Avanti and accelerometers: refining ride qualities
At the end of 2010, RIDE teamed up with graduates from Deakin University to devise a testing protocol that measured the differences in movement on various parts of a bike to try and ascertain what benefits (or hindrances) came from different frame designs with the use of accelerometers. We published the data collected from the tests bikes in several issues but ultimately scrapped the protocol as there were too many variables to make it practical to achieve the desired result in the limited time frame that we had the test bikes for. Still, it offered interesting feedback and the use of accelerometers remains an integral part of modern-day bike design.
In late-June, Sheppard Industries – the agents for several bike brands in Australia, including Avanti, Scott, Malvern Star and Haro (amongst many other products) – held a dealer show in Melbourne and the company invited numerous product managers, engineers and sales agents along to discuss the vast range of cycling wares on display. Business was done and the media was welcomed to overview the 2016 range and meet some of the people responsible for the products.
The senior design engineer for Avanti bikes, David Higgins, proudly spoke about the new range of road bikes from the New Zealand company. Included in the new season line-up is a series of road bikes with disc brakes and the popular Corsa line of frames that have been refined significantly for 2016. He spoke about the work he and his team had done with accelerometers and it pricked up my ears because I was aware of the benefits (and challenges) of getting real world data from bikes using technology that measures at frequencies of 5,000 hertz. After our initial discussion, Higgins went on the record to talk through the experimentation that Avanti went through before deciding on the final specification of the latest line of bikes. Here is a transcript of that exchange.
Interview: David Higgins – on Avanti bikes
– By Rob Arnold
24 June 2015
RIDE: I’m with David Higgins from Avanti. He’s the senior design engineer. We’ve just been through the 2016 Avanti range; there are a few changes coming up and while David was showing it off to RIDE we got talking about the use of accelerometers and strain gauges and cameras – and all sorts of things – to work on compliance of frames. There are three primary road bikes in the  range and each have significantly different qualities…
I’m going to get David to talk a little about all of the work that they’ve been doing with accelerometers. I wonder if you could give us a broad overview of how you’ve come to make a frame more compliant because we often hear that they are compliant but the road feel is negligible unless you’re going from one bike to the next. What have you learned?
David Higgins (Avanti): “One of the key things [with] a project we started a few years ago now is to create a data acquisition tool that enables us to really analyse and look at what’s happening to the bike in a real [riding] condition. In the past the only way we’ve been able to do this is by static testing – so, testing a frame or a fork either together or individually on a test machine – which doesn’t necessarily replicate real world riding situations.
“When we’ve been developing our new range of bikes – from the Corsa family, the DR initially and then the SL the super light bike, and now the Corsa ER which is the endurance road bike… we use this data acquisition tool to look at the frame and the fork and the seatpost etc. And we riding that in real world local conditions.
“The type of roads we get in New Zealand and Australia are very different to European roads and we’re trying to create a frame which dampens those vibrations that we get and improves the ride [quality], as well as reducing fatigue over the longer rides. That’s what this endurance road bike is all about, the long rides.
“This tool we have is motorsport-derived data acquisition system which includes several mini sensors that we put on the bikes. The main ones we use for vibration is the accelerometer.
“We’ve got some very high frequency accelerometers which are mounted at the road inputs – so at the axle points, the chainstay axle and on the fork.
“Those accelerometers read the road inputs and when we use standardised wheels across each frame we can test all our bikes – and our competitions’ bikes – to look at the real dampening that’s happening.
“We also have accelerometers mounted at the touch points of the bike, where the inputs for the rider are: at the saddle point and the handlebars. So we can very easily see in the data the dampening, or vibration, or the force acceleration from the axle input to the rider input.
“We can really look at changing the carbon lay-up of the frame as well as the tube shapes on the frame to improve it… the input you get from the road is much more significant than the input you get at the rider interface.”
I think it’s important to explain the degree of the testing you’re doing because otherwise it’s just anecdotal evidence – you’re just trying to say, ‘Well, the theory is that the bike is more compliant…’ We’re going to get some of these graphs from the testing and compare the DR vs the SL vs the ER… and hopefully we’ll be able to present those by the time the magazine comes out. But when you’re devising these tests, I queried that perhaps – on the superlight bikes – the sheer bulk of the attachments might alter the ride qualities. You’re pretty confident that won’t happen?
I guess what we’re trying to do is negate any questions or doubt that comes from these testing protocols. You would have considered it all…
“Yeah. So, typically, most of the vibration dampening through a frame doesn’t happen at major joints so we have bulk around, say, the chainstay and seatstay joins, the bottom bracket, the seatstay to seat tube… that’s not where dampening occurs.
“Dampening occurs in the longer, slender [tubes] when you allow them to ‘bend’, essentially, in certain directions. And that bending is what creates the vibration reduction.
“We can tune the shapes and tune the lay-ups in those sections to reduce that dampening.”
Let’s talk about the tuning of lay-ups: we’ve often referenced it in bikes tests – ‘We’re going to change the carbon lay-up to make it the ride quality that we want…’ Talk us through what you’re doing in that process.
“These days, inside a frame, 99 per cent of the carbon is what’s call uni-directional. In the past you might have seen a fabric type situation where you have carbon plies going in multiple directions and weaved into a fabric which isn’t as efficient type of fibre… by having that capability now – and the fact that most of the frame is built around uni-directional fibres – we can tune the directions of those fibres a lot more than we have been able to in the past.
“And so, by doing that, we can change how a tube bends.
“By changing the lay-up, whether it’s zero, 90, 45, 60 degree angles, etcetera, you can tune in stiffness. That’s what we’re changing, those directions and also the number – the quantity – of plies to allow things to bend.
“Across a tube that tapers, the fibre drop offs might go from four plies to three to two… we can change all of that.
“There’s an infinite number of possibilities that you can have to change how a tube performs and that’s what we test when we use the finite element analysis software which is a structural simulation type software where we can put in the lay-up, test it inside the computer, and see what’s going to happen.
“Then we create that lay-up, put it on a bike, put the data logger on the bike and test it in real life. That’s the detail that we go through.”
From the computer to the real world accelerometer testing, are the numbers similar?
“Yeah. It’s not exact – you can simulate everything inside the computer – but because we have that data acquisition tool, we know the inputs. We know the forces that we’re playing with on a real road. We’re not just guessing what that is, we can see it. And we input those load cases into the FEA software… it’s like a process where, over the development of the bike and the years having that tool, we can get much closer to the ‘perfect’ situation.”
To go back to the testing protocols, we’ve got the accelerometers and you’ve synched them with cameras and synched it with GPS so you know the road surface, you know where the variation in road surface is, and you’ve tested it on New Zealand roads… is that how it work?
“Yeah, we do the majority of our testing and development at that level on New Zealand roads but then we also do testing – not with the data acquisition tool but rider testing in Australia with the Avanti Racing Team. We do it the roads of both countries. But New Zealand has the more extremes; let’s just say our course roads are very, very course – more so than in Australia. So by looking at that and testing it across both smooth tarmac, slight chip, and course chip roads we can cater for the whole; what you’ll get in Australia as well as New Zealand.”
And this was developed with Motrec?
“The data acquisition head unit that we’re using is a Motec system, an Australian company, and they are the world leader in motorsport data acquisition tools. They’re used across all categories of motorsport, all the way from the club race all the way up to Le Mans. It’s exclusively used in V8 Supercars.
“Their tool allows for an incredibly large number of sensors. The number we’re using on a bike is small in comparison to what the system is capable of.
“To run you through the sensors we have on the bike – and we use this system across mountain [bikes] and road [bikes]: we have the four main high frequency accelerometers and then we have a fifth accelerometer inside the head unit which is tri-axial so it does three directions, we have a gyro sensor which measures roll, we have a GPS sensor, a camera with synch and we have linear potentiometers which measure shock travel for the mountain bikes, and there’s a wheel speed sensor too.”
And the measurements are in what unit? Or, to what degree can you measure?
“Accelerations are measured in Gs, so we’re measuring up to 5,000 hertz which is 5,000 samples a second, that’s why we can measure every single bump, every single stone on the road we can see the input and the output for. And we can average those across a section and look at the average value of dampening.”
How greatly did you change, for example, 2014 bikes to 2016 bikes because of what you’ve learned from this testing?
“Oh, it’s huge. It’s a big change. And being able to really analyse it and look at the numbers as opposed to how it was before we had these tool. It’s a huge change.”
And the end result is a rider that’s happier…?
“Yep, a rider who can go longer and have more energy at the end of the ride – for that sprint…”
– Interview by Rob Arnold