Thread: Modified 300tdi v standard td5 power?

Originally Posted by uninformed

Zeus timing gears have their own set of issues

Only if they're not installed well

Originally Posted by Blknight.aus

Only if they're not installed well

I disagree, so do a few people with much great mechanical and engineering experience than me, and dare I say it.... you.

Originally Posted by Blknight.aus

Only if they're not installed well

They have proven to be a failure,Modern Motors at Dungog have a set that stripped after a short period,they refuse to fit them. Pat

Originally Posted by Blknight.aus

Only if they're not installed well

Bulldust.

They may be OK now, but it has been proven through several independant engineers' assessments that they are/were crap.

See below one such report done at the request of Turner Engineering.

Folio No: B7847
Report No: 1
Client: Turner Engineering
Order No: letter
Attn: Mr Turner

Date: 10th May 2002



TECHNICAL REPORT



EXAMINATION OF ZEUS TIMING GEARS

FITTED TO LAND ROVER 200 TDI ENGINES







J CAMPBELL




SYNOPSIS

The timing gears are plain hobbed, and the geometry is so poor that only the edge of each tooth on the camwheel gear has been in contact with the mating gear. This has resulted in physical damage to the tooth face, resulting in pitting and fretting damage. This area will be susceptible to fatigue cracking as the fretting worsens, resulting in tooth fracture.

The fundamental problem with this system appears to be the poor quality of the gears, resulting in incorrect meshing of the gear teeth. The rough, hobbed surface makes the quality of mesh that much more critical.

INTRODUCTION

I was asked to make an examination of a set of gears manufactured by Zeus Ltd, and submitted by Turner Engineering. The samples consisted of a full gear kit with front and rear engine castings, plus two separate gears from another failed 200 TDI kit, and one gear from an earlier S3 kit.

These gears are timing gears designed to replace the standard belt driven timing train on Land Rovers. The system consists of an idler gear, and drive and delivery gears, which replace the drive system fitted to the unit by the manufacturer.

I have experience in gear and transmission investigations over twenty years, and have worked on thousands of gears, and transmission projects including Jaguar 220, McLaren F1, formula one racing cars, and many vans, cars, 4x4 vehicles, and commercial vehicles.

The cause of the particular problems was resolvable by visual examination alone, but I could provide a full metallurgical review of the gears if this is required.

EXAMINATION OF THE GEARS

The two camwheel drive gears were examined first. Both had a rough tooth surface typical of plain hobbed gears, without any tip relief, profiling or final grinding of any kind. On one gear there was smearing of metal deposited from the hobbing process, and this had left a very rough surface of metal smears stuck together and acting like surface laps. The other gear was almost as bad.

The surfaces of the teeth were still showing their hobbing pattern, and wear of the surfaces was only apparent at one edge of the gear teeth. There were scuff marks and pitting associated with the corner of the teeth, and from experience these will ultimately generate fatigue cracks in the case, running into the body of the tooth. They were indicative of tip contact through poor meshing profile between the two gears.

Because the gear is a rotating part, each contact between the tooth tips will generate flexing and loading, which culminates in fatigue cracking.

The other gear had a similar problem, but there were also edge fractures, as shown in the attached photographs.

DISCUSSION

The gear quality used for manufacturing these gears is very basic. These gears are hobbed, which is the first stage of gear manufacture, intended to ‘rough out’ the gear tooth profile. Gear teeth can be hobbed, ground, or ground and profiled, and most engine gears used in motor vehicles would be expected at least to be ground, unless their action is very basic and speeds are modest. The action of two gears meshing against each other should be as smooth as possible, especially where the gears are not running in a bath of oil, such as within this gear train.

The idler gear was found to be loose on its boss, with play of around 0.2mm. The plate holding the idler gear in place has two grub screws, with no shake proof washers. Considering the vibrations involved, this is an insecure fixing and requires at the very least a loctite bonded fixing.

There was no smearing, or discolouration, or any other sign that the gears had ever run without lubrication, and there was no sign of intermittent oil starvation.

Engines can suffer from vibrations if moving parts are not carefully chosen and balanced, and the automotive designer pays a lot of attention to noise, vibration and harshness (NVH). Hobbed gears are not sufficiently smooth in operation to avoid placing vibrations and stresses into the engine. There appears to be some slack in the design of the timing gears, which will add to problems of NVH as well as causing inefficiencies in engine operation because of the variability of the timing mechanism as a result of this slack.

I understand that there have been problems with this engine in that components have failed. It is likely that vibrations from these gears will affect other parts of the vehicle that have the same natural frequencies. This will cause them to oscillate and fail by fatigue. This is the principle on which a number of parts on a vehicle can vibrate until they crack, and fail. This commonly happens to exhausts systems if the clips are broken or if the owner modifies the exhaust.

The cracking of the camwheel gear teeth is a problem that appears to be caused by improper meshing. There is no reason to suspect the fitting of the gears, because there is no damage on any of the clamping faces

If the gear design is consistent within the Zeus timing gear kit, then other failures are likely from similar causes, on other kits in service.

In my professional opinion the gear kits were unfit for their intended purpose.




J Campbell

Ken Wright wasn't impressed with his: Zeus gears anyone

Originally Posted by isuzurover

Bulldust.

They may be OK now, but it has been proven through several independant engineers' assessments that they are/were crap.

See below one such report done at the request of Turner Engineering.

Interesting!

I've only ever heard good things about them, so that's half a shock.

Quite interesting reading a real life engineering report about Land Rovers! Much more enthralling than what we read at UNI!

Cheers
Will

Originally Posted by MR LR

Interesting!

I've only ever heard good things about them, so that's half a shock.

Quite interesting reading a real life engineering report about Land Rovers! Much more enthralling than what we read at UNI!

Cheers
Will

Only ever heard bad things, with plenty of evidence all over the 'net for a very long time.

And they're ****ing heavy.