Vill the Triangle be the standard ,rake-tester?
Page 51
If you've noticed an error in this article please click here to report it so we can fix it.
BY R. D. CATER AMInstBE
ITITH the introduction in the not too V distant future of yearly tests for timercial vehicles which. it is intended.
I take place at specially set up testing lions, it is highly likely that vehicle brakes
I be tested on a dynamic brake testing whine that is being manufactured by iangle Products Ltd.. of Newton Moor 11, Mill Street. Newton, Hyde. Cheshire. Recently COMMERCIAL MOTOR was 'en the opportunity to evaluate such a ter which has been installed at the anchester Corporation cleansing departnit at Water Street, Manchester, and the wits achieved were amazingly close to a . of results produced by a standard )MMERCIAL MOTOR brake test carried out the same time.
Manchester Corporation very kindly aned us a Karrier Bantam refuse collector -rich is used by the cleansing department r training drivers and is, therefore, fitted th dual controls. I carried out a set of 11-pressure stops in the normal manner id achieved average stopping distances Din 30 m.p.h. of 39.5 ft. (24.4 ft./sec.2) ile a Tapley-meter reading of 73 per nt was recorded. The vehicle behaved tremely well during these stops and owed even marking by all the wheels on ch occasion.
To do six full-pressure stops using the talk-gun and tape took me approximately min. and this was in a depot off the iblic roads and without being a danger to her traffic. Also weather conditions on this ;casion were perfect, a point which often ;tracts from the accuracy and adds to the Inger arising when physical testing is irried out on the roads.
When I had completed the brake tests e vehicle was taken into the testing shop the Corporation department and in 1 min. 5.8 sec. almost identical results were town, except in this case we were able to certain exactly how much effort was being wiled to each individual wheel, whilst at ie same time making a check on the mdition of wheel bearings and the free inning of transmission units.
Most important was the fact that no anger was encountered by the person Ding the test or by any innocent bystander
who might well be involved should a brake or mechanical failure occur while a road test was being carried out.
The Triangle machine is simple, extremely reliable and efficient. It comprises two pairs of rollers which are driven by two 5 h.p., motors, to revolve at 5 r.p.m. The drive is taken through a series of chain-belts, worm and wheel and roller-chain drives from the motor to each pair of rollers. Each individual pair is capable of being motored in both directions to enable differential action to be os'rercome when testing rear axle brakes.
Results obtained with the machine are read off two 10 in.-diameter, expanded-scale hydraulic meters and because of the expanded scales, readings are extremely accurate for testing all classes of vehicle from light vans up to the heaviest commercial. The weight applied to each individual pair of rollers must not exceed 5 tons.
The Corporation vehicle tested produced the following figures on each individual wheel: handbrake--nearside rear. 11 cwt.; offside rear 11 cwt., making a total effort of 1 ton 2 cwt. With footbrake—nearside front. 15 cwt.; offside front, 16 cwt.; nearside rear, 12.5 cwt.; offside rear. 11.5 cwt., making a total effort by the four wheels of 2 tons 15 cwt.
Using the Triangle slide rule this figure placed over the total weight of the vehicle, which was 3 tons 10 cwt., produces a brake efficiency of 78 per cent and shows a distance of 38 ft. as being that required to bring the vehicle to rest from 30 m.p.h. Comparing this result with those recorded on the COMMERCIAL MOTOR style tests, it will be seen that there is a difference of 5 per cent on the Tapley reading and 1.5 ft. difference in the actual stopping distance. I put these differences down to the road surface on which the tests were carried out, which was smooth tar macadam.
In order to ascertain the usefulness of the machine with regard to diagnosing trouble in vehicle braking systems I went to the nearby meat market and asked the driver of the first vehicle that passed by if he would be willing to submit his vehicle to a brake test. He agreed to this and had a severe shock when the machine showed his offside rear brakes to be out of action.
Other than the rolling resistance present at the wheels no reading was recorded by this particular unit when either the footbrake or the handbrake was applied. In fact the braking system of the vehicle which had, according to the driver, been overhauled only a short time previously recorded only 34 per cent efficiency on the footbrake and only 7.5 per cent on the handbrake. This —on a machine which scaled 8 tons 8 cwt. on the Corporation weighbridge—represents a minimum stopping distance from 30 m.p.h. of 89 ft. and the handbrake with 7.5 per cent efficiency would not be capable of holding the vehicle on any local railway station bridge.
If one considers the amount of time that can be wasted in a workshop in trying to eliminate possible causes of poor brake performance it is not difficult to see that at ,E1,950 installed, the Triangle Brake-Tester used in conjunction with a big fleet could very soon pay its way by virtue of shorter down-time periods.