Is there really an advantage to motors in pro-cyclist bicycles? - Page 1
Forum section: electronics / general

author: Franxois
author_rank: Newbie
timestamp: May 30, 2015, 10:11:44 am
content: I spotted the articles below on the cycling news website where the pro-cyclists are having their bicycles checked for motors. This got me thinking about whether there would really be an advantage to putting a motor in a bicycle?Firstly, the motors and batteries would add weight, cancelling out any power gain (especially in climbing stages).Secondly, a battery (fitted inside a bicycle frame) cannot store a significant amount of energy.A grand tour cyclist uses about 6 MJoule per 4 hour stage ( assuming a constant power output of 400W) compared an 18V power tool battery which stores around 0.1MJoule (1,5Ah)To me it would seem that there would be no advantage to adding a motor to a pro-cyclist bicycle.http://www.cyclingnews.com/news/uci-checks-bikes-of-contador-hesjedal-and-gilbert-for-motors-at-giro-ditaliahttp://www.cyclingnews.com/news/lemond-the-uci-should-use-a-heat-gun-to-detect-motors

author: Rerouter
author_rank: Super Contributor
timestamp: May 30, 2015, 10:19:53 am
content: If there is any downhill at all, then rather than braking they could use the system, or trickle feed at the easier stages to top over the hills at the mean parts,weight is no issue for them, due to regulation they can not make them any lighter, and the weight they can make the bikes is so low that there is plenty of budget for a motor and batteryThey key point is you don't need the thing constantly doing work, even if it only contributes 20W at an uphill stage, that is 20W you have over your competitor, and at the end of a long ride, on the rush to the finish line, well every trickle of power helps,

author: EEVblog
author_rank: Unknown
timestamp: May 30, 2015, 10:40:46 am
content: That would be interesting, but perhaps rather hard to test with repeatable results.

author: EEVblog
author_rank: Unknown
timestamp: May 30, 2015, 10:43:08 am
content: Quote from: Rerouter on May 30, 2015, 10:19:53 amYeah, but the main point would be would the say extra 20W of power be more advantageous than the downside of the extra weight of the stuff?

author: Rerouter
author_rank: Super Contributor
timestamp: May 30, 2015, 10:55:41 am
content: The limit is the bike must weigh 6.8Kg or greater, that never changes, its the regulation, you can buy road bikes all the way down at 2.7Kg with modern materials, so you can see the kind of gap they have room to play with, tell me you could not dream up an assistance style e-bike kit under 4KG?

author: SeanB
author_rank: Super Contributor
timestamp: May 30, 2015, 11:16:00 am
content: Easy to hide the lithium batteries inside the frame when building it, and the major obstacle is hiding the motor assist. Simplest way to check for a motor would be to place all bikes through a magnemometer, pretty hard to shield a supermagnet so there is no external fringing field, and the motor has to be either in the wheel or the pedals to do any assistance, limiting the search area considerably. Otherwise you will need to hire a Xray scanner ( like Mike has) and run the bikes through them before, during and after the race.

author: LabSpokane
author_rank: Super Contributor
timestamp: May 30, 2015, 01:59:54 pm
content: Quote from: Rerouter on May 30, 2015, 10:55:41 amIt's very common now for weight to be *added* to a bike to make the UCI 6.8kg minimum.

author: Franxois
author_rank: Newbie
timestamp: May 30, 2015, 04:25:55 pm
content: Another issue would be, where to hide the motor?The only place would be in the crank which would limit the output power and torque because of the physical space available.

author: LabSpokane
author_rank: Super Contributor
timestamp: May 30, 2015, 07:32:09 pm
content: Quote from: Franxois on May 30, 2015, 04:25:55 pmThe motor fits in the seat tube and interfaces to the crank with a gear. They already exist. Have for several years now.

author: LabSpokane
author_rank: Super Contributor
timestamp: May 30, 2015, 07:49:01 pm
content: Here it is:http://www.vivax-assist.com/en/produkte/vivax-assist-4-0/vivax-assist_4-0.html

author: janoc
author_rank: Super Contributor
timestamp: May 30, 2015, 09:06:56 pm
content: Quote from: LabSpokane on May 30, 2015, 07:49:01 pmWhooa ... I am completely ignorant when it comes to serious cycling, but who is actually the intended legitimate market for a 2700 eur device like this ?! (i.e. not race cheating).I guess that wouldn't be the grandma going shopping on her e-assisted bike. And I somehow don't see serious amateur cyclists using this neither, but perhaps I am wrong.

author: langwadt
author_rank: Super Contributor
timestamp: May 30, 2015, 10:18:45 pm
content: Quote from: Franxois on May 30, 2015, 10:11:44 am400W is high, looks like a stage is roughly 4MJhttp://cat6.trainingpeaks.com/races/tour-de-france.aspxthe energy in a few kg of batteries would make a huge difference.but I don't see how you could hide the noise of a high revving motor and all the gearing to get the torqueneeded at the crank

author: Rerouter
author_rank: Super Contributor
timestamp: May 30, 2015, 10:37:12 pm
content: Also looking at how they are checking for them (removing the seat to look at the bottom bracket), it occurs to me just how easy it would be to have the thing fitted and installed through the steering tube before it is joined, fit an inductive charging coil and the thing should never even be needed to be accessed over the course of a few months of riding, even the charger could be obscured into a bike frame they store the thing in for the night,It would pass there current tests, and be obscured from thermal imagers by the riders own legs reflecting heat off the frames, and if i can dream this stuff up in idle thought, then what about pro cycling teams who have money to throw at very custom bikes?next thought, how do you activate the thing? most riders can comfortably skip a gear and still be in there power band, the bike can directly measure cadence, and could pick up GPS for speed, so if the rider has been in a specific gear for a few seconds engage, or something to that effect,Dipping deeper still, the brake and gear changer cables are fed down the steering tube, so they could directly measure when the brakes are being applied to start charging, and directly what gear they are in, skipping the gps stuff entirely,

author: apis
author_rank: Super Contributor
timestamp: July 12, 2015, 08:01:07 pm
content: Quote from: SeanB on May 30, 2015, 11:16:00 amNot all motors have magnets though, you can have a winding in both the rotor and stator.Quote from: Rerouter on May 30, 2015, 10:37:12 pmcould add some sort of touch controls in the handles as well and possibly a rfid lock so it only works when the right person is using the bike.

author: amyk
author_rank: Super Contributor
timestamp: July 13, 2015, 04:24:20 am
content: Maybe the reason they can't find the hidden motors is that they're not hidden in the bicycle, they'rein the cyclist's legs...

author: apis
author_rank: Super Contributor
timestamp: July 13, 2015, 04:52:17 am
content: Quote from: wilfred on July 12, 2015, 11:45:43 pmHow would anyone else know it's a 2.7 kg bike if it's custom made?

author: apis
author_rank: Super Contributor
timestamp: July 13, 2015, 06:19:07 am
content: Quote from: wilfred on July 13, 2015, 05:48:49 amI assumed it was mostly down to choice of materials, you would then try to mimic the shape of the more common bikes. You don't have to shave of 4 kg of course that would be the maximum possible. But I'm no bike or pro-cycling expert just speculating. I have no idea what scrutineers are able to notice, but ppl tend to not see what they aren't expecting.

author: amyk
author_rank: Super Contributor
timestamp: July 13, 2015, 10:22:12 am
content: The bike must beat least6.8kg, so if it's lighter they would probably put weights in it anyway; the question here being whether those weights contain energy too.

author: fcb
author_rank: Super Contributor
timestamp: July 15, 2015, 12:41:38 pm
content: Do they weigh the bike at the start AND the finish?If they don't, then what about taking a 2.7kg frame and filling it with water or a heavier liquid, then just releasing it as you pootle along.