If you've already got a load of data on Strava that you can cut & paste into Excel, it's simple enough to calculate your own personal "Naismith's Rule" if you download the regression add-in.
Search found 2866 matches
- 28 Mar 2024, 4:59pm
- Forum: Health and fitness
- Topic: Calculate avg speed on a flat ride
- Replies: 8
- Views: 300
Re: Calculate avg speed on a flat ride
- 28 Mar 2024, 11:13am
- Forum: Campaigning & Public Policy
- Topic: Over-powerful LED lights
- Replies: 101
- Views: 6750
Re: Over-powerful LED lights
1. I wonder whether police stats are sufficiently detailed to reveal an effect that my be small in terms of all-cause road deaths but quite large in terms of deaths related to headlamp design. I also think that any advantage of better visibility will have been consumed in the form of faster driving rather than reduced accident rate, and that that possibility won't have been researched.
2. There is no sharp binary boundary at the edge of the beam pattern, lamps that are brighter in the middle of the beam will also be brighter at the margins.
3. Degree of dazzle doesn't just depend on the location of the viewer relative to the beam, it also depends on the direction of the viewer's gaze. From any given position, you may be able to see to the side, but the vicinity of the car with the offending lights is obscured, and that makes it difficult to be sure of avoiding hitting it. If you increase the brightness within the beam too much when the light level around the car remains unchanged then this difference will exceed the dynamic range of the eye.
4. I didn't know that the UN had a finger in the vehicle regulation pie, considering that we left the EU so that we don't have to be told what to do by forriners, it's interesting that we're happy to be involved with them. Mr. Konstantin Glukhenkiy is the contact, I wonder if he's amenable to submissions from lay road users.
2. There is no sharp binary boundary at the edge of the beam pattern, lamps that are brighter in the middle of the beam will also be brighter at the margins.
3. Degree of dazzle doesn't just depend on the location of the viewer relative to the beam, it also depends on the direction of the viewer's gaze. From any given position, you may be able to see to the side, but the vicinity of the car with the offending lights is obscured, and that makes it difficult to be sure of avoiding hitting it. If you increase the brightness within the beam too much when the light level around the car remains unchanged then this difference will exceed the dynamic range of the eye.
4. I didn't know that the UN had a finger in the vehicle regulation pie, considering that we left the EU so that we don't have to be told what to do by forriners, it's interesting that we're happy to be involved with them. Mr. Konstantin Glukhenkiy is the contact, I wonder if he's amenable to submissions from lay road users.
- 26 Mar 2024, 4:55pm
- Forum: Campaigning & Public Policy
- Topic: "Why is the right at war with cyclists?... "
- Replies: 27
- Views: 1459
Re: "Why is the right at war with cyclists?... "
It's not about cyclists, it's motorists. Here's how they react when they're held up by road works. I recall a similar article about tractor drivers not so long ago.Jdsk wrote: ↑25 Mar 2024, 9:12pm "Why is the right at war with cyclists? We’re not ‘wokerati’ – we’re just trying to get around":
https://www.theguardian.com/commentisfr ... get-around
Jonathan
- 26 Mar 2024, 4:48pm
- Forum: Campaigning & Public Policy
- Topic: "Why is the right at war with cyclists?... "
- Replies: 27
- Views: 1459
Re: "Why is the right at war with cyclists?... "
Really? You don't say.a.twiddler wrote: ↑25 Mar 2024, 10:52pmAbove all don't dare to stand up for your rights, you'll be labelled as a trouble maker.
Indeed.a.twiddler wrote: ↑25 Mar 2024, 10:52pmIt's got all the sophistication of the school playground, bashing those who are identifiably different from the herd to distract from the failure of those who supposedly, aren't.
It's an old old technique, yet people still seem to fall for it. It's not just cyclists getting "othered".
- 25 Mar 2024, 6:33pm
- Forum: Health and fitness
- Topic: Why are the general population resistant to getting fit?
- Replies: 97
- Views: 5061
- 24 Mar 2024, 1:34pm
- Forum: Campaigning & Public Policy
- Topic: Over-powerful LED lights
- Replies: 101
- Views: 6750
Re: Over-powerful LED lights
"27% say the design of brake lights on cars are ‘more style over substance’"Diatom wrote: ↑24 Mar 2024, 12:49pmreport on blinding car lights ( https://www.theaa.com/about-us/newsroom ... headlights )
This is a problem in general, not just with lights, or even just cars. These days the design of almost everything is mainly determined by what makes a winning marketing gimmick, and less and less by what's safe, or practical to use, or even useful. Another example would be the touch screens that take 30 seconds of searching in a menu to find something you could previously reach out and feel for without even taking you eyes off the road. Even when there is a prima facie reason to suppose that something has a safety benefit, there's scant regard payed to investigating the possibility that its presumed benefit may be completely undermined by risk compensation in practice before it gets put into production.
"there is an acceptance that having brighter lights is better for road safety"
Better at shifting responsibility from those who want to drive faster onto those who are dazzled by the lights.
- 20 Mar 2024, 2:23pm
- Forum: Health and fitness
- Topic: Atrial Fibrillation...Should We Worry
- Replies: 102
- Views: 13137
Re: Atrial Fibrillation...Should We Worry
I can do nothing but sit in this chair all day and every day, it's ruining my life. That wasn't the case when they offered it to me in July 2013.
- 20 Mar 2024, 12:44pm
- Forum: Health and fitness
- Topic: Atrial Fibrillation...Should We Worry
- Replies: 102
- Views: 13137
Re: Atrial Fibrillation...Should We Worry
I was offered an ablation for my AF ten years ago, and I'm still waiting for it.brianleach wrote: ↑20 Mar 2024, 7:19amI was only offered 1 ablation and my cardiologist expressed some surprise that I had stayed in SR for longer than he expected after that ablation.
- 20 Mar 2024, 12:05pm
- Forum: The Tea Shop
- Topic: Food poverty-the way out
- Replies: 756
- Views: 27949
Re: Food poverty-the way out
Depressive Realism: The perception and judgment of depressed people tends to be more accurate because they are less prone to self-serving bias.simonineaston wrote: ↑20 Mar 2024, 11:40am What exactly is there to be happy about? Let's recall that our primate brains are inclined towards two overarching tendancies - opportunism and optimism. Thus any thoughts we have will tend to err on the side of imagining that 'it will be alright on the night'... the likeilhood is that it won't and anyone with half an ounce of sense should have realised that by now.
Off for a nice restorative cycle ride now
- 19 Mar 2024, 6:02pm
- Forum: Health and fitness
- Topic: Atrial Fibrillation...Should We Worry
- Replies: 102
- Views: 13137
Re: Atrial Fibrillation...Should We Worry
Very common.
In the days when I could shrug off my AF I didn't take much notice, but since my AF got much worse in 2020 I've had to sleep on my right side only for about the last two years because it's completely intolerable otherwise.
It's fairly common to need 2 or even 3 for AF, and then a PVI is only about 70% successful IIRC. On the other hand, a CTI for atrial flutter is much quicker, simpler, and higher success rate though.
- 19 Mar 2024, 2:25pm
- Forum: Bikes & Bits – Technical section
- Topic: SKS Chainbow?
- Replies: 26
- Views: 1656
Re: SKS Chainbow?
Tucking trousers into socks is no use, when I bend my legs the bottoms of my trousers ride up above the top of my socks. Cycle clips aren't much fun either unless I want them around my calves.
Before I switched to Ron Hill Bikesters, I used polycotton walking trousers, and modified a pair for cycling in. They had a zip across each leg just above the knee with a gusset sewn in behind, so that when I got on the bike I opened the zip and the gusset allowed the leg to bend without riding up. I then had tabs with Velcro sewn on the bottoms like the ones on waterproof over trousers. Very convenient, but it takes a bit of time to make them.
I had a strong wind from the front right quarter blow my Lycra Bikesters into the chainring once.
Before I switched to Ron Hill Bikesters, I used polycotton walking trousers, and modified a pair for cycling in. They had a zip across each leg just above the knee with a gusset sewn in behind, so that when I got on the bike I opened the zip and the gusset allowed the leg to bend without riding up. I then had tabs with Velcro sewn on the bottoms like the ones on waterproof over trousers. Very convenient, but it takes a bit of time to make them.
I had a strong wind from the front right quarter blow my Lycra Bikesters into the chainring once.
- 19 Mar 2024, 10:49am
- Forum: Bikes & Bits – Technical section
- Topic: how slow do they get?
- Replies: 17
- Views: 1120
Re: how slow do they get?
Given that 'unpunctured' tyres still go flat eventually, it begs a definition of what constitutes a puncture.
- 18 Mar 2024, 6:52pm
- Forum: The Tea Shop
- Topic: Heat in the home
- Replies: 2297
- Views: 134415
Re: Heat in the home
I think I must have been typing that from memory instead of checking.axel_knutt wrote: ↑16 Jan 2024, 5:39pmI measured the cost of running the heating continuously a few years ago, and found that switching off for 7 hours overnight saved about 12% off the gas consumption.
So, the first time I measured this was for 8 weeks in November and December 2017, and alternated the heating between timed and continuous each week to minimise the effect of weather, on the basis that any temperature variations won't be synchronised with the measurement periods. Comparing the ratio of average fuel consumption to average temperature difference for the 4 timed weeks and 4 continuous weeks, I got a 7.9% (not 12%) reduction in consumption with the heating switched off at 00:30, and back on again at 07:30.
This winter I repeated the measurement but by a different method: running the heating continuously for the whole winter and comparing it with the timed running during the three preceding winters. To account for variations in the weather, this time I normalised the fuel use to the heating load in degree days. The result this time was an average consumption of 350W/K on timed, and 383W/K on continuous, giving a similar saving of 8.5%. (Heating load measurement)
I also have a model of the house and heating system on the computer (in the form of a virtual analog computer running on Spice), so I thought it would be interesting to compare what that says against the actual measurements. This time I don't need to worry about the effect of weather variations, because I can repeat the simulation with exactly the same weather temperature for both timed and continuous operation. The result I got this time was a saving of 9.47% using weather data for Oct 2021 and 9.53% for Jan 2022, those months being chosen so as to cover a wide range of heating loads.
In view of the similarity of the results for all three measurement methods, I think it likely that the results are about correct.
------------ooo-----------
Diffusivity is a property that's normalised to a standard dimension, in the same way that density is weight normalised to a standard volume. What you are arguing is the equivalent of saying that the density of steel has no effect on the weight of a bike because it's just a property of the material, or that the contents of your bath weigh the same as the contents of the local reservoir because the density of the water is the same in both.roubaixtuesday wrote: ↑16 Jan 2024, 6:30pmIf you believe thermal diffusivity is "absolutely fundamental" please answer the point about how it is identical for walls regardless of their thickness.axel_knutt wrote: ↑16 Jan 2024, 5:39pm
Thermal diffusivity is absolutely fundamental: it’s what determines how fast a material can change temperature in response to a change in surrounding temperature, and how fast a change in temperature can propagate from one side of it to the other. What I said above all assumes a static system, but the conditions never are static: as weather and/or heating level change the thermal diffusivity of the walls determines how fast they can follow, and hence the extent to which MRT and level of radiant asymmetry vary, causing transient variations in thermal comfort.roubaixtuesday wrote: ↑15 Jan 2024, 7:54pmThermal diffusivity is a material property. It tells you almost nothing about how a building responds to temperature changes.
A wall constructed of a single sheet of paper and a wall constructed of 10 metre wide coastal redwood trunks would have the same thermal diffusivity.
It is a property of a material, not a property of a building, or even an element of a building.
In the same way that the performance of bicycle frame depends on it's geometry, tube thickness and other design parameters, not just the youngs modulus of the material.
One advantage of computer models is that you can test hypothetical what-ifs that wouldn't otherwise be possible: On the left, the inside and outside temperatures from data logging thermometers are plotted in green and blue respectively, and in red you can see that the modelled inside temperature is a reasonably good fit for the measured data. On the right is the same plot again, but this time it shows the result when I remove all the thermal inertia from the model: unsurprisingly the temperature plummets as soon as the heating switches off, because there's no longer any heat capacity in the building to maintain it.
We can also look at how the thermal properties of the wall affect the heat transfer through the wall: Here, the red trace is internal air temperature, and then from top to bottom are the temperatures of the internal surface of the internal leaf of the cavity wall, the external surface of the internal leaf, the internal surface of the external leaf, the external surface of the external leaf, and finally, the outside air temperature in blue, which I've set to be constant so as not to obscure the effect we're looking at.
What you can see is that the thermal resistance and heat capacity of the brickwork combine to create a low-pass filter, smoothing out the temperature variations between the inside and outside of the wall. Note that not only has almost all of the temperature variation gone, but there's a phase shift: minimum temperature on the inside occurs at 07:30, immediately before the heating comes back on, but the outside surface of the wall doesn't reach minimum temperature until gone midday. All this effect disappears if you don't take proper account of the way that the thermal resistance and heat capacity combine to influence the way that heat diffuses through the wall.
The reason I built the model in the first place is that I was interested in exploring the transient effects as the heating switches on and off.
I don't see what you're getting at, I haven't said that there's no convection or conduction in the room, and I don't see the relevance of conduction through the wall. The point I was talking about is that people are more sensitive to radiant heat, and that asymmetric radiation causes thermal discomfort. Radiant heat's not irrelevant, or even insignificant.Jdsk wrote: ↑17 Jan 2024, 12:13pmI'm all in favour of thought experiments in discussing the physics.axel_knutt wrote: ↑16 Jan 2024, 5:39pm ...
If the walls of a room were at body temperature, then the radiant heat passing from the body to the walls would be exactly balanced by the heat radiated from the walls to the body. Walls colder: there’s a net heat loss, hotter and there’s a net heat gain.
...
But in this one is there any heat flow from the interior surface of the walls to the walls and the outside world? And is there any conduction and convection within the room?
Thanks
Jonathan
See here: An excessively warm ceiling is the most uncomfortable, followed by a cool wall (which is the problem I have in my dining room).
- 17 Mar 2024, 3:06pm
- Forum: Campaigning & Public Policy
- Topic: LTN politics
- Replies: 54
- Views: 3591
Re: LTN politics
The review was published this morning.
https://www.gov.uk/government/publicati ... ood-review
https://www.gov.uk/government/publicati ... ood-review
- 17 Mar 2024, 1:23pm
- Forum: The Tea Shop
- Topic: Just how long will it take to turn this ship around?
- Replies: 103
- Views: 2949