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| While the weight being carried on the cutter bar may have an impact on the longevity of the tie bolt, it alone is not the reason for the failure. This is strictly my opinion why the rear tie bolts fail. If you look at the end cap where the tie bolts go through you will see the width of the cap is about 5/8" narrower than the front. When you tighten a bolt you are actually stretching the bolt and are relying on the stretch to hold the nut tight. The tie bolts are 3/4" rod with coarse threads cut on each end. In reality you end up with a 3/4" rod in the center of the bolt and 1/2" rod where the threads are. So where would you think the stretch of the bolt is going to happen. It happens in the place of least resistance which is the threaded area. The front tie bolt has about an inch of threads between the nuts where the stretch can happen. The rear tie bolt has about 3/8" where the stretch can occur. Both bolts are going to stretch the same amount but the stretch in the rear tie bolt will be concentrated is a much shorter length of the tie bolt threaded area when compared to the front tie bolt.
That alone would not cause the rear tie bolt to fail. After all the right side has the same setup and all the failures I have seen are on the drive side. I believe the added torque of the drive on the first module is also exerting a pulling apart force on the tie bolt. The strange part about the problem is that it is more prevalent on 9 ft machines than the 10 ft machines. And on top of that, the problem is on only a few machines. On the ones I have seen fail, header floatation was not an issue at all. I set all machines all the light side when attached to operators tractor.
I had one machine that failed that tie bolt 4 or 5 times and it would fail with less than 20 acres of use. I thought I would test my theory about the bolt stretch and upon reassembly I installed 5 additional washers on the rear tie bolt so the nuts were in the same position as on the front tie bolt. The machine has now completed three seasons without another failure. In fact none of the units I have done has failed again. Use only the correct washers and nuts and follow the procedure from NH on reassembly.
I would also replace the bottom gear box seal. When the cutter bar separates it opens the gap between the bottom gearbox hub and the hub on the drive shaft. This allows material to enter below the gear box seal. Have only had two gear box failures on the 9ft machines but both machines had a previous tie bolt failure. I now at least check to see if material has packed around the seal.
Edited by mike10 10/25/2015 09:10
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new holland h7230 problem
