AdrianH
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| posted on 8/11/09 at 04:46 PM |
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Any simple ideas for a foot pressure guage?
Not thinking of a tyre pressure pump here but what would let me know how much pressure I am putting on the brake pedal.
Need something with an easy to read scale so I can repeat the process several times. Have not found any scales that are small enough with a remote
panel. Thinking of using a type of bellows with an air pressure gauge with the bellows surrounded by a coil spring.
Why, in case you ask is to prove brakes for the IVA test, the brake distribution test.
Adrian
[Edited on 8-11-09 by AdrianH]
Why do I have to make the tools to finish the job? More time then money.
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zilspeed
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| posted on 8/11/09 at 04:48 PM |
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I thought VOSA had equipment specifically for measuring that and that they used it as part of the test ?
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Dangle_kt
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| posted on 8/11/09 at 04:57 PM |
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I can only guess Zil that due to the new high price of the test and the retest, that people are trying to pass first time?
you could do a similar thing to the air bellows one, but with coloured water with a long tube, with marks on it - as long as you insert some sort of
spring to resist the pressure of your foot.
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tegwin
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| posted on 8/11/09 at 04:58 PM |
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I would make a rig using a spring balance so you push down on the spring balance and it "pulls" the pedal down... and then measure the
maximum deflection on the spring balance....
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Would the last person who leaves the country please switch off the lights and close the door!
www.verticalhorizonsmedia.tv
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MikeR
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| posted on 8/11/09 at 05:00 PM |
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i think he wants to test before he does IVA
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austin man
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| posted on 8/11/09 at 05:21 PM |
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attach the weight scale a fisherman uses or the one you can buy for wighing your suitcases rig it to the pedal an steering wheel then you can view the
scale
Life is like a bowl of fruit, funny how all the weird looking ones are left alone
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AdrianH
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| posted on 8/11/09 at 05:22 PM |
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MikeR you are correct.
I failed the IVA and this was a main item with the backs being as good as the front. At weekend a friend got the car on to an MOT brake tester but it
only showed at what point the brakes locks.
So what I need to do is work out five points before lock and determine front brake effort and the same 5 points and rear brake effort.
I think I have done enough now to ensure pass but as well as the cost there is the time off work.
I would still have to find a seal bellows small enough to go within a spring.
Adrian
Why do I have to make the tools to finish the job? More time then money.
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zilspeed
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| posted on 8/11/09 at 05:25 PM |
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quote:
Originally posted by Dangle_kt
I can only guess Zil that due to the new high price of the test and the retest, that people are trying to pass first time?
you could do a similar thing to the air bellows one, but with coloured water with a long tube, with marks on it - as long as you insert some sort of
spring to resist the pressure of your foot.
Fair enough, hadn't thought of that.
In that case, a set of electronics scales and a stick would measure pressure at the pedal whilst the car is static.
Surely a friendly MOT tester could let you use their rollers whilst you press the stick with a set of scales, then record the pressure exerted and the
braking force acheived. That's got to cost no more than a donation to their tea fund.
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Dangle_kt
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| posted on 8/11/09 at 05:42 PM |
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quote:
Originally posted by zilspeed
quote:
Originally posted by Dangle_kt
I can only guess Zil that due to the new high price of the test and the retest, that people are trying to pass first time?
you could do a similar thing to the air bellows one, but with coloured water with a long tube, with marks on it - as long as you insert some sort of
spring to resist the pressure of your foot.
Fair enough, hadn't thought of that.
In that case, a set of electronics scales and a stick would measure pressure at the pedal whilst the car is static.
Surely a friendly MOT tester could let you use their rollers whilst you press the stick with a set of scales, then record the pressure exerted and the
braking force acheived. That's got to cost no more than a donation to their tea fund.
I like that idea a lot - obvious really, but I could never have come up with it!
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AdrianH
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| posted on 8/11/09 at 06:38 PM |
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Does anyone know what a typical pedal pressure could be for a 7 style car? at 150Kg force per front wheel mine where locking, got to guess at 50 kg
max?
Adrian
Why do I have to make the tools to finish the job? More time then money.
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oldtimer
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| posted on 8/11/09 at 07:38 PM |
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Could you not use this?
http://www.autoanything.com/brakes/61A3154A0A0.aspx
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AdrianH
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| posted on 8/11/09 at 08:13 PM |
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I assume that will measure the fluid pressure in the lines, which would mean re bleeding the system to put it in and take it out.
I like the idea of the stick and scales that is very low-cost, but how easy to operate and work the brake rollers at the same time I do not know.
That after watching there operation on Saturday.
I have an idea that may include a bike clutch slave cylinder hose and a pressure gauge.
Just need to know what pressure you can apply, guess that will be trial and error.
Adrian
[Edited on 8-11-09 by AdrianH]
Why do I have to make the tools to finish the job? More time then money.
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oldtimer
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| posted on 9/11/09 at 07:44 AM |
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I don't think so, looks like a 'quick-release' type system to me. You may have to fix upa a tee where the bleed exit is, attach the
female fittings ang bleed nipples back on. Opperate the system moving the gauge around, set your bias valve, remove tee, rebleed and done. Just my
thoughts, I've not done it....
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rusty nuts
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| posted on 9/11/09 at 08:12 PM |
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pressure gauge connected to a caliper where a bleed nipple fits should be an easy way to do it. VW used a similar workshop tool to set the brake
balance on the LT van range
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britishtrident
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| posted on 9/11/09 at 10:18 PM |
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KISS principle, don't approach a problem by using the most complicated route possible, istr your brake test results weren't far out
just fit smaller rear wheel cylinders, job done.
[Edited on 9/11/09 by britishtrident]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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AdrianH
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| posted on 11/11/09 at 10:59 PM |
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I've done the brake cylinders already, but also enjoy testing and proving what I do matches what I think it should, if you understand what I am
trying to say.
 
Pedaltest
My pedal tester first stage tonight.
One last change to side repeaters then going for retest. I can not book retest yet as can not get time off work at present so need something to
occupy myself!
Adrian
Why do I have to make the tools to finish the job? More time then money.
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Liam
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| posted on 11/11/09 at 11:19 PM |
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If you just want to measure typical human being brake pedal effort, just do what I did and sit yourself in a driving position with your back against
an imovable object. Then position bathroom scales between your brake foot and another imovable object, push, and read. Voila - your brake force
measurement (in kg. x10 for N). If you want to know pressure in the brake lines, that's just a function of your foot force, the pedal ratio,
and master cylinder piston size. If you measure pressure generated in some bellows contraption or some other non-representative equipment, it's
a meaningless figure, unless you then work out your foot force from the characteristics of your equipment - but why do that if you can directly
measure your foot force with bathroom scales?
Liam
[Edited on 11/11/09 by Liam]
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AdrianH
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| posted on 12/11/09 at 12:09 AM |
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Not really trying to measure how much foot pressure I can provide, guess I could go to 150 Kg easily, because you can put a lot more force on the
pedal then you need to lock the wheels.
Sorry if this next bit is saying how to suck eggs!
My car seems typical at 570'ish Kg weight. On the rolling road brake test the front would lock around 150 Kg effort tyre to roller and 130 Kg
on the back. Just because the car is light.
What the IVA tester did was to fit a device to the sole of his foot. Apply pressure to the brake pedal and record the point at which the front wheels
locked, say at 42 kg force on the pedal.
He then tested the brake effort at the rollers at 5 points from a low pressure to just under the 42 Kg, say at 8, 16, 24, 32 and 40 Kg. For each of
the 5 points he recorded the figures for the front axle.
Then on to the rear axle and at the same 5 points repeated the test for the back wheels. He then fed the figures into a computer programme and worked
out if the brake balance was less then the weight distribution for all 5 points.
I am just trying to get a DIY method for applying the same 5 pressures to the pedal to test the front brakes and for the rear brakes at a standard MOT
garage.
It makes no difference if the scale is not calibrated providing it is repeatable. At present 2 on the scale is only 23 Kg or 230 Newton' ish.
I can add a spring I think to give it a higher pressure for full scale reading. But it is guess work what range I need to give it.
Adrian
[Edited on 12-11-09 by AdrianH]
Why do I have to make the tools to finish the job? More time then money.
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Liam
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| posted on 12/11/09 at 12:51 AM |
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Ah - I understand exactly what you're trying to do know! Your naughty interchanging of 'force' and 'pressure' had me
slightly confused.
I'm sure with some choice bits of wood you could sandwich some bathroom scales between your foot and brake pedal, couldn't you? But
failing that your proposed device looks good. Ideally you'd then calibrate that device with known weights to relate the guage reading to
applied force. That would be more reliable than trusting the guage to be accurate and doing a calculation using the piston area to get the applied
force.
Liam
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Liam
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| posted on 12/11/09 at 01:03 AM |
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Ah just read your edit. OK well dont worry about calibration if you only need repeatability. Bit hard to see on the picture - but you're
saying you're going to full scale (2 bar) at only 23kg? Simple solution then - bigger piston or higher range pressure gauge. You can get a
0-10 bar gauge from RS for about 17 quid. Should do the trick if I understand your problem correctly!
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AdrianH
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| posted on 12/11/09 at 07:35 AM |
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Cheers Liam. I will look at the gauges, the slave was £13 from a bike breakers and was convinced I had an old oil pressure gauge somewhere in the
garage, that should go more then high enough.
It's a bit of fun really getting ideas to work.
Why do I have to make the tools to finish the job? More time then money.
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