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HomeCyclingAASQ #152: Why is there no inner Truss System in trendy bike...

AASQ #152: Why is there no inner Truss System in trendy bike frames?


We all know, there’s no such factor as a silly query. However there are some questions you won’t need to ask your native store or driving buddies. AASQ is our weekly sequence the place we unravel your questions – critical or in any other case. Hit the hyperlink on the backside of the publish to submit your individual query.

Welcome again to the Bikerumor Ask A Silly Query sequence. This week, we’re taking a more in-depth have a look at the lesser-spotted utilization of Truss Programs in bicycle body design. Considered one of our readers is to know why the usage of trussing, specifically inner trussing, hasn’t been extra extensively taken up by the trade. To sort out this query, we’ve approached a number of body designers who’ve, in numerous kinds, used a Truss System in manufacturing of their body. Having made use of Truss Programs themselves, they’re maybe greatest positioned to touch upon why this uncommon body design has remained, nicely… uncommon.

Why is there no inner truss system in trendy bike frames? Sure, we have to preserve the floor easy however why isn’t there extra speak about particular person strands of fiber taking a carrying load in a truss system? There could possibly be potential weight financial savings in stiff areas like BBs and head tubes.

IsoTruss: Truss programs do provide benefits in weight and stiffness, however there are some challenges incorporating the truss system with the remainder of the bike body. First, some benefits. On the subject of hole composite tubes/sections, essentially the most environment friendly designs have skinny partitions and a big floor space. This makes the partitions liable to puncture and such buildings may be liable to shell buckling. Consider an empty soda can. You’ll be able to stand on it, however the slightest contact to the wall of the can leads to collapse.

isotruss road bike frame

IsoTruss achieves its excessive strength-to-weight ratio with a particular geometry that makes use of longitudinal and helically wound members.  The “iso” and “truss” in “IsoTruss” come from its  environment friendly geometry; isosceles triangles that kind a truss of pyramids that are what give the IsoTruss its distinctive energy and stiffness. Would you experience one in all these? Tell us within the feedback!

With a truss system, particular person members of the truss are extra sturdy than the skinny partitions of the tube and fewer harm susceptible. The failure modes of a truss are sometimes simpler to foretell, too. Trusses are extra environment friendly, from a strength-to-weight standpoint, than hole tubes leading to stiffer, lighter buildings.

delta7 isotruss carbon road bike frame

We did ask Delta7Bikes to contribute to this week’s characteristic however we’re but to listen to again – these guys use the IsoTruss expertise to provide carbon street bike frames

Now a few of the challenges. Probably the most urgent problem, and the probably motive truss programs haven’t been adopted extra readily, is manufacturing. The truss sections require advanced manufacturing. Every part is made individually after which built-in with different body parts manually. This course of is gradual and costly. For a lot of, the extra value doesn’t justify the increase in efficiency. Funding into higher manufacturing strategies would probably yield extra constant, inexpensive merchandise.

Galaxy Gear Works: At first, any inner trussing/bridging/and many others could also be very troublesome or not possible to perform in a significant or value efficient manner on any manufacturing scale. The present manufacturing strategies that produce thin-walled steel tubing widespread within the bicycle trade (aluminum, metal, titanium, or in any other case) preclude the inclusion of inner options. Whereas we are able to manipulate wall thickness with butting processes and shapes with numerous forming strategies, we are able to solely produce hole tubes i.e. no trussing. Carbon tubing manufacturing as we all know it on this trade would additionally (normally) preclude the creation of inner options whether or not the tubes are shaped on a mandrel or inside a mould.

five-land-bikes-factory-tour-swarf-cotic-steel-handmade-fabrication-reynolds-tube-cutting-ovalised-QC

Checking the metal tube butting profiles at 5 Land Bikes, Edinburgh

Nonetheless… I’ve seen inner bridging within the steerer on a couple of carbon forks in the previous couple of years. I don’t imagine it’s common apply. Why not, you may ask? Firstly, I’m sure that it’s an infinite ache within the ass to mould the steerer with an online dividing the tube. Layup precision and laminate compaction can be sophisticated to say the least. Bladder equalization and post-cure removing is also vital hurdles. Right here’s one other thought that’s maybe the true motive why it isn’t widespread; a fork steerer has to fulfill sure structural standards that maybe outline the wall thickness to a level that an inner internet/bridge is superfluous. Shear and bending forces on the fork crown apart, the highest of the steerer tube has to withstand the clamping forces of the stem and ham-fisted mechanics.

Even if everybody ritually abides by the producer’s torque specs and makes use of a torque wrench to put in the fasteners, it has to resist a good bit of crushing power. Add the real-world stresses with the “fudge issue” that the engineer calculates in there to maintain the attorneys joyful, and the steerer has to have a fairly hefty wall – definitely burly sufficient to deal with regular torsional, shear, and bending masses as nicely.

The steerer additionally has to have that “hefty” wall thickness by way of a lot of its size to accommodate the stem clamp top for an excessive vary of motorcycle sizes, assuming a manufacturing fork. So… does it actually make any sense for inner trussing/webbing/bridging on a manufacturing made fork? For my part, it could require an excessive amount of effort for much too little reward. I don’t imagine it might add measurable efficiency advantages or cut back weight at a significant degree.

pegoretti big leg emma steel bike frame

The Pegoretti Large Leg Emma body with one of the beautiful paint jobs we’ve ever laid eyes on!

I’ve additionally seen a couple of examples of inner options on metal bikes, and I’m presently driving an MTB with inner bridging within the chainstays. The purpose of the aforementioned options is stiffness. Dario Pegoretti created the Large Leg Emma with a sequence of flat sheet bridges within the downtube. They’re inserted into slots reduce into the perimeters of the tube, brazed into place and lined with a tidy, brazed-on gusset. You’ll be able to see these options clearly on the mannequin web page on the Pegoretti web site.

The tubes on this bike are pretty giant in diameter for metal tubing, and I’m positive that the partitions are fairly skinny. For my part, the bridging plates are lengthy sufficient (in reference to the lengthy axis of the tube) to behave as a truss to extend the tube’s resistance to side-to-side bending forces i.e. all-out sprinting for metropolis restrict indicators on Tuesday nights. How a lot stiffer is it as a consequence of these inner options? I do not know. It could possibly be measured in fact.

My present MTB was constructed as a “shreddy hardtail” so it wanted to be considerably burly. Energy and stiffness had been paramount, and people attributes needed to marry with a kinda quick chainstay size and a couple of.8″ tires. With all that in thoughts, the chainstays had been fairly slender the place they had been shaped across the tire. I felt like this slender cross part wasn’t going to provide sufficient lateral stiffness within the stays.

A part of my concern was the true chance of tube deformation and bending beneath pedaling masses. Like the benefits I imagine to be current on the Pegoretti downtube, I feel I added energy and stiffness to the tubes by including horizontally oriented plate bridges throughout the inside of the slender, ahead portion of the stays. I executed these additions by slicing the tubes, inserting the sheet-metal plates (about 4 inches lengthy), and welding the plate’s edge alongside the tube intersection.

galaxy gearowkrs roswell truss swingarm design

How wild-looking is that this construct?! It’s the Galaxy Gear Works Roswell full suspension mountain bike with Belief Efficiency linkage fork.

Now we ask the query, “was it value all the trouble?” I don’t know the reply. I didn’t do any lab kind testing or calculations. I’m no engineer. What I do know is that the bike rides nicely and goes sturdy after greater than two years of onerous driving. I additionally know that I rattling positive didn’t save any weight by including these bridges.

Is it attainable that inner bridging/trussing might permit thinner partitions on the tubes? I’d say heck yeah! How would we do it? Maybe 3D printing one way or the other reasonably than laborious hand work or a mixture of each? And wouldn’t it come at a value to sturdiness and due to this fact practicality? The reply could be sure. Use the huge, however not stunning proliferation of carbon restore companies arising all around the nation now that the quantity of out-of-warranty carbon bikes has reached important mass as proof. The tubes on ultralight carbon street bikes don’t have to get a lot thinner except we see extra quantity of more durable supplies like Dyneema included into the laminates. That stuff is dear although!

galaxy gearworks cosmo emtb

The Galaxy Gear Works Cosmo eMTB with built-in rear rack

In the true sense, inner trussing doesn’t generally exist on this trade. With carbon manufacturing frames routinely coming to market beneath 900g, is there actually a have to attempt to make them lighter? I’m unsure. And most of the time, these ultralight bikes are a lot stiff due to excessive modulus carbon and sensible laminate engineering.

Frace Bike: A tube in comparison with the truss system is having at all times much less weight for having the identical stiff attribute. So it’s for positive extra weight saving to have a tube – however it is usually much more boring. Everyone is doing tubes – however we need to have one thing completely different from all of the others. And, for having a completely milled body out of aluminum there isn’t any different alternative than selecting such a method because the truss system. However this truss system is dearer – however it’s trying nice. Positive you must pay extra however then you might be getting a singular model.

frace f160

The Frace F160 is machined from a 70 kg slab of aluminum

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