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skyeg3
08-02-2013, 09:20 PM
Has anyone ever heard of a timing chain breaking on the T1N? My uncle has a NCV3 and his timing chain just broke. And because that engine is an interference engine ( the valves come in contact with the top of the Pistons if the timing chain breaks) it destroyed his engine and he had to buy a new one... For $17,000. ouch.

Does anyone know if the t1n has an 'interference' engine? Is replacing the timing chain something that would be smart, or overkill?

photogravity
08-03-2013, 12:48 AM
While I do not know for sure, I think that most diesel engines are of the design you mention. Diesel engines run at much higher compression rates than gasoline engines and it seems that dictates the cylinder and head design which causes interference between the two in the case of a catastrophic failure of the timing chain.

I am a fan of gear to gear setups, foillowed by chains and then belts. The old pushrod Volvo engines (B18, B20, B30 and probably others) had gear to gear drives between the crank and camshaft.

If I'm way off here about diesel engine design, someone correct me please.

EZoilburner
08-03-2013, 02:58 AM
I remember reading a post by Doktor Andy saying the chain on the t1n's should last for the life of the vehicle, or was it the engine. No need to put a new one in I believe, so many other things can go wrong before that, vibration damper and key, egr, injectors, black death, broken glow plugs come first to mind to name a few.

lindenengineering
08-04-2013, 12:06 AM
I remember reading a post by Doktor Andy saying the chain on the t1n's should last for the life of the vehicle, or was it the engine. No need to put a new one in I believe, so many other things can go wrong before that, vibration damper and key, egr, injectors, black death, broken glow plugs come first to mind to name a few.

Basically he is right!
That stated if the engine has suffered a failure where pistons have whacked valves then it should be replaced since it will have suffered some due shock/stress treatment due to the chain bending the valves; since it is connected to the crankshaft and the camshafts.

The clearance on most diesels are minimal hence they are almost always interference designs.
The Sprinter like many other engines uses a version of the toroidal cavity piston and cut out pockets are provided in the piston crown to accommodate the valve heads as they sit proud of the head face.
Here is a view of Sealed Power's Sprinter piston ans you can see the valve cutaways quite clearly.

If you are interested in piston design over the years, here is a good symposium on the subject

http://www.gruppofrattura.it/pdf/ext/MS&T/Vol.5%20No1/The%20piston.pdf
Good bedtime reading:laughing:
Dennis

jackbombay
08-04-2013, 05:24 AM
I don't know of any diesel engine that isn't an interference engine.

hkpierce
08-04-2013, 06:49 PM
I remember reading a post by Doktor Andy saying the chain on the t1n's should last for the life of the vehicle, or was it the engine. No need to put a new one in I believe, so many other things can go wrong before that, vibration damper and key, egr, injectors, black death, broken glow plugs come first to mind to name a few.


Source: http://sprinter-source.com/forum/showthread.php?p=222923&highlight=timing+chain#post222923

Boater
08-05-2013, 01:56 PM
I don't know if it applies to the NCV3 but I have heard of diesel cars where timing chain failure has been linked to how the tensioner works. For some reason the timing chain tensioner has oil pumped through it on these cars, and failure was traced to a blockage in the oil supply starving it of oil and causing it to seize.
I know my T1N engine does not have oil actively pumped into the tensioner, and the same appears true for the OM611 engine used in non-NAFTA T1Ns, so I'd say if your tensioner is just pre-loaded with oil and does not rely on a pumped supply, you can probably ignore any rumours of failures on other engines, the caveat being that I don't know whether the NCV3 tensioner is passive or pumped. Almost certainly this sort of thing will be specific to an engine series and I haven't read about a failure in T1N yet so wouldn't worry about it.

icarus
08-05-2013, 07:29 PM
I don't know of any diesel engine that isn't an interference engine.

Not to pick nits, but lots of older stationary diesels with compression release levers are non interference engines.

Icarus

jackbombay
08-05-2013, 10:29 PM
Not to pick nits, but lots of older stationary diesels with compression release levers are non interference engines.

Icarus

Interesting, I was thinking through the various automotive diesels I have knowledge of. A friend used to have an old bulldozer, it started on gasoline and ran till it was warmed up and then you switched it to diesel with a raise in the compression, I never got to check it out before he moved away though...

skyeg3
08-09-2013, 09:52 PM
It makes sense that diesels are interference engines with the compression and all. Thanks everybody..

ManWithDog
12-26-2016, 12:07 AM
oh God could you imagine buying a sprinter, having the chain break then having to spend another 17k? I would probably quit everything, leave everything and move to some island and eat fish for the rest of my life if that happened to me.

I'm looking at a t1n tomorrow with 220k miles. it is 1/3 of the price of your friends engine and that is a ton of money for me. If I buy it and it's a good van I'll be taking it fishing in south florida!! :tongue:

I always thought the t1n was gear driven for some reason. Now I know there is a timing chain does anyone know how often they should be changed or are they nothing to worry about as mentioned above?

Merry Christmas!!:smirk::smirk::smirk::smirk::smirk::smi rk::smirk::smirk::smirk::smirk::smirk::smirk::smir k::smirk::smirk::smirk::smirk::smirk::smirk::smirk ::smirk::smirk::smirk::smirk::smirk::smirk::smirk:

ManWithDog
12-26-2016, 03:25 AM
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Lotus54
12-26-2016, 04:59 AM
I have not seen the timing chain system on the T1N-'and I have not even looked at the Manuals to see how it is setup.

I did just do the chains on my 2000 VR6 Eurovan.
The problem on it was not really the chains, but the tensioners. Three of them were broken- the chain was starting to wear against the case. The hydraulic tensioner appeared just fine.
Poor design for extended longevity I think. It wouldn't be so bad, but it is a pain to R and R the transaxle to get to them.

lindenengineering
12-26-2016, 02:23 PM
Well I have just fixed one!
The timing half gear spokes sheered on the exhaust camshaft.
Really buggered it up!

The pistons clashed with the valves, bent all of 'em and busted five valve guides in the process of coming undone. The exhaust camshaft sheered off at the 1st lobe, and all that collision activity before it stopped reduced the valve train it to junk; tearing up the cam lifters in the process.

I took the engine down and checked the pistons for damage, rods for bend and twist but found nothing so I rebuilt it using some new guide rails, chains,and recovered the head by installing some new guides and a set of good used valves reworking the head. Then installed a complete used valve train from another used engine that had been severely overheated.

With all that stated the timing chain set up on these is traditional Mercedes and very reliable and this is the first time I have seen one really come apart in decades of working on MB engines.
Really if you were contemplating buying one this would be my last area of worry.
Dennis
Mechanic

ManWithDog
12-28-2016, 03:52 AM
Well I have just fixed one!
The timing half gear spokes sheered on the exhaust camshaft.
Really buggered it up!

The pistons clashed with the valves, bent all of 'em and busted five valve guides in the process of coming undone. The exhaust camshaft sheered off at the 1st lobe, and all that collision activity before it stopped reduced the valve train it to junk; tearing up the cam lifters in the process.

I took the engine down and checked the pistons for damage, rods for bend and twist but found nothing so I rebuilt it using some new guide rails, chains,and recovered the head by installing some new guides and a set of good used valves reworking the head. Then installed a complete used valve train from another used engine that had been severely overheated.

With all that stated the timing chain set up on these is traditional Mercedes and very reliable and this is the first time I have seen one really come apart in decades of working on MB engines.
Really if you were contemplating buying one this would be my last area of worry.
Dennis
Mechanic

Dennis i'm moving to Denver soon maybe I'll meet you. I am wondering what you charged to do all of that?

lindenengineering
12-28-2016, 04:46 AM
Dennis i'm moving to Denver soon maybe I'll meet you. I am wondering what you charged to do all of that?

That job was $6000 incl tax.
Dennis

owner
12-28-2016, 05:18 AM
What was the actual engine in the OP? Was it the v6 or om651?

lindenengineering
12-28-2016, 02:57 PM
Well in my posted case it was an OM647.
Dennis

wlauberds
07-10-2017, 10:46 PM
I have a 2006 Sprinter 2500 and the van died while driving down the hwy on the 4th. Had it towed to the closest trusted Sprinter repair location (luckily in Portland, OR, so there are a few to choose from).

Got a call from the shop today that the timing chain snapped and that the engine needs to be replaced. 8k for new engine and 3k for the install.

Van has 125k on it and has been babied, so this comes as a huge shock. Aside from replacing some hoses and other standard stuff, van has been a great runner. All fluids, filters, etc, replaced to a T.

Question for you all, any idea on what questions I should ask to see about rebuilding over replacement? At the cost I was quoted, putting in a new engine is likely out of the question.

Any advice on what route would be advised and what questions to ask the shop would be very greatly appreciated. Super bummed to have them happen. Van has been fantastic otherwise with lots of great trip my family has shared in it.

lindenengineering
07-11-2017, 03:01 AM
Well I did one similar recently at around $5000 but adding a lot of stuff that needed replacement other than just the engine repair , like water pump, accessory belt, tensioner etc that added another $1000 to the bill.
Still not a cheap job but better than 11 Grand.
Dennis

Patrick of M
07-11-2017, 07:24 AM
So why are the t-chains failing? Are the tensioner loosing it thus causing chain failure. My money is always on the tensioner in t-belt failure, but with t-chains...?

lindenengineering
07-11-2017, 02:00 PM
Well from my experiences, its the exhaust cam chain wheel spokes that fail, then the whole lot simply comes apart.
It can do some spectacular damage to the valve gear, but so far I have yet to see any rods or pistons badly damaged by valve contact and by everything doing the crunchies!
There was an earlier more reliable wheel available and used on earlier engines ( as mentioned by Andy B) but its not now available.

In any case its an isolated problem, but I confess the recent three I have dealt with have turned up in the last 9 months.
Dennis

Patrick of M
07-12-2017, 09:08 AM
Thanks for the info. Sad to hear the cam chain wheels can fail, seems a little lame.

NelsonSprinter
07-13-2017, 12:38 AM
Has anyone ever heard of a timing chain breaking on the T1N? My uncle has a NCV3 and his timing chain just broke. And because that engine is an interference engine ( the valves come in contact with the top of the Pistons if the timing chain breaks) it destroyed his engine and he had to buy a new one... For $17,000. ouch.

Does anyone know if the t1n has an 'interference' engine? Is replacing the timing chain something that would be smart, or overkill?

Is your Uncle's a 4cylinder 2.1L Diesel?

jackbombay
07-13-2017, 05:42 AM
There was an earlier more reliable wheel available and used on earlier engines ( as mentioned by Andy B) but its not now available.

Some time ago I had chatted with Andy, and I recalled that it was the OM647 that had the better exhaust cam sprocket on it, and the OM612 had a less stout sprocket on them. But that was 8 years ago and my memory could certainly be in error.

Or is it that the early OM612 sprockets different than the late OM612 sprockets?

wlauberds
07-17-2017, 09:49 PM
Getting additional info from the shop, who have been great to work with, it was the cam chain wheel spokes that failed. From what the mechanic can see, the chain is still in one piece, but he can see the worn out spokes on the cam wheel.

Still sorting out best route, but, every shop I have talked to advised against rebuilding and instead getting either a new engine, which is likely cost prohibitive or buying a remanufactured from a shop like sprinterengines.come or the like.

Bummer situation. No options have come in at under 8k unless I buy an engine off ebay for $3k with no idea on the history or warranty. No shop wants to rebuild and it seems like rolling the dice if the valve rods and cylinders are smashed up.

Thanks for the help and advice on the thread. Dennis (lindenengineering), your responses and initial posting were super helpful. Still need to figure next step, but your comments have been helpful.

Cheyenne
07-17-2017, 09:57 PM
How about getting the whole thing shipped to Dennis for a rebuild?

IIRC another forum member did it recently. Again IIRC the cost of shipping plus Dennis's bill came in less than a new engine local to where the van failed.

Keith.

Edit to add, From Dennis's recent post...

Well I did one similar recently at around $5000 but adding a lot of stuff that needed replacement other than just the engine repair , like water pump, accessory belt, tensioner etc that added another $1000 to the bill.
Still not a cheap job but better than 11 Grand.
Dennis

So if you could get it shipped for less than six grand then you're in the money!

Midwestdrifter
07-18-2017, 05:22 AM
Diesels tend to have shorter valves, and turbodiesels have smaller valve diameters on average. The piston dish volume and low operating RPM means that chain slippage does not always result in major engine damage like it does on Gasoline powerplants. If only the exhuast cam slipped you may even have less damage than you think.

In general a boroscope inspection through the injector holes will tell you right away if the damage is major. It won't take long either.

If the scope comes back clean. The head is probably salvagable, and the bottom end surely is.

Pull the head and check it at this point. It probably just needs new valves, seats, and guides, and maybe a bit of cleanup on the chamber. If you are really lucky the seats will be good, and and new valves and guides will get you fixed.

At that point its just the labor for Head R&R, new timing chain, and ancillaries. Most skilled shops could do that in less than 15 hours labor. I would not throw away the engine without at least giving it a look! If the shop doesn't have a source or machine shop they trust to work on your head/engine, you probably should just have it moved somewhere else.

Lotus54
07-18-2017, 05:28 AM
I had a chain come loose (Lotus twincam) at 7000 rpm. Bent all the valves (expensive big valves too)
Didn't hut the pistons, rods, seats or even guides.

Since the valves are often at angles, what I've seen a lot is the valve just bends, and that's it.
(Obviously everything should be checked)

lindenengineering
07-18-2017, 05:31 AM
For info just about all of them bust the valve guides when the valve bends.
MB does not supply guides --It a new head from them .
Uncle Dennis has guides !

In just about every case the bucket followers are crushed and the cams are broken into bits.
In any case I remove the pistons and check for land damage and rod bend.

The whole timing chain, sprockets and guides get tossed into the trash with the cam girdle cams and caps etc .
Take no prisoners !
Dennis

jackbombay
07-18-2017, 05:53 AM
Which engines have the fragile exhaust cam sprocket?

Aqua Puttana
07-18-2017, 12:15 PM
Properly replacing a Sprinter any diesel engine won't be cheap no matter how you cut it.

How about getting the whole thing shipped to Dennis for a rebuild?

...

So if you could get it shipped for less than six grand then you're in the money!
+1
Shipping deals can be found if not on a tight schedule.

And Colorado is nice a nice area to tour when you go to pick up your properly repaired Sprinter. :thumbup:

:cheers: vic

jackbombay
07-18-2017, 05:23 PM
Shipping deals can be found if not on a tight schedule.


My sprinter was recently shipped from Denver to Albany New York for $2500, that's just one price point, but it can give you an idea of what shipping costs might be.

wlauberds
07-24-2017, 11:48 PM
Looking at the numbers, shipping + rebuild is about the same as a remanufactured. Still an option on the table as I continue to weigh what we are going to do.

So far, no options under $8k seem to exist as no one locally (Portland OR) seems to be willing to rebuild the engine. Most only seem willing to put in a brand new engine from MB.

Thanks again for all your help.

@jackbombay, I don't know enough to call the situation to call this a fragile exhaust cam sprocket, but, my engine was the OM647.

wlauberds
08-20-2017, 05:01 AM
Howdy All,
I wanted to share some pics of what actually happened with the timing chain. The secondary cam sprocket snapped off and the timing chain slipped.

Here are some views of what is going on:
https://s3.amazonaws.com/rwgps/screenshots/5PChKdlq.png
https://s3.amazonaws.com/rwgps/screenshots/9ma6P8Oy.png
https://s3.amazonaws.com/rwgps/screenshots/UXkH1hNe.png

Has anyone seen this before?
94042

94043

94044

lindenengineering
08-20-2017, 03:05 PM
Howdy All,
I wanted to share some pics of what actually happened with the timing chain. The secondary cam sprocket snapped off and the timing chain slipped.

Here are some views of what is going on:
https://s3.amazonaws.com/rwgps/screenshots/5PChKdlq.png
https://s3.amazonaws.com/rwgps/screenshots/9ma6P8Oy.png
https://s3.amazonaws.com/rwgps/screenshots/UXkH1hNe.png

Has anyone seen this before?

Yes!
Dennis

traT3gic
02-10-2018, 12:51 AM
To add my tiny .02 to the discussion, my 7.3L Ford has planetary gears for timing - basically for life. The T1N on the hand has the chain with apparently cams being the weak points. So my question is can the engine be rebuilt in situ or does it need to come out of the van ? If rebuilt for the cam damage I am guessing there will be metal slurry in the bottom end and bits of crap everywhere at the top end, the head will have to be pulled and I would be looking at a solid 10-20hrs of commitment ?

lindenengineering
02-10-2018, 02:34 PM
To add my tiny .02 to the discussion, my 7.3L Ford has planetary gears for timing - basically for life. The T1N on the hand has the chain with apparently cams being the weak points. So my question is can the engine be rebuilt in situ or does it need to come out of the van ? If rebuilt for the cam damage I am guessing there will be metal slurry in the bottom end and bits of crap everywhere at the top end, the head will have to be pulled and I would be looking at a solid 10-20hrs of commitment ?

A clarification is needed here.
My apologies for being a bit pedantic but you would only find PLANETARY gears in the E4OD transmission (gearbox) attached to the back of that 7,3 engine !
An example :-
https://www.google.com/search?q=planetary+gear+set&rlz=1C1AVNC_enUS737US737&tbm=isch&source=iu&ictx=1&fir=EesKgbHCRz7slM%253A%252CJ_DgTqvUzuGjiM%252C_&usg=__K2ou5o_pzatxzhLvj1v5q7oOoxE%3D&sa=X&ved=0ahUKEwjdv_f4wJvZAhUo94MKHfajBwcQ9QEIiQEwDA#im grc=EesKgbHCRz7slM:

In fact for clarification the engine you mentioned does have a SPUR gear timing set to drive the camshaft and HPOP pump etc etc . Helical tooth form is prefered in this application.
https://www.google.com/search?q=spur+gear+timing+gears+set&rlz=1C1AVNC_enUS737US737&tbm=isch&source=iu&ictx=1&fir=JfCJ0JMVosac8M%253A%252CVN80iR95JqpYhM%252C_&usg=__P-jDN52EkXeOg0HPuBhj2BUIw4A%3D&sa=X&ved=0ahUKEwjKwbjawZvZAhXD4IMKHRDvAwkQ9QEILjAB#imgr c=JfCJ0JMVosac8M:

For information on engine architecture/design MB (like many manufacturers) prefer a timing chain for the application, simply because the engine is used in passenger cars and engine quietness is a strong consideration.
Conversely the 7,3 International Navistar engine was principally designed as a truck engine for medium duty truck applications like the IH 404. --404 is of course 400 CU Inches or 7,3 litre!
Ford of course adapted this engie for light duty PU applications where noise was less of a consideration.

As for the camshafts you mention that are weak!
Essentially they are not, but rather being a cast induction/ case hardened item, they fracture when impacted by sudden arrest! (Such as in a valve hitting a piston when the timing chain arr' lets go!) in short they are not very ductile as in most applications.
The weak area is in fact the spokes on the exhaust camshaft chain wheel which fracture/shatter in some cases.
The issue is not a prevalent one but more a weakness created by mass production and induction hardening processes is the cause.

It is preferable to tear down the engine which in any case dictates removal!
Why you might ask?
Principally metal fragments and swarf are dumped into the engine oil pan/sump.
The oil pan can be removed from the engine in situ but its much quicker to pull the engine as a complete powerpack for a clean out.
In any case the head will have to be removed and the piston crowns inspected for valve impact damage. In some cases the impact can be severe and this will damage the top ring land rendering the piston as scrap.
For that very reason alone, it is preferable to pull out the pistons and carefully inspect them for impact damage. Equally the rods checked for alignment when repairing this engine after such a failure.
As with most repairs be thorough for the best results.
Dennis

Patrick of M
02-10-2018, 03:32 PM
Thanks for the clarification re spur gear/planetary and how the mb sprocket is getting broken. Does beg the question how is a sudden stoppage happening if the sprocket is not the cause? Chain tensioner? Chain breakage?
On a completely tangential issue, my B18 Volvo engine, which was used in passenger cars, marine engines ( and tractors by the sound of it), uses spur gears to drive the cam. The noise (and long term reliability) was reduced by having the larger gear made of fibre. They still last over 500,000 miles in most cases, and mine looks fine at aprox 300 k miles. These old engines donít really care if the fiber gear fails, you can just pop on a new one . No interference back then.

Nautamaran
02-10-2018, 05:04 PM
In any mass-produced item there is the chance of production flaws, so likely the sprockets that break had flaws that were missed by MB quality control checks. A likely failure mechanism is metal fatigue on the spokes, as they flex slightly with each rotation. 3000 hrs @ 2000 rpm is 180 million cam cycles, and a minor flaw (such as weak spot around a casting inclusion) could grow into a crack and the spoke suddenly break. Sprocket wheel inspection is possibly preventative, but this is an uncommon failure and not worth pulling front covers off engines fleet wide, though you might get lucky and spot a cracking spoke by peering through the oil cap with a borescope?

-dave

lindenengineering
02-10-2018, 07:53 PM
Thanks for the clarification re spur gear/planetary and how the mb sprocket is getting broken. Does beg the question how is a sudden stoppage happening if the sprocket is not the cause? Chain tensioner? Chain breakage?
On a completely tangential issue, my B18 Volvo engine, which was used in passenger cars, marine engines ( and tractors by the sound of it), uses spur gears to drive the cam. The noise (and long term reliability) was reduced by having the larger gear made of fibre. They still last over 500,000 miles in most cases, and mine looks fine at aprox 300 k miles. These old engines donít really care if the fiber gear fails, you can just pop on a new one . No interference back then.

Yes !
To reduce the mesh noise, the fibre of the day was a material called phenolic resin.
Since some engines are designed for multi applications, fibre gear is used to reduce the noise in passenger car applications.
Back in the 70's the most famous one was the straight 6 Ford engine in E Series vans; notorious for tearing off the teeth on the half time idler pinion .
I suppose today the preferred material is delrin.
http://www.cncplastics.com/customgears.php
Dennis

Nautamaran
02-10-2018, 09:16 PM
Sailing hardware used the same fibre/resin sheets for pulley cases... today it’s been usurped by carbon fibre reinforced resins.
And there’s a LOT of delrin used in bearing rollers and linear bushings. Great material.

Lotus54
02-11-2018, 04:04 PM
On a completely tangential issue, my B18 Volvo engine, which was used in passenger cars, marine engines ( and tractors by the sound of it), uses spur gears to drive the cam. The noise (and long term reliability) was reduced by having the larger gear made of fibre. They still last over 500,000 miles in most cases, and mine looks fine at aprox 300 k miles. These old engines donít really care if the fiber gear fails, you can just pop on a new one . No interference back then.\

The B18 is a push rod engine, so can have just a drive and driven gear. Pretty simple and many, many pushrod engines have such a setup.
But with a tall, overhead cam engine such as the MB 5, it would require multiple gears to Ďget to the camí. Or a bevel gear setup could be used. Certainly it can be done, but would tend to be rather noisy and expensive. Typically, cam chains last a very long time. I have no idea how common the cam sprocket failure is on the MB, a higher quality item would make it much less likely Iím sure. But I would guess that it is relatively uncommon, or they would have changed it quite some time ago.
Of course, that is not necessarily true- but I would hope they would! It wouldnít require anything but better sprockets, no redesign of the rest or anything.

When I first saw your post, I was stopped at the Ďplanetaryí Gears. I was trying to figure how in the heck it would even work in a camshaft drive.

I tried to add a couple pics- but it wouldnít work.
Mark

Patrick of M
02-11-2018, 04:39 PM
\

The B18 is a push rod engine, so can have just a drive and driven gear. Pretty simple and many, many pushrod engines have such a setup.
But with a tall, overhead cam engine such as the MB 5, it would require multiple gears to ‘get to the cam’. Or a bevel gear setup could be used. Certainly it can be done, but would tend to be rather noisy and expensive. Typically, cam chains last a very long time. I have no idea how common the cam sprocket failure is on the MB, a higher quality item would make it much less likely I’m sure. But I would guess that it is relatively uncommon, or they would have changed it quite some time ago.
Of course, that is not necessarily true- but I would hope they would! It wouldn’t require anything but better sprockets, no redesign of the rest or anything.

When I first saw your post, I was stopped at the ‘planetary’ Gears. I was trying to figure how in the heck it would even work in a camshaft drive.

I tried to add a couple pics- but it wouldn’t work.
Mark
Google “image size” and download app for image sizing, or if you are on a laptop anything else that works. It is a bit of a pain, but the upside is : if the pic server you link to closes the forum loses content. If you resize image and then upload to forum, the forum always has the pics.
Re bevel gear to drive cam, the Ducati desmo has a variation on that theme.

Nautamaran
02-11-2018, 04:58 PM
I was trying to figure how in the heck it would even work in a camshaft drive.

It does give new meaning to the term ďrotary engineĒ... :lol:

Lotus54
02-12-2018, 03:26 AM
I guess I can't upload from the tablet.

Sample of a bevel drive (Ducati) and a Ford gear/shaft driven system
(for those that can't figure how the Ducati rockers- it is a Desmodronic system- meaning the valves are opened AND closed with rockers- not springs.

Nautamaran
02-12-2018, 03:56 AM
I guess I can't upload from the tablet.

Sample of a bevel drive (Ducati) and a Ford gear/shaft driven system
(for those that can't figure how the Ducati rockers- it is a Desmodronic system- meaning the valves are opened AND closed with rockers- not springs.

Gapping all the clearances on the Ducati engine must be a nightmare, but the Desmodronic valve train uses practically no power and eliminates valve float. I recall Ducati protesting when Honda supported a MotoGP move to limit 800cc engine speeds to (wait for it...) 19,000 RPM. :bow:

Lotus54
02-12-2018, 04:15 AM
Gapping all the clearances on the Ducati engine must be a nightmare, but the Desmodronic valve train uses practically no power and eliminates valve float. I recall Ducati protesting when Honda supported a MotoGP move to limit 800cc engine speeds to (wait for it...) 19,000 RPM. :bow:

Iíve had a number of Ducatis (still have one)- they are no big deal to set valves, and if set correctly, hold quite a long time. I like to set the closers to as close to zero lash as possible, with openers at minimum spec. Openers are super easy- closers are a bit trickier (since you need to make sure the valve doesnít drop into the cylinder!)


Mark

Nautamaran
02-12-2018, 04:29 AM
I was thinking more of dailing in the end-play on all those interconnected spur- and worm-drives during a rebuild. The cam followers would be a relative cake walk? Don’t misunderstand: I think it’s a truly elegant design.

Lotus54
02-12-2018, 04:40 AM
I was thinking more of dailing in the end-play on all those interconnected spur- and worm-drives during a rebuild. The cam followers would be a relative cake walk? Donít misunderstand: I think itís a truly elegant design.

I see- Iíve never done a bevel, just belt drive. From what I understand, those bevel drives on the Ducatis once set up stay very well. With no springs to work against, there is less wear (so I understand)

lindenengineering
02-12-2018, 06:42 PM
So what do you do if the engine is obsolete and NO parts are available for the timing gears?
Ref Wolsey Viper engine found in a Sopwith Camel /Spad fighter or Hispano Suiza car?
(The engine is designed by Hispano Suiza)

https://www.google.com/search?q=hispano+sauiza+engine+diagram&rlz=1C1OPRB_enUS575US577&oq=hispano+sauiza+engine+diagram&aqs=chrome..69i57.23771j1j8&sourceid=chrome&ie=UTF-8


Answer:-
In short make 'em
Dennis

jackbombay
02-13-2018, 04:14 AM
Looking at parts for the OM612 and the OM647 both of them have the same part number for the exhaust camshaft sprocket.

I believe the OM647 is the engine that has the sprocket that can sometimes fail, but I'm having a hard time confirming that.

lindenengineering
02-13-2018, 05:23 AM
Looking at parts for the OM612 and the OM647 both of them have the same part number for the exhaust camshaft sprocket.

I believe the OM647 is the engine that has the sprocket that can sometimes fail, but I'm having a hard time confirming that.

The "647" is prominent.
Dennis

Nautamaran
02-13-2018, 10:47 AM
Looking at parts for the OM612 and the OM647 both of them have the same part number for the exhaust camshaft sprocket.

I believe the OM647 is the engine that has the sprocket that can sometimes fail, but I'm having a hard time confirming that.

Given the 612 is a lengthened OM611, I wonder if the sprocket was designed for a 4-cylinder then carried into the 612 and 647 designs? 25% more cam to twist would consume some design margin and shorten fatigue life - assuming itís the same 611 part, though my money would still be on internal production flaws making it past quality checks?

AdrianD
02-14-2018, 07:22 AM
Don't forget about the OM613, which has one more cylinder and I suspect they use the same sprocket too.