Engineer's Certificate

[Jim Allen]

Well it's been driven on the road on the way to get NSW registration blue slip and engineer's certificate . Felt really good so looking forward to some proper driving soon.a

As I have fitted HiSpec 4 pot callipers and matching discs the engineer needs to sign off on these as well as the rack conversion.

I have retained, at this stage the original Lockheed master cylinder and 10 inch rear brakes without any proportioning valve or check valve. The rears have just been skimmed and new shoes and liners fitted so no where bedded in. He and I are not sure if after bedding in any valves or what ever will be needed.

He says the brake modifications mean fairly extensive brake testing is required which he will need to test on a private road with some preliminary testing on a plate test machine also required. He notes that a preliminary test indicated that front to rear brake balance will require adjustment ahead of this test.He has asked if I am are able to source suitable testing for an identically modified vehicle as we may be able to use these figures.

So does any one have some test figures if not on identical callipers and discs but at least on some other 4 pot conversions that have needed an engineer's certificate. That way I'll have some figures to discuss with him.

Also any advice eg should I just get a proportioning valve fitted or smaller rear slave cylinders before I go to the expense of the road test testing to set them up.

Cheers

Jim

[john.r.davies]

Jim,

Different car, different application and no figures, but ...

 

I race a Vitesse, with a TR6 engine, which I why I hang around this street corner.

The Vitesse, like all the small chassis Triumphs, suffers from poor design of the halfshafts and rear wheel bearings, both of which I have had break up/down/off on me.

So I replaced the rear uprights with those from an MGF, with LoBro joints and Volvo half shafts.

As the MGF uprights came with their own disc brakes, I used them, rather than stick with the old drums.

This followed, a long time after, replacing the front calipers with four-pots. Which going a long way around, brings me to the relevant bit.

I didn't fit a brake proportioning valve to the rear, even though I expected the balance to be disturbed, and Lo!

It wasn't disturbed at all!

 

Which shows, I think, that by themselves 4-pots don't increase braking ability. I'm happy that, with vented front discs, they have abolished brake fade.

 

I'm surprised that the engineer wants comparative data. . Any MoT station in the UK has a 'rolling road' type brake tester that can measure the braking ability at front and rear. A road test is good practice, but has to be subjective, and may not represent how the car will be braked in use. Have you, or your engineer, seen this: http://stoptech.com/technical-support/technical-white-papers/white-paper---brake-bias-and-performance-why-brake-balance-matters

 

Would you tell us something, please, about this "NSW registration blue slip and engineer's certificate"? Is this required because you have modified the car? Or merely rebuilt it, perhaps from parts? In the UK, we just have the annual MoT test of road-worthiness, but a 'kit car' or one built from the parts of other cars, needs a far more detailed and stringent Individual Vehicle Approval test https://www.gov.uk/vehicle-approval/individual-vehicle-approval.

 

JOhn

Edited May 25, 2017 by john.r.davies

[Jim Allen]

Hi John,

Thank you for your reply and the link to the article. I composed a long reply last night and then lost it before posting so retired overnight to lick my wounds.

So again NSW Registration is annual and needs a "pink slip" issued by an authored inspection station. Not rigorous in any way and certainly not a "road worthy certificate"

If registration lapses then an authorised inspection station needs to do a much more thorough inspection before issuing a "blue slip"

If a car has been modified then a certificate issued by an authorised engineer that certifies to the safety aspects of the modifications needed before a "blue slip" can be issued.

I don't believe we have anything as rigorous as your very thorough annual MOT test.

I'm not quite sure what data the engineer wants. Perhaps just stopping distances from certain speeds so he can look for front/rear bias when testing. In which case my manual says 30 feet at from 30 mph.

Cheers

Jim

[john.r.davies]

stopping distances are a function of tyre and road surface friction.

But if they are significantly less than these Highway Code (I'm sure you have a local equivalent) distances, then the brakes are faulty.

 

 

But "30ft at 30MPH"? You have some super-brakes!

 

JOhn

[oldtuckunder]

Don't forget to bed the new pads and discs in properly, otherwise the front braking efficiency may be way down.

 

Alternatively if he says the front efficiency is too high (unlikely as you may well find its less than the two pot was) take it away and give the front discs a good clean, don't rebed in the pads, and take it back and say sorted :-)

 

The Garages in NSW really don't have roller brake testers?

 

Alan

[Jim Allen]

stopping distances are a function of tyre and road surface friction.

But if they are significantly less than these Highway Code (I'm sure you have a local equivalent) distances, then the brakes are faulty.

 

stopping distances.jpg

 

But "30ft at 30MPH"? You have some super-brakes!

 

JOhn

Hi John,

General Data page 3 of my Standard Motor Co Ltd "Service Instruction Manual" that I have owned for many, many years.

General Data for Track Dimensions.pdf

[Alec Pringle]

That was a singularly ambitious claim by Standard Triumph in the 1950s . . . . .

 

The contemporary UK brake testing standard was that of Ferodo, whose theoretical limit for 4-wheel brakes, at 100% efficiency, suggested a braking distance of 52ft from 30mph . . . . . 22ft of which was covered in the 0.5sec reaction or thinking time, and 30ft represented the actual braking distance.

 

I'm not convinced that the TR2 Lockheed or TR3 Girling systems reached the 1950s theoretical limit of braking ability.

 

As far as I'm aware, claims about braking distances ceased with the Leyland takeover.

 

Cheers

 

Alec

[Alec Pringle]

Just checked the Standard 8/10 Workshop Manual, and even more remarkably the small cars too are supposedly capable of stopping from 30mph in just 30ft . . . . . which given their modest 8" drums all round, to stop 3/4 ton kerb weight, seems like wishful thinking of the first water to me.

 

Cheers,

 

Alec

[PhilCollins]

Alec is right- 30ft stopping distance equates to almost exactly 1 "g" deceleration- not many 50s cars and tyres could do that. The standard for roadworthiness used to be at least 0.5 g on the foot brake and 0.25 g on the emergency brake, with extra concessions for vehicles with dual circuit brakes.

 

There may be a simpler way to get your engineer off the hook. If you can find a dry, empty bit of road (and surely Oz must have plenty) do a series of emergency stops. Start at 15 mph so there isn't any real hazard and work up to at least 30 mph. The skid marks will tell you whether you can lock the wheels and also which axle locks first. Conventionally for good stability the fronts should lock first. The overall objective is clear- to be able to stop in the specified distance and to remain stable under braking. A basic practical test beats any amount of theory.

 

At 30 mph a steady 0.5 g means a stopping distance of 60ft and 0.25 g means 120ft. [The formula is- stopping distance (ft) equals the square of the initial speed (in ft/sec) divided by twice the deceleration in ft/secsquared.. One "g" is 32.2 ft/secsquared and 30 mph is 44ft/sec] If the front axle can achieve wheel lock on modern tyres it is probably meeting 1 "g" deceleration. If the rear axle is over braked the car will be directionally unstable. The rear braking efficiency can be checked by measuring a stop using hand brake only.

 

If you can't lock the wheels you might wish to dig deeper.

 

Good luck,

 

Phil

 

 

 

The alternatives require specialist equipment, like the rolling road type of brake tester used in the UK.