NH 451 mower - bar is bending too much

[rbargeron]

In your 3rd picture, there is a cable that has a lot of slack in it.......

That cable's function is to raise the outer end of the bar faster and higher than the inner end as the 3pt hitch arms are raised. The 451's frame rides at a constant height, with the 3pt hitch raising and lowering only the main arm and cutter bar assembly.

The cable is one adjustment point - but the short chain off the upright arm is another. When cutting along a sloped drop-off, the tip of the bar wants to be able to drop below the level of the tractor.

I have a NH 451 manual - I'll dig it out later and confirm the initial adjustment settings.

 

[Opti-Mist]

rbargeron, that is what I was looking for. I'm not familiar with the NH 451 design, but the wobble drive mowers that I am familiar with have a mechanism to accomplish as you describe. Thanks for chiming in.

 

[stowester]

I think you are on the right track with the adjustment of the cable.

Most 3pt hitch sickle mowers have some method of raising the far end of the bar at a faster rate then the near end.

1) Some are done with a lever under one of the 3pt arms.

2) Some with a cable/chain connected to the tractor in a way (usually lower then the 3pt arms) to provide extra pull to raise the far end on the bar. This is what I expect your setup is missing.

3) Some use a separate hyd cyc for it.

The idea is to have a little movement of the 3pt arms translate to a lot of movement on the far end of the bar.

I modified my IH from an type 1 to type 3.
some pics here. http://www.tractorbynet.com/forums/hydraulics/126164-problem-sickle-bar-lift-speed.html


The manual will have the key

Dean

 

[drw]

I'm looking at the manual here. That cable (that was slack when the bar was in transport position) is called the "lift cable".

There are two sections of the manual that seem to address this. I've uploaded those here:

Cutter bar flotation spring:
http://atimetofarm.com/sickle/img_9386.jpg

Lift cable:
http://atimetofarm.com/sickle/img_9387.jpg

I'll play around with these hopefully this afternoon.

 

[TimPa]

i mow with an old dearbprn 14-15. after looking at your possible adjustments, couldn't the leveling box crank on the lift arm be used to raise that side? i guess i don't know if that machine has to run level at the three point arms, or out at the bar. i'd guess bar.

 

[drw]

The manual is crystal clear in many areas that the lift arms are only to be used to level the machine, not the bar. The bar's adjustment must occur through the other means it prescribes.

 

[Opti-Mist]

The mower frame should run level by adjusting the RH lift arm via the leveling box crank.

I'd be inclined to shorten the effective length of the cable per the instructions until you achieve the amount of lift of the outer end of the cutter bar as you raise the mower from the operating position. It will be fairly snug given the 50# force to achieve a 3" deflection.

You should be on the road to proper adjustment and performance.

 

[drw]

You should be on the road to proper adjustment and performance.

Yes, I agree. I'm anticipating spending some time this afternoon poking around with what I've learned so far.

 

[drw]

The answer is what the manual calls a "gag lever".

The lift cable that we were talking about was actually to tight, which was preventing the gag lever from leaning toward the sickle when the sickle is in the operating mode. The gag lever is supposed to actually lean toward the sickle when the sickle is in the operating mode.

Sure enough, I adjusted that gag lever (with much frustration, by the way) and it worked great. It's mowing perfectly flat and straight now.

I appreciate everyone's help! Hopefully this thread will help someone else who searches for it in the future.

 

[rbargeron]

Please accept my apologies for saying I'd check the manual and then not getting back here with the goods. We had a small car crisis last week and I've been on other forums looking for parts....

drw, you are right it is the gag linkage that was out of adjustment. First, the box tube frame bar is supposed to be set at 16-1/2" above the ground when the 3-pt hitch is lowewred. Then the gag post should lean toward the cutter bar so it has 1/2" to 5/8" clearance under the inboard end.

If you PM me your email address I can PDF the owner's manual and send it to you (provided of course I don't forget)

The book also shows an extender bracket on the gag chain for use with a 9' bar. Take care, Dick B