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Post by Simon on Dec 28, 2014 22:29:02 GMT -5
So I spent the afternoon cleaning up my kart and doing some maintenance. Part of that was a clutch strip down and clean up. When I pulled the clutch part I found a crack in the central hub where that flat needle bearing runs. The crack is in line with the machined gap where you push the clutch key into. That explains the whizzing sound I have been noticing coming from that clutch for a few races. Next I got my box of assorted clutch parts and half clutches and found another one which I pulled apart. Behold, same crack in the same place ! After more digging I found another partial clutch without a cracked hub and build a frankenstein clutch. My suspicion is the radiused shoulder on the crank that the clutch slides up to is forcing that slot in the hub to be opened up and then a crack starts. I double, double checked the installation instructions and it says to only use the supplied radiused washer behind the clutch if running the drive sprocket inboard. I am not, so never used that washer. My guess is that washer should prevent the crank radius opening up the clutch hub even running the thing outboard, so I have put that washer in, even though that is contrary to the installation instructions. Any thoughts from the brain trust ? Did I mention I hate these clutches ?  |
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Post by Dan Pell on Dec 29, 2014 17:02:44 GMT -5
So, just to best understand your plight, the crack is in the machined section of the center hub that rotates inside the interchangeable gear. Does the crack originate at the very outside edge (including the very end that holds the snap-ring) of the hub?
If yes, the problem might have originated from too much pressure when torquing the clutch, or from an impact gun. Simple solution is to put a couple thin spacers between the output shaft (crankshaft end) prior to tightening the clutch down. BTW, not uncommon, and why some create a slight "float" of clutches.
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Post by RichH on Jan 4, 2015 19:59:41 GMT -5
So I just read this forum post on Bob's. Goes against what I had been told for years as for mounting clutches on the crank. The video on Brigg's site is dated '09 but I never seen it before karting.4cycle.com/showthread.php?41482-Premier-Titan-spec-changeDan, you and I have talked about this before and I am pretty sure we agreed about some play in mounting the clutch. Care to give your opinion? |
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Post by Simon on Jan 4, 2015 20:53:40 GMT -5
Wow, the plot thickens and more contradicting information between the Briggs video and the Premier documentation.
- The Briggs video says always use the radius washer (which make sense to me as my cracks look exactly like those in the video)
- The Premier documentation says only use the radius washer if mounting for inboard drive (I'm not, I'm outboard so until last week have never used the radius washer)
- Common practice seems to be allow a bit of float of the clutch on the crank (I have yet to try this)
The end float thing is interesting. The Briggs video says that will cause crank keyway damage, but I have experienced keyway damage with zero float. My personal opinion is crank keyway damage is caused more by clutch judder. I really struggle to believe that the longitudinal pressure of the bolt and outer washer on the clutch hub is going to do diddly squat to stop the clutch hub rotating on the crank.
I used to run my clone clutch with loads of end float and never damaged a crank or key (yes, the clone does not have the torque of the WF, but it was still hauling around an overweight middle aged dude, so was certainly earning it's keep).
For the next clutch service I'm reassembling with radius washer inboard and little spacer washers on bolt to allow the bolt to be tightened up and still provide a little end float. We'll see how that goes.
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Post by Dan Pell on Jan 5, 2015 19:31:03 GMT -5
It's been said that the memo is developed to "protect the sender as opposed to informing the receiver"....Guessing Ron agrees with me. That said, if you hit the end of the clutch with a sledgehammer and it cracked, the first suggestion I'd throw out there is to quit friggin' hittin' the clutch w/ a hammer! If the clutch was floating ever so slightly, there's ZERO potential to encounter the result Simon experienced. Interesting thing here, we used to have problems with clutches, now have zero issues. The reason, experience is a great teacher. Briggs is not happy with some of the variations encountered w/ the Titan piece, seems neither are the Aussies.
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Post by ron90 on Jan 5, 2015 19:55:01 GMT -5
quit friggin' hittin' the clutch w/ a hammer! Now I have to get rid of my hammer. that's okay. If Rich is in the pits I can use his HUGE crescent wrench to wail all over the kart. We all know I use hammers and zip ties to stay on the track. |
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Post by Dan Pell on Jan 7, 2015 12:44:02 GMT -5
Ron, guessing there are a bunch of hammers, Crescent wrenches, and trailer hitches in the NFRA pits. Who knows what Rich keeps in that van as well, holy moly!
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Post by ron90 on Jan 7, 2015 15:57:11 GMT -5
Ron, guessing there are ... trailer hitches in the NFRA pits. I did not even think of those. That could be even more effective than that 10 pound sledge we used in Dixon. You should have seen the faces of those watching us. Then I said, "Eh, the front end looks pretty good. I put my suit on and ran to the grid." I hit my clutch all the time. It keeps it making those clinging and clanging noises as I go down the straight. People stay away from me because they think it is going to blow. |
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Post by Dan Pell on Jan 8, 2015 13:38:43 GMT -5
Only brought up the hitches based on raceday experiences seen. It's been said that necessity is the mother of invention, and nowhere else is that more evident than the NFRA pits!
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