VWDiesel.net The IDI, TDI, and mTDI source.
General Information => FAQ/Tech Tips/Please Read First => Topic started by: lord_verminaard on April 17, 2008, 09:19:40 am
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Figured I would post this here, as apparently this is a common problem with 16v engines that get a serpentine conversion. This guy has made a jig so you can drill into the crank nose and press in hardened dowel pins to prevent the keyway from shearing off. Before, this fix required pulling the engine and crank and having a machine shop do the work.
http://forums.vwvortex.com/zeropost?cmd=tshow&id=3793002
Enjoy! Rob, (the guy who posted the thread) has done a lot of various fabricating for the Scirocco crowd and he really knows his stuff.
Brendan
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I also have a little more detailed explanation written up in this thread here:
http://forums.vwvortex.com/zerothread?id=3409003
Here are some pictures of the jig just being used on the cog/sprocket:
(http://www.mrequivocal.com/vw/Img_0465.jpg)
(http://www.mrequivocal.com/vw/drilledout2.jpg)
(http://www.mrequivocal.com/vw/drilledout.jpg)
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Man what I wouldnt give to have a serp system on my car.. :(
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Exciting business this is. Not only does it work in theory it works in practice as well. I'm quite pleased I didn't have to take this thing out to put it in a mill.
Here are some pictures (again, they can be found on the link(s) provided above):
(http://www.mrequivocal.com/vw/boltedon.jpg)
(http://www.mrequivocal.com/vw/boltedon2.jpg)
(http://www.mrequivocal.com/vw/boltedon3.jpg)
(http://www.mrequivocal.com/vw/drilling.jpg)
(http://www.mrequivocal.com/vw/onedrilled.jpg)
(http://www.mrequivocal.com/vw/twodrilled.jpg)
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complete success.
(http://www.mrequivocal.com/vw/fourdrilled.jpg)
(http://www.mrequivocal.com/vw/cogdrilled.jpg)
(http://www.mrequivocal.com/vw/cogdrilledwithbolt.jpg)
(http://www.mrequivocal.com/vw/cogdrilledbolted.jpg)
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and those 4 holes won't weaken the crank nose too much??? looks really interesting... that thing isn't going anywhere!! :lol:
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and those 4 holes won't weaken the crank nose too much??? looks really interesting... that thing isn't going anywhere!! :lol:
The holes are 5mm deep and the material for the crank is one hell of a lot harder than the cog. Thats less than 1/4" deep. Now I can't say this for sure because obviously I haven't driven it around yet but my educated guess is it will be just fine. The thread for the crank nose starts at about 7mm into the crank. So as far as that goes it shouldn't weaken the mounting.
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I did a similar repair, but with just two holes. As long as the key can't start moving due to the pins it should be fine. Four holes looks like overkill to me.
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I did a similar repair, but with just two holes. As long as the key can't start moving due to the pins it should be fine. Four holes looks like overkill to me.
I thought that originally too...but then I read other people's stories. First they tried one, then two. Finally by the third it seemed to be OK. There is a LOT of force that causes them shear in the first place - because on the one hand you have the crank bolt which is supposed to be around 77ft/lbs + 1/4 turn and THEN you have the 7mm key. It takes a lot of force to shift the cog and shear off the key.
And I do agree with you partly. The cog must not be permitted to move even a little. I don't know if you've ever tried it but on a clean nose and new cog, there is very very little movement maybe one quarter of one degree. Unfortunately that is why we're here. Even that little amount of movement could not overcome those forces I mentioned earlier. The idea behind using 4 pins is pretty simple really. Take equal loads across the geometric span of the cog - not in one or two places.
Though we'll see. Believe me I don't want to be proven wrong here, not because of my ego - but because I just rebuilt everything and another failure would mean 3 cylinder heads. :roll:
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I did a similar repair, but with just two holes. As long as the key can't start moving due to the pins it should be fine. Four holes looks like overkill to me.
I thought that originally too...but then I read other people's stories. First they tried one, then two. Finally by the third it seemed to be OK. There is a LOT of force that causes them shear in the first place - because on the one hand you have the crank bolt which is supposed to be around 77ft/lbs + 1/4 turn and THEN you have the 7mm key. It takes a lot of force to shift the cog and shear off the key.
And I do agree with you partly. The cog must not be permitted to move even a little. I don't know if you've ever tried it but on a clean nose and new cog, there is very very little movement maybe one quarter of one degree. Unfortunately that is why we're here. Even that little amount of movement could not overcome those forces I mentioned earlier. The idea behind using 4 pins is pretty simple really. Take equal loads across the geometric span of the cog - not in one or two places.
Though we'll see. Believe me I don't want to be proven wrong here, not because of my ego - but because I just rebuilt everything and another failure would mean 3 cylinder heads. :roll:
well vw over engineers their engines for a reason. i think there is no way you're going to bust this off, unless the crank bolt somehow loosens itself completely, and then falls out, and even then i have a hard time seeing this setup fail due to the belt tensioning, unless the pins are loose enough.
good work! keep the diy coming :) its what owning a vw is all about 8)
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The other thing to look at is making sure the end of the crank is perfectly flat to mate with the gear when it's bolted down tight. My dad's been noticing some of them aren't exactly flat, which might cause more wobble, especially if a less than perfect torquing procedure is used on a new bolt.
If you're going to this much trouble, and you're that risk adverse I would have thought you'd pull the crank and machine a TDI shaped D on the end of the crank nose matched to a gear to a light press fit.
Do keep up posted as to how the fix works though, I'm curious.
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The other thing to look at is making sure the end of the crank is perfectly flat to mate with the gear when it's bolted down tight. My dad's been noticing some of them aren't exactly flat, which might cause more wobble, especially if a less than perfect torquing procedure is used on a new bolt.
If you're going to this much trouble, and you're that risk adverse I would have thought you'd pull the crank and machine a TDI shaped D on the end of the crank nose matched to a gear to a light press fit.
Do keep up posted as to how the fix works though, I'm curious.
Well the problem is I can't. The TDI (and the like) use a different style belt that isn't compatible with the 16V and it wouldn't have been as cost effective to do that either. Sadly I can only design, I don't have the tooling to manufacture so it required dinero $$$.
...I thought of a better way of approaching the issue. Part two of the solution as a whole really. The second part being a lighter "harmonic balancer" thankfully those DO exist in forms compatible with the 16V. This setup is approximately 51% lighter than the stock pulley. Since I'm not running anything but the stock load (electrically speaking), and I have no P/S and/or AC, the diameter of the pulley "harmonic balancer" shouldn't matter as much as it would in say those systems.
I posted some pictures on VWVortex which I'll just include in this thread here:
(http://www.mrequivocal.com/vw/pulleycog.jpg)
(http://www.mrequivocal.com/vw/pulleyinside.jpg)
(http://www.mrequivocal.com/vw/pulleyandcog.jpg)
(http://www.mrequivocal.com/vw/lightweightscale.jpg)
(http://www.mrequivocal.com/vw/stockscale.jpg)
(http://www.mrequivocal.com/vw/sizediff.jpg)
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That is just a pulley, not a harmonic balancer as there is no rubber or mass to dampen out the harmonics.
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That is just a pulley, not a harmonic balancer as there is no rubber or mass to dampen out the harmonics.
That would be why it's in quotations. :wink:
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Guess I missed them. :oops:
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Damn, Rob- looks nice. :)
Any detail of the pins you used to tap into the crank? Are they snug with the holes in the pulley? (aka no "tenth of one degree" play in them?
That serp. pulley is really pretty too. :)
Brendan
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Guess I missed them. :oops:
:wink: :lol:
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Damn, Rob- looks nice. :)
Any detail of the pins you used to tap into the crank? Are they snug with the holes in the pulley? (aka no "tenth of one degree" play in them?
That serp. pulley is really pretty too. :)
Brendan
Brendan,
I purchased 5mm hardened dowel pins from Fastenal.com. There is no play. The holes in the crank are 4.95mm (5mm drill bit) and the pins themselves are 5.01mm so a few very light taps of the hammer do get them in. Initially I ordered 5x14mm pins and realized I was being absent minded.
The depth of the cog itself is 19.35mm from where I drilled at the top of the cog to where the face of the crank nose is. So if you go and do the math. I drilled the crank nose by just just over 5mm. I think it was about 5.2mm for each hole. 19.35+5.2 = 24.55mm pins. Just under a standard inch (25.4mm).
So what I decided to do to correct this little difference is order pins that were longer. I'm going to cut them where they need to be cut and then grind them down so they are a snug fit and so the sleeve of the crank bolt presses the pins into the nose. So snug side to side on the nose and pressed down with the crank bolt. Will absolutely have some pictures for you guys when I get that all done. Right now I'm simply waiting on Fastenal's latest shipment (since I had to reorder the right size) :roll:
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brilliant, i wonder how this would work on the older 22mm hub cranks. my 11mm 1.6 has this issue, i did fix it with a new crank sprocket and stuff, but u am sure this problem will return.
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brilliant, i wonder how this would work on the older 22mm hub cranks. my 11mm 1.6 has this issue, i did fix it with a new crank sprocket and stuff, but u am sure this problem will return.
did you put the red loctite on the bolt and give it a good yank?
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yep, i filled the slightly chewed up part in with jb weld... u know what else can you do haha, aside from what this thread is showing.
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yep, i filled the slightly chewed up part in with jb weld... u know what else can you do haha, aside from what this thread is showing.
do you use a/c a lot? i was thinking of having some kind of a/c disengage switch i could use to turn it off when i feel the need for some 'spirited' driving :twisted:
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yeah my ac i think is what made the problem way worse since it didn't get bad until it started getting warm out haha. ac disengages when u have it turned off.
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yeah my ac i think is what made the problem way worse since it didn't get bad until it started getting warm out haha. ac disengages when u have it turned off.
yea but having a button to press instead of moving the selector is much more convenient as that hand is usually shifting gears :twisted:
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easy to do, the magnetic clutch can be disengaged anytime. you could even fit a switch on the pump to disengage AC when going full throttle.
even my 1993 Renault ECU has that feature ;)
you can also disable the alternator and ICE automatically ( if the battery has enough charge to keep everything else going )
any of these systems must have a delay, so if you blip the throttle the AC doesn't get affected, alternator also sends huge spikes if disconnected when supplying power.
EDIT: sorry for the offtopic, great work on the jig!
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just re-reading all this for myself, and i got to thinking - i reckon using a lighter drive pulley isnt necessarily a good thing -
sure, all the load is driven by the crank sproket and associated pulley - BUT, the total inertia of hte system is what reacts when the loads change. so, say your driving along and switch on the a/c, putting a sudden load on the pulley- the less inertia the pulley has, the more quickly it will want to decelerate. so, in theory, the heavier the drive pulley is, the better, because its in the inertia transfer when turning on a load, there is less associated reduction in rpm....
i think...
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Has anyone ever had to replace a crank gear, once it's been pinned?
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i believe maybe one user pinned his crank..
all the others went with the more socially accepted method of TDI crank sprocket.
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Has anyone on this board ever even pinned a crank sprocket?
Moi. My dad's done a couple in Eastern Canada as well.
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http://www.vwdiesel.net/forum/index.php?topic=25424.0
I've pinned a 22mm crank. The above link shows my trials and tribulations on that. Unfortunately I don't have the engine back together yet so I can't report any results.