Rolls-Royce's technical director at Shrewsbury talks about the quality of
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castings, tightening up standards at the foundry, turbo-compound engines and twostage turbocharging
"THE most important thing that concerns me is quality of the product." The words of Brian Leverton, technical director of Rolls-Royce at Shrewsbury, explaining his job philosophy.
Quality control for the present and research and development for the future are his responsibility.
One of his rnain aims in seeking reliability and durability is to decrease the sensitivity of the product to abuse.
Brian has always been concerned with the quality of castings from the engineering standpoint. He accepts that there will inevitably be some castings which have to be scrapped; the trick is to keep the scrap rate to the minimum. "My idea of a percentage is different to theirs," says Brian of his foundry suppliers.
He has been encouraged since his clamp down on casting quality by the reaction from his various suppliers. It is worth pointing out, lest Mr Leverton be accused of humping RollsRoyce's quality control problems on to the foundries, that over 75 per cent of all the defective material picked up on inspection is castings and forgings. Castings are the main problem, whether ferrous or alloy.
The tightening up on foundry quality control has spawned other ideas. Foundries have been developing new production techniques to decrease the scrap rate and have found that, in certain cases, the performance of the final component has improved.
The big Vee engines provided the foundries with a difficult problem. Because the configuration is more compact than with an in-line design, there is little margin for movement of the cylinder barrels. A lop-sided barrel with one side thick and the other thin can be discovered early on, but if porosity is the problem then it is quite possible that this would not be discovered until the final machining stage. Much time and money would have been wasted.
Rolls-Royce is now placing more and more components on to a casting guarantee scheme with its suppliers, and the benefits have been obvious. Improvement in quality is, however, a ouble-edged sword, for as rian Leverton pointed out: "If e improve the product in a cerlin area, the implication is that e were weak before but like teryone else we are constantly ancerned with improvement
f the product."
Extending the oil drain period something which some of the I companies, in conjunction ith the engine builders, have 3en advocating for some time. rian is in two minds: not op)sed but, on the other hand, yt 100 per cent in favour, either. "We've been slow in formally (tending our oil change period it some of our customers went lead and did it anyway."
What concerns Brian is that ails-Royce has to accept that ere are operators who do not ok after their engines. He is so concerned about the dedopment of so-called "eco)my oils", which in his opinion lye been over-sold by the oil impanies.
The claimed benefits in fuel :onomy thanks to these oils Ime from a lowering of the visisity, and this can be taken too r. Brian thinks that one or two the oil companies have shown ime responsibility in this area it, unfortunately, "if someing goes wrong, we catch it — )t the oil company."
For the eighties, Brian Leverton envisages an increased requirement for engines in the 225 to 300kw (300 to 400bhp) category, in conjunction with the obvious aims of decreased weight and improved reliability and durability.
Several of Rolls-Royce's rivals in the automotive field are working on adiabatic engines with insulated combustion chambers using, for example, ceramics or stainless steel. Shrewsbury is watching such developments with interest but as Brian explained: "We don't propose to become an authority on adiabatic engines. My priority is with other matters."
While obviously not neglecting such technical developments, Rolls-Royce is cur
rently concentrating on Cost control and quality assurance. Unglamorous and tedious the work may be, compared with the comparatively exotic future concept work, but it is nevertheless of vital importance.
Turbo-compound engines, where the turbocharger is geared back through to the crankshaft via a fluid coupling, are a long way from the production stage according to RollsRoyce, but Brian Leverton stressed that this was very much a personal view.
Two-stage turbocharging, where two turbochargers are linked in series, is envisaged for future use in the generator set market but not for lorries. "Does the operator want it?" asked Brian. "You double your turbocharger failure probability and you take up more space."
Charge cooling, however, is one feature that Brian does see as having increased application to automotive engines in the future. The company will retain the air-to-water system preferred by most of the proprietary engine builders, who can then retain the engineering integrity of the charge-cooling system without relying too much on the chassis manufacturers' installation. There are other advantages too, of course, including a compact installation.
Against this, the air-to-air adlure drop and thus greater effivocates claim a bigger temperaciency, but Brian Leverton argues that this improvement is but marginal and only occurs in certain conditions.
Rolls-Royce now fits liners impregnated with silicon carbide to all its turbocharged engines and this has improved liner life and decreased oil consumption to the point where 0.2 per cent is considered the norm.
The carbide finish was introduced to eliminate a problem with bore polishing, which for reasons Rolls-Royce has never yet understood, only occurred with engines operating in Finland. Whether it was due to the quality of the locally available fuel or to the extremes of temperature has not yet been ascertained. The polishing problem did not show up until 250,000km (155,000 miles), and has now been eliminated completely, so the carbide process has been extended to the entire turbocharged range.
Not surprisingly, the carbide process costs more but R-R obviously feels that it is well worth the money. There is no intention (or any need, for that matter) to carry the process over to the naturally aspirated engines but Rolls-Royce does not now make many of these anyway.
Rolls-Royce has long been involved in paring excess weight from the basic engine structure and this exercise is still going on. An investigation had showed that the cylinder block had "grown" over the years because bosses and lugs had been added which had nothing to do with the design itself. If a particular machine tool was replaced it very often necessitated different handling points which meant extra bosses. The original ones, however, were not removed.
When Rolls-Royce started this weight •reduction exercise, all the superfluous metal was removed. In fact it never went on, as the foundry drawings were altered to eliminate the extra metal before the blocks were cast.
Brian Leverton's target weight for the engine, including fan, flywheel and electrics, is 1,000kg. The figure currently stands at 1,100kg (21.6cwt), but, says Brian, "we'll get there".