Crank and camshafts

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Sun 7 May 2023 23:13
Crank and camshafts - Adampr

Just reading the thread on the astra with a shaky dephaser and a thought occurred to me. Normally when I have thoughts late at night they're stupid, so I'm bracing myself...

Why bother with cambelts and chains at all? Why not just have a geared connection between the top and bottom ends?

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Sun 7 May 2023 23:43
Crank and camshafts - elekie&a/c doctor

The main issue is noise. Listen to the Vag 2.5 diesel engine as fitted to the T5 transporter and Touareg . They will wake the dead.

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Sun 7 May 2023 23:59
Crank and camshafts - Big John

The Ford Essex V6 engine had geared connection between crank and camshaft (not ohc) but the cam gear was made of a sacrificial fibre material to ensure it wore before the cog integrated into the crankshaft. Net result - they failed in the same way as a cambelt - fortunately the valves / pistons didn't collide.

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Mon 8 May 2023 00:28
Crank and camshafts - edlithgow
It’s done. At least 1 of the classic Volvo’s has that IIRC (Volvo 140?). I suppose the main reason it’s not done more often is that they can get away with not doing it. IOW the punter does not know or care enough to refuse to buy rubber band autodestructing engines, which are cheaper and quieter, give more design flexibility, yadda yadda

The once common pushrod engines minimized the cam chain by putting the cam.down next to the crankshaft, and I would expect there were more gear driven examples in that configuration, though I don’t know this for a fact. However, pushrods mean you have more bits,more inertia, cost, yadda yadda. Surprised they lasted so long. Still a thing in the US. Maybe more historical consumer resistance to rubber band autodestructing engines there

Edited by edlithgow on 08/05/2023 at 00:45

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Mon 8 May 2023 08:27
Crank and camshafts - Surreydriver

Apart from noise, the main issue is cost. Geared drive to the camshafts obviously takes more precision parts, more time to assemble and a more complex engine block. Keeping it quiet also requires more complexity ( Honda (say) with spring loaded gears ).

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Mon 8 May 2023 09:02
Crank and camshafts - craig-pd130

Apart from noise, the main issue is cost. Geared drive to the camshafts obviously takes more precision parts, more time to assemble and a more complex engine block. Keeping it quiet also requires more complexity ( Honda (say) with spring loaded gears ).

Exactly this. Honda's motorbike division dropped a major clanger in the 1980s when it introduced a range of V4 engines, led by the VF750. Unfortunately, the engines were not tested for long enough in real-world conditions.

Owners quickly found that the camchain tensioning system was inadequate and the cams themselves wore out, often within a year of purchase. Both problems would kill engines. Several updated parts were specified but they were only partial fixes. The warranty costs were crippling in the critical US, UK and German markets.

Honda redesigned the engine and gave it gear-driven camshafts, and that version was ultra-reliable and largely saved the reputation of the company's bike division. But it later reverted to chain-driven cams again, for cost reasons

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Sun 11 Jun 2023 04:22
Crank and camshafts - movilogo

If engine is non interference type then belt failure is not catastrophic.

Though it will not be a nice situation when driving at speed.

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Mon 8 May 2023 08:32
Crank and camshafts - badbusdriver

While it is not comparable to a "normal" road car, Swedish supercar maker Koenigsegg do use a camless design for the ICE engine used in the Gemera (hybrid). It uses pneumatic actuators to open and close each valve independently.

Koenigsegg_TFG

Not sure if this is the kind of tech which may filter down into normal cars, but with EV domination not far away, maybe not worth bothering about.

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Mon 8 May 2023 09:07
Crank and camshafts - bathtub tom

pneumatic actuators to open and close each valve independently.

Didn't F1 engines toy with that technology?

I've seen shaft drive OHC on motorbikes and I believe Ferrari use gears.

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Mon 8 May 2023 11:50
Crank and camshafts - edlithgow

www.volvoclub.org.uk/prof_140.shtml

"The engines are unusual in that, instead of the more conventional timing chain to operate the camshaft, gears are used. A steel one is fitted to the crankshaft and a ‘Tufnol' (fibre) one to the camshaft. After a while. backlash occurs between the gear teeth and there is a resultant 'tappety-sounding' knock from this area. Only a replacement gear kit will rectify this. An 'all steel' kit is available for competition or general use if you don't mind the 'whine'! - I think it was standard on the 164's."

Pushrod engine though, so camshaft and crankshaft close together and noise possibly damped by being down in the sump.

Edited by edlithgow on 08/05/2023 at 11:53

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Sun 11 Jun 2023 03:48
Crank and camshafts - edlithgow

Air cooled Corvair seems to be a direct gear. Looks a nice engine.

www.youtube.com/watch?v=LJyKVWu_mhM

Closer to Brexitistan, always fancied a VW Variant estate, tho dunno offhand if the cam drive is done the same way

Edited by edlithgow on 11/06/2023 at 03:50

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Mon 8 May 2023 10:41
Crank and camshafts - John F

Pre-war Bugattis had shaft driven camshafts. The legendary Porsche 917 flat (boxer)12 engine's camshafts were driven by gears. Belts and chains are cheaper, quieter and lighter. They are also now sufficiently durable as long as they are made using top quality modern materials.

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Mon 8 May 2023 11:59
Crank and camshafts - Xileno

Before they went bust Rover were working on a version of the K series with no cam. I think it used electronically controlled actuators on the valves. Possibly too risky - any electrical malfunction and smashed valves might result.

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Tue 9 May 2023 03:55
Crank and camshafts - edlithgow

Before they went bust Rover were working on a version of the K series with no cam. I think it used electronically controlled actuators on the valves. Possibly too risky - any electrical malfunction and smashed valves might result.

Sounds like something to only consider on a non-interference engine, which don't seem to be very common.

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Tue 9 May 2023 06:54
Crank and camshafts - Falkirk Bairn

I have had some 50+cars in my life.

The only one I know off that was non-interference engine was my Mazda Xedos - in my 15 years of ownership no real repairs needed on the car - cambelts changed 2x.

What killed it was, like many Mazdas, rust in the rear suspension. In the past Mazda paid huge attention to the mechanicals & electricals but failed, for many years, on the rust. The inattention to rust probably due to there being no rust issues in Japan as they do not salt their roads.

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Tue 9 May 2023 09:25
Crank and camshafts - Andrew-T

What killed it was, like many Mazdas, rust in the rear suspension. In the past Mazda paid huge attention to the mechanicals & electricals but failed, for many years, on the rust. The inattention to rust probably due to there being no rust issues in Japan as they do not salt their roads.

Japan does have a fair bit of coastline, to say nothing of the occasional typhoon, so some salt must get around ?

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Sun 11 Jun 2023 16:21
Crank and camshafts - galileo

I have had some 50+cars in my life.

The only one I know off that was non-interference engine was my Mazda Xedos - in my 15 years of ownership no real repairs needed on the car - cambelts changed 2x.

I had a Rover 216 with the Honda engine: the cambelt broke but there was no damage at all, ran perfectly with a new (correctly timed)belt)

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Tue 9 May 2023 03:58
Crank and camshafts - edlithgow

Pre-war Bugattis had shaft driven camshafts. The legendary Porsche 917 flat (boxer)12 engine's camshafts were driven by gears. Belts and chains are cheaper, quieter and lighter. They are also now sufficiently durable as long as they are made using top quality modern materials.

If you still have to change them every 6 years (or, in fact, at all) they are not "sufficiently durable" for me.

According to the CB20 manual they are not "sufficiently durable" to be folded double, which is what the motor factors here do to them in storage, so the replacements are "pre-aged" to an unknown extent.

IOW they are not "sufficiently durable" to be worth a damn, or the trouble.

Edited by edlithgow on 09/05/2023 at 04:05

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Wed 10 May 2023 15:49
Crank and camshafts - Steveieb

Did anyone incorporate electro magnetic valve operation like the injector arrangement on my PD VAG engine ?

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Thu 18 May 2023 00:43
Crank and camshafts - edlithgow
Not even on my very long “to do” list.

As mentioned above, risky on an interference engine.
But I suppose if IC engines had a future, and manufacturers were looking for yet more new ways. To make them less reliable, that might be next.

As it is BIO is perhaps The Final F******
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