Derailleur in Kilo allowed?

MishMash95

Had this random question and couldn't really find much information on it. So, I Was wondering whether derailleurs were actually allowed in track cycling if riders wanted them?

I understand the aerodynamic/chainline efficiency gains of not having one however I feel like it would ultimately yield a faster time if you could progressively shift accelerate, rather than needing to dump 2000w+ just to get the bike rolling. As lots of pro road racers, especially leadout men have pretty darn good 1-minute powers, heck I feel even something as low as 700w for a minute could yield a pacey time if you had all the gear and a lower cDa. It seems that most of the muscle bulk is used for that short, sharp initial acceleration, which seems like its overkill to an extent.

(Regarding things like gear crunching, I feel if you built a system specifically for this purpose, with only 2 or 3 gears, it could be built to be better at switching under load). If they are objectively banned, what is the main reasoning behind it?

Or is it just one of those Olympic restrictions that enforce a certain "style" when performing an event?

imposter2.0

Not sure if you've fully grasped the nature of track cycling - which is that the bikes are single speed, fixed wheel.

MishMash95

Imposter wrote:

Not sure if you've fully grasped the nature of track cycling - which is that the bikes are single speed, fixed wheel.

... I know that is how it is performed now, I was simply asking if you HAD to use a bike which followed those specifications. Clearly, i'll take that reply as meaning there is no other option, so to re-iterate what I asked in my first question, why is this the case?

Efficiency gains aside, for a short event like the kilo, I would imagine that having an option to shift would ultimately be more efficient than having to grind off the start block (Not only from the lower power requirements, but indirectly this would mean riders who are smaller frame could gain an aerodynamic advantage at the cost of less raw power).

I understand how it is, I merely wanted to create a bit of discussion into the mechanics and reasoning behind it, and whether if all you wanted to do was get the fastest Kilo, would track bikes (as they are now) even be the best option?

fenix

There was a british Track racer who did use two gears - I think Shaun Wallace ? It was something clever like one sprocket was loose and when it tightened up it brought into play the higher gear.

I've never heard of anyone else using this since so I guess it's banned.

imposter2.0

If you are taking part in a track event, then yes obviously you have to use a track bike which conforms generally to the required spec. And the minimum required spec (amongst other criteria) is single speed, fixed wheel and no brakes.

That kind of rules out derailleurs and - by extension - shifters.

Most kilo riders are sprint specialists, so are not going to be 'small frame' types. You can obviously speculate whether a road-going TT rig might be faster round a track than a track kilo bike for the same rider in the same event, but the speculation is kind of pointless in my opinion as it's never going to happen.

DeVlaeminck

Yes when you think about it it'd be pretty easy to design a bike to beat the kilo world record if it weren't for those pesky equipment regs.

Matthewfalle

Imposter wrote:

You can obviously speculate whether a road-going TT rig might be faster round a track than a track kilo bike for the same rider in the same event

Any track riding TTers on here fancy doing a completely unscientific experiment along those lines when they are next down their track? Be interesting to see the differences.

Even if it’s normal track bike vs normal oak bike set ups.

imposter2.0

The guys at Aerocoach might have the answers, I suspect. They are the only ones I've ever seen running road-going TT bikes in a velodrome, so may have some comparative data.

Pross

It doesn't take long to find the answer to this in the UCI technical regulations

Freewheels, multiple gears and brakes are not permitted for use on the track during competition or training.

thistle_

Fenix wrote:

There was a british Track racer who did use two gears - I think Shaun Wallace ? It was something clever like one sprocket was loose and when it tightened up it brought into play the higher gear.

Like a clutch? Are they in the UCI regs? :roll:

timothyw

It would be fairly easy to perform an investigation yourself with a turbo.

Do a 1 minute effort from stopped, take your average wheelspeed over that minute (using gears).

Pick a gear perhaps 1 or 2 below the top gear you reached in the first effort, repeat the effort but stay in that gear. How does your average wheelspeed compare?

I'd have thought you'd be slightly faster with gears, yep, but I doubt many people of a competition standard would want to risk a missed shift even if gears were an option. Kilo riders will also be much better than you or I at spinning a high cadence while still getting a lot of power out.

If you look at Pervis' WR splits - 17.671/12.418/12.732/13.482 - you can see that the acceleration is actually a pretty small part of the effort as a whole (in terms of duration) - the first lap is only 5 seconds slower despite coming from a standing start(!) - so you can imagine that trying to shift through the gears over that small period of time would in of itself disrupt the acceleration unless you had, well, better bike gears than I've ever used.

Doing the sums, that second lap split gives you a speed of 72.48kph - it's a lot harder to find numbers for a top end road sprinter in terms of peak speed, this article quotes 76kph as Sagan's top speed last year https://www.cyclingweekly.com/news/raci ... ing-359140 - the numbers are in the same ball park despite the rider having the benefit of gears.

There's obviously a bit of give and take in those numbers - Sagan has the benefit of a leadout, perhaps favourable wind and slope, no corners, whereas Pervis had the advantage of fresh legs, a nice smooth track and tyres at 180 psi.

I guess the point is that I don't think Kilo riders would hit much higher speeds with gears, and they're already accelerating to those speeds ridiculously quickly - unless someone comes up with a better way for gears to shift smoothly and without losing power I think they'd be more detriment than benefit.

Pross

Presumably the fade at the end would also be longer if you hit top speed earlier, those splits suggest that top speed can only really be maintained for around 500m.