A Much improved ebike spoke calculator,

[justin_le]

We're in the midst of making a better online spoke length calculator tool to address the needs of people lacing up hub motors in to rims, and before going live would like to get a bit of feedback.
The test URL is here:
http://www.ebikes.ca/spokecalculator/index.html

There are a few things missing from most existing tools that I wanted to include

#1) Representative Wheel Drawing This is somewhat self explanatory, but I thought it would be great to have an online app that actually draws the motor, rim, and lacing pattern all dimensionally correct so that you get a visual cue that the numbers and selection are what you want. This also helps you see whether it's feasible to say lace a large diameter hub motor into a 16" rim, or whether double cross pattern really makes sense, or even to idiot check that the ERD number you found for a rim is in the right ballpark.

Wheel Renderings.jpg (63.37 KiB) Viewed 5836 times

#2) Paired Spoke Holes An increasing number of hub motors don't have uniform spoke holes around the perimeter but instead group them into pairs. This has a few advantages, it means that straight lacing pattern still has a tangental element to the spokes tension so that you get the torque tranmision benefits of a cross pattern with the lacing simplicity of a radial build. It also allows for a lighter overall motor since large sections of the spoke flange can be cut away. An example is the new Crysatlyte Crown motors for normal spokes:

Crown Flange Holes.jpg (29.42 KiB) Viewed 5836 times

With the new calculator, if you check the box "paired hole spacing", then you can set a custom spacing between adjacent sets of grouped holes rather than have it assume a uniform distribution.

Paired Hole Spacings.jpg (46.8 KiB) Viewed 5836 times

You can also choose with each lacing whether to have initial cross over the adjacent spokes in the pair, or have them initially cross the spoke from the alternate pair:

Alternate Crossings.jpg (51.4 KiB) Viewed 5836 times

#3) Spoke Angle Measurement Finally, for any of these arrangements it shows the actual angle between the spoke nipple and the tangent where it enters the rim, so that you can quantify the feasibility of a build. I'm not sure what rules of thumb there are for acceptable angles, but my experience is that with eyeletted rims and tight nipples it can often be tricky when this angle is less than about 75-77 degrees, while with rims that don't have eyelets you can usually get away going down to 70, though it's not always pretty.

Spoke Angle.jpg (8.77 KiB) Viewed 5836 times

Anyways, for now I went ahead and measured all of the different hub motors I have kicking around in our lab and filled up the motor drop-down list with that, and similarly with the rims that a lot of our stock wheel builds come in. But I'd be happy to add other specific motor models and rim types which are in common use by ES members here. So if you have a suggestion, AND you have independent measurements of the relative parameters (ERD for the rims, spoke flange diameter and flange spacing for the hubs), then let me know with some justification and we can add it.

[Tench]

Justin your graphic representation of the pattern is an awesome addition to this tool!
Machining around the holes to flower petal the steel flanges on my H series and save weight is something I have just done, this tool would allow even more weight saving by pairing the holes and provides an easy way to calculate the spoke lengths and also visualise the outcome, Brilliant!!
I had not considered the benefit of paired holes over radial spokes on small dia rims before, this has to result in a stronger wheel.

[miuan]

Brilliant Justin, keep it coming!

[cwah]

thanks

[voicecoils]

Brilliant! I'll start putting this into use straight away

It also gives me another nudge towards experimenting with drilling hubs for spoke pairing

[rborger73]

Any chance of adding a Magic pie 3 on there?

[Ypedal]

Very nice !...

i have a small request,for the ' idiot factor ' i frequently suffer from, for Hub Flange Diameter and Flange Spacing, a small diagram or illustration to show what they represent... saves a trip to google

[justin_le]

Any chance of adding a Magic pie 3 on there?

There is for sure, but I can't just type in "Magic Pie 3" and suddenly have a verified value for the flange spacing and spoke hole diameter show up in the database. So to contribute to getting it on the list, then we'll need someone who has one to break out their calipers and measure the relevant spoke hole dimensions.

Hence the AND part:

So if you have a suggestion, AND you have independent measurements of the relative parameters (ERD for the rims, spoke flange diameter and flange spacing for the hubs), then let me know with some justification and we can add it.

[justin_le]

I had not considered the benefit of paired holes over radial spokes on small dia rims before, this has to result in a stronger wheel.

Yes for sure, I'm really surprised too that this isn't a lot more common. Pure radial lacing is a foolish concept for a wheel that needs to transmit torque, while actually crossing the spokes with large diameter hubs in small rims leads to pretty extreme spoke angles at the rim which can cause its own problems. This avoids both those problems:

Zero Cross, Some Angle.jpg (28.08 KiB) Viewed 5626 times

And the actual tangential spoke angle is almost exactly the same as a regular diameter bike hub with a standard triple cross:

Small Hub 3 Cross.jpg (32.73 KiB) Viewed 5626 times

[zener]

That is realy a very usefull tool for every ebike builder.
As a thank you i post here the magic pie 3 calculation.

mapi3.png (83.39 KiB) Viewed 829 times

[justin_le]

That is realy a very usefull tool for every ebike builder.
As a thank you i post here the magic pie 3 calculation.

Awesome, thanks Zener. So you have verified that the rim hole spacing is 299mm center to center. For the flange width of 22mm, is that the inside, outside, or mid-point measurement? In all the hubs I've added so far I used the mid-point flange spacing for consistency. So the calculation is a tiny bit too short for spokes that are laced outside the flange, and a bit too long for spokes that come out inside the flange. We might do a later upgrade where you can select to have the spoke head inside or outside the flange and then it would calculate accordingly. Anyways I've added it to the database list.

Also, earlier today we rolled out some more upgrades and bug fixes. We allowed it so that you can do some generally nonsensical stuff, like have an odd number of spoke holes, or a rim ERD that is larger than the nominal wheel size, or a negative flange diameter etc., and it will still do it's best at making a drawing but will show a warning note at the bottom. As well, when you select a hub or rim from the drop-down, the associated fields become greyed out so that you can't accidentally change a value and not realize it. If you then want to deliberately change a parameter from one of the standard hubs, just select "custom hub" from the drop-down list and then the fields will be editable again.

-Justin

[Obiwan007]

This is simply fantastic! I will use it quite soon on my 4060 resurrection project. One thing I have found useful in other calculators is the ability to set spoke bed off set (especially when considering wider rim projects) also the ability to build in some or a lot of dish. Those calculators however often lack the ability to handle large hubs and several of your other cool improvements. Combining these features in one calculator would be a dream. Here is an example of one that does dish and also has a graphic representation of the final shape from an end-on view:

http://kstoerz.com/freespoke/fullcalc

Once again Justin, thanks from a grateful community. Obiwan

[voicecoils]

I had not considered the benefit of paired holes over radial spokes on small dia rims before, this has to result in a stronger wheel.

Yes for sure, I'm really surprised too that this isn't a lot more common.

Wavecrest did paired radial for both wheels starting in 2003 but perhaps no one paid it much attention!

wavecrest-wheel.jpg (223.49 KiB) Viewed 5568 times

http://www.cpsc.gov/PageFiles/75310/05593.jpg
Nice to see good ideas of the past being rediscovered even if we're not reinventing the wheel

Kinda like all the moped rim wheelbuilds happening now resemble what was done on a certain electric moped from 2002...

[zener]

That is realy a very usefull tool for every ebike builder.
As a thank you i post here the magic pie 3 calculation.

Awesome, thanks Zener. So you have verified that the rim hole spacing is 299mm center to center. For the flange width of 22mm, is that the inside, outside, or mid-point measurement? In all the hubs I've added so far I used the mid-point flange spacing for consistency. So the calculation is a tiny bit too short for spokes that are laced outside the flange, and a bit too long for spokes that come out inside the flange. We might do a later upgrade where you can select to have the spoke head inside or outside the flange and then it would calculate accordingly. Anyways I've added it to the database list.

Also, earlier today we rolled out some more upgrades and bug fixes. We allowed it so that you can do some generally nonsensical stuff, like have an odd number of spoke holes, or a rim ERD that is larger than the nominal wheel size, or a negative flange diameter etc., and it will still do it's best at making a drawing but will show a warning note at the bottom. As well, when you select a hub or rim from the drop-down, the associated fields become greyed out so that you can't accidentally change a value and not realize it. If you then want to deliberately change a parameter from one of the standard hubs, just select "custom hub" from the drop-down list and then the fields will be editable again.

-Justin

Yes the flange width is mid-point too.
I have bought 120mm spokes and they are not too long and its laced that they are all inside. Not optimal for laterally stiffness but not other possible.

[pendragon8000]

This is great.
I'm looking at doing a bmx, h3540 in 20bmx rim.
Radial won't do.
And the angle of single cross is on the limit of possible and definitely not easy to build.

Thanks Justin

So any suggestions on drilling the hub flange?
And is the spacing measured as a segment of circumference or a direct line, (like a cord ?) At 10mm it would be similar.

[justin_le]

This is great.
So any suggestions on drilling the hub flange?

If you have a hand drill and an center punch to properly mark the hole location first, then there isn't much to it. But, you'll need to think a little bit about the right vs. left flange hole alignments. You want the 'extra' hole drilled on the same side of the existing hole on both the left and the right flanges, so that the pairs of holes on the left side continues to be 10 degrees offset from the pair of holes on the right side.

And is the spacing measured as a segment of circumference or a direct line, (like a cord ?) At 10mm it would be similar.

It is a circumferential measurement for calculation expediency, but just measure the cord because the difference is completely negligible unless you only have a very small number of spokes (like 8 or something).

-Justin

[pendragon8000]

Great thanks for clarifying that Justin,

just one other thing so i can decide what arangment of spoke pattern i will use...
I'm thinking about the angle at the hub and how its vertually a tangent on a normal hub, and how this affects things?

I should have done some reasearch before i asked this now i that im asking i realise i could have come to a conclusion on my own. but it would be nice to see what you and others think.

anyway, radial is perpandicular at rim and hub, then normal single cross in a small rim - big hub as tangental at hub and way off perpendicular at rim, so i guess a compromise is best and as you origionaly sugested , 75º spoke on rim sounds about right. so for my examle of h35xx in 20"bmx rim a closely pared no cross pattern would be best theoretically? i might go closely paired single cross just because it seems right to me.

thanks again
Ken

edit:
sory for ambiguity, im really trying to ask about the importance of the spoke angle from the hub flange.
edit:
so this is the rim angle I'll go for and its about on the limit( after eyelets removed)

spokes.JPG (34.92 KiB) Viewed 5496 times

[John Bozi]

Thanks Justin.

Pendragon, that diagram looks like they are too close together. I'd bet having that much stress with so little metal between the two spokes the flange will eventually crack or even break off between the spokes.

No engineer though

[amberwolf]

If the flange is made properly, it's a non-issue, as there is even less material in many normal bicycle hubs.

the catch is whether they made the flange normlaly, or if they cast it with bubles or cracks in it, etc. :/

[justin_le]

This is simply fantastic! I will use it quite soon on my 4060 resurrection project. One thing I have found useful in other calculators is the ability to set spoke bed off set (especially when considering wider rim projects) also the ability to build in some or a lot of dish.

I hear. I'd be worried about adding a number of extra fields in the default view because that just complicates things for most people who don't need it, but we could have an "advanced" tab that opens up for those wanting dish control. For now though, you can very easily get the same results by simply changing the the flange width. So if you have motor that has say a 40mm flange spacing, but it is offset 10mm to one side, then just calculate the spoke length in one case with the spacing set to 20mm (for the 10mm side), and for the long side spokes that are 30mm from center, use a flange spacing of 60mm. Similarly, if the rim itself has an offset between the left and right spoke holes, then you'd just subtract this offset from the flange spacing

But if we do a 2.0 version enhancement, this would be on the list.

Here is an example of one that does dish and also has a graphic representation of the final shape from an end-on view:
http://kstoerz.com/freespoke/fullcalc

Hey cool, don't know how I didn't come across this one before, that's pretty comprehensive. A drawing view of the edge like this when doing dishing is especially useful too.

[justin_le]

Yes for sure, I'm really surprised too that this isn't a lot more common.

Wavecrest did paired radial for both wheels starting in 2003 but perhaps no one paid it much attention!

At the time I sure did! Wavecrest also had a quick release axle, an integrated torque arm, large diameter ball bearings, cassette freehub system rather than freewheel etc. Clearly when it comes to ebike motor development, the chinese had been doing their own thing rather than copying early western efforts.

-Justin

[justin_le]

Great thanks for clarifying that Justin,

just one other thing so i can decide what arangment of spoke pattern i will use...
I'm thinking about the angle at the hub and how its vertually a tangent on a normal hub, and how this affects things?

The only advantage of a spoke that exits "tangent" to the hub flange is that there is then very little outwards radial force on the hub flange holes. The spokes are effectively pulling against one another, and so you don't have a risk of the spoke tension ripping right through the flange. In practice, any hub flange should be able to handle fully radial spoke tension just fine, but some cheaper cast aluminum motors have been known to fail this way.

As far as transmitting motor or braking torque goes, it makes NO difference if you have spokes exiting tangent from a normal size hub or just at a slight angle from a much larger diameter hub. All that matters in this case is the angle where the spoke meets the rim. If this angle is the same, then the same torque will produce the same increase/decrease in tension on the leading and trailing spokes, regardless of whether it is 0 cross with paired spoke holes or triple cross coming out tangent from a small hub.

anyway, radial is perpandicular at rim and hub, then normal single cross in a small rim - big hub as tangental at hub and way off perpendicular at rim, so i guess a compromise is best and as you origionaly sugested , 75º spoke on rim sounds about right.

I'd aim for more like 80 degrees, especially if the spokes are short. Typical bike wheels are like 82-83.

so for my examle of h35xx in 20"bmx rim a closely pared no cross pattern would be best theoretically? i might go closely paired single cross just because it seems right to me.

You shouldn't let "seems right" get in the way of rational thought. Go 0 cross!

-Justin

[pendragon8000]

You shouldn't let "seems right" get in the way of rational thought. Go 0 cross!

-Justin

Haha yeah your sure are right. Thanks for all that valuable info. I'll take it into consideration and do another calculation plan.
Ken

[John Bozi]

You shouldn't let "seems right" get in the way of rational thought. Go 0 cross!

-Justin

Haha yeah your sure are right. Thanks for all that valuable info. I'll take it into consideration and do another calculation plan.
Ken

zero

[justin_le]

Well, just some minor cosmetic updates but we've now got it showing the spoke nipples and motor axle and side cover diameter so that it looks a little more photo realistic:

Nipples and Axles.jpg (23.09 KiB) Viewed 5238 times

And also added the Heinzmann PRA-180 motor which is another example of a hub that uses paired spoke holes in the flange, in this case quite close together at 9mm apart.

I'm going to fill out the support documents and take this to main spoke calculator site soon, but one last call if anyone has specific rims that they feel are used often enough to include in our dropdown rim selection list? I know that the Alex DM24's come up a bit in custom builds, are there others you would want to see?

-Justin