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]

I thought VOSA had equipment specifically for measuring that and that they used it as part of the test ?

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.

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....

i think he wants to test before he does IVA

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

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

quote:

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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.

---

quote:

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Originally posted by zilspeed

quote:

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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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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

Could you not use this?

http://www.autoanything.com/brakes/61A3154A0A0.aspx

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]

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....

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

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'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

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]

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]

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

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!

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.