27 replies to this topic

[mariner]

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So why were bevel drives superseded, was it just less engine length or are two bevels sets plus a shaft more expensive than a chain plus two straight gears?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

[just me again]

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

[Sterzo]

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.

[Bloggsworth]

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.

[Greg Locock]

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.

[desmo]

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

[just me again]

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 :-)

[GregThomas]

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.

[Magoo]

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

 

 

 

[Catalina Park]

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

 

 

 

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

[Dave W]

An external belt requires lip seals where the camshaft(s) pass from inside to outside.  Lip seals have a tiny but measureable amount of friction and wear in service.  Leaking seals are messy.  Moving the belt inside gets rid of some or all of the shaft pass-throughs.  There's also a tiny but measureable amount of belt and pulley wear from friction, which could theoretically be reduced by running in oil.

 

Theoretically a belt could be lighter, quieter, and cheaper than a chain, as well as having less potential for an oil leak.

 

Downsides: hot motor oil is a very harsh environment for "elastomer" belts, and if service is needed, the complexity and expense are then the same as an internal chain.

 

Early cars used gear trains or shafts with bevel or skew gears because gears were established technology with known service factors.  Roller chains were rare and often unreliable.  Roller chain was one of those things like ball-point pens, that looked simple, but took a very long time to get right.

[BRG]

Supposedly, most of the issues with the Ford Eco-Boost B-I-O system is people not using the correct specified oil.  Apparently, Ford dealers servicing your car will use the correct oil but private garages or home mechanics just bung in any old oil that is roughly right 

 

Or so Ford claim.

[mariner]

There is an excellent UK magazine called Car Mechanics which, these days, is aimed at independent repairers.

 A recent issue highlights some of the in service horrors of BIO engines , particularly Ford and Stellantis turbo three's

 

Apparently as the belt sheds bits they get everywhere, including into the filter of the oil driven brake booster. The EU supposedly forced areacall when peoples brakes stopped working a recall on some BIO engines!

 

 

Peugeot is recalling 2212 examples of its 2017-2020 Peugeot 308, 208 and 2008 due to an issue with the timing belt degrading. "The timing belt may degrade due to aged engine oil. If left unrepaired it may result in a reduction or a loss of braking performance," says the brand in its recall notice.May 30, 2023

[Wuzak]

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.

 

Wouldn't the bevel drive also be less efficient?

[Dave W]

*Theoretically* the belt is more efficient.  The bevel gears have sliding friction and the shafts require bearings, which take a tiny amount of power.

 

In practice, there are lots of variables, and it often comes down to "six of one, half a dozen of the other." 

 

The service life of shafts and bevel gears is "indefinite".  Same for gear trains and even Bentley or NSU style eccentric rods.  Belts and chains, not so much, and often expensively so.

[kikiturbo2]

There is an excellent UK magazine called Car Mechanics which, these days, is aimed at independent repairers.

 A recent issue highlights some of the in service horrors of BIO engines , particularly Ford and Stellantis turbo three's

 

Apparently as the belt sheds bits they get everywhere, including into the filter of the oil driven brake booster. The EU supposedly forced areacall when peoples brakes stopped working a recall on some BIO engines!

 

 

Peugeot is recalling 2212 examples of its 2017-2020 Peugeot 308, 208 and 2008 due to an issue with the timing belt degrading. "The timing belt may degrade due to aged engine oil. If left unrepaired it may result in a reduction or a loss of braking performance," says the brand in its recall notice.May 30, 2023

as an owner of BIO peugeot 208, and user of a company car with a 1 litre 3 pot from VW, I can say that extended service intervals are the single largest killer of these engines..

[7MGTEsup]

I think some of the real world problems stem from the compressed timing of manufactures durability schedules. They may put 150,000 miles on a vehicle but it's done in a short time period and the vehicles are always hot apart from the first start of the day. Now do those same 150,000 miles over 10 years with many thousends of cold starts and stunted warm up cycles. 

[Lee Nicolle]

In theory a bevel gear is effiient,, but as has been pointed out not nice to set up. And uses space.

Chains are archaic, stretch big time and thendamage are the quides. Morse chain? Sorry no. Normally used with nylon/ alloy gears which fail.  Roller chains, a double row roller chain is better. But still stretch. Will take high rpm where Morse chain does not.

Composite belts? If kept dry are very good as well as absorbing crankshaft or valve train harmonics. Wet belts? In theory should be ok but clearly are not. I too have heard the stories, very secondhand about oil. These engines are sewing machine engines so using sewing machine oil may be applicable.

From what I have seen of OEM dealers they use maybe 2 types of oil,, usually the cheapest brandname oil. And I have been in a lot of OEM workshops. 5W20 budget mineral oil MAY be ok in these new engines,, but not when they have done high kms. 

I also [again s/h] have heard these wet belts dont like synthetic oil, which I have used for 30 years.

I guess I am glad I am largely out of this now as I have got too old but for servicing my drive cars, and racecars, though have just renewed my dealers licence for one more year. With the lack of sales hardly worth it really.

[GregThomas]

The development of chains has continued quietly and largely unnoticed.

 

Single row roller chain is now available in varieties which can handle the final drive requirements of a drag bike - up to 500 RWHP.

Or the cam drive requirements of an engine doing 18,000RPM.

With good life expectancy in both cases

There are also double row roller cam drive chains now doing astronomical mileages in big diesels. .

Morse chain is also being used for cam drives in high RPM applications.

i  don't consider it ideal but guide and tensioner developments have made it reliable.

I've never seen a motorcycle morse application using anything but steel sprockets.

 

In both types a reliable self adjusting tensioner is essential.  

IMO the designers who use oil pressure activated tensioners are idiots.

Once a certain level of floating detrius happens in the engine oil, they stop working.

Once that happens,the damage cascades.

[NTSOS]

How about the worm cam drive as used by the Ford GAA?

 

https://www.thesherm...-gaa-data-page/

[GregThomas]

Appropriate for something doing less than 3000rpm.  I note there are still spiral bevels in the accessory drives.

 

IMO a complicated build but probably good for a long service life before attention.

[Lee Nicolle]

The development of chains has continued quietly and largely unnoticed.

 

Single row roller chain is now available in varieties which can handle the final drive requirements of a drag bike - up to 500 RWHP.

Or the cam drive requirements of an engine doing 18,000RPM.

With good life expectancy in both cases

There are also double row roller cam drive chains now doing astronomical mileages in big diesels. .

Morse chain is also being used for cam drives in high RPM applications.

i  don't consider it ideal but guide and tensioner developments have made it reliable.

I've never seen a motorcycle morse application using anything but steel sprockets.

 

In both types a reliable self adjusting tensioner is essential.  

IMO the designers who use oil pressure activated tensioners are idiots.

Once a certain level of floating detrius happens in the engine oil, they stop working.

Once that happens,the damage cascades.

Big diesels at max 3500rpm with fairly light valve springs are eons away from a performance engine running at at least 7000 rpm.

I just watched a 2019 5.3 Chev stripped,, single row chain. Bean counters at work!!  A double row true roller chain has very little wear issues though ofcourse they stretch. As do belts and every other style of indirect connection. Gears still work well and are direct. Straight cut are noisy but reliable, helical cut  not quite as much. More so because noone manufactures them right now. As a HQ Racing engine sealer the alloy cam gear would walk forward on the steel hex until restrained by the timing cover,, cam is at least 4 deg wrong then and if left just eats the gears off. And wears a hole in the timing cover!! I have seen both!And these are mildly modded engines absolutely flat out a 6 grand and fairly soft valve springs. Decades ago you would buy a 44AL Repco set and they lasted forever. Change the cam and press the gear off and then on the new one. Never had an issue though not making the power of the engines if today. These days whoever makes them do not do a very good job

Many years ago they allowed straight cuts. And I have found with those poor cutting so no symetrical with each other,, 6 thou clearance one side, half a turn and none. The disadvantage of straight cut however, worse than helical is the cam harmonics are transferred to the crank. Chains do it as well, probably not quite so bad though the chain itself will set up a harmonic of its own. This is where external belts are probably the best.

As for seals? Eventually you have to have a seal both ends of the engine. Doesnt matter if it is before or after the belt. So dry belts make more sense. Replacing timing cover seals these days is more common that the past on all brands of engine. Rear seals as well though generally a bit easier these days than the old rope seals. Just a plate that bolts on the back of the block with a lip seal. Some engines just have it cast in the back. So remove tranny remove flywheel, then dig out the old one and install a new one.

[gruntguru]

 . . .A double row true roller chain has very little wear issues though of course they stretch. . . 

 

Although of course "stretch" in a roller chain is actually wear in the hinges.

[Magoo]

On GM LS V8s, the LS2 timing chain is the ticket. It's single-row but with heavier side plates and pins. 

[Magoo]

The development of chains has continued quietly and largely unnoticed.

 

Single row roller chain is now available in varieties which can handle the final drive requirements of a drag bike - up to 500 RWHP.

Or the cam drive requirements of an engine doing 18,000RPM.

With good life expectancy in both cases

There are also double row roller cam drive chains now doing astronomical mileages in big diesels. .

Morse chain is also being used for cam drives in high RPM applications.

i  don't consider it ideal but guide and tensioner developments have made it reliable.

I've never seen a motorcycle morse application using anything but steel sprockets.

 

In both types a reliable self adjusting tensioner is essential.  

IMO the designers who use oil pressure activated tensioners are idiots.

Once a certain level of floating detrius happens in the engine oil, they stop working.

Once that happens,the damage cascades.

 

Thanks. The inestimable Bill "Grumpy" Jenkins RIP was a proponent of the Morse aka link-belt silent chain for his Chevrolet V8s in drag racing, which did pretty well. In other words, the stock production part. He believed it was easier on the crankshaft, camshaft, and valvetrain. 

 

In the normally aspirated pushrod V8s in NASCAR, NHRA etc these days, toothed rubber belts are pretty much the universal choice. Even quieter. 

[Magoo]

 

In both types a reliable self adjusting tensioner is essential.  

IMO the designers who use oil pressure activated tensioners are idiots.

Once a certain level of floating detrius happens in the engine oil, they stop working.

Once that happens,the damage cascades.

 

 

Indeed. Also, oil debris in the cam phasers. JFC. I don't know about elsewhere, but in the USA it's an epidemic. 

Edited by Magoo, 01 February 2025 - 12:12.

[PJGD]

You would think that the effect of dirty oil on your whizzo mechanism would be an easy thing for the development engineers to test for and resolve  —  but apparently not.

[Magoo]

You would think that the effect of dirty oil on your whizzo mechanism would be an easy thing for the development engineers to test for and resolve  —  but apparently not.

 

One would think.