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the lack f it, has been the most nportant factor in the cceptance of speed miters and Lucas ienzle has been rorking on how to iprove the efficiency these useful but till BA/ problematic atines
'AD SPEED limiters for trucks ve been around for a while w but their use in coaches has an less extensive.
lowever, there is a very defi.e dividing line between _tilers and coach operators as as speed limiting require!tits are concerned: the -tier is looking for increased I economy while the coach )rator is under pressure to imve safety and comfort.
,nother difference is that the :lc tends to be geared for the ticular operation whereas ches are geared above the maximum.
icas Kienzle now markets a I speed limiter which was iched originally for coaches is now available in sufficient ntity to enable trucks to be ared as well. The difference veen this system and the irs already available is that actuation is electronic rather hydraulic or pneumatic.
the early stages, Lucas izle was approached by meveld in Holland which ted an outlet for its speed er in the UK. The suggestion along the lines of "we have woduct — you have the net: and the ability to penetrate narket." Lucas Kienzle tried roduct and suggested a few ifications to suit UK opera had been agreed that the important single factor to wards acceptance of speed limiters in the past has been driveability. Early types of limiter did not help in this respect as, when the vehicle reached its ground speed, it felt as though someone had turned the fuel off — what technical manager Roy Parlett calls "the brick wall effect."
Operators have had trouble in the past because of this brick wall syndrome; drivers did not like the action of the limiter and were thus more likely to find ways of abusing it.
The argument put forward was that if the driveability was better, the driver would not even notice the limiter was in use and his interest in tampering would be minimal.
One of the modifications suggested by Lucas Kienzle was to change the response time to modify that rate of acceleration towards the governed speed. As this suggests, a slight change in driving technique is recommended by Lucas Kienzle, which claims that once this has been explained, the driver can still maintain his over-the-road speed even though the limiter is fitted.
This technique is best explained by considering the case of a vehicle going down hill before climbing the equivalent gradient up the other side. Normally the driver would maintain his legal speed on the down grade to keep up the momentum for going up the hill but this is where the "brick wall syndrome" would apply, according to Lucas Kienzle.
Its recommended technique is for the driver to keep the speed downhill just below the governed speed. With the Groenveld limiter, the road speed is allowed to exceed the pre-set limit briefly and is then gradually pulled back.
To put some numbers into the explanation, a limiter set at, say, 60mph will not stop the speed increase dead on the 60 mark. It will permit the vehicle to reach say, 64/65mph and will then pull the speed back down to the predetermined. Thus it is possible to accelerate thr.ough the limit to achieve a good hill climbing performance at least as good as the unrestricted vehicle.
Which speed is selected as the upper limit depends on a combination of operator requirements and the torque curve of the engine. If the chosen speed is wrong, then the operator will not see the expected improvement in fuel consumption and, for this reason, Lucas Kienzle does not regard fitting as a diy installation.
With the Lucas Kienzle trained fitters, an installation should take four to six man hours for a known vehicle. Where it is a new vehicle — as far as fitting a speed limiter is concerned — then it could take up to a day.
If the vehicle has a mechanical tachograph then the company recommends the use of an impluse generator speed sensor. This is not required with an electronic tachograph which is already fitted with a speed sensing contact in the back.
Sensing the road speed from the prop shaft is not recommended by Lucas Kienzle. As Roy Parlett explained: "It's not just because we sell tachos. The prop shaft system is too open to abuse." Apart from that, the tachograph is already part of a sealed system so it makes sense to use it.
The Groeneveld system also gives the option of a variable speed control which can be selected at will. This does not effect the pre-set maximum speed but if the vehicle is operating on A-roads with a 40mph limit then the driver can operate a switch when the tachograph needle reaches 40. The vehicle will surge above this speed and then hunt back down as in the case of the recommended hill climbing technique.
Flicking the switch the other way releases the limiter — there is no "kick down" release. With this system the speed control is thus infinitely variable if required.
The limiter operates on the fuel pump rack based on road speed but it can also accept a separate signal with respect to engine speed using the same type of sender. This is currently an option with the Lucas Kienzle limiter rather than a standard feature.
The actuator is fitted within the frame rails or across the chassis under the radiator bui alway using existing holes or the chassis wherever possible Because the very nature of al electronic rather than mechanical system means tha the cable does not rotate, it give an enormous latitude for instal lation.
I tried the Lucas Kienzlespee limiter fitted to a Dodge Corr mando rigid and can report thE the recommended driving tech nique is very effective. When th limiter was actually operatinE the engine note tended to soun flat, gradually getting "harder as the road speed dropped bi low the limit speed due to a gn dient.
To overtake a slower vehicle, dropped the speed slightly br low the programmed limit an accelerated past when th equipment would hunt be( down again.
There were no problems at E with lack of driveability a though, as Lucas Kienzle readi admits, driver tuition would I essential to get the best from it.
As far as price is concerne the component breakdown is follows: Actuator £103.08 Control module £118.60 Control cable £43.37 (Impulse transmitter fr mechanical tacho £28.06) 5m of electric cable £17.37. The engine speed limiting o tion adds the cost of another ir pluse transmitter.
Lucas Kienzle claims to I able to cover most popul coaches (and the majority heavy lorries as well) and to dE the company has not found a make where installation h proved impossible.
With speed limiters r coaches the driver can conce trate more on what is going around him without worryi about his speed because knows it will be legal. Anoth forgotten advantage is that can brace himself with both fe