Are Heli Coils safe in a Flywheel???

I didn't read the whole thread mainly 'cause I didn't want to get caught at work, but here are my 3 statements, and sorry if someone mentioned them ALREADY!!! FIRST we use helicoils ALL day at my company that makes HUGE aluminum molds for ingots, and billets to p*** thru, and if anyone is aware of the immense heat and pressure that goes on in making ingots and billets you would know the forces upon the helicoils, Next, aren't the friction discs on the clutch ***embly held together with (for a lack of a beter term) GLUE!! I would think a metal coil inserted into a threaded metal item would be stronger than the glue?? and Lastly, there are items that we also use on occasion at work called "time-serts" they are a threaded "barrel" that is one piece with the threads on the inside for the original hole size, and on the outside for the enlarged hole. This time-sert is a one piece item that I myself have NEVER seen fail! The WHOLE barrel would have to be pulled out, not just the "unraveling" of a heli-coil. If you are unsure of the "coil" I would suggest using the time-sert method and have NO WORRIES!!! Then again this is just my "opinion"!!! Ken

 

Read the post people,,,, it is NOT an aluminum flywheel.

 

do what you like thats what I did...

 

My foam mockup block has heli-coils and they seem to be holding up perfectly fine.

 

Did your flywheel come apart too? Where the bolts sheered off at the thread base or pulled whole?

 

Foam won't cut my foot off. I just go to the next size metric tap and no drilling. Always works fine.

 

fly wheel did not come off.,..pressure plate bolts were sheared..threads were still in fly wheel...

 

Then that was not a helicoil issue. Under rated bolts, loose bolts, or something else,,, but not a helicoil issue when the bolts were sheered off.

That was my point on the very first page. The stress on a pressure plate bolt is from a sheer point, not a pulling outward from the threads issue.

 

I'm thinking over torqued. I've seen it quite a few times...

 

You guys need to figure on application and how a part is designed to (or not to) fail. When you are putting a helicoil into, lets say, a engine block main, the bolt will typically fail from being pulled directly outward from the block from pressure forces. On a reciprocating m***, such as a flywheel, the designed failure comes from a sheering off of a bolt, rather then a pulling out of the threads. Two entirely different failures.

 

now just wait a gosh dern minute, that is being entirely too logical

 

First Id go ask Don Garlits if a flywheel that cant be guaranteed 100% is a good idea...
Doc.

 

ok sorry I see your point...but it failed while shifting..

 

The issue I would have is, what caused the damage to necessitate the Helicoil? Is there any danger that in stripping the threads out wards pressure has been exerted on the surrounding flywheel metal causing small cracks? I would have the thing X-rayed for them. Then drill larger and re-tap.
Doc.
Doc

 

Can ANY part be guarenteed 100%????

No need for sorrys, I dont gain one way or another if Helicoil makes a sale. I'm just OCD when it comes to things like this (one reason my dad thinks I should have gone further in life). When something fails on me, I want to know WHY it failed. One reason,,, so I don't do it again, Second reason is that OCD. Most guys have stories that their wives or whatnot say, "it's brand new, dont take it apart to look at it". I don't just take covers off, I pull that stuff apart. I mean REALLY apart. Anyway



Zman is right, more often than not, the bolts fail from over tightening. Bolts rated shear strengths come from the amount of stretching designed into them. Any bolt over or under tightened will not test rate the same as one tourqued to specs. Another reason, people REUSE the bolts, big no no. Bolts lose strength from stretching EVERY TIME you reuse them, some studies show 35-40% strength loss. Another issue is testing and certification.Many bolts come from China, btw hows that Harbor Frieght tool holding up , and often, although the bolt is MARKED grade 8 it often will not hold up to testing. Often times no higher then a grade 2 bolt. EVERY bolt I NEED to hold, I buy from a reputable dealer that HAS SPEC SHEETS on the bolts I'm buying. Name brand stuff will have it and be availiable, Checkers and Home Depot wont.

 

I won't guess on the condition of the flywheel or its metallurgical properties but I spent 15 years in aviation machine work and know for a fact that helicoils will be fine for this application IF properly installed. As for someone arguing the aluminum issue... forget it. The mainshaft in the jet engine that bolts to the turbine blade ***embly (crankshaft equivalent) is helicoiled if needed and it spins far faster than you will ever see a car engine turn. I have seen helicoils in cooling turbines that spin in excess of 50K rpm with no problems. I have installed helicoils in aluminum, stainless, hastelloy, ***anium, cast iron, even in some resin products successfully.

As stated I won't vouch for unseen workmanship but the helicoil process will stand up to anything a normal car will put on it.

 

Thats very common to have it go during a shift. As the pressure plate releases and engages forces are transmitted through the flywheel as if the pressure plate was trying to make the flywheel into a salad bowl. The stress placed on the parts due to centrifical forces are tremendous. Most of the time the iron flywheel or iron pressure plate ring lets go due to fatigue and heat cracks....taking everything out in its path including popping the pressure plate bolts off like a toddler picking daisys. A slightly less violent explosion occurs when just the clutch disc blows up. I've that happen to me on a big block Mustang I had, I still keep the parts sitting around the shop for reminders.

Believe it or not that big ol' flywheel is flexing a little under those conditions....and you all know what happens when you flex cast iron.

Bigchief's keep your legs for a while Rules of Thumb:

1. Never run ANY flywheel that exhibits severe heat marks or ANY cracks. Don't be fooled by resurfacing the wheel to a clean surface (machining the minor surface cracks away) the wheel has already been overheated/over stressed at that point and all those little stress risers go WAY father into the metal than you think.....think dead man walking at that point. Many racers get away with this with a steel wheel, however......

2. Use steel flywheels if you can afford them (cheaper than new legs) ANYTHING the far side of stock daily driver that your gonna drive like a daily driver should have a steel billet (not cast steel) flywheel.

3. NEW grade 8 bolts everytime its apart for any reason.

4. Hel-A-Coils and/or other thread inserts are fine when properly installed.

5. If your turning over 6000RPM its a good idea to have a blow-proof bellhousing and SFI approved clutch.

Happy Walking!

-Bigchief.

 

More times than not there is no room around the pressureplate bolt holes for larger bolts/larger bolt heads. This is especially true when using larger 11 and 12" clutches.

-Bigchief.

 

just slit your wrists dude this build is over. i thought it looked cool but a helacool flywheel is so gay.

 

Thanks for your support Drew. Maybe some VW lights would revive this pile of ****.

 

i would have checked for cracks and have machine shop tap it out to next size or use a timesert . then i would run it .

 

Just my 2 cts worth

if it bothered me rotate and redrill, if the helicoil was put in properly key word ( properly) i would have no problem with it.
I am a retired aircraft mech ( major airline) i can tell you if you fly at all-- you have ridden on airplanes that have been helicoiled. We used them all the time on the jet engines.
Really depends on how they were put in

 

Did you get your pressure plate bolts at Yousef's Imported Hardware store? Good made to be Pressure plate boltsd, properly installed will not all shear. If they did it had nothing to do with the Heli-Coil. It held

 

I always have been taught a properly installed Helicoil is stronger than the threads that were originally in the part...

 

on second thought.............I think Tony is correct, buy a new one from him.............I'll take your old one , no more RPM's then I turn my motor I'll leave the damn bolt OUT !

 

we used them on molds in the plastic industry and they never failed under 700 tons of pressure making HDPE pallets and fish bins.

 

Don't take the chance its your legs that will pay , just redrill the mounts it's easy ! Your a Jet Doc

 

WOW....7 pages of debate on Helicoils and their use??? Really???

Doesn't overthinking **** all the time make your heads hurt?????

 

wow.. why hasn't anyone suggested a ****ter shield? surely reduces the risk..(which imo is 0%)... but still..

 

Helicoils are fine in this application. We used them to repair forming dies with 100 ton presses with no problems. All you are really doing is enlarging a hole and inserting new threads. I would however have that flywheel checked for cracks prior to doing ANY sort of machine work or inserting heli-coils.

From the heli coil website....



HeliCoil Thread Repair Kits are used for creating stronger internal threads in all metals, composites, polymers and other materials by repairing damaged or stripped internal threads and regaining the original thread size. HeliCoil Thread Repair Kit creates longer lasting durable threads, avoids thread over-sizing, increases the possibility of higher torque application in weaker metals, significantly reduces the bolt breaking problems & HeliCoil being made of stainless steel protects against atmospheric corrosion