Re: Wellington Crash Video

Postby CrustyMTB on Thu 13/Dec/12 10:13pm

thelivo wrote:Although - an interesting point is raised by that thread. What do you reckon the stopping distance is on a bike as opposed to a car at 45 kmh?

Car - Big contact patches, big brakes, ABS (sometimes), no stability issues when braking hard - but heavy
Bike - Small contact patches, small brakes but MUCH lighter.

Not really going anywhere with this just interested.

Lower speeds on a bike too (most of the time). But on the roadie I reckon I can match the braking of most cars, on the MTb there's no contest, big grippy , suspension and hydraulic disks I can out brake anything on the road (apart from other bikes).

Catmanz, double collies fractures? Nasty mate, heal up.
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Re: Wellington Crash Video

Postby sifter on Thu 13/Dec/12 11:39pm

pm wrote:ouch, i didn't enjoy watching that (nearly didn't click the link cause i knew it was going to be unpleasant viewing).
good to hear you got off relatively lightly.

i only ever use the bus lane through there if traffic is really slow and even then i go through slowly. most times i sit out in the main traffic lane as its a lot safer. in the bus lane you first have to deal with cars cutting in on top of you when they want to turn up towards aro, then you have to deal with cars pulling out from curtis st (and sometimes turning across into curtis st), then you have the likes of this with cars pulling out in front of you. i'm normally at least as fast as the traffic so not holding up anyone but myself. once around that corner safely i'll pull over into the bus lane as the road tips up slightly and my speed eases off so nobody gets impatient.

really its 50m of road that combines so many of the fundamental failings of our road network with regard to accommodating cyclists. whilst its good to hear that the driver is being charged, i'd also like to see road designers taking responsibility for the situations they create - not that i can think of a better way of organising this area, but then that's not my job.

edit: actually, i somewhat retract that blame on the engineers - really the blame is on the drivers who just can't get their heads around the concept of sharing the road with cyclists and accommodating the differences. but i've pretty well given up on that changing so unfortunately we need roads designed around it. its just a worse version of the way people pull out in front of other cars, making some weird assumption that it will be ok for no reason other than because it suits their purposes



It just dawned on me that I can usually get up to the X-intersection between the two tunnels without losing too much momentum. I wonder if hooning up there and then dropping down to the tunnel is a goer on a regular basis? I will try it out tomorrow (on Simonk's bike!!!) and report back. Will be *difficult* to avoid sneaking out the bottom though... :blush:
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Re: Wellington Crash Video

Postby thelivo on Fri 14/Dec/12 8:54am

Short powerclimb to get the heartrate pumping on the way down to town - nice!
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Re: Wellington Crash Video

Postby thorg on Fri 14/Dec/12 9:02am

CrustyMTB wrote:Lower speeds on a bike too (most of the time). But on the roadie I reckon I can match the braking of most cars, on the MTb there's no contest, big grippy , suspension and hydraulic disks I can out brake anything on the road (apart from other bikes).

Only if you can brake the laws of physics. bikes = 0.6G cars =1G (with ABS it's 2G, or more) At best a bike may approach 1G, in ideal circumstances, with a VERY skilled rider. It's not about the contact patch or brakes, it's the COG trying to throw you over the bars which limits maximum forces on a bike.

answer provided by Google.
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Re: Wellington Crash Video

Postby sifter on Fri 14/Dec/12 11:17am

sifter wrote:It just dawned on me that I can usually get up to the X-intersection between the two tunnels without losing too much momentum. I wonder if hooning up there and then dropping down to the tunnel is a goer on a regular basis? I will try it out tomorrow (on Simonk's bike!!!) and report back. Will be *difficult* to avoid sneaking out the bottom though... :blush:


Great success, though helped by the fact that I didn't struggle to get across the lane to make the right turn back down to the tunnel.
Would trade again, etc.
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Re: Wellington Crash Video

Postby catmannz on Fri 14/Dec/12 6:33pm

Good news. I got a letter from the police today. The driver has been charged with ''careless or inconsiderate vehicle operation causing injury''.

Score one for the cyclists :thumbsup:
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Re: Wellington Crash Video

Postby piwakawaka on Fri 14/Dec/12 7:44pm

Barbsarama wrote:
pm wrote:really its 50m of road that combines so many of the fundamental failings of our road network with regard to accommodating cyclists. whilst its good to hear that the driver is being charged, i'd also like to see road designers taking responsibility for the situations they create - not that i can think of a better way of organising this area, but then that's not my job.


:withstupid:
Retire some of the old dinosaurs and get some fresh blood in, people who aren't 100% car focused (not necessarily young). How about that new intersection layout at Adelaide road / John St. Gives me the shits :angry:


Can't believe the money they have spent up there and there is nothing for cyclists on what must be one of the busiest cycle routes in Welly, the basin end is garbage as well.
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Re: Wellington Crash Video

Postby nzmatto on Fri 14/Dec/12 9:22pm

I've been too bloody lazy to ride over the past couple of weeks so have been taking the car to work....can't believe I'd normally ride with traffic like that around me. I think I actually felt safer on the bike than I do in the car.
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Re: Wellington Crash Video

Postby fatwombat on Sat 15/Dec/12 1:56am

sifter wrote:
sifter wrote:It just dawned on me that I can usually get up to the X-intersection between the two tunnels without losing too much momentum. I wonder if hooning up there and then dropping down to the tunnel is a goer on a regular basis? I will try it out tomorrow (on Simonk's bike!!!) and report back. Will be *difficult* to avoid sneaking out the bottom though... :blush:


Great success, though helped by the fact that I didn't struggle to get across the lane to make the right turn back down to the tunnel.
Would trade again, etc.


Yeah, I find Raroa Crescent is the best option when I'm riding into town: if I'm doing stuff at the south end or going east of the Hataitai tunnel, I go all the way up over to Aro St; if I'm going to the north end of town or up SH2 I go through the Northland tunnel and down Garden Rd. Initially I thought that Garden Rd would be a bit perilous because it's narrow with lots of parked cars and no visibility for cars coming up, but I've never had a problem (I think I feel safer going down there on the bike than in the car). So the only time I go through Karori tunnel is if I'm going to Kelburn which is hardly ever.
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Re: Wellington Crash Video

Postby sidlomavpa on Sat 15/Dec/12 6:19am

catmannz wrote:Good news. I got a letter from the police today. The driver has been charged with ''careless or inconsiderate vehicle operation causing injury''.

Score one for the cyclists :thumbsup:


:thumbsup:
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Re: Wellington Crash Video

Postby CrustyMTB on Sat 15/Dec/12 9:20am

thorg wrote:
CrustyMTB wrote:Lower speeds on a bike too (most of the time). But on the roadie I reckon I can match the braking of most cars, on the MTb there's no contest, big grippy , suspension and hydraulic disks I can out brake anything on the road (apart from other bikes).

Only if you can brake the laws of physics. bikes = 0.6G cars =1G (with ABS it's 2G, or more) At best a bike may approach 1G, in ideal circumstances, with a VERY skilled rider. It's not about the contact patch or brakes, it's the COG trying to throw you over the bars which limits maximum forces on a bike.

answer provided by Google.

Not to disagree with google, but there are variables missing there, an 8 inch travel slack sledge (late 90's dh couch for instance) with a looong wheelbase relatively low cog, and the ability of the rider to alter through the braking 8 inch hydraulics will pull higher g's than a high sprung front engined SUV on road tyres. If we're talking real world the bikes brakes and pads are also probably better maintained as riding dh on bad brakes is a one time experience.

I'd also factor in that concentration will be higher in the case of the cyclist.
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Re: Wellington Crash Video

Postby nzmatto on Sat 15/Dec/12 12:58pm

for my own understanding here (I really don't quite get it), what does this 0.6g vs 2+g factor mean?
Are we saying that a bike will typically take a longer distance to come to a complete stop from the same speed as it would for a car with ABS? In my mind I'd always considered a bike should be able to stop faster cause there's something like nearly 1.5 tons less of me on a bike to stop.
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Re: Wellington Crash Video

Postby Simonius_Titius on Sat 15/Dec/12 5:04pm

The coefficent of friction is theoretically a simple ratio of downward force/braking force. Weight doesn't affect it so long as the brakes are adequate. Rubber departs from simple theory a bit, so racing cars have fat tyres.

Theoretically a huge truck could brake very well. Achieving that in practise is unlikely because of the difficulty of distributing the braking force for each wheel to be proportionate to the load it carries, this being very variable in a truck.

Motorcycle braking forces of up to around 1g are achievable under test conditions, but consider the histogram of hundreds of rider performances under "Real Rider Performance" here below. These would all be expert riders under test conditions and there is a wide spread, some under 0.6g
http://www.mfes.com/motorcyclebraking.html

Forrester gave 0.67g as the endo point for a road bike.
Asphalt typically can provide 0.7g with the standard tyre used for testing road surfaces.
US bicycle regulations specify 0.5g (peak?)as a minimum.

Beck tested MTB and found they got up to 0.5g overall on concrete road. He explains why his figures are lower than expected:
http://www.beckforensics.com/CMRSC14BeckBicycle.pdf

The better ABS give real-world braking comparable to the best that an expert can do under test conditions, so the bottom line is that in the real word an expert motorcyclist without ABS is very much at risk of running into the back of even an an unskilled motorcyclist with ABS.

Dunno about cars, my 1999 ABS is not that flash under test conditions. In the real world I'm sure it would be adequate to catch out expert cyclists.
Last edited by Simonius_Titius on Sat 15/Dec/12 6:46pm, edited 1 time in total.
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Re: Wellington Crash Video

Postby nostromo on Sat 15/Dec/12 6:00pm

nzmatto wrote:for my own understanding here (I really don't quite get it), what does this 0.6g vs 2+g factor mean?
Are we saying that a bike will typically take a longer distance to come to a complete stop from the same speed as it would for a car with ABS? In my mind I'd always considered a bike should be able to stop faster cause there's something like nearly 1.5 tons less of me on a bike to stop.

Try it; stomping the brake pedal on a modern car stops you pretty damn fast, no way a bike or anything on two wheels can compete, the difference is more so on curves.
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Re: Wellington Crash Video

Postby CrustyMTB on Sat 15/Dec/12 7:53pm

Simonius_Titius wrote:...
http://www.mfes.com/motorcyclebraking.html

Forrester gave 0.67g as the endo point for a road bike.
Asphalt typically can provide 0.7g with the standard tyre used for testing road surfaces.
US bicycle regulations specify 0.5g (peak?)as a minimum.

Beck tested MTB and found they got up to 0.5g overall on concrete road. He explains why his figures are lower than expected:
http://www.beckforensics.com/CMRSC14BeckBicycle.pdf
...

I stand corrected.
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