Acceptable wear on chain tensioner

I don't have the answer but I would change it ... no matter what.

 

Are those groves factory or a sign of the wear? I have seen chain tensioners come new with groves like this.

 

Rule of thumb I have used is if the grooves are smooth and shallow they are fairly harmless. If the is any sign of the material crumbling and 'chunking out' it is on its last legs. The wear rate at that point is exponential, not linier. This applies to both the rubber and plastic rubbing blocks. Ferrari's newest offering for the oil chain tensioner appears to be quite nicely made and should last a good long time.

When in there... make positive the bearing behind the drive gear is updated to the ball bearing and not the roller bearing and the fences on all of the gears are secure with no dings. I posted a photo of the process we came up with a while back for welding the fences as per the new 360 design and re plating the gears to FAA spec. Those fences cause a LOT of damage when they go walkin...

The chain drive tensioner pads are supposed to be to me by Wednesday this coming week. I sent my prototype to a new machine shop I was turned on to by a good friend. This shop specializes in aircraft restoration parts, is ISO rated and is owned by a Vintage Racer who I wanted to debate my design with. I gained a very high respect for these folks as it was quite clear they know what they are doing and were interested in the project based on our discussion. We agreed the design had 3 levels of fail safe redundancy over the OE design and I turned them loose on making me 32 of them. One will be tested to destruction, one will fix the engine that is currently apart waiting on them, two for my IMSA race engines and the rest available in kit form with templates to assemble them.
I have updated my test jig with a new motor (circuit breaker blew after many hours on the old one) so I should be ready to test them as soon as they come in. My plan is to run it both dry and wet, hot and cold under twice the expected load and see what happens after 10 hrs. just short of a simulated 7K RPM. I have enough research into the material spec's that I am confident nothing better is currently available on the market....based on the price it must be so! The newest GP bikes and many of the high end auto makers are now using this material in their new models coming out.

Having two trusted machine shops will now reduce the wait time of going from prototype to product... something I have been after for many years now. One of the machinists in my new shop has mold making experience so this should speed up the in tank fuel system rubber component's a good bit. Next week we start on the remainder of the cooling system hose tooling for the later cars... and then we take a break.

 

Dave, you are THE man!

Enjoy your time off, you certainly deserve it

 

Just a note about chain tensioners. When the head gasket went out on my VW Corrado V6 at less than 70,000 miles (grrrrrrr), my mechanic friend called me and said "You should come over and look at this". The chain tensioner had worn all the way through the plastic material and the chain was riding on the metal shoe! In addition, the valve guides were worn out. Not a long-lasting engine, apparently.

 

I dunno, Dave, this one out of my 36k spare could probably be fixed with some epoxy and bondo, don'cha think? Or should I just put it back in and let it eat?

Or maybe you should put me down for one of the new ones for when I do my belt service....
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Mine is shown below.

I used Gorilla Glue to build up the base of it, then after sanding it down flush, I used some Thompson's Water Seal to make it impervious to the elements.
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Photo's can tell so much...

Chains loose enough to jump links on start up, high levels of acid build up in the oil....

Both Virgin, run what ya brung.

 

Testing with a few drops of oil an hour. A new use for the cheap 348 idler bearings
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Nice test rig

 

Wow. Talk about timely. And me due for service next month!

 

Well put me down for one when testing is done, and they are for sale.

 

Of course I grabbed the chain that came out of a Daytona... the only that was damaged very bad due to some meat head only getting one row of the chain on the drive gear, not both, and running it that way for 18 years. This chain (and the gears in that engine) were worn at a terrible angle due to this misalignment and raised burs on one side of the center link rows. It is these burs that cut the one groove in the plastic rubbing block in the one area....

Six hours + run time, 4-6 drops of oil once an hour (really all I was trying to do is save my spare 348 drive gear, driving this whole mess and not run that dry), as high an RPM as my mill would go and enough tension on the chain to destroy a new 348 idler bearing, wearing deep grooves in the steel roller of that, ATF (running about 5wt) used for oil

The one slice in the plastic is explainable by the photo's of the chain. The other wear areas of the plastic faired a whole lot better than the steel roller and shows stains but little to no wear...... the idler bearing got hot enough to start throwing grease... upward, I havent looked at the bottom where gravity assisted. This means surely the plastic was plenty hot with no real lubrication for the run time indicated.

Any other tests needed? Considering it will be highly lubricated with engine oil when in real use... I am really liking these new plastics!

I sent the photo's to my design debate crew and have heard back from a few, now for the REAL tough crowd...
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Very impressive...

 

Seems it must be AT LEAST as good as OEM. As long as the material has the same strength and physical properties at running oil temps, I'd install it! Thanks Dave for working on these solutions!!

 

Part of my research was an attempt to identify what was used originally and set that as a baseline to improve upon. Too many variables to state anything as fact but... the plastic version was better than the rubber version. This is the latest and greatest improvement on the best plastic commercially available, designed specificly for this application, priced to reflect that status and I have not even found it available in the states yet, my expensive little sheet came from Europe.

Base tensile UP 2000-2500 PSI
Melt point UP 150 F
Deflection UP 50F

It was designed specificly to retain all of the properties while bathed in 'old' engine oil, one of the areas of improvement focused on in its construction. The carbon and acids in old oil must react negatively to plastics in some way.... beyond my grasp. This is the material that was used when plastic lined, steel body chain guides on the German marques were converted entirely to plastic construction for the new cars. Its good, but not good enough for me to trust mounting it in a dovetail fashion like Ferrari did on a series of these, they didnt stay with that design for long for obvious reasons. I decided to do a mechanical attachment to address that failure mode so the wear block is a future replaceable component. This attachment design required me to make a very accurate jig to be supplied with the pad so the attachment of the pad to the backing plate can be done consistantly.

Hell, I dunno..... Its the best I can come up with and I am going with it. Based on how it held up compared to the steel roller in my dry run test I figure if its good enough for the new Panzer's, it should do fairly well in the Red Cars. Upside to this effort is I finally have a material I trust to make the chain guides and wear plates in the Vintage engines, something I have been lacking for years now.

 

Excellent work Dave....from everything I know of the plastic you are using it is far superior to the OEM construction.

I also like the way you are intending to fasten the plastic.

 

C'mon Bruce, admit it - you like the fact that the material came from Panzers!!!

 

Bummer, we just replaced mine four months ago...

 

The military hardware given by Germany to Italy in WWII was tried and proven battle ready....when the Italians did maintenance and repair to the German equipment..well well well, it either fell out of the sky or couldn't even roll out of the shop under its own power.

Panzer engineering? Well, in this case it's like comparing space age to stone age. Wonder when Ferrari is going to cure its sticky interior plastic...then they may move forward and upgrade the plastic used in the engine...lol

 

OMG Plugzit thinking of using "good parts"? Has he!! frozen over? Dave you have influenced that hillbilly in a good way. Cheers guys...back to making airjacks for my racecar....

 

If my spit, bondo and epoxy fix on my old one works, I'll return the new one....
Instead of airjacks, why not use a skyhook?

 

I wish I had time to run it in the 348 IMSA car for a season prior to letting it out to cars outside of my own. I think I have covered all of the variables, the reason I have a design debate crew... have as many pairs of eyes as possible trying to find fault with a design while its still on the bench.

I have researched the plastic to death, am quite satisfied with the attachment procedure, find the test results to be quite satisfactory and am very pleased with the jig we made for setting it all up. I cant think of anything else we can do to improve it beyond what it is now. At this point its all up to the plastic and I have a paper trail on that.


"""When do you think these will be available for sale? Have you decided what the price will be? """
Late next week I should have the first batch done. I had 2 test mules made for final fitment checks and destruction tests and I am very pleased with those and intend to sign off on them Monday. Mid $300 range I suspect. Using round numbers when estimating costs and the projected volume required, it will be somewhere in that range if I am ever to see a payback on the materials alone.