levelr123g

I have built spin fixtures for and conducted valvetrain dynamic testing when I worked for McLaren Engines http://www.mclarenperformance.com/s...ines-index.html
as well as other places during my 20+ years in this business.

He doesnt work for mclaren anymore. obviously you did not read all the documents I provided to you. the pulley would have to break in order for it to protect the crank so that it would freewheel or spin. if the bolt holds the hub of the pulley to the crank and the bolt provides all the force necessary to turn the pulley without the key then NO you are wrong. You would need to break the pulley in order for it to protect the crank. The key on the other hand is the weak link here and is designed to shear when loads placed on it are greater then its designed shear point. I have supplied documents which clearly states that the key is used to transmit torque. READ! Im not making this up, its documented.

mdp c230k

It is the friction between the pulley hub and the crank and the bolt and the pulley hub that enable the cranks force to be transfered to the pulley. It's the tension on the bolt that provides the force on the friction surfaces. If the friction force is overcome the pulley will slip with a key. If you have a box with a brick in it it will take 1 x mu force to slid it on a surface with a friction coef of mu. Put 10 bricks in the box and its 10 x mu to slide it. Just exceed the tension x mu of the bolt pulley comb and it too will slip.

20FHK02

My impression on this argument is that nov0798 is trying to prove DCXdynodog wrong on all engine designs. I think DCX is only trying to say that the key for the M111 engine is not used to carry the loads, and cited some examples from other engines to support his argument; he never say that ALL engines use clamp force design. But nov0798 cited different examples from other engines and trying to prove that ALL engines use keys to carry the loads.

I know that, in the real world, there are different designs on similar products/applications. Different engineers have different ideas on how to make a thing work.

mctwin2kman

Actually if the key was not needed then you would need a pulley extractor to get the pulley off after the bolt was removed. In this case both the bolt and key are needed. If the key was not needed then the pulley would need to be press fit on the crank and the bolt to hold it in place. The key is there for alignment and then the bolt makes sure the pulley stays in contact with the key.

levelr123g

i am not trying to prove anybody wrong on engine design, the key is needed to protect the crank. The key does transmit torque from the crank to the pulley. If everyone here is so sure that is does nothing more than align then do a simple test. Go out to your car, remove the key and tighten the bolt. It should work RIGHT!. I dont think anyone here would do that because they know it wont work. SO back to my original statement, the key DOES transmit torque from the shaft to the pulley. Until you exceed its designed shear point then it wont shear and will continue to transmit torque.

Matt230K

No, this isn't why they wouldn't do it. Most people here wouldn't do it (myself included) because we aren't sure exactly how it works. There are only a few of you (so-called) engine experts here and there are too many sides to the argument for anyone to want to test this. Few here would take a chance on something that could potentially cause problems if done incorrectly or at all. This doesn't mean you're right, just that it's not perfectly clear which way is right.

20FHK02

It will not work, because without the key how can the pulley be properly aligned?? If the key is not needed then MB won't put it there. But the present of the key does not exactly mean it has to carry load.

Oranges and apples grow on trees, but you cannot put this to all fruits and claim that whenever you see a fruit it must be grown on trees, because there are strawberrys on bushes and watermelons on the ground. Similar to engine design, the key for the M111 engine may be for some other purpose. I'm just not convinced that MB designs a ~5mm long wedge shape key to carry all the loads from the pulley spinning at 5000rpm.

mdp c230k

2fhk02, I agree with you on your analogy but the watermelon is a vegetable!

mctwin2kman

I can put it this way, if the key was just for alignment purposes the one person that had the ASP pulley and had a key shear would still have been driving his car today if the key was not needed. Instead the key sheared and the crank pulley stopped turning at the right speed.

ice777

both the key and the bolt share the job

there, now everyone can stop fighting!

20FHK02

Opps....

levelr123g

20f
what needs to be aligned on the pulley? nothing!

20FHK02

The timing mark, otherwise there is no way to tell how to get the piston 1 to TDC. The pulley not only serves as a driver, the timining marks on its surface serve as an alignment tool for cylinder pistons. People put aftermarket pullies not just for power alone, they also want to keep its other functionalities intact.

levelr123g

well seeing how you cannot change the timing on our vehicles, who cares. plus the timing change would be done by the computer, which would show the timing anyways.

levelr123g

actually you could still set the pistom at tdc without the use of the timing marks. the only reason you would need to know tdc is if you are playing with the cams, and since you would have the valve cover off anyway it would be easy to find tdc without any markings, just look at the cams.


hmmm I supply documentation and the experts vanish. I guess ill change my screen name to whodini.

speedfrk

nov0798, Nobody feels like arguing with you because you don't understand basic engineering principles. And don't bother asking for me to "PROVE IT", because trying to prove something to someone who can't understand is an exercise in futility. Check out tedypedy's post here http://www.csportcoupe.com/forums/sh...&threadid=1392
and see if you can connect the dots.

dswildfire

since when? last i checked, the rule was that if it had seeds, it's a fruit. just like cucumbers.

levelr123g

yea his post is fine but if you read the documentation i supplied, it clearly states that keys are used in the transmission of torque from the shaft to the driven part. As you can see in one of the documents, it takes almost 600 ft lbs to shear a hardened key of a particular size. the experts here claim to know all the answers yet I have yet seen one to dispute the documents I supplied. Here you want a **** simple test. go out to your lawn mower remove the blade and the remove the key that is between the hub and the shaft. start it up and go mow your lawn. I bet you will not get even 2-3 minutes into your lawn b4 the blade stops turning and the crank welds itself to the hub due to friction, well actually at this point it will turn because it is welded. But i guess the key has nothing to do with this because all the force if the blade is held in place by the bolt, right! We can keep this up as I will continue to provide example after example, yet no one can prove otherwise, hmmmm.

levelr123g

does a banana have seeds? but a tomato does is it a fruit or a vegetable?

dswildfire

yes, a banana has one seed. it's the black thing at the end opposite the stem (the one under the peel). and yes, a tomato is a fruit.

levelr123g

here scroll down to page 9 and start reading

http://www.ecs.umass.edu/mie/courses.../lawnmower.doc

hold on ill find more.

speedfrk

You oversimplify everything to the absurd. A key can transmit torque if it is DESIGNED to do so. No one disputes that. The question here is whether this particular engine and pulley are designed to do that. The post I referred to clearly show that the key can be sheared off in this engine if the pulley is not properly seated and/or torqued. Here's a test for you- Go out and loosen the bolt on the pulley on your car to just enough so it won't fall off-say 20-30 ft-lbs. Drive your car until the key shears off, and then come back and tell us how the key takes all the torque.

levelr123g

well obviouslt the key is designed in this vehicle to transmit the torque as shown in the pulley that failed. The bolt was still tight yet the pulley wasnt turning, go figure. once again the key is there to transmit torque and protect the crank. yes i must over simplify everything as this is all people understand. tomorrow we will do colors! as for the key in the post you refer to , it sounds like this key was broken at production time and possibly the pulley was slammed on there and broke the key, who knows but eventually it to would have failed due to its lost structural integrity.

DCXdynodog

Sorry, this is certainly not "top secret" stuff, and I don't think a pic of this cam hub/sprocket would be a problem, but I am bound by rules not allowing cameras other than by special permit from our security dept. There are rules about disclosing things as well and I do have to think about what I talk about. (this is an R&D facility for future products after all)

We do have one engine in production that I know of in which the cam is *not* aligned by anything and special fixtures on the assembly line set the timing. I think it is our 2.7L V6 but not sure about which one. (and the bolt is in the center)

If I could, I would. but would you believe it? How would you know it ran? How would you know I didn't build it just for you and an arguement over the internet?

levelr123g

it might run initially but not for long, unless it was a press fit.