, buildings and tractors, but not flight hardware. Curious if any of the high powered builds out there have had long term luck. I have never seen a motorcycle with radial drive. Sure that folks have tried it. On the e-bike with a DD motor, you would not have popping clutches, clutch less shifts, and hard down shifts to deal with, but still have to face the daily grind. As long as you stay within the elastic limits of the components, it should hold up.

" Sheldon Browns reasoning in favor of using Loctite on the spoke threads when radial lacing makes sense to me.
Click to expand...
Green number 290, designed to secure assembled fasteners.
 
Kirk said:
I use a Park TM-1 Tension Meter on my wheel builds. An old CSM wheel builder once told me that if I had nothing else, to go by the pitch of the spoke, which should be F Sharp (F#) on nearly any build. A guitar tuner from your local music store could be in your future. As always YMMV.
Click to expand...

Piano tuning stores should be able to supply an F# tuning fork if your so inclined. Wow, that old builder you met is right. A lot of my spokes are F#. On both my 29er and 20er. I have a few that get altered because they are touching stuff (i.e. reflector) 8)
 
melodious said:
Kirk said:
I use a Park TM-1 Tension Meter on my wheel builds. An old CSM wheel builder once told me that if I had nothing else, to go by the pitch of the spoke, which should be F Sharp (F#) on nearly any build. A guitar tuner from your local music store could be in your future. As always YMMV.
Click to expand...

Piano tuning stores should be able to supply an F# tuning fork if your so inclined. Wow, that old builder you met is right. A lot of my spokes are F#. On both my 29er and 20er. I have a few that get altered because they are touching stuff (i.e. reflector) 8)
Click to expand...

how would you use that tuning fork? i know what to do: knock it onto something, it start to vibrate and gives a sound. but my super short 70mm spokes don't seem to vibrate at all :(
 
Hi izeman

You are working with motorcycle sized spokes/ wheels /hubs. What we use on them if you want the best setup, is a torque wrench. You may need to adapt a head to fit your nipples. I would set them to the lowest motorcycle settings (lower if you see rim deforming at the hole), true it, loctite, and ride away. No more guessing.
Cheers.

http://www.fasstco.com/shop/spoke-torque-wrench
http://www.rkexcelamerica.com/mx_excel_spoke_wrench.html
 
speedmd said:
Hi izeman

You are working with motorcycle sized spokes/ wheels /hubs. What we use on them if you want the best setup, is a torque wrench. You may need to adapt a head to fit your nipples. I would set them to the lowest motorcycle settings (lower if you see rim deforming at the hole), true it, loctite, and ride away. No more guessing.
Cheers.

http://www.fasstco.com/shop/spoke-torque-wrench
http://www.rkexcelamerica.com/mx_excel_spoke_wrench.html
Click to expand...
great idea :) i have a torque wrench. i just have to make an adapter for 3.65mm. and second i need to know what's the best torque value to set? i surely depends on the rim.
what i read a spoke tension of 110-120kgf is best for bmx rims. but how to translate that into the torque to screw down the nipple???
 
Hi izeman

Not a straight forward calculation unfortunately. You can get close knowing the thread pitch and diameters, but lots of trouble with noise (thread friction, friction from eyelet, "give" in the rim, etc)on this to get accurate conversions. They will vary as much as 30% or more from calcs. Some good reading so you can better do the math. http://www.hexagon.de/rs/engineering%20fundamentals.pdf

I would start at a few inch pounds, and see how it builds up, looking closely at the eyelet areas and for bulges in the rim near them. I would consider something around 5 inch pounds torque about max when looking at a #2 small screw data and based on the wheels I have built but the rim may not be up for that. Just a guess. http://www.holo-krome.com/pdf/torquedatachart.pdf
http://www.pencomsf.com/screw-torque-reference.aspx

With the Radial pattern, you have the shortest / stiffest spoke setup, so be careful as the hub and rim will both be at risk from the spoke stresses.

Best wishes
 
Torque is a lousy way of setting tension, but if you are going that way, the adapter you want is called a crow's foot wrench, which is actually an adapter from open end to square drive (1/4" in this case, I expect).

The way I would do this if I didn't have a spoke tension meter, is to find a well built wheel with a cross pattern that gives an unsupported span similar to what you have. If you pluck/flex the spoke in the cross plane direction back to back with your wheel, the flexure should be similar. You could event put the wheels adjacent, and react one spoke from your reference wheel against a spoke from this wheel, noting if one deflects more than the other. The thicker spoke only contributes a small amount of bending stiffness over that of the thinner spoke, making this a reasonable approach, given the wheel should be relatively insensitive to tension above some threshold, and below the static failure threshold of the weakest component. From there, tension should be kept as uniform as possible while still truing the wheel. With these parts, that probably isn't going to be all that uniform (certainly not so much so that setting uniform tension with precision produces a true wheel, if that's what you were thinking).
 
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