Cycling UK Forum

TonyR wrote:Much of the advance in LED brightness has been from getting the heat out of the chip better which means attaching it to a good thermal mass and radiator.

Thermal mass isn't going to affect the steady-state temperature, is it.

TonyR wrote: Mounting the chip facing backwards makes that difficult because a good thermal mass and conduction path will get in the way of the beam that eventually goes forward.

Like how the secondary mirror gets in the way in a Newtonian telescope?
Yes, on second thoughts, look how effective a design mounting the LED rearward is; any heatsink can be directly exposed to airflow, keeping the sink smaller or cooler through forced convection cooling---ideally complemented by dynamo power!

TBH, the LED could be mounted in the side of the lamp housing if heat rejection and light obscuration is a real issue for you. My major point was that our being able to see the tiny radiating LED surface directly is what makes them so uncomfortable for us to look at. O&O.

I would be glad of some guidance, if not legislation, on bicycle lights. It is true they are not as powerful as car headlights, but the radiance of the emitting surface is a lot higher with modern LEDs, to the point where it is almost painful to pass another cyclist with a Magic Shine-style light. From this perspective, bicycles are more of a nuisance than cars. If these lights are pulsating, the discomfort is even worse. The car headlight bulbs I have seen contain a mirrored surface to prevent light shining directly forward else they too would be similarly annoying. Batwing-style LED emitters are available, which emit very little forward light, and maybe these are the ones that should be used in bicycle lights. A normal LED could instead be mounted facing backwards, and I have seen this on some bicycle lights. Of course, a good quality reflector is then essential to collect the light and redirect it forwards. Lowering the colour temperature is also helpful, and a lot more pleasant from the rider's vantage in my experience, but the highest luminous efficacy LEDs tend to give off very blue-white light. If people are prepared to sacrifice some efficiency, they could have something a more mellow yellow.

Bicycle lights are never going to be as large as car headlights, but by preventing the emitter surface from being directly visible, and using larger reflectors, things could be made more tolerable, without needing to reduce the intensity of road illumination.

SJSBrompton wrote:I think you'll find our experience of the IRA in the 70s through 90s, and their use of bins as handy places to leave bombs, has something to do with why there aren't any bins on most public transport stations. I hear tourists asking it all the time at Victoria, which, along with Paddington on the same day, was targetted by the IRA in 1991.

Yeah, I remember.

I don't suppose any stations have these any more. Like they don't have bins. The upshot is that I'll have to carry a pile of cycling clothes and shoes around with me, whilst dressed up trying to look smart. As it is going to be pouring with rain tomorrow, it will be a steaming and dripping pile of gear. It is either that, or leave it on the bike and hope that it doesn't get nicked or fiddled with. What is it like on the continent? Are they equally as paranoid? I have long suspected that the lack of bins at train stations was a money saving exercise under the pretence of improving our security.

reohn2 wrote:http://www.youtube.com/watch?v=hpzPmDtkeRo
http://www.youtube.com/watch?v=37Apscp3 ... creen&NR=1

I can't peel myself away.

I thought this was another Jimmy Savile thread.

This 1985 book probably came out too late to help anyone.

531colin wrote:You can use "more than half" of 2 shims to avoid a gap....I wouldn't be happy with a big gap in a thick shim.....

I was contemplating this this very morning. The problem became more complicated as I thought about it because two halves could easily fall down the seat tube, or become lost when transporting the bike, so that led me down the line of buying four shims and offsetting the joins, then gluing it all together.

531colin wrote:Could an adjustable reamer be pressed into service as a gauge?

I'll have to google that. My tool knowledge is very basic. TBH, I don't know any bicycle shops that would be prepared to faff around with this for me.

cycle tramp wrote:What's the seat post made from? If its alloy or steel you may be able to make the diameter of the seat post bigger by hitting it with a hammer and punch across its surface. The punch will distort the metal, making a dent, but the metal around each dent would be pushed up. If you continue to make punch strikes along the surface of the metal the diameter of the seat post should increase... personally i'l never tried it What i have done is simply wrapped lots of electrical tape around the seat post until the diameter was slightly larger than i wanted and then just pushed the seat post in and tighten the clamp. Under pressure the tape became a sticky mess, but the seat post was held securely

Ah, Cycle tramp, you are living up to your alias. Both of those ideas appeal to my ghetto-chic, make-do-and-mend nature, and it is good to know that insulation tape can be employed in an emergency. I think I'll put your idea to one side for the moment, along with the one marked 'deliberately make the inside of the seat tube rusty so as to reduce its diameter'.

I attempt to appear normal when cycling with a purpose, so try to choose clothes that are socially acceptable whilst having the usual quick drying/wind resistant etc properties.
Time and time again, I end up buying golfing clothes. Apart from the risk of looking like Ronnie Corbett, the materials and design often seem more sophisticated. Cycling gear is invariably a garish colour and made of skin-tight spandex, as though training/fitness are the only reasons for owning a bicycle. I don't think I've ever seen anything a bit preppy in the way of cycling clothing that isn't ridiculously expensive. Even the gloves are better. How can it have all gone so wrong? Are there two massive production lines in China that have become crossed, or is Vicky Pollard a senior buyer for a cycling brand?

CREPELLO wrote:There's a long and interesting thread about Karrimor and the event jacket here http://www.outdoorsmagic.com/forum/gear ... 51829.html
Apparently the jacket is a climber's fit - a short cut in length, whereas we cyclists benefit from the back being a bit longer.

I thought when I looked at this jacket that the back was longer than the front by a few inches, which I thought would be excellent for cycling, and it can be quite irritating having a jacket bend on your thighs with each pedal stroke. I suppose some people sit on their coat tails when cycling, in which case a longer walking-length jacket would be better.

Sports Direct has Karrimor Event waterproof jackets for £99. They look good, but I noticed that the lips of the waterproof zips didn't meet in places. I held off buying one because I suspected that it was mutton dressed as lamb, like the rest of the stuff they make. But most Goretex jacket makers are meant to meet a W.L.Gore standard in order to be able to use the fabric. Would it be the same with Event, and have I judged the jacket harshly?

Brucey wrote:If you are measuring +/- 0.2mm the old seat pin must be very oval

That was my error guestimate. The pin is even more oval than that, at one point, we measured 35.8mm and 35.0mm at right angles to each other, but this is consistent with the pin being 35.4mm OD.

Colin's idea of cutting up the old pin is neat, but it is a bit final, so I might hold fire on that idea. I haven't got a micrometre with me at the moment, so I don't know how thick the wall is.
Are plastic shims able to do the job? Most shims seem to be metal. Is it just that people aren't comfortable with the idea of plastic holding up their weight?

Brucey wrote:Are you sure your friend measured the correct thing?
cheers

It's definitely over 35mm. I measured it myself using a strip of paper wrapped around the pin, so that the two edges just butted up, then divided the length by pi, and came to 35.4 +/- 0.2mm, then my friend used Mitutoyo digital calipers, which aren't cheap, and obtained readings that were mostly 35.3--35.4mm. I didn't take him the bike, just the pin, and watched him measure it, so he couldn't have measured the seat tube OD by mistake.

I've had a friend apply his digital calipers to my seatpin and, on average it seems to be 35.4mm OD, although it is a bit ovalized in places, eek!

I've got two solutions:
Buy a 34.9mm seatpin, but I would then need a 0.2-0.3mm shim. Is there anything lying around a typical house that would do that?
Commercial seat tube shims don't seem to come that thin.

Alternatively, I could buy a 31.8mm seatpin (3.6mm narrower), and try to use a shim made for 27.2 to 30.8mm conversion (1.8mm thick). There would be a 15mm wide gap where there wasn't any shim, would that cause problems? And the shim might crease rather than spring open?
I've seen plastic shims; do they do the job better or worse? They seem to be a bit deeper.

Given the ability of a beautiful woman to grab my attention to the point of feeling giddy, even when initially glimpsed out of the corner of my eye, and without her wearing hi-viz or a flashing lamp, perhaps cycle tops should have a pretty face on the back of them? Is this why cyclists with mirrors have fewer accidents? Because motorists can see the face? Do ugly cyclists have more accidents? Over to you...