I have been making these for a while now, took awhile to get the bugs worked out, had the levels speacial made with the center solid so I could set 3 ball bearings in to take away friction. The hardest part was making sure the hooks hang the same distance from the center and the hooks and chain has to be the same weight. Makes the cutter run alot smother and saves those gear boxes and seals. Any thing that spins need to be balanced, and yes you can take a pair of good scales and do the same, but this takes no batteries.
Rotary Cutter Blade Balancer
- Thread starter DThrash
- Start date
Good Idea! I have always used an electronic scale, that I picked up at a bolt business, that was going out of biz. Yours is simpler, and don't use no 'lectric...
85Hokie
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I like it ! Brilliant too.
Even the slightest gram will show up!Question for you.....you add weight on the "short" side? Or grind off the heavy side? If you were to add weight - and it would be hard to do, the centripetal force would still not be correct,since the weight would not be out on the cutting tip. I would imagine that grinding the edge of the heavy blade would be the only practical answer.
I bet it is a bearing saver too!
Back in the old days of sharpening lawnmower blades with a file, I was always told to count the number of licks that were used when filing. I prefer to sharpen blades with a nice file as opposed to a grinding wheel - even though it is a hellva lot more work!
I wonder how close the typical blades are from the factory!
I gots a coupla sets of new blades, I'll weigh them and see, maybe sunday...I like it ! Brilliant too.
Question for you.....you add weight on the "short" side? Or grind off the heavy side? If you were to add weight - and it would be hard to do, the centripetal force would still not be correct,since the weight would not be out on the cutting tip. I would imagine that grinding the edge of the heavy blade would be the only practical answer.
I bet it is a bearing saver too!
Back in the old days of sharpening lawnmower blades with a file, I was always told to count the number of licks that were used when filing. I prefer to sharpen blades with a nice file as opposed to a grinding wheel - even though it is a hellva lot more work!
I wonder how close the typical blades are from the factory!
Yes I always grind off the heavy one. The blades that I used in the pics came off a 15' Rhino that I bought used. Those blades are to far gone to be fixed. The gear box they were on was leaking [wonder why]. The way I explain it is, if you drop the stump jumper off and bolt a blade to each side, now you have one big blade. The factory balances the stump jumper and it only makes since to keep those blades close. I know those big cutters can take abuse for a long time but those smaller 40 and 60 HP gear boxes catch H.I like it ! Brilliant too.
Question for you.....you add weight on the "short" side? Or grind off the heavy side? If you were to add weight - and it would be hard to do, the centripetal force would still not be correct,since the weight would not be out on the cutting tip. I would imagine that grinding the edge of the heavy blade would be the only practical answer.
I bet it is a bearing saver too!
Back in the old days of sharpening lawnmower blades with a file, I was always told to count the number of licks that were used when filing. I prefer to sharpen blades with a nice file as opposed to a grinding wheel - even though it is a hellva lot more work!
I wonder how close the typical blades are from the factory!
ShaunBlake
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I like your 'gizmo' as well. I particularly like that it requires some precision in fabricating the level, and necessitates close matches in the weight of add-on parts. And I can see a benefit of having blades of very close weights. (My R322T has three blades, so it would require some extra steps to balance them, but as you note, the gearbox will be happier.)
It seems to me that the uniform weight of the blades is important, but is #3 on the list of blade balance; blade shape; and matching weights.
IOW, if one of the same-weight blades is a little bit unbalanced, that will be far more damaging than one of them being a little heavier, but all of them well balanced. Don't you agree?
And if one of the blades is out of shape -- say, bent up a bit -- wouldn't that also be more upsetting to the momentum than dissimilar weights?
I hope I'm not coming across as nay-saying your invention. In fact, I admire it greatly! And I hope you invent equivalent devices for balancing blades and checking their trueness (if I can create a word). I am not at all satisfied with the typical balancer that consists of a cone sitting on a nail. Those are not even remotely close to the precision you've designed into your device.
Kudos!
It seems to me that the uniform weight of the blades is important, but is #3 on the list of blade balance; blade shape; and matching weights.
IOW, if one of the same-weight blades is a little bit unbalanced, that will be far more damaging than one of them being a little heavier, but all of them well balanced. Don't you agree?
And if one of the blades is out of shape -- say, bent up a bit -- wouldn't that also be more upsetting to the momentum than dissimilar weights?
I hope I'm not coming across as nay-saying your invention. In fact, I admire it greatly! And I hope you invent equivalent devices for balancing blades and checking their trueness (if I can create a word). I am not at all satisfied with the typical balancer that consists of a cone sitting on a nail. Those are not even remotely close to the precision you've designed into your device.
Kudos!
As far as a bent blade goes, I don't think it makes a heck of a lot of difference, seeing as how even on a brand new set of blades, on a brand new SJ, with new pins, I measured about an inch of up and down movement at the blade end, which does 90% of the cutting. My guess would be, if you can see that a blade is bent (ie: stack the 2 blades on each other), then, just replace the set...
I use a magna matic blade balancer, on my dixie chopper blades, it has a finger or arm that can detect bent blades. In 20+ years of mowing lawns professionally, I have only 1 set, with one bent blade, out of the 12-15 sets of blades. I am the only operator, and I can only remember hitting one chunk of concrete, in tall grass that could have caused that bend, and it is only about a eigth to a quarter inch out. I marked it, as bent, but still am going to use it as a rough area blade, as it is still perfectly balanced...
I use a magna matic blade balancer, on my dixie chopper blades, it has a finger or arm that can detect bent blades. In 20+ years of mowing lawns professionally, I have only 1 set, with one bent blade, out of the 12-15 sets of blades. I am the only operator, and I can only remember hitting one chunk of concrete, in tall grass that could have caused that bend, and it is only about a eigth to a quarter inch out. I marked it, as bent, but still am going to use it as a rough area blade, as it is still perfectly balanced...
ShaunBlake
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Well, no... and yes. The blades aren't stacked; each one is on its own shaft, and they are driven by a belt.
Sounds like Shaun is talking about a finish mower with three blades instead of the rotary cutter that Dthrash started the thread on. With a three blade finish mower, balance of the individual blades is #1. The deck won't give a hoot if one blade is 3 ounces heavier or you run one Gator blade.
For the optimum matchup on a rotary cutter each of the two blades should weigh the same. DT's balance beam does that. There is another component that the level doesn't address as someone was getting at. It may not affect the mower much, but think about this.
With the level, the blade weights will match BUT the weight distribution of each blade will not necessarily be the same. If one blade is slightly heavier at the cutting end while still being the same overall weight as the other, it will unbalance the cutting assembly when it spins but not when it is static on the level. This can happen if the sharpening isn't quite straight (a little more trimmed back at the tip on one blade, for example).
After making certain both blades weigh the same, you'd need to solidly support one end of the blade and weigh the other.
If you ever balanced a ceiling fan you'll understand. The stick-on weight doesn't only need to be on the correct blade - it needs to be a certain distance from the tip.
For the optimum matchup on a rotary cutter each of the two blades should weigh the same. DT's balance beam does that. There is another component that the level doesn't address as someone was getting at. It may not affect the mower much, but think about this.
With the level, the blade weights will match BUT the weight distribution of each blade will not necessarily be the same. If one blade is slightly heavier at the cutting end while still being the same overall weight as the other, it will unbalance the cutting assembly when it spins but not when it is static on the level. This can happen if the sharpening isn't quite straight (a little more trimmed back at the tip on one blade, for example).
After making certain both blades weigh the same, you'd need to solidly support one end of the blade and weigh the other.
If you ever balanced a ceiling fan you'll understand. The stick-on weight doesn't only need to be on the correct blade - it needs to be a certain distance from the tip.
ShaunBlake
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Yep, chim put it very well.
And yes, I do have a finish mower, but ignore that and just consider the momentum that chim is addressing.
And yes, I do have a finish mower, but ignore that and just consider the momentum that chim is addressing.
I agree with Chim's theory on static vs dynamic balancing, but on a BH, you can end up splitting hairs, with a sledge hammer... As long as mine weigh the same, i'm satisfied...
You put it very well. I never went to the trouble to balance them like a ceiling fan and probably never will. I think the gear box will probably take that. I have proven around here to several people after they sharpen the blades about 2 or 3 times they usually need balancing. On pull behind big cutters you don't feel the vibration as much as 3 point. I know you are going to feel some vibration, but the more you can get rid of the better you are. With these you still have a nice level made by Port Austin in MI. 2 in one.