Loud knocking fixed!

[carbon-rod]

So I have been working on the engine, getting it ready to run and I have had this really loud knocking noise, I thought it was diesel knock as the engine has always done this, I was kind of disappointed considering I told the Mrs I would be able to make the engine silent enough to run it in suburbia prior to buying it. So I started to do the balancing on my engine the other day and noticed there is a half mm gap between the flywheel hub key slot and the key itself, the key fits not too badly into the shaft but there was quite a bit of slop in the hub. I did some research on the net and I found that someone else had loud knocking noises I think they likened it to someone hammering on an anvil with a sledgehammer, well this was what this sounded like!

So I was going to shim the gap but you think I could find anywhere that sold thin brass sheeting for shimming? so I ended up welding a bead onto the gibkey and filing it down to the correct height to take up the play, I like this solution because you only need to do it once and don't need to worry about losing the shimms if the key is removed. I also tightened the fit into the shaft keyway as well. voila!! the noise was gone! I couldn't believe how quiet it was after doing this, such a relief, I might actually be able to get it quiet enough to run without the neighbours putting in complaints now.

I took a quick before and after video, its hard to distinguish the difference in noise when recording on a mobile phone so if you compare the different in sound from when I have the decomp lever enabled and disable you will notice the sound difference, the knocking only occurred when in normal running, not when the decomp was enabled. The second video does a similar comparison, this time there is minimal difference between decomp and not.

Any way, I hope this helps someone else out there having a similar issue, the gib key now has a 0.5mm step to take up the play, it looks a little rough but works sweet.

Before

[youtube]http://www.youtube.com/watch?v=mgWt2sxhUTA[/youtube]

After

[youtube]http://www.youtube.com/watch?v=v85aRSc2bvA[/youtube]

[ronmar]

Yep, that's what a wheel working loose sounds like:)  A loud diesel knock that starts to take on a bell ringing tone as it gets worse... 

[dieselgman]

Bravo! A very good illustration for the forces involved and the necessity of keeping those flywheels TIGHT! Now, what viewers would like to see is the exact repair process you used!

Thanks!

dieselgman

[carbon-rod]

Dieselgman,

I have a couple of photos of the key, they didn't come out so well though, I will make up a little drawing which will help illustrate things.

So the photo below is my first attempt at building up the edge of the key, I used silver solder and filed it down, it's hard to build it up enough as the solder tends to pool and it's not the most durable metal either so I decided to weld it the second time.



My second attempt was to lay a bead using the mig welder and file in a step. Again it's hard to see the step but it is there, man it is difficult to get it precise! I really need to buy a milling machine! I could have milled 10 keys in the time it took to modify one, oh well my time is free correct?



I really like the idea of not having to shim the keyway because it provides a more permanent solution, I also found that the key in the shaft was slightly larger than the key so I fixed that issue as well, now the key is nice and tight in there as well.

[dieselgman]

Very good, I see that you are working with your key width because it did not properly match the slots in crank and flywheel. Good pictures! I have seen quite a few of these sorts of width mods on clutches and pulleys in various machinery.

It may be important to mention that the magic of the gib key as used on the Listers is its taper. A proper key will have a very slight but regular taper in thickness from one end to the other. This is what allows it to bind the flywheel to the shaft as the key tightens gradually as it is driven into the slots. It acts as a wedge. In my experience, it is this wedge action that keeps things together and therefore the mechanism maybe somewhat less reliant on the actual shoulder contact between the keys and keyways (although those should also fit snugly if possible).

I hope this clarifies things somewhat for those who need to deal with their flywheel connections.

dieselgman

[SHIPCHIEF]

you might want to consider a locking collar on the shaft to hold the key in.
Just a belt & suspenders deal. Like wearing a helmet when you ride a bike.