Bike Roll-out tests in Gunnislake

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Mick F
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Bike Roll-out tests in Gunnislake

Post by Mick F »

Done it.
I took four bikes up to the Station and let them roll. Barbarella, MTB, RSW16 and my Mercian.

Please watch the movie - pardon me nearly, but not quite hitting the kerb! - and I'll be pleased to take any questions.

I paced out the distances with long paces about 1 metre each. Watch the movie for the results!

http://www.youtube.com/watch?v=D1mUNRtbQbQ
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Re: Bike Roll-out tests in Gunnislake

Post by geocycle »

Nice! So is this largely a function of wheel diameter? Would weight give more momentum once inertia is overcome hence MTB>Barbarella? Looking forward to hearing CJ's views.
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Re: Bike Roll-out tests in Gunnislake

Post by Mick F »

Weights:
Barbarella.......16.8kg
MTB................14kg
RSW16............19kg
Mercian..........11.3kg
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Re: Bike Roll-out tests in Gunnislake

Post by geocycle »

Thanks. I'm surprised how light the MTB is relative to Barbarella. Even though you've minimised the variables by using the same slope in the same conditions with the same rider, it is still hard to decide what are the key factors explaining the result (wheel diameter/weight, tyre/weight/pressure, hubs, overall mass and acceleration....). What are your thoughts?
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Mick F
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Re: Bike Roll-out tests in Gunnislake

Post by Mick F »

My thoughts are the only thing possible - friction.

I wasn't going fast enough for any wind resistance and it wasn't windy either. I wasn't going fast enough for anything to affect the roll-out other than outright friction.

What this friction is caused by, can only be tyres and hubs. RSW16 and Barbarella have hub gears full of oil, so that may account for Barbarela underperforming. RSW16 is explained by small balloon tyres and perhaps a pair of inefficient hubs. Also, RSW16 has a hub dynamo - although it wasn't switched on, it still provides a little drag evidenced when you spin the front wheel off the ground, you can feel the magnets attracting. The wheel always comes to rest with a 'twitch' rather than just rotating gently to a standstill or reversing to get the heaviest bit at the bottom.

I'm not really trying to prove any of the above, they're just my thoughts and perhaps other people could enlighten us with their thoughts. It was very interesting to see the distances they rolled, and I'm not surprised that Mercian was the clear winner.

The next test is to try different tyres on Mercian as it has 700c wheels. Barbarella is on 27" so not so easy to get others.

Edwards is hoping to send me some 25mm tyres for Mercian to try, but I have an idea. I have a pair of Mavic MA3(?) wheels on Campag Mirage cassette bearings. It would be a simple thing to change over, I even have more 20mm tyres and tubes to fit. Maybe do another test later this week to see if a change of wheels makes any difference.
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Re: Bike Roll-out tests in Gunnislake

Post by neilob »

With painful memories still of late-1960s division road races in which we grovelled up Gunnislake Hill, I was really interested in this thread from the title then realised it was a test held in the car park of the station rather than one starting from the station. Perhaps the next phase of the test would be to measure terminal velocity of your four bikes as they fly off the road at the bottom into the Tamar??
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Re: Bike Roll-out tests in Gunnislake

Post by meic »

It is very early to be speculating on conclusions when you havent really collected any data yet after adjusting the variables.
You have one point each on a graph for four different curves!
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Re: Bike Roll-out tests in Gunnislake

Post by hubgearfreak »

Mick F wrote: Barbarella have hub gears full of oil, so that may account for Barbarela underperforming.


do you mean grease?
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Re: Bike Roll-out tests in Gunnislake

Post by hubgearfreak »

Mick F wrote:I wasn't going fast enough for any wind resistance


at any speed there's wind resistance.

Mick F wrote:that may account for Barbarela underperforming.


this comment, for me sums up the pointlessness of the survey. you're out to find results that fit your theory. even with the best will in the world, you can't be nuetral in these tests. this isn't a dig at you mick, it's simply human nature. see the link below - even the very same thing can be percieved as different by the brain, it's a very complex thing.

http://www.sciencedaily.com/releases/20 ... 101053.htm
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Re: Bike Roll-out tests in Gunnislake

Post by al_yrpal »

I think what you have done is brilliantly simple. I wish I could get you to test my touring bike to see how it compares, but you are too far away.

Did the MTB have full knobblies or was there a central smooth bead, I think that could make a big difference?

Presumably the car park has a downhill slope followed by a flat or slight 'up' incline?

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Re: Bike Roll-out tests in Gunnislake

Post by geocycle »

Thinking about it again, your body position must hve made a major difference. The aerodynamic contrast between drops and the RSW at the extremes must be very marked even in still weather, whereas the mtb and barbarella might be closer. Did you try and keep a similar profile?
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Mick F
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Re: Bike Roll-out tests in Gunnislake

Post by Mick F »

I understand all the comments and the observations.

All I did was to sit on the respective bikes in the normal way you would sit on that particular bike and let them roll. I doubt I got above 5mph.

The slope was even then levelled out, no wind or weather and nothing other than bike geometry and design.

The distances I recorded had no bias and no predetermined thoughts from me. I understand the idea of perception of the results, but TBH, I was surprised at them.

All I've done is to report the facts.

I said on my previous thread about not lying. It was as I have shown.

Tomorrow, I will go back to the station and repeat the Mercian trial with Mavic/Mirage wheels. Same tyres, same bike, same me in same clothes.

BTW, Hubbers, the Nexus on Barbarella and the SA hub on RSW gears have oil in them, not grease.
Mick F. Cornwall
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Re: Bike Roll-out tests in Gunnislake

Post by Mick F »

neilob wrote:With painful memories still of late-1960s division road races in which we grovelled up Gunnislake Hill, I was really interested in this thread from the title then realised it was a test held in the car park of the station rather than one starting from the station. Perhaps the next phase of the test would be to measure terminal velocity of your four bikes as they fly off the road at the bottom into the Tamar??
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Re: Bike Roll-out tests in Gunnislake

Post by DavidT »

Meanwhile British Transport Police (Tamar Valley Division) are investigating the reports of strange markings appearing all over one of their car parks...... :lol:
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Re: Bike Roll-out tests in Gunnislake

Post by hubgearfreak »

Mick F wrote:BTW, Hubbers, the Nexus on Barbarella have oil in, not grease.


thanks for clearing that up. is that standard or something you've done? 8)
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