BMW Accelerator jam car hits 135mph

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On Mon, 13 Mar 2006 22:12:03 -0000, "Huw"


Of course it clutches and declutches; the torque that is transmitted is controlled by the speeds of the two shafts. As a rough approximation it's proportional to the square of the difference. Hence at high RPM the clutch is fully engaged for a few percent slippage, at low speeds it slips like mad with very little torque transmitted. But whatever you call it, there is no torque conversion whatsoever. So if mechanics insist on calling it a torque converter it is only because they are ignorant of what it does.
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A fluid flywheel doesn't provide torque multiplication. They were used on pre-selector gearboxes fairly common on some pre WW2 cars. And on the first common auto on UK cars - the GM Hydramatic that Rolls and others used. A torque convertor has a different construction.
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wrote:

I have quite good knowledge of industrial applications [it is part of my business] and the only difference in many applications is the stall speed and terminology. I am thinking specifically of ZF transaxles which had an option of with or without fluid flywheel aka low stall speed torque converter. On engines with a maximum rated speed of 2200 these things more or less lock up at 1100erpm which is a high idle. The primary purpose is to reduce wear on the primary dry traction clutch.
The reason that there is no way you can define a torque converter as a clutch is that it does not actually 'clutch' or 'declutch'. Substitute 'grab' for the word 'clutch' and you should see what I mean; grab or degrab.
Huw
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Huw, with all respect, you need to do a bit of research. The construction of a fluid flywheel and torque convertor *is* different. Google will come up with the answer.

I'm no expert on industrial equipment - this is a car group. But I've owned car autos with both fluid flywheels and torque convertors, and the big difference is the FF acts more or less like a normal dry clutch in that it has effectively no action once the car is moving. A TC is obviously in action in all but the highest engine speeds. Of course many autos lock it out under some circumstances since it's not the most efficient way to provide torque multiplication.

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wrote:

A Lanchester?
and torque convertors, and the

Yes, that type of coupling is certainly more of a clutch than a torque converter.
A TC is

Almost all torque converters fitted to modern cars have a lock-out mechanism which, surprise-surprise, requires a CLUTCH to work.
LOL.
Huw

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Close. The first one was actually a BSA - but of course with a pre-selector box, not auto.
Rolls Royce didn't use torque convertor autos until something like '68. They had fluid flywheels. As did Mercedes.

But your definition of a clutch is like a light switch? ;-)

But not an on/off switch. ;-)
BTW, the Borg-Warner DG box fitted to things like late '50s Rovers and Jaguars had a TC lock out clutch which only operated in top gear.

Didn't realise you were an AOL customer.
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wrote:

Well yes actually. It is either engaged or disengaged with, in most cases, a degree of softeness to the actuation or 'soft modulation' designed in.

Even these had an actual CLUTCH to lock the torque converter then.
Huw
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So what? It still didn't operate like an on off switch. It modulated the speed of lockup - same as you do with the clutch on a manual transmission when starting from rest.
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wrote:

Yep. It modulates between the on and off position, neither of which is possible with a torque converter without a separate clutch to facilitate.
Huw
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A conventional clutch allows from zero to maximum of the engine torque to be transmitted. A torque convertor acts like a continuously variable gearbox and multiplies the torque by producing a lower rpm output than the engine.
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London SW

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manual transmissions, you know that an engine is

You are having a laugh aren't you? It purely connects and disconnects drive from the engine to the transmission. A torque converter is in effect a fluid flywheel which throws oil from the front part to the back. At low revs it slips like heck and continues to slip to what is called its stall speed or to where a clutch engages full mechanical drive to by-pass it.
I wonder what you think torque is converted to, in the context of your answer to your own question?
Huw
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wrote >> "If you've read about

No it doesn't it facilitates a variable torque conversion mechanism :O)

Yes its a liquid clutch.

It's not a name I would choose for a clutch, what do you think it is converted to in a torque convertor?

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aren't you? It purely connects and disconnects

Rather than waste my breath or keyboard finger on you, I'll simply refer you to http://auto.howstuffworks.com/torque-converter.htm
Huw
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wrote >> You are having alaugh

Yes I suspected you would have had trouble understanding that :O|

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wrote >> You are having a

Wriggle and squirm all you like. Just read the article and related links to conventional clutch and automatic transmission [which have wet multiplate clutches within]. It will help you a lot. As a direct answer to your question, power is converted to torque at a lower speed and waste heat. In effect it slips. This is not the case with a conventional clutch which is just an on/off switch. You should have known this even if your engineering experience was limited to school metalwork :o]
Huw
Huw
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On Sun, 12 Mar 2006 18:52:22 -0000, "Huw"

What you seem to be describing is a fluid clutch. In a fluid clutch there is no gain in torque so there is indeed slippage and a lot of wasted power that ends up as heat. In a torque converter, there is an increase in torque to make up for the decrease in speed so most of the engine power goes through instead of being wasted as heat. The heat that they do produce is just frictional, it's not inherent in the device.

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On Sun, 12 Mar 2006 18:52:22 -0000, "Huw"

No, a conventional clutch is designed to allow an intermediate, slipping position whilst an on/off switch has no such intermediate position. The fact that a conventional clutch cannot endure *sustained* slipping does not mean that it is not designed to slip - if it were not so designed, the manufacturer would have fitted a simpler dogtooth clutch rather than a plate clutch.
An electrical analogy would be a rheostat used to provide "soft start" to e.g. large incandescent lights. I have come across such units that are not designed to be left in the half-way position, and will burn out if they are used as a dimmer.
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wrote:

You can have all kinds of refinements to the design including running multiplates in a pressure lubricates oil environment to allow more abuse befoe it wears. None of this alters the fact that it is not designed to slip further than to provide smooth full engagement. It is certainly not designed as a variable ratio type 'gearbox' which multiplies torque on a full time basis. In essence the speed input should equal the speed output from a car clutch except momenterally when engaging. Aren't people taught not to abuse clutches any more?

really?
Huw
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On Mon, 13 Mar 2006 13:53:19 -0000, "Huw"

Yes, really. There is a warning to that effect on the unit.
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