FAO Yeehaa
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How is temperature to be measured?
(serious question!)How would I write my own epitaph? With a crayon - I'm not allowed anything I can sharpen to a sustainable point.
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Steelie says he has access to a non-contact thermometer. It's basically a calibrated infra-red camera, which measures the amount of infra-red light (heat) given off.Clank wrote:How is temperature to be measured?
(serious question!)
The advantage of these types over a thermocouple (general) style thermometer, is that you don't have to wait for any part of the thermometer to settle at a temperature, so you can get accurate readings immediately.
EDIT: Beat me to it - but at least there's some more info there about why that kind of instrument is better in this case.
And yeah, 22 stone should be fine.
So there's you at 22 stone, me at about 15 and a half, maybe we should get a whippet involved too!
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Has it been calibrated to work on uncoated steel?
Many aren't, and consequently can give an abolsute BS reading. We have some like that in work, and with the amount of welding we do, it's a bit of a t**t. Instead, they work great on painted surfaces and polymers (tyres, s**t like that).How would I write my own epitaph? With a crayon - I'm not allowed anything I can sharpen to a sustainable point.
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Clank wrote:Has it been calibrated to work on uncoated steel?
Many aren't, and consequently can give an abolsute BS reading. We have some like that in work, and with the amount of welding we do, it's a bit of a t**t. Instead, they work great on painted surfaces and polymers (tyres, s**t like that).
I shall make sure it is when I send it off. All this is just in the pipe line, but im sure we can make an uber geeky dark blue anorak review of it all!! LOL
My first priority it build my bike up, and get a bit of fitness, cos I havent got any at all. But im sure well have this done before summer is over, cos we'll need a dry day to hammer that front brake to get some heat in the old girl!!!0 -
The chart on the link above show the colours the steel turns as it heats, not the blue /purple colours that are still present after they have cooled down,typical of exhausts, brake discs , flywheels etc
The bedding in instructions on super star pads tells you to do 10 hard brake applications from speed to stand still,and to check the disc is hot enough by flicking some water on and seeing that is boiled away(prob not the best thing to do to a +100c disc) So after some heavy braking or dragging on long descent i'd imagine you could double the temperature,having said that the air speed/cooling will be greater.
edit, b011ox, did get to 2nd page0 -
I'm not sure how all of them work, but I can't see how an infra-red measurer would differentiate between different materials.Clank wrote:Has it been calibrated to work on uncoated steel?
Many aren't, and consequently can give an abolsute BS reading. We have some like that in work, and with the amount of welding we do, it's a bit of a t**t. Instead, they work great on painted surfaces and polymers (tyres, s**t like that).
Maybe if the I.R. filter was actually letting in some visible light, or wasn't a strong enough bandpass filter. But the concept behind them is scientifically sound, regardless of material.0 -
top work if you can get some valuable results guys0
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I think that a lot of the way that stuff looks in thermography, and maybe IR (although I'm not totally sure), is due a property called emissivity.
http://en.wikipedia.org/wiki/Emissivity
Basically as long as the disc is measured at the same distance away from the sensor, and the target is made of the same thing, then the results should be roughly comparable. Distance might be a bit irrelevant in this case, as my experience of this stuff comes from aerial survey where the distances involved are obviously a bit larger.
It'd be really interesting to see how quickly the disc heats up under braking and cools down again over the course of a run, and see to what extent different sized riders who are travelling at similar speeds influences this. In order to do that you'd need to mount the camera somehow though, and not crash the bike. It's actually a really difficult thing to measure, and there are a lot of variables that you'd struggle to control. Are you just proposing to measure directly after a run?0 -
Dunno, really. The original debate was about how hot they got under very hard use, so maybe just measure once immediately after stopping, then again every minute or so just for extra geeky insight.EH_Rob wrote:Are you just proposing to measure directly after a run?
I think the deal is, if the brakes are under 200C, Steelie buys me a pint. If the brakes get over 200C, I buy Steelie a pint.
And, if some brakes stay under, and some go over, then we buy each other a pint 0 -
YeehaaMcgee wrote:I'm not sure how all of them work, but I can't see how an infra-red measurer would differentiate between different materials.
Maybe if the I.R. filter was actually letting in some visible light, or wasn't a strong enough bandpass filter. But the concept behind them is scientifically sound, regardless of material.
Different material radiate, absorb and reflect IR energy in very different ways ('transmissive welding' exploits this characteristic in a really cool way). So yes, the science of them working is very sound. But the same science can trip 'em up - hence my asking. The usual fix is a different bandpass filter, as it happens!
It's the reason why for most of our tests in work we use thermocouples (unless we're dealing with really hot s**t).
Not trying to diss your tests - just wanting to make sure the result is pukka - I'm fascianted about how hot these brakes can get myself.How would I write my own epitaph? With a crayon - I'm not allowed anything I can sharpen to a sustainable point.
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This is what we need to work out, how we are going to measure, a set speed to run at (the bike are gonna need speedos), a braking distance test, and anything else we can come up with, and then make some pretty pie charts or graphs so the simpletons can understand0
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If we do use the hill by the pub, then I'm pretty sure than any brake will be nearing it's limit, so for a simple "do they or don't they" just stopping the bike (if you can!) should be enough.
However, I'm definitely not opposed to a more thorough, or broad analysis.0 -
aye sounds like we will both have the jedi blue anoraks on!! LOL Where is this hill anyhoo, can you gimme a google map link so I can have a look and I probably pop over next week have a look on the nail!0
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http://g.co/maps/4vqch
It's the hill to the immediate south of the Halfway House and it's car park, that goes up through the trees.0 -
Didnt know it were that far into Welshland!! LOL, But yep looks ideal, slow down or its gonna hurt!!0
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I was thinking initially winter hill just outside Bolton going to Rivvy barn. Thats one steep mofo or maybe the cat n fiddle as there is a nice steep decent that goes round a chapel coming back down the congleton side its about a mile ling and there are 4 big brake moments on it. But closer the time we can make a decision mate0
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Uncompromising extremist0
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this is more relevant to the discussion tho
http://www.youtube.com/watch?v=qXg4gvPrCFY&feature=related0 -
Here's an idea, however it would only measure the temp of the calliper or brake pad
Mountable temp gauge, this comes form the world of RC but it's probably do the job if you were to mount it to the fork leg/rear swingarm and get the sensor as close to the brake pads as possible
Having used these when racing RC nitro cars, I know they log the highest temperature recorded too
Not cheap at £35, but they are small and light0 -
Well, the discussion started with questioning how hot a brake disc gets, if I recall correctly.0
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Just looked at this - the geeky side of me finds it quite interesting :oops:
but what the fark is a sensible thread like this doing in the Crudcatcher? "I spent most of my money on birds, booze and fast cars: the rest of it I just squandered." [George Best]0 -
Because it will all fark up and turn into a bundle of sh1t sooner or later.I don't do smileys.
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As fun as the 'let's ride down a hill near a pub' method sounds, I would say there are far too many variables involved to get a truly accurate set of results, although it would be very interesting to test the performance of a load of brakes in 'real world conditions' (i.e. different rider weights, set ups, tyres, size of bolloxs...!)
If you just want to see how hot you can make a brake get, I'd suggest a rig where the rotor is attached to a motor, and applying the brake fully whilst progressively increasing the speed of the rotor until something fails.
On a side note, my Uncle flies microlights, and they use mountain bike brakes (some model of Magura I think).
I have also heard a story from a mechanic of a brake pad becoming welded to the brake piston due to the brake being used without any braking material left on the pad...Only those who will risk going too far can possibly find out how far one can go - T.S. Eliot0 -
Err, not really, no. All they're doing is seeing if brakes will reach 200 degrees celcius, how do tyres, set ups and rider weight affect that? If it reaches 200 degrees it reaches 200 degrees, if it doesn't then it's probably hotter than most riders can get a brake to reach.Ghostt wrote:As fun as the 'let's ride down a hill near a pub' method sounds, I would say there are far too many variables involved to get a truly accurate set of results, although it would be very interesting to test the performance of a load of brakes in 'real world conditions' (i.e. different rider weights, set ups, tyres, size of bolloxs...!)0 -
Meh, motor sounds boring. And the problem with finding somewhere suitable to ride a brake to it's limits is that, well, there's not a lot of places that you can do it.Ghostt wrote:As fun as the 'let's ride down a hill near a pub' method sounds, I would say there are far too many variables involved to get a truly accurate set of results, although it would be very interesting to test the performance of a load of brakes in 'real world conditions' (i.e. different rider weights, set ups, tyres, size of bolloxs...!)
If you just want to see how hot you can make a brake get, I'd suggest a rig where the rotor is attached to a motor, and applying the brake fully whilst progressively increasing the speed of the rotor until something fails.0 -
A grippier tyre will allow you to brake harder without breaking traction.bennett_346 wrote:
Err, not really, no. All they're doing is seeing if brakes will reach 200 degrees celcius, how do tyres, set ups and rider weight affect that? If it reaches 200 degrees it reaches 200 degrees, if it doesn't then it's probably hotter than most riders can get a brake to reach.Ghostt wrote:As fun as the 'let's ride down a hill near a pub' method sounds, I would say there are far too many variables involved to get a truly accurate set of results, although it would be very interesting to test the performance of a load of brakes in 'real world conditions' (i.e. different rider weights, set ups, tyres, size of bolloxs...!)
Setup? Er, no idea what he's on about, to be honest.
Rider weight will make a HUGE difference to the brake temperature, since the heavier the rider the more kinetic energy the brake needs to disperse. In a car, the driver weight only plays a tiny part, but on an MTB, the rider is the main component of the total vehicle weight.0 -
Yeah, but you'll still get valid results whatever weight you use, and you can always draw conclusions from it. In this scenario if you find that, for example, someone of above average weight cannot get them to reach 200 degrees, then you can fairly safely assume that mtb brakes probably wouldn't reach 200c easily. Coversely, if you get them way above 200c easily then a lighter rider would likely still get them to 200 degrees with a bit more effort. Also, it would be pretty easy to test the effects of time on heat, because you can find a long shallow descent and a short steep descent and compare. Yeah, tyres will have an effect on braking performance, but i'd wager that it's minimal. You can still play with pressures remember.YeehaaMcgee wrote:
A grippier tyre will allow you to brake harder without breaking traction.bennett_346 wrote:
Err, not really, no. All they're doing is seeing if brakes will reach 200 degrees celcius, how do tyres, set ups and rider weight affect that? If it reaches 200 degrees it reaches 200 degrees, if it doesn't then it's probably hotter than most riders can get a brake to reach.Ghostt wrote:As fun as the 'let's ride down a hill near a pub' method sounds, I would say there are far too many variables involved to get a truly accurate set of results, although it would be very interesting to test the performance of a load of brakes in 'real world conditions' (i.e. different rider weights, set ups, tyres, size of bolloxs...!)
Setup? Er, no idea what he's on about, to be honest.
Rider weight will make a HUGE difference to the brake temperature, since the heavier the rider the more kinetic energy the brake needs to disperse. In a car, the driver weight only plays a tiny part, but on an MTB, the rider is the main component of the total vehicle weight.
I do understand what you're saying, but short of a full scientific investigation i think you'll still get valid enough results for the scope of the test that you're after.
I've done tests on braking distance in the real world before and made up graphs to go with the results, you'd be surprised how little of a percentage effect those listed variables make.
All in all good luck, and hope the experiment goes well lads.0
