question Brake testing

[Iain Crosbie]

I have an MOT exempt Militant Mk 3 Recovery truck on which I wish to do a voluntary brake test.

I have access to a Tapley Meter, but having looked at some posts about these meters on here I wonder what reading I should be looking for in order to expect a pass on a brake testing roller at the MOT station.

As far as I can find out, the test requires a braking efficiency of 50% on the rollers, so the question is: does that equate to 50% on a meter? I have adjusted up the brakes and tried the meter this afternoon, but could not get a reading above 35%, although it did seem to stop OK, and of course at 21 tons it does require some stopping!

One thing the meter instructions did not make clear is whether or not you need to let the vehicle settle down to a constant speed before applying the brakes (as I did). I noticed that on initial acceleration the meter dial naturally moves in the opposite direction, so presumably if you applied the brake before it had settled back to the zero/level position you would get a wrong reading? Also, I cannot quite see why it is unimportant that the road being used is not completely flat as you are required to accurately set the meter up to a level position before the test, so surely the reading would again be inaccurate if you ended the test on a hill, either up or down?

Are there any mechanics out there who can clarify things for me, and does anyone else with a Milly remember what their brakes read on a test?

[Richard Farrant]

I have an MOT exempt Militant Mk 3 Recovery truck on which I wish to do a voluntary brake test.

Are there any mechanics out there who can clarify things for me, and does anyone else with a Milly remember what their brakes read on a test?

 

Hi Iain,

 

The Tapley will not show you any imbalances between wheels. Better if you can find a friendly truck or bus workshop with brake rollers who will test them for you, that way you will have a much better idea of how they are performing.

 

regards, Richard

[cosrec]

I have never actually used a tapley meter myself. But have been driving various vehicles when they are being used for MOT with examiner sat along side. All i can say is they have passed and i was told not to press brakes to hard when doing test. To be honest i feel i could have stopped a lot quicker than i did and i still recieved a pass. Vehicles i took on more than one occasion were Martian and Thornycroft Big Ben both had no Third diff so could not be spun on rollers. Foden Gun tractor this one the tyres were to large diameter to get grip on rollers. Hand brakes were all tested backwards and forwards on incline ramp out side test station. When doing tests had to hold steering loosely in order examiner could see if there was any inbalance on braking a second person was looking for wheels locking. Before doing test vehicles are examined at great length over pit for air leaks sluggishness air pot releasing and air pot travel. also warning lights (buzzers not needed any more) and air build up on gauges after air tanks depleated from pressing brakes. Dont know if a militant will actually be be tested over rollers but if done on tapley meter i think it should pass ok either way you have advantage as it cant be tested at full gross wieght as they have no way of loading it. In fact more i think about it i doubt it will be done with rollers.

Edited September 26, 2011 by cosrec

[Grumpy]

35% is about right for a Mk 3 recovery, you will struggle to get any where near 50% without a lot of work. It can be put on the rollers but you may have grip problems with the 1600 x 20 tyres.

[Iain Crosbie]

35% is about right for a Mk 3 recovery, you will struggle to get any where near 50% without a lot of work. It can be put on the rollers but you may have grip problems with the 1600 x 20 tyres.

So if 50% is the pass mark, does that mean I would have an automatic fail, or is there a discrepancy between the meter and the rollers which might mean 35% on the meter is 50% on the rollers?

If I'm understanding things properly, different standards would apply to a Mk 1 Militant because of age, even though the brakes are similar, i.e. only one leading shoe per wheel. Is that right?

[Grumpy]

It would probably fail, even fresh out of the factory they struggled to meet the braking standards. De-glaze the shoes and drums and let them bed in again and see what you get then. The brakes on the Mk3 Recovery are not the best, we looked at putting type 30 spring brake chambers on the back to improve things but you haven’t got room due to the ground anchor.

[Iain Crosbie]

Thanks for your input guys. Not quite sure where I go from here, but will obviously start by trying to rejuvenate the drums and shoes. From what you have all said it seems unlikely that any Milly out there would achieve a pass- or does anyone know different?

[cosrec]

I beg to differ as long as every thing is working as it should you will acheive a pass. I know a few companies who had them on police contracts and they had to go for certificates of roadworthiness (MOT under another name) Like i said they cant test it at its full loaded wieght so you have an edge to start with. Another piont are you taking it to a DOT station or somewhere say a local Council yard for test. Even the Dot station wont stop you driving it away again unless its down right dangerous and a danger on the road

Edited September 27, 2011 by cosrec

[Iain Crosbie]

I beg to differ as long as every thing is working as it should you will acheive a pass. I know a few companies who had them on police contracts and they had to go for certificates of roadworthiness (MOT under another name) Like i said they cant test it at its full loaded weight so you have an edge to start with

Sorry to be thick about this as I am no expert in this field, but could you clarify the weight issue? If I understand things correctly, the braking force as measured by the rollers or other device should amount to 50% of the vehicle weight, which I take to be 21 tons. If you are suggesting that the fully loaded weight could be more than 21 tons, then surely you would be looking for an even greater braking force to achieve the 50%? What figure would you think to be possible for the full loaded weight, and how does that come about for a vehicle not designed to be load carrying (other than the 4.5 ton suspended load)?

I would intend taking it to a friendly local commercial vehicle company who do MOTs and have a set of rollers.

Edited September 27, 2011 by Iain Crosbie
extra info

[cosrec]

When a commercial vehicle is taken to a DOT station It undergoes an MOT the vehicle is taken either fully loaded or artificial loads imposed on the vehicle by equipment in the test station. The vehicle has to meet standards at these wieghts. Recovery vehicles except those with flat backs eg transporters are exempt from MOT. Reason being they cant impose loads on them. In theory your militant wieghs what ever but it will have a designed Gross vehicle wieght this is the wieght it should be able to provide efficency at. So like i say you brakes dont have to be as good as a cargo vehicle as it will be tested at what it wieghs not at what it could wiegh if loaded to its maximum. My advice is check it over and take it friendly local commercial garage will give advice on wether its fit to be on road and give you peace of mind.

Just read your post again you say not a load carrying vehicle apart from 4.5 tons suspended that 4.5 tons will be adding minimum 10 tons to the vehicles rear axles

Edited September 27, 2011 by cosrec

[Grumpy]

You have little to no advantage over a normal cargo truck, Militant has a gross design weight of 28 ton and weighs 22 ton c/w CES, it’s nearly up to weight before you start, its design train weight is 50 ton. Because of the short wheel base and how the crane is positioned on the Militant, a 4.5 ton suspend tow will place no where near 10 ton on the rear bogie, the draw back of this is the ability to wheelie when loaded. Ask any one who has had to stop on a bend half way up a hill loaded – ask Poptopshed about a wheeling Militant and the Police car :-D

[cosrec]

 

You have little to no advantage over a normal cargo truck, Militant has a gross design weight of 28 ton and weighs 22 ton c/w CES, it’s nearly up to weight before you start, its design train weight is 50 ton. Because of the short wheel base and how the crane is positioned on the Militant, a 4.5 ton suspend tow will place no where near 10 ton on the rear bogie, the draw back of this is the ability to wheelie when loaded. Ask any one who has had to stop on a bend half way up a hill loaded – ask Poptopshed about a wheeling Militant and the Police car :-D

You want to tell me exactly how much 4.5 tons will put on then i am willing to prove it with calculations. You have all so just proved it has a 6 ton advantage over a cargo vehicle

[Grumpy]

Go on then mate prove it with calculations, I really can’t be bothered to get the tape out and measure the cantilever points on a Militant.

 

Let’s agree to disagree; poor blokes only asked a simple question no need to turn it into a "whose dog is blacker". :yawn:

 

PS If you really want to do the calculations, don't forget to factor in the reactor that is fitted to most Mk 3 Recovery's

Edited September 28, 2011 by Grumpy

[cosrec]

Go on then mate prove it with calculations, I really can’t be bothered to get the tape out and measure the cantilever points on a Militant.

 

Let’s agree to disagree; poor blokes only asked a simple question no need to turn it into a "whose dog is blacker". :yawn:

 

PS If you really want to do the calculations, don't forget to factor in the reactor that is fitted to most Mk 3 Recovery's

 

To be fair all i was saying was take it and try it i think it will pass because even when it was built it will have had to pass certain standards it was you that was putting him of by saying he would struggle or wasting his time

[Grumpy]

Again only speaking from experience with Mk 3 recovery brakes, you can spend days on them and still not get any where near 50% efficiency. One quite well known owner was horrified when he tested his after a refurb. If it’s reading 35% now nothing much will change when at the DOT.

They were borderline when new, its forty years old now, I don’t know the history but unless the brakes have been fully refurbished, personally I don’t think it will pass, but this is only a personal opinion and perhaps looking at the black side. But it’s not unknown for the inspectors to issue a PG9 following a test.:cry:

[N.O.S.]

It's been a (long :-D) while since I've been in a testing station, but I thought the reason for loading a commercial vehicle for test was to ensure the brakes didn't simply lock up on brake application when on the rollers, which for example an 8 wheel tipper would if empty.

 

ISTR putting just over 1/2 the max. load on to ensure successful testing, which would accord with a 50% efficiency as axles would be more than 50% loaded with 1/2 a load.

 

If you take an empty vehicle do they really impose the full carrying load?

Edited September 28, 2011 by N.O.S.

[Zero-Five-Two]

It's been a (long :-D) while since I've been in a testing station, but I thought the reason for loading a commercial vehicle for test was to ensure the brakes didn't simply lock up on brake application when on the rollers, which for example an 8 wheel tipper would if empty.

 

ISTR putting just over 1/2 the max. load on to ensure successful testing, which would accord with a 50% efficiency as axles would be more than 50% loaded with 1/2 a load.

 

If you take an empty vehicle do they really impose the full carrying load?

 

Not only the wheels locking, most modern commercials have a load sensing valve in the brake circuit to alter the balance (front to rear) of the braking effort, and need carry some form of load to get an accurate test.

 

We have a similar issue when testing buses and coaches, you can't have 50 passengers hanging around the test station just so you get have a brake test with a loaded vehicle, so the expected brake values and test standards take this into account.

 

35% on a Militant ain't bad, and in any event the examiner can use a fair amount of personal discretion as to whether to pass or fail a given vehicle.

 

One final point, what ever happens, it is only ever valid as "At the time of testing" once you have left the test centre anything could happen

[Iain Crosbie]

35% on a Militant ain't bad, and in any event the examiner can use a fair amount of personal discretion as to whether to pass or fail a given vehicle.

That's interesting to know. I assumed the pass was 50% and anything less was an automatic fail. That was why I had asked about the Mk 1 brakes. As far as I know the braking arrangements are similarly unsophisticated, but a Mk 1 could pass because of different conditions applying due to its age, whereas the Mk 3 would have to comply with more recent regs.

Do the regs allow a vehicle to pass if it is as good now as it would have been when new, or is that not part of the thinking?

[Zero-Five-Two]

Do the regs allow a vehicle to pass if it is as good now as it would have been when new, or is that not part of the thinking?

 

Generally speaking yes. If that is how it was when it left the factory, then that is good enough for today.

[Iain Crosbie]

Generally speaking yes. If that is how it was when it left the factory, then that is good enough for today.

Are there historical records somewhere which would list the original brake performance?

[Grumpy]

Just to clear up the figures,

 

Minimum Service Brake Efficiency:

 

2 axle Rigid pre 1968 – 45% DGVW

More than 2 axle rigid or tractor unit pre 1968 – 40% DGVW

Any vehicle pre 1915 - one efficient braking system required

Any other vehicle – 50% DGVW

 

Vehicle to be loaded to minimum of 65% design axle weight. (I have never had a vehicle loaded above 70% during test)

 

The above is taken from the 2011 Heavy Goods Vehicle Inspection Manual, this is what the inspectors must test to.

 

So the requirement for the Mk 3 Recovery is 50% DGVW

 

As far as Prohibition (PG9) at test, the following is listed regarding service brake efficiency, Note the last paragraph:

 

“With the service brake applied:

 

There is little or no brake effort at any wheel

 

Braking effort from any wheel on a steered axle is less than 70% of the brake effort from another wheel on the same axle

 

Efficiency significantly below legal requirements (before issuing the examiner must consider whether the vehicle, as presented, would pose an immediate danger to road safety) ”

 

Hope this helps

:thumbsup:

[julezee001]

My Mk1 Militant cargo, with the Atlas crane fitted, weighed in at around 16.5 tons this year for the test. Without the box body with essential spares, cooker, sink, bed and camping kit it's about 12 tons. This year there was a reading of 51% on the tapley meter for the footbrake test, despite not reaching the required 20mph.

 

The handbrake was also tested as the secondary brake also passing at about 30%, although it wasn't a very accurate reading for various reasons!

 

The VOSA tester hates the idea of testing with a Tapley, but owing to the intervention of more savvy people he had to relent and use one. He reckons that if a house brick on its side falls over when the brakes are applied, that's about 50%, and if it fall's over when stood on end it's about 25% efficient.

 

In almost 20 years of driving my Militant, I've never been worried about the vehicles brake efficiency. It's always stopped really well. I'm far more concerned about the failure of a main hose, or some other failure, and having to then stop in a hurry.

 

I have had major hassle over the years getting through brake tests, mainly through imbalance, but have so far always succeeded eventually. It's probably helped that the GVW of my truck was 22.5tons , thus the brakes should pass with that weight, then they should manage at 16.5 tons.

 

Jules

[cosrec]

Just to clear up the figures,

 

Minimum Service Brake Efficiency:

 

2 axle Rigid pre 1968 – 45% DGVW

More than 2 axle rigid or tractor unit pre 1968 – 40% DGVW

Any vehicle pre 1915 - one efficient braking system required

Any other vehicle – 50% DGVW

 

Vehicle to be loaded to minimum of 65% design axle weight. (I have never had a vehicle loaded above 70% during test)

 

The above is taken from the 2011 Heavy Goods Vehicle Inspection Manual, this is what the inspectors must test to.

 

So the requirement for the Mk 3 Recovery is 50% DGVW

 

As far as Prohibition (PG9) at test, the following is listed regarding service brake efficiency, Note the last paragraph:

 

“With the service brake applied:

 

There is little or no brake effort at any wheel

 

Braking effort from any wheel on a steered axle is less than 70% of the brake effort from another wheel on the same axle

 

Efficiency significantly below legal requirements (before issuing the examiner must consider whether the vehicle, as presented, would pose an immediate danger to road safety) ”

 

Hope this helps

:thumbsup:

 

 

I know you have or had a militant did you ever take it for a test. If not (i know it was or is exempt testing) think to yourself i was or could be knowingly riding about with substandard brakes. Oftence trying to stop a lot more than the its designed wieght.

also as i said you wont get a prohibition order due to moderatly low efficency only if certain brakes arnt working or the vehicle is down right dangerous. I admire the guy for trying to satisfy his own mind

Edited September 28, 2011 by cosrec

[Grumpy]

Hi Jules

 

Must admit I have a soft spot for the MK1, and most that I have driven have had good brakes. Problem with the Mk 3 recovery is the shear weight of the thing, its 22 ton before you start to load it. The rear brakes are larger on the Recovery than the Mk 3 cargo version but the cargo’s do stop better even with the smaller brakes.

[Grumpy]

I know you have or had a militant did you ever take it for a test. If not (i know it was or is exempt testing) think to yourself i was or could be knowingly riding about with substandard brakes. Oftence trying to stop a lot more than the its designed wieght.

also as i said you wont get a prohibition order due to moderatly low efficency only if certain brakes arnt working or the vehicle is down right dangerous. I admire the guy for trying to satisfy his own mind

 

Yep still got it, the best we have managed to get it is 53% but believe me it bloody hard work, I think up rating the front chambers from type 20 to type 30 would help but not sure the drums will take it. Experience tells you when the brakes are going off, annual test tell you nothing really and I doubt many do an efficiency test at each maintenance inspection.

 

The Militant is not the only ex-military vehicle with poor brakes in fact a lot of old vehicles struggle to meet the requirements for test in lots of areas, its all part of the joys of ownership.

 

As far as knowingly using a vehicle that does not meet a particular standard or regulation – I thought this forum had got past this sort of self inflicted damage to our movement.

Edited September 28, 2011 by Grumpy
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