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Shortening the 72 cardan drive

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#1 Eastwest


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Posted 06 September 2017 - 03:29 AM

Hi. If i instsll the Dnepr gear box into mt M72 i am told i need to shorten the drive shaft by 20mm.

Question.   What is the best way to go about this and is there any pitfalls.



#2 Peter Williams

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Posted 09 September 2017 - 07:24 AM

Easiest is to use a M-63, M-66 or early K-750 driveshaft as they are the right length. Probably hard to find though. Otherwise cut the shaft at the spline end, bore a hole into the spline end about 20 mm, turn down the shaft for 18/19mm (to take account of the material lost in the cut. You want a very tight fit. TIG weld the join. You can do the same thing at the yoke end. There's more metal there so you can arc weld it and grind it down. In both cases you want it welded by someone that knows what they are doing. I've seen photos of Russian shafts lengthened for choppers and they grind the shaft ends to a point and run a series of welds to slightly oversize and grind to standard diameter.

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