Search found 192 matches

by Mr Evil
20 Jun 2021, 11:21pm
Forum: Bikes & Bits – Technical section
Topic: Disc Brake Thermal Imaging
Replies: 2
Views: 517

Disc Brake Thermal Imaging

Today I attached an infra-red camera to my bike, pointed it at my front brake, then rode down a hill, deliberately dragging the brake the whole way.

I can't see a way to embed a video, so here's a link. https://mrevil.asvachin.com/cycling/bra ... 13_A-1.m4v It's hosted over my home internet connection, so it might be slow if too many people view it at once.

Notable things include:
  • The camera unfortunately doesn't embed the scale in the video, and it auto-ranges to the highest and lowest temps in each frame, so you can't tell what the absolute temperature is.
  • Occasional pauses in the video are where the camera recalibrates itself.
  • Different materials radiate heat differently, so you can't directly compare the apparent temperature of different parts of the bike.
  • At the start, I had been standing at the top of the hill for a minute, which was long enough for one side of the tyre to absorb heat from the road. This is why one side appears slightly orange as I start the descent.
  • I start dragging the brake at around 0m40s.
  • By about 1m00s the rotor is much hotter than anything else in the picture.
  • I come to a complete halt right at the end of the video.
In case anyone can't see it, here are pictures from the start and end:
Image

Image

And here's a second video from a short while later showing much quicker heating from hard braking to stop at a junction. At the start, you can see that the caliper has warmed up a bit compared to the first video: https://mrevil.asvachin.com/cycling/bra ... 13_A-2.m4v

The brake caliper is a Hope RX4, and the rotor is a Shimano RT81, which is one of the ones with an aluminium core.
by Mr Evil
29 Jul 2020, 11:10am
Forum: Does anyone know … ?
Topic: Repurposing old bike parts
Replies: 21
Views: 2155

Re: Repurposing old bike parts

Cyckelgalen wrote:Rather than bike parts, I'd like to repurpose a whole bike to power a manual water pump of some sort to water my garden from a nearby pond. Last time I looked into it I didn't find any suitable affordable pump, only a rather costly commercially produced pump that had been developed as an aid to subsistence agriculture in the third world.
Any better ideas?

How about attaching the bike to a generator, and using an electric pump? There would be a loss of efficiency in the mechanical->electric->mechanical conversion, but you would gain a wider choice of pumps.
by Mr Evil
28 Jul 2020, 10:07am
Forum: Does anyone know … ?
Topic: Repurposing old bike parts
Replies: 21
Views: 2155

Re: Repurposing old bike parts

gregoryoftours wrote:Is that a Kooka crank?

No, it's an ax-lightness crank. Too new to use for this really, but it's the only one I had spare.
by Mr Evil
25 Jan 2020, 5:23pm
Forum: Does anyone know … ?
Topic: Titanium seatpost
Replies: 27
Views: 2415

Re: Titanium seatpost

robgul wrote:...it's not going to rust or corrode in any way...

The seatpost itself won't, but some titanium frames have aluminium inserts in the seat tube. The presence of a titanium seatpost against the aluminium in an area that may get quite wet can result in the aluminium corroding.
by Mr Evil
23 Jan 2020, 6:18pm
Forum: Does anyone know … ?
Topic: ...why so many bikes are such boring drab colours these days?
Replies: 80
Views: 3661

Re: ...why so many bikes are such boring drab colours these days?

It's disappointing that technology has improved so much that customizing products for each user should be easier and cheaper than ever, and yet the improvements are instead put into mass production of a minimum of variants, and the general public seem quite happy with it like that.

Personally I've had bikes in all manner of colours, from plain to garish, and got around the lack of choice in car colours by respraying mine. My current preferred style is mostly plain, with bright colours used for highlights, thusly:
Image
Whatever your favourite colour, it's in there somewhere.
by Mr Evil
20 Jan 2020, 6:35pm
Forum: Bikes & Bits – Technical section
Topic: What is a Gravel Bike?
Replies: 280
Views: 10329

Re: What is a Gravel Bike?

slowster wrote:74 and 73.5 degree seat angles are pretty much the norm for gravel bikes. If it's the case that 'you can find whatever you want', please give me some examples (plural) of gravel bikes in a 'medium' size with a 72 degree seat angle.

I'm not going to go trawling through the internet to find them for you , but since I was looking at gravel frames recently, here's one I had in my notes: https://www.aliexpress.com/item/33027472215.html

The one I ended up buying has a 72.5° seat tube, which seemed a popular angle. Yes, that means, horror of horrors, than I own what might called a "gravel" bike. You could call it a tourer instead if that would help reduce your blood pressure, but I don't tour on it. When called a gravel bike, I'm confident that it ticks all the boxes for things that the older crowd on here despise.

slowster wrote:And there's the rub: someone who buys a gravel bike because (to begin with) they are just going out for short one or two hour blasts on tracks and bridleways is potentially going to be deterred from going further, if they find the bike unsuitable for longer periods in the saddle. Someone who buys a touring bike will have a bike suitable for short rides and long rides, and for carrying as much or as little with them as they want.

You sound like you think that people be going on weeks-long tours is the end goal that everyone should strive for. What if someone doesn't do that, and a gravel bike, or any other type of bike for that matter, actually suits them fine?

horizon wrote:... I don't think we have such roads in the UK so of course we find gravel bikes a bit mystifying. I would also just use an old-fashioned MTB.

I don't think that's the issue. Most of the UK is bereft of mountains too, yet no one finds the name "MTB" to be mystifying.

I'm not going to read through all the other posts here now, as it's turned into foaming-at-the-mouth walls-of-text. Who could have though that the mere existence of a name could evoke such passion; they're just bikes, like any other.
by Mr Evil
18 Jan 2020, 6:18pm
Forum: Bikes & Bits – Technical section
Topic: What is a Gravel Bike?
Replies: 280
Views: 10329

Re: What is a Gravel Bike?

slowster wrote:
gregoryoftours wrote:More capable off-road than a touring bike, less designed for full load bearing

So that would be less capable off-road than a touring bike then.

Shorter chainstays, steeper seat angles and shorter wheelbases will contribute to a livelier, more responsive ride. Except that the further you ride, especially off-road, the more undesirable those qualities become, i.e. even less capable off-road than a touring bike.

Wheelbase and chainstay length really don't make much difference to handling. Seat tube angles vary, and aren't necessarily steeper - you can find whatever you want. On the other hand, gravel bikes tend to have room for wider, potentially knobby tyres. But yes, touring bikes are designed for very long distances, while gravel bikes are not. Which is better depends on what you are going to use it for.
by Mr Evil
18 Jan 2020, 5:23pm
Forum: Bikes & Bits – Technical section
Topic: What is a Gravel Bike?
Replies: 280
Views: 10329

Re: What is a Gravel Bike?

They can also be compared to touring bikes, as they are built stronger, and more likely to be designed to take mudguards and racks than standard road bikes, but they usually have shorter chainstays as they aren't designed to carry as much.
by Mr Evil
13 Jan 2020, 5:18pm
Forum: Does anyone know … ?
Topic: Printed lugs etc
Replies: 5
Views: 574

Re: Printed lugs etc

pwa wrote:...The only 3D printing I've seen has involved some plasticy material that probably wouldn't be up to much.

If KM2 was really referring to 3D printing, then it's probably selective laser melting, which can be done with any of the metals used for bicycle parts.
by Mr Evil
30 Dec 2019, 6:47pm
Forum: Bikes & Bits – Technical section
Topic: Wooden Mudguards .... Aye or Nay?
Replies: 17
Views: 1439

Re: Wooden Mudguards .... Aye or Nay?

Mike Sales wrote:I note that the Squaretree Woodguards have their stays outside, in the continental way. Seems a good idea. Is it?

I don't think I can say that it's better or worse. In combination with the thickness of the wooden mudguards, it let me countersink the fixings, so the inside surface of the mudguards are completely free of protrusions.
by Mr Evil
30 Dec 2019, 2:56pm
Forum: Bikes & Bits – Technical section
Topic: Wooden Mudguards .... Aye or Nay?
Replies: 17
Views: 1439

Re: Wooden Mudguards .... Aye or Nay?

I can offer an opinion, as I have been using a pair of wooden mudguards for over 5 years now. They are Squaretree Woodguards*, which are flat, and consist of both wood and a thin layer of aluminium glued underneath. The attached photo is from when they were new; they are faded compared to that now, but still look good. My observations are:

  • Flat mudguards are a ltitle less effective at catching water. I'd say about 80-90% as good as ones with a compound curve.
  • Flat mudguards are less sensitive to the width of the tyre than curved ones - you can fit tyres that are too wide, and they still function more or less, since most water is flung from the centre of the tyre.
  • Flat mudguards can be cleared more easily when they clog.
  • The bond between wood and aluminium has stood up well. Even after years of water spray, they are still inseparable.
  • They absorb moisture when it's wet, and change shape slightly. They need to be mounted very securely and with sufficient clearance, otherwise this will cause them to rub.
  • The stain has faded at the ends where they are sprayed the most. Also - don't scrub them too hard when washing them, as that washes the stain out too. The one in your photo looks varnished, which will probably be better in this regard.
  • They attract an unexpected amount of attention from people wondering what they are made of.
  • No problems with fatigue so far, which is a problem that plagues flat aluminium mudguards.

Related to your cracking problem, I actually cracked my rear mudguard when it got caught on a fence as I was trying to squeeze through a small gap. Right where the rearmost stay attaches. I fixed it by epoxying a sheet of carbon fibre across the crack and it has been fine ever since, even with a bolt going through the middle.

* Their website was http://www.woodguards.co.uk but it's defunct now. Not sure if that's temporary, or if they have gone out of business.
by Mr Evil
20 Dec 2019, 2:42pm
Forum: Does anyone know … ?
Topic: Repurposing old bike parts
Replies: 21
Views: 2155

Repurposing old bike parts

If you do a lot of cycling, you're bound to end up with a lot of parts that aren't suitable for reuse, but it seems wasteful to throw them away. Inner tubes are a common one. I have used a few of those for suspending hard drives, to damp their vibrations and quiet them, like this:
Image
That's not something I am able to do as much anymore, now that hard drives are becoming obsolete.

I had an aluminium frame lying around for many years that had been retired due to a crack. Recently I cut it up and turned it into wind chimes:
Image
The tubes are hung from a right crank. It's important that the holes for the string are exactly 1/4 of the way down, as the standing waves that make the tubes ring have a node at that point.

A few other things that I've done include bending spokes into hooks for clothes-hangers, and grinding a pair of titanium skewers into chopsticks (sadly they are too short to work well).

What creative ways have you come up with for finding new life for old parts?
by Mr Evil
18 Dec 2019, 5:51pm
Forum: Bikes & Bits – Technical section
Topic: CAAD 12 Durability for commuting.
Replies: 24
Views: 4522

Re: CAAD 12 Durability for commuting.

Cowsham wrote:10 Brucey -- what you say about carbon frame aluminum inserts dissolving is scary so has put me off carbon frames.

That's mainly a problem with early or poorly made carbon frames where aluminium parts are bonded directly to the carbon. Better frames will electrically insulate the aluminium, so there is much less risk of corrosion.

Cowsham wrote:8 A threaded BB if possible but not a deal breaker.

This is related to the above: I much prefer press-fit bottom brackets, especially with carbon or titanium frames, because then I can use plastic cups instead of aluminium, eliminating galvanic corrosion entirely.

I've used bikes of all four common frame materials for commuting. All of them can work fine, but my current ones are carbon and titanium, with parts carefully chosen to avoid corrosion, since they get ridden every day in the winter, covering them in salt I am too lazy to wash off, and they are left out in the rain all day.
by Mr Evil
16 Dec 2019, 5:39pm
Forum: Bikes & Bits – Technical section
Topic: Wheels - number of spokes
Replies: 31
Views: 2103

Re: Wheels - number of spokes

Brucey wrote:...So to put fashion considerations ahead of wheel strength in a touring machine is (IMHO) a pretty dumb idea. Adding four more spokes per wheel 'costs' about 30g per wheel...

You can make exactly the same argument about any chosen spoke count; going up to 40 spokes is only a small penalty, and 48 spokes only a little more. The choice of 36 spokes is based on tradition, which is just another form of fashion, and a wheel which is stronger than it will ever need to be is just as pointless as choosing a wheel is which is lighter by an amount you will never notice.
by Mr Evil
13 Dec 2019, 3:51pm
Forum: Bikes & Bits – Technical section
Topic: Frameset transplant: Spa Titanium Touring
Replies: 89
Views: 4896

Re: Frameset transplant: Spa Titanium Touring

Foghat wrote:...Rack mounts feature M6 threads, which seem far more appropriate than M5 - why don't all rack-capable frame designers specify this?..

M5 bolts are stronger than you might think. Strong enough to carry the weight of anything you might reasonably put on the back of a bike.