YouTube R1200 WetHead DIY Cam Timing Tool

[alancoles]

Wouldn't surprise me if BMW pulled it so that folks have to go to the dealer. They have a long history of doing that sort of stuff with plenty of stuff and have been trying to shut out products like the GS911, etc.

Heck, you even need a tool (factory or GS911 or equivalent) to reset your maintenance reminder which could easily be user done through the existing bike electronics like it is on two of my cars!

 

[lirider]

I think if you can determine the force the factory tool applies you can definitely replicate that with a fixed rate spring of sufficient length in the pressure driven tensioner. Since we know the thread pitch, a certain number of turns once contact with the chain is made should do the trick.

 

[azgman]

I know the very similar tensioner tool for a Triumph 1215cc triple is set for 0.6NM. Surprisingly little force. I am not saying that the same force would be appropriate for a BMW but it is at least one known data point.

 

[SeattleRTrider]

I am impressed by the knowledge and the detailed research that Boxflyer has put into this project. I am equally impressed by those in this forum contributing to his on going work with questions and suggestions. From my perspective, this type of collaboration is rare and I'm anxious to see the results.

I do have a question based on some of the comments related to the interaction of the proposed tool with a timing chain that has stretched. It looks like the cam chain tension is defined by the upward force applied to lower the chain rail by the chain tensioner (the part, not the tool). As Boxflyer pointed out, the force from the chain tensioner is related to oil pressure when the engine is running. Since it looks like the force applied to the tensioning mechanics is directly related to oil pressure and independent of any other outside variable, does the length of the chain (based on stretching), play a role in this process?

As you can probably tell, I am not an engine mechanic so please don't be too harsh if this is a dumb question.

 

[lirider]

Since it looks like the force applied to the tensioning mechanics is directly related to oil pressure and independent of any other outside variable, does the length of the chain (based on stretching), play a role in this process?

I don't think it does. The piston in the tensioner just moves to take up that extra play but the force should be the same.

 

[Omega Man]

Could this "force" be mirrored and then duplicated with a torque wrench.....A click off at the prescribed tension with a bolt or Delrin spacer/bolt combination?
OM

 

[Boxflyer]

Hello Seattle...
Thanks for the kind words and contribution to this thread.

I think that the way cam chains today are engineered and constructed, that stretch is not a significant issue until an extended amount of use (maybe in excess of 150k miles). This is totally a guess, but there has to be some BMW engineering data that shows the merit of choosing this conventional roller chain for this application. I've seen that the new "ShiftCam" 1250 will feature a toothed link style chain vs the "WetHead" roller chain. Once again, speculation on my part is that with the greater mass of the intake cam extra lobes and associated "shift gate", that the older style single roller chain was just beyond its design limits for what's ahead. Lots of data shows less friction and better longevity with roller chains, but that is waaaaay beyond the scope of this discussion...and I HATE thread drift on forums!

As far as stretch is concerned, it has to exist, but even with the OEM tool, it doesn't really take that into account in a way that I can see. Ultimately, the critical length of chain to check/set the cam timing with, is the "top, pulled/tensioned" length under normal operation. With either the OEM tool or the DIY version I'm working on, it will be better able to compensate for some stretch by using a spring vs having a fixed length device that will only be accurate at one point of time in the life of our cam chain stretch. My first attempt at using a stick pen plastic body is just not going to work!

I'm using this website to work with some variables in the effort to use a coil spring in the OEM tensioner for the DIY solution.
https://www.acxesspring.com/spring-force-constant-calculator.html

For LiRider, I'm worried about having less than about 75% of the threads engaged on the OEM tensioner when the load approaches what I have measured at about 50 Nm on my torque wrench when the OEM tool clicks over. ( that's the force exerted from the tip of the tool against a torque wrench adaptor, not the turning force of any of the threaded parts)
With the copper crush washer removed to eliminate another variable, from the first thread to bite between the OEM tensioner and the cylinder casting, there is only 8.5mm of threaded body to achieve somewhere near the 50N of force. I've run my OEM tool and DIY tools in and out so may times, that I am now seeing some grey aluminum breakdown on my RH side threaded hole. I can only lube the threads with engine oil so as to keep it the same as what the end user will be doing when this is complete.
Thanks for the input, every little bit helps!

So, with the chain on the RH side of 102 elements, and the LH side with 106 elements, maybe only a little less than half of the chain is really going to affect the actual cam positions when the chain and sprocket wear do become a factor. Then there are the drive gears on the end of the cams which are not accounted for...blah, blah, blah...the theory of all this makes my head hurt!

SeattleRTrider: I'm in total agreement with you that this thread has maintained a tone of civility and collaboration that is terrible on other threads and forums.
If, like on this thread, anyone that wants to contribute and stay on point with the meat of the topic work together, we all benefit...if like so often happens, a few vocal members drive the topic off or just get downright rude, those that want to get something from the topic flee like spooked animals. Too bad we can't all behave like we were face to face in the same room and had to account for what we just throw out as either gospel or show as bad manners.
Enough of my rant and back to the technical discussion at hand...

 

[lkraus]

You are trying to replicate a force normally supplied by oil pressure. So, maybe some sort of piston driven by oil and pressurized by tightening a bolt, monitored with an oil pressure gauge? Modify a stock chain tensioner to change the oil source?

Getting a good deal more complicated than a piece of pen tube...

 

[alancoles]

You are trying to replicate a force normally supplied by oil pressure...

Larry, because the testing is done with the engine not running, I don't think there is any need to replicate an oil source (additional complication - oil pressure + spring tension) but rather simply replicate the pressure/force that the OE Tool generates with it's simple spring + 3-clicks.

 

[PGlaves]

I have a very simple question.

We are applying pressure against the chain follower to fully tighten the chain. So my question is why is the precise pressure so critical. It is a steel chain. Once all of the slack is removed that is it. It won't get any longer until there is more wear. So apply sufficient pressure to remove all slack but not so much to break anything and you are there.

Why overthink or over complicate this task just because some junior German intern engineering student did? What am I missing here? Why not use a spring sufficiently strong to make sure there is no slack but not strong enough to strip threads or break chains?

 

[Boxflyer]

Hi Paul,
That's what I'm doing with the latest version of this DIY tool.

One set of springs will be arriving today and another set of a different length and strength tomorrow.

It should be simple once the range of pressure required to tension the chain correctly is duplicated.

As soon as I get parts to work, I'll let everyone know...I feel bad that what I thought was a solution with some light weight plastic, was published before it was proven to be a flawed approach.

Thanks for your help with thinking this through.

 

[lirider]

I have a very simple question.

We are applying pressure against the chain follower to fully tighten the chain. So my question is why is the precise pressure so critical. It is a steel chain. Once all of the slack is removed that is it. It won't get any longer until there is more wear. So apply sufficient pressure to remove all slack but not so much to break anything and you are there.

Why overthink or over complicate this task just because some junior German intern engineering student did? What am I missing here? Why not use a spring sufficiently strong to make sure there is no slack but not strong enough to strip threads or break chains?

I think you're absolutely right here and I think that's what Boxflyer is shooting for. Close enough should be good enough.

 

[alancoles]

Paul, I believe the necessity to have a specific tension on the cam chain is that at that specific tension (the tension of the tool) the camshaft position measurements are valid for camshaft alignment. Anything less or more will change the position of the cams and not allow one to ensure that the two camshafts are properly aligned.

There are two (2) points where this is needed/desired. First is to verify that the cams are in proper alignment so that the engine runs as well as possible and that the valve clearance checks are meaningful. The second point where you would want to use the tool is if there is a need to remove the cams, to adjust the valves or any other reason.

 

[PGlaves]

Paul, I believe the necessity to have a specific tension on the cam chain is that at that specific tension (the tension of the tool) the camshaft position measurements are valid for camshaft alignment. Anything less or more will change the position of the cams and not allow one to ensure that the two camshafts are properly aligned.

There are two (2) points where this is needed/desired. First is to verify that the cams are in proper alignment so that the engine runs as well as possible and that the valve clearance checks are meaningful. The second point where you would want to use the tool is if there is a need to remove the cams, to adjust the valves or any other reason.

Why would this specific tension be less that all slack in the chain removed?

 

[Boxflyer]

I received 2 sets of different size/strength springs today.

Both sets come up a little weak on effort to push on the bottom side of the chain to allow correct fit of the alignment jig on the cams.

I expect one more spring tomorrow that I feel may be really workable after seeing how close I was today.

I'll post up my results as soon as I run back in the garage from the mail box and the COLD!

 

[azgman]

My guess on the OEM cam chain tensioner tool for cam alignment is, that it is attempting to replicate the force applied by the "normal" cam chain tensioner. The cam alignment should be correct for a running engine and that has a cam chain under the adjustment of the oil pressure based cam chain tensioner. Certainly, the cam chain tension in a running engine is not perfectly stable, so this must be an average value? Bottom line is Paul has made a good point about removing all of the slack and that being good enough to make the adjustment of cam alignment (phase). It would be great if we could hear from a BMW engineer, but that won't happen.

 

[PGlaves]

My guess on the OEM cam chain tensioner tool for cam alignment is, that it is attempting to replicate the force applied by the "normal" cam chain tensioner. The cam alignment should be correct for a running engine and that has a cam chain under the adjustment of the oil pressure based cam chain tensioner. Certainly, the cam chain tension in a running engine is not perfectly stable, so this must be an average value? Bottom line is Paul has made a good point about removing all of the slack and that being good enough to make the adjustment of cam alignment (phase). It would be great if we could hear from a BMW engineer, but that won't happen.

The tensioner is controlling the "back" side of the chain. The sprocket on the crankshaft is pulling the chain to turn the sprockets on the camshafts. I would surmise that there should not be any slack between the crank sprocket and the cam sprockets.

 

[Boxflyer]

Hi Paul, you are right...
There's a little more to it than just removing the slack though. There are wildly varying degrees of taking the slack out and putting the cam timing chain in a reference position.

The OEM running tensioner has a very light duty spring (about 7-8 lbs force) that is removing the slack when the engine is not running, and that is not very close to where the chain/cam position is when using the OEM tool to establish the tension to fit the cam alignment jig to set/adjust the cams.

If you calculate the full running oil pressure of 4.5 +/- .5 BAR (65.3 +/- 7.3 PSI) on the 13mm (.511 in) diameter piston, the working effort while running is about 13.4 pounds of compression force on the slack side cam chain follower.

I've measured the force generated by the OEM cam tensioning tool to be about 50 +/- 5 Nm (36.88 lbs) force on my torque wrench with an adaptor set at 90 deg at the "3 clicks" point.
Here's my crude attempt to measure the OEM tool:

I am totally guessing that what the original BMW engineers did was to set some specific data point to load up the cam chain to make sure it totally removes any cushion effects of various oils and wear in the sprockets and links, and whatever...I don't know what they were thinking...

Yesterday I got the 2 sets of springs as mentioned above, and they only exerted about 30 and 32 pounds of force when pushed to the installed compressed length using my "not so precision" bathroom scales.

The spring that arrived today is a "heavy load" version of the ones I tried yesterday. I was hopeful to find a working length of this spring when used in place of the OEM running spring, inside the OEM tensioner, that puts the same compression force on the slack side cam chain follower as the OEM tool. This "heavy load" gave a force of about 35 lbs at the installed length as measured with the bathroom scales.
I could install the OEM turning tool in the cam chain sprocket and give just a "calibrated" little extra pull on the tight side of the chain and the cam alignment jig fit fine.
Since this "heavy load" was not quite enough power to duplicate the effort from the OEM tool, I tried adding some small washers as shims making it push more, but started to "2 block" and get coil on coil which in essence makes it a fixed length tool again.

There is one more spring in the 10mmx70mm size I've been working with that is listed as "super heavy load". I'll order it and see how long it takes to get here from Hong Kong, but it's not like getting the others right from Amazon.

I'm sure some are wondering, so I'll put it out there, that I keep checking the proper alignment of my cams with the OEM tool so I don't make a false discovery that has more flawed R&D...

Anyway, this is just a hobby, and I'm just an enthusiast, so I'll keep making an effort to come up with a DIY tool that may help someone out.

 

[Boxflyer]

FINALLY!
I've published this YouTube Video again...this time with repeatable results.

https://www.youtube.com/watch?v=4Ts_LP-1rr0

 

[azgman]

Outstanding job!