NH 275 breaking shear bolts

MNfarmer

Member
I bought this 275 cheap because the
previous owner said it was breaking shear
bolts. I rebuilt the knotters, feeder
carriage, and put a different knotter brake
on it from a baler that had been working.
I put a new knotter drive chain on and
timed it with the marks on the baler,
adjusted the needle stop latch per the
owners manual and it still wants to break
shear bolts. What would be causing the
needles to not be completely in home
position with everything timed right? The
needles don't drift out of home between
bales either.
 
First thing I would be checking if the plunger safety stop and make sure it is moving as it should and goes to the home position because if can/will cause the needles not to be able to go back like they should and will sure as heck cause the shear bolts to shear
 
Also check the needle brake. If it is not tight and you hit a bump, the needle carriage can drop into the bale chamber and bring the the plunger stop in too - stopping the plunger and shearing the flywheel bolt. You should also IMHO be running full 540 rpms to take advantage of the flywheel inertia and lesson the recovery torque by the tractor's PTO. That alone helped us with breaking flywheel shear bolts on our New Holland 68.

With regard to timing, our 68 was in time per the marks on the knotter, but was out of time by maybe 1 chain link. I set the timing with the needle about to enter the bale chamber per the manual with the plunger face (if I recall correctly and as per the manual) about 3/4 of an inch past the needle tips. That 1 link difference was the difference between the plunger stop being on the ragged edge of coming-in and shearing a flywheel bolt.

Good luck,
Bill
 
Every time I use my NH271 that is the first thing I check and then double check it to be 1000% sure it works like it should because if it does not work correctly it can pretty much cost a guy a baler since if it does not work it and end up causing so much to get broken that the baler becomes scrap iron
 
Could it still be out of time even with the marks lined up OK? Last night my 67 was one sprocket tooth out of time and it caused the needles to not be quite home so the safety stop stopped the plunger and sheared a pin. The timing marks were close but not right on. Try advancing the knotter one tooth on the regular tooth sprocket, not the sprocket for the long link '20' chain. Is the rod that actuates the needle carriage worn in the pins so it isn't returning the needles all the way?
 
In addition to the other comments I'm guessing the knotters are all chain driven? Look real carefully at chain length and take a hard look at the chain for wear if you chain is worn or the wrong length it can mess with your timing, not much but just enough to cause hair loss and the invention of new bad words
 
You might have just enough wear in things that you'll need to jump that chain back one cog on the sprocket. I remember a neighbor had an IH 46 that he did custom work with. It ran like a Swiss watch. Another neighbor rode him until he finally sold it to him. He went all through the old thing and set everything by the book. It wouldn't bale worth a tinker's dam after that.
 
count the pitches on the timing chain they have to be exact to what the book calls for if some one shortened the chain it will be out of time. on my dads 275 we ran with the timing marks for the knotters just slightly advanced. now on his 311 they have to be lined up perfectly
 
I have an MF 12 baler which broke a few shear bolts last year. The problem was the shaft that pulls the needles into the baler somehow got bent. How that happened I do not know. Anyway, I straightened the shaft and it all works fine (except one of the knotters which is a problem for another day).
 
(quoted from post at 17:52:29 06/28/17) Check the flywheel bushings to make sure the shear bolt fits tight


Ditto- check both the flywheel center bushing (should be basically no movement) AND the shear pin bushing. Both of mine were badly worn after 50 years of baling.
 
Several things but do check the knotter brake. If it slips the needle yoke drifts forward a teeny bit which engages the safety stop, bolt gone every time.
Check hardened bushings in flywheel AND hub on shaft. If either is loose in its place OR bolt is sloppy fit in them bolts will shear.
If you don't do the shearbolt up tight enough it will shear. Use a good quality ring spanner on both the head AND the nut (self-locking, of course) and tighten to the point of almost stripping the thread - they will stay tighter and half tight bolts shear easily.
 
How much "slop" is there in the linkage that actually operates the needles. Even with a tight needle brake there can still be movement of the needles when you hit bumpy spots in the field, bringing the plunger stop into play.
 
I'd start by being sure the plunger stop is adjusted properly. Over years they can get just a tiny bit out of adjustment and only need to protrude a tiny bit more than specs to catch the plunger arm and shear the bolt. Also be sure there is no drag and a properly spec'd spring to pull the stop back out of the way. That is the simplest and easiest thing to check first.
 
(quoted from post at 16:36:37 06/28/17) In addition to the other comments I'm guessing the knotters are all chain driven? Look real carefully at chain length and take a hard look at the chain for wear if you chain is worn or the wrong length it can mess with your timing, not much but just enough to cause hair loss and the invention of new bad words

Bulk chain is cheap. I replaced all mine last year and will probably do it again next spring with ~2500 bales through it.
 
I would also recommend new chain. If you have to jump it a link, that could very well mean it's stretched that much. Chain is cheap, and easier to replace than most sprockets. I replaced a chain once on a forage harvester that we bought once that was so worn out I could practically bend it in a circle sideways. The sprockets had a fair amount of wear on them ($$$$$$) because the previous owners never replaced the main drive chain for the feed rolls.

Donovan from Wisconsin
 

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