CVRT questions

#3
What you need to calculate is the Mean time before failure MTBF obviously each component has a MTBF and this needs to be considered.By the way that information is restricted and will not be covered here.

However heres a MTBF for a car so you understand the complexities of the calculation.

Having a reliable car is important to just about everybody. The following equations illustrate how you could compute the reliability and availability of your car knowing the expected life of a few key components:
Expected Life of Key Components

MTBFPower Train = 1500 hrs (90k miles @ 60 mph)
MTBFTires = 1000 hrs (60k miles @ 60 mph)
MTBFBrakes = 666 hrs (40k miles of city driving)


Time to Repair Car if Key Component Failed


MTTRCar = 24 Hrs

Computing Reliability of Car


1/MTBFS = 1/MTBFa + 1/MTBFb + 1/MTBFc
1/MTBFCar = 1/1500 + 1/1000 + 1/666
MTBFCar = 315 hrs

R = e-t/MTBF (0-1, 1=Perfectly Reliable)

Reliability of Car after 100 hours of operation:


RCar @ 100 hrs = e-100/315 = 0.72 (72% chance of operating without failure)

Computing the Availability of Car


Availability (% Up Time) = MTBF / (MTBF + MTTR) (0-1, 1=Always Available)

Availability = 315 / (315+24) = 0.929 (92% chance of being operational at any point in time)

So, the car is available 92.9% of the time for use. This level of availability might be acceptable for the majority of people. For others with different circumstances, a higher level of availability is a requirement. For these people, some form of redundancy is required, a second car that can be used while the primary car is being repaired.


System Reliability/Availability With Redundancy
In redundant systems where the repair of a failed component can take place with no interruption to system operation and the backup unit is in standby.



Typical System Reliability/Availability for One of Two Cars
Extending the example of cars, the following equations compute the availability of having one of two cars operational in a family:

From the previous example:


MTBFCar = 315 hrs
MTTRCar = 24 Hrs



MTBF 1car out of 2 = 4764 hrs (Versus 315 for 1 car)

Reliability of having one operational car from a two car system after 100 hours of operation:


RCar @ 100 hrs = e-100/4764 = 0.979 (Versus 0.72 for 1 car)

Computing the availability of a car in a two car system:


Availability = MTBF / MTBF + MTTR (0-1, 1=Always Available)

Availability = 4764 / (4764+24) = 0.995


In a two-car system, 99.5% of the time one of the two cars is available for use. As contrasted with a one-car system, where 92.9% of the time there is a car available for use.
 
#4
It's for a Spartan. Sorry I should have said, I intend to use one (private Civi one) on the road quite a bit, I was just wondering if this is going to be at all practicable. Or do I need a spare gearbox, engine etc ready. thanks.
 
#5
It's for a Spartan. Sorry I should have said, I intend to use one (private Civi one) on the road quite a bit, I was just wondering if this is going to be at all practicable. Or do I need a spare gearbox, engine etc ready. thanks.
 
#6
Mate you will have a lot of work on there . I take it , it has the JAG 4.2 petrol engine if so engine parts are not too bad to get hold of but gearbox , running gear etc will be tough . You will have to be really keen to keep that spartan on the road .
 
#7
Also, the AA don't do recovery plans for CVR(T), so when it breaks it will be expensive to get it towed home :)
 
#8
why would u want to your very own spartan? are u mad, they are a pain in the arrse at the best of times, hope u have the man hours to graft on the thing! what u gonna use it for shopping at asda, like to see that in the mother and toddler bit!. hope u have wone the lottery to fill the thing up.
 
#9
Once consumer to consider will be; track pads, 6 monthly inspectionS, mission servicing and heavy forbid you need a new J60 powerpack.Gearbox is a pig to work on aswell.
 
C

cloudbuster

Guest
#10
QManWpns said:
Once consumer to consider will be track pads, 6 monthly inspection mission servicing and heavy forbid you need a new J60 powerpack.Gearbox is a pig to work on aswell.
Whadeesay???

Someone's started the session early.'8)
 
#12
thought as much. I had a friend who had a civi cvrt that had his j60 engine blow up. Big hole in his sump. As track pads are not removable it they are very expensive to replace as they wear out pretty quick. It is just I have never run one for a long period of time. I have been about 10 miles max (No problems then). I have heard gearboxes are prone to going over long periods.

I just wondered how long you could go in 7th gear at 50 miles an hour without something cracking, breaking etc. Are the diesel engines any better?
 
#13
Diesals are better better they wear the gearbox quicker , as for 50mph in 7th it all depends on how good the running gear is , track should be condemed at 500 miles or less than 79 links ( remeguys correct me if i am wrong) could work out shit loads of money to keep on the road .
 
C

cloudbuster

Guest
#14
On top of your fuel bill, Alvis (now part of BAe, along with Vickers) won't part with spares for anything less than mega-bucks, as they've got some lucrative overseas refurb contracts coming up.
 
#15
4.2 Jaguar XK engine is one of the best petrol engines ever made

Serviced properly with specific attention to cooling and they last for decades.

Dont know which variant the CVRT uses presumably carb fuelling? if so which carbs?

Converting to a straight port head and injection will up economy by about 20% an LPG conversion will knock of another 40-45% off fuel costs, unleaded fuel is no problem for any of the engines
although they do like a higher octane than your average hatchback :D

Maintained properly (lots of oil changes and coolant changes) they are virtually bomb proof
 
#17
Sounds like it is the worst of all the XK variants, from the era where they tried o make them comply with to many regs without spending any money.

The cylinder head from a post 1979 Jaguar car will bolt straight on and transform the engine, converting to injection at the same time will boost performance and economy considerably, the first thing to do if you dont want to spend a fortune on it is make sure it had 2" SU carbs and not Strombergs

Completely change coolant at least every 6 months, use at least 50% anti-freeze with corrosion inhibitor (preferaly UniPart), flush cooling system thoroughly at the same time. Do not use any from of chemical leak sealer (radseal type stuff)

Primary cause of failure on the XK are cooling problems, Oil changes are equally important use good oil, they have quite a high oil consuption rate so check it frequently, cam chains can wear with heavy use but generally dont cause problems. USe genuine JAguar parts, it will save you a firtune in the long run
 
#18
Dont want to piss on any bodys chips but they binned the jag engine for a reason . It might be a great car engine but in 8 tonnes of CVR(T) its gonna struggle , the engine is the least of your worries , gearbox will go tits up in the end and are you going to get a replacement ? however if you are mad for a spartan best of luck , and dont forget to bleed the brakes often .
 
#19
part of the reason the Jaguar engine isn't upto the job is because it utilises the worst version available
also it was designed as a thoroughbred high perfromance engine not long after the second world war. Its maintenance requirements are high and if it does'nt get it it'll suffer.

You are right though it was never designed to haul 8tons about

In the state of tune its in when fitted to the Spartan the engine is operating at less than 60% of its performance, consequently its working harder than it should. long experience with this engine shows that if you let it work the way it was designed to it becomes an awful lot more reliable

With the modifications suggested bhp and torque will be increased by about 50% (yeah sounds simpler than it actually is) and reliabilty will improve.

I know sod all about the transmissions in them, so cant really comment, whats the gearbox and final drive arrangement?

The biggest think with the XK unit is that now modern parts materials can make it a better engine than it ever was new.

Personnaly I'd pull the thing out and chuck a cummins turbo in it, bout the right power, massive fuel saving, reliable and the rightish physical dimmensions.......
 
#20
I looked into changeing the head on a mates J60 after his blew up. I was told the gearbox would not be able to handle the extra power. I belive the gearbox is the weak link.

The guys over at Repaircraft (http://www.scorpiontank.co.uk) seem to have sorted the problems out by putting a new diesel engine in it. The same as the new Bv206 I belive. But they only sell to govenments etc. Which is a shame.
 

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