BXProject

[Bx Bandit]

............breaking apart is what caused the 2.1 in the Xantia to die! The rubber part had got itself tangled up with the timing belt and I removed the biggest part of it from round the camshaft! The timing is all to pot which I'll re-set tomorrow but I suspect things will be unpleasant valve wise.

[jonathan_dyane]

Bad times! Harmonic balancer; what in the world is that madness?? I can't say that I for one have ever been troubled by harmonic vibration...

[docchevron132]

Tis the damper by another name!
They are known for it.
Pull the rocker lid and have a ganders. You might find everythings ok.
By far the weakest point of the top end is the rockers, they may well be smashed, but replace them and you might find it goes fine. I've rebuilt a couple now that had belt failure, both smashed the rockers, replaced rockers, both are still going.

I may even be able to find some laying around, I did have a scrap head somewhere...

[Bx Bandit]

Thanks for the advice Doccers....I've not been arsed the last few days but i will have a butchers when I can muster the urge. Ta mucka.

JD, I have no idea mate, a supposed step forward in the name of refinement....

[docchevron132]

no no, it's critical.
It's sole purpose is to stop the crank from smashing itself to pieces.

[Bx Bandit]

/\ Oh! So it's one of the first things to strip to prevent major internal damage???? I guess from experience they should be replaced at particular intervals!?

[Philhod]

Just goes to show, your never too old to learn. I thought you had to have two sources of resonance that were interfering with each other, to need to adjust the harmonics.
I was unaware that such a level of discord could be produced by one motor alone

Yes I know it happens in turbines. Although it's one shaft, there are between 10 and 16 stages of blades to argue with one another

[docchevron132]

/\ Oh! So it's one of the first things to strip to prevent major internal damage???? I guess from experience they should be replaced at particular intervals!?

Erm, they need replacing a little bit before they fail, as you found out!
Some seem to last forever, some last about 60K miles and disintegrate.
HDi's are very prone to it.

Not quite mate, run one without the balancer and the engine will implode sooner or later.

I need a new one for the ambulance... likelyhood of getting one....er, fucking zilch. Hence I'll have one made!
Since I'll never find another crank...

[Bx Bandit]

/\ Oh! So it's one of the first things to strip to prevent major internal damage???? I guess from experience they should be replaced at particular intervals!?

Not quite mate, run one without the balancer and the engine will implode sooner or later.

I need a new one for the ambulance... likelyhood of getting one....er, fucking zilch. Hence I'll have one made!
Since I'll never find another crank...

So it's to stop the engine shitting itself to death???? I've shoved the damn Xantia on the drive and there it will sit until I can be figged to fiddle with it..........and I really....really can't be arsed!

When you gonna do that Ambulance Doc? After Dennis?

[Philhod]

That's about it Bandit,
All revolving machines vibrate. this set's up resonance which can be measured in ultrasonic wavelengths. some wavelengths are "smooth" and some are downright destructive. these can be alleviated by setting up another wavelength to counter it's effect.
I dont know how the xant one works but bit's usually in the form of a counter rotating shaft, producing similar but opposite vibes, thus nullifying the effect.

If you picture an oscilloscope with a sine wave on it, you would need to produce a second wave of the same height and length, but with it's meridians exactly mid point with the first one.

OR...................................... it's to stop it vibrating to bitz


Seriously, You can release the welding stresses in a fabricated structure that's too big to go
in an oven. by clamping cables to it and setting up opposing resonances.

I've actually seen where 3 electric motors were running next to each other. The discord caused the sheet metal guards to crack.

[Bx Bandit]

Well Phil, would you believe it............Citroen have made theirs from cheese! Your version sounded very mechanical.........Cit just bunged some cheese inbetween two bits of metal to 'dampen some shit out!'

[jonathan_dyane]

Why is it then that the XUD turbos manage without?

[Philhod]

Err that would have been the bit about "smooth" frequencies. until a motor is built and tested for the first time, you don't know what frequency it will produce.
Well you can predict it to some extent, but it's far to boring to explain on here..... height, width, length,weight, mass, versus revs calculations.

[Bx Bandit]

Good point my ginger tater! I have no idea. I was even tempted to put one on the BX to see what happened but I'll be fucked if I'll bother now......

edit.....my ginger tater being JD for Phil has no colour.............!

[jonathan_dyane]

Ah, I see, it's the about the specific *frequency* of the vibration kinda thing! I understand, and can see how the (lovely smooth) IDI XUD would have a somewhat different frequency to the (harsh and crude) DI HDI. Something like when you're smashing a cast iron bath with a hammer, and it's about the tune you play rather than how hard you hit it (sed actress to the bishop etc...)?

[jonathan_dyane]

Good point my ginger tater! I have no idea. I was even tempted to put one on the BX to see what happened but I'll be fucked if I'll bother now......

perhaps it would be more fun to fit a solid crank pulley to the Xant and note how long it takes before (and under what conditions) the big BANG!

[jonathan_dyane]

Rambling about HDI's

Soddit, it's a 2.1 not an HDI isn't it! I blame the beer...

[Philhod]

The smoothness of the engine is not a factor really. The 2.1 just has bad vibes, it runs smooth enuff. IDi's have a longer burn, which I suppose, should smoothen it.
Yet the HDI has a very short burn and conversely is also very smooth running......
Go figure?????

[docchevron132]

Ahh, but HDI's have a damper aswell, also well known to shit the bed at impromptu moments!

The TD doesn't have a damper / harmonic balncer thing because the crank is beautifully counterbalanced as is.
The N/A's have a damper because the crank is not so well tuned.

It also serves to smooth the impact on the crank when the alternator has work to do (ie when you turn the lights on etc) and when switching in air con and the such..

[Philhod]

Err ..i knew that......Actually I didn't, I havn't even got a manual for the Picasso yet.

I got a bit of warranty from Rigbye's when I bought it. I've just sort of driven it since then,I don't need one for servicing. However, D has just bought one to do that Lift pump, so I suppose I had better have a read.