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rsnik

Do FDT decks cut better than RBT decks...

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rsnik
I mounted the 42" deck that came with my 2010 Landlord (that I have yet to put back together) on my '92 Sovereign 18. The '92 Sovereign has funky, higher and smaller little running boards and the deck mounts and lifts with no issues. The old deck is in truly excellent, hardly used condition. I was interested in how the deck performs in comparison with the decks on my current and past RBT tractors. Turns out the old FDT deck cuts dry, wet, short and tall grass better than any deck I have ever had. Were the 60's decks the best? Did something get lost in the 70's and beyond?






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Kent
IMO, the deep decks of the 60's and 70's certainly will cut taller, thicker, wetter grass than the newer decks -- while requiring less power. However, IMO, they do not mulch or vacuum like the newest decks with the arched "wind tunnels" in them... Not sure if there's a significant difference though between how the FDT decks mow and those used on the 7000 series, for example. In fact, I think the basic shape/shell of the deck is the same.

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Chris727
The difference is more in the tractors/pto configurations than the decks themselves. The 42" deck will work different on your Sov because its spinning a different speed than it was on the FDT. Blade tip speed is key. I have a 42" deck on a B-110 which doesn't mows poorly. I can take that same deck off it, put it on a B-210 (has different size pulley on the center PTO due to single belt conversion kit) and it runs faster and cuts excellent. I think the RBT decks all ran a bit faster than the B-10, B-12 decks and as a result cut better. My 17GTH-L with "gul-wing" blade 48" deck cuts best because it has enough suck to cut the grass pushed down by the left hand front wheel, the HB-212 does not.

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Chris727
quote:
Originally posted by Ronald Hribar
i am of the opinion that the 42 inch decks cut better than 48 I personally like my 32 inch deck on my old Broadmor
Generally speaking that is true. One of the problems with the 48" decks is they tend to scalp more and not cut the grass flattened by the left front wheel as Levi points out.

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Chris727
quote:
Originally posted by wilm169
Chris you may like the gull wings, but I do not mine, will not pick up the left wheel run down. When this deck comes off again it will have flat blades on it.
We seem to have the same problem but with opposite decks. My HB-212 with flat blades has the same problem you describe, while my gull wing deck doesn't. I didn't know are these blades interchangeable, putting flat blades on will raise your cutting height. I suspect its not the blades but rather the large discharge opening is preventing sufficient vacuum to pick up the grass and cut it.

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rsnik
Chris, The stock 48" deck that came with the Sovereign 18 has a 6 inch pulley on the center spindle of the deck. The FDT deck has a 4 inch pulley on the center spindle of the deck. The FDT deck is obviously spinning one heck of a lot faster or slower with that much difference in pulley diameter.

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HubbardRA
That deck is now spinning 33 percent faster than the RBT deck. Blade tip speed is getting pretty fast, so watch out. Blades will come apart if spun too fast, because of shock wave generation.

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dentwizz
Actually blade disintegration is much less a factor than arbor mount fatigue and deck shell fatigue. I used to overspeed my push-mowers when I was younger and more foolish to get more performance out of the 3 hp briggs(22" blade). I stopped that practice after the decks fatigued in a year and a half, including new from the factory replacement decks.

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rsnik
The PO of this deck passed unexpectedly, a coworker bought the tractor from the widow and sold it to me, so no history. I did not know why the spindles had 6 holes and only 3 bolts. Ray explained that FDT deck spindles are fastened with 3 bolts. I did not know why the spindles looked brand new but had no zerk fittings. A recent post explained that new replacement spindles have sealed bearing and no zerk fittings. My guess was they were off brand spindles cobbed on. At any rate, when you spin the blades by hand with the deck off the tractor you hear no bearing noise. The blades spin freely and almost silently. I consider a reasonable amount of bearing noise to be normal, so I thought something must be wrong. Nope. Sealed bearings spin easily and almost silently. No wonder I thought this FDT deck was way better; it is super quiet and the blades are being overdriven to super killer speed.

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lumpy
I have the best of both worlds now , I have on old 42 inch deck off a 3416s on my 18hp sovereign, I removed the new splined arbors and mounted them on the older deck, both were 42" I then retrofitted all the deck hardware including rollers , I swear it cuts better at a slower rpm than before. so I have an old shell with all newer parts , same pulley as before so it should be spinning at the same speed as before but cuts much better as slower speeds. gotta be something said for the old deck design. oh and it is about 1/2 as quiet now. needless to say I am quite happy. I had to swap due to the 18hp deck cracking and looking like swiss cheese, I believe the old deck is a thicker gauge of iron to boot.

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jmhusby
Have a question and a comment. What does RBT and FDT stand for and whats the difference. Comment is we have a 54" on our Prestige and a 48" on our 918 Allis. They both cut about the same but the Prestige cuts faster and the height is easy to set. Been reading the posts on setting the older decks so will have to try it. Regardless of age still think the Simplicity cuts the grass better than the others. Haven't seen any yard looking better than ours.

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Chris727
quote:
Originally posted by jmhusby
Have a question and a comment. What does RBT and FDT stand for and whats the difference.
RBT= Running board tractor (1971 and newer) FDT= Foot dragger tractor (1970 and earlier) In reality all of the left hand discharge 42" and 48" decks have the same basic design principle. I own and have cut with all of the older Simplicity decks. My 1992 sov deck is just as heavy as the old 48" on the AC HB-212. Guage of material was likely never changed. With sharp blades and good rollers most any of these decks will cut very well.

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steve-wis
For whatever reason, of the four mowers I have used in the last few years, the best looking lawn comes from my 1959 Wonderboy with the three blade 32 inch deck. My 616 yeomans are a close second. My 810GT Allis was the worst, although I didn't mow much with it being my yard is so small, and it could use some work. Having said that, I agree that the worst Simplicity is better than the best of anyone elses. Funny side note....my employer hires a lawn service, and the guy mows with a John Deere tractor. Have to say it does a pretty nice job, and the lawn always is striped pretty nice too. Steve

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Vassal
quote:
Originally posted by HubbardRA
That deck is now spinning 33 percent faster than the RBT deck. Blade tip speed is getting pretty fast, so watch out. Blades will come apart if spun too fast, because of shock wave generation.
I think blade speed is the key here, and when using OEM blades, the more the merrier as far as I'm concerned. I have 100% percent confidence in the OEM blades at this speed, little to none in the Chyneez replacements. However, I do wear steel toe boots and don't have to worry about kids in the area(ever):D

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larry8200
I think lawn flatness is everything. If it's like a golf course, 48" decks will do fine, if it's all lumpy from frost heaves and lack of landscaping, well, 22" push mower might be the ticket. Sharp blades are the key always. I have yet to get a better cut with my feet dragging. :D:D:D

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