OT optimal cutting speed and feed rate for lawn mower blades?

[Freedommachine]

I'll provide a quick update on this; I pulled the deck off and removed the gearbox (peerless 1100-009) to replace this bearing on the output shaft:

I checked the gear box ratio at .740:1. I decided that it would be much easier to change the gear ratio in the box rather than make new pulleys. I downloaded the parts diagrams for 42 different versions of this gear box and searched them all for an acceptable gear set. The only set I could find that peerless still has available (obsolete, 5 left in stock) is a 1.15:1 ratio. This will bring me up over 18,000sfm blade tip speed - it isn't the 20,000 I was hoping for but it will still be a 6000 sfm increase over where I am now.

I ordered the gears today, I will report back when they arrive.

 

[john.k]

I got a 7ft slasher driven by a 60hp tractor that I used to do the back with ........the blades are kind of triple jointed so they can fold back if I hit a stump.........or piece of scrap iron.......anyhoo,they are 1" thick and worn to a round edge ,which is more or less indestructable...............I havent done the back in over a year now ,simply because no one has complained to the council........fuel costs money ,causes climate change ,yada yada.............and the tractor doesnt have power steering ,so its plain hard work.

 

[Freedommachine]

This is one of my other current side projects, 9ft sickle bar mower.





Grandpa caught a small dog wood sapling or something with it. Locked up the knife bar and mangled one of the drive plates. It'll be getting rebuilt once Messnick's actually gets my new parts delivered. Really cool mower, I just wish it wasn't so fragile, it's always shaking itself apart. Hiking through a hay field searching for a lost guard and blade clip gets old lol.

 

[eKretz]

Those are cool. I want one.

 

[Gearclash]

@Freedommachine -- I don’t know what you ordered for replacement parts there, but I would recommend using the NH guard that is already on that bar, or stub guards (no point on them, the sickle protrudes past the end of the guard). For sickle sections, I highly recommend a good quality top serrated section. Don’t use smooth or bottom serrated sections.

 

[fish123]

WOW, you guys have some big powerful mowing gear!
We have "his & hers" equipment here.
Wife uses the 30 year old Diesel Kubota G1800S for trimming sections of the 3 acres that my larger mower won't fit through - she likes the old style steering wheel.

Over the decades, I have welded up the stamped steel deck on that thing so much, very little of the original deck remains.

I use a 5 year old Diesel Kubota ZD1211.
It was the most HP available at the time w/o requiring the DEF and DPF and other emissions crap. Steel plate welded up deck is very durable.

I try to only mow in "J" months here.
However, SWMBO becomes irate when the dogs can't be seen in the yard, so occasionally other mowing months are added.

 

[DrHook]

This is one of my other current side projects, 9ft sickle bar mower.

View attachment 410966
View attachment 410967


Grandpa caught a small dog wood sapling or something with it. Locked up the knife bar and mangled one of the drive plates. It'll be getting rebuilt once Messnick's actually gets my new parts delivered. Really cool mower, I just wish it wasn't so fragile, it's always shaking itself apart. Hiking through a hay field searching for a lost guard and blade clip gets old lol.

be thankful the blades are BOLTED on- the one we had "back in the day on the farm" had riveted blades, and took forever to change.

 

[MwTech Inc]

it's always shaking itself apart.

New Holland shouldn't shake itself apart, if it is somethings wrong.
Make sure your clips are set right. Anyone do some funky repairs on the blade system?
Grew up with and still have my Dads NH sickle, jillion hours on it, still smooth.

 

[Freedommachine]

@Freedommachine -- I don’t know what you ordered for replacement parts there, but I would recommend using the NH guard that is already on that bar, or stub guards (no point on them, the sickle protrudes past the end of the guard). For sickle sections, I highly recommend a good quality top serrated section. Don’t use smooth or bottom serrated sections.

I probably shouldn't have said that I was rebuilding it; repair would be a more accurate description.

Thank you for the info about the knife sections. The parts book called for either smooth or bottom serrated, so I ordered the latter. The knife sections on it now are a mix of smooth and top serrated; now I see why.
I will figure out how to return them and get top serrated instead. Again, thank you for this info!

Whenever I can squeeze in time to work on equipment, I like to go all the way. I innitally wanted to rebuild the bar with new guards, wear plates, knife sections and the newer style adjustable knife clips. Unfortunately it would have cost nearly $1000 to do it - even more if I were to use all NH parts.

This mower is primarily used for cleaning up the perimeter of the fields and a few tight places that are too difficult to reach with the haybine. It catches the occasional fallen limb, grape vine, thorn bush trunk and other hedgerow vegetation - so in this case; guards, clips and knife sections are better replaced as they get damaged.

My current plan is to replace:
crank bearings
wear plates
2- knife clips
11- knife sections
1 mangled drive plate
There are probably a few other small things I cannot remember.

Then reshim all of the knife clips and bend the guards back straight so that the blade sections ride properly on the ledger surfaces.

be thankful the blades are BOLTED on- the one we had "back in the day on the farm" had riveted blades, and took forever to change.

Thats for sure! There are 35 knife sections with 2 bolts each. Dealing with all those rivets would be tedious for sure!

New Holland shouldn't shake itself apart, if it is somethings wrong.
Make sure your clips are set right. Anyone do some funky repairs on the blade system?
Grew up with and still have my Dads NH sickle, jillion hours on it, still smooth.

There haven't been any rigged sort of repairs that I can tell. Just a general lack of maintenance and a hard use application. I plan to go heavy on the blue loctite putting it back together.

Looks like we have a number of members experienced in the art of maintaining old farm junk. I have a decent backlog of it to get through so it's nice to know that I can ask questions. After the sickle bar mower comes wheel bearings, linkage adjustment and PM on a bobcat 553. Then building an elevator, followed by steering clutches in a JD 350C dozer.

 

[MwTech Inc]

cleaning up the perimeter of the fields

Of course used it for that too, but she mowed many a field of hay. But always freshened it up before hay season rolled around.
Normally was pulled with a Allis Wd.........ah...memories.

 

[DrHook]

Of course used it for that too, but she mowed many a field of hay. But always freshened it up before hay season rolled around.
Normally was pulled with a Allis Wd.........ah...memories.

"WD" ...shee-it, most folks wouldn't know what that is!
(Grandpa called them "Almers-Chalmers")

 

[DouglasJRizzo]

I'll provide a quick update on this; I pulled the deck off and removed the gearbox (peerless 1100-009) to replace this bearing on the output shaft:

I checked the gear box ratio at .740:1. I decided that it would be much easier to change the gear ratio in the box rather than make new pulleys. I downloaded the parts diagrams for 42 different versions of this gear box and searched them all for an acceptable gear set. The only set I could find that peerless still has available (obsolete, 5 left in stock) is a 1.15:1 ratio. This will bring me up over 18,000sfm blade tip speed - it isn't the 20,000 I was hoping for but it will still be a 6000 sfm increase over where I am now.

I ordered the gears today, I will report back when they arrive.

Nothing like some good old fashioned hot rodding to get what you need!
If 18k SFM isn't enough, you could always call the local gear house and have a set made.......

Of course you might also want this..:



For a little "extra" SFM...

 

[eKretz]

"WD" ...shee-it, most folks wouldn't know what that is!
(Grandpa called them "Almers-Chalmers")

My gramps had one too. I used to mow his back field with it when I was a kid. I was fond enough of it and the memory that I bought this surface plate as soon as I saw it.

 

[EmGo]

Of course you might also want this..:
View attachment 411053

Are you a friend of Bottlebob ? That's not much of a hiding job, BB would laugh

 

[eKretz]

Are you a friend of Bottlebob ? That's not much of a hiding job, BB would laugh

I tucked mine into where the factory spare tire used to be... . That was a fun car.

 

[Freedommachine]

Nothing like some good old fashioned hot rodding to get what you need!
If 18k SFM isn't enough, you could always call the local gear house and have a set made.......

Of course you might also want this..:

View attachment 411053

For a little "extra" SFM...

I dont think that little diesel would live too long getting hit with the giggle juice. It would be cool to see though!

 

[EmGo]

Kids today ! Most everybody who did alt.machines knows bottle .... good machinist. In fact excellent machinist ... but the entertaining part :

Street Race Stories

To All: I was just turned on to this board a few days ago by Groucho, when John Goms started posting like a Phoenix rising from the dead. I hope...

www.jalopyjournal.com

I wonder if we can lure him over here ?

 

[MK ULTRA]

Your SFM depends on “how fast the lawnmower is going over the grass” or “Feed Rate” You don’t seem to have that data in your calculation. So if it’s not cutting good slow your speed across the grass or your “feed rate” right down. But your blade RPM is important also but you must include Feed rate in your calculation.

 

[DouglasJRizzo]

I dont think that little diesel would live too long getting hit with the giggle juice. It would be cool to see though!

Methanol/water injection for diesels!

 

[Freedommachine]

Your SFM depends on “how fast the lawnmower is going over the grass” or “Feed Rate” You don’t seem to have that data in your calculation. So if it’s not cutting good slow your speed across the grass or your “feed rate” right down. But your blade RPM is important also but you must include Feed rate in your calculation.

Do you mean that cut quality depends on ground speed? If so, yes I agree.

However, SFM has nothing to do with ground speed. It is a unit of measurement for 'cutting speed'. On a band saw, this would represent blade speed. On a lathe or mill, it would be measured from the o.d. of the material or tool respectively.

On a rotary mower; SFM is a measurement of blade tip speed; this is independent of ground speed, aka feed rate. A 18" blade must spin at a higher rpm than a 22" blade to achieve the same SFM - this is why RPM is not a good unit of measure for recording cut data.

Surface feet per minute gives us a constant that we can apply to all traditional rotary finish mowers. 12,000 is too slow, 16,000 seems to be acceptable and common. I will find out what 18,500 looks like and let everyone know.

Higher blade speed = the ability to achieve a higher ground speed, to an eventual point of diminishing returns of course.