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Dutch

Sickle Speed

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CleanBee
Wasnt there something in the owners manual about setting the tractors speed for operating the sickle mower by doing something like: Put the tractor in second gear and have someone walk next to it. Adjust the rpm so they walk at a normal pace. This is the rpm to operate the mower at. I recall reading something to that effect in one of the manuals that my dad had. I recall it had me thinking how do they know what speed pully you have in it. Unless it dictated that earlier. Dan

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dlcentral
There are warning decals all over my AC bar not to run eng more than 1/2 speed.More like 1/4 speed by me is plenty fast enough.It takes very little hp to run them as they were on the old 700's,,Also to mow properly they must have a forward lead at the outward edge,otherwise in thick hay they will plug or ball up,,.

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Dutch
If you’ve added a sickle bar to your tractor, make sure it’s not running too fast. Had someone who wanted to trade a single belt sickle for one of my planetary drives. Upon inspection, the owner had used the large PTO pulley to power the single belt sickle. It was running too fast. After adding a smaller PTO pulley, his single belt sickle performed just fine. Sold him some new parts, blades and rock guards instead of trading.

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BradW
Just another thought, NEVER run over half throttle otherwise things WILL break! There are expensive to fix so keep that in mind. Another resource is the link below to the "Operation Guide". -BradW[A href='"Operation manual for 46" sickle mower"']"Operation manual for 46" sickle mower"[/a]

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CleanBee
Hi all, My little brother just e-mailed me with a clarification straight from the manual: This is what the Manual had to say: Set the tractor engine speed to give a ground speed equal to a fast walk when the tractor transmission is in 3rd gear. Mark this point on the throttle control lever quadrant and DO NOT EXCEED THIS SPEED OR SETTING IN ANY GEAR. Have a good one Dan

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ka9bxg
I've used mine a few times and I run it just above a idle on the small pulley.Much faster than that will cause parts to go flying.I have a bit of time before I could use it.We just got another coating of snow on the ground.

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RATobin
CleanBee, What manual did he look in? My decals say do not operated above half throttle. I do not know of a B series or equivelent that has a throttle lever quadrant. A/C farm tractors have throttle lever quadrants but 3rd gear even at an idle on a larger machine would be faster than a fast walk. Too much rpm will damage the mower regardless of ground speed, too slow of ground speed and the cut material will fall poorly and lead to clogging, too fast and the mower can't keep up, ground speed will need to be adjusted according to the material being cut. Dutch, Engine rpm dictates strokes per minute (720spm @ 1800 rpm/half throttle) with the recomended pulley of course. Granted the same rpm with the improper larger pulley will increase the spm dramatically. Rob

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MPH
Hi all again, Personally, I will run my sickle mower at a lower mid idle determined by my ear. Not to fast and on the small pulley. I guess this post should have ended there. But, as usual, things always go further than that here. lol About the manual, it is one that AC supplied to the dealers for set up of the sickle mower for the b-series tractors. It is a full 4 page with alot of writing. My dad has an entire libary of original manuals, inner office memos, advertisement, ect. He collected alot from AC while he worked there. For the question about the quadrant, all I have to say is that it was quoted from the manual, I didn't write it. Guess you would have to do quite some reserch to find who did write it, and ask them. Chances are either they wont remember or their not living anymore. As for the reference to the ground speed, again, this is what the manual said. The main reason I listed what the manual said was for a bit of humor as to how AC went about explaining a rpm setting back in the mid sixties. I really didn't expect anyone to use it as a reference. I figured people would follow the logical post about less than 1/2 idle. Take care, Dan

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Dutch
Peter, Very valid questions and opinions. To me, a sickle bar stroke is back and forth (a complete cycle). Perhaps others would disagree. I'm only addressing Simplicity sickle bars. To the best of my knowledge there are only 2 types (planetary and non-planetary). On the non-planetary type, 1 sickle pulley rotation = 1 complete sickle bar stroke (I examined it). The planetary type has a 3+:1 ratio. 3+ rotations of the input pulley (from the PTO) = 1 sickle pulley rotation which = 1 stroke. Pulley ratios can be calculated mathematically, or visually. To calculate visually, mark the BGB output pulley, and mark the sickle bar pulley. Rotate the BGB output pulley until the sickle bar pulley rotates 1 full turn. If the BGB pulley rotated twice that's a 2:1 ratio, if the BGB pulley rotated 3 times that's a 3:1 ratio, etc. Since the BGB has a 1:1 ratio with engine speed, 1 BGB pulley rotation = 1 engine RPM. So calculating engine RPM for 720 SPM should be easy.

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Kent
Looking at only the pictures of the old ones, it's pretty clear that one RPM of the final drive pulley on the sickle bar's pittman is one stroke... the variables are: 1) Left BGB pulley size 2) Center PTO pulley size 3) The two pulleys on the sickle bar drive itself So, Dutch's point on putting a sickle bar on a different tractor is well made. 1. The BGB pulley is a slightly different size between early (B-seriew) and later, cone clutch PTOs, unless I'm mistaken. 2. The center PTO pulley for B-series tractors had an outside groove that was very small (2" or 2-1/2" ?? to drop the ratio below 1:1). Since a cone-clutch setup doesn't have this small pulley, I'd guess you'd be overdriving an old-style sickle bar by close to 3:1, if you tried to put it on a newer, cone-clutch tractor. 3. I have no personal experience with these, so I'll stop there -- but I just went through the exercise of recalculating gear ratios when I converted my B-210 to a Sundstrand with cone clutch... I had to almost double the size of the pulley on my mower deck to get the same blade RPM -- and it used to drive off the larger center PTO groove, not the small outside one.... Kent http://www.simpletractors.com/images/sickle_bar/sb_fig4.jpg

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JeffG
Dutch: First,I appreciate your compliments...from someone as knowledgeable as yourself, it is indeed high praise, and I thank you. Second, I'm glad you physically confirmed that one sickle pulley rotation = one complete, "back and forth" cycle of the non-planetary sicklebar. You did what I was too lazy to do-LoL. Third, I appreciate your confirmation of how the ratios work, mathematically, and it's an excellent point that visual confirmation of ratios may be the simplest, most "error free" method, IMHO. However, on the topic of "what constitutes a stroke," (sounds more like a lockerroom conversation, no?) while I tend to agree with you that a stroke should be a complete, "back and fourth" cycle, it seems that the nomenclature used to describe the "Otto Cycle" engine (our common, 4-stroke auto engine) is against us. In a "four-stroke cycle" engine, the piston "strokes" up and down four times, and in a "2-stroke cycle" engine, it strokes twice (once each way) per cycle. If we were to be consistent with this precedent, it would seem then that EACH traversing of the blades, until they reverse, is a complete stroke. Somehow, conceptually, I don't think this seems correct to me, but again, the 2-stroke/4-stroke engine terminology seems to be against us.... So I think this in itself is still a potential source of confusion, (by a factor of 100%!) which might possibly be resolved from some text from the Simplicity literature available.... Any takers? Kent: excellent analysis of the potential "overdrive" ratio on the coneclutches...as I've never even seen one, or the planetary sicklebar drive, all I can say is "sounds right!" However, I cannot imagine how you were able to deduce, from pictures alone, that "...it's pretty clear that one RPM of the final drive pulley on the sickle bar's pittman is one stroke...." Now, Dutch confirmed your analysis, physically, of the 1:1 ratio b/w the (non-planetary) sickle pulley RPM and sicklebar SPM (again, ignoring for the moment whether a stroke is just movement one way, or a complete, "two-stroke" cycle). So I don't doubt you. My question is, how in the world can you tell this from pictures? I am always fascinated at others (inventors, technicians, etc...) ability to "intuit" info that I might see only after tedious, physical inspection. And again, Dutch confirmed it and you obviously dealt successfully with these issues with your hydro conversion. So give--how do you do it? Peter

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Dutch
Rob, I don’t know what manual Dan’s brother is quoting, but my manual (TP-1651827) has the same exact wording. ”Set the tractor engine speed to give a ground speed equal to a fast walk when the tractor transmission is in 3rd gear. Mark this point on the throttle control lever quadrant and DO NOT EXCEED THIS SPEED OR SETTING IN ANY GEAR.” Interestingly, other manuals appear to give contradictory instructions. For example, check out the recommended engine RPM for sickle operation in speeds for hydro and speeds for gear transmissions. Both list engine RPM at 3/4 throttle NOT 1/4 or 1/2. Engine RPM must be high enough to provide sufficient power and afford proper cooling. After that, the only important consideration is sickle bar strokes per minute. The planetary units have a built in 3.25:1 gear reduction, while non-planetary units rely on the operator using the proper diameter pulleys.

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RATobin
Dutch, It seems there is a lot of inconsistency with the different operating instructions. I understand what you are saying about needing adequate engine rpm to produce the needed power and cooling. Sickle mowers do not require much power to operate and therefore the motor works less and runs somewhat cooler assuming it is maintained properly. You make it sound like the planatary gearbox solves over speed problems but the planetary gearbox is still driven by a belt and pulley,so it still rely's on the operator using the proper diameter pulleys. Change the pulley size and you change the speed of the bar. Granted the planetary setup may have a different engine rpm recomendation. I have never measured all the pulleys involved running the non-planetary unit to figure the reduction, I have never felt the need. You said " Engine RPM must be high enough to provide sufficient power and afford proper cooling. After that, the only important consideration is sickle bar strokes per minute." I agree with the first part but you seem to seperate engine rpm and spm, they are tied to each other. With a given pulley set you change the rpm you change the spm period. Assuming Allis did there homework they recommend 720 spm @ 1800 rpm, 1800 rpm is half throttle on an engine rated at 3600 rpm, if all recommended pulleys are used the spm will be aproximately 720. If one ran the engine at a higher rpm they would need an even smaller pulley on the center pto to keep the spm close to spec. This is assuming that the 720 spm recommended in the manual is actually correct, we all seem to be findind contradictions in the manauls. I am not trying to be difficult, I just want to be as clear on this issue as possible, I think we both think basically the same thing but are saying/typing it different, I don't know about you but when I type I try to be as concise as possible and that does not always seem to get the nescesary details out. In a verbal conversation it would be easier to be clear and complete but in written form is leaves more to interpretation (in my opinion) Rob P.S. this did not seem to concise!

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CleanBee
Hi Dutch, I'm not sure what manual it is either. My little brother has all of my Dads paperwork at his fingertips. I think, instead of him just reading these posts and emailing me when he wants to voice something, he should become a member like the rest of us. Hope you read this David. Dan

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Dutch
Rob, I believe we are saying the same thing. But, you stated, “I have never measured all the pulleys involved running the non-planetary unit to figure the reduction, I have never felt the need.” When someone bought a brand new sickle for their tractor, I’m sure the Simplicity engineers figured everything out and supplied parts and instructions for that particular application. However, when someone installs a used sickle, THEY have to do the calculations for themselves. For example, with a engine set at 1/2 throttle (1800 RPM) a 4” PTO pulley will drive a 6” sickle bar pulley at 1200 RPM (4 / 6 = .666 1800 * .666 = 1200). 1200 strokes per minute is too fast. You would have to reduce engine speed to below 1/3 throttle (1200 RPM) using 4” and 6” pulleys to achieve 720 strokes per minute. 1/3 throttle will effect power, ground speed, and possibly cooling. All I’m saying is, IF anyone has trouble with their sickle bar, it may be a good idea to calculate pulley ratios. Since you’re not having trouble, just ignore my suggestion.

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treegunman
Dutch: I've decided not to let the fact that I've never even mounted my sickle bar on my tractor keep my from adding my .02 here--LoL! I have spent countless hours behind a Jari sicklebar, however, so I can tell when one is running correctly (you don't have to keep stopping to clear the "wiregrass", and it doesn't keep stalling). My Firs Q: Aren't you making an assumption, in your mathematical formula, that ONE (sicklebar plley) RPM = ONE SPM? IOW, there is no documentation re: how many strokes one revolution of the sickle's pulley actually creates, and I would not be surprised if it is not even consistent between the planetary type and the older type. To be clear on this, I agree with the following formula, re: PULLEY SPEED. But as I read it, that's ALL it calculates, not SPM. Specifically, you correctly state: (4 / 6 = .666 1800 * .666 = 1200). But that 1200 is "driven pulley," or "sickle pulley" RPM, and NOT NECESSARILY SPM...am I right? IOW, Sickle pulley RPM and SPM may not be in a 1:1 ratio. And if it's off by a factor of one, in either direction, you end up with a SPM rate of either 600 or 2400. And what if one sickle bar pulley RPM = .75 SPM, or any other percentage of one RPM? That's why, IMO, this has to be taken into consideration. Of course, I could go spin my pulley and count the strokes, but my bar, not being used for years, is more than a little stiff, I'm sure, so I didn't bother. My Second Q: Is everyone counting strokes consistently? Is a stroke ONE way, or a complete, (2-stroke) cycle? Would this ALONE account for some of the confusion, i.e., what looks like 1200 SPM (again, assuming one RPM of the sickle's pulley actually = One SPM, in your formula example) could really be a more acceptable 600 SPM? If you've somehow explained how you know that one sickle pulley's RPM = one SPM, I apologize. Just trying to understand this Peter

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JeffG
Kent: Thank you! I am familiar w/ the concept of an eccentric (and no, I didn't think you meant Dutch--just kidding, Herb!). And Kent, your drawings were awesome, and I easily understand your reasoning, and agree w/ it, because of them, but now, after all that effort, please point me at the exact photo you could see that in. And understand, I have no doubt you'll do this, I just want to see if I can actually "see" what you "saw" in whatever pic you "saw" it in. You see?

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Kent
Peter, Deducing from the picture is pretty easy -- the Pittman arm bolts onto the pulley near the outside of the "circle" of the pulley. It forms a simple eccentric (see dictionary.com definition below). When the final drive pulley turns over one complete revolution, it has caused the pittman arm to move forward, then back to its original position, completing one stroke... While I have no experience with these little tractor-mounted ones, I've spent far too many days looking at the north end of a south-bound team of mules pulling the steel wheel-driven ones.... Kent ec·cen·tric Pronunciation Key (k-sntrk, k-) adj. Departing from a recognized, conventional, or established norm or pattern. See Synonyms at strange. Deviating from a circular form or path, as in an elliptical orbit. Not situated at or in the geometric center. Having the axis located elsewhere than at the geometric center. http://simpletractors.com/images/pittman.jpg

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Kent
Dan, It took one year of pre-engineering as an Aerospace Engineering major long ago for me to realize that I was NOT cut out to be an engineer. I enjoyed the drafting, geometry, and "arithmetic" (even vectors), but calculus was a huge struggle.... I have to be able to "visualize" the answer to understand the theory and potential application! Kent

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MPH
Kent--I was afraid you'd say that--LoL! I can't make hide nor hair out of Figure 4, other than it's general layout, but I'm gonna print it and go study my sicklebar. That diagram is so complex-looking to me, I think it triggered my "higher math reflex" (gag!). But thanks for telling me. Thanks again, Peter

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Kent
Peter, it's in Figure 4, that I linked in above... ----------------------------------- ADDED LATER ------------------------------------ How's this? Does it help? I don't know if the pulley drives from the top (my guess) or the bottom, but the effect on the pittman arms would be the same. Pittman #1 is the eccentric, converting circular movement to back and forth. There's a pivot in the middle, transferring this movement, and Pittman #2 looks like it drives the cutter bar.... http://simpletractors.com/images/pittman2.jpg

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Dutch
Peter, You seem to enjoy taking shots at me..... That's okay, you're not alone. I've developed a protective armor for my feelings. Besides, I realize many people have a tendency to mock that which they do not understand.

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