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Old 23rd July 2014, 15:08   #31
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Default re: Gearbox failure in a 10-day old Mahindra Thar

Doesn't the snapping looks exactly like what happens when you test a metal piece for Young's modulus/Yield-Ultimate strength in the universal testing machine.

The material is subjected to linear elongation which exceeded the elastic limit stress and the material flowed like plastic before ultimately breaking.
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Old 24th July 2014, 11:40   #32
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Default Re: My li'l Red Mahindra Thar with some practical modifications

Originally Posted by DHABHAR.BEHRAM View Post
Dear Mooza - this is not the reason for failure. If it was, it would not have lasted for 120 kms also.

Best regards,

Behram Dhabhar
Sir, please enlighten us on the root cause. I can see, it is twisted before breaking. That means the part is soft there.... It broke when the vehicle started, under normal load. That means the failure must be gradual. Defect in the alloy composition ?
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Old 24th July 2014, 19:50   #33
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Default Re: Gearbox failure in a 10-day old Mahindra Thar

Mooza your observation is correct. This is a classical overload failure of a torsional shaft. Twisted splines and a clean cut is an indication. I suspect a goof up in the through hardening process( Ref the end view and the discoloration in the shaft middle- looks soft). Looks like this shaft may have around 20Rc (soft)against the typical requirement of around 40Rc and would have caused the failure.
Alpha1. This shaft do not see a tensile load( as in a UTM), It is a torque transmission shaft and hence the type of failure is also different.
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Old 4th September 2014, 21:58   #34
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Default Re: Gearbox failure in a 10-day old Mahindra Thar

My thoughts,
The failure is not due to Heat treatment process. If it was,then within few km run the spline of the shaft would have rounded of. I suspect a blow hole in the shaft .
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