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New Arbors In Old Deck, Finally


Roy

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Finally finished putting the new style "splined" arbor in an early model deck. Notice in the pictures I only used one spacer per arbor. With a straight blade I have a slightly higher cut. Or I can use gull wing blades and drop the cut 1/2". The blade speed is slightly lower with the new arbors due to 4" diameter pulleys instead of 3.4" diameter pulleys but it seems to mow OK. Just no "air plane" sound. Had to make a new, longer spring anchor pin with a flat side to clear the 4" pulley. Also had to put a longer belt on (84.1" instead of 82.1"). At least the deck now operates smoothly and quietly. Arbor from bottom:

Deck from bottom:

Spring anchor pin:

Deck from top:

If anyone is interested I am now well schooled on this conversion. Even have a drawing to make spacers with. That's all,
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Dave, I am confused because the driven pulley is the same size on the new & old arbors. The PTO drive pulley also looks to be the same size. Unless the newer tractors drive the BGB at a higher speed I don't know where the speed loss is. But, you are correct, if a smaller driven pulley were available it would increase the blade speed. Thanks,
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Nice job. My deck is in need of some serious attention and this winter is my time to get to it. Here come the questions Roy. 1. What is the advantage of the new type arbors? Any difference in bearings? 2. Why did you bolt the spacers to the arbor and then bolt the assembly to the deck? Could you have used the spacer like a washer and used only 6 bolts instead of 12? 3. When you installed the pulleys on the top of the deck, was there plenty of clearence between the bottom of the pulleys and the tops of the bolt heads? (I deffinately have something messed up on mine - the pulley just touch the bolt heads - and I have the arbor shafts pressed all the way up into the arbor housings)
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Roy, The difference in size of the arbor pulleys (lower pulley on the center) won't make any difference in blade tip speed as long as they are all the same size. They are connected by a single belt and therefore since they are the same size, they turn the same RPM. However, the diameter of these pulleys does make a difference with the amount of belt wrap and ability of the belt to deliver power. It looks like the center arbor is driven by a "newer" double pulley assembly - if the diameter of the lower pulley is smaller than the outer pulleys, the outer two arbors will run slower than the center. Maybe this is the issue with the lack of "airplane sound"? Hope this makes some sense. The way I check pulleys of different styles for their "effective" diameter is to put a match mark on the top of the belt and the edge of the pulley; then wrap the belt a complete revolution around the pulley and put another mark on the belt corresponding to mark on the edge of the pulley. Measure the distance between the two marks and divide by pi (3.1416) to get the diameter.
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Roy, if the driven upper pulley from the pyo belt is the same size as the older upper arbor pulley then I'd say your tip speed is the same and the lack of the sound is due to the newrer quite bearings.
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Boogity, To answer your questions: 1. "What is the advantage of the new type arbors? Any difference in bearings?" Parts are NLA for the old, original arbors. Simplicity sells a kit to replace the old arbors that has the new type arbors. Bearings are the same for the new & old. 2. "Why did you bolt the spacers to the arbor and then bolt the assembly to the deck? Could you have used the spacer like a washer and used only 6 bolts instead of 12?" The new arbors are a two-piece stamping that are bolted together. Six of the bolts hold the arbor together. Six bolts hold the arbor to the deck. 3. "When you installed the pulleys on the top of the deck, was there plenty of clearance between the bottom of the pulleys and the tops of the bolt heads? (I definitely have something messed up on mine - the pulley just touch the bolt heads - and I have the arbor shafts pressed all the way up into the arbor housings)" The pulleys just clear the bolt heads. Bottom of the pulleys are about 5/16" to 3/8" above the deck. The original pulleys were 1/4" above the deck. If you need more clearance get some 3/4" machine washers (available at Tractor Supply) and put one under each pulley (on the shaft). This will raise the pulley 1/16". PhanDad, Pulley diameter will affect the blade speed (RPM). Belt velocity = pulley radius x rpms. If the belt velocity is constant (same) and the radius is larger then the speed/rpm will be less. All three arbor pulleys are 4". The original pulleys were 3.5". Hence for the same belt velocity the larger pulleys result in lower blade RPM. D17, The new bearings are definitely much quieter. The old center arbor bearing and housing was completely shot along with the drive pulley hub (lots of runout/wobble). Thanks to all for your interest.
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Roy, I don't disagree with your formula. But this is how I see it: The center arbor rpm is determined by the PTO belt speed (belt from PTO to center arbor top pulley). Since the 3 arbors are connected by a different single belt and the pulleys contacting this belt are all the same size, they will all turn at the same rpm. However, the belt speed will be greater with the 4" pulleys vs 3.5" pulleys for a any given arbor rpm. Also, as you mentioned in your second post, the ratio of the PTO drive pulley to the center arbor top driven pulley as well as the BGB gear ratio will effect the overall engine to center arbor rpm ratio. And since you said these are the same before and after, then maybe the sound difference due the blade being higher in the deck than it used to be. And thanks for your interest and informational post.
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Bill,
quote:
However, the belt speed will be greater with the 4" pulleys vs 3.5" pulleys for a any given arbor rpm.
What you say is absolutely correct. But, since the belt is driving the arbors, and the belt speed is the same as before, the arbors will turn slower. I think we are saying the same thing. Just having trouble communicating with each other. The slower speed ratios out to 0.875% of the original speed (3.5/4). Thanks again,
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Hey Roy, I got three decks that need rebuilding. Want something to do in your spare time? LOL. By the way, the only pulley that has anything to do with the mower speed is the large one on the center shaft. If it is the same size as original, then the blades are turning at the same speed. As long as the other pulleys are all the same size, the shafts will all turn at the same speed. In that case size doesn't matter. The 48 inch mower deck that I rebuilt last summer was much quieter than before. Same pulleys. Just smoother bearings. I don't hear any wind noise from my blades.
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Rebuilt mine the same way a while back, and never really paid attention to the fact the new center pully is larger. Had a #@%$$#@$% time trying to get the old belt to fit up without knocking the PTO out of adjustment, In fact, shortly after, I figured out the pulley was larger. Don't know about yours but the kit wouldn't let me mount up the old center pulley-- it wouldn't fit. I took the deck off and have had the tiller on since. Thanks for the belt size measurement!
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Good point Rod. I owe PhanDad and apology on this one. DaveL, my top center driven pulleys (old & new) were the same diameter (5" OD). Original deck drive belt worked fine. The old pulleys will not work because they are "keyed" on and the new arbor pulleys are "splined" on.
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Roy, No apology necessary. One of the things I like most about this site, is how most everyone tries to help one another understand mechanical/electrical issues about our tractors. Every person has a different communication style and as long as everyone keeps "listening", we'll all keep learning. There's always something new to learn (or re-learn for me sometimes) every day.
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Roy, I also noticed that your deck looks somewhat like the deck I rebuilt. I put several coats of paint on it for rust protection. Problem was - every time I needed more spray paint (rattlecans), it would end up being a different shade of the orange-red. In fact, my oldest son asked me why the mower deck was painted a different color than the tractor. Guess what, same paint name, same dealer, but noticeably different. Moral of the story - buy all the paint that you will need, all at one time, and make sure it is the same part number and from the same production lot.
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Rod, It is worse than that. I tried some Rust Oleum orange. Didn't like the color and over-sprayed it with Plasticote Chevrolet Orange without waiting for the Rust Oleum to dry for 24 hours. Both paints started to craze (wrinkle finish) so I stopped putting the Plasticote on. As I was only doing the worst spots (deck needs some weld repairs), and where the arbors mounted, I wound up with 3 colors (original, RO Orange, & P Chevy Orange). Was also interesting to note that the deck was originally AC yellow. Painting is not one of my skills. :( Primarily wanted to make the deck operable/useable so did not bother to fix the messed up paint job. If and when I do the weld repairs I will fix the poor paint job.
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