The Flywheel is connected to the ....

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Hurtzberg
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The Flywheel is connected to the ....

Post by Hurtzberg »

.. Nothing.

My flywheel bolts have decided to snap. Two snapped and the remaining 2 damaged their threads and undid themselves.

I imagine the massive 40something Hp the engine has is just too much!

Do we have a recommendation on repairing the bolt hole threads? I guess a slightly oversized thread for the bolt holes is the most permanent option.

Anyone had this before ? I did use a torque wrench when I did them up. They were the original bolts.

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Thanks, Andrew.
Andrew

1957 A35
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Re: The Flywheel is connected to the ....

Post by Tight Yorkshireman »

You can get the damaged threads repaired with heli-coil inserts either yourself or at an engineering company
guess you take the crank out for repair to the engineering company or maybe another crank? It needs to be done properly as it is securing the flywheel after all.

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Dave Clark
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Re: The Flywheel is connected to the ....

Post by Dave Clark »

Did you use Loctite Andrew ?

It is possible to re-tap the damaged threads a little bigger, in situ, if you are careful and get them dead straight. Crankshaft is quite tough so beware snapping the tap !!

Use all new bolts. If you can,t get the ones with the reduced head send them to me and I will turn them down.
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Re: The Flywheel is connected to the ....

Post by Neil Evans »

I would scrap the flywheel as it's almost certainly worn the bolt holes...
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Big Daddy
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Re: The Flywheel is connected to the ....

Post by Big Daddy »

Hurtzberg wrote:Anyone had this before ? >>> They were the original bolts.
Yes I had this happen on a 995cc race engine, caused by aggressive starts off the line. Standard bolts stretched hence losing clamp load, allowing the flywheel to loosen and then shear the bolts by impact.

Suggest replacing standard bolts with high tensile socket capheads (ref photo). Chemically clean bolt and crank threads with degreasing spray and install using medium strength Loctite. Hardware torque can be increased to 50 lbf.ft if required. Caphead bolts can be refitted many times... :thumbs:

Redrilling 948 crank for 6 bolts and location dowel is the ultimate solution, but don't bother with just 40hp... :mrgreen:

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Hurtzberg
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Re: The Flywheel is connected to the ....

Post by Hurtzberg »

Thanks all.
Dave, I was using new lock tabs not loctite. Do you recommend just loctite without the lock Tab?

BD, it could even be 45hp!

It will be a while before I can work on her again so I will probably just collect parts for now.
Andrew

1957 A35
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Re: The Flywheel is connected to the ....

Post by Big Daddy »

Hurtzberg wrote:Thanks all.
Dave, I was using new lock tabs not loctite. Do you recommend just loctite without the lock Tab?

BD, it could even be 45hp!
Throw lock tabs in the bin - they are hopeless. Use medium strength Loctite instead (not high strength because you may want to undo the bolts in future).

Power isn't really the issue. Instantaneous torque peaks in the driveline are dominant, mostly due to inertia.
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Re: The Flywheel is connected to the ....

Post by gazza82 »

Well now we know what the funny noise was .... :shock:
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Hurtzberg
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Re: The Flywheel is connected to the ....

Post by Hurtzberg »

Morning all,

Yes Gazza , it was good of the last remaining bolt to hold on for as long as it did!

A rare event happened on this thread, BD and DC both agreed on something !

Is the same recommendation for loctite instead of locktabs true for inside Engines too?

Is it ok to start the engine without the gearbox/flywheel attached? I'd need to use the cranking handle but it would be nice to check it was only the flywheel bolts causing the noise before a do the drilling and tapping.

Thanks again. Andrew
Andrew

1957 A35
Dave Clark
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Re: The Flywheel is connected to the ....

Post by Dave Clark »

As BD says locktabs are a waste of space. Being soft metal they slowly compress enough to relax the tension on the bolt. I use ARP bolts on the big ends and not even Loctite but I would use it with regular bolts.

I know people have started various engines without flywheels but be very careful. It will rev like crazy and may be off balance as well. Flywheel is there for several reasons one of which is to damp vibration.
Hurtzberg
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Re: The Flywheel is connected to the ....

Post by Hurtzberg »

Thanks Dave. Your knowledge is always very appreciated.
Andrew

1957 A35
Big Daddy
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Re: The Flywheel is connected to the ....

Post by Big Daddy »

Hurtzberg wrote:A rare event happened on this thread, BD and DC both agreed on something !
Appearances can be deceptive. Although always open to robust debate, these days I reckon Dave and I agree on over 95% of issues. Different approach can lead to the same conclusion... :thumbs:

Hurtzberg wrote:Is the same recommendation for loctite instead of locktabs true for inside Engines too?
:iagree: ... :thumbs:

Hurtzberg wrote:Is it ok to start the engine without the flywheel attached?
Don't do it :!: With very low inertia, even small throttle changes can send engine speed soaring, causing damage... :shock:


So DC and BD agree again... :mrgreen:
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Dave Clark
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Re: The Flywheel is connected to the ....

Post by Dave Clark »

And we both like beer and red wine too :cheers:
Big Daddy
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Re: The Flywheel is connected to the ....

Post by Big Daddy »

And rugby union, good food and driving fast on race circuits... :thumbs:
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Hurtzberg
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Re: The Flywheel is connected to the ....

Post by Hurtzberg »

Speaking of which, Will we see either the s2000 or a Turbo mx5 at the Bird in the hand this year? Might even be some of that beer or red wine with your name on it.
Andrew

1957 A35
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