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Why did camshaft bevel drive get replaced and why B-I-O?


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#1 mariner

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Posted 18 February 2024 - 10:51

Yesterday I went to a very British event, the VSCC Pomeroy Trophy. It is a handicap driving test competition designed to give old and new cars an even chance . 

 

Being the Vintage Sportscar Club there were several pre-1930 cars, the ones with OHC usually had bevel gear cam drives. I think the RR Merlin used bevel drive.

 

Bevels were replaced by chains then gear drives. Chains are noisy, stretch and need an oil tight box at the front of the engine. Bevel drives have separate oil boxes and no oil filled drive tower to leak. Gear drives don't stretch but setting up backlash is very tricky and harmonics can wreck them as Cosworth found with the DFV.

 

So why were bevel drives superseded, was it just less engine length or are two bevels sets plus a shaft more expensive than a chain plus two straight gears?

 

Then , of course Glas introduced the rubber belt drive with no oil and easy replacement – yes I know it is elastomer  not rubber but everybody says “rubber”

 

Having got back from the VSCC I was reading about the recent Ford B-I-O cam drive. B-I-O is "belt in oil" so Ford have replaced a simple rubber belt outside the wet engine area and accessible under a plastic cover with a rubber belt inside the wet engine and very inaccessible. The article was implying a lot of the Ford B-I-O engines have failed simply because the normal wear mode for a rubber drive belt is to shed rubber teeth particles which then go into the sump and neatly block oil filters etc.

 

 


Why is B-I-O better thana belt please?


Edited by mariner, 18 February 2024 - 11:26.


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#2 just me again

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Posted 18 February 2024 - 11:01

I believe the belt on Peugeot 1.0 - 1,2 3cyl. Engines also run in the oil. This has also caused problems with longevity!!!

#3 Sterzo

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Posted 18 February 2024 - 14:28

I have read that belt-in-oil reduces frictional losses (somewhere it said by 30%). It's also claimed to reduce carbon dioxide emissions; but whether that's as an effect of the reduced frictional losses or some other way I have no idea. The cynic in me wonders whether it's one of those things that performs better in official tests, but lacks much merit overall.



#4 Bloggsworth

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Posted 18 February 2024 - 17:11

Ask a 1 litre Ford EcoSport owner about the longevity of BIO... Oops! Ford just admitted to an expensive cock-up.


Edited by Bloggsworth, 18 February 2024 - 17:11.


#5 Greg Locock

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Posted 18 February 2024 - 19:52

One reason bevel drive would have disappeared eventually is noise. With a bevel drive, if you have a separate head /cam carrier, then you'd have to adjust the meshing of the bevels for each car to prevent chatter, and somehow allow for the expansion of the block as it warms up. They also add a bit to engine length which is critical for EW layouts and important for NS.



#6 desmo

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Posted 19 February 2024 - 15:23

Bevel drives must be expensive AF to make compared to simple belt (dry or wet) or chain drives.



#7 just me again

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Posted 19 February 2024 - 16:54

I have read that belt-in-oil reduces frictional losses (somewhere it said by 30%). It's also claimed to reduce carbon dioxide emissions; but whether that's as an effect of the reduced frictional losses or some other way I have no idea. The cynic in me wonders whether it's one of those things that performs better in official tests, but lacks much merit overall.


My guess would be that a 1,2 Peugeot is the most economical non Turbo car you an buy. So they are doing something right :-)

#8 GregThomas

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Posted 22 February 2024 - 08:35

One reason bevel drive would have disappeared eventually is noise. With a bevel drive, if you have a separate head /cam carrier, then you'd have to adjust the meshing of the bevels for each car to prevent chatter, and somehow allow for the expansion of the block as it warms up. They also add a bit to engine length which is critical for EW layouts and important for NS.

Having built more than my fair share of Ducati bevel OHC engines, I'll attest to the extra time/cost of setting up top and bottom bevels to close limits.

Certainly not what you'd want on a serious modern production line.

An Oldham coupling in the vertical shaft takes care of expansion concerns quite neatly.

 

Never struck a b i o setup but very familiar with both roller chain and Morse chain layouts. In my experience, a roller chain layout requires less in the way of guides and tensioners than a Morse. The heavier Morse at high revs wants to become a circle and has to be restrained by very stiff guides. Late twin cam motorcycle engines using Morse chain cam drives even have the short 100mm or so run between the cams restrained in this way. Needed when the operating revs can exceed 14,000rpm.



#9 Magoo

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Posted 22 February 2024 - 14:21

John Oldham's coupling with pop-country backing track. 

 

 

 



#10 Catalina Park

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Posted 23 February 2024 - 03:39

John Oldham's coupling with pop-country backing track. 

 

 

 

I can see why they dropped out of favour. That noise would drive me crazy.