Tuesday, 2 July 2019

Triplet hubs from BORG

Triplet lacing is kind of specific. It requires carefully selected components in order to deliver what it supposed to deliver - equal spoke tension between NDR and DR side, higher radial, torsional and lateral stiffness comparing to traditional lacing. 
Today, triplet is used by Campagnolo, Fulcrum and Mavic but not so much in custom building as there are no good hubs available on the market designed for such lacing.... until now... Ladies & Gentlemen, let me introduce to you the BORG 16:8 hubs!


Malcolm from The Cycle Clinic is the man behind BORG brand. If you spend a little bit of time reading his articles you'll quickly realise how much knowledge and experience he has in regards of wheel building. 


When I saw his initial designs of triplet hub I knew this will be done properly and when I got the prototype, built the wheels and made the first ride... I only smiled and thought - this is it!

But first things first, let's go back and talk about triplet lacing itself.

What is really the triplet? Well, in the simplest words it's less spokes on NDR side and more on DR. At first, it doesn't sound logical but the key here is the geometry and physics. 

Source here

Explaining all that in simple words:
  1. They key to make a stiff wheel are the wide bracing angles, especially B as C is limited by the freehub.
  2. In the traditional lacing 1:1 you can push flange B to the left, only to some extend. If you go too far the NDR spoke tension will be very low, resulting in a short lifespan of the wheel (spokes will break quickly as with every rotation of the wheel they will have very low to zero tension). The widest hub in traditional lacing I know is Miche primato (38mm). I think you can't go further then that.
  3. The trick to increase the NDR spoke tension and at the same time to keep wide bracing angle is to use less spokes on NDR side. If you do that, less spokes on the left side will have to use greater force=tension to dish the wheel as on DR there will be more spokes holding the wheel to the right pretty strongly. This is exactly the triplet concept.
Wheel laced by me in 8:16 setup

If all above is so great, why triplet is not that popular today, you might ask? Well, I can only say from my experience - the mass production.

In order to have a proper triplet setup you need three things:
  1. Specific rim drilling. It's about nipple holes angles 
  2. Specific geometry of the hub. Left flange pushed to the left as much as possible, flanges drilled in 8:16 or 4:17.
  3. A bit of more knowledge and experience in wheel building. Spoke length calculation is not that easy and the build is a bit more specific. Not every person in Asia (with all the respect) can do that well I'd say.
As you can imagine from the above, such setup can be used only for triplet and nothing else. That doesn't help in mass production and manufactures simply don't do that as they don't make great money with it. There are few exceptions as I mentioned before but that's it.

Worth to mention, that there are universal hubs on the market which offer the same geometry with 1:1 or triplet drilling, however if such hub has left flange closer to the centre (and it will have due to 1:1 lacing possibilities) it might result in softer wheel in triplet than with 1:1 lacing... so not a good idea at all.


So let's go back to Malcolm and see what did he do with the hub.

First, the hub was designed from the scratch and then manufactured by one of the biggest brands in the industry with large experience in hubs, wheels and other cycling components.

Geometry was done very well, as at the end this hub will be only used for triplet lacing.
  • DS PCD = 54mm
  • NDS PCD = 44.3mm
  • DS centre flange to centre hub = 17.4mm
  • NDS centre flange to centre hub = 49mm
Yes, left flange is pushed away 49mm from the centre of the hub. The widest hub for 1:1 I know has 38mm so it's over 10mm difference - that's massive for lateral stiffness!

See on the picture how much the left flange is pushed away from the centre

Just to compare that to totally different school - DT Swiss has 33mm in their 240/350 hubs. They opted for high NDR spoke tension in 1:1 lacing by sacrificing lateral stiffness.

Bearings are NTN with LLU contact seals. 2x6902 bearings in the body and 2x6802 in the freehub running on a 15mm axle. The freehub has 4 pawls and a 36T ratchet ring. This means fast engagement but the large  diameter ring means a low rate of wear on the ring and pawls

All that means that this hub is built like a German tank, it will survive everything. In order to carry such hub on the street you will need a permission to carry the weapon!

NDR side was laced radially, elbows in


Drawbacks? Of course there are some:
  1. Weight. The rear hub shows about 260g on the scale. The front has 125g
  2. Shape. While the front has a nice shape, the rear one is thick and simple. Some may like it, some others won't
  3. First miles. Due to class of bearings and contact seals, at the beginning wheels won't spin so freely. You will notice some drag while riding. It will go away after few km. In my case after first 3 rides (about 400km/5000m climbs and fast descents reaching up to 80km/h) they started to spin very well. Currently they are as fast as any other wheels I had.
Taking all the benefits of proper triplet lacing, stiffness of the wheels and durability of the bearings + solid construction I'd say that the only point to consider it the weight.

I built my set using Kinlin XR-22T 20h rim front and Kinlin XR-26T 24h rim rear. Pillar PSR 2016 (1.6mm) spokes on front, PSR 2017 (1.7mm) spokes on NDR and PSR 2016 (1.6mm) spokes on DR side. Alloy nipples. The total weight without rim tape was 1540g. By using aero spokes I think the weight would go down to around 1510 - 1520g. Totally acceptable. With light carbon rims the weight below 1500g will be achievable.


In my case the choice for round spokes was done in purpose. I know my leg and style of riding and I wanted to achieve max stiffness without overweighting the wheels. Mission was accomplished. Already during the build when I was doing the spoke stress relieve I could not bend the wheel. 
I setup my rear brake pads very close to the rim (I think less than 2mm) and no matter how strong I push the bike, the rim won't rub the pads. 
Using ticker spokes on NDR I achieved almost equal tension, plus higher lateral stiffness. 

Overall I'm supper happy with the setup and I can only say - Malcolm, well done! Superior job!

As soon as hubs will be available for mass production they will become part of my offer. I'll be building them with Kinlin and carbon rims and my new, super wide alloy rims:


For triplet they will be drilled 8:16 and will come with offset

More reports to come after solid riding. BORG hubs will soon see some sections of Giro Italia and some cols in France. I will be using them daily till the end of the season to ensure all works well and hopefully still this year you will see the first builds to the end customers.

P.S. For those who will be interested, the spoke lengths for ERD 589mm are: NDR 274mm (radial, elbows in) and 276mm DR

Stay tuned and thanks for reading!

Tomasz
blog-wheelbuilding

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