911 Clutch Bell Screw Broke Off In Crankshaft 911

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CRSMP5
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Post by CRSMP5 » Wed Nov 26, 2003 11:27 am

yep will work for all sg shafts.. and yes the threads cut is the variable.. the further forward the flywheel is the less you cut.. the thinner the flywheel the more you have to cut..

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Post by iCow » Wed Nov 26, 2003 11:33 am

ah yes.. i see your point... so the only constant is the depth of the pilot adapter which cannot bottom out when screwed on. This should be fun.
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Post by tbill » Wed Nov 26, 2003 5:33 pm

another note on this, when i cut the crank for the mach .26, i was useing the stock .21 flywheel. the only thing i needed to change when i put on the envy flywheel was the brass washer between the flywheel and adapter nut, and that was to get my springs to line up better.
savage #1 lrp z28, savage #2 mach .26, savage #3 wasp .26, savage #4 mach .26, savage X, Hellfire, GS storm,
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Post by iCow » Thu Nov 27, 2003 1:06 pm

Ok folks here we go... in a nut shell this surgery on a WASP 26 crankshaft will NOT work! ARRRGH! The section of shaft between the threads and the engine body is too long when using the OFNA pilot adapter. Also the adapter won't go passed the shaft section between the threads and collet. it basically ges stuck there, nowhere else to go. It's not bottoming out, just that's the stopping point. The pilot nut is perfect for the shoe springs, but the overall length of the adapter pushes the clutchbell to far toward the spur and it rubs and it won't mesh properly. If the area of shaft that is too long was the same length as the Mach .26 crank then all would be well and I'd be playing right now, but alas it looks as though i have to by a new crankshaft now ~great~. Not to mention I think the piston got messed up when i was torquing on the pilot adapter. i think I may just wait for my replacement S-25. Looks like I need to dismantle the WASP to make sure I didn't screw up the sleeve and piston.

Here is the lesson: Always use Hex screws whenever possible, and watch the lock tite!

Anyway the surgery went fine. Here's some pics:

Here's the crank end with the screw broken off in it...
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The crank with everyhing mounted for measuring...
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You can see where my concern was foreseen even before i made the cut...
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I made a depth check on the pilot adapter...
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You can see here how much better the springs will line up...
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Took everything off and bottomed out the stock nut for the cut...
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Making the cut, the nut will heal any threads that get marred during the cut...
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Cut done...
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New adapter screws right on...
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Here's the crank section I was talking about. See how long the section between the body and the threads is? The pilot adapter stops where the section starts, it's really only about a 1/4 inch too long...
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Oh this is why you shouldn't use zip ties to lock your piston...
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Ok I put everything on and put on the new HPI shoes. Someone was right. What a PITA!But here's a good way to get it done...
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All new shoes...
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Ok here's where you can clearly see the problem. WAAAAY too long. No matter how you shim it, it's just pushes the CB out too far into the spur...
Image

While this is an ideal solution for some situations, if you have an engine with an SG crankshaft this is most likely NOT going to work. I guess I'm the guinnea pig on this, but it loks like the only true solution is to buy a new crank if you can't get the end screw out.

Learn from my screw up...

Comments welcome...
[url=http://www.iconicarts.com/savss/racer/]My Racer Project - Codename: Little Boy[/url]

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Post by CRSMP5 » Thu Nov 27, 2003 1:13 pm

shave the brass collit down against the bearing side of it.. :wink: that will move the flywheel back more.. you could also remove a tad bit of the nut onto the shaft.. ive seem picco with that shjaft on it at the track which is who i know it will work.. its just a matter of rethinking the issue..

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Post by iCow » Thu Nov 27, 2003 3:27 pm

Well the collet and flywheel aren't really the issue. it's the length of shaft between the engine body and the threads. The pilot nut gets stopped at the forward part of that section. That's where I'm stuck.

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Post by ChiefPig » Thu Nov 27, 2003 3:44 pm

So are you saying that the ofna adapter stops at the end of the thread before the flywheel is tight? Have you tried the thinner collet that came with the SS?

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Post by tbill » Thu Nov 27, 2003 5:15 pm

icow, looks like the adapter you have is taller in the actual nut area than the one i used on the mach. i plan to go to my LHS tomorrow or sat., i'll pick up another one to look at [don't want to take my clutch off again :oops: ], i'll post a side view pic of it if it looks alot different than the one you have. i am determined to get this $10 repair to work for you.
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Post by ChiefPig » Thu Nov 27, 2003 5:19 pm

tbill wrote:icow, looks like the adapter you have is taller in the actual nut area than the one i used on the mach. i plan to go to my LHS tomorrow or sat., i'll pick up another one to look at [don't want to take my clutch off again :oops: ], i'll post a side view pic of it if it looks alot different than the one you have. i am determined to get this $10 repair to work for you.


tbill, is this what you have (Traxxas):

Image

It is definitely shorter.

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Post by tbill » Thu Nov 27, 2003 5:32 pm

i do beleive that is the one i used, but i can't find the packaging anywhere to be 100%sure.


found it! boy was i way off, it's an XTM clutch nut, p/n 233220

http://www.globalhobby.com/public/gallery/233220.asp
savage #1 lrp z28, savage #2 mach .26, savage #3 wasp .26, savage #4 mach .26, savage X, Hellfire, GS storm,
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Post by iCow » Thu Nov 27, 2003 9:52 pm

ChiefPig wrote:So are you saying that the ofna adapter stops at the end of the thread before the flywheel is tight? Have you tried the thinner collet that came with the SS?


Yes that's exactly it. i know it's not bottoming out inside the pilot adapter because i measured it. It's because the pilot nut is too long.

Well I guess it helps to have the right part to do the job! :) I guess it's another few days of wait time while the other part ships. That XTM pilot looks like the one... and I will be able to shim it properly too!

Oh one thing. I tried grinding down that shaft section just a tad to see if i could get the distance I needed to clear the spur. No luck of course. I just took off the lip a bit. Of course this was done before the correct part was posted. :D You don't think I threw it out of balance do you? The flywheel and nut should correct anything right?

Oh and how are the pictures? I'm using a 4MP Sony CD-R digital camera with great macro support. I like that you can see my finger prints... :twisted:
[url=http://www.iconicarts.com/savss/racer/]My Racer Project - Codename: Little Boy[/url]

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Post by ChiefPig » Thu Nov 27, 2003 9:59 pm

iCow wrote:
ChiefPig wrote:So are you saying that the ofna adapter stops at the end of the thread before the flywheel is tight? Have you tried the thinner collet that came with the SS?


Yes that's exactly it. i know it's not bottoming out inside the pilot adapter because i measured it. It's because the pilot nut is too long.

Well I guess it helps to have the right part to do the job! :) I guess it's another few days of wait time while the other part ships. That XTM pilot looks like the one... and I will be able to shim it properly too!

Oh one thing. I tried grinding down that shaft section just a tad to see if i could get the distance I needed to clear the spur. No luck of course. I just took off the lip a bit. Of course this was done before the correct part was posted. :D You don't think I threw it out of balance do you? The flywheel and nut should correct anything right?

Oh and how are the pictures? I'm using a 4MP Sony CD-R digital camera with great macro support. I like that you can see my finger prints... :twisted:


Pics look great.

I did not understand which part you grinded. Maybe more pics would help? LOL! :lol:

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Post by iCow » Thu Nov 27, 2003 10:23 pm

ok here's what i did. It wasn't much and I kept it pretty even. it shouldn't cause a problem right? I've done this on bigger engines before (non-rc) but they don't spin at anywere near the RPMs that nitro engines do. Thoughts?

Image
Last edited by iCow on Fri Nov 28, 2003 3:55 am, edited 1 time in total.
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Post by iCow » Thu Nov 27, 2003 10:49 pm

tbill wrote:i do beleive that is the one i used, but i can't find the packaging anywhere to be 100%sure.


found it! boy was i way off, it's an XTM clutch nut, p/n 233220

http://www.globalhobby.com/public/gallery/233220.asp


ok GREAT! now where do i get it from? tower doesn't have it...

nevermind.. found it here http://www.hobbypeople.net/gallery/233220.asp
[url=http://www.iconicarts.com/savss/racer/]My Racer Project - Codename: Little Boy[/url]

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Post by ChiefPig » Thu Nov 27, 2003 11:09 pm

Another good pic :D

Yeah, I don't think that is enough to affect the balance of the crankshaft. The flywheel and clutch nut adapter are a lot heavier than what you took off. Those parts are probably not 100% balanced as well.

But I guess we will eventually find out, right? :D

This thread should be made a sticky cause there is so many info here that would definitely help people in the future not to make the same mistakes :D I know I will be confident enough to cut my crankshaft this accident ever happens to me in the future.

Maybe you can do a tech tip writeup later on after all is well, iCow? You already have good pics for it.

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Post by CRSMP5 » Fri Nov 28, 2003 9:12 am

ok.. back to something i posted before i left and did not return to now.. did you try to shave down the NUT section against the flywheel to bring the shaft/nut further back? spend a little time and see how much you can machine off to fit the springs into the grove properly.. or even preload them towards the engine block a tad bit..

also it is planned to make a tech tip out of this once its completed.. it is something that honestly, is needed cause this comes up way too often.. just your the 1st lucky person to need lots of help solving it.. :D

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Post by iCow » Fri Nov 28, 2003 11:01 am

i ordered the XTM pilot nut and will try that first. if it fits then i dont have to worry about shaving off the OFNA pilot. I'd rather shim than shave. :)

thanks though.

the other pilot is only like $3 so it was no biggy to get.
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Post by tbill » Fri Nov 28, 2003 7:32 pm

icow, if you don't have any luck with the xtm pilot nut, send me your crank, and i'll stick it in my wasp and i won't send it back untill i get it to work 8) sorry to have led you down the wrong path on the adapter nut [ofna/traxxas/xtm], but who in the heck would have thought there would be SO much difference between them? the only other thing i am not sure of [which i should have checked] is if the crank shaft diameter is the same between the mach, and the wasp, as far as where the collet slides on.


balance issue, i don't think it will come into play really, given the size of the crank, the way it is cut, and the fact that most of the rotating mass is at the clutch end of it, i don't think it matters really.
savage #1 lrp z28, savage #2 mach .26, savage #3 wasp .26, savage #4 mach .26, savage X, Hellfire, GS storm,
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Post by iCow » Sat Nov 29, 2003 8:51 am

it's not the wrong path, just had the wrong nut. So far I'm at $10 instead of $80 so I can't complain really. I just want to get it working again. My SS was sadly missed over T-day and i miss it too. :(

I believe the shafts are the same diameter. They should be pretty standard in the BB engines right? It says the XTm nut is for a 21 conversion so I'm assuming it will work... we will see in a few days.
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Post by iCow » Wed Dec 03, 2003 7:29 pm

well actually yes... i got the XTM pilot adapter this afternoon (darn holidays). it is exactly the same as the stock one EXCEPT that the only hex to grab onto is at the base of the nut. Not an easy thing to get torqued down.

The only other thing I can see after doing a dry fit for length and shimming is that the pilot shaft is now about an 1/8 of an inch too SHORT now and there's no way to make it longer. if I put the end screw in as is it ends up torquing down on the brass bushing and the CB starts grinding and it doesn't spin freely. the only way to avoid this is to get things situated so the end screw just meets the end of the pilot shaft. I've tried all kinds of variations so far including using the shaft extenders but then i have to add like 6 shims and it just looks like crap. So I took a break to clear my head and played with my kids.

then it hit me. i'll just grind down the brass bushing until it's even with the pilot shaft end. Then everything will be snug as a bug. Once i get everything figured out i'll shoot some pics from the beginning. Then I'll redo a tech tip from the start so a Mod can move it later.

Down the road I may try out that traxxas pilot adapter as well. I just wanna run again. i have a weeks vacation coming up Xmas week and i'd like to hit the track a couple of days...

I may also revisit CRSMP5's idea of shaving down the OFNA nut to shorten it enogh to fit right. the spprings lined up perfectly without any shims and the hex was very easy to grab onto. We'll see.

I'll post soon...

PS: I think in the end (after Xmas) I'll look at getting a new crank altogether. I'm gonna get some serious runs in on this engine with the surgery fix just to test it's durability for those who follow in my mishap. I think I may have screwed the sleeve, but we'll see. If it blows up... it blows up.

And that's that with that...
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